3.3.1. Principal Component Analysis (PCA)

The sample quantity is crucial for good PCA. The PCA of the study was performed considering the chemical constituents of 90 PM2.5 samples. The outliers (those beyond 2SD) were removed, and the dataset was normalized prior to the operation [69]. When the value of KMO is close to 1, it indicates that there is a strong correlation between these variables (KMO indicates the amount of variance shared among the items designed to measure a latent variable when compared to that shared with the error), and these variables are more suitable for PCA [70]. In this study, the SPSS software package (IBM, version 24.0) was used to conduct PCA research on substances in PM2.5 to obtain the emission characteristics

of its pollution sources. For this study, the species of Li, Na, K, Mn, Cu, Zn, As, Pb, Al, Mg, Ca, Fe, Ba, Si, Ti, NH4 +, NO3 −, SO4 2−, OC and EC had strong correlations in the two seasons, and the PCA results are listed in Table 2.

**Table 2.** Matrix of loading factors of PCA in spring and autumn.

From Table 2, we know that PCA resolved six components explaining 80.5% of the variance in spring.

**Factor 1**: The first factor contributes 18.15% to the total factor contributions and is characterized by a high concentration of SIAs, which indicates that Wenshan was greatly affected by secondary inorganic aerosol pollution in spring. SIAs are mainly generated by the photochemical reactions of precursor gases (SO2, NH3, and NOx), which are emitted from specific identified sources of human activity (coal combustion, vehicle exhaust emission, and biomass burning). Therefore, the strict control of precursor gases is conducive to reducing PM2.5 levels.

**Factor 2**: The second factor contributed 16.28% of the total PM2.5, and mostly originated from natural sources, such as the lifting of dust or mechanical abrasion processes, which was identified by high concentrations of Al, Fe, Si and Ti, indicating the leading contribution of dust [71]. Si and Ti are the key tracers of soil dust caused by winds. The extra Ba is emitted from brake linings and tire tread wear. These results can be explained as a consequence of dust persisting in the atmosphere longer because of calm and low-speed winds.

**Factor 3**: The third factor resolved 14.15%, and represents the factor contribution from industrial emissions. The elements are related to the industrial metal smelting process and represent anthropogenic emissions from various industries near the sampling site [72].

**Factor 4**: This source provided 11.55% of PM2.5. OC and EC are considered to be tracers of motor vehicle emissions, and EC is an indicator of primary emissions of OC [73]. The presence of K also deserved our attention, directly indicating emissions from biomass burning.

**Factor 5**: Cu and Na were apportioned to this factor, which suggests that the effect of this factor was manifold, such as copper smelting and sea salt [74]. The contribution of this factor towards PM2.5 was 10.83%, as revealed by PCA. In addition, Na might travel long distances from the Indian Ocean, and Cu could have come from the nearby industrial area in Honghe Prefecture.

**Factor 6**: This factor is construction cement dust, which is represented by high concentrations of Ca and Mg [75]. This finding indicates that construction and demolition activities were prevalent in the urban areas in Wenshan during the sampling period, without effective measures for dust control. More precise and effective policies are needed for the local government to improve PM2.5 pollution.

In addition, PCA resolved five components explaining 78.7% of the variance in autumn. Different from spring, Factor 1 represent biomass burning and industry sources, contributing 29.40% of PM2.5. Factor 2 includes secondary inorganic aerosols and motor vehicle exhaust emissions, which resolved 18.73% of the factor contribution. Factor 3 represents metal smelting, with remarkable representative Al, Fe and Mg features, which can be attributed to the smelting production activities around the site. Factor 4 and Factor 5 are soil dust and construction dust, which resolved 9.30% and 8.91% of the factor contributions, respectively.

#### 3.3.2. The Long-Range Transport

To better understand the transport of airborne particles from distant sources, the 72 h backward trajectories starting at a height of 100 m at the sampling site were calculated using the Hybrid Single Particle Lagrangian Integrated Trajectory 4.0 (HYSPLIT4) model with a 12 h period (meteorological data from the Global Data Assimilation System (GDAS)). The back trajectories were classified into three clusters using TrajStat in this study.

In spring, the trajectories were grouped into three clusters (Figure 6). Cluster 1 (blue line), from the southwestern direction, was associated with slower and lower air mass trajectories and accounted for 57%. The other two trajectory clusters (green line and red line) came from the north and southwestern directions, accounting for 24% and 19%, respectively. Cluster 1 came from central Myanmar and passed through during spring sampling in northern Vietnam and the Honghe Prefecture in Yunnan Province, China, which explains the effect of Factor 3. At the same time, Cluster 2 (green line) came from the industrial region in Chongqing, which explained the source of biomass burning in Factor 1 and the industrial impact in Factor 3. Figure 6b shows that wind mainly originated from the south during the sampling period, which prevented the diffusion and great accumulation of NOX and SO2. Then, they formed secondary pollution through photochemical reaction transformation, which conforms to the SIA pollution in Factor 1. The higher wind speeds were also consistent with the contribution of Factor 2.

In autumn, the trajectories were grouped into three clusters from the southeastern direction (Figure 7). Cluster 1 (red line) came from Guangxi Province and passed through the industrial region in Baise, which explains the presence of industrial elements in Factor 1. The other two trajectory clusters (blue line and green line) accounted for 33% and 8%, respectively. Figure 7b also shows that the wind mainly originated from the south during the sampling period and resulted in the impossibility of the diffusion and dilution of pollutants, which was also the reason for the SIA pollution in Factor 2.

**Figure 6.** (**a**) Mean 72 h backward trajectories of each trajectory cluster during spring and the percentage of allocation to each cluster. (**b**) Wind roses of Wenshan during spring sampling.

**Figure 7.** (**a**) The mean 72 h backward trajectories of each trajectory cluster during autumn and the percentage of allocation to each cluster. (**b**) Wind roses of Wenshan during autumn sampling.

### **4. Conclusions**

In this study, PM2.5 samples were collected in Wenshan, and their mass concentration, chemical composition and source apportionment characteristics were analyzed in spring and autumn. The mean concentrations of PM2.5 were 48.00 ± 11.01 μg/m3 and 41.64 ± 10.10 μg/m3 in spring (sampled on 19 April–3 May) and autumn (sampled on 12 October–26 October). The annual mean concentration of PM2.5 at the three sites was 44.85 ± 10.99 μg/m3, which was lower than that in Standard II (75.00 μg/m3) and higher

than that in Standard II (35.00 μg/m3). This means that the air quality in Wenshan is better than that in most cities in China.

WSIIs and OC were the main components of PM2.5, accounting for 26.91% and 23.80% of PM2.5, respectively. SIAs were the major contributors to WSIIs, due to the incomplete combustion of fossil fuels and the slathering of nitrogen fertilizers in agriculture. Wenshan was greatly affected by secondary inorganic aerosol pollution in the two seasons, which contributed 21.82% and 16.50% to the total factor contributions in spring and autumn, respectively. The ratio of NO3 −/SO4 2− implied that the contribution of mobile sources was not significantly different from that of other developed areas. The daily mean value of OC/EC was 2.64–4.17 in spring and 2.74–3.65 in autumn, which indicates that the SOC was generated by the photochemical process during the sampling days in Wenshan. Moreover, the OC and EC concentrations in Wenshan had a better correlation in autumn (R = 0.86) than in spring (R = 0.69), which shows that OC and EC were derived from similar sources during autumn and from complex sources during spring. However, elements from anthropogenic sources (Ti, Si, Ca, Fe, Al, K, Mg, Na, Sb, Zn, P, Pb, Mn, As and Cu) accounted for 99.38% and 99.24% of the total inorganic element concentration in spring and autumn, respectively.

Source apportionment showed that SIAs (18.15%), the lifting of dust or mechanical abrasion processes (16.28%), industrial sources (14.15%), motor vehicle emissions (11.55%), copper smelting and sea salt pathways (10.83%), and construction cement dust emissions (9.58%) were the main pollution sources in PM2.5 in spring. Furthermore, source apportionment showed that biomass burning and industry (29.40%), SIAs and motor vehicle exhaust (18.73%), metal smelting (12.33%), soil dust (9.30%) and construction dust (8.91%) emissions were the main pollution sources of PM2.5 in autumn. Different source contributions were found in spring and autumn. According to the research results, the pollution prevention and control suggestions are as follows: (1) Exert related effective management for artificial sources, such as industry and construction sites, to accelerate industrial transformation and upgrading. (2) Adopt emission control measures, such as motor vehicle restrictions and the promotion of new energy transportation methods.

The results of cluster analysis indicate that the long-range transport of air pollutants has a profound effect on local air quality in Wenshan. Wenshan is mainly affected by long-distance atmospheric transmission from the southwest and the northeast in spring and autumn, respectively.

In this paper, chemical composition and source characteristics of PM2.5 in a plateau slope city were first studied, and the main sources of PM2.5 in Wenshan City are resolved. The results can provide scientific data to support PM2.5 pollution control in local and similar cities.

**Author Contributions:** Conceptualization, J.S. and X.H.; investigation, Y.Z. and L.R.; resources, X.H.; data curation, Y.F.; writing—original draft preparation, X.L.; writing—review and editing, J.S. and X.H.; supervision, P.N. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Key R&D Projects of China (grant number 2019YFC0214405) and the National Natural Science Foundation of China (grant number 21966016 and 21667014).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data used in this paper can be provided by Jianwu Shi (Shijianwu@kust.edu.cn).

**Acknowledgments:** This work was supported by the National Key R&D Projects of China (No. 2019YFC0214405), and the National Natural Science Foundation of China (No. 21966016, 21667014).

**Conflicts of Interest:** The authors declare that there are no competing financial interests that could inappropriately influence the contents of this manuscript.


**Author details**

Edlyne Eze Anugwom Department of Sociology and Anthropology, University of Nigeria, Nsukka, Nigeria

\*Address all correspondence to<EMAIL_ADDRESS>
© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**65**

*Health Promotion and Its Challenges to Public Health Delivery System in Africa*

Promoting Health: Politics and Practice.

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*Health Promotion and Its Challenges to Public Health Delivery System in Africa DOI: http://dx.doi.org/10.5772/intechopen.91859*


**5. Conclusions**

The total element contents and the bioavailable fraction of essential elements Ca, Mg, Zn, Mn, and Fe were determined in leaves of *Sempervivum tectorum* L. The control of the quality of medicinal plants used in traditional medicine and pharmacy is an important step for consumer protection from contamination and health risks. The determination of toxic element content in plants grown on different soils clearly shows the contamination of plants from urban soils and plants fertilized with phosphate fertilizers. The high bioavailable concentrations of essential elements could explain the wide use of this plant in folk medicine. For example, the high Mg content in fresh juice is responsible for its anti-inflammatory action and application as an ear pain reliever.

**Author Contributions:** K.N. constructed and conceived the project. G.G. and I.K. designed the study. P.R., S.M., Y.S. and I.Y. performed the study. V.A. and Y.S. analyzed the data. G.G. and I.K. wrote the newspaper. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Bulgarian Ministry of Education and Science under the National Research Programme "Healthy Foods for a Strong Bio-Economy and Quality of Life" approved by DCM # 577/17.08.2018.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Datasets from the time of this study are available from the respective author upon reasonable request.

**Acknowledgments:** Special thanks to Medical University–Varna for the provided financial support for paper publication.

**Conflicts of Interest:** The authors declare no conflict of interest.


*Edited by Lavinia Cosmina Ardelean*

*and Laura Cristina Rusu*

Oral health care is an issue of modern society that is sometimes difficult to manage. Considered a key indicator of global health, well-being, and quality of life, oral health's relationship with general health is of utmost importance. As such, maintenance of oral health should be a lifelong commitment as well as a daily priority. This book includes twenty chapters that focus on different aspects of oral health issues, including prevention, treatment, and management.

*Sergio Alexandre Gehrke, Dentistry Series Editor*

ISBN 978-1-80355-123-4

Oral Health Care - An Important Issue of the Modern Society

ISSN 2631-6218

Published in London, UK © 2022 IntechOpen © Gile68 / iStock

IntechOpen Series Dentistry, Volume 10


**5. Impacts of conventional tillage on soil health**

Since the origins of agriculture, tillage has been used to prepare seedbeds, control weeds, and incorporate amendments. However, conventional intensive tillage using frequent disturbance through implements like moldboard plowing and heavy disking can seriously impair soil health over time. Tillage breaks up soil structure, disrupts biological communities, and exposes soil organic matter to decomposition, resulting in a cascade of physical, chemical, and biological degradations.

#### **5.1 Physical impacts**

One of the most prominent physical impacts of intensive tillage is increased soil compaction and degradation of soil structure [2, 14]. Frequent tractor passes and inversion by moldboard plowing form plow pans and destroys soil aggregation, reducing macroporosity for drainage, aeration, and root growth [7, 15]. With poor structure, tillage also leaves soil much more vulnerable to compaction and wheel traffic effects [16]. Loss of stable aggregation from organic binding agents and disruption of soil biology impair soils' ability to regain structure [10].

In addition, conventional tillage leaves soil nearly bare between crops, dramatically increasing susceptibility to erosion from wind and rainfall. Intensive tillage

pulverizes surface aggregates and residues that protect soil from raindrop impact and overland flow [17]. Erosion removes fertile topsoil and organic matter, reduces infiltration, and causes further structural decline. Tillage also speeds evaporation of soil moisture, requiring more frequent passes for seedbed preparation that perpetuates compaction issues.

Formation of surface crusts is another common physical impact in conventionally tilled soils. Destruction of surface aggregates combined with loss of protection from residues and minimal biological activity near the surface often causes crusting and poor seedling emergence [7]. Hard crusts reduce infiltration and increase runoff and erosion. Emerging seedlings can be cut off or plants may expend crucial energy breaking through crusted layers.

Overall, intensive conventional tillage degrades the fundamental physical properties needed for soil functionality. The resulting problems with compaction, structure loss, erosion risks, and crusting diminish root growth, drainage, and plant establishment which are critical for agricultural productivity and soil sustainability.

#### **5.2 Chemical impacts**

Tillage also substantially alters key chemical properties and processes in soil systems. Most notably, conventional intensive tillage generally causes significant declines in soil organic matter and overall carbon stocks [3, 11]. Frequent inversion and disturbance expose previously protected organic matter to microbial decomposition and release CO2 into the atmosphere [17]. Reduced carbon inputs from less residue return also deplete organic matter over time. Lower organic matter negatively impacts structure, reduces nutrient and water-holding capacities, and decreases soil biology.

Nutrient balances and availability dynamics are also disrupted by conventional tillage regimes. Native soil nutrient reserves become depleted over years of crop removal without adequate replenishment from organic cycling or additions of fertilizers and amendments [1]. Nutrients like nitrogen and phosphorus can be rapidly lost through leaching and gas emissions when bound up in soil organic matter that is decomposed through tillage exposure. Soluble nutrients are also readily lost when tillage causes erosion. More intensive fertilizer inputs are thus needed to maintain crop nutrition in degraded tilled soils. However, fertilizer use efficiency is often impaired by poor soil structure and biological activity as well.

Improper pH levels resulting from conventional tillage may further impact soil chemical processes and crop growth. Acidification is common, stemming largely from greater nitrate leaching when ammonium fertilizers are rapidly converted to nitrate, and reduced liming due to minimal surface residue incorporation [18]. Lower pH substantially influences nutrient availability, solubility of heavy metals and aluminum, and microbial communities (**Table 1**).

#### **5.3 Biological impacts**

Soil biology represents a foundational component of overall soil health that is significantly altered by frequent conventional tillage [19]. The extensive physical disturbance and changing soil environmental conditions under intensive tillage regimes reduce soil biological diversity, activity, and community resilience [20]. Fungal communities are particularly affected due to their sensitivity to disturbance, while bacteria increase in dominance [21].

#### **Table 1.**

*Comprehensive analysis of the impacts of conventional tillage on soil health.*

Biomass, abundance, and diversity of soil fauna including protozoa, nematodes, earthworms, and arthropods generally decline with tillage intensity, which removes surface residues and kills organisms directly through mechanical disruption [22, 23]. Declines in mycorrhizal associations further impact plant and root ecology. Reduced soil macrofauna and fungal activity negatively affect soil structure development and stabilization. Lower organic matter under tillage also cuts off the energy source driving soil food web integrity and function.

Overall biological activity including nutrient mineralization and immobilization, carbon transformations, and pest suppression suffers under intensive tillage regimes [24]. For example, earthworms and arbuscular mycorrhizal fungi play key roles in soil carbon storage; their reduction with tillage decreases soil carbon sequestration [10, 25]. Impaired biology diminishes critical services like nutrient cycling, water regulation, and disease suppression.

In essence, conventional tillage degrades soil biological function at many levels, from microbial communities and soil fauna diversity to critical services that support agricultural productivity and ecological health. Regenerating soil biology requires a systemic approach including reduced tillage, increased plant diversity, and enhanced organic matter inputs.


Structural Consolidation of Architectural Heritage

*Carlos Franco*

#### **Abstract**

The present study has as its main objective, the search and development for a model of evaluation and diagnosis of the origins of pathologies, in a rehabilitation process of architectural heritage that allows possible corrective measures to be applied at an early stage of appreciation, defining rigorously the reinforcement and consolidation options necessary to improve the overall construction performance. Understanding the original tectonics of the building, becomes essential for a conscious and adequate performance decision-making in an intervention that is desirable to be minimal and not intrusive, facilitating the optimization of solutions depending on the state of conservation in which the building is. Historical and morphological characteristics of the construction were considered, in order to define and study the best solutions for an appropriate intervention. The proposal for structural stabilization, from the perspective of greater sustainability, observes all the requirements and recommendations of the international charters on heritage rehabilitation - in addition to national legislation, the contemporary intervention principles, guaranteeing the safeguarding of its identity.

**Keywords:** Architectural heritage, rehabilitation, original tectonics, construction pathologies, structural stabilization

#### **1. Introduction**

Taking advantage of a case study that was once carried out on a building in the entire state of neglect, for its research and its unequivocal architectural value, with a view to transmitting the scientific and technological knowledge and consequent endogenization then acquired, all the information collected was compiled. to the date and before the intervention in the meantime, including photographic records already in the initial phase of the work.

The work presented here aims to establish an intervention methodology - in an approach directed to the evaluation of the structural system, defining as a priority the global stabilization of the building.

The prior assessment of the building's state of conservation, through the onsite observation of pathologies and anomalies caused by years of neglect, makes it possible to define an appropriate concept for structural stabilization, which may be replicated in similar buildings, not only in Portugal as well as in any part of the world where there are examples of recognized architectural interest, favoring the adoption of less intrusive solutions, betting on the recovery and rehabilitation of materials and traditional construction techniques that are part of the set of cultural values materialized in the building, where adaptation to the new regulatory

requirements for use and structural performance, constitutes an additional challenge to which it is intended to respond, in order to satisfy the requirements of comfort, functional efficiency and sustainability.

Prior to interventions in classified Architectural Heritage and in the design phase, not only the applicable national legislation should be considered, but also the letters and recommendations, criteria and international standards on the protection of Architectural Heritage.

The studies and projects for the works of conservation, modification, reintegration and restoration in classified properties, or in the process of being classified, will have to be elaborated and subscribed by technicians of legally recognized qualification or under their direct responsibility, for which the works or interventions, will be subject to authorization and monitoring by the competent authorities for the final decision of the classification procedure.

Portuguese legislation establishes the bases of the policy and regime for the protection and enhancement of cultural heritage - Law n° 107/2001 of 8 September, in conjunction with Decree-Law n° 308/2009 of 23 October, defining the concepts, rights and duties of the owners of heritage with relevant cultural interest, namely architectural, with values of memory, antiquity, authenticity, originality, rarity, uniqueness or exemplarity, being a fundamental task of the State and duty of citizens, their protection and enhancement [1].


*5.3. Plant and Herb Derived Antioxidants*

Numerous plant- or herbal extracts or plant/herb-derived natural products have been tested for their capacity in fighting DKD. A major representative of these extracts is polyphenols that can scavenge ROS [177], leading to correction of redox imbalance and enhancement of mitochondrial function [178–180]. Moreover, these plants extracts can also activate the Nrf2 signaling pathway thereby leading to upregulation of the so-called second cellular defense system including antioxidant proteins such as heme oxygenase-1 and NQO1 [181]. As chronic inflammation is implicated in the pathogenesis of DKD, many studies involving plant extracts have also demonstrated their anti-inflammation properties in preclinical DKD [182]. Table 1 shows selected representatives of plant/herb extracts or plant/herb-derived compounds and their redox balanced-related anti-DKD mechanisms.

**Table 1.** Selected representatives of plant/herbal extracts/components in DKD from the literature. Experimental models and the major underlying renoprotective mechanisms are also given in the table.

 Please note that this table is not meant to exhaust the literature on plant/herbal extracts and DKD.

### *5.4. Caloric Restriction*

Caloric restriction (CR) [221–223], sometimes also called energy restriction [224,225], is a well-established approach for extending the lifespan of many species. CR can also prolong the health span of many organs including the kidney [226–229]. As CR has a direct impact on energy supply that involves NADH and NAD+, it thus is involved in eliciting antioxidative responses in DKD by restoring redox balance and mitigating diabetic kidney injury [230,231]. Such responses include AMPK activation, autophagy, ROS elimination, Nrf2 signaling pathway activation and enhancement of antioxidative capacity in the kidney [231–235]. In certain studies, exercise has been shown to have a synergistic effect on CR [236,237]. Therefore, CR and exercise may be applied simultaneously to enhance kidney function in diabetes [238,239]. Moreover, intermittent fasting, a different version of CR, has also been demonstrated to prevent progression of DKD via NAD+ dependent sirtuin pathway [230]. Additionally, the restriction of single element in a given diet such as iron can also afford renoprotection in diabetes via attenuation of oxidative stress [240].

#### **6. Magnitude of Redox Imbalance and Progression of DKD**

While it is now known that NADH/NAD+ redox imbalance is one of the underlying mechanisms of DKD and this redox imbalance drives reductive stress to oxidative stress [47], culminating in renal dysfunction in DKD, whether the magnitude of NADH/NAD+ redox imbalance can be associated with the indices of DKD progression has not been established. DKD progression can be determined by the ratio of urinary albumin to urinary creatinine [127] and by estimated glomerular flow rate (eGFR) [241,242], but whether NADH/NAD+ ratio would also advance from low to high during DKD progression is unknown at this time and needs to be investigated. It is conceivable that with the progression of DKD quantitated by the above-mentioned parameters, values of the NADH/NAD+ ratio would also increase gradually to reflect the severity of DKD. Conversely, the value of the NADH/NAD+ ratio should go down upon remission of DKD after treatment. Regardless, this would need to be evaluated using proper animal models that can show clearly an association of the value of NADH/NAD+ to progression of DKD until the end stage of renal disease.

#### **7. Conclusions**

NADH/NAD+ redox imbalance, driven by persistent hyperglycemia and oversupply of other nutrients, is the initiator of reductive stress and oxidative stress in DKD [47]. More studies would be needed to dissect the role of each and every player in this cascade of redox imbalance biochemistry mechanism. Complete and comprehensive studies not only will shed insights into the mechanisms of DKD but will also facilitate identification of targets that can be explored for DKD therapy. As indicated in a recent review article by Matoba et al. [243], targeting NADH/NAD+ redox imbalance would be a valuable approach for combating DKD. Finally, it should be pointed out that in terms of potential injury caused by redox imbalance, which part of the kidney or what type of cells that sustain the most damage have not been comprehensively evaluated. Therefore, future efforts should be made to assess redox imbalance-induced damage to endothelial cells of the renal vasculature, the podocytes and mesangial cells of the glomerulus and the epithelial cells of the tubule. Additionally, how redox imbalance differs within the tubule should also be measured.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** The author's work was supported in part by UNTHSC seed grants RI10015 and RI10039.

**Conflicts of Interest:** The authors declare no conflict of interest.


*Article* **Removal of Phenol from Aqueous Solution Using Internal Microelectrolysis with Fe-Cu: Optimization and Application on Real Coking Wastewater**

**Do Tra Huong 1,\*, Nguyen Van Tu 2, Duong Thi Tu Anh 1, Nguyen Anh Tien 3, Tran Thi Kim Ngan 4,5 and Lam Van Tan 5,6,\***

**Citation:** Huong, D.T.; Van Tu, N.; Anh, D.T.T.; Tien, N.A.; Ngan, T.T.K.; Van Tan, L. Removal of Phenol from Aqueous Solution Using Internal Microelectrolysis with Fe-Cu: Optimization and Application on Real Coking Wastewater. *Processes* **2021**, *9*, 720. https://doi.org/ 10.3390/pr9040720

Academic Editors: Bipro R. Dhar and Andrea Petrella

Received: 6 March 2021 Accepted: 16 April 2021 Published: 19 April 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

**Abstract:** Fe-Cu materials were synthesized using the chemical plating method from Fe powder and CuSO4 5% solution and then characterized for surface morphology, composition and structure by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The as-synthesized Fe-Cu material was used for removal of phenol from aqueous solution by internal microelectrolysis. The internal electrolysis-induced phenol decomposition was then studied with respect to various parameters such as pH, time, Fe-Cu material weight, phenol concentration and shaking speed. The optimal phenol decomposition (92.7%) was achieved under the conditions of (1) a pH value of phenol solution of 3, (2) 12 h of shaking at the speed of 200 rpm, (3) Fe-Cu material weight of 10 g/L, (4) initial phenol concentration of 100.98 mg/L and (5) at room temperature (25 ± 0.5 ◦C). The degradation of phenol using Fe-Cu materials obeyed the second-order apparent kinetics equation with a reaction rate constant of k of 0.009 h−1L mg−1. The optimal process was then tested against real coking wastewater samples, resulting in treated wastewater with favorable water indicators. Current findings justify the use of Fe-Cu materials in practical internal electrolysis processes.

**Keywords:** internal microelectrolysis; Fe-Cu material; phenol; wastewater treatment; coking wastewater

### **1. Introduction**

In recent years, the process of industrialization and modernization in Vietnam has taken place rapidly, promoting socio-economic development of the country and accompanying problems of environmental pollution. Phenol is a hazardous pollutant and is listed as one of 129 pollutants that need to be pre-treated, according to US Environmental Protection guidelines. Phenol is often generated in the waste streams of industries such as petrochemicals, oil refining, plastics, steel, textile, paper and pulp, pesticides, pharmaceuticals, synthetic resins, and coking plants [1–3]. Phenol is a less biodegradable chemical that can cause cancer, gene mutation and teratogen. Phenol contaminates water sources, causing tremendous harm to humans and organisms; thus, eradication of phenol pollution in wastewater is being studied in many countries, including Vietnam. In order to treat phenols, physicochemical methods, such as adsorption, flocculation and sedimentation have been used as a traditional treatment. However, they are found to be not very effective.

Internal electrolysis (IE) has been proposed as a remedy for this issue. Usually, based on the electron material used, there are four types of IE, including Fe-Cu, Fe-C, Al-Cu and Al-C. Among them, the Fe-C and Fe-Cu systems are widely used in actual projects. The principle of IE involves two materials with different electrode potentials that generate microelectrode pairs when being in contact. For Fe-C, the Fe-Cu iron system acts as an anode and copper or carbon acts as a cathode, similar to the micro-battery pair in metal corrosion. With a micro-battery with a voltage of about 1.2 V, a small power circuit of μA appears, which acts as a redox agent in the decomposition reaction of adsorbed organic compounds on the electrode surface. Due to this principle, Fe-C and Fe-Cu electrolytic processes are also known as internal microelectrolysis. Therefore, it is possible to dissolve iron without the use of an external current by placing micro-battery pairs as composites of Fe-C and Fe-Cu, providing an advantage in internal microelectrolysis technology in wastewater pretreatment applications [1–26]. The reactions that occur during internal microelectrolysis are as follows [27].

The reaction at the anode (Fe):

$$\text{Fe} \rightarrow \text{Fe}^{2+} + 2\text{e} \to ^{0}(\text{Fe}^{2+}/\text{Fe}) = -0.44 \text{ V} \tag{1}$$

The reaction at the cathode (Cu):

$$2\text{H}^+ + 2\text{e} \rightarrow 2[\text{H}] = \text{H}\_2\text{ E}^0 (\text{H}^+ / \text{H}\_2) = 0.00\text{ V} \tag{2}$$

$$\text{Fe and Cu:}\ \mathrm{H\_2O} \to \mathrm{HO^\*} + \mathrm{H^+} + \mathrm{e} \tag{3}$$

Organic substances that exist in the solution, such as RX (organochlorine compound) and RNO2 (aromatic ring nitro compound) then receive electrons from the anode surface (metal Fe) and are reduced by the chlorine and amine reaction. The resulting pollutants would become non-toxic or less toxic products, hence being more easily biodegradable.

The internal microelectrolysis process holds two main advantages. First, it could be applied to treat various types of industrial wastewater, including polyester-containing effluent [15], dyes [11,13,16], discharge from coal gasification [12], plant protection products [3,25], nitrate contamination [19], mixed industry (textile, dyeing, paper, plating, mechanic) [6–9], high organic matter [4,17,18], oil contamination [14], TNT and RDX contamination [10]. Second, internal microelectrolysis exhibits high treatment efficiency, fast response time and low operating costs. Fan and Ma [4] used a Fe-Cu electrode system to treat mixed industrial wastewater in Taopu, Shanghai at the capacity of 60,000 m3/day, achieving a COD removal efficiency of 40%. Yin et al. [12] used this method to connect an external current to treat 4-chlorophenol, reaching a removal efficiency that was higher than 90% after 36 min. Yang et al. [5] also reported that internal electrolysis could be used to treat polyester wastewater, achieving the COD removal efficiency of 58%. The COD of the wastewater decreased from 3353.2 mg/L to 1391.6 mg/L and its BOD5/COD ratio also increased from 0.27 to 0.42 after treatment. Zhu [17] combined internal microelectrolysis and a bio-membrane to treat mixed industry wastewater, reducing the COD from 150,000 mg/L to 500 mg/L.

Recent trends in enhancing the decomposition of organic pollutants have shifted to the use of bimetallic internal microelectrolytic materials prepared by the deposition of second transition metals on the iron surface. Previous studies showed that transition metals such as Ni, Cu and Co can enhance the catalytic activity of FeO [28]. Two types of catalytic mechanisms of bimetallic internal electrolytic materials have been proposed: (a) indirect reduction by atomic hydrogen ([H] abs) absorbed on the material's surface in bimetallic and transition metal additives form that facilitates the generation of surface-linked hydrogen atoms ([H] abs), and (b) direct reduction on the catalytic active site by receiving electrons during FeO oxidation and surface additives (i.e., transition of metals) to increase FeO oxidation through the formation of a multitude of micro-battery pairs [29,30].

In many studies, Fe-Cu and Fe-C materials are usually made from scrap, iron granules, copper and carbon powder with different sizes or prepared by second transition metal

deposition on the surface of Fe, thus offering modest degradation efficiency against pollutants [5,28–31]. However, it has been suggested that the use of chemical plating of Cu on the Fe surface might result in materials with significantly improved degradation capacities for internal microelectrolysis [22]. For example, Xu et al. (2008) fabricated Fe-Cu material using the chemical plating method and used it in treatment of nitrobenzene (100 mg/L) in aqueous solution [31]. The obtained material showed a removal efficiency of approximately 95% at optimal conditions, suggesting a better reactivity of the chemically galvanized Fe-Cu for internal electrolysis. Bo et al. (2014) used a micro-sized Fe-Cu internal electrolyte material prepared by chemical plating to pretreat p-nitrophenol in aqueous solution [22]. The material was prepared with the content of Cu on the surface varying from 30% to 95%. Remarkably, the results pointed out that the Fe-Cu ratio played a key role in degradation of p-nitrophenol.

In this work, we continued this research pathway by fabricating Fe-Cu materials using the chemical plating method and investigated the effect of some factors such as pH, treatment time, mass of Fe-Cu system, shaking rate, and the concentration to efficiency ratio of phenol degradation of Fe-Cu materials in aqueous medium. In addition, the internal electrolysis reaction was applied to treat real coking wastewater from a coal factory in Vietnam.

#### **2. Materials and Methods**

#### *2.1. Fabrication of Cu-Fe Material*

Fe powder with sizes smaller than 50 μm and 99.9% purity (PA, China) was immersed in 30% NaOH solution for 10 min to remove grease and clean the surface. The surface was activated by treating in HCl 7.4% wt for 3 min. The diluted HCl solution was prepared with an HCl solution concentration of 37% wt. The material was then washed several times with water, followed by drying at 105 ◦C for 2 h, allowed to cool and stored in a sealed glass jar. Fe-Cu samples were made using the chemical plating method in 5% CuSO4 solution (wt%). To be specific, a total of 100 g of Fe powder was added into 1 L of 5 wt% CuSO4 solution for a period of 2 min. The mixture was then washed several times with water and dried at 105 ◦C for 3 h under N2 gas. The material was then stored in a desiccator for further research.

#### *2.2. Characterization of Structure, Composition, Physical Properties, Surface Characteristics of Fe-Cu Materials*

The surface characteristics and components of the Fe-Cu material after fabrication were determined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) (on an SEM-EDS machine, JSM 6610 LA—JEOL, Tokyo, Japan), respectively. Measurements were made at the Institute of Materials Chemistry, Institute of Military Science and Technology, Vietnam. The structure of the material was determined by the method of X-ray diffraction (XRD) (on a Bruker D5000, Siemens, München, Germany). The measurement was conducted at the department of Chemistry—Hanoi University of Natural Sciences.

#### *2.3. Study on Decomposition of Phenol*

Factors affecting degradation of phenol were investigated, including pH, time, dosage of Fe-Cu materials, shaking rate and initial concentration of phenol. The experiments were carried out at room temperatures (25 ± 0.5 ◦C). Parameters for the experiments are shown in Table 1.

**Table 1.** Parameters for single factor investigations.

All experiments were conducted three times to check the repeatability. The result of each experiment is the average result of the three times, with P values less than 0.05 indicating a significant difference between the means.

The phenol degradation efficiency was calculated by the formula:

$$\text{H\%} = \frac{(\text{C}\_0 - \text{C}\_{\text{cb}})}{\text{C}\_0} \times 100\text{\%} \tag{4}$$

In which: C0 is the concentration of the phenol solution before decomposition (mg/L), Ccb is the concentration of the phenol solution after decomposition (mg/L) and H is the degradation efficiency (%).

The initial and post-treatment phenolic concentrations were determined on the HPLC Waters Acquity Arc instrument at the University of Education, Thai Nguyen University, Thai Nguyen Province, Vietnam. The instrument was equipped with chromatographic column C18 Inertsil ODS (5 μm, 250 × 3 mm, GL Sciences Inc., Tokyo, Japan). The optimal conditions for the determination of phenol content are as follows: wavelength of 272 nm, ratio of phosphate buffer solution mixture (pH = 4) to acetonitrile solution (pH = 3) of 30:70 (*v*/*v*), flow rate of 1.0 mL/ min, column temperature of 30 ◦C. TSS, BOD5, COD, total N, total P and NH+ 4 -N indicators were determined at the Thai Nguyen Center for Natural Resources and Environment Monitoring.

#### **3. Results and Discussion**

#### *3.1. Survey Results on Surface Characteristics and Physical Properties of Fe-Cu Materials*

From the analysis results of the SEM-EDS images of the materials and synthetic materials shown in Figures 1–4, it was found that the surface composition of the synthetic materials was different from the original materials. The Fe powder particles were arranged overlapping each other in blocks, whereas the Fe and Cu powder particles in Fe-Cu material were distributed relatively evenly on the surface with sizes of less than 50 μm. This shows that there was an even distribution of Cu plating alternating Fe powder particles to form Fe-Cu micro-cell pairs. The results of analyzing the EDS spectrum of Fe and Fe-Cu materials shown in Figures 3 and 4 and Tables 2 and 3 show specifically the presence of the elements and their content in each sample.

**Figure 1.** SEM image of Fe material.

**Figure 2.** SEM image of Fe-Cu material.

**Figure 3.** The EDS spectrum of material Fe.

**Figure 4.** EDS spectrum of Fe-Cu material.

**Table 2.** Results of analyzing Fe sample elements.

**Table 3.** Results of analyzing Fe-Cu sample elements.

Analysis of the EDS of the Fe-Cu samples has shown Cu appearance, which proves successful copper plating. The reaction in the process of dissolving and chemically plating copper follows the processes below:

$$\text{Fe} \rightleftharpoons \text{Fe}^{2+} + 2\text{e}$$

$$\text{Fe}^{2+} \rightleftharpoons \text{Fe}^{3+} + \text{e} \text{ (There may be a part of } \text{Fe}^{2+} \text{ oxidized to } \text{Fe}^{3+}\text{)}$$

$$\text{Cu}^{2+} + 2\text{e} \rightleftharpoons \text{Cu}$$

On the other hand, the analysis of the structure of the synthesized Fe and Fe-Cu materials shown in Figure 5 shows that the components of the two spectra were distinctly different. The Fe accounted for 18.59% of the mass according to EDX. On the XRD pattern, the peaks assigned to Fe were quite weak, which suggests that Fe may be converted into other compounds such as Fe•Cu2O. However, this is not always the case because Fe might be present in the Fe-Cu materials in amorphous forms, which does not show up in XRD results. Therefore, further studies are needed to confirm the exact material composition.

**Figure 5.** XRD spectrums of Fe and Fe-Cu materials.

This proves that the Fe-Cu bimetal material has been successfully fabricated and that Cu has coated the Fe surface to form Fe-Cu micro-battery pairs.

#### *3.2. Decomposition of Phenol*

#### 3.2.1. Effect of pH

According to Equations (1) and (2), the pH value has a great influence on the reaction rate and the redox ability to create [H]. When the pH is lower, the amount of H+ provided for the reaction becomes adequate or excessive, therefore accelerating the internal electrolysis or the corrosion of the electrode system. A lower initial pH value is associated with a higher concentration of [H]. Furthermore, in the presence of O2, the cathode reduction of the internal electrolytic reaction can also occur in the following reaction:

$$\text{O}\_2 + 4\text{H}^+ + 4\text{e} \to 2\text{O}^\* + 4[\text{H}] \to 2\text{H}\_2\text{O}; \text{E}^0 \text{ (O}\_2/\text{H}\_2\text{O}) = 1.23\text{ V} \tag{5}$$

Thus, more H+ would produce more [H] and O\*, enhancing the ability to redox and reduce phenol and leading to a better phenol treatment efficiency. The initial pH value also affects the rate of corrosion reactions of Fe/Cu materials to form Fe2+, Fe3+, Fe (OH)2 and Fe(OH)3. In a more acidic environment than Fe2+, Fe3+ is easy to form, yet it is difficult to precipitate Fe(OH)2 and Fe(OH)3. Conversely, when the pH is high and in the presence of dissolved oxygen, Fe(OH)2 and Fe(OH)3 concentration could be increased gradually in response to reaction time. Iron hydroxides are also factors that indirectly remove the phenol part as well as the intermediate compounds of the treatment by adsorption, flocculation and precipitation.

The results shown in Figure 6 show that when the pH value increases from 4 to 9, the phenol decomposition efficiency decreases. This can be explained by three main phenol decomposition processes, including decomposition due to the impact of internal electrolyte materials, adsorption and coagulation with iron hydroxide. As the concentration of Fe (II) and Fe (III) ions exceeds 10−5 mol/L in the material, precipitates of Fe(OH)2 and Fe(OH)3 will appear at pH values higher than 3, which is favorable for the flocculation of Fe (II) and Fe (III). At high pH (pH > 3), the phenol decomposition process was hindered, and coagulation was accelerated. As a result, phenol decomposition efficiency was decreased. Therefore, a pH value of 3 gave the maximum phenol decomposition efficiency and was selected for further studies.

**Figure 6.** Effect of pH on the phenol removal performance of Fe-Cu material.

#### 3.2.2. Effect of Time

Variations of phenol removal with respect to reaction time are illustrated in Figure 7. The results show that when increasing the time from the 2 to 12 h, the phenol decomposition efficiency increased rapidly to a maximum value of 92.39%. Thereafter, over a period from 12 to 24 h, decomposition efficiency decreased slowly and then became almost stable.

**Figure 7.** The effect of time on the phenol removal performance of Fe-Cu material.

The current result is in line with that of a previous study [19], which used Fe-Cu to treat polyester wastewater. This can be explained as follows: when the time increases from 2 to 12 h, the ongoing occurrence of the interior microelectrolysis reactions accumulates ferrous and ferric hydroxides, thus promoting phenol degradation efficiency. However, increasing the time from 12 to 24 h also leads to increased precipitation of hydroxides on the Fe-Cu surface and impedes the electron transmission between Fe-Cu and wastewater, thereby neutralizing the Fe-Cu surface and terminating the internal electrolysis, so the phenol degradation efficiency is reduced [20]. Therefore, we chose 12 h as the optimal time for phenol decomposition of Fe-Cu materials.

#### 3.2.3. Effect of Dosage of Material

Removal efficiencies achieved at different dosages are shown in Figure 8. As the dosage of Fe-Cu material increased from 0.25 to 1.0 g, the phenol decomposition efficiency increased gradually. Increasing the dosage from 1.0 to 6.0 g seemed to impair the phenol degradation efficiency. In general, increasing the dosage of Fe-Cu resulted in a higher generation of microscopic galvanic cells, possibly leading to improved phenol removal efficiency. However, excessive amount of Fe-Cu in the solution might cause particle agglomeration, thus reducing the contacting area among Fe-Cu and wastewater. Moreover, the excess iron would react with H+ present in the solution, leading to weakened reaction from Fe-Cu [21]. The Fe-Cu utilization efficiency would decrease remarkably if its dosage were too high. Therefore, the material weight of 1.0 g or 10 g/L was selected as the optimal material weight to decompose the phenol of Fe-Cu material.

**Figure 8.** The effect of material dosage on phenol removal performance of Fe-Cu material.

#### 3.2.4. Effect of Shaking Speed

The effect of shaking speed on phenol decomposition efficiency is shown as in Figure 9. As the speed was accelerated, the phenol decomposition efficiency also improved. This can be explained as follows. The shaking speed increases the dissolved oxygen content into the solution and enhances the ability to diffuse pollutants to the surface in contact with the Fe-Cu electrode, as well as the rapid dispersion of the products treated at the electrode in the solution. However, in acidic environments with low pH, the dissolved oxygen content is lower than in alkaline media. The effect of dissolved oxygen content on phenol degradation efficiency can be explained by the following reasons:

When shaking speed increased from 100 to 150 rpm, the phenol decomposition speed increased rapidly from 180 to 200 rpm. This could be the reason why at this time the dissolved oxygen concentration in the solution was almost saturated. Therefore, we chose the shaking speed of 200 rpm to proceed to subsequent experiments.

**Figure 9.** The effect of shaking speed on the phenol removal efficiency of Fe-Cu material.

#### 3.2.5. Effect of Initial Phenol Concentration

Phenol removal efficiencies at different initial phenol concentrations are shown as in Figure 10. The results from Figure 10 show that the phenol decomposition efficiency increased proportionally when the concentration increased from 53.38 to 100.98 mg/L. Afterwards, in the concentration range from 146.69 to 250.76 mg/L, the phenol decomposition performance decreased. At a phenol concentration value of 100.98 mg/L, the degradation efficiency reached the maximum value of 92.7%, which indicates almost complete phenol decomposition. There was a sharp decrease in performance at higher concentrations of phenols (higher than 100.98 mg/L), possibly due to higher required amount of internal electrolytic material. At low phenol concentrations, a low concentration gradient would obstruct the mass transportation. Simultaneously, the short lifetime of HO\* is also a contributing factor to reduce the number of reactions with phenol. At higher phenol concentrations, it is more likely for phenol and HO\* to mutually react, which results in improved phenol removal efficiency. However, at very high phenol concentrations (146.69 mg/L), the phenol removal efficiency decreased to 72.71% due to limited formation of HO\* in the interior micro-electrolysis system Therefore, there should be further studies and surveys to handle phenol at high concentrations.

**Figure 10.** The effect of initial phenol concentration on the phenol removal capability of Fe-Cu material.

3.2.6. Decomposition Analysis Phenol Concentrations by HPLC

Figure 11 illustrates HPLC results of different phenol solutions (initial concentration of 100.98 mg/L) treated with different masses of Fe-Cu internal electrolysis material. It was indicated that phenol was completely decomposed when being treated with Fe-Cu material with the weight of 10 g/L, under 12 h of shaking at 200 rpm and at a pH value of 3.

**Figure 11.** Chromatographic lines of a phenol solution sample depend on the amount of Fe-Cu material. Red curve: chromatogram of an untreated phenol sample (100.98 mg/L). Blue curve: chromatogram of a phenol sample treated with the following conditions: initial phenol concentration of 100.98 mg/L, Fe-Cu material weight of 5 g/L, shaking time of 12 h, shaking speed of 200 rpm, at pH = 3. Black curve: chromatogram of a phenol sample treated with the following conditions: initial phenol concentration of 100.98 mg/L, Fe-Cu material weight of 10 g/L, shaking time of 12 h, shaking speed of 200 rpm, at pH = 3.

#### 3.2.7. Degradation Kinetics of Phenol Using Fe-Cu Material

The classical kinetics is that of the first-order and second-order chemical reaction kinetics. The equations are shown as follows:

$$\text{First-order kinetic model: } \ln \mathbf{C}\_{\mathbf{t}} = -\mathbf{k}\_{\mathbf{t}} \cdot \mathbf{t} + \mathbf{A}\_{\mathbf{t}} \tag{6}$$

Second-order kinetic model: 1/Ct = k2·t+A2 (7)

$$\text{Third-order kinetic model: } 1/\text{C}\_{\text{t}}^{2} = 2\mathbf{k}\_{3} \cdot \mathbf{t} + \mathbf{A}\_{3} \tag{8}$$

where: k1 and k2 are the first-order and second-order reaction rate constants, respectively; A1, A2 and A3 are constants. C0 is the initial concentration of the phenol solution before decomposition (mg/L), which is 100 mg/L.

Based on the investigations on the efficiency of phenol degradation over time, we surveyed the kinetics of phenol degradation according to the first-, second-, and third-order kinetic equations, as shown in Figures 12–14.

The results show that the degradation of phenol by internal microelectrolysis material of Fe-Cu seemed to follow the second-order apparent kinetics due to a higher linear regression coefficient (R2 = 0.9507) than those of other kinetics. The calculated reaction rate constant of k of the second-order model was 0.009 h−1Lmg−1.

**Figure 12.** Model of the first-order apparent kinetics.

**Figure 13.** Model of the second-order apparent kinetics.

**Figure 14.** Model of the third-order apparent kinetics.

#### 3.2.8. Real Sample Analysis

In this study, the optimal experimental parameters, including a Fe-Cu mass of 10 g/L, a shaking time of 12 h, a pH of and a shaking rate of 200 rpm, were adopted for pretreating real wastewater samples collected from a coal factory (Thai Nguyen Iron and Steel Joint Stock Company, Thai Nguyen Province, Vietnam). The results are shown in Figures 15 and 16 and Table 4.

**Figure 15.** Chromatograms of wastewater samples containing phenols before treatment using Fe-Cu internal microelectrolysis material.

**Figure 16.** Chromatograms of wastewater samples containing phenols after treatment using Fe-Cu internal microelectrolysis material.

**Table 4.** Parameters of coking wastewater before and after treatment using Fe-Cu materials.

The mechanism of phenol degradation in the interior micro-electrolysis has been presented previously [25], and it involved the conversion of decomposed phenol into a less toxic intermediate compound. To be specific, during the micro-electrolysis process, radicals and oxidants are produced and oxidize organic compounds. This causes the destruction of structures of benzene ring and chemical bonds on its side chain, transforming toxic compounds into biodegradable intermediates [20]. Simultaneously, microelectron currents in the galvanic cell reaction also cause electron transfer, which promotes the growth and biodegradation capacity of microorganisms and stimulates active metabolic enzymes [32]. Furthermore, the justification of interior microelectrolysis technology for biological treatment is corroborated by its high degradation efficiency of refractory compounds and the ability to improve wastewater biodegradability [33].

The results in Table 3 show that the highest treatment efficiency was observed in the phenol parameter (70.07%), followed by the NH4 +-N, BOD5 and COD. The remaining parameters exhibited lower removal efficiencies (<50%). Thus, further biological treatment methods are recommended in order to achieve steel industry wastewater standards [34].

#### **4. Conclusions**

A sample of Fe-Cu material for internal electrolysis was synthesized from Fe powder material by using the chemical plating method. The Cu content at the material surface reached 69.30% (by weight). The surface, structure and composition of the as-synthesized materials were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction diagram (XRD), respectively.

The internal electrolysis-induced phenol decomposition was then studied with respect to various parameters, including pH, time, Fe-Cu material weight, phenol concentration and shaking speed. The optimal phenol decomposition (92.7%) was achieved at the pH value of 3, the shaking time of 12 h, the shaking speed of 200 rpm, the weight of Fe-Cu material of 10 g/L, the initial phenol concentration of 100.98 mg/L and at room temperature (25 ± 0.5 ◦C). The degradation of phenol using Fe-Cu materials obeyed the second-order apparent kinetics equation with a reaction rate constant of k of 0.009 L × mg−1h−1. Further evaluation using real coking wastewater resulted in treated effluents with favorable water indicators, suggesting the suitability of Fe-Cu materials in practical processes to treat coking wastewater before biological treatment. Further studies should contemplate the evaluation of material stability through cyclic reactions.

**Author Contributions:** Investigation, D.T.H., N.V.T., D.T.T.A., N.A.T. and T.T.K.N.; supervision, L.V.T.; writing—original draft, D.T.H.; writing—review and editing, L.V.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was funded by the Ministry of Education and Training of Vietnam, under the project B2019-TNA-10.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Acknowledgments:** This work was completed with financial support from the Ministry of Education and Training of Vietnam, under the project B2019-TNA-10.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


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Section 2


**1. Introduction**

[84] Love AJ, Chapman SN, Matic S, Noris E, Lomonossoff GP, Taliansky M. In Planta Production of a Candidate Vaccine against Bovine Papillomavirus Type 1. Planta.

[85] Borzacchiello G, Roperto F, Nasir L, Campo MS. Human Papillomavirus Research: Do we Still Need Animal Models? International Journal of Cancer 2009;125 739-740.

[86] Campo MS. Vaccination against Papillomavirus in Cattle. Clinics in Dermatology

[87] Campo MS, Roden RB. Papillomavirus Prophylactic Vaccines: Established Successes,

[88] Gaukroger JM, Chandrachud LM, O'Neil BW, Grindlay GJ, Knowles G, Campo MS. Vaccination of Cattle with Bovine Papillomavirus Type 4 L2 Elicits the Production of Virus-neutralizing Antibodies. The Journal of General Virology 1996;77 1577-1583. [89] Embers ME, Budgeon LR, Pickel M, Christensen ND. Protective Immunity to Rabbit Oral and Cutaneous Papillomaviruses by Immunization with Short Peptides of L2,

New Approaches. Journal of Virology 2010;84 1214-1220.

the Minor Capsid Protein. Journal of Virology 2002;76 9798–9805.

2012. doi: 10.1007/s00425-012-1692-0.

136 Current Issues in Molecular Virology - Viral Genetics and Biotechnological Applications

1997;15 275–283.

Baculoviruses are enveloped viruses that infect insect larvae mainly from the order Lepidop‐ tera. Their genomes are circular double-stranded DNA molecules of about 80 to 180 kbp and are packed in rod-shaped nucleocapsids with a typical size of 40-50 nm in diameter and 200-400 nm in length.

Among the numerous baculoviruses, *Autographa californica* multiplenucleopolyhedrovirus (AcMNPV) is the most widely studied and used in biotechnology.

During its infection cycle it produces two phenotypes. Occlusion derived viruses (ODV) initiate the infection at the larvae midgut. After this primary infection, the viral progeny consists of budded viruses (BV) that carry on the systemic infection in larvae. These types of virions differ in their efficiencies of infection for different cell types; ODV infect midgut epithelial cells up to 10,000 fold more efficiently than BV. In contrast, BV are up to 1,000-fold more efficient at infecting cultured cells than ODV. As the viral propagation in cell culture is mediated by BV phenotype (Rohrmann, 2011), most of the knowledge regarding baculovirus infection cycle is based on studies performed in insect cells infected by BV (Figure 1).

Cell entry is mediated by a class III viral glycoprotein located at the virion surface, Gp64, which interacts with an unknown cell receptor (Backovic & Jardetzky, 2009). This interaction triggers clathrin-dependent endosomal internalization. This internalized vesicle becomes subsequent‐ ly acidified. This causes a conformational change in Gp64 that result in the fusion of the viral envelope with the endosome membrane. Thus the nucleocapsid is released in the cytoplasm and migrates to the nucleus. Once in the nucleus, DNA is uncoated and the transcriptional cascade begins (Figure 2).

© 2013 Pidre et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

AcMNPV genome encodes about 150 genes which are transcribed in a temporal fashion. Firstly, immediate early genes are transcribed by the host RNA-polymerase II. These genes generally encode for transcription factors, like Ie1, that aid the subsequent transcription of genes. After this early phase DNA replication occurs. Immediately after DNA replication there may be a transient period when proteins are not bound to the DNA and this might expose late promoters and facilitate their activation (Rohrmann, 2011). Baculoviruses also encode a novel RNA polymerase that transcribes late and very late genes and that recognizes the unique baculoviral promoter consensus sequence DTAAG. During the systemic infection nucleocap‐ sids are assembled in the virogenic stroma. The envelope proteins are synthesized, translated in association with the endoplasmic reticulum, glycosylated and transported to and incorpo‐ rated into the cytoplasmic membrane via the Golgi apparatus. Nucleocapsids destined to become BV exit the nucleus. They move to the cytoplasmic membrane at the site where envelope proteins (Gp64 and F protein) concentrate, and bud through obtaining their enve‐ lopes. Early in the systemic infection more BV are produced which spread the infection throughout the insect. Finally, late in infection, occluded virions are produced, and the cell

Baculovirus Display: A Novel Tool for Vaccination

http://dx.doi.org/10.5772/55572

139

There are many biotechnological uses for baculoviruses. One of the most widespread is their use as insecticide agents. There have been much work on the development of baculoviruses to control insects but the acceptance and use of viruses for insect control has been limited. This can be attributed to their slow speed of kill and their limited host range. At present many research groups are working with the aim of overcoming these limitations developing novel strategies such as baculovirus-mediated expression of toxic proteins for insects. Moreover, recombinant baculoviruses have been extensively used as expression vectors in insect cell cultures. A variety of technological improvements have eliminated the tedious procedures to isolate the recombinant viruses turning the baculovirus-based expression system in a safe, easy

Another application of baculovirus is their use as expression vectors for eukariotic proteins. Their ability to include quite large DNA extra fragments in their genomes and the possibility to use their very strong polihedryn promoter, which activates upon infection, make baculo‐ viruses a very useful tool in biotechnology for the production of recombinant proteins in insect

In addition, protein expression in larvae or cell culture is not the only application of baculo‐ viruses. In fact, baculoviruses are widely used in the development of strategies for displaying foreign peptides and proteins on the virus surface as well as mammalian cell transduction using different mammalian expression cassettes. Baculovirus display consists of the expression of proteins or peptides in the surface of a baculovirus. This is achieved by fusing the protein of interest with the major baculoviral envelope glycoprotein Gp64, resulting in the localization of the chimeric protein on the viral envelope and the plasmatic membraneof infected cells. The surface displaying of antigenic epitopes make baculoviruses efficient vaccine vehicles capable

The aim of this chapter will be to describe the biotechnological utilities of baculovirus display. Particularly, it will describe this technique for vaccination and gene delivery. It will discuss

dies releasing the occlusion bodies.

to use and scale up system. (Kost et al., 2005).

of mounting a strong specific immune response.

cells.

**Figure 1.** Structure of the budded virus.

**Figure 2. Baculovirus replication cycle.** Infection cycle initiates when a budded virus (BV) interacts with the cell membrane and is endocytosed. When the endocytic vesicle is acidified, GP64 fusion protein, located at the BV mem‐ brane, trigger the fusion of the plasma membrane and the BV envelope releasing the nucleocapsid in the cytoplasm. The nucleocapsid is then transported to the nuclus where it transcribes its genes, replicates its DNA in the virogenic stroma where new nucleocapsids are assembled. Nucleocapsids then egress from the nucleus, travel to the cytoplas‐ mic membrane and bud through aquiring an envelope containing the surface protein GP64.

AcMNPV genome encodes about 150 genes which are transcribed in a temporal fashion. Firstly, immediate early genes are transcribed by the host RNA-polymerase II. These genes generally encode for transcription factors, like Ie1, that aid the subsequent transcription of genes. After this early phase DNA replication occurs. Immediately after DNA replication there may be a transient period when proteins are not bound to the DNA and this might expose late promoters and facilitate their activation (Rohrmann, 2011). Baculoviruses also encode a novel RNA polymerase that transcribes late and very late genes and that recognizes the unique baculoviral promoter consensus sequence DTAAG. During the systemic infection nucleocap‐ sids are assembled in the virogenic stroma. The envelope proteins are synthesized, translated in association with the endoplasmic reticulum, glycosylated and transported to and incorpo‐ rated into the cytoplasmic membrane via the Golgi apparatus. Nucleocapsids destined to become BV exit the nucleus. They move to the cytoplasmic membrane at the site where envelope proteins (Gp64 and F protein) concentrate, and bud through obtaining their enve‐ lopes. Early in the systemic infection more BV are produced which spread the infection throughout the insect. Finally, late in infection, occluded virions are produced, and the cell dies releasing the occlusion bodies.

There are many biotechnological uses for baculoviruses. One of the most widespread is their use as insecticide agents. There have been much work on the development of baculoviruses to control insects but the acceptance and use of viruses for insect control has been limited. This can be attributed to their slow speed of kill and their limited host range. At present many research groups are working with the aim of overcoming these limitations developing novel strategies such as baculovirus-mediated expression of toxic proteins for insects. Moreover, recombinant baculoviruses have been extensively used as expression vectors in insect cell cultures. A variety of technological improvements have eliminated the tedious procedures to isolate the recombinant viruses turning the baculovirus-based expression system in a safe, easy to use and scale up system. (Kost et al., 2005).

Another application of baculovirus is their use as expression vectors for eukariotic proteins. Their ability to include quite large DNA extra fragments in their genomes and the possibility to use their very strong polihedryn promoter, which activates upon infection, make baculo‐ viruses a very useful tool in biotechnology for the production of recombinant proteins in insect cells.

In addition, protein expression in larvae or cell culture is not the only application of baculo‐ viruses. In fact, baculoviruses are widely used in the development of strategies for displaying foreign peptides and proteins on the virus surface as well as mammalian cell transduction using different mammalian expression cassettes. Baculovirus display consists of the expression of proteins or peptides in the surface of a baculovirus. This is achieved by fusing the protein of interest with the major baculoviral envelope glycoprotein Gp64, resulting in the localization of the chimeric protein on the viral envelope and the plasmatic membraneof infected cells. The surface displaying of antigenic epitopes make baculoviruses efficient vaccine vehicles capable of mounting a strong specific immune response.

**Figure 2. Baculovirus replication cycle.** Infection cycle initiates when a budded virus (BV) interacts with the cell membrane and is endocytosed. When the endocytic vesicle is acidified, GP64 fusion protein, located at the BV mem‐ brane, trigger the fusion of the plasma membrane and the BV envelope releasing the nucleocapsid in the cytoplasm. The nucleocapsid is then transported to the nuclus where it transcribes its genes, replicates its DNA in the virogenic stroma where new nucleocapsids are assembled. Nucleocapsids then egress from the nucleus, travel to the cytoplas‐

mic membrane and bud through aquiring an envelope containing the surface protein GP64.

**Figure 1.** Structure of the budded virus.

138 Current Issues in Molecular Virology - Viral Genetics and Biotechnological Applications

The aim of this chapter will be to describe the biotechnological utilities of baculovirus display. Particularly, it will describe this technique for vaccination and gene delivery. It will discuss the adjuvant effects of baculoviruses and the immunity response of recombinant viruses. Moreover, other applications of baculovirus display such as gene therapy and high throughput screening of antibodies and antigenic epitopes libraries will also be addressed.

aminoacids polypeptide with 15 cysteine residues. The resulting disulfide bonds participate

Baculovirus Display: A Novel Tool for Vaccination

http://dx.doi.org/10.5772/55572

141

As a member of the Class III fusion proteins, Gp64 is composed of five domains that result in a macromolecular structure very distinct from any reported class I or class II fusion protein. However, Gp64 conserves the typical characteristics of viral fusion proteins. It includes a fusion domain which mediates the fusion between the cell membrane and viral envelope; a transmembrane domain which anchors the protein in the lipidic bilayer and a multimerization domain that allows the protein to form trimmers. The detailed structure of AcMNPV Gp64 is shown in Figure 3 (Backovic & Jardetzky, 2009) Baculovirus gp64 also contains a seven residue C-terminal tail domain (CTD). Deletion of this domain does not significantly affect the ability to mediate fusion, but reduces the baculovirus titers to 50%. These data indicate that CTD is

**Figure 3. GP64 structure. a.** Trimmeric structure of baculovirus major surface glycoprotein Gp64 obtained using the Expasy tool *Make multimer.py* in www.expasy.org. **b.** Gp64 polypeptide scheme showing different functional domains

in the formation of the native structure.

involved in virus budding (Figure 3).

**a**.

**b**.

useful for antigen surface display.


**1. Introduction**

Shipping has a vital role in developing human society over the years, at which the shipping activities have linked the widely separated parts of the world through commercial relationships. In fact, the shipping industry is still developing from time to time with rapid industrial and digital economy growth. In Canada, the shipping industry has been established since 1840 and now undergone significant technological advances, where the size of ships that carry containers for international use continues to increase [1]. Even in Malaysia, the government has launched an initiative, namely, Malaysia Shipping Master Plan, that ensures the shipping industry is focused on developing itself and has a guide for future development. This initiative takes place from 2017 until 2022 with a "Revitalizing Shipping for a Stronger Economy" theme [2].

Generally, there are three main classifications for the global cargo shipping industry, which are:

Each of wet bulk, dry bulk, and liner shipping needs their specialized vessels, which are tankers, bulkers, and container ships, respectively [3].

on the surface of the water and is carried into the shoreline, causing life cycles of

Hence, many governments and international industries are working on the marine pollution issue, mainly originated from the shipping industry, such as the Marine Environmental Protection Committee (MEPC), the International Convention for the Prevention of Marine Pollution from Ships (MARPOL), and the Department of Environment (DOE), Malaysia. In order to solve the problem, oily wastewater separator is essential and needs to be installed and operated effectively to prevent the pollution as well as to ensure that the water discharged overboard

The lowest compartment of the vessels and directly above the keel is known as bilge, where water that drains off from various sources is captured. The water might be originated from rain, interior spillage, rough seas, or minor leakage in other main parts of the vessel. Depending on a few factors such as ship size, design of engine room, and components' age, the amount of accumulated bilge water onboard varies from one to another. In order to maintain the stability of the vessel and to avoid conditions that can cause hazard (such as vessel's propulsion systems and ancillary machinery damage and fire hazard) due to too much of bilge waste accumulation, it is crucial to remove the bilge water into a holding tank, periodically [9]. There are two options to manage the bilge water, which are whether installing bilge separator to treat it onboard or holding it in a tank on the vessel before discharging it to the shore's treatment facility. Somehow, treating it onboard has an advantage where a smaller volume of oily bilge water has to be stored in the vessel. Meanwhile, the treated wastewater can be removed according to the related regulations and

The composition of bilge water depends on the design and function of the ship. The wastewater is commonly comprised of water, oily fluids, cleaning fluids, lubricant, and grease as well as other wastes that originated from piping, engines, and other operational and mechanical sources in the vessel's machinery spaces [9] as well as urine and chemicals.  Sludge is formed from the continuous fuel purification to remove contaminants in order to enhance lowquality fuels as well as to avoid ship's engines and highly machined components

The regulation stipulated by the International Maritime Organization (IMO) highlighted on the oil content of the bilge water discharged to the sea. The International Convention for the Prevention of Pollution from Ships (MARPOL 73/78) has set the maximum limit of 15 mg/L for the oil content in the wastewater to be discharged to the sea. According to the US EPA (2008), passenger ships produce the highest amount of bilge water with huge difference as compared to the other types of ships. This is due to their more complex constructions and support for crowds of

Typically, the small volumes of treated bilge water are released above the water line and instantly diluted in the sea water. Hence, the obvious effects of oil spill is most likely not going to occur. However, a long-term effect might happen to the marine living organisms around the shipping lanes. The negative consequences that will take place may be due to the excessive concentration of biodegradable compounds, including oil, as well as continuous increment of nondegradable compound

the plant and the respiration of the animals be interfered [10].

*Oil–Water Separation Techniques for Bilge Water Treatment*

*DOI: http://dx.doi.org/10.5772/intechopen.91409*

is within legal limits.

standards.

from being damaged.

passengers [9].

**149**

concentration such as metals [11].

**2. Impact of bilge on marine pollution**

Firstly, for wet bulk shipping, approximately a quarter of the goods transported by sea is dominated by crude oil [4]. The oils are transported from its production point to the purchasers by the wet bulk shipping or known as tankers. Majority of the crude oil is moved from the most significant oil-producing region, which is the Middle East, to the dominant importers like the European Union, Japan and the United States of America. Other than that, North America imports oil from the Caribbean and West America meanwhile West and North Africa export their oils to Europe [4].

Next, the largest group out of these three classifications is dry bulk shipping, where more than 50% of all loaded goods are handled by the bulkers, while 30 and 16% are for tankers and containers, respectively [5]. There is a vast range of solid cargoes transported by containers. Generally, there are five primary crucial bulk goods, which are coal, grain, iron ore, bauxite, and phosphates, in which iron ore and coal are the two goods that are transported the most [4]. Meanwhile, chemical packages and steel products are the example of the shipped minor bulk goods [6]. The main routes for iron ore transportation are from Australia and Brazil to Japan as well as from Brazil to Western Europe. While for coal, which is commonly used as steam coal in power stations to generate electricity, the leading exporters are from South Africa, Australia, Colombia, the East and West Coast of the United States, as well as Indonesia. Moreover, Australia, South Africa, Colombia, and the East Coast of the United States export their coal to Western Europe, whereas Japan receives the coal from the West Coast of the United States, Australia, and South Africa [4].

Liner shipping, also known as container shipping, provides services by transporting goods in containers with scheduled sailings. The variety of goods transported by liner shipping are packed in a smaller unit. One of the contributors to the continuation and development of liner shipping is the increment of the digital economy. According to Ref. [7], companies that produce and process raw materials, commodities, and manufacturing goods are the previous world's fastest-growing and biggest corporations. However, currently, Internet-related service and technology-based manufacturers, such as Alibaba, Amazon, Apple, and Microsoft, have become the world's most valuable and most prominent companies, where ecommerce, online communication and cashless Business to Business (B2B) and Business to Consumer (B2C) transactions are practiced [7]. This development has contributed more to the growth of the shipping industry, where it is considered as a catalyst for economic development by facilitating world trade, due to the cheaper mode of transportation.

However, aside from on-the-ground activities such as lubricants, refineries, and petrochemical industries, it is undeniable that shipping activities have contributed to marine pollution, especially in this twentieth century where carriage of the cargoes by the ships is increasing. According to [8], millions of tons of oily wastes and waste oils are generated as the by-products of the ships, every year. One of the contributors to water pollution by the operating marine vessels is the discharging of oily bilge water. Typically for marine vessels, the oily wastes and waste oil that come from various sources accumulate in the bilge space, which is the lowest part of the vessel.

Routinely, the accumulated oily bilge water must be discharged out of the bilge spaces to maintain the stability of the vessel, hence eliminating the possibility of the ship to be in the conditions that can cause a hazard to it [9]. The wastes discharged can eventually cause water pollution, which leads to many negative impacts on the human, environment, and marine populations. Oily bilge water may poison marine organisms because it might cover plants and tiny animals when it floated

## *Oil–Water Separation Techniques for Bilge Water Treatment DOI: http://dx.doi.org/10.5772/intechopen.91409*

Each of wet bulk, dry bulk, and liner shipping needs their specialized vessels,

Next, the largest group out of these three classifications is dry bulk shipping, where more than 50% of all loaded goods are handled by the bulkers, while 30 and 16% are for tankers and containers, respectively [5]. There is a vast range of solid cargoes transported by containers. Generally, there are five primary crucial bulk goods, which are coal, grain, iron ore, bauxite, and phosphates, in which iron ore and coal are the two goods that are transported the most [4]. Meanwhile, chemical packages and steel products are the example of the shipped minor bulk goods [6]. The main routes for iron ore transportation are from Australia and Brazil to Japan as well as from Brazil to Western Europe. While for coal, which is commonly used as steam coal in power stations to generate electricity, the leading exporters are from South Africa, Australia, Colombia, the East and West Coast of the United States, as well as Indonesia. Moreover, Australia, South Africa, Colombia, and the East Coast of the United States export their coal to Western Europe, whereas Japan receives the coal from the West Coast of the United States, Australia, and South Africa [4]. Liner shipping, also known as container shipping, provides services by transporting goods in containers with scheduled sailings. The variety of goods transported by liner shipping are packed in a smaller unit. One of the contributors to the continuation and development of liner shipping is the increment of the digital economy. According to Ref. [7], companies that produce and process raw materials, commodities, and manufacturing goods are the previous world's fastest-growing and biggest corporations. However, currently, Internet-related service and

technology-based manufacturers, such as Alibaba, Amazon, Apple, and Microsoft, have become the world's most valuable and most prominent companies, where ecommerce, online communication and cashless Business to Business (B2B) and Business to Consumer (B2C) transactions are practiced [7]. This development has contributed more to the growth of the shipping industry, where it is considered as a catalyst for economic development by facilitating world trade, due to the cheaper

However, aside from on-the-ground activities such as lubricants, refineries, and petrochemical industries, it is undeniable that shipping activities have contributed to marine pollution, especially in this twentieth century where carriage of the cargoes by the ships is increasing. According to [8], millions of tons of oily wastes and waste oils are generated as the by-products of the ships, every year. One of the contributors to water pollution by the operating marine vessels is the discharging of oily bilge water. Typically for marine vessels, the oily wastes and waste oil that come from various sources accumulate in the bilge space, which is the lowest part of

Routinely, the accumulated oily bilge water must be discharged out of the bilge spaces to maintain the stability of the vessel, hence eliminating the possibility of the ship to be in the conditions that can cause a hazard to it [9]. The wastes discharged can eventually cause water pollution, which leads to many negative impacts on the human, environment, and marine populations. Oily bilge water may poison marine organisms because it might cover plants and tiny animals when it floated

Firstly, for wet bulk shipping, approximately a quarter of the goods transported by sea is dominated by crude oil [4]. The oils are transported from its production point to the purchasers by the wet bulk shipping or known as tankers. Majority of the crude oil is moved from the most significant oil-producing region, which is the Middle East, to the dominant importers like the European Union, Japan and the United States of America. Other than that, North America imports oil from the Caribbean and West America meanwhile West and North Africa export their oils to

which are tankers, bulkers, and container ships, respectively [3].

Europe [4].

*Resources of Water*

mode of transportation.

the vessel.

**148**

on the surface of the water and is carried into the shoreline, causing life cycles of the plant and the respiration of the animals be interfered [10].

Hence, many governments and international industries are working on the marine pollution issue, mainly originated from the shipping industry, such as the Marine Environmental Protection Committee (MEPC), the International Convention for the Prevention of Marine Pollution from Ships (MARPOL), and the Department of Environment (DOE), Malaysia. In order to solve the problem, oily wastewater separator is essential and needs to be installed and operated effectively to prevent the pollution as well as to ensure that the water discharged overboard is within legal limits.

The lowest compartment of the vessels and directly above the keel is known as bilge, where water that drains off from various sources is captured. The water might be originated from rain, interior spillage, rough seas, or minor leakage in other main parts of the vessel. Depending on a few factors such as ship size, design of engine room, and components' age, the amount of accumulated bilge water onboard varies from one to another. In order to maintain the stability of the vessel and to avoid conditions that can cause hazard (such as vessel's propulsion systems and ancillary machinery damage and fire hazard) due to too much of bilge waste accumulation, it is crucial to remove the bilge water into a holding tank, periodically [9]. There are two options to manage the bilge water, which are whether installing bilge separator to treat it onboard or holding it in a tank on the vessel before discharging it to the shore's treatment facility. Somehow, treating it onboard has an advantage where a smaller volume of oily bilge water has to be stored in the vessel. Meanwhile, the treated wastewater can be removed according to the related regulations and standards.

The composition of bilge water depends on the design and function of the ship. The wastewater is commonly comprised of water, oily fluids, cleaning fluids, lubricant, and grease as well as other wastes that originated from piping, engines, and other operational and mechanical sources in the vessel's machinery spaces [9] as well as urine and chemicals.  Sludge is formed from the continuous fuel purification to remove contaminants in order to enhance lowquality fuels as well as to avoid ship's engines and highly machined components from being damaged.