Absorption is the incorporation of a substance in one state into another of a different state (e.g. liquids being absorbed by a solid or gases being absorbed by a liquid).
Absorption Chiller
Absorption chillers are refrigerators that use heat energy as an input, rather than mechanical energy. Absorption chillers are useful, where electricity is no available or where there is an easily available source of heat (e.g. sun, hot water). The heat is used to evaporate a liquid to a gas. The gas then moves to the condenser where the heat dissipates and the gas is turned back into a liquid. Then, the cooled liquid is directed into the evaporator, where it turns into a gas and pulls heat from the air. Then the gas moves from the evaporator into the compressor and the process starts again. Synonyms: Absorption Refrigerator

Accumulation System
An accumulation tank or a continuously fed batch is characterised by an increasing effective reactor volume with time. When the reactor is full and reaction time is over, it is emptied and refilled again as batch reactors. Synonyms: AC, Accumulation Tank, Fed Batch Reactor
Acetogenesis is the third step of anaerobic digestion. Products from fermentation (organic acids, alcohols) are converted into hydrogen (H2), carbon dioxide (CO2) and acetic acid (CH3COOH). To produce acetic acid, acetogenic bacteria need oxygen and carbon. For this, they use the oxygen solved in the solution or bound-oxygen. Hereby, the acid-producing bacteria create an anaerobic condition, which is essential for the methane-producing microorganisms responsible for the further step of anaerobic digestion which is methanogenesis.

Acidic is an adjective describing the properties of having a pH below 7. Its opposite is alkaline or basic.

Activated Sludge
Activated sludge consists of flocs of bacteria, which are suspended and mixed with wastewater in an aerated tank. The bacteria use the organic pollutants contained in the wastewater to grow and transform it to energy, water, CO2 and new cell material, thereby removing them from the water. Activated sludge systems are suspended-growth type and are used in conventional high-tech wastewater treatment plants. Almost every wastewater can be treated in activated sludge systems as long as it is biodegradable. A physical pre-treatment unit, a post-settling unit (a clarifier) from which active sludge is re-circulated to the aerated tank, as well as excess sludge treatment, are necessary. The process is highly mechanised and thus only adapted for centralised systems where energy, mechanical spare parts and skilled labour are available. Provided the reactor is well operated, a very good removal of organics and suspended solids can be achieved, though pathogen removal is low.
Abbreviation: AS

Adult Learning
Learning opportunities for adults exist in a variety of settings, ranging from a formal institution to day to day practical learning at work. It is important to acknowledge prior knowledge and experiences of learners, including their ability to recognize their own skills as lifelong learners. Considerations for adult development and learning include biological and psychological development and socio cultural and integrative perspectives on development.
Advanced Facultative Pond
Advanced facultative ponds are the first step in advanced integrated wastewater pond (AIWP) systems. They consist of a conventional facultative pond, containing a digestion pit on its bottom, where solids are trapped and transformed into methane by anaerobic digestion. The surface aerobic layer is about 1 meter deep and helps reducing potential odour problems. Biogas may be collected using a submerged gas canopy and potentially used for energy production. Synonyms: AFP
Abbreviation: AFP

Advanced Integrated Wastewater Pond
Advanced integrated wastewater pond systems are improved conventional waste stabilisation pond (WSP) systems and are based on a series of four advanced ponds: An advanced facultative pond (AFP) containing a digester pit which functions much like an anaerobic pond integrated into the facultative pond; A high rate pond (HRP), covered by algae which provide oxygen to the water and take up organics and nutrients; An algal settling pond (ASP), where most of the algae produced in the HRP is removed; And finally an maturation pond (MP) for biological and solar disinfection. Synonyms: Advanced Integrated Pond, AIP, AIWP
Abbreviation: AIWP

Advanced Oxidation Process
The term advanced oxidation processes (AOP), describes a series of processes which are used for the chemical treatment of organic and inorganic pollutants in wastewaters. AOPs are based on the generation of reactive oxygen species (ROS) such as hydroxyl radicals. Generating hydroxyl radicals is possible via various ways such as photocatalytic, electrochemical, sonochemical. Typical AOPs are H2O2/hv, ozone/hv, ozone/H2O2/hv, TiO2/hv, (photo-)Fenton systems and electrochemical processes. Synonyms: AOP
Abbreviation: AOP

Advanced Wastewater Treatments
Advanced wastewater treatments, in opposition to natural systems require generally highly engineered biological processes, which leads to a reduction in space requirement to achieve similar performances. However, due to the complexity of the process and the high requirements for energy and operation and maintenance, advanced systems inhere a higher risk of technical failure.

Advection Fog
Advection fog is a certain type of fog, that requires a steady wind that moves a fog layer that has formed upwind of a given site.
Fog Research
Advisory Services in Environmental Management
Advisory Services in Environmental Management Synonyms: ASEM
Abbreviation: ASEM

Advocacy is the action of delivering an argument to gain commitment from political and social leaders and to prepare a society for a particular issue (DE JONG 2003). Advocacy involves the selection and organisation of information to create a convincing argument, and its delivery through various interpersonal and media channels (e.g. public speaking, project visits, petitions, engaging celebrities, radio and newspaper). Influencing and involving important leaders is one of the essentials of advocacy, because political support together with support from community leaders and religious leaders can give a water-related project or campaign a powerful boost (SCHAAP & VAN STEENBERGEN 2001). Synonyms: Influencing Leaders
Aerated Pond
Aerated ponds are aerobic wastewater treatment ponds in which the natural oxygenation is enhanced by mechanical or diffused air injection to achieve high rates of organic degradation and nutrient removal. Completely mixed aerated ponds require a sedimentation unit afterwards and are in essence activated sludge systems without sludge return. Synonyms: Aerated Lagoon

Aerobic means ‘requiring oxygen’. Aerobic processes can only function in the presence of molecular oxygen (O2), and aerobic organisms are those that use oxygen to drive cellular respiration and store energy.

Aerobic Digestion
Aerobic digestion describes the microbial transformation of organic matter into water, heat and CO2 in presence of oxygen. Aerobic digestion is used in wastewater treatment to both organic matter and the volume of sludge. As for anaerobic digestion, process rates increases with increasing temperature. Aerobic sludge digestion facilities may be designed for batch or continuous flow operations and the process results in approximately 50% reduction in solids content for typical municipal wastewaters. Typical wastewater treatments, using aerobic digestion are activated sludge systems, trickling filters, aerobic ponds etc.

Aerobic Wastewater Treatment
Aerobic wastewater treatments use aerobic microorganisms to transform pollution into a variety of oxidized end products, carbon dioxide, and metabolized biomass. Generally, aerobic wastewater treatment is faster than anaerobic treatments but require the supply of oxygen, which can be expensive, and energy consuming.

Aeroponics is the process of growing plants in an air or mist environment without the use of soil or an aggregate medium. The word "aeroponic" is derived from the Greek meanings of "aero" (air) and "ponos" (labour). Unlike hydroponics, which uses water as a growing medium and essential minerals to sustain plant growth, aeroponics is conducted without a growing medium. Aeroponic equipment involves the use of sprayers, misters, foggers, or other devices to create a fine mist of water to deliver nutrients to plant roots. Because water is used in aeroponics to transmit nutrients, it is sometimes considered a type of hydroponics.
Anaerobic microorganisms, which are not sensitive to oxygen and can growth both in its absence and in its presence.

African Development Bank
African Development Bank Synonyms: AfDB
Abbreviation: AfDB

African Development Fund
African Development Fund Synonyms: ADF
Abbreviation: ADF

African Ministers Conference On Water
African Ministers Conference On Water Synonyms: AMCOW
Abbreviation: AMCOW

African Union
African Union Synonyms: AU
Abbreviation: AU

Agenda 21
The first UN Conference on Environment and Development in 1992 adopted an agenda for environment and development in the 21st Century. This “Agenda 21: A Programme of Action for Sustainable Development” reaffirmed that sustainable development was delimited by the integration of the economic, social and environmental pillars. The “Agenda 21” is not legally binding, a reason to be criticised by many.
Aggregation formation
Soil particles can stick together and build aggregates where water can be enclosed.

Agricultural Issues
Agricultural issues provides background knowledge that is necessary to understand loop-oriented approaches in the management of water and wastewater - such as soil properties, plant requirements, etc.

Agricultural Wastewater
Agricultural wastewater is all waters that have been used in agriculture and are refused. They are either biodegradable (most often) and can be treated and reused similar to blackwater (e.g. manure from livestock); or they are not biodegradable (e.g. water containing a lot of residues from pesticides etc.) and require an advanced oxidation processes for treatment.

Air Stripping
Air stripping is the transferring of volatile components of a liquid into an air stream. It is a chemical engineering technology used for the purification of groundwater and wastewater containing volatile compounds. Synonyms: Stripping
Air Stripping
Algae Settling Pond
Algae Settling Pond follow the high rate algae pond in a advanced integrated pond systems. They are designed to settle out algae, and especially important if the water from the high rate algae pond is to be used for crop irrigation. The hydraulic retention time in algae settling ponds are of about two days and the harvested algae can be used as a nitrogen-rich fertilizer, or as protein-rich animal or fish feed (for further cultivation of high protein foodstuffs), modern medicine and even cosmetics for the idle. Synonyms: ASP
Abbreviation: ASP

Algal Bloom
A rapid increase in the population of algae in an aquatic system, e.g. as a result of an excess of nutrients (particularly phosphorus and nitrogen). As more algae and plants grow, others die. This dead organic matter becomes food for bacteria that decompose it. With more food available, the bacteria increase in number and use up the dissolved oxygen in the water. When the dissolved oxygen content decreases, many fish and aquatic insects cannot survive. Synonyms: Marine Bloom, Water Bloom
Algal Bloom
Alkaline is an adjective describing the properties of having a pH greater than 7. It is the opposite of acidic.

The alkalinity measures the capacity of water to neutralise acids. The alkalinity depends on amount of carbonates, bicarbonates, hydroxides, and occasionally borates, silicates and phosphates. Alkalinity stabilises water at pH levels around 7 (neutral). However, high water acidity decreases alkalinity and may cause harmful conditions for aquatic life. Alkalinity is expressed in ppm or mg of calcium carbonate per litre (mg/L CaCO3).
Alluvial River
An alluvial river is a river in which the bed and banks are made up of mobile sediment and/or soil. Alluvial rivers are self-formed, meaning that their channels are shaped by the magnitude and frequency of the floods that they experience, and the ability of these floods to erode, deposit, and transport sediment. As such, alluvial rivers can assume a number of forms based on the properties of their banks; the flows they experience; the local riparian ecology, and the amount, size, and type of sediment that they carry. These forms can be meandering, braiding, wandering and (occasionally) straight.
Colourless astringent compound that is a hydrated double sulphate of aluminium and potassium, used in water purification. Synonyms: AlK(SO4)
Abbreviation: AlK(SO4)

See ammonium. Synonyms: NH3
Abbreviation: NH3

Ammonia nitrogen (NH4-N) is found in aqueous solutions as ammonium ion (NH4+) or ammonia gas (NH3), depending on the pH and the temperature of the solution. It is a bioavailable form of the macronutrient nitrogen and found in many fertilisers. It is also the result of the decomposition of organic nitrogen in wastewaters. At high pH, NH3 is predominant. NH3 is volatile, colourless and has a pungent odour. If it escapes to the atmosphere, it can travel large distances and resettle with the rain, what can lead to overfertilisation (eutrophication) and acidification of ecosystem. Synonyms: NH4+
Abbreviation: NH4+
Wastewater Engineering, Treatment and Reuse
Anaerobic means completely deficient in oxygen and describes environments where there is no molecular gaseous oxygen (O2), neither any other form of oxygen available for metabolic activity. Anaerobic microorganisms use other molecules than oxygen for the respiratory activity. Anaerobic processes are either hindered, or halted by the presence of oxygen. Anaerobic processes are often more foul-smelling than aerobic processes.

Anaerobic Ammonium Oxidation
ANAMMOX stands for Anaerobic Ammonium Oxidation. It is quite a new process, which combines ammonia and nitrite into dinitrogen gas directly instead of passing through a two stage process of aerobic nitrification and anaerobic denitrification. Compared to conventional nitrification/denitrification in activated sludge systems, ANAMMOX eliminates the necessity of an organic carbon source for nitrification, reduces energy demand for aeration and has a smaller production of excess sludge and lower CO2 emissions. Synonyms: ANAMMOX
Anaerobic Baffled Reactor
An anaerobic baffled reactor is an improved septic tank, which, after a primary settling chamber, uses a series of baffles to force the grey-, black- or the industrial wastewater to flow under and over the baffles as it passes from the inlet to the outlet. The wastewater is introduced into the chamber at the bottom, leading to an enhanced contact with the active biomass which results in an increased retention and anaerobic degradation of suspended and dissolved organic pollutants. ABRs are robust and can treat a wide range of wastewater, but both remaining sludge and effluents still need further treatment in order to be reused or discharged properly. Synonyms: ABR
Anaerobic Biogas Digester
Anaerobic digesters are air-tight chambers used to transform organic wastes (excreta, faecal sludge, wastewater, organic fraction of municipal waste, garden or kitchen waste, etc.) or feedstock (energy crops such as maize, palm oil, etc.) into biogas by a process called anaerobic digestion. Typical anaerobic biogas digesters used for slurries are round a work in a fed-batch process. They can be small-scale (e.g. agricultural biogas plants) or large-scale (high-tech industrialised plant). Other reactor types used for biogas sanitation are biogas settlers, upflow anaerobic sludge blanket (UASB) reactors, anaerobic baffled reactors (ABRs) and anaerobic filters.

Anaerobic Biogas Settler
Anaerobic biogas settlers are air-tight reactors used for the pre-settlement of municipal wastewaters and the conversion of the settled sludge into biogas via anaerobic digestion. Biogas is recovered and can be transformed into heat, light or any other energy. The reactors are round or square - much like a septic tank, but with biogas collection. As the wastewater flows into the tank, organic solids start to settle to the ground. The liquid phase continuous to further treatment steps after a relatively short hydraulic retention time, while the sludge is kept in the tank for several months to years (long sludge retention time). The remaining slurry is almost pathogen free and can be used as soil amendment (optionally after an aerobic composting post-treatment or drying/humification in a sludge drying bed). Biogas settlers are most often used at community or institutional level as first treatment step of a decentralized wastewater treatment systems (DEWATS) for the pre-treatment of biodegradable domestic or industrial wastewaters. Synonyms: Biogas Settler

Anaerobic Digestion
Anaerobic digestion is the degradation of organic material by microbial activity in the absence of air transforming it into biomass and biogas, a mixture of methane (CH4), carbon dioxide (CO2) and some trace gases. Biogas is recovered and can be transformed into heat, light or any other energy. The process takes place in four steps (hydrolysis; fermentation and acidification; acetogenesis, and methanogenesis). Anaerobic digestion of typical wastewater or faecal sludge results in a sludge reduction of approximately 95% (compared to aerobic treatments which achieve only 50%). Process rate increases with increasing temperature. Typical wastewater treatment systems using anaerobic digestion are small- and large-scale anaerobic digestion, anaerobic baffled reactors (ABR), upflow anaerobic sludge blanket reactors (UASB), etc.

Anaerobic Filter
An anaerobic filter is a fixed-bed biological reactor. Anaerobic filters are similar to septic tank, with the difference, that wastewater, once entered into the tank must flow downwards (anaerobic downflow filter, ADF) or upwards through a filter media (anaerobic upflow filter, AUF). Dissolved organic matter and un-settleable solids are filtered and anaerobically digested by bacteria of the biofilm attached to the filter media. Anaerobic filters are widely used as secondary treatment in household-level black- or greywater systems or in decentralised wastewater treatment systems (DEWATS). Compared to septic tanks or anaerobic baffled reactors, they considerably improve the solid removal. As it is an anaerobic digestion process, which removes organic matter, biogas can be recovered and used. Synonyms: AF

Anaerobic Pond
Anaerobic ponds are deep (3 to 5 m) small ponds, which receive black- and greywater for anaerobic treatment. Suspended solids settle to the ground and the sludge, which builds up in the bottom, where it is transformed into biogas via anaerobic digestion. If the pond is covered, biogas can be collected for use. Anaerobic ponds are most often used as a primary treatment in waste stabilisation pond (WSP) systems. Synonyms: AP
Abbreviation: AP

Anaerobic Wastewater Treatment Process
Anaerobic Wastewater Treatment processes are based on the treatment of waste and wastewater by a process called anaerobic digestion. During anaerobic digestion, the organic matter in the waste and wastewaters is transformed to biogas, a mix of methane (CH4) and carbon dioxide (CO2) and a nutrient rich sludge. Biogas can be transformed into heat or power and has therefore a large potential as a renewable energy source. The nutrient-rich sludge can be composted and used as fertilising soil amendment in agriculture. Typical biogas sanitation technologies are biogas settlers, upflow anaerobic sludge blanket (UASB) reactors, anaerobic baffled reactors (ABRs) and anaerobic filters for municipal wastewaters; and biogas reactors (batch, fed-batch PFR or CSTR) for the treatment of slurries and solid organic wastes from agriculture and industry.

Anal Cleansing Water
Anal cleansing water is the liquid which has been used to clean oneself after is (and/or urinating). In comparison to blackwater, it is only little polluted and can be treated onsite by infiltration and fertigation (e.g. in mulch).
Anammox Bacteria
The causative organism, which was responsible for the Anammox reaction was named Candidatus Brocadia anammoxidans. This organism is a member of the planctomycetes and therefore lacks peptidoglycan in its cell wall, divides by budding, and has a compartmentalised cytoplasm. Candidatus Brocadia anammoxidans is able to anaerobically oxidise ammonium and nitrite to nitrogen gas. The key enzyme involved in this reaction, hydroxylamine oxidoreductase, is located in an organelle-like structure called an anammoxosome. The ability to oxidise ammonium anaerobically makes Candidatus Brocadia anammoxidans potentially useful for reducing, or eliminating, ammonium from wastewater. Synonyms: Candidatus Brocadia anammoxidans
Anoxic describes environments where there is no molecular gaseous oxygen (O2), but other forms of oxygen can still be present (in opposite to anaerobic, which means that there is no oxygen at all). Organisms that can live in an anoxic environment can use oxygen that is bound in other molecules (e.g. nitrate, sulphate). Anoxic conditions are often found at the interface between aerobic and anaerobic environments (e.g. in trickling filters or in facultative ponds).

To protect the immediate surroundings of a well, a concrete slab is installed around the water extraction point. Synonyms: Well cover

Aqua Privy
The aqua privy is a simplified variation of the septic tank. It is a simple storage and settling tank immediately under the latrine floor. Excreta drop directly into the tank through a pipe. Te bottom of the pipe is submerged in the liquid in the tank, forming a water seal to prevent escape of flies, mosquitoes and smell. Effluent usually infiltrates into the ground through a soak pit. Accumulated solids (sludge) must be removed frequently and enough water must be added to compensate for evaporation and leakage losses (in order to maintain the water seal).

Aquaculture is commonly defined as the active cultivation (maintenance or production) of marine and freshwater aquatic organisms (plants and animals) under controlled conditions. This definition encompasses a broad range of operations, cultivating a wide variety of organisms such as fish, crustaceans and aquatic plants, using a wide variety of production systems and facilities. Aquaculture can be combined with the reuse of wastewater. Nutrients contained in wastewater are removed by feeding animals or plants, which can be harvested. Pathogens can also be removed by natural die-off, solar disinfection (in shallow ponds) or predation (even though the effluent is not pathogenically safe). The combination of aquaculture and wastewater reuse allows optimising the water use for farming of aquatic animals and plants for food production all by increasing the quality of the wastewater effluent.

Aquaponics is the symbiotic cultivation of plants and aquatic animals in a recirculating environment. Aquaponic comes from the two words aquaculture and hydroponic. The main aim of such systems is the recycling of the nutrients contained in the water from aquatic animal effluent. The system contain of to interlinked compartement, one for growing plants and one for growing aquatic animals. The plants take up the nutrients, allowing them to grow and reducing or eliminating the water's toxicity for the aquatic animal. Thus the water can be recirculated back to the animal pond where it will be charged again by nutrients.

Arid climate is characterised by high evaporation and low precipitation. This climate is typical for desert or semi-desert as well as big continental areas surrounded by mountains.
Pentavalent Arsenic Synonyms: As(V)
Abbreviation: As(V)

Trivalent Arsenic Synonyms: As(III)
Abbreviation: As(III)

Artesian Spring
Artesian springs occur when water is trapped between impervious layers and is forced to the surface under pressure. At these springs, the water comes out of the ground vertically.
Spring Catchment
Artificial Fertiliser
Artificial fertilisers are plant nutrients produced through chemical processes to nurture soil and foster plant growth. Artificial fertilisers mainly consist of plant macronutrients such as Nitrogen, Potassium, Phosphorus and Sulphur, but lack other essential substances (micronutrients). Artificial fertiliser are able to improve the chemical properties of soils, but as they contain no organic substances, they are not able to counter the loss of organic substance through harvesting, which is important for soil structure. On the other hand, organic fertilisers produced out of biodegradable waste – such as e.g. kitchen residues, manure and other organic waste – are complete fertilisers that are able to improve both physical and chemical properties of the soil, and that are normally more balanced in their composition, containing macro- and micronutrients.

Artificial Groundwater Recharge
Artificial recharge is the planned, man-made increase of groundwater levels. By improving its natural replenishment capacities and percolation from surface waters into aquifers, the amount of groundwater available for abstraction is increased. Treated effluent and/or stormwater is discharged into aquifers either directly or after pre-treatment (e.g. wastewater stabilisation ponds or constructed wetlands). This is particularly useful in areas where water and groundwater resources are heavily utilised and acute problems with dropping watersheds, soil salinisation, saltwater intrusion in coastal areas or water scarcity in general exist. Synonyms: Groundwater Recharge

Automated irrigation
An automated irrigation system refers to the operation of the system with no or just a minimum of manual intervention. Almost every irrigation system can be automated with the help of timers, sensors, computers, or mechanical appliances.

Automatic Surge Flow and Gravitational Tank Irrigation System
This is an intermittent gravity-flow irrigation system consisting of a storage tank equipped with one or more siphons. The water in the tank flows to the field because of the siphon effect. As soon as the tank is empty, the flow stops. For the next irrigation process, the tank has to be filled-up to restart the siphon effect again. To learn more about possible siphon designs see VORTECH (2009).
Awareness Raising
With Awareness Raising Tools, you try to influence social norms, attitudes and values of people so they will change their behaviour because they are convinced that they are doing the right thing and their actions are in line with their personal values. Different types of information, education and communication (IEC) instruments can be used to initiate behavioural change and to stimulate social pressure towards sound and sustainable policies.

Awareness Raising for Demand Creation
Awareness raising includes an array of different technologies to make people aware of a problem, a new approach, a solution etc.