dry sewage sludge). drainage water must be captured; drying beds are sometimes covered but usually left uncovered. drying beds are typically composed of four layers (from top to bottom): sludge, sand, fine gravel, coarse gravel and drainage pipes. fecal sludges behave differently during dewatering processes than wastewater sludges. the amount of extracellular polymeric substances (eps) can be an important predictor for fecal sludge dewatering performance. fecal sludge from public toilets took longer to dewater than sludge from other sources, and had turbid supernatant after settling. grasses with adventitious roots may also be planted in drying beds, allowing for reduction of odor, collection over longer periods, production of forage, and more decomposition of the final biosolids by the time they are extracted. the roots introduce oxygen and maintain the permeability of the sludge. earthworms may also play an important role in such beds. emerging technologies emerging technologies for fecal sludge treatment include: technologies that can produce a dried or carbonized solid fuel from fecal sludge include: drying, pelletizing, hydrothermal carbonization, and slow pyrolysis. thermal processes which can achieve cost effectiveness by eliminating the need for separate processes. they convert the fecal sludge along with certain fractions of sewage sludge or municipal solid waste to produce energy or fuel by using certain sewage sludge treatment technologies. biodiesel can be manufactured by using fats, oils and grease as feedstocks. research by rti international is being conducted to use fecal sludge for biodiesel production. electricity can be produced by thermal processes that burn fecal and solid waste together to maintain stable combustion and the heat is used to make steam that drives generators. solar thermal dryers solar thermal dryers rely on the collection of the solar thermal energy for drying and pasteurization of fecal sludge. in these systems, the sludge is placed inside an enclosure of transparent or opaque walls, with a ventilation system for moisture evacuation. the sludge can be dried by hot air that was heated by a solar thermal collector (indirect solar dryer), by direct exposure to solar radiation (direct solar dryer), or by both modes (mixed solar dryer). co-treatment at wastewater treatment plants co-treatment of septage at wastewater treatment plants may be considered where the volume of septage removed from on-site facilities is small, as will be the case in situations where most households have access to sewerage. however, the high strength of septage and fecal sludge means that relatively small volumes of both can have a large impact on the organic, suspended solids, and nitrogen loads on a wastewater treatment plant. possible consequences include an increase in the volume of screenings and grit requiring removal; increased odour emission at headworks; increased scum and sludge accumulation rates; and increased organic loading, leading to overloading and process failure, and the potential for increased odour and foaming in aeration tanks. because of their partly digested nature, septage and fecal sludge will usually degrade at a slower rate than municipal wastewater. therefore, their presence is likely to have an adverse impact on the efficacy of treatment processes. the intermittent nature of fecal sludge and septage loading can also amplify the problems identified above. despite these possible drawbacks, wastewater treatment facilities with spare capacity are a potential resource to be investigated. even where co-treatment is not an option, existing wastewater treatment plants may provide land in strategic locations, close to areas of demand for septage management services. separate preliminary treatment and solids-liquid separation facilities should always be provided for septage/fecal sludge. solids-liquid separation will reduce both the overall load and the proportion of digested material in the liquid fraction and will thus lessen the possibility that it will disrupt wastewater treatment processes. separated solids can be treated along with the sludge produced in sedimentation tanks during the wastewater treatment process.: 6 technology selection training of enumerators for a survey regarding fecal sludge management needs in nepal a formal process should be used for making an informed technology selection for the treatment of the fecal sludge. it is usually a collaborative process conducted by stakeholders, consultants, the operator and the future owner of the facility. the process is based on a long term vision planning with stakeholders as part of citywide sanitation planning. the expected waste flows (volume), their strength, characteristics, and variability in each area need to be known. a formal and transparent process for developing appropriate plans and designs for wastewater and fecal sludge treatment plants will achieve local buy-in and ownership of technology decisions, which is critical for the long term success and sustainability of the program. reuse options further information: reuse of excreta sludge pellets after processing (including heating, drying and pelletizing) in a ladepa process, ethekwini municipality (south africa) resource recovery from fecal sludge can take many forms, including as a fuel, soil amendment, building material, protein, animal fodder, and water for irrigation. some of the by-products from fecal sludge treatment processes have the potential to offset some of the costs of collection and treatment, thereby reducing tariffs for the households. however, value addition all the way to biogas, biodiesel and electricity is difficult to achieve in practice due to technological and operational challenges. composting composting is a process whereby organic matter is digested in the presence of oxygen with the byproduct of heat. for fecal sludge, the heat deactivates the pathogens while the digestion process breaks down the organic matter into a humus-like material that acts as a soils amendment, and nutrients that are broken down into a form that is more easily taken up by plants. properly treated fecal sludge can be reused in agriculture. fecal sludge is rich in nitrogen. when fecal sludge is mixed with materials that are rich in carbon, such as shredded crop wastes, the composting process can be maximized. proper mixture to achieve a ratio of 20 to 1 to 30 to 1 of carbon to nitrogen is best. solid fuel resource recovery as a solid fuel has been found to have high market potential in sub-saharan africa. the selection of the fuel type will depend on: (1) the intended use of the fuel (e.g. combustion technology, user/handling requirements, and amount required); and (2) the properties of the input fecal sludge (e.g. level of stabilization, sand content, and moisture content). once suitable technology options are identified, they must subsequently be evaluated for best fit in the local context (e.g. local capacity for electricity, land, and technical (operation and maintenance) requirements).: figure 2 others biogas is a renewable energy that is a byproduct of the anaerobic digestion process. treated effluent can be used for agricultural or landscape irrigation. costs and fees fsm is considered an entry point for sanitation improvement programs that are led by local governments. such programs may include tariffs or user fees, promotions campaigns to raise the willingness to pay for the service, and local ordinances that define the rules and regulations governing fsm. in the philippines, tariffs around us$1 per family per month are generally enough to achieve full cost recovery within a period of 3 to 7 years. promotional campaigns are used to raise the willingness to pay for services, and local procedures and ordinances provide additional incentives for compliance. synergies with other sectors fsm is but one aspect of citywide sanitation that also includes: municipal solid waste management; drainage and greywater management; wastewater collection and treatment including effluent overflows from on-site systems where soils based dispersal systems are insufficient to assimilate the volume; water safety; and food safety. there are important synergies between many of these services and fsm, and investigating co-management opportunities can yield benefits. msw can often be co-managed with fecal waste, especially when thermal treatment technologies are used. food waste from restaurants and markets can be co-composted with fecal waste to produce a high value soils amendment. fats, oil and grease (fog) from commercial grease traps can be added to biodigesters to increase methane production, or used in conjunction with fecal sludge as a feedstock for biodiesel production. water supply is also closely linked with fsm as it is often the water utility that will manage programs and their customers that will pay for services through tariffs. examples dumaguete, the philippines usaid has supported efforts to introduce scheduled desludging services in some countries in southeast asia. the first of these was in dumaguete in the philippines. the program was run jointly by the city government and the dumaguete city water district, with the former operating the treatment plant and the water district conducting the desludging. the cost of the scheme was covered by adding a tariff of 2 pesos (about 5 us cents) to the water bill for each cubic meter of water consumed (about one us dollar per family per month). this approach was possible because around 95% of residents had a connection to the water district reticulation system. trucks were to move from neighborhood to neighborhood on a scheduled cycle, emptying pits on a regular 3–4 year cycle. this approach requires a database of all pits and septic tanks requiring desludging. however, dumaguete has by 2018 reverted to an ‘on-call’ system, the cost of which is still covered by the surcharge on the water tariff. it seems that users prefer this small regular payment to having to make large payments when tanks require desludging.