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The combined effect of climate change, rapid industrialisation and traditional water use has created freshwater stress situations in industrial delta regions. Alternative Water Sources (AWSs) offer opportunities to mitigate the freshwater stress issue and, thus, contribute to a sustainable industrial future. This study developed a Decision Support Model (DSM) to assist the decision-makers in selecting the most feasible AWS. In the study location, Tan Thuan Export and Processing Zone (TTZ) of Ho Chi Minh City, rainwater, industrial effluent and brackish water were selected as AWS options and evaluated for technical, environmental, economic, social and institutional criteria. The stakeholder organisations representing government organisations, industrial-zone management organisations and enterprises were selected as decision-makers based on their willingness to explore AWSs. Four DSM scenarios were derived from the varying decision-making power of the selected stakeholder organisations. The results obtained from applying DSM in TTZ showed rainwater as the most feasible AWS for all the scenarios, while the rank of other AWSs fluctuated for different scenarios. To implement the result of DSM in practice, the government should not only focus on formulating clear technological guidelines on AWS quality but also on providing subsidies and creating an environment of social acceptance of AWSs. The DSM allows the decision-makers to determine the most capable AWS in mitigating freshwater stress issues and the changes required to shift towards these AWSs.

Discharge of nitrogen (N) with wastewater causes eutrophication in surface water. On the other hand, nutrient-rich wastewater can be valuable for agriculture. Tailoring N removal or conservation is important to meet the requirements of different water end uses. Improved vertical flow constructed wetlands with hydroponic materials (CWH) as substrata were developed at lab scale in a greenhouse and studied to optimize N removal in CWH. This study investigated the effect of influent COD/N ratios of 5/1 and 15/1 on the removal or conservation of N in CWHs with Syngonium as vegetation and three substrata, pumice, cocopeat, and mineral wool. CWH with pumice showed the highest TN removal at both COD/N ratios. The Syngonium plant significantly contributed to the additional 50% TN removal in CWH. Nitrification of above 90% was observed at both studied COD/N ratios, indicating sufficient oxygenation due to the vertical pulse flow operated CWH. The denitrification process was enhanced at a higher COD/N ratio of 15/1 compared to 5/1 by around 10–40%. The occurring nitrification and denitrification indicate the coexistence of aerobic and anaerobic conditions in CWH, and balancing these conditions is necessary for future applications to remove N for its specific end use, i.e., irrigation water (high standards) or discharge to surface water (low standards).

Ensuring safe irrigation practices is vital to sustaining food production in water-scarce delta areas. Bangladesh and many other developing countries discharge untreated wastewater into their surrounding surface water bodies, serving as the primary irrigation source. This indirect irrigation of wastewater is believed to pose threats to the farmers, consumers and market vendors and may also affect crop and soil quality. To assess the risk, peri-urban farmers who use surrounding water bodies of Khulna city, Bangladesh, for crop irrigation were selected for the study. The microbial and heavy metal concentrations were measured in water samples collected from various locations over different seasons. For heavy metals As, Co, Ni, Cd, Cr, Cu and Pb, concentrations were below the detection limit, whereas Al, Fe, Mn, Ti and Zn were present but below the FAO recommendation limit for safe irrigation. The mean concentrations of microbial parameters were above the thresholds of WHO guidelines for crop irrigation intended for human consumption. Significant temporal variations in Faecal Coliform, E. coli and Enterococcus concentrations in the water samples were observed. The annual risk of infection for farmers was determined using the screening-level Quantitative Microbial Risk Assessment (QMRA). The results indicated that the annual probability of infection with pathogenic E. coli in different seasons ranges between 5 × 10−3 to 5 × 10−2, above the WHO's acceptable threshold for annual risk of infection for safe water reuse in agriculture. During the farmers' survey, around 45% reported health-related issues and more than 26% reported suffering from water-borne diseases after getting in contact with polluted surface water. This illustrates the actuality of the risks in practice. To ensure safe irrigation, the health risks need to be reduced below the acceptable limits. Suggested technical measures include adequate treatment of wastewater before disposal into rivers and access to protective equipment for farmers. This should be complemented by raising awareness through education programs among farmers to reduce accidental ingestion.

The indirect, unplanned use of urban wastewater by peri-urban farmers in developing countries poses a severe risk to the environment and the farmers. Planned water reuse could contribute substantially to the irrigation water demand in peri-urban agriculture and minimize the risk. However, implementing such practice requires a thorough evaluation of stakeholder's perception and the scope within the existing organizational structures. This paper aims to assess the level of awareness, perception, and willingness of different stakeholders toward current practices and the prospect of urban water reuse in Khulna City - one of the most vulnerable cities located in the southwest of Bangladesh due to the consequences of rapid climate changes in the Bengal delta. Also, institutional arrangements and their functioning were analyzed to understand the current sectoral performance. One questionnaire with 385 respondents from the urban area, 32 in-depth interviews and one focus group discussion with farmers in the peri-urban area, and ten interviews with key informants from the government and non-government organization was conducted. Results indicate an overall positive attitude among major stakeholder groups toward planned water reuse for peri-urban agriculture. More than half of the citizens (53%) are willing to pay for the treatment of wastewater and majority of the farmers (66%) are willing to pay for the supply of better-quality irrigation water. However, the public sector responsible for wastewater collection and treatment requires adjustment in rules and regulations to implement planned water reuse. Interrelated factors such as lack of transparency and coordination, shifting responsibilities to other organizations, lack of required resources need to be addressed in the updated rules and regulations. Strategies to enforce current regulations and align all stakeholders are also crucial for collection and treatment of wastewater and its subsequent use for crop production.

Constructed wetlands could be improved with novel substrata to enhance the removal efficiency of micropollutants from wastewater and reduce the spatial footprint. Use of hydroponic substrata like mineral wool, pumice, wood - and coconut fibre is both novel for wastewater treatment, and potentially suitable, due to their hydraulic compatible texture. Since sorption is a key removal process for pollutants in constructed wetlands, this study investigates sorption to novel substrata by six priority micropollutants, caffeine, carbamazepine, ibuprofen, naproxen, sulfamethoxazole and trimethoprim, with diverse Log Kow and pKa values. We found that higher sorption was positively related to substrata's organic matter content. Organic substrata, namely wood - and coconut fibre, demonstrated higher sorption affinity compared with the inorganic substrata mineral wool and pumice, notably regardless of the micropollutants’ Log Kow. Carbamazepine efficiently and rapidly sorbed onto organic substrata, which is particularly noteworthy considering the recalcitrance of carbamazepine in conventional treatment plants. The sorption isotherms were best described by the Freundlich model rather than Langmuir or linear models. We determined that using wood fibre in constructed wetlands would require around 35–66% less area to remove the selected micropollutants, compared to soil as matrix. Thus our results show the potential of using hydroponic substrata such as wood - and coconut fibre to both remove micropollutants in, and reduce the footprint of constructed wetlands.

Freshwater scarcity has increased in the cities of the global South due to rapid urban agglomeration and changing climate. Alternative water resources such as treated wastewater can play a significant role to reduce the water supply-demand gap. In the recent past, wastewater has been used solely for irrigation and other allied agriculture purposes, with limited focus on reuse for other purposes within the cities. Despite the progress in wastewater treatment technology and various policy frameworks, in low income and lower-middle-income countries, limited progress has been made. Through this article, we compare three aspects, representing the wastewater paradigms in India and the Netherlands. The three elements are 1) framing, 2) policy goals, and 3) technical and financial instruments. Using policy document analysis and interviews, we compare water and related policies prepared in India and the Netherlands. We found that the wastewater paradigms have evolved in the two countries. In India, the wastewater paradigms have realized paradigm changes from ‘water resource to meet a basic human need’ to ‘water as an engine of economic growth’ and then to ‘water scarcity and beautification of cities’. In the case of the Netherlands, the wastewater paradigms have changed from an emphasis on ‘public health and environmental concerns’ to the ‘circular economy of wastewater’. Although the Netherlands has to still meet the water quality targets of the European Water Directive Framework with regards to micropollutants, the country has made significant progress towards wastewater treatment and reuse in the last four decades. On the contrary, the Indian wastewater policy domain has room for improvement in terms of designing appropriate financial instruments and governance strategies to increase the urban wastewater treatment capacity and reuse. This article concludes that the use of the concept of wastewater paradigm is useful to show the progress and challenges in the two countries.

Worldwide, every year 525 000 children under the age of five die from diarrhoea. The simple act of washing hands with soap and water can prevent more than one-third of diarrhoeal disease cases. In the densely populated urban areas of the developing world, handwashing wastewater is commonly discharged to the environment without any treatment, creating unhygienic situations and breeding places for different vectors and wasting a valuable resource. However, this relatively clean wastewater can be treated and reused using simple technological solutions. The objective of our water innovation is, therefore, twofold: improving children’s health through stimulating handwashing at schools while at the same time demonstrating the feasibility of water conservation through low-tech, nature-based treatment and safe reuse of handwashing wastewater for irrigation and toilet flushing. To enhance the intrinsic motivation of children and school staff to adopt this innovation, four educational games were developed drawing on theories used in gamification of learning, such as social learning theory and engagement theories. This paper provides an overview of the games and the main results of the game testing. For promoting hygiene among school children, a board and a card game were developed based on the F-diagram – commonly used by water and sanitation practitioners to illustrate the main routes for pathogen transmissions from faeces. In addition, the system linking handwashing wastewater collection, treatment and reuse for irrigation and toilet flushing was simulated by the development of two board games which targeted school children, school staff and the operators of the treatment system. The prototypes and final versions were tested in two schools in the Oromia region in Ethiopia – while the treatment system (constructed wetland) for handwashing wastewater is located in one school. Children that play-tested the games were generally enthusiastic and eager to play repeatedly, which demonstrated that board and card games are appropriate tools to engage with this young target group. We conclude that there is a large potential for development, use, and upscaling of educational games for more sustainable WaSH interventions.

Urban residual flows contain significant amounts of valuable nutrients, which, if recovered, could serve as input for the own city needs or those of its immediate surroundings. In this study, the possibilities for decentralized recovery of nutrient rich residual flows in Santiago, Chile, are studied by means of a case study considering technical and socio-economic criteria. In particular, we calculate circularity indicators for organic matter (OM), nitrogen (N), and phosphorus (P) and cost&ndash, benefits of household and community on-site technological alternatives. Kitchen waste (KW) and garden residues (GR) as well as urine were considered as system inputs whereas urban agriculture, municipality green, or peri-urban agriculture were the considered destinations for nutrients recovered. The technologies studied were anaerobic digestion, vermicomposting, and composting, while urine storage and struvite precipitation were considered for nutrient recovery from urine. Material flow analysis was used to visualize the inputs and outputs of the baseline situation (the traditional urban waste management system), and of the different household and municipality resource recovery scenarios (the decentralized valorization systems). Our findings show that decentralized valorization of KW and GR are a clear win&ndash, win policy, since they can not only produce important environmental benefits for the city in the long run, but also important cost savings considering the landfill fees and residues transportation of the current centralized waste management system.

Agriculture in delta areas of emerging economies is highly reliant on the provision of water with adequate quality. This quality is often under pressure by season-related saltwater intrusion and poor domestic or industrial wastewater management. Methods to separate these two negative impacts on water quality for the delta areas are lacking but essential for proper management and supply of irrigation water. Therefore, the main aim of this research is to propose a method that maps salt and wastewater impacts on seasonal water quality and relate that to different land uses. Khulna, a delta city of Bangladesh was taken as a representative case study. Surface water samples have been collected from different city locations in winter, summer and monsoon seasons, and were analyzed for a variety of chemical-physical water quality parameters. Spatio-temporal variation maps were generated using Inverse Distance Weighted (IDW) interpolation method, and weighted overlay method was employed to map the current irrigation water use suitability based on FAO guidelines for the interpretations of water quality for irrigation. The influence of land-use on water quality was assessed by correlation analysis followed by bi-variate linear regression analysis. Analysis indicated significant (p < 0.05) seasonal dependent variation in water quality parameters, especially for saltwater influenced and generic water quality parameters. Also, the land-use percentage within 500 m radii to the sampling stations had a significant positive correlation with several parameters indicating saltwater and urban wastewater influences. Weighted overlay analysis revealed that during summer, approximately 1/3rd of the total studied area has a severe restriction for irrigation water use. The method presented here was shown to be effective in presenting variabilities on the effects of salinization and wastewater discharge on water quality in urbanized deltas and can be used as a knowledge base for formulating and implementing future urban infrastructure planning to improve irrigation water quality.

”. The corrected paragraph, therefore, reads as follows: Within the group of technologies applied to physical helminth egg removal (not inactivation) from wastewater, land-based post-treatment technologies such as sand filtration, wetlands and polishing ponds are reported to achieve helminth egg removal of 90%–99%, 100% and 100%, respectively [1,25,26]. In addition, Jimenez [19] reported that grit removal followed by a coagulation flocculation process in what is known as advanced primary treatment (APT), combined with an upflow sand filtration, reduced the amount of helminth eggs from 1.2 to 0.2 eggs·L

Studies on the occurrence of pharmaceuticals show that the widely used pharmaceuticals ibuprofen and diclofenac are present in relevant concentrations in the environment. A pilot plant treating hospital wastewater with relevant concentrations of these pharmaceuticals was evaluated for its performance to reduce the concentration of the pharmaceuticals. Ibuprofen was completely removed, whereas diclofenac yielded a residual concentration, showing the necessity of posttreatment to remove diclofenac, for example, activated carbon. Successively, detailed laboratory experiments with activated sludge from the same wastewater treatment plant showed bioremediation potential in the treatment plant. The biological degradation pathway was studied and showed a mineralisation of ibuprofen and degradation of diclofenac. The present microbes were further studied in laboratory experiments, and DGGE analyses showed the enrichment and isolation of highly purified cultures that degraded either ibuprofen or diclofenac. This research illuminates the importance of the involved bacteria for the effectiveness of the removal of pharmaceuticals in a wastewater treatment plant. A complete removal of pharmaceuticals from wastewater will stimulate water reuse, addressing the worldwide increasing demand for clean and safe fresh water.

This research was conducted to study the faecal coliforms removal capacity of downflow hanging sponge (DHS) reactors as a post-treatment for an upflow anaerobic sludge blanket (UASB) reactor. Three long-term continuous laboratory-scale DHS reactors, i.e. a reactor with cube type sponges without recirculation, a similar one with recirculation and a reactor with curtain type sponges, were studied. The porosities of the applied medium were 91%, 87% and 47% respectively. The organic loading rates were 0.86 kgCOD m −3 d −1 , 0.53 kgCOD m −3 d −1 and 0.24 kgCOD m −3 d −1 correspondingly at hydraulic loading rates of 1.92 m 3 m −2 d −1 , 2.97 m 3 m −2 d −1 and 1.32 m 3 m −2 d −1 , respectively (COD: chemical oxygen demand). The corresponding averages for faecal coliform removal were 99.997%, 99.919% and 92.121% respectively. The 1989 WHO guidelines standards, in terms of faecal coliform content for unrestricted irrigation (category A), was achieved with the effluent of the cube type DHS (G1) without recirculation. Restricted irrigation, category B and C, is assigned to the effluent of the cube type with recirculation and the curtain type, respectively. Particularly for organic compounds, the effluent of evaluated DHS reactors complies with USEPA standards for irrigation of so called non-food crops like pasture for milking animals, fodder, fibre, and seed crops.

The feasibility of two accumulation-systems (AC) for anaerobic digestion and storage of concentrated black water with (AC1) or without (AC2) urine + kitchen organic-wastes was investigated. The waste(water) was collected by two vacuum toilet/transport systems. The influent-total COD of the AC2 (53,000 mg/L) was more concentrated by four times than that of the AC1. The suspended COD represented the major part (71–73%) of influent total COD of the two systems. The batch-experiments results showed a high anaerobic biodegradability of the waste(water) (>85%). The AC systems demonstrated stable performance. There was no inhibition effect of NH4 and VFA concentration decreased in time. Total COD removal of 58% was achieved in both systems, after 105 days at 20 °C. Moreover, if only the supernatant in AC1 is withdrawn and the settled sludge stays for the next runs, only 20% of the influent total COD will be in the supernatant. In AC2, 74% of influent ortho-P was removed by precipitation. Therefore, the settled sludge in the AC2 had a high total-P concentration of 1,300 mg/L. The C:N:P ratios of the supernatant and the sludge were 26:13:1 and 35:4.5:1, respectively, in the AC1, and were 28:14:1 and 32:2.4:1, respectively, in AC2.

Anaerobic digestion of concentrated domestic wastewater streams – black or brown water, and solid fraction of kitchen waste is considered as a core technology in a source separation based sanitation concept (DESAR – decentralised sanitation and reuse). A simple anaerobic digester can be implemented for an enhanced primary treatment or, in some situations, as a main treatment. Two reactor configurations were extensively studied; accumulation system (AC) and UASB septic tank at 15, 20 and 25°C. Due to long retention times in an AC reactor, far stabilisation of treated medium can be accomplished with methanisation up to 60%. The AC systems are the most suitable to apply when the volume of waste to be treated is minimal and when a direct reuse of a treated medium in agriculture is possible. Digested effluent contains both liquid and solids. In a UASB septic tank, efficient separation of solids and liquid is accomplished. The total COD removal was above 80% at 25°C. The effluent contains COD and nutrients, mainly in a soluble form. The frequency of excess sludge removal is low and sludge is well stabilised due to a long accumulation time.

A new type of hybrid constructed wetland (CW), consisting of both vertical-baffled flow wetland (VBFW) and horizontal subsurface flow wetland (HSFW), has been deployed in Southern China to naturally accelerate the removal of organic matter and nitrogen. The hybrid CW system is characterised by a combination of continuous baffled flow vertical wetland and ‘S’ pattern horizontal subsurface flow wetland with natural aeration ditches to increase the concentration of dissolved oxygen in the HSFW bed. An internal circulatory system from the HSFW effluent back to the VBFW may optionally be operated to enhance the biological denitrification effect. Cyperus alternifolius is the main macrophyte in the wetland bed. The performance of the hybrid CW was studied with a pilot-scale system and three full-scale systems for municipal sewage treatment in Southern China. The results suggest that this new hybrid CW can achieve removal efficiencies of chemical oxygen demand, suspended solids, ammonia nitrogen, total nitrogen, and total phosphorus of better than 83.6, 95.0, 71.7, 64.5 and 68.1% respectively, with a specific wetland bed area of 0.70–0.93 m2 PE−1. The mean effluent concentrations of these parameters would meet the regulatory discharge limits for wastewater treatment systems (GB18918, 2002) and reuse in the context of agricultural irrigation solutions in China.

Vacuum collected black (toilet) water contains hormones and pharmaceuticals in relatively high concentrations (mu g/L to mg/L range) and separate specific treatment has the potential of minimizing their discharge to surface waters. In this study, the fate of estrogens (natural and synthetical hormones) and pharmaceuticals (paracetamol, metoprolol, propranolol, cetirizine, doxycycline, tetracycline, ciprofloxacin, trimethoprim, carbamazepine, ibuprofen and diclofenac) in the anaerobic treatment of vacuum collected black water followed by nitrogen removal by partial nitritation-anammox was investigated. A new analytical method was developed to detect the presence of several compounds in the complex matrix of concentrated black water. Detected concentrations in black water ranged from 1.1 mu g/L for carbamazepine to >1000 mu g/L for paracetamol. Anaerobic treatment was only suitable to remove the majority of paracetamol (>90%). Metoprolol was partly removed (67%) during aerobic treatment. Deconjugation could have affected the removal efficiency of ibuprofen as concentrations even increased during anaerobic treatment and only after the anammox treatment 77% of ibuprofen was removed. The presence of persistent micro-pollutants (diclofenac, carbamazepine and cetirizine), which are not susceptible for biodegradation, makes the application of advanced physical and chemical treatment unavoidable. (C) 2010 Elsevier Ltd. All rights reserved.

A major fraction of nutrients emitted from households are originally present in only 1% of total wastewater volume. New sanitation concepts enable the recovery and reuse of these nutrients from feces and urine. Two possible sanitation concepts are presented, with varying degree of source separation leading to various recovery products. Separate vacuum collection and transport followed by anaerobic treatment of concentrated black water (BW) demonstrated on a scale of 32 houses preserve 7.6 g/N/p/d and 0.63 gP/p/d amounting to respectively 69 and 48% of the theoretically produced N and P in the household, and 95% of the retained P was shown to be recoverable via struvite precipitation. Reuse of the anaerobic sludge in agriculture can substantially increase the P recovery. Energy recovery in the form of biogas from anaerobic digestion of concentrated BW, fits well in new concepts of sustainable, zero energy buildings. Nutrient recovery from separately collected urine lowers the percentage of nutrient recovery in comparison with BW but can, on the other hand, often be implemented in existing sanitation concepts. Theoretically 11gN/p/d and 1.0 g P/p/d are produced with urine, of which 38–63 and 34–61% were recovered in practice on a scale of 8–160 inhabitants in Sweden. New sanitation concepts with resource recovery and reuse are being demonstrated worldwide and more and more experience is being gained. Uitleg en ervaringen rond het concept nieuwe sanitatie

Although many publications are available on the fate of estrone (E1), 17β-estradiol (E2) and 17α-ethynylestradiol (EE2) during aerobic wastewater treatment, little is published on their fate under strictly anaerobic conditions. Present research investigated the digestibility of E1 and EE2, using digested pig manure, granular UASB sludge, UASB-septic tank sludge and activated sludge as inocula. Besides, actual concentrations were measured in a UASB septic tank treating black water. Under anaerobic conditions E1 is reduced to E2 but the extent of this reduction depends on type of inoculum. No significant loss of the sum of E1 and E2 and of EE2 was observed. Adsorption was responsible for a 32–35% loss of E1 and E2 from the liquid phase in the UASB septic tank and the effluent still contained considerable concentrations of respectively 4.02 μg/l and 18.79 μg/l for E1 and E2 with a large fraction present in conjugated form. No EE2 was detected in the UASB effluent

The fate of oestrone (E1), 17β-oestradiol (E2) and 17α-ethynyloestradiol (EE2) was investigated in a concentrated blackwater treatment system consisting of an UASB septic tank, with micro-aerobic post-treatment. In UASB septic tank effluent a (natural) total concentration of 4.02 μg/L E1 and 18.69 μg/L E2, comprising the sum of conjugated (>70% for E1 and >80% for E2) and unconjugated forms, was measured. During post-treatment the unconjugated oestrogens were removed to below 1 μg/L. A percentage of 77% of the measured unconjugated E1 and 82% of E2 was associated with particles >1.2 μm in the final effluent implying high sorption affinity of both compounds. When spiking the UASB septic tank effluent with E1, E2, EE2 and the sulphate conjugate of E2, removal in the micro-aerobic post-treatment was >99% for both E2 and EE2 and 83% for E1. The lower removal value for E1 was a result of (slow) deconjugation during the treatment, and in the final effluent still 40% of E1 and 99% of E2 was present in conjugated form. The latter was the result of incomplete deconjugation of the spiked E2(3S) in the post-treatment system.

The effect of northern European seasonal temperature changes and low temperature on the performance of upflow anaerobic sludge blanket (UASB)-septic tanks treating black water was studied. Three UASB-septic tanks were monitored with different operational parameters and at different temperatures. The results indicated the feasibility of the UASB-septic tank for (pre)treatment of black water at low temperatures with respect to removal of suspended solids and dissolved organic material. Inoculum sludge had little effect on COD(ss) removal, though in the start-up phase some poorly adapted inoculum disintegrated and washed out, thus requiring consideration when designing the process. Removal of COD(dis) was at first negative, but improved as the sludge adapted to low temperature. The UASB-septic tank alone did not comply with Finnish or Dutch treatment requirements and should therefore be considered mainly as a pre-treatment method. However, measuring the requirements as mgCOD l(-1) may not always be the best method, as the volume of the effluent discharged is also an important factor in the final amount of COD entering the receiving water bodies.

Anaerobic digestion of wastewater should be a core technology employed in decentralised sanitation systems especially when their objective is also resource conservation and reuse. The most efficient system involves separate collection and anaerobic digestion of the most concentrated domestic wastewater streams: black or brown water and solid fraction of kitchen waste. Separate collection using minimal amount of transport water besides saving this resource allows to apply a targeted treatment. A relatively small volume of digested effluent can be directly reused for fertilisation or processed when a high quality product is required. Clean nutrient production requires advanced multi-step treatment but the quality of products is risk-free. The issue of organic micro-pollutants and their accumulation in the environment is recently often addressed. Anaerobic treatment of total domestic wastewater stream can be applied as well. Treated in this way wastewater can be discharged or used for irrigation or fertilisation. The post-treatment will be usually required and its rate of complexity depends on the anaerobic effluent quality and local requirements for final effluent quality. A variety of technological solutions for treatment of domestic wastewater streams and reuse of resources is discussed in this paper.

Co-digestion of concentrated black water and kitchen refuse within the DESAR concept was the objective of this pilot research. The digestion took place in two, non-mixed accumulation reactors (AC1 and AC2) inoculated with digested primary sludge from a WWTP at a temperature of 20°C for a period of around 150 days. Reactor AC1 was fed with a mixture of faeces, urine and kitchen refuse in the equivalent amount that one individual generates per day. The AC2 was fed with a mixture of faeces and kitchen refuse in the equivalent amount that two individuals produce per day. Some contribution of urine to AC2 was not to be avoided. Detailed characterisation of waste(water) was performed. The performance of the stratified reactor was followed by monitoring the reactor content for several reactors' heights as well as being based on the biogas production. In general the system exposed good process stability. The methanisation of 34 and 61% was obtained for AC1 and AC2 respectively. The biogas yield was 26.5 and 50.8 L/p/d for the respective reactors. Proper choice of inoculum as well as good buffering capacity did not lead to accumulation of VFA and an inhibitive effect due to relatively high ammonium concentration. The chosen process is a promising technology showing good process stability especially for high strength influent.

Separation of wastewater streams produced in households according to their origin, degree of pollution and affinity to a specific treatment constitutes a starting point in the DESAR concept (decentralised sanitation and reuse). Concentrated black water and kitchen waste carry the highest load of organic matter and nutrients from all waste(water)streams generated from different human activities. Anaerobic digestion of concentrated black water is a core technology in the DESAR concept. The applicability of the UASB septic tank for treatment of concentrated black water was investigated under two different temperatures, 15 and 25 °C. The removal of total COD was dependent on the operational temperature and attained 61 and 74% respectively. A high removal of the suspended COD of 88 and 94% respectively was measured. Effluent nutrients were mainly in the soluble form. Precipitation of phosphate was observed. Effective sludge/water separation, long HRT and higher operational temperature contributed to a reduction of E. coli. Based on standards there is little risk of contamination with heavy metals when treated effluent is to be applied in agriculture as fertiliser.