Globally, there is a dire need for a new class of advanced non-sewered sanitation systems (NSSS) to provide onsite wastewater treatment that is capable of meeting stringent discharge or reuse criteria. These systems need to be simple to operate and maintain, reliable, and resilient to unreliable electrical service. The NEWgenerator (NG) is a compact, automated, solar-powered wastewater treatment system comprised of three major treatment processes: anaerobic membrane bioreactor (AnMBR), nutrient capture system (NCS) with ion exchange and carbon sorption, and electrochlorination (EC). The NG system operated at an informal settlement community in South Africa over a 534 d period, treating high-strength blackwater (BW) and yellow water (YW) from a public toilet facility. Over three test stages (BW, BW + YW, BW) that included several periods of dormancy, the NG system was able to provide a high level of removal of total suspended solids (97.6 ± 3.1%), chemical oxygen demand (94.5 ± 5.0%), turbidity (96.3 ± 9.7%), color (92.0 ± 10.5%), total nitrogen (82.1 ± 24.0%), total phosphorus (43.0 ± 22.1%), E. coli (7.4 ± 1.5 LRV, not detected in effluent), and helminth ova (not detected in effluent). The treatment levels met most of the ISO 30500 NSSS standard for liquid effluent and local water reuse criteria. A series of maintenance events were successfully conducted onsite over the 534 d field trial: two membrane cleanings, two NCS regenerations, and granular activated carbon replacement. Desludging, a major pain point for onsite sanitation systems, was unnecessary during the field trial and thereby not performed. The AnMBR performed well, removing 94.5 ± 5.0% of the influent COD across all three stages. The high COD removal rate is attributed to the sub-micron separation provided by the ultrafiltration membrane. The NCS was highly efficient at removing total nitrogen, residual COD and color, but the regeneration process was lengthy and is a topic of ongoing research. The EC provided effective disinfection, but frequent prolonged run cycles due to power supply and water quality issues upstream limited the overall system hydraulic throughput. This extended field trial under actual ambient conditions successfully demonstrated the feasibility of using advanced NSSS to address the global water and sanitation crises.
Trials at a wastewater treatment works indicate that cross-flow microfiltration, using flexible woven fibre tubes, could significantly enhance the performance of anaerobic digesters. The cross-flow microfiltration unit decouples the solids residence time from the liquid residence time and thus enables the volumetric throughput of the digester to be significantly increased while maintaining a constant solids residence time and volatile solids destruction. In trials on a pilot-plant digester, the volumetric throughput was almost doubled, from 70 to 130 1 d−1, while the solids residence time was maintained at 26 days. The economic feasibility of the coupled system was evaluated, using permeate flux data obtained from a cross-flow microfiltration unit coupled to a full-scale digester. The evaluation indicates that the coupled process is economically favourable when compared to conventional digester systems. The coupled system is currently being developed into a full-scale process. A full-scale CFMF unit is being constructed and will be coupled to a full-scale digester. Over a three year project the long-term reliability and operability of the process will be investigated, together with its effect on digester fluid dynamics and biomass viability.
Denitrification kinetics and wastewater characterization of eight different plants in Europe are discussed. Denitrification batch tests revealed three distinct rates except in the cases of Plaisir, Rostock and Orense where 4 rates were observed. The latter three plants revealed atypical rapid initial rates which were between 7 and 21 mgN/gVSS.h. All denitrification kinetics under non-limiting carbon conditions revealed fast first rates which ranged between 3.0 and 7.3 mgN/gVSS.h. Acetate was used to simulate denitrification kinetics with readily biodegradable COD present. Two subsequent rates were observed. Rates 2 and 3 ranged between 2 and 3 mgN/gVSS.h, and 1 and 2 mgN/gVSS.h, respectively. The RBCOD fraction varied between 10 and 19%, except for one of the plants where the value determined was 7%.
Shared sanitation is widely proposed as a means to increase access to improved sanitation. There are few reports of a causal relationship between the use of shared sanitation and community-acquired diarrhoea. This paper presents an analytical review of studies that have investigated the relationship between the use of shared sanitation and the prevalence of (1) diarrhoeal disease and (2) soil-transmitted helminth (STH) infections. Data were extracted from the reviewed literature to calculate odds ratios (ORs) and confidence intervals (CIs). The use of shared sanitation showed a significant increase in diarrhoeal diseases, with an overall OR of 2.39 (85% CI 1.15–8.31). Children under 5 years were slightly less affected with a prevalence ratio of 1.09 (95% CI 1.06–1.12). The number of published reports on STH infections in relation to shared sanitation was limited, but the few that do exist report on ‘improved sanitation’, showing a positive and protective impact with an overall OR of 0.49 (95% CI 0.28–0.89), which is contrary to the negative impact related to diarrhoea. Despite the limited information on the direct link between shared sanitation and incidence of diarrhoeal/STH infections, this literature review demonstrates that the relationship deserves close attention in future practice and research. This article has been made Open Access thanks to the generous support of a global network of libraries as part of the Knowledge Unlatched Select initiative.
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