On-site sanitation provisions in urban slums rarely prioritise grey water management, yet it forms the largest fraction of wastewater. This study was carried out to characterise grey water and quantify its pollutant loads in Bwaise III (Uganda) and to provide data for grey water management in urban slums of developing countries. Samples were collected for analysis from ten representative households as well as from four tertiary drains and the main drainage channel for 7 months in two dry seasons. Grey water production was found to comprise 85 % of the domestic water consumption. The chemical oxygen demand (COD) concentration in the grey water generated by laundry, in the kitchen and in the bathroom was 9,225 ± 1,200 mg L⁻¹, 71,250 ± 1,011 mg L⁻¹ and 4,675 ± 750 mg L⁻¹, while the BOD₅ (biochemical oxygen demand) to COD ratio was 0.24 ± 0.05, 0.33 ± 0.08 and 0.31 ± 0.07, respectively. The maximum concentration of Escherichia coli and total coliforms was 2.05 × 10⁷ cfu (100 mL)⁻¹ and 1.75 × 10⁸ cfu (100 mL)⁻¹, respectively, in grey water from the bathroom, while that of Salmonella spp. was 7.32 × 10⁶ cfu (100 mL)⁻¹ from laundry. Analysis of variance (ANOVA) showed a significant difference in the concentration of COD, total suspended solids (TSS), total organic carbon (TOC), dissolved organic carbon (DOC), total phosphorus (TP), sodium adsorption ratio (SAR), oil and grease, and Salmonella spp. in grey water from laundry, bathroom and kitchen (p < 0.05). The high loads of COD (>500 kg day⁻¹), TSS (>200 kg day⁻¹), nutrients (8.3 kg TKN day⁻¹ and 1.4 kg TP day⁻¹) and microorganisms (10⁶ to 10⁹ cfu c⁻¹day⁻¹) originating from grey water in Bwaise III show that grey water poses a threat to the environment and a risk to human health in urban slums. Therefore, there is a need to prioritise grey water treatment in urban slums of developing countries to achieve adequate sanitation.

@en

Two uPVC columns (outer diameter 160cm, internal diameter 14.6cm and length 100cm) were operated in parallel and in series to simulate grey water treatment by media based filtration at unsaturated conditions and constant hydraulic loading rates (HLR). Grey water from bathroom, laundry and kitchen activities was collected from 10 households in the Bwaise III slum in Kampala (Uganda) in separate containers, mixed in equal proportions followed by settling, prior to transferring the influent to the tanks. Column 1 was packed with lava rock to a depth of 60cm, while column 2 was packed with lava rock (bottom 30cm) and silica sand, which was later replaced by granular activated carbon (top 30cm) to further investigate nutrient removal from grey water. Operating the two filter columns in series at a HLR of 20cm/day resulted in a better effluent quality than at a higher (40cm/day) HLR. The COD removal efficiencies by filter columns 1 and 2 in series amounted to 90% and 84% at HLR of 20cm/day and 40cm/day, respectively. TOC and DOC removal efficiency amounted to 77% and 71% at a HLR of 20cm/day, but decreased to 72% and 67% at a HLR of 40cm/day, respectively. The highest log removal of Escherichia coli, Salmonella sp. and total coliforms amounted to 3.68, 3.50 and 3.95 at a HLR of 20cm/day respectively. The overall removal of pollutants increased with infiltration depth, with the highest pollutant removal efficiency occurring in the top 15cm layer. Grey water pre-treatment followed by double filtration using coarse and fine media has the potential to reduce the grey water pollution load in slum areas by more than 60%.

@en

Decentralised grey water treatment in urban slums using low-cost and robust technologies offers opportunities to minimise public health risks and to reduce environmental pollution caused by the highly polluted grey water i.e. with a COD and N concentration of 3000-6000mgL^-1 and 30-40mgL^-1, respectively. However, there has been very limited action research to reduce the pollution load from uncontrolled grey water discharge by households in urban slums. This study was therefore carried out to investigate the potential of a two-step filtration process to reduce the grey water pollution load in an urban slum using a crushed lava rock filter, to determine the main filter design and operation parameters and the effect of intermittent flow on the grey water effluent quality. A two-step crushed lava rock filter unit was designed and implemented for use by a household in the Bwaise III slum in Kampala city (Uganda). It was monitored at a varying hydraulic loading rate (HLR) of 0.5-1.1md^-1 as well as at a constant HLR of 0.39md^-1. The removal efficiencies of COD, TP and TKN were, respectively, 85.9%, 58% and 65.5% under a varying HLR and 90.5%, 59.5% and 69%, when operating at a constant HLR regime. In addition, the log removal of Escherichia coli, Salmonella spp. and total coliforms was, respectively, 3.8, 3.2 and 3.9 under the varying HLR and 3.9, 3.5 and 3.9 at a constant HLR. The results show that the use of a two-step filtration process as well as a lower constant HLR increased the pollutant removal efficiencies. Further research is needed to investigate the feasibility of adding a tertiary treatment step to increase the nutrients and microorganisms removal from grey water.

@en

Aims: To determine the magnitude of microbial risks from waterborne viruses and bacteria in Bwaise III in Kampala (Uganda), a typical slum in Sub-Saharan Africa. Methods and Results: A quantitative microbial risk assessment (QMRA) was carried out to determine the magnitude of microbial risks from waterborne pathogens through various exposure pathways in Bwaise III in Kampala (Uganda). This was based on the concentration of Escherichia coli O157:H7, Salmonella spp., rotavirus (RV) and human adenoviruses F and G (HAdV) in spring water, tap water, surface water, grey water and contaminated soil samples. The total disease burden was 680 disability-adjusted life years (DALYs) per 1000 persons per year. The highest disease burden contribution was caused by exposure to surface water open drainage channels (39%) followed by exposure to grey water in tertiary drains (24%), storage containers (22%), unprotected springs (8%), contaminated soil (7%) and tap water (0·02%). The highest percentage of the mean estimated infections was caused by E. coli O157:H7 (41%) followed by HAdV (32%), RV (20%) and Salmonella spp. (7%). In addition, the highest infection risk was 1 caused by HAdV in surface water at the slum outlet, while the lowest infection risk was 2·71 × 10^-6 caused by E. coli O157:H7 in tap water. Conclusions: The results show that the slum environment is polluted, and the disease burden from each of the exposure routes in Bwaise III slum, with the exception of tap water, was much higher than the WHO reference level of tolerable risk of 1 × 10^-6 DALYs per person per year. Significance and Impact of the Study: The findings of this study provide guidance to governments, local authorities and nongovernment organizations in making decisions on measures to reduce infection risk and the disease burden by 10² to 10⁵ depending on the source of exposure to achieve the desired health impacts. The infection risk may be reduced by sustainable management of human excreta and grey water, coupled with risk communication during hygiene awareness campaigns at household and community level. The data also provide a basis to make strategic investments to improve sanitary conditions in urban slums.

@en

The presence of viruses in a slum environment where sanitation is poor is a major concern. However, little is known of their occurrence and genomic copy concentration in the slum environment. The main objective of this study was to determine the genomic copy concentrations of human adenoviruses F and G, Rotavirus (RV), Hepatitis A virus (HAV), Hepatitis E virus (HEV) and human adenovirus species A,C,D,E, and F (HAdV-ACDEF) in Bwaise III, a typical slum in Kampala, Uganda. Forty-one samples from surface water, grey water and ground water were collected from 30 sampling locations. The virus particles were recovered by glass wool filtration with elution using beef extract. DNA and RNA viruses were detected by the real time quantitative polymerase chain reaction (qPCR) and the reverse transcription-qPCR (RT-qPCR), respectively. HAdV-F and G were detected in 70.7% of the samples with concentrations up to 2.65 × 101 genomic copies per mL (gc mL-1). RV and HAV were detected in 60.9% and 17.1% of the samples, respectively. The maximum concentration of RV was 1.87 × 102 gc mL-1. In addition, 78% of the samples tested positive for the HAdV-ACDEF, but all samples tested negative for HEV. These new data are essential for quantitative microbial risk assessment, and for understanding the effects of environmental pollution in slums.@en

Poor sanitation in urban slums results in increased prevalence of diseases and pollution of the environment. Excreta, grey water and solid wastes are the major contributors to the pollution load into the slum environment and pose a risk to public health. The high rates of urbanization and population growth, poor accessibility and lack of legal status in urban slums make it difficult to improve their level of sanitation. New approaches may help to achieve the sanitation target of the Millennium Development Goal (MDG) 7; ensuring environmental sustainability. This paper reviews the characteristics of waste streams and the potential treatment processes and technologies that can be adopted and applied in urban slums in a sustainable way. Resource recovery oriented technologies minimise health risks and negative environmental impacts. In particular, there has been increasing recognition of the potential of anaerobic co-digestion for treatment of excreta and organic solid waste for energy recovery as an alternative to composting. Soil and sand filters have also been found suitable for removal of organic matter, pathogens, nutrients and micro-pollutants from grey water.

@en

Provision of sanitation solutions in the world's urban slums is extremely challenging due to lack of money, space, access and sense of ownership. This paper presents a technology selection method that was used for the selection of appropriate sanitation solutions for urban slums. The method used in this paper takes into account sustainability criteria, including social acceptance, technological and physical applicability, economical and institutional aspects, and the need to protect and promote human health and the environment. The study was carried out in Bwaise III; a slum area in Kampala (Uganda). This was through administering of questionnaires and focus group discussions to obtain baseline data, developing a database to compare different sanitation options using technology selection criteria and then performing a multi-criteria analysis of the technology options. It was found that 15% of the population uses a public pit latrine; 75% uses a shared toilet; and 10% has private, non-shared sanitation facilities. Using the selection method, technologies such as Urine Diversion Dry Toilet (UDDT) and biogas latrines were identified to be potentially feasible sanitation solutions for Bwaise III. Sanitation challenges for further research are also presented.

@en