Excreta flow mapping along the sanitation service chain, a case of Kombolcha town, Ethiopia

Poor management of fecal sludge (FSM) presents significant risks to public health and the environment. This study employed qualitative and quantitative data collection methods, along with the Shit Flow Diagram (SFD) data analyzing tool to investigate FSM patterns in Kombolcha town, Ethiopia. The findings indicate that 75.7% of housing unites in the town are shared toilets, with multiple households sharing a single facility. The primary toilet technologies used include cistern flush toilets (2.1%), pour/manual flush toilets (19.8%), ventilated improved pit latrines (11.1%), pit latrines with slabs (56.4%), and pit latrines without slabs (10.6%). However, 98.5% of these toilet types had either unlined or only partially lined containments. Furthermore, only 37% of households practice safe pit or sludge tank emptying. As a result, only 17% of fecal sludge goes through the sanitation value chain and is effectively treated, while 39% remains onsite and unemptied, and the remaining 44% is disposed of in a manner that poses risks to the environment and public health. The study highlights the significant public health and environmental risks associated with the high reliance on shared toilets, the prevalence of inadequately lined toilet types, and the low adoption of proper fecal sludge management practices. Addressing these challenges requires the implementation of sanitation bylaws and building code regulations that prioritize hygienic standards and promote improved toilet technologies.

Field-based methods for measuring greenhouse gases emissions from on-site sanitation systems: A systematic review of published literature

On-site sanitation systems (OSS) are a source of greenhouse gas (GHG) emissions. Although efforts have been made recently to measure and quantify emissions from septic tanks using various field-based methods, the vast majority of published literature reporting GHG emissions from OSS units (e.g., pits and tanks) is based on non-empirical evidence. This systematic review presents an overview and limitations of field-based methods used for the quantification of GHG emissions from OSS. Papers published in English were searched in three databases: Google Scholar, PubMed, and Directory of Articles and Journals. Peer-reviewed papers that reported field-based methods applied to containment units in OSS were included in this study. Only eight out of 2085 papers met the inclusion criteria with septic tanks as the sole technology reported and were thus, considered for the review. Most of the studies have been conducted in middle- and high-income countries. Field-based measurements of GHGs are conducted using a flux chamber (FC) and the most commonly used FC methods are (a) the modified simple static FC, (b) automated static FC, and (c) floating FC. Data reported in published studies do not provide sufficient information on the calibration and validation of the results from the FCs used. The complex FC designs, laborious fieldwork operations, and reliance on expensive, specialist equipment, suggest that such methods may not be suitable in Low and Middle-Income countries (LMICs), where resources and access to laboratory facilities are limited. Also, the complexity of pits and tank typology in LMICs (i.e., unstandardised designs and sizes) may be a challenge to the use of FCs with fixed dimensions and set operational conditions. The variation in the quantification methods and resulting emission rates among the studies indicates that gaps prevail in the use of existing methods. Therefore, there is still a need for a simple field-based, easily adaptable FC method with adequate calibration and validation that can help in reliably quantifying the emissions from different OSS in any LMICs.

Wastewater-based epidemiological surveillance to monitor the prevalence of SARS-CoV-2 in developing countries with onsite sanitation facilities

Wastewater-based epidemiology (WBE) has emerged as a valuable approach for forecasting disease outbreaks in developed countries with a centralized sewage infrastructure. On the other hand, due to the absence of well-defined and systematic sewage networks, WBE is challenging to implement in developing countries like Bangladesh where most people live in rural areas. Identification of appropriate locations for rural Hotspot Based Sampling (HBS) and urban Drain Based Sampling (DBS) are critical to enable WBE based monitoring system. We investigated the best sampling locations from both urban and rural areas in Bangladesh after evaluating the sanitation infrastructure for forecasting COVID-19 prevalence. A total of 168 wastewater samples were collected from 14 districts of Bangladesh during each of the two peak pandemic seasons. RT-qPCR commercial kits were used to target ORF1ab and N genes. The presence of SARS-CoV-2 genetic materials was found in 98% (165/168) and 95% (160/168) wastewater samples in the first and second round sampling, respectively. Although wastewater effluents from both the marketplace and isolation center drains were found with the highest amount of genetic materials according to the mixed model, quantifiable SARS-CoV-2 RNAs were also identified in the other four sampling sites. Hence, wastewater samples of the marketplace in rural areas and isolation centers in urban areas can be considered the appropriate sampling sites to detect contagion hotspots. This is the first complete study to detect SARS-CoV-2 genetic components in wastewater samples collected from rural and urban areas for monitoring the COVID-19 pandemic. The results based on the study revealed a correlation between viral copy numbers in wastewater samples and SARS-CoV-2 positive cases reported by the Directorate General of Health Services (DGHS) as part of the national surveillance program for COVID-19 prevention. The findings of this study will help in setting strategies and guidelines for the selection of appropriate sampling sites, which will facilitate in development of comprehensive wastewater-based epidemiological systems for surveillance of rural and urban areas of low-income countries with inadequate sewage infrastructure.

An integrated investigation on anaerobic membrane-based thickening of fecal sludge and the role of extracellular polymeric substances (EPS) in solid-liquid separation

Pre-thickening or primary treatment of fecal sludge (FS) is a major bottleneck in designing fecal sludge treatment plants. This research demonstrates a practical analysis to improve the thickening efficiency of FS using woven fiber microfiltration membrane. A laboratory-scale anaerobic membrane-based thickening tank (MBTT) was investigated. Firstly, the system was operated with unconditioned FS at a flux range of 1-3 L/m²h. Secondly, the system was operated at an optimized flux of 2 L/m²h with conditioners, chitosan, and charcoal dust, at their optimized dosages reported in previous studies. It was observed that the solids accumulation in MBTT was linear and was specific to net solids accumulation. Feed FS was thickened to around 15% of total solids (TS) in 9-14 days. The overall solids accumulation rate was higher with conditioned FS. The less EPS accumulation and higher dewaterability in conditioned FS reduced the brushing frequency of the membrane and consequently, the average filtration duration per cycle was increased. Strong correlations of dewatering time with floc size, EPS, and electrical conductivity, indicated that higher EPS in FS tends to form flocs which can increase the dewatering rate in unstabilized FS. In permeate, the average TS and COD_t removal observed were 72-78% and 87-91%, respectively.

Resolving the relative contributions of cistern and pour flushing to toilet water usage: Measurements from urban test sites in India

A challenge in water reuse for toilet flushing in India and other Asian countries derives from pour flushing practices. It is a common assumption that the amount of pour flushed water used for personal cleansing is small in comparison to the cistern flush volume, however there is a knowledge gap regarding the actual contribution of each water source to the blackwater amount. In this study, digital water meters were used to measure the fraction of water from personal wash tap relative to cistern water that is used for toilet flushing. High temporal resolution measurements were carried in three different urban sites in the city of Coimbatore in the southern Indian state of Tamil Nadu where onsite sanitation treatment prototypes that may provide reclaimed water for cistern flushing are being tested. Data collected over periods of up to 2 months show that the contribution of the cistern flush to the total blackwater volume is low (14-40%). These data highlight an important factor to inform interventions designed around water reuse for flushing in world geographies where personal toilet cleansing by water is the common practice.

Nouveau design solar septic tank: Reinvented toilet technology for sanitation 4.0

The up-flow solar septic tank (UTST) and multi-soil layering (MSL) system has been developed and proposed as "Nouveau Design Solar Septic Tank". The objective of this study was to verify functionality of the integrated UTST and MSL system for treatment of toilet wastewater (or black water) under actual conditions over a year at the Asian Institute of Technology campus, Pathumthani province, central Thailand. During the operation period which involved fluctuating flow rates, ambient temperatures and black water characteristics, the UTST unit yielded satisfactory performance with the average treatment efficiencies of 92 ± 10% for total chemical oxygen demand (TCOD), 79 ± 10% for soluble chemical oxygen demand (SCOD), 93 ± 9% for total 5-days biochemical oxygen demand (TBOD) and 90 ± 12% for soluble 5-days biochemical oxygen demand (SBOD), respectively, while the MSL unit could remove 95 ± 3%, and 88 ± 15% of total kjeldahl nitrogen (TKN) and total phosphorus (TP), respectively. The effluent TCOD, TBOD, TKN, nitrite (NO₂-N), nitrate (NO₃-N), ammonia (NH₃) and TP concentrations of the integrated UTST and MSL system were 39 ± 27,8 ± 27,5 ± 5 mg/L, 2 ± 2,39 ± 24,8 ± 9,2 ± 5 and 1 ± 1 mg/L, respectively, meeting the ISO requirements. The removal efficiencies of TCOD, SCOD, TBOD and SBOD exhibited positive correlation with the ratios of TBOD/TKN, TBOD/SBOD and TBOD/TP. With high treatment efficiencies and effluent quality meeting the ISO requirements, the nouveau design solar septic tank has been demonstrated as an innovative technology toward the sanitation 4.0 concept and the Sustainable Development Goal no. 6 (SDG6).

Field testing of a household-scale onsite blackwater treatment system in Coimbatore, India

4.2 billion people live without access to safely managed sanitation services. This report describes the field testing of an onsite prototype system designed to treat blackwater from a single flush toilet and reuse of the treated effluent for flushing. The system passes wastewater through a solid-liquid separator followed by settling tanks and granular activated carbon columns into an electrochemical reactor that oxidizes chloride salts from urine to generate chlorine to remove pathogens. The objectives of the study were to verify the functionality of the system (previously demonstrated in the laboratory) under realistic use conditions, to identify maintenance requirements, and to make a preliminary assessment of the system's user acceptability. The prototype was installed in a women's workplace and residential toilet block in Coimbatore, India, and tested over a period of 10 months. The treated water met stringent disinfection threshold for both E. coli and helminth eggs and produced a clear, colorless effluent that met or nearly met local and international discharge standards for non-sewered sanitation systems. The effluent had an average chemical oxygen demand of 81 mg/L, total suspended solids of 11 mg/L, and reduction of total nitrogen by 65%. These tests determined the recommended service lifetimes and maintenance intervals for key system components including the electrochemical cell, granular activated carbon columns, and solid-liquid separator. User feedback regarding the use of treated blackwater as flush water was positive. These findings will inform the design and implementation of next-generation systems currently under development.

Field testing of a household-scale onsite blackwater treatment system in South Africa

Innovations that enable cost-effective and resource-conserving treatment of human waste are required for the 4.2 billion people in the world who currently lack safe and reliable sanitation services. Onsite treatment and reuse of blackwater is one strategy towards this end, greatly reducing the need to transport wastewater over long distances either via sewers or trucks. Here, we report on the field testing of a prototype onsite blackwater treatment system conducted over a period of 8 months. The system was connected to a women's toilet in a public communal ablution block located in an informal settlement near Durban, South Africa. Liquid waste was treated by separation and diversion of large solids, settling of suspended solids, and filtration through activated carbon prior to disinfection by electrochemical oxidation. System performance was monitored daily by measurement of chemical and physical water quality parameters onsite and confirmed by periodic detailed analysis of chemical and biological parameters at an offsite lab. Daily monitoring of system performance indicated that the effluent had minimal color and turbidity (maximum 90 Pt/Co units and 6.48 NTU, respectively), and consistent evolution of chlorine as blackwater passed through the system. Weekly offsite analysis confirmed that the system consistently inactivated pathogens (E. coli and coliforms) and reduced chemical oxygen demand and total suspended solids to meet ISO 30500 category B standards. Significant reductions in total nitrogen load were also observed, though these reductions often fell short of the 70% reduction required by ISO 30500. No significant reduction in total phosphorus was observed. Maintenance requirements were identified, and the resilience of the system to restart following a prolonged shutdown was demonstrated, but significant improvements are required in the design of the solid/liquid separation mechanism for application of this system in a wiping culture.