The pit latrine paradox in low-income settings: A sanitation technology of choice or a pollution hotspot?

Response of soil microbial community structure and function to the sewage leakage: A case study of a 25-year-old cesspool

Providing many millions of rural households with decentralized sanitation facilities remains challenging. In undeveloped areas, cesspools have still been widely used due to technologically simple and low-cost. However, the influence of cesspools on the surrounding soil remains unclear. In this study, we investigated the influence of a 25-year-old household cesspool on soil physicochemical factors, microbial community composition and function, pathogens and antibiotic resistance genes (ARGs). Soil at the depth around the sewage liquid level (D70) was mostly disturbed where TOC, NO3-N and TP was increased to 16.8 g/kg, 18.2 mg/kg and 1.02 mg/kg respectively. Correspondingly, the element cycling genes of carbon fixation, methanotrophy, nitrogen fixation, ammonia oxidation, and nitrate reduction etc., were increased at D70. Notably, human derived pathogens such as Enterobacter, Salmonella, Pseudomonas aeruginosa, Klebsiella pneumoniae, Prevotella, and Vibrio were highly enriched by 5-10 folders in D70, indicating the potential health risk to human. Mantel tests suggested that EC, TP, pH, NH3-N and particularly NO3-N are important factors that influence the microbial community and element cycling genes in cesspool-affected soil. Overall, this study revealed the impact of household cesspool leakage on the surrounding soil and provided information for the selection and construction of basic sanitation facilities in poor regions.

Indicators to complement global monitoring of safely managed on-site sanitation to understand health risks

Halfway through the Sustainable Development Goal (SDG) period, there has been little research on the criteria for monitoring safely managed sanitation under SDG target 6.2. For reporting against SDGs, global indicators are necessarily limited and exclude many safety aspects from a public health perspective. Primary survey data from 31,784 households in seven countries in Asia and Africa were analysed, comparing estimates of safely managed on-site sanitation based on global indicators with five complementary indicators of safety: animal access to excreta, groundwater contamination, overdue emptying, entering containments to empty and inadequate protection during emptying. Application of additional criteria reduced the population with safely managed sanitation by 0.4-35% for specific indicators, with the largest impact due to the risk of groundwater contamination, animal access, and containments overdue for emptying. Combining these indicators across the service chain, excluding transport and treatment, found almost three-quarters of on-site systems currently assessed as safely managed with global indicators were considered unsafe based on complementary indicators. A more comprehensive assessment of safety of on-site sanitation can be achieved through these indicators, which could be integrated into national monitoring systems and used to inform sanitation investments that address local health-related risks.

Wastewater-based epidemiology as a public health resource in low- and middle-income settings

In the face of emerging and re-emerging diseases, novel and innovative approaches to population scale surveillance are necessary for the early detection and quantification of pathogens. The last decade has seen the rapid development of wastewater and environmental surveillance (WES) to address public health challenges, which has led to establishment of wastewater-based epidemiology (WBE) approaches being deployed to monitor a range of health hazards. WBE exploits the fact that excretions and secretions from urine, and from the gut are discharged in wastewater, particularly sewage, such that sampling sewage systems provides an early warning system for disease outbreaks by providing an early indication of pathogen circulation. While WBE has been mainly used in locations with networked wastewater systems, here we consider its value for less connected populations typical of lower-income settings, and in assess the opportunity afforded by pit latrines to sample communities and localities. We propose that where populations struggle to access health and diagnostic facilities, and despite several additional challenges, sampling unconnected wastewater systems remains an important means to monitor the health of large populations in a relatively cost-effective manner.

The potential contribution of aquatic wildlife to antibiotic resistance dissemination in freshwater ecosystems: A review

Antibiotic resistance (AR) is one of the major health threats of our time. The presence of antibiotics in the environment and their continuous release from sewage treatment plants, chemical manufacturing plants and animal husbandry, agriculture and aquaculture, result in constant selection pressure on microbial organisms. This presence leads to the emergence, mobilization, horizontal gene transfer and a selection of antibiotic resistance genes, resistant bacteria and mobile genetic elements. Under these circumstances, aquatic wildlife is impacted in all compartments, including freshwater organisms with partially impermeable microbiota. In this narrative review, recent advancements in terms of occurrence of antibiotics and antibiotic resistance genes in sewage treatment plant effluents source compared to freshwater have been examined, occurrence of antibiotic resistance in wildlife, as well as experiments on antibiotic exposure. Based on this current state of knowledge, we propose the hypothesis that freshwater aquatic wildlife may play a crucial role in the dissemination of antibiotic resistance within the environment. Specifically, we suggest that organisms with high bacterial density tissues, which are partially isolated from the external environment, such as fishes and amphibians, could potentially be reservoirs and amplifiers of antibiotic resistance in the environment, potentially favoring the increase of the abundance of antibiotic resistance genes and resistant bacteria. Potential avenues for further research (trophic transfer, innovative exposure experiment) and action (biodiversity eco-engineering) are finally proposed.

Climate warming, environmental degradation and pollution as drivers of antibiotic resistance

Antibiotic resistance is a major challenge to public health, but human-caused environmental changes have not been widely recognized as its drivers. Here, we provide a comprehensive overview of the relationships between environmental degradation and antibiotic resistance, demonstrating that the former can potentially fuel the latter with significant public health outcomes. We describe that (i) global warming favors horizontal gene transfer, bacterial infections, the spread of drug-resistant pathogens due to water scarcity, and the release of resistance genes with wastewater; (ii) pesticide and metal pollution act as co-selectors of antibiotic resistance mechanisms; (iii) microplastics create conditions promoting and spreading antibiotic resistance and resistant bacteria; (iv) changes in land use, deforestation, and environmental pollution reduce microbial diversity, a natural barrier to antibiotic resistance spread. We argue that management of antibiotic resistance must integrate environmental goals, including mitigation of further increases in the Earth's surface temperature, better qualitative and quantitative protection of water resources, strengthening of sewage infrastructure and improving wastewater treatment, counteracting the microbial diversity loss, reduction of pesticide and metal emissions, and plastic use, and improving waste recycling. These actions should be accompanied by restricting antibiotic use only to clinically justified situations, developing novel treatments, and promoting prophylaxis. It is pivotal for health authorities and the medical community to adopt the protection of environmental quality as a part of public health measures, also in the context of antibiotic resistance management.

Municipal wastewater treatment plant showing a potential reservoir for clinically relevant MDR bacterial strains co-occurrence of ESBL genes and integron-integrase genes

Municipal wastewater treatment plants (MWWTPs) are a milieu for co-occurrence of multiple antibiotic resistance genes (ARGs). This facilitates mixing and genetic exchange; and promotes dissemination of multidrug resistance (MDR) to wastewater bacterial communities which is hazardous for the effluent receiving environment. This study investigated the co-occurrence of extended-spectrum beta-lactamase (ESBL) genes (blaTEM, blaCTX-M, blaSHV, blaOXA), and integron-integrase genes (intI1, intI2, intI3) in MDR bacteria isolated from the Bharwara MWWTP in Lucknow, India. Thirty-one MDR bacterial colonies resistant to three or more antibiotics were isolated from three treatment stages of this MWWTP. Six of these: Staphylococcus aureus, Serratia marcescens, Salmonella enterica, Shigella sonnei, Escherichia coli, and Bacillus sp. Had co-occurrence of ESBL and integron-integrase genes. These six isolates were examined for the occurrence of MDR efflux genes (qacA, acrB) and ARGs (aac(3)-1, qnrA1, tetA, vanA) and tested for resistance against 12 different antibiotics. The highest resistance was against penicillin-G (100%) and lowest for chloramphenicol (16.66%). Bacillus sp. Isolate BWKRC6 had the highest co-occurrence of antibiotic resistance-determining genes and was resistant to all the 12 antibiotics tested. The co-occurrence of ESBL, integron-integrase, antibiotic resistance-determining and MDR efflux genes in bacteria isolated from the Bharwara MWWTP indicates that the wastewaters of this treatment plant may have become a hotspot for MDR bacteria and may present human and environmental health hazards. Therefore, there is need for a rapid action to limit the spread of this threat. Public regulatory authorities must urgently implement measures to prevent MWWTPs becoming reservoirs for evolution of antibiotic resistance genes and development of antibiotic resistance.

Water, sanitation, and hygiene implications of large-scale recycling of treated municipal wastewater in semi-arid regions

Access to water, sanitation, and hygiene (WaSH) is crucial for national development, as it improves human health and fulfills a fundamental need. This study examines the impact of a large-scale groundwater (GW) recharge scheme using secondary treated wastewater (STW) on WaSH characteristics and identifies the major determinants of improved WaSH charecteristics in drought-hit regions of Kolar district, southern India. The study quantifies improved WaSH practices by comparing WaSH characteristics between impacted areas (influenced by STW) and non-impacted areas (not influenced by STW) of Kolar, using household survey data. Pearson's chi-square and student's t-test are used to verify differences between WaSH characteristics. Furthermore, a composite WaSH score is formulated, and a hierarchical stepwise multiple linear regression model is constructed to identify major determinants of improved WaSH scores. The results show that impacted areas have better WaSH characteristics, including daily water supply by gram panchayat, enhanced toilet uses among all family members, bathing patterns, cloth washing practices, toilet cleaning patterns, and water consumption per capita per day. The maximum and minimum WaSH scores of impacted areas were 17.50 and 6.50, respectively, while those of non-impacted areas were 14 and 4.5. This study finds that improved water availability, quality, and security due to daily water supply at the household level are the major determinants of improved WaSH practices. These results can inform policymakers in designing sanitation and hygiene improvement policies that integrate water recycling projects in drought-hit areas.

Sustainability of facilities built under the Community-Led Total Sanitation (CLTS) implementation: Moving from basic to safe facilities on the sanitation ladder

In the context of monitoring progress towards SDG target 6.2, a household is counted to have access to sanitation if it uses at least basic sanitation services. Several approaches have been employed to help rural communities to climb up the sanitation ladder such as Community-led Total Sanitation (CLTS), whose primary target is to end open defecation through behavior change. CLTS does not subsidize sanitation facilities, but let households build their own facilities. The types and sustainability of facilities when construction is entrusted to households without guidelines remain understudied. The contribution of CLTS in achieving SDG6.2 also have not been studied. This paper addresses these gaps. Conducted in the province of Sissili in Burkina Faso, our study involved interviewing CLTS implementers, government officials, and community stakeholders. Coupled with household surveys, the data was analyzed using SPSS and Excel software. Findings indicate that CLTS succeeded in motivating households to build latrines hence escalating latrine coverage from 29.51% in 2016 (pre-CLTS) to 90.44% in 2020 (post-CLTS) in the province. However, 97.53% of latrines built were unimproved pit latrines with superstructures and without/with wooden or clay slabs and no roof, of which 19.76% collapsed during the rainy season. During this period, sanitation access rate rose from 11.9% to 17.00%. The study has therefore revealed that CLTS significantly elevates latrine coverage, yet it does not guarantee a proportional rise in sanitation access. This discrepancy results from the type of technologies generated by CLTS, which are not considered in calculating the sanitation access rate due to their unimproved nature. Consequently, further exploration of social approaches is essential, amalgamating technical and engineering aspects. Beyond socio-economic considerations, the sustainability of CLTS and the achievement of access to adequate and safe sanitation also rely on the robustness and resilience of the implemented facilities.

Exploration of appropriate media to influence sustainable on-site sanitation choices in Sri Lanka- visualization with still images or a video

Pit latrines are the most common form of improved sanitation in many rapidly developing countries. However, they cause the highest amount of groundwater pollution among on-site sanitation (OSS) facilities. Many households in developing countries use groundwater as their main or sub-source, and pit latrines are not a sustainable solution. Thus, the conversion from pit latrines to septic tanks is required. We created two types of media, still images and a video, to illustrate the differences in functions and hygiene risks between pit latrines and septic tanks. Moreover, a survey was conducted in Sri Lanka to determine the media choice that would increase the people's preference for septic tanks as their next OSS, even weeks after the information is presented. The choice of the next OSS participants selected before they were presented with the images was the same as that currently in use, reflecting the belief that the problem of pit latrines was not currently apparent and need not be changed. However, a video presentation of the information made it possible for a larger group of people to choose the usage of septic tanks in the future, especially in suburban areas where the problems were likely to occur.