Public health performance of sanitation technologies in Tamil Nadu, India: Initial perspectives based on E. coli release

Review of linear and circular approaches to on-site domestic wastewater treatment: Analysis of research achievements, trends and distance to target

This comprehensive review critically assesses traditional and emerging technologies for domestic wastewater treatment and reuse, focusing on the transition from conventional centralised systems to innovative decentralised approaches. Through an extensive literature search on domestic wastewater systems serving a population equivalent of less than or equal to 10, the study juxtaposes linear and circular methods and highlights their impact on urban water management and the environment. The papers reviewed were classified into five categories: Environmental studies, economic studies, social studies, technological studies, and reviews and policy papers. The analysis was carried out separately for linear and circular approaches within each category. In addition, the maturity of the technology (lab/pilot or full-scale application) was taken into account in the analysis. The research landscape is shown to be evolving towards circular methods that promise sustainability through resource recovery, despite the dominance of linear perspectives. The lack of clear progress in decentralised technologies, the scarcity of circularity assessments and the challenges of urban integration are highlighted. Operational reliability, regulatory compliance and policy support are identified as key barriers to the adoption of decentralised systems. While conventional pollutants and their environmental impacts are well addressed for linear systems, the study of emerging pollutants is in its infancy. Conclusions on the impact of these hazardous pollutants are tentative and cautious. Social and economic studies are mainly based on virtual scenarios, which are useful research tools for achieving sustainability goals. The conceptual frameworks for assessing the social dimension need further refinement to be effective. The paper argues for a balanced integration of centralisation and decentralisation, proposing a dual strategy that emphasizes the development of interoperable technologies. It calls for further research, policy development and widespread implementation to promote decentralised solutions in urban water management and pave the way for sustainable urban ecosystems.

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.

Shared sanitation in informal settlements: A systematic review and meta-analysis of prevalence, preferences, and quality

Shared sanitation facilities are not considered a type of basic sanitation by the WHO/UNICEF Joint Monitoring Programme (JMP), though they may be the only alternative to open defecation in urban informal settlements. Additionally, JMP indicators for sanitation do not cover aspects related to the quality of shared sanitation, such as those outlined in the Human Right to Water and Sanitation (HRTWS) framework. Data on the prevalence of shared sanitation within informal settlement areas is limited, and there is a need to understand user preferences, experiences, and barriers to the use of shared sanitation to inform effective policy and practice. This systematic review aims to summarize the prevalence and number of households sharing sanitation in informal settlements globally, as well as user experiences and barriers to successful implementation of shared sanitation. We included studies available in English and published after January 1, 2000. We retrieved 4741 articles from seven databases and included a total of 167 relevant publications. Among included studies, 54 reported the prevalence of shared sanitation in informal settlements, and 138 studies reported on user perceptions and experiences related to shared sanitation quality. A meta-analysis of studies reporting the prevalence of shared sanitation in informal settlements globally revealed an estimated overall prevalence of 67% [95% CI: 61%-73%]. Commonly reported user preferences included cleanliness to promote continued use of shared facilities, privacy with a lockable door, facilities for menstrual hygiene management, safety and protection against violence, 24/7 access, proper lighting, and shared responsibility for facility management - which align with the HRTWS framework and represent barriers to shared sanitation use. Based on the findings of this review, we recommend including the number of households or people sharing a sanitation facility in monitoring of shared sanitation quality, locating sanitation facilities within compounds, where applicable, and promoting safety, dignity, and privacy of all users in the development of shared sanitation quality indicators.

Social barriers to safe sanitation access among housed populations in the United States: A systematic review

BACKGROUND

Nearly six million people residing in the United States do not have access to safely managed sanitation. Housed populations may lack access to centralized wastewater treatment systems or functioning onsite wastewater treatment systems, which subsequently places them at higher risk for adverse health outcomes associated with unsafe sanitation.

OBJECTIVES

We sought to understand the various social barriers that impact access to safe sanitation in the United States.

METHODS

We included peer-reviewed studies published between January 2000 and March 2023. The publication search was conducted using Scopus, ProQuest Social Science Database, and HeinOnline. We extracted data on social barriers and physical factors associated with access to sanitation.

RESULTS

Twenty publications met the inclusion criteria, and data relating to 11 social barriers and two physical factors were extracted. The social barriers to safe sanitation access mentioned most frequently were found to be socioeconomic status and race-based discrimination. Studies discussed sanitation in communities in five states.

DISCUSSION

Barriers pertained to lack of access to centralized wastewater treatment system, inadequate repair or replacement of septic systems, and lack of safely managed onsite sanitation systems. We discuss the intersectionality of the barriers, the underlying policy and history that leads to them, and make recommendations to address inequitable access to safe sanitation. Legislation and policy must be critically reviewed at national, state, and local levels to limit or eliminate ability for utilities to be extended on the basis of a community's income and property values or racial makeup. Policy recommendations also include additional community engagement, onsite sanitation system monitoring, and knowledge dissemination and education of septic system users. More geographically diverse research and research on sanitation in specific communities such as those of migrant farmworkers, undocumented persons, and tenants are recommended.

Greenhouse gas emissions from on-site sanitation systems: A systematic review and meta-analysis of emission rates, formation pathways and influencing factors

Onsite sanitation systems (OSS) are significant sources of greenhouse gases (GHG) including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). While a handful of studies have been conducted on GHG emissions from OSS, systematic evaluation of literature on this subject is limited. Our systematic review and meta-analysis provides state-of-the- art information on GHG emissions from OSS and identifies novel areas for investigation. The paper analyzes GHG emission rates from different OSS, the influence of various design, operational, and environmental factors on emission rates and proffers mitigation measures. Following the Preferred Reporting Items for Systematic reviews and Meta-analysis (PRISMA) guidelines, we identified 16 articles which quantified GHG emissions from OSS. Septic tanks emit substantial amounts of CO2 and CH4 ranging from 1.74 to 398.30 g CO2/cap/day and 0.06-110.13 g CH4/cap/day, respectively, but have low N2O emissions (0.01-0.06 g N₂O/cap/day). CH4 emissions from pit latrines range from 0.77 to 20.30 g CH4/cap/day N2O emissions range from 0.76 to 1.20 gN2O/cap/day. We observed statistically significant correlations (p < 0.05) between temperature, biochemical oxygen demand, chemical oxygen demand, dissolved oxygen, storage period, and GHG emissions from OSS. However, no significant correlation (p > 0.05) was observed between soil volumetric water content and CO2 emissions. CH4 emissions (expressed as CO2 equivalents) from OSS estimated following Intergovernmental Panel for Climate Change (IPCC) guidelines were found to be seven times lower (90.99 g CO2e/cap/day) than in-situ field emission measurements (704.7 g CO2e/cap/day), implying that relying solely on IPCC guidelines may lead to underestimation of GHG emission from OSS. Our findings underscore the importance of considering local contexts and environmental factors when estimating GHG emissions from OSS. Plausible mitigation measures for GHG emissions from OSS include converting waste to biogas in anaerobic systems (e.g. biogas), applying biochar, and implementing mitigation policies that equally address inequalities in sanitation service access. Future research on GHG from OSS should focus on in-situ measurements of GHGs from pit latrines and other common OSS in developing countries, understanding the fate and transport of dissolved organics like CH4 in OSS effluents and impacts of microbial communities in OSS on GHG emissions. Addressing these gaps will enable more holistic and effective management of GHG emissions from OSS.

Assessment of sanitation infrastructure resilience to extreme rainfall and flooding: Evidence from an informal settlement in Kenya

Sanitation infrastructure can fail during heavy rainfall and flooding, allowing the release of fecal waste - and the pathogens it carries - into spaces where people live, work, and play. However, there is a scarcity of reliable frameworks that can effectively assess the resilience of such infrastructure to extreme rainfall and flooding events. The purpose of this study was to develop and apply a novel framework for assessing and ranking the resilience of sanitation infrastructure in informal settlements. A framework for assessing sanitation infrastructure resilience was developed consisting of 19 indicators that were categorized into three domains: physical infrastructure design (8 indicators), operations and management (5 indicators), and environmental factors (6 indicators). The framework was applied to data from 200 shared sanitation facilities in Kibera, Kenya, collected through transect walks, field observations, surveys, and sanitary risk inspections. Results indicate that sanitation infrastructure type impacts resilience. Toilet facilities connected to a piped sewer (r = 1.345, 95% CI: 1.19-1.50) and toilets connected to a septic system (r = 1.014, 95% CI: 0.78-1.25) demonstrated higher levels of resilience compared to latrines (r = 0.663, 95% CI: 0.36-0.97) and hanging toilets (r = 0.014, 95% CI: 0.30-0.33) on a scale ranging from 0 to 4. The key determinants of sanitation infrastructure resilience were physical design, functionality, operational and maintenance routines, and environmental factors. This evidence provides valuable insights for developing standards and guidelines for the design and safe siting of new sanitation infrastructure and encourages investment in sewer and septic systems as superior options for resilient sanitation infrastructure. Additionally, our findings underscore the importance for implementers and communities to prioritize repairing damaged infrastructure, sealing potential discharge points into open drains, and emptying filled containment systems before the onset of the rainy season.

Influence of sanitation facilities on diarrhea prevalence among children aged below 5 years in flood-prone areas of Bangladesh: a multilevel analysis

Although the improvement of sanitation facilities has been a major contributor to improving public health, it is not guaranteed to prevent negative health outcomes. This is especially true in areas affected by severe natural disasters, such as flooding or extreme rainfall. Previous studies have examined the association between catastrophic natural disasters and negative health outcomes. However, studies on disaster-prone areas are limited. This study focused on the impact of flood risks and examined whether the improvement of sanitation facilities would be sufficient to suppress the prevalence of diarrhea in flood-prone areas. Two secondary datasets including geodata on flood-prone areas were used for the analysis: one each was obtained from the Bangladesh Demographic and Health Survey and Bangladesh Agricultural Research Council. Two models with categorizations of sanitation facilities based on containment type and excreta flow were applied for analysis. Results showed that the severe flood-prone areas and "diffused" type of sanitation, where the feces are diffused without any containment, had significant positive associations with diarrhea prevalence; however, the interaction between them was negative. Moderate flood-prone areas had a significant positive association with diarrhea prevalence; however, the interaction with unimproved sanitation, which includes containment without clear partition from feces, was significantly negative. These findings indicate that improved sanitation or containment type of sanitation may not positively contribute to the prevention of diarrhea in these severe- and moderate-flood prone areas. The urgent need for alternative sanitation technologies should be addressed in flood-prone regions.

Effect of Turning Frequency on the Survival of Fecal Indicator Microorganisms during Aerobic Composting of Fecal Sludge with Sawdust

The study investigated the effect of turning frequency on survival of fecal indicator pathogens (E. coli, Enterococcus spp., Salmonella spp. and helminth eggs) during fecal sludge (FS) co-composting with sawdust. Dewatered FS was mixed with sawdust and composted on a pilot scale using different turning frequencies-i.e., 3 days (3TF), 7 days (7TF), and 14 days (14TF). Composting piles were monitored weekly for survival of fecal indicator microorganisms and evolution of selected physical and chemical characteristics for 14 weeks. Our results show that turning frequency has a statistically significant (p < 0.05) effect on pathogen inactivation in FS compost. The 3TF piles exhibited shorter pathogen inactivation periods (8 weeks) than 7TF and 14TF piles (10 weeks). Temperature-time was found to be the major factor responsible for the survival of pathogens in FS composting piles, followed by indigenous microbial activities and toxic by-products (monitored as NH4+-N). Our study findings suggest that even at low composting temperatures, the high turning frequency can enhance pathogen inactivation. This is a significant finding for composting activities in some rural areas where suitable organic solid waste for co-composting with FS to attain the recommended high thermophilic conditions could be greatly lacking.

Recycling of Faecal Sludge: Nitrogen, Carbon and Organic Matter Transformation during Co-Composting of Faecal Sludge with Different Bulking Agents

This study investigated the effect of locally available bulking agents on the faecal sludge (FS) composting process and quality of the final FS compost. Dewatered FS was mixed with sawdust, coffee husk and brewery waste, and composted on a pilot scale. The evolution of physical and chemical characteristics of the composting materials was monitored weekly. Results indicate that bulking agents have a statistically significant effect (p < 0.0001) on the evolution of composting temperatures, pH, electrical conductivity, nitrogen forms, organic matter mineralisation, total organic carbon, maturity indices, quality of the final compost and composting periods during FS composting. Our results suggest reliable maturity indices for mature and stable FS compost. From the resource recovery perspective, this study suggests sawdust as a suitable bulking agent for co-composting with FS-as it significantly reduced the organic matter losses and nitrogen losses (to 2.2%), and improved the plant growth index, thus improving the agronomic values of the final compost as a soil conditioner. FS co-composting can be considered a sustainable and decentralised treatment option for FS and other organic wastes in the rural and peri-urban communities, especially, where there is a strong practice of reusing organic waste in agriculture.