Septic Tank Research Articles

From a Wretched Past to an Uncertain and Undignified Future: The Open Secret of Manual Scavenging in India

India promises liberty, equality, justice and fraternity with dignity of life through the Constitution to every citizen without any discrimination. However, a particular section of society has been deprived of these promises due to their birth, gender and occupation. This section happens to be part of the generically termed ‘Dalits’ who are the lowest of the lower castes among the Hindus. They are known as manual scavengers who carry human excreta and clean dry latrines, sewers, and septic tanks more often with bare hands. This practice of manual scavenging is involuntary in nature. The scavengers not only suffer from extreme forms of social exclusion but also gross violations of human rights and dignity. However, ironically, despite several efforts as well as denial of its existence by the government, this inhuman practice still continues to exist in India. In fact, it has given birth to a new subtle form of untouchability which is an anathema to the constitutional promise. Therefore, the main aim of this article is an investigation of the nexus between caste and occupation. This article, in fact, suggests that for the annihilation of this practice, there is the need for an inclusive approach and overall behavioural change.

A Localized GIS-Based Multi Decision Criteria Approach in Determining Suitable Sites for Community Toilet Facilities in BASECO Compound, Manila City

Abstract. Access to sanitation remains a major concern in the Philippines due to the increasing population and growing demand for basic needs. This study addresses poor sanitary conditions in slum areas, specifically in BaSECo Compound, Manila, where informal settlers rely on shared toilets. Utilizing GIS and MCDA, the study identifies areas suitable for community toilet facility (CTF) development. The Modified Huff Three-Step Floating Catchment Area (MH3SFCA) method quantified spatial accessibility to existing toilets. The SPAI map shows low accessibility in blocks 15 and New Site, with Gawad Kalinga, Habitat, and Old Site (N) having none. The Analytical Hierarchy Process (AHP) prioritized six criteria, with accessibility being the most significant (33.18%), followed by proximity to water supply (31.76%), communal septic tanks (14.53%), land use (8.2%), flood-prone areas (7.44%), and ground slope (4.89%). The final suitability map identified 14.12% of the 0.6 sq. km. area as highly suitable, including Block 15, Gawad Kalinga, Habitat, and Old Site (N). Ground truth verification visited five candidate sites, which were tested for improved SPAI maps. The inclusion of facilities in Block 15, GK 2, OSN, and H improved accessibility in northern BaSECo. Significant service area improvements for each CTF were observed using Voronoi polygons. This study demonstrates the effectiveness of integrating GIS and MCDA methods for CTF site selection.

Surface water quality in Costa Rica: new initiatives and challenges

ABSTRACT Despite Costa Rica's reputation for being a leader in environmental policy and its thriving nature-based tourism industry, the nation has had poor surface water quality. Reasons for poor water quality include the lack of sewerage treatment, overuse of septic tanks, and the application of large quantities of agrichemicals. Although Costa Rica has policies to maintain surface water quality, they have not been sufficiently implemented. Recent initiatives have addressed surface water quality, including an ambitious plan to expand treated sewerage systems in all urban areas. Current efforts to meet this goal have focused on the San Jose metropolitan area and coastal communities. This paper reviews the advances and challenges to Costa Rica's efforts to improve water quality.

Performance of a pilot-scale microbial electrolysis cell coupled with biofilm-based reactor for household wastewater treatment: simultaneous pollutant removal and hydrogen production.

The septic tank is the most commonly used decentralized wastewater treatment systems for household wastewater treatment in on-site applications. The removal rate of various pollutants is lower in different septic tank configurations. The integration of a microbial electrolysis cells (MEC) into septic tank or biofilm-based reactors can be a green and sustainable technology for household wastewater treatment and energy production. In this study, a 50-L septic tank was converted into a 50-L MEC coupled with biofilm-based reactor for simultaneous household wastewater treatment and hydrogen production. The biofilm-based reactor was integrated by an anaerobic packed-bed biofilm reactor (APBBR) and an aerobic moving bed biofilm reactor (aeMBBR). The MEC/APBBR/aeMBBR was evaluated at different organic loading rates (OLRs) by applying voltage of 0.7 and 1.0V. Result showed that the increase of OLRs from 0.2 to 0.44kg COD/m3 d did not affect organic matter removals. Nutrient and solids removal decreased with increasing OLR up to 0.44kg COD/m3 d. Global removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN), ammoniacal nitrogen (NH4+), total phosphorus (TP) and total suspended solids (TSS) removal ranged from 81 to 84%, 84 to 85%, 53 to 68%, 88 to 98%, 11 to 30% and 76 to 88% respectively, was obtained in this study. The current density generated in the MEC from 0 to 0.41 A/m2 contributed to an increase in hydrogen production and pollutants removal. The maximum volumetric hydrogen production rate obtained in the MEC was 0.007 L/L.d (0.072 L/d). The integration of the MEC into biofilm-based reactors applying a voltage of 1.0V generated different bioelectrochemical nitrogen and phosphorus transformations within the MEC, allowing a simultaneous denitrification-nitrification process with phosphorus removal.

Rural-urban disparities in basic sanitation access among households: a multivariable decomposition analysis of Ethiopian demographic and health survey 2019

IntroductionDisparities in access to basic sanitation services between rural and urban households pose significant challenges to public health and human development. Understanding the determinants contributing to this gap is vital for advancing the Sustainable Development Goals (SDGs) and improving environmental and public health through evidence-based interventions.ObjectiveThis study aims to analyze and understand the disparities in access to basic sanitation services between rural and urban households in Ethiopia.MethodsThis study analyzed a sample of 8,663 weighted households, collected using stratified sampling techniques, utilizing the data from the 2019 Ethiopian Demographic and Health Survey (EDHS). The primary outcome was basic sanitation access, defined as access to flush or pour-flush systems, septic tanks, pit latrines, or composting toilets. A multivariable decomposition analysis was conducted to identify factors contributing to rural–urban disparities. Statistically significant variables were determined at a p-value of <0.05 with a 95% confidence interval.ResultsThe weighted proportion of basic sanitation access in Ethiopia was 13.78% (95% CI, 12.67–14.96), with significant disparities between rural (6.02%) and urban (27.15%) residents. Endowment factors accounted for 78.9% of this disparity, while behavioral coefficients contributed 22.1%. If the characteristics of respondents in rural and urban households had been similar, significant factors that would have narrowed the gap included the age of the household head (15–35 years), the absence of under-five children, smaller family size, and the attainment of secondary education, reducing the gap by 1.83, 2.07, 5.08, and 3.25%, respectively. Conversely, illiteracy and primary education levels widened the gap between rural and urban access to basic sanitation services by 16.85 and 0.23%, respectively. Additional factors exacerbating the rural–urban disparity included poverty (which widened the gap by 58.71%), residence in pastoralist regions (which widened the gap by 10.10%) or agrarian regions (which widened the gap by 7.03%), and access to water sources located more than 30 min away (which widened the gap by 7.91%).ConclusionSignificant disparities in access to basic sanitation services exist between rural and urban households in Ethiopia. Key factors contributing to these disparities include the age of the household head, education level, family size, region of residence, and water source proximity. Addressing these factors is essential for improving sanitation access and achieving the Sustainable Development Goals (SDGs).

Effluents from septic systems and impact on groundwater contamination: a systematic review.

Globally, 2.2 billion people rely on groundwater for their water supply, and 2.8 billion use onsite sanitation systems for their sanitation needs. Groundwater contamination from septic systems is a critical public health concern, linked with diseases related to water sanitation and hygiene. Despite the severe impacts of septic systems on groundwater quality, comprehensive global studies remain limited. This study conducted a systematic review of articles published between 2012 and 2023 on topics related to septic systems and groundwater contamination, and 82 peer-reviewed articles met the inclusion criteria. The review identified key contaminants, including E.coli, nitrate, Enterococcus spp., total coliform, ammonium, phosphate, chlorides, and pharmaceuticals. Research on microbial indicators is more prevalent in Africa, while research on nutrients is common in North America. Research on organic contaminants including polyfluoroalkyl substances (PFAS), pharmaceuticals, and personal care products (PCPPs) is limited, particularly in low-and middle-income countries. Critical factors contributing to groundwater contamination include soil, hydrogeological conditions, climate, septic system maintenance and functioning, and septic density. The goal of this study was to comprehensively assess the extent of groundwater contamination resulting from septic system effluents by identifying the major contaminants typically found in affected groundwater sources and exploring the factors contributing to contamination. Identifying the major contaminants and factors related to groundwater contamination from septic systems is crucial for developing effective management strategies to protect groundwater sources.

Effectiveness and Risk Assessment of Septic Tank Treatment Systems in Rural Cold Regions of China

Rural toilet reform in cold areas is the focus and difficulty of China’s toilet revolution. In this paper, by carrying out the septic tank gradient burial depth test and regular seasonal monitoring of the operation effect of rural septic tanks in cold areas, the frost protection effect and treatment effect of rural toilets in cold areas are clarified, which provide important references for the rural toilet revolution and its practical significance in cold areas of China. Based on controlled tests and correlation analysis methods, different gradient burial depths of septic tanks (40, 60, and 80 cm) and different seasonal operation effects (spring, summer, autumn, and winter) were studied to analyze the influence of factors such as burial depths and temperatures on the effectiveness of anti-freezing and treatment of septic tanks. The results found that the septic tank effluent indexes of the six cold-zone test households could not meet requirements of Class Ⅰ-B in the discharge standard of pollutants for municipal wastewater treatment plants (GB 18918-2002). (The criteria for Class I-B are as follows: COD emission limit of 60 mg/L; SS emission limit of 20 mg/L; TN emission limit of 20 mg/L; TP emission limit of 1 mg/L; NH3-N emission limit of 8 mg/L); The average removal of suspended solids (SSs), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), NH3-N, and NO3-N by septic tanks was 79.7%, 21.8%, 10.5%, 13.5%, 9.76%, and 2.38%, respectively; the water temperature was significantly positively correlated with SS, TN, and TP; the double-layer insulated septic tank with medium burial depth (60 cm) could operate normally in cold areas in winter. The treatment effect of septic tanks on various indicators basically shows that summer > autumn > spring > winter. Temperature is the main limiting factor affecting the treatment effect of septic tanks.

Ethical and Legal Protection of Drinking Water Resources in Islamic Jurisprudence (with Emphasis on Drinking Water Resources in Kabul)

Water is a vital resource for all living beings. The increase in population and decrease in rainfall in many cities around the world have led to serious water scarcity and pollution of wells and water resources in countries. The expansion of industrial production has resulted in the release of pollutants into surface and groundwater in cities and farmlands of countries. Therefore, this research has been conducted in a library way to examine the views and solutions of Islamic jurisprudence on resolving the problems and preserving the health of drinking water resources and wells, especially in Kabul. The findings of this research are that to preserve the health of water resources, a legal or spatial boundary between neighboring wells or farmers is required to be 500 meters in soft land, but in hard land, at least 250 meters between them is necessary to prevent the resulting damages. However, the distance between a well and a septic tank is 2.5 meters in hard land, and at least 7 cubits or 3.5 meters in soft areas. This is to purify water pollutants and prevent the resulting damages to neighbors. The legal boundary approach has been stated to compensate for the damage caused by a well or a water canal. Moral boundary means the growth of human responsibility to prevent water and environmental pollution in Islamic jurisprudence. Natural pollutant filters for well and canal water are the elements of soil, sand, abundant or flowing water, and oxygen present in water in Islamic jurisprudence.

Hydrochemical Characterisation of the Basement Aquifer with a Focus on the Origin of Nitrate in the Highly Urbanised Niamey Region, SW of Niger

This study investigated the basement aquifer beneath the urbanised city of Niamey and the agricultural fields of Kollo, SW of Niger. During the observation period spanning from 2021 to 2023, groundwater and surface water samples were collected for analysis of major ions and the stable isotopes oxygen-18 and deuterium (δ18O and δ2H) of water. To trace the origin of high nitrate concentrations (NO3−) found in several observation and drinking water wells in both areas, δ15N and δ18O isotope values of NO3− were analysed in groundwater and eluted soil samples. The observed hydrochemical patterns mainly reflect the heterogeneity of the weathered fringe of the basement aquifer. Decreasing concentrations of NO3− and δ18O and δ2H values were observed in relation to the distance of the Niger River and increasing thickness of the clay layer on the surface. The wells close to the river in Niamey show a dilution effect during the flood season, and the NO3− concentrations displayed a continuous increasing trend. The δ15N-NO3 and δ18O-NO3 values confirmed that septic tank water is spreading in the region of Niamey and that manure originating from livestock in Kollo is the main source of NO3−. The patterns of δ15N in the soil samples coincide with those of cattle’s manure spread in both areas. The shallow wells show significantly higher values of electric conductivity and NO3− concentrations compared to the deeper wells, which clearly indicates the influence of shallow septic tanks on water quality.

Septic systems in North Carolina: A neglected half of the state?

Septic systems in North Carolina: A neglected half of the state?

Breaking the chains of discrimination: an assessment of India’s legal framework and rehabilitation initiatives for manual scavengers

ABSTRACT Tragically, between March and April of 2023, during a period lasting just one month, eight individuals perished while undertaking one of society’s most hazardous jobs: cleaning sewers. These fatalities have resurrected anxieties regarding the persisting deaths among manual scavengers despite explicit legal prohibitions against such practices nationwide. Despite legal efforts against it, news reports reveal that this harmful practice continues across India. The dangers are real for those who work in septic tanks or sewage systems, with incidents frequently cited where death results from accidental asphyxiation. Through a comprehensive analysis of social and legal factors at play for manual scavengers, this research looks into how far the laws and government schemes have successfully improved the condition of manual scavengers. It explores recent court cases alongside legal developments to determine efficacy while highlighting challenges faced in the implementation stages of relevant laws. By considering cultural perspectives and these factors, it becomes clear that pervasive stigmatization has severe psychological consequences for those working as manual scavengers within India’s caste system today. This research highlights how this scenario affects those who scavenge as they deal with being socially excluded while enduring economic exploitation and denying their fundamental human rights and dignity. Furthermore, it examines current rehabilitation plans by analyzing their efficacy and what hinders implementation through social empowerment initiatives for these individuals who manually scavenge human waste.

Characterizing the Areal Extent of PFAS Contamination in Fish Species Downgradient of AFFF Source Zones.

Most monitoring programs next to large per- and polyfluoroalkyl substances (PFAS) sources focus on drinking water contamination near source zones. However, less is understood about how these sources affect downgradient hydrological systems and food webs. Here, we report paired PFAS measurements in water, sediment, and aquatic biota along a hydrological gradient away from source zones contaminated by the use of legacy aqueous film-forming foam (AFFF) manufactured using electrochemical fluorination. Clustering analysis indicates that the PFAS composition characteristic of AFFF is detectable in water and fishes >8 km from the source. Concentrations of 38 targeted PFAS and extractable organofluorine (EOF) decreased in fishes downgradient of the AFFF-contaminated source zones. However, PFAS concentrations remained above consumption limits at all locations within the affected watershed. Perfluoroalkyl sulfonamide precursors accounted for approximately half of targeted PFAS in fish tissues, which explain >90% of EOF across all sampling locations. Suspect screening analyses revealed the presence of a polyfluoroketone pharmaceutical in fish species, and a fluorinated agrochemical in water that likely does not accumulate in biological tissues, suggesting the presence of diffuse sources such as septic system and agrochemical inputs throughout the watershed in addition to AFFF contamination. Based on these results, monitoring programs that consider all hydrologically connected regions within watersheds affected by large PFAS sources would help ensure public health protection.

Geoenvironmental Effects of the Hydric Relationship Between the Del Sauce Wetland and the Laguna Verde Detritic Coastal Aquifer, Central Chile

In the central region of Chile, the Mega-Drought together with the demographic increase near the coast threatens groundwater availability and the hydrogeological functioning of coastal wetlands. To understand the hydric relationship between an aquifer and a wetland in a semi-arid coastal region of Central Chile (Valparaíso, Chile), as well as its geoenvironmental effects, four data collection campaigns were conducted in the wetland–estuary hydric system and surroundings, between 2021 and 2022, including physical, hydrochemical, and isotopic analyses in groundwater (n = 16 sites) and surface water (n = 8 sites). The results generated a conceptual model that indicates a hydraulic connection between the wetland and the aquifer, where the water use in one affects the availability in the other. With an average precipitation of 400 mm per year, the main recharge for both systems is rainwater. Three specific sources of pollution were identified from anthropic discharges that affect the water quality of the wetland and the estuary (flow from sanitary landfill, agricultural and livestock industry, and septic tank discharges in populated areas), exacerbated by the infiltration of seawater laterally and superficially through sandy sediments and the estuary, increasing salinity and electrical conductivity in the coastal zone (i.e., 3694 µS/cm). The Del Sauce subbasin faces strong hydric stress triggered by the poor conservation state of the riparian–coastal wetland and groundwater in the same area. This study provides a detailed understanding of hydrological interactions and serves as a model for understanding the possible effects on similar ecosystems, highlighting the need for integrated and appropriate environmental management.

Long-term spatiotemporal changes in nitrate contamination of municipal groundwater resources after sewerage network construction in the Hungarian Great Plain.

Over the last decades, as a consequence of wastewater discharges and other anthropogenic sources, severe nitrate (NO3-) pollution has developed in municipal environment causing global concern. Thus, eliminating the potential sources of pollution is one of the major challenges of the twenty-first century, whereby sanitation services are essential for ensuring public health and environmental protection. In the present study, long-term monitoring (2011-2022) of shallow groundwater NO3- contamination in municipal environment was carried following the construction of the sewerage network (2014) in the light of the pre-sewerage situation. Our primary aim was to assess the long-term effects of sewerage on nitrate NO3- levels in the shallow groundwater and evaluate the efficiency of these sanitation measures over time. Based on the results, significant pollution of the shallow groundwater in the municipality was identified. During the pre-sewer period, NO3- concentrations exceeded the 50mg/L limit in the majority of monitoring wells significantly, upper quartile values ranged between 341 and 623mg/L respectively. Using Nitrate Pollution Index (NPI) and interpolated NO3- pollution maps, marked spatial north-south differences were detected. In order to verify the presence of wastewater discharges in the monitoring wells, the isotopic ratio shifts (δ) for 18O and D(2H) were determined, confirming municipal wastewater effluent. Variations in NO3-/Cl- molar ratios suggest also contamination from anthropogenic sources, including septic tank effluent from households and the extensive use of manure. Data series of 7years (2015-2022) after the investment indicate marked positive changes by the appearance of decreasing trends in NO3- values confirmed by Wilcoxon signed rank test and ANOVA. By comparing the pre- and post-sewerage conditions, the mean NO3- value decreased from 289.7 to 175.6mg/L, with an increasing number of monitoring wells with concentrations below the limit. Our results emphasise the critical role of sanitation investments, while also indicating that the decontamination processes occur at a notably slow pace. Detailed, long-term monitoring is therefore essential to ensure accurate follow-up of the ongoing changes. The results can provide information for local citizens and authorities to improve groundwater management tools in the region.

Reducing wastewater nitrogen loading by >90% with carbon-amended septic systems: A field demonstration in Barnstable (Cape Cod), Massachusetts

Onsite wastewater treatment systems (OWTS) are a major source of excess nutrients and co-pollutants in watersheds across the United States. In Barnstable County (Cape Cod), Massachusetts, effluent from septic systems and cesspools contributes approximately 80% of the controllable reactive nitrogen (N) load to numerous impaired estuaries and degrades water quality in the region's sole source aquifer, streams and ponds. In unsewered areas, wastewater N loads could be reduced substantially by Innovative/Alternative (I/A) septic systems designed for enhanced removal. Use, however, has been partly limited by the availability of high performing, cost effective options, while conventional septic systems continue to be installed in watersheds with well documented N impairments. This paper describes the strategic replacement of residential OWTS with two I/A models that incorporate woodchip bioreactors to enhance N removal. Systems were installed at 14 neighboring homes in Barnstable, MA, and monitored for field performance. Influent and effluent were sampled monthly and analyzed for N and phosphorus (P), among other water quality indicators. Flow to each system was continuously metered to estimate nutrient loads. Results from the first 25 months of monitoring for 13 systems with at least a full year of data are presented in terms of 1) reductions in nutrient concentrations and mass loads and 2) reliability of the systems for meeting a performance goal of total N (TN) < 10 mg/L. Discussion supports consideration of where and how these technologies may be successfully used to manage excess N in sensitive watersheds.

How to Check and Maintain Your Septic System Before and Immediately After Hurricanes

The purpose of this guide is to provide tips for how to check, maintain, and use your septic system in the days leading up to a hurricane and immediately after any associ­ated flooding. This guide is intended for residents who have a residential septic system connected to their home. Written by Mary G. Lusk, and published by the UF/IFAS Department of Soil, Water, and Ecosystem Sciences, October 2024.

Planning decentralized wastewater treatment systems by comparing through TOPSIS

ABSTRACT This study evaluates 10 case studies of decentralized wastewater treatment systems (DEWATS) and compares them based on their environmental and economic performance. The aim is to identify the best treatment system composed of specific treatment processes that can be used in the future for hospitals, universities/colleges, and small communities. The comparison was conducted using the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS) method of multiple criteria decision-making. According to the TOPSIS method, systems are ranked from 1 to 10 by normalizing and weighting the decision matrix criteria, measuring the alternative's distance from the ideal best to worst value, and then calculating the performance score of each system. The study found that the H4 system, which includes a septic tank, anaerobic baffled reactor, anaerobic filter, horizontal filter, and pond, achieved the highest performance score. Therefore, the processes of the H4 system are recommended as the best alternative for DEWATS. This study may therefore assist stakeholders on their decision to implement DEWATS in similar facilities.

Effects of Polyethylene Terephthalate Microplastics on Anaerobic Mono-Digestion and Co-Digestion of Fecal Sludge from Septic Tank.

Anaerobic digestion (AD) is one of the most significant processes for treating fecal sludge. However, a substantial amount of microplastics (MPs) have been identified in septic tanks, and it remains unclear whether they impact the resource treatment of feces. To investigate this, polyethylene terephthalate (PET) was used as an indicator of MPs to study their effect on the anaerobic digestion of fecal sludge (FS). Two digestion systems were developed: FS mono-digestion and FS co-digestion with anaerobic granular sludge. The results indicated that the effects of PET varied between the two systems. PET inhibited volatile fatty acid synthesis in both systems, but the inhibition period differed. During mono-digestion, PET slightly increased gas and methane production, in contrast to the co-digestion system, where PET reduced methane production by 75.18%. Furthermore, in the mono-digestion system, PET increased soluble chemical oxygen demand and ammonia nitrogen concentrations while blocking phosphorus release, whereas the co-digestion system showed the opposite effects. Ultimately, the choice of digestion method is crucial for the resource utilization of septic tank sludge, and the impact of MPs on AD cannot be ignored.

Microbial source tracking and identification of fecal contamination patterns in saltwater estuaries between base- and storm-flow events using dual genome-based approaches

Fecal contamination from natural and anthropogenic sources poses significant threats to saltwater estuaries, particularly after storms or heavy rainfall. Monitoring fecal contamination is essential for protecting these vulnerable ecosystems having important ecological and economic values. In this study, we investigated the abundance, sources, and potential causes of fecal contamination at three marine and seven freshwater stations across Vaughn Bay (WA, USA), a shellfish growing district, during base- and storm-flow events. Additionally, we evaluated the performance of fecal indicator bacteria (FIB) quantification, optical brightener assessment, and qPCR analysis for fecal contamination quantification. We compared the effectiveness of qPCR-based microbial source tracking (MST), which targeted a broad range of hosts including, such as humans, birds, cows, horses, ruminants, dogs, and pigs, with sequencing-based MST in identifying fecal contamination sources. Both MST analysis approaches identified birds and humans as the primary sources of fecal contamination. For marine water stations, freshwater creeks VBU001, VBU002, and VB047, along with drain VB007, were identified as the main sources of human-derived fecal contamination in Vaughn Bay, based on Kendall's tau analysis (τ: 0.58–0.97). This information indicates that the septic systems in the catchment areas of these creeks and drains require further investigation to achieve effective fecal contamination control. Optical brightener, FIB enumeration and qPCR quantification results were generally higher during storm-flow events, although they showed poor correlation with each other (Pearson r < 0.40), likely due to physiological and phylogenetic differences among the target organisms of these methods. However, the sequencing-based method faces challenges in precise quantitative identification of differences in fecal contamination between base- and storm-flow events. Due to its high-throughput and cost-effectiveness, we recommend using sequencing-based analysis for large-scale identification of the primary sources of fecal contamination in water environments, followed by targeted qPCR quantification of MST markers for more precise assessments.

Wastewater-based surveillance for Hepatitis A virus, Enterovirus, Poliovirus, and SARS-CoV-2 in São Tomé and Príncipe: A pilot study

BackgroundWastewater-based surveillance is a valuable tool for monitoring pathogen transmission in communities, especially in regions where formal surveillance systems are limited. AimThe aim of this study was to implement and evaluate a wastewater-based monitoring system for viral pathogens in São Tomé and Príncipe. MethodsA total of 122 water samples were collected bi-weekly from June 2022 to July 2023 at six locations in São Tomé city and analysed for molecular detection of Hepatitis A Virus (HAV), Enterovirus (EV), Poliovirus (PV), SARS-CoV-2, as well as JC-Polyomavirus (JCPyV) and pepper mild mottle virus (PMMoV) as indicators of human contamination. Prevalence was analysed per pathogen and across sampling locations. Results for SARS-CoV-2 were assessed together with notifications from national COVID-19 surveillance. Further, we estimated resources needed to establish a wastewater-based approach to assess community-level transmission of viral pathogens. ResultsAll 122 and 117 samples were found positive for PMMoV and JCPyV, respectively, demonstrating a high level of human contamination at all sampling locations. The prevalence of HAV and EV ranged from 0 % to 59 % and 56 % respectively. Consistent with national surveillance data the highest proportion of SARS-CoV-2 positive water samples coincides with the highest number of COVID-19 cases reported during the study, demonstrating the potential of wastewater-based surveillance to identify signals. In addition, for SARS-CoV-2 this approach provided evidence of continuous circulation of the virus in the community, most importantly during weeks when no COVID-19 cases were reported. ConclusionOur findings provide evidence of high transmission of HAV and EV in communities in São Tomé and continuous circulation of SARS-CoV-2, even in weeks without COVID-19 case notifications. This study demonstrates that monitoring of viral pathogens in humanly impacted open water streams and sewage tanks is a valuable tool to complement clinical surveillance in resource-limited settings.