Solar Septic Tank: Next Generation Sequencing Reveals Effluent Microbial Community Composition as a Useful Index of System Performance

Abstract

Septic tanks are widely deployed for off-grid sewage management but are typified by poor treatment performance, discharge of polluting effluents and the requirement for frequent de-sludging. The Solar Septic Tank (SST) is a novel septic tank design that uses passive heat from the sun to raise in-tank temperatures and improves solids degradation, resulting in a cleaner effluent. Treatment has been shown to exceed conventional systems, however, the underlying biology driving treatment in the system is poorly understood. We used next generation sequencing (Illumina Miseq (San Diego, CA, USA), V4 region 16S DNA) to monitor the microbiology in the sludge and effluent of two mature systems, a conventional septic tank and an SST, during four months of routine operation in Bangkok, Thailand, and evaluated the ecology against a suite of operating and performance data collected during the same time period. Significant differences were observed between the microbiome of the sludge and effluent in each system and the dominant taxa in each appeared persistent over time. Furthermore, variation in the microbial community composition in the system effluents correlated with effluent water quality and treatment performance parameters, including the removal of chemical and biochemical oxygen demand and the concentration of fecal and total coliforms in the effluent. Thus, we propose that a wide-scale survey of the biology underlying decentralised biotechnologies for sewage treatment such as the SST could be conducted by sampling system effluent rather than sampling sludge. This is advantageous as accessing sludge during sampling is both hazardous and potentially disruptive to the anaerobic methanogenic consortia underlying treatment in the systems.

Effect of sponge Density on septic tank effluent quality for dairy wastewater treatment

“…The figure (7) shows that filtration action give the highest removal ratio 64.80 % which is higher than COD removal ratio of septic tank by 21.93%.…”

Technologies for pollutant removal and resource recovery from blackwater: a review

“…5). With the stricter discharging requirements and the development of anaerobic technologies, enhancement and modification have been performed on septic tanks, including upflow operation to improve the contact between anaerobic sludge and wastewater (Luostarinen and Rintala, 2005;Luostarinen and Rintala, 2007;Al-Jamal and Mahmoud, 2009;Santiago-Díaz et al, 2019); membrane module introduction for effective rejection of suspended solids and associated particulate organic matter (Khalid et al, 2017); four-chamber septic tank with orifice plate and filter (Singh et al, 2019); combination with microbial electrolysis cell (MEC) to enhance biogas production and reduce the discharge of phosphorus and H 2 S (Zamalloa et al, 2013); and solar energy-assisted septic tank to raise the in-tank temperature and promote solids degradation (Connelly et al, 2019).…”

Development of Vertical Garden Constructed Wetlands (VGCWs) for Treating Septic Tank Effluent

“…in urban and rural areas for treatment of black and grey water from households (Koottatep et al, 2019). However, due to short hydraulic retention times (HRTs) and uctuating organic loading rates (OLRs), e uent of septic tanks usually contains high concentrations of organic and nutrients such as chemical oxygen demand (COD), total phosphorus (TP) and nitrogen, which negatively affect the environment (Connelly et al, 2019 andKoottatep et al, 2014). Therefore, posttreatment of septic tank e uent should be required to improve the water quality before disposal.…”