intI1 gene abundance from septic tanks in Thailand using validated intI1 primers.

IMPORTANCE: Antimicrobial resistance is a global crisis, and wastewater treatment, including septic tanks, remains an important source of antimicrobial resistance (AMR) genes. The role of septic tanks in disseminating class 1 integron, and by extension AMR genes, in Thailand, where antibiotic use is unregulated remains understudied. We aimed to monitor gene abundance as a proxy to infer potential AMR from septic tanks in Thailand. We evaluated published intI1 primers due to the lack of consensus on optimal Q-PCR primers and the absence of standardization. Our findings confirmed septic tanks are a source of class 1 integron to the environment. We highlighted the significance of intI1 primer choice, in the context of interpretation of risk associated with AMR spread from septic tanks. We recommend the validated set (F3-R3) for optimal intI1 quantification toward the goal of achieving standardization across studies.

Performance of novel constructed wetlands for treating solar septic tank effluent.

To improve treatment performance of the solar septic tank technology, novel constructed wetland systems have been proposed as an effective post-treatment system. This study aimed to investigate the treatment performance of the multi-soil layer based constructed wetland (MSL-CW) and comparing with the modified constructed wetland (mCW) for treating solar septic tank effluent in long-term operation. Pilot-scale MSL-CW and mCW units were operated in parallel under the same conditions during the period of 2016-2019. Removal efficiencies of TCOD, SCOD and TBOD in the MSL-CW were not significantly different (p < 0.05) from those of the mCW unit, which were 70-72%, 63-68% and 78-82%, respectively. The removal efficiencies of TSS, TKN, NH4-N and TP were found in the same magnitude in both units. The total coliform and E.coli counts in the effluent of MSL-CW and mCW units were reduced from 105 MPN/100 mL to be lower than 103 MPN/100 mL. These long-term operational results demonstrated that the effluent from the MSL-CW and mCW units could meet the global standards of non-sewered sanitation systems and the WHO guidelines. The effects of seasonal variations and plant harvesting on the monthly treatment performance are discussed in this study.

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).

Enhanced sludge reduction in septic tanks by increasing temperature.

Septic tanks in most developing countries are constructed without drainage trenches or leaching fields to treat toilet wastewater and /or grey water. Due to the short hydraulic retention time, effluents of these septic tanks are still highly polluted, and there is usually high accumulation of septic tank sludge or septage containing high levels of organics and pathogens that requires frequent desludging and subsequent treatment. This study aimed to reduce sludge accumulation in septic tanks by increasing temperatures of the septic tank content. An experimental study employing two laboratory-scale septic tanks fed with diluted septage and operating at temperatures of 40 and 30°C was conducted. At steady-state conditions, there were more methanogenic activities occurring in the sludge layer of the septic tank operating at the temperature of 40°C, resulting in less total volatile solids (TVS) or sludge accumulation and more methane (CH4) production than in the unit operating at 30°C. Molecular analysis found more abundance and diversity of methanogenic microorganisms in the septic tank sludge operating at 40°C than at 30°C. The reduced TVS accumulation in the 40°C septic tank would lengthen the period of septage removal, resulting in a cost-saving in desluging and septage treatment. Cost-benefit analysis of increasing temperatures in septic tanks was discussed.