Investigation of the treatment performance of up-flow thermophilic septic tank for treatment of blackwater | |
| Author | Pimchanok Prapasriket |
| Call Number | AIT Thesis no.EV-18-23 |
| Subject(s) | Septic tanks Wastewater--Treatment Water--Purification--Biological treatment |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Abstract | There are many countries in the world especially in developing country using the septic tanks for treatment of toilet or blackwater from their households. However, most of the septic tanks are not functioning properly which result from inappropriate design and maintenance, leading to the harmful pollutants of the effluent. According to Koottatep et al. (2014), the effluent of septic tank still appeared the high concentrations of TCOD, BOD5and TSS when compared with the discharged standards of Thailand which are 120, 30and40mg/L, respectively. To improve treatment performance of septic tanks, an innovative design of the septic tank is suggested. This study combines an up-flow hydraulics with solar septic tank for the treatment of black water, called as “Up-Flow Thermophilic Septic Tank” (UTST). The UTST which is thermophilically operated at a temperature of 50°C can improve the treatment efficiency by enhancing the contact between the blackwater and the sludge and promoting the growth of thermophilic microorganisms to degrade organic matters. This study aimed to investigate the performance of UTST treating blackwater and the effects of HRTs on COD and BOD5removal efficiencies and biogas production. The experiments were conducted with a laboratory-scale UTST(27L in size)by feeding with blackwater obtained from toilets of an academic building. The laboratory-scale UTST was operated at the HRTs of 8, 16, 24 and 32 h with continuous feeding for4months. Average COD removal efficiencies of the laboratory-scale UTST operating at 8, 16, 24 and 32 h at the temperature of 50oC were 53, 67, 77 and 75%, respectively. The effluent BOD5concentrations of the laboratory-scale UTST were in the same identical range of about 190-300 mg/L. The result showed that the UTST operating at HRT of 24 h could remove COD and BOD5better than those unit operating at 8, 16 and 32 h. However, there were no significant differences(p>0.05) of COD and BOD5treatment efficiencies between 24 and 32h HRTs operation, hence HRT of 24h is selected to be optimum due to less reactor size consideration. The average CH4yield production by the laboratory-scale UTST at 50oCoperating at HRT of 24 h were found to be 0.04 L/gCODin, consist mainly of methane 79.1%. The intermittent feeding mode was conducted with HRT of 24h to compare the treatment performance of different mode feeding. The experimental results showed that intermittent feeding mode could remove COD and BOD5better than continuous feeding. Average COD and BOD5 removal efficiencies of intermittent feeding at 24h HRT were 87 and 79, respectively with significant differences(p<0.05). In addition, the hydraulic condition in the UTST at optimum HRT of 24hwas studied. NaCl was used as a tracer chemical with a single shot impulse. The normalized resident time distribution (RTD) curves resulting from the results of tracer study indicated that the dispersion numbers of continuous and intermittent feeding were 0.203 and 0.326, respectively indicating the reactors approaching the completed-mix pattern. The kinetic model of the UTST was indicated to the first order kinetic with completely-mixed model. The reaction constants of the UTST for TCOD and BOD5removal efficiencies were1.952and 2.456which had correlation coefficient (R2) to be 0.871and 0.819. The model of UTST was validated with the literature data of the septic tank and up-flow septic tank for treating wastewater and blackwater that fitted well as the correlation coefficient (R2) to be0.8751and 0.763 for TCOD and BOD5removal efficiencies. |
| Year | 2018 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Thammarat Koottatep; |
| Examination Committee(s) | Annachhatre, Ajit P.;Chongrak Polprasert;Tatchai Pussayanavin; |
| Scholarship Donor(s) | Loom Nam Khong Pijai (Greater Mekong Subregion) Scholarships; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2018 |