| Author | Yuttachai Sarathai |
| Call Number | AIT Diss. no.EV-10-07 |
| Subject(s) | Sewage--Purification--Anaerobic treatment
|
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctorof Technical Science inEnvironmental Engineeringand Management |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. EV-10-07 |
| Abstract | Ecentralized approachbecomesa promising alternativefordomestic wastewater management inunseweredcities and developing countries. Anaerobic Baffled Reactor (ABR) and vermicomposting process are regarded as decentralized treatment options.It isa challenge to determine the stability and reliability of ABR at various hydraulic and organic fluctuationswhich is important. For vermicomposting process, performance in treating accumulated sludge from ABR should be determined as well.For ABR studies, flow patterns werecategorized into steady flow and non-steady flow conditions, governed by peak flow factor (PFF). PFF is defined as a ratio of peak to average flow, for which a steady flow (or PFF=1) is equal to an average flow while non-steady flow are varied at PFF of 2, 4 and 6.Hydraulic retention time (HRT) was varied between 24-48 hrs,based on 24-h average flow. ABR operated at 48-h HRT could be recommended because this HRT results in minimal the effects of different flow patternson the mixing patterns and achievesthe higher hydraulic efficiency. However, dead space of ABR system depends on flow pattern, likely independent of given HRTs. Dead spaces did not exceed 13% atPFF of 1, 2, and 4whereas at the PFF of 6 itwould increase twofold (23-28%).In addition, superficial gas velocities in the range of 0.6 to 3.1 cm/hdid not cause (biological)dead space and not significantly affect the mixing pattern.The tank-in-series (TIS) model (N=4) could well explain thehydraulic model of ABR system.In term of treatment performance, it was investigated by feeding synthetic and household wastewaters.Influent COD concentrations ranged from 481 to1,416 mg/L, corresponding to organic loading rates(OLR) of 0.24-0.71 kgCOD/m3-d. Influent total suspended solids (TSS) concentration ofhousehold wastewater was 568 mg/L, while no suspended matters in syntheticwastewater. ABR units were operated at 48-h HRT.Start-up period of ABR requiredabout 90 day. For steady flow condition, ABR units could achieve COD and TSS removals at greater than 90% and 95%, respectively. IncomeCOD could be converted to methane gas at54-60%. 95.4% of TSS was accumulated in ABR,most of which88.7% of TSS were accumulated in a settling chamber.Fornon-steady flow conditions, COD removal efficiencies of ABR units wasaffectedonly atPFFof 6 but apparently affect TSS removal efficiencies atPFF of 4 and 6. By compartment-wise variation, 90% of income COD was removed within first two upflow chambers and more than 85% of TSS was removed in asettling chamber and likelytrapped within sludge blanket. pH was increased and volatile fatty acids (VFA)concentration decreased longitudinally down the reactor, indicating acidogenesis and acetogenesis.At non-steady flow (PFF=2 to 6), VFA were accumulated and metabolized during no peak flow hours (NPFH), confirmed by Methanosaetaand Methanosarcinagroups in upflow chambers andindicatingmethanogenesis in ABR unit.Reliability analysisfound that the effluent COD and TSS concentrations from ABR operatedat 48-h HRT under any flow patterns were 83 and 47 mg/L at reliability level of 95%.Mathematical model ofABR units combined a complete-mix reactor with first order reaction could be used to determine ABR treatment performance.For vermicomposting process, Eisenia fetida could be employed in treatingaccumulated sludge underoperating conditionsas follows: (i) initial moisture content of accumulated sludge of 90%, (ii) Stock density of 0.8 kg worm/m2and (iii) Feeding rate of 1 kg-wet weight of sludge/kg of worm-d.The average volatile suspended solids (VSS)removal by vermicomposting process was40% and moisture content in sludge vermicompost was66%. The quality of sludge vermicompost is comparable to a compost guidance byUS EPA. |
| Year | 2010 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. EV-10-07 |
| Type | Dissertation |
| 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 (EV) |
| Chairperson(s) | Thammarat Koottatep |
| Examination Committee(s) | Annachhatre, Ajit ;Aramaki, Toshiya ;Vilas Nitivattananon |
| Scholarship Donor(s) | Royal Thai Government Fellowship ;SwissNational Centre of Competence in Research (NCCR) North-South Program |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2010 |