Effects of temperature on pathogen inactivation in an thermophilic septic tank | |
| Author | Sarunnoud Phuphisith |
| Call Number | AIT Thesis no.EV-13-24 |
| Subject(s) | Pathogenic bacteria--Inactivation Pathogenic microorganisms Septic tanks |
| 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 |
| Series Statement | Thesis ; no. EV-13-24 |
| Abstract | Thermal application has been widely and popularly used in term of pathogen inactivation in various fields of studies. Aimed to that purpose, application of thermal treatment on the conventional septic tank was initially studied in this study through small-scale batch experiments treating septic tank fecal sludge of Pathum Thani province, Thailand. To understand effects of temperature on excreted pathogens behaviors, total coliform, fecal coliform and Escherichia coli were selected and used as a fecal surrogate. Batch experiments were done in septum bottles and water bath was used as an energy source. Degrees of temperature applied ranged in mesophilic to thermophilic conditions (32, 40, 50, 60 and 70°C). The results revealed that the removal rates of fecal indicators increased with elevated temperatures. At thermophilic temperatures, pathogen removals in septic tank fecal sludge were strongly affected by a factor of thermal mechanism while under mesophilic ranges, those removals were functioned of thermal effect and many variances in fecal sludge together, i.e., substrate limitation, microbial competition, etc. The temperature effects on total coliform removal showed relatively less in numbers than on fecal coliform, however; effects of temperature on fecal coliform removal were similar toon E. coli. This indicated that fecal coliform group including E. coli has more vulnerable to thermal treatment than other thermotolerant species in total coliform group. Over four days incubation, total coliform (presumptive) was removed about 0.7, 1.5 and 1.5 log reductions at 32, 40 and 50°C, respectively and for one day incubation, total coliform was removed about 1.3 and 2.4 log reduction at 60 and 70°C, respectively. As the same incubating periods, fecal coli form removals showed around 1.8, 3.5, 3.5, 4.2 and 6 log reductions at 32, 40, 50, 60 and 70°C, respectively. As well as E. coli removals were detected approximately 2, 3.5, 3.5, 6, and 6 log reductions at 32, 40, 50, 60 and 70°C, respectively. The relationship between E. coli survivors and time treatment over temperatures studied were evaluated and the results were more suitable to be described as a nonlinear correlation (Weibull model) than a linear line(First-order kinetics) at all studied temperatures regarding to regression coefficient values (R2). Moreover, relating to Arrhenius relationship, the average k20 of E. coli in fecal sludge was 0.03 h-1 as well as the average b20 which modified from Weibull parameter, b, was 0.22. Apart from that, thermal treatment on lab-scale septic tanks was also preliminarily studied as a batch operation treating fecal sludge of Pathum Thani province, Thailand. COD, BOD, TSS, VSS and fecal indicators were studied over 42 days operation. Additionally, removals of fecal indicators in lab-scale septic tank were validated by both first-order and Weibull models. Care should be taken for using this study’s models to real septic tank application, for instance; effects of tank volume’s scale-up as well as continuous-feeding function were carefully considered. Other parameters of septic tank fecal sludge which could be affected by thermal treatment such as volatile fatty acid, ammonia, methane, helminth egg, etc. also needed for further studies. |
| Year | 2013 |
| 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 (EV) |
| Chairperson(s) | Thammarat Koottatep |
| Examination Committee(s) | Chongrak Polprasert;Annachhatre, Ajit P. |
| Scholarship Donor(s) | Royal Thai Government Fellowship |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2013 |