An integrated model for organic and nutrient removal by duckweeds-based wastewater treatment system (DUBWAT) | |
| Author | Krishna, K. C. Bal |
| Call Number | AIT Thesis no.EV-07-2 |
| Subject(s) | Duckweeds Sewage disposal plants |
| Note | A thesis submitted in paiiial 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-07-2 |
| Abstract | This study was conducted to develop an integrated kinetic model for organic and nutrient removal by duckweeds-based wastewater treatment systems that incorporate the key operating parameter such as hydraulic retention time (HRT), organic loading rate (OLR) and stocking density (SD). Four pilot-scale duckweeds-based wastewater treatment (DUBWAT) units planted with duckweeds (Lenina gibba) were set up and optimum key operating parameters such as HRT, OLR and SD were also determined. The effects of HRT on organic and nutrient removal were studied by varying the HRTs of 1, 5, 10 and 15 clays, while the OLR-and SD were maintained at 50 kgCOD/(ha.day) and 0.5 kg/m2, respectively. The unit operating with HRT of 15 days gave the highest COD, BOD5, NH3-N, TN and TSS removal efficiencies of 86, 87, 64, 51 and 90%, respectively. Based on the paired t-test at 95% confidence level, the mean COD, BOD5, NH3-N, TN and TSS removal efficiencies were not significantly different between units operating at HRT of 10 and 15 days. Therefore, the HRT of 10 days was considered the optimum HRT. The effects of OLR were studied by varying the OLR at 50, 75, 100 and 150 kgCOD/(ha.day), while the HRT and SD were maintained at 10 days and 0.5 kg/m2, respectively. The highest COD, BOD5, NH3-N, TN and TSS removal efficiencies of 85, 88, 63, 49 and 89 % were found in the unit maintaining the OLR of 50 kgCOD/(ha.day). Similarly, the effects of SD were studied by varying the SD at 0.3, 0.5, 0.9 and 1.2 kg/m2, respectively. The unit operating with SD of 0.5 kg/m2 gave the maximum COD, BOD5, NH3-N, TN and TSS removal efficiencies of 84, 87, 67, 58 and 86%, respectively. An integrated model to predict treatment performance of the DUBWAT system was developed which incorporated such important parameters as: HRT, OLR and SD. The model coefficients were determined from the experimental data by using SPSS 11.5 program. The models were validated with the literature data obtained from pilot-scale DUBWAT unit treating domestic and synthetic wastewaters. The predicted COD, BOD5, NH3-N and TN values were found in close agreement with observed effluent values, indicating the applicability of proposed model in DUBWAT systems design. The RGR value of duckweeds was found to be 0.32 day-1 with an average production rate of 62 kg dw/(ha.day) in the unit operating at SD of 0.5 kg/m2. N uptake rate by duckweeds was found to be 0.62 g-N/(m2.day). |
| Year | 2007 |
| Corresponding Series Added Entry | Asian Institute of Technology.|tThesis ;|vno. EV-07-2 |
| 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) | Chongrak Polprasert; |
| Examination Committee(s) | Ajit P. Annachhatre;Thammarat Koottatep; |
| Scholarship Donor(s) | FRANCE;AIT Fellowship; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2007. |