Modeling of biological nitrification | |
| Author | Sharma, Keshab Raj |
| Call Number | AIT Thesis no. EV-98-16 |
| Subject(s) | Nitrification--Mathematical models Sewage--Purification--Nitrogen removal |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | A mathematical model incorporating diffusion limitations inside a spherical biofloc for nitrogen removal with aerobic nitrification and anoxic denitrification is developed. Relationships between carbonaceous oxidation, nitrification and denitrification reactions and mass transfer are taken into account. The model consists of a set of simultaneous mass balance equations for organic matter, dissolved oxygen and various nitrogen species. Monod kinetics is used to describe biochemical reactions taking place inside the biofloc. Numerical solution to the system of ordinary differential equations is obtained using computer simulation. Different cases with respect to bulk substrate penetration are identified and incorporated in the model. Under low bulk DO concentration both aerobic and anoxic zones are present due to diffusion limitations inside the biofloc, resulting simultaneous nitrification and denitrification. Effectiveness factors for nitrification and denitrification are evaluated separately. Significant effects of biofloc size, temperature and bulk DO concentration on effectiveness factor are observed. Biofloc size, bulk concentration of DO and COD, and temperature are found to have significant influence on nitrification and denitrification processes and hence ammonia and total nitrogen removal rates. Higher nitrogen removal rates were observed for smaller bioflocs under low bulk DO concentrations. Bioflocs size for which maximum nitrogen removal rates can be achieved under bulk DO concentration of about 1 mg/l is found to be about 100 to 125 µm. Use of the model in a batch process is illustrated through simulation. Need of continuous addition of carbon source for the accomplishment of simultaneous nitrification and denitrification is realized. Proper control of bulk conditions such as DO and COD is found to enhance rate of nitrogen removal in a biological process employing biological floes. |
| Year | 1998 |
| 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) | Annachhatre, Ajit P. |
| Examination Committee(s) | Dahl-Madsen, Karl Iver ; Kim Oanh, N. T. |
| Scholarship Donor(s) | World Health Organization, Asian Institute of Technology |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1998 |