| Author | Jenyuk Lohwacharin |
| Call Number | AIT Thesis no.EV-05-12 |
| Note | A thesis submitted in partial fulfillment of the requirements for the
degree of Master of Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Performance of an airlift reactor for biological sulphide removal process employing obligate chemolithotrophs was investigated for 155 days under ambient temperature. The experimental setup was consisted of feed tank, 5-1 airlift reactor, and settling tank for removal of biologically-produced sulphur. The airlift reactor was equipped with a draft tube through which air was sparged continuously for maintaining DO level in the range 0.2-1.0 mg/l as well as to generate airlift condition in the reactor. The reactor was also equipped with pH controller to maintain pH in the range 7.8-8.0. Effluent recirculation was employed whenever necessary in order to maintain oxygen-limited condition in the reactor. Deoxygenating with N2 gas was conducted to obtain low dissolved oxygen in the feed and nutrient tanks. At volumetric sulphide loading rate lower than 2.18 kgS/m3 -day, maintaining oxygenlimited condition was critical in optimizing elemental sulphur production. This was achieved by partial recirculation of the effluent to maintain dissolved oxygen below 0.2 mg/l. 50% of influent sulphide was converted to elemental sulphur. Beyond the loading rate of 2.18 kgS/m3 -day and DO concentration below 1.0 mg/l, elemental sulphur production gradually increased. The result implies that volumetric sulphide loading rate is the significant operational parameter under high influent-sulphide concentration. The airlift bioreactor was operated at the maximum volumetric sulphide loading rate of 4.0 kgS/m3 -day yielding the maximum sulphide consumption rate of 4.3 kgS/kgVSS-day and over 93 %-sulphide removal. 90% of sulphide removed was converted into elemental sulphur which was separated in settling tank as sulphur sludge with 40 percent sulphur content by weight. Addition of the selected coagulant, Polyaluminium chloride, was found to be effective for sulphur-particle aggregation. Optimal coagulant dose was found to be 0.71 g/l at pH 7.5 and a temperature of 30°C. Morphological examination of biomass suspension in the reactor by Scanning Electron Microscopy (SEM) showed that elemental sulphur was excreted on the bacterial surface and deposited extracellularly. |
| Year | 2005 |
| 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) | Annachhatre, Ajit P.; |
| Examination Committee(s) | Visvanathan, C.;Preeda Parkpian; |
| Scholarship Donor(s) | Royal Thai Government Fellowships ; |
| Degree | Thesis (M. Eng.) -- Asian Institute of Technology, 2005 |