| Author | Chanya Pokasoowan |
| Call Number | AIT Diss. no.EV-10-02 |
| Subject(s) | Sulphides--Oxidation
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| Note | A dissertation submitted in partial fulfillment of requirements for the degree of Doctor of Engineering in Environmental Engineering and Management, School of Environment, Resources, and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. EV-10-02 |
| Abstract | Sulfide-containing wastewater is generated by a number of industries and anaerobic treatment of sulfate in industrial effluents by the use of sulfate-reducing bacteria (SRB). Sulfide cause unpleasant odor, corrosion, damage to aquatic environment, and also process failure of bioreactors. Thus, sulfide should be removed from the effluents before discharged. Conventional physico-chemical treatments such as sulfide precipitation or addition of oxidizing agents can efficiently remove sulfide from wastewater. However, these processes consume large amount of chemicals and energy. The produced sludge is toxic and need a safe disposal. Recently, the biological sulfide oxidation by the use of sulfide oxidizing bacteria (SOB) becomes a better alternative with the advantages of lower chemical and energy requirement, less sludge production, and elemental sulfur recovery. Under limited dissolved oxygen (DO) condition, sulfide and other reduced sulfur compounds are partially oxidized to elemental sulfur which is easily removed from the waste streams. This research focused on the feasibility of sulfide removal and sulfur recovery from industrial wastewater by biological sulfide oxidation on airlift reactor. The lab-scale airlift reactor was operated under ambient condition to study the effect of sulfide loading rate and optimize the sulfur recovery. Moreover, the morphology of SOB is characterized by electron microscope and the properties of biologically produced sulfur were also analyzed. Synthetic sulfide wastewater was used as a feed and sodium bicarbonate was prepared as a carbon source for chemolithotrophic SOB. The influent flow rate was kept constant. The sulfide loading rate (SLR) was gradually stepwise increased from 0.80 kgHS-/m3-day to 4.00 kgHS-/m3-day. It was observed that sulfur was mainly produced instead of sulfate at SLR of 1.22 kgHS-/m3-day. The produced sulfur was further increased until it reached its maximum of 2.95 kgHS-/m3-day at SLR of 2.97 kgHS-/m3-day. At high SLR (> 2.2 kgHS-/m3-day), DO and pH were controlled between of 0.2-1.0 mg/l and 7.2-7.8, respectively. At SLR of 3.05 kgHS-/m3-day, the sulfur production dropped to less than 10% and sulfate became the main product with 60-70% of influent sulfide conversion. It was found that sulfur production had tendency to increase again at SLR of 3.33 kgHS-/m3-day. The accumulation of produced sulfur in the reactor reduced the contact of aqueous sulfide and the bacterial cells, thus, reducing the conversion of sulfide to sulfur. More recovered sulfur was produced at high sulfide loading rate due to the change of metabolic pathway of SOB which prevented the toxicity of sulfide in the culture. The airlift reactor successfully removed sulfide over 90% of the influent sulfide during the steady state operation. The produced elemental sulfur was analyzed by X-Ray diffraction (XRD) analyzer. The XRD pattern showed the elemental sulfur (S8) with orthorhombic structure. All peaks of the sample resemble S8 and most peaks matched with the commercial sulfur and analytical-grade sulfur. The biologically produced sulfur also contained organic compounds which were confirmed by the result from elemental analyzer. The percentage of carbon, nitrogen, and hydrogen are 4.44%, 0.79% and 0.48% respectively. |
| Year | 2010 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. EV-10-02 |
| 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) | Annachhatre, Ajit P.; |
| Examination Committee(s) | Chongrak Polprasert;Vilas Nitivattananon; |
| Scholarship Donor(s) | Asian Institute of Technology |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2010 |