A study of coagulant demand in algal harvesting | |
| Author | Vichitra Chovichien |
| Call Number | AIT Thesis no. 585 |
| Subject(s) | Water--Purification Sewage disposal Oxidation |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand. |
| Publisher | Asian Institute of Technology |
| Abstract | Experimental investigations were performed to study the influences of variables affecting coagulant demand in algal harvesting from the high rate oxidation pond. The variables considered were particle sizes, alkalinity, phosphate, sulphate, calcium, magnesium and algal concentrations. The age of the algae in suspension was also considered. All tests were conducted by the common jar test technique, operating at an initial fast mixing of 80 rpm for 40 seconds followed with 60 rpm for 120 seconds. pH was maintained at optimum of 4o5. The extent of flocculation was measured by percent transmission of the settled supernatant, settled volatile solids and residual aluminum concentrations. The effects of particle sizes in pond water were investigated by fractionation through filtration and centrifugation techniques. Colloidal particles (O-lµ) were found to play a significant role in exerting coagulant demand. Large particles including algal cells facilitated agglomeration of flocs. Alum flocculation was also found to be affected by alkalinity and phosphate ions. The influences of concentration and growth phase of algae over flocculation were observed. More alum was required at too low or higher algal concentrations. However, it seemed to be more economic to harvest algae at high concentrations. The coagulant demand for flocculation was also related to the growth phase (algal age). High dosages of alum were required as algae entered their exponential growth phases.. Thereafter the demand decreased gradually in time. A technique of electrical shock wave for algal flocculation was applied to harvesting of algae o An experiment was performed to determine· the effects of mixing, pH, power supplied, effluent flow rate and alum additions on flocculation. Costs of energy and chemicals required for flocculation of algae by this technique were estimated. The experiment showed that the electrical shock wave has potential but requires further experimental work before it can be utilized as a less expensive technique than alum flocculation. |
| Year | 1972 |
| Type | Thesis |
| School | Student Research Before 1980 |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Thesis (Year <=1979) |
| Chairperson(s) | McGarry, M.G. |
| Examination Committee(s) | Suwan Sangpetch |
| Scholarship Donor(s) | Asian Institute of Technology |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 1972 |
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