| Author | Hossain, Golam |
| Call Number | AIT Thesis no. 444 |
| Subject(s) | Algae
Sewage lagoons
|
| 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 | High rate oxidation ponds have proven to be effective in the treatment of waste waters and may provide additional benefits in terms of algal protein production. Separation of algae from pond effluent by chemical coagulation and flotation appear to be the most effective technique for algal harvesting. However, the cost of chemicals constitutes a major portion of the costs of algal production. It was suspected that growth conditions of algae might influence the flocculating characteristics of algal cells and that through controlled conditions of growth, reductions
in chemical coagulant requirements for algal flocculation might be achieved.
The effects of growth period, incident light intensity during
growth, addition of cations, sea - water, alum, polyelectrolyte and
ferric chloride into the growth media prior to algal growth and
alum flocculation after growth, were all studied, each in separate experiments as to their effects on algal flocculation characteristics. The effects of algal cell age in reducing chemical coagulant requirements for primary concentration of algae were observed to be most influential. Algae grown in ponds having longer detention periods required less coagulant for chemical flocculation than those grown in ponds with low detention periods. The effects of
addition of ferric chloride, Purifloc C- 31 and aluminum chloride into the growth media prior to algal growth were proven significant in reducing coagulant demand for flocculating algae thus grown.
Similar additions of seawater and magnesium were marginally effective in reducing such coagulant demand. Addition of sodium or calcium into the growth media before algal growth or incident light
intensity during growth within the range studied had no or very
little effect on algal flocculation tendencies. It was possible to increase algal removal from 80 to 100% by increasing the sea
water addition from 0% to 1.0% at a detention period of 5 days and initial algal concentration of 150 mg/l with 60 mg/l alum dosage for flocculating algae after growth. Increase in addition of iron and aluminum h=fore growth from 0.2 mg/l to 0.5 mg/l increased algal recovery from 50-90% at a detention period of 3 days, initial algal concentration of 100 mg/l and alum dosage of 50 mg/l after
growth. It was therefore postulated that algal growth conditions did influence chemical coagulant demands for primary concentration of algae by chemical flocculation. Prototype high rate ponds would need dilution of influent sewage for optimum pond operation. The clarified effluent from the flotation plant could be recycled back to the pond for diluting
influent sewage. It appears that the recycled of excess coagulant
in the clarified effluent back into a prototype pond would be effective in reducing the coagulant requirements after growth there by reducing the cost of algal harvesting. |
| Year | 1971 |
| 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) | Pescod, M.B. |
| Scholarship Donor(s) | Asian Institute of Technology,
Applied Scientific Research Corporation of Thailand, Canadian International Development Agency and Refuse and Nightsoil Disposal Organization of Bangkok. |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 1971 |
