Electrolytic removal of algae was conducted in batch and continuous reactors to investigate operating factors affecting removal ef®ciency and to explore engineering relationships which could be useful for operation and scale-up. The system integrated both electro-¯occulation and electrootation mechanisms by using polyvalent metal anodes and inert metal cathodes. Batch reactor studies con®rmed that high electrical input power or higher electrical current achieved higher and faster removal ef®ciencies. Natural liquid circulation was observed during electrolytic operation and increased with higher electrical power. However, a small degree of external mixing may be useful at lower electrical power input. Electro-¯otation alone could not achieve complete algae removal (maximum ef®ciency 40±50%), and showed the importance of algal¯oc formation for the complete removal of algae. In continuous electrolysis experiments, the ratio of the volumetric current intensity (amperes dm À3) and the chlorophyll a loading (mg dm À3 h À1) was found to be a useful operating and scale-up factor to balance high algal removal ef®ciency with minimum release of excess aluminum. This ratio was eventually found to be just the charge dose or the amount of coulombs required to remove a unit mass of chlorophyll a. The optimum charge dose was determined and used to relate the operating current and electrolysis time of a continuous process.

No abstract

A good cysteine addition method that could increase the specific glutathione (GSH) production rate (Pc) was investigated and utilized to maximize total GSH production in fed-batch culture of Saccharomyce s cerevisiae. The single-shot addition of cysteine was a better method compared to a continuous method that maintained a constant cysteine concentration in the.. reactor. The shot method increased Pc about twofold compared to a culture without cysteine. The increase in Pc by the shot method can be achieved without growth inhibition if the cysteine dose is maintained at 0.7 mmol.g-1 cell or less. The positive effect on Pc (at every specific growth rate,/z) was saturated when the cysteine shot concentrations was 3 mM or more. A simple model was developed consisting of mass balance equations and the relationship between p and Pc, for the single cysteine shot addition method. From this model an optimal operating strategy was determined to maximize total GSH production in fed-batch culture. This optimal operation consisted of separating the process into phases of (1) cell growth and (2) GSH production, through a bang-bang profile control of/z, and a shot of cysteine just at the start of the GSH production phase. In other words, the cysteine shot time and the ~ switching time should be the same. For a total feeding time of 10 h, both the switching time of p and cysteine shot time were calculated to be about 6.4 h.

No abstract

Ozonation of distillery slop waste was done to evaluate the process in terms of organic matter removal and decolorization efficiencies. The chemical properties of melanoidins, which are known to harbor the chromophoric groups in the waste were also investigated. Ozone had primary effects on the decolorization of the slops and improvement in its biodegradability, compared to organic matter removal (as COD). A decolorization efficiency of 80% and a biodegradability improvement of 40% was obtained in 40 hours. Only 16% of the COD was removed. The melanoidins had a 10% decrease in molecular weight indicating slight depolymerization. UV spectral studies of melanoidins showed that olefinic linkages (which are said to be important in the structure of the chromophores) decreased.