Development of pretreatment system for restaurant wastewaters by the use of oil/fat gydrolysis reactions catalized by lipase.

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Through experimental investigation to apply lipase, an enzyme to catalize fat/oil hydrolysis reactions, to the treatment of restaurant effluent, the following conclusions were obtained.1. About the combination of hydrolysis by lipase and the chemical coagulation treatment :(1) By neutralizing fatty acids produced through the lipase pretreatment of n-hexane extractable components in wastewaters with calsium salts, sludge with very good dewaterbility is formed, which can be removed as solid form by floatation or dewatering methods.(2) The above process is affected by the concentration of fats or type of existing substances in the wastewater.2. About the combination of hydrolysis by lipase and the activated sludge treatment :(1) By introducing a lipase pretreatment system for a restaurant wastewater, a sequence batch activated sludge system could be maintained in good conditions with an CODcr loading of 1.1kg/m3/d and an sludge retention time of 30 days.(2) The activated sludge processes with and without the lipase pretreatment did not significantly differ from each other in terms of the removal efficiency of n-hexane extractable compounds, but more fat seemed to be accumulated in the process without the lipase treatment.(3) When the loading of n-hexane extractable compounds increased, they leaked to effluent or were accumulated in the sludge in both the processes with and without lipase treatment. The critical loading of n-hexane extractable compounds beyond which satisfactory performance can not be achieved is 1 kg/m3/d. Restaurant wastewaters had better be concentrated when the lipase treatment is applied, but too much concentration can lead to deterioration.(4) When high concentration of n-hexane extractable compounds flew into the process, the sludge grew in a dispersed form. In this connection the control of the loading of n-hexane extractable compounds may be necessary.