2006 Volume 7 Issue 1 Pages 49-54
The effect of enzyme addition for the sedimentation activity of solid particles (mainly starch and bran) in waste water derived from a rice washing and manufacturing plant is described to decrease water treatment costs and reuse the ingredients of such waste water. Sedimentation of solid particles in waste water was highly dependent on enzyme concentration, temperature, and duration: the highest sediment ability (SV60: 43 (%) and SVI: 7.2 (ml⋅g-1) ) was obtained by the addition of protease M (acidic protease and pronase were contained) under 30°C and 24h duration. The total carbon (TC) concentration in the supernatant after enzyme treatments and sedimentation was almost the same value as the supernatant of waste water after centrifuge and less than 15% of the stock waste water without enzyme addition. Moreover, in the results of surface electron charge analysis, surface electron charges (mV) of solid particles in wastewater were increased by enzymatic treatment, and highly correlated values (r=0.848) with SV60 (%) were observed. These results suggest the occurrence of sedimentation and the concentrate of solid particles in waste water by the addition of enzymes as a result of the strong negative electron charges in solid particle surface and electrostatic interaction such as adsorption phenomenon.
