Columnal desalting of soy sauce cake,
Shoyu Kasu, with 4 times its weight of water forms large volume of waste water, It contains 3.6%(w/v) N
aC1, 17, 800ppm BOD, and 15, 300 ppm COD and has a dark brown color.To drain the waste water into a river in meeting the standard for industrial drainage enacted by the local government, we studied reduction of its BOD and COD and decolorization by microbial and physicochemical treatments.
In the microbial treatment, 30 m
l of activated sludge was inoculated into 300m
l of the waste water and incubated aerobically at 25. In incubation for 4 days, its BOD decreased to 430 ppm and its COD to 2, 000 ppm. But its bacteria fromed flocs poorly and didn't sediment even after 15 days. The bacteria sedimented in 6-18 min at 0.3%-0.8%(w/v) N
aC1 concentrations of the waste water but didn't at more than 1.5%(w/v) NaCl. At the same time it was observed that the bacteria sedimented in 10 min at less than 2, 000 ppm BOD.
In the physicochemical treatment, 0.5%(w/v) activated carbon was found to adsorb 60% of colored materials in the waste water in comparison with charcoal bone, aluminum hydroxide, natural zeolite and others.
In the microbial and physicochemical treatment, the waste water was diluted tenfold into water and then treated with activated sludge.
Its BOD decreased to 48 from 1, 930 ppm, and its COD to 121 ppm.Subsequent treatment with 0.1% activated carbon for 3 times reduced COD value to 59 ppm as well as the colored materials.
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