Decolorization of Secondary Treated Water from Livestock Urine Waste

There are many swine farmers near the rivers in Gunma Prefecture and the secondary treated water from the farmers comes into the river. The color of the drainage is dark brown. Although there is no regulation of chromaticity of the waste water from the farmers, one of the biggest concerns of the farmers is the color of the waste water. An absorbent was prepared by radiation grafting of cationic monomer on fiber to reduce the color. The color was easily removed using the absorbent. COD of the waste water was also reduced after decolorization. The decrease in chromaticity using absorbents depended on the degree of grafting of the absorbents. Maximum decrease in 4 h was obtained when absorbent with 86% degree of grafting was used. The absorbed colored substances on the absorbent were easily desorbed using salt solution. Colored substances were precipitated adding acid to the desorbed solution. The colored substances in the secondary treated water were estimated to be humic substances. The absorbent and desorbent after removing colored substances could be used repeatedly. Environmentally-friendly new system is proposed to treat secondary treated water from livestock urine waste.