| 摘要 |
[Object] In relation to the treatment of organic wastewater in which organic wastewater is separated from biosludge by solid liquid separation using a separation membrane and the permeate water is subjected to RO membrane separation treatment and further in which normal solid liquid separation treatment is suspended and the membrane is cleaned by passing a cleaning liquid through the membrane from the permeate water side to the concentrated water side, the invention prevents a decrease in the flux of RO membranes due to TOC components eluted from the sludge during membrane cleaning and thereby reduces the frequency of chemical cleaning of the RO membranes as well as increases water recovery rate, thus allowing the treatment to be performed stably and efficiently. [Solution] After membrane cleaning, the solid liquid separation is resumed in such a manner that the pH of the obtainable permeate water is adjusted to not less than 9.5 and a scale inhibitor is added to the permeate water, and the permeate water is thereafter treated by RO membrane separation treatment. By adjusting the pH of the RO feed water to a highly alkaline pH of not less than 9.5 as well as by adding a scale inhibitor, it becomes possible to suppress TOC components eluted from sludge from being adsorbed onto RO membranes and from generating slimes as well as consequently to prevent a decrease in the flux of RO membranes. |
