Recent revisions to Japan's Water Pollution Control Law have reduced the allowable cadmium content in wastewater from 0.1 mg/l to 0.03 mg/l.
Oji has developed a cadmium removal system based on its chemical treatment and ultrafiltration technologies. The company reports that a system delivered to Monbetsu Fishery Cooperative Association has demonstrated that cadmium can reliably be removed to the new value, or less.
In the Oji process, the dissolved cadmium in the wastewater is chemically treated to form solid particles in suspension, which are then removed by an ultrafiltration membrane. Compared with other systems such as dissolved air floatation and adsorption, the technology is said to offer a number of benefits.
It ensures reliable cadmium removal. Using an ultrafiltration membrane with a pore size of 0.02 µm it is possible to comply with the new stricter effluent standard.
Energy and cost savings are realised. The treatment involves minimal chemical costs, and the system has a low electric power requirement because of the highly efficient membrane filtration system.
The compact equipment requires a small installation space due to the efficient and simple treatment process with compact pretreatment tank and separator.
According to the Nikkei Asian Review, by eliminating the need for sedimentation and filtration tanks used in conventional water treatment facilities, setup costs are reduced by two thirds and filtration capacity raised by a factor of four or more. The report says the company intends to introduce its system at 20 locations in Japan, mainly water treatment facilities, in the next five years, as well as locations across Southeast Asia, where facilities that can efficiently, and at low cost, filter river and reservoir water are in high demand.