Liquid waste processing method and device in nuclear power plant

Liquid wastes containing suspended materials in coolants are separated by precipitation, and a neutral salt additive for increasing only the electroconductivity with no pH change is added to a supernatant water containing not precipitated fine suspended materials, or reaction materials for generating the neutral salt additive are added thereto. After adjusting the electroconductivity, the suspended materials are removed by filtration treatment regenerated by back washing and separated by precipitation. Upon adjusting the electroconductivity, a neutral salt additive such as Na2SO4 is added to the liquid waste containing finely suspended materials, or NaOH and H2SO4 are admixed to adjust the electroconductivity to not less than 50μS/cm. With such procedures, finely suspended materials which are less precipitated in the precipitation separation vessel are easily precipitated. Accordingly, the finely suspended materials do not circulate between the precipitation/separation vessel and the filtration device, thereby capable of processing liquid wastes rapidly. (T.M.)