With the development of industry and the increasing of urban population, the wastewater treatment is being given more and more attention. For example, in chemical industry (pharmacy, zymolysis, paper making etc), wastewater treatment is very important to control liquor pH in a certain bound in these processes. But pH process has serious nonlinearity and hysteresis. There are many difficulties in detecting and controlling of pH value. The level of automation of the pH control system in China relatively falls...