Diluted solutions of a peat water and a biological wastewater effluent were subjected to coagulation, ozonation, and chlorination. The effects of these pretreatments on the removal of humic substances by activated carbon adsorption were tested. Batch adsorption isotherms were analyzed using a distributed fictive component method, which assumed a logarithmic normal distribution of Freundlich K and a non-adsorbable fraction in the Ideal Adsorption Solution Theory for multicomponent adsorption. Coagulation treatment not only increased adsorbabilities but also decreased its heterogeneity in terms of multicomponent adsorbates. Ozonation decreased adsorbabilities and increased heterogeneity in adsorbabilities by producing weakly adsorbing compounds. The average Freundlich K decreased, while the Freundlich exponent, 1/n, and non-adsorbable fraction was increased with ozone consumption. Chlorination showed the same effects as ozonation. However, after ozonation, equilibrium capacity at low activated carbon doses was increased because of the reduced dissolved organic carbon concentration by ozonation.

A coagulation process for water purification plants mainly uses feedforward control based on raw water quality and empirical data and requires operator's help. We developed a new floc sensor for measuring floc size in a flush mixer to be used for floc control. A control system using model predictive control was developed on the floc size data. A series of experiments was performed to confirm controllability of settled water quality by controlling flush mixer floc size. An automatic control with feedback from the coagulation process was evaluated as practical and reliable. Finally this new control method was applied for actual plant and evaluated as practical.