2013 年 11 巻 3 号 p. 187-195
The effectiveness of chitosan as a coagulant/flocculant in tunnel construction wastewater treatment has been studied. Chitosan is a biodegradable cationic polymer. The objective of this study is to develop an integrated desander and flocculator with inclined settler (IDFIS) system using chitosan coagulant. As a result of jar test, a chitosan optimum dosage of 5 mg/L for tunneling wastewater sediment, leave a residual turbidity of less than 5 NTU with this condition. Because the effectiveness of chitosan in removing turbidity was independent of pH, the operation of IDFIS system would be simple. The synthesized turbidity was made with clay particles, stream sediments, stream suspended sediment, and tunneling wastewater sediments. Results indicate that the overall removal efficiencies for turbidity, SS, COD and TP were 98%, 99%, 85% and 95%, respectively. The IDFIS system is possible to operate with compact design, because the increase of floc size favours the increase of settling speed and reduces the settling time.