Advanced treatment of recalcitrant textile wastewater and goal-oriented process design

This study was intended to evaluate the performance of a biological and a chemical treatment process of recalcitrant textile wastewater. The biological process consisted of Activated Sludge (AS) reactor followed by column reactor packed with cellimmobilized pellets. The chemical process consisted of coagulation/precipitation and ozone oxidation. Experiments were conducted by pilot-scale reactors fed with textile wastewater. The removal efficiency of BOD by AS process was 85%, but only 45% of the COD was removed, indicating the AS process was not satisfactory in removing recalcitrant organic matter. However, the packed-bed column reactor effectively removed the recalcitrant organic matter, showing stable performance at an empty bed contact time of 8. hours. Both PAC and ferric chloride appeared to be excellent coagulants for removal of the remained hardly-biodegradable COD. Although the previous biological processes and coagulation/precipitation had already removed 74% of the color in the influent, most of the remaining color was removed by ozone oxidation at a contact time of 20 minute. A combination of AS, PEG-pellet column, and coagulation/precipitation produced a good effluent quality which met the discharge standards of most Asian countries. Additionally, if the ozone oxidation was added, the effluent quality could meet more stringent standards of advanced countries.