Kinetic study on the chemical oxygen demand removal at the optimum conditions in the treatment of textile bleaching and dyeing industrial wastewater using coagulation and flocculation

• Main Author: Tun, Lin Lin
• Format: text
• Language: English
• Published: Animo Repository 2007
• Subjects: Coagulation; Flocculation; Dyes and dyeing; Factory and trade waste; Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/3496; https://animorepository.dlsu.edu.ph/context/etd_masteral/article/10334/viewcontent/CDTG004278_P.pdf
• Institution: De La Salle University

Wastewater, from textile bleaching and dyeing industry is usually high in Chemical Oxygen Demand (COD) and solids, and is characterized by intense color, which gives adverse effects especially on the aquatic environment. Such wastewater can be treated using chemical treatment methods by coagulation and flocculation. The efficiency of coagulation and flocculation strongly depends on the initial pH of the wastewater and chemical dosages. Kinetics of COD removal by coagulation and flocculation at the optimum conditions in the treatment of Textile Bleaching and Dyeing Industrial Wastewater was studied. The optimum initial pH of the wastewater and chemical dosages of three different coagulants (alum, polyaluminum chloride PAC, ferrous sulfate) and of a flocculant (excelfloc 264) was determined using the jar test method. The initial pH of the untreated wastewater was varied at 5 to 8 for alum and PAC and at 9 to 11 for ferrous sulfate. Dosages of each coagulant and excelfloc were varied from 200 to 1000 ppm, and 0.5 to 2.5 ppm, respectively. Experimental results showed that the optimum initial pH of the wastewater using alum, PAC and ferrous sulfate were 7, 7.5 and 10, respectively. The optimum dosages of the coagulants were found to be 600 ppm for alum and, 800 ppm for PAC and ferrous sulfate. The optimum flocculant dosages were 1.5 ppm for alum coagulation, 1 ppm for PAC coagulation and 2ppm for ferrous sulfate coagulation. Highest percentage removal of COD, Total Suspended Solids (TSS), Total Dissolved Solids (TDS), chromium and color were found to be 58.84%, 65%, 36.51%, 76.45% and 94.49 % respectively using alum, 65.64%, 67.5%, 35.84%, 44.92% and 75.49%, respectively for PAC coagulation, and, 56.01%, 34.17%, 33.95%, 19.88 % and 48.56%, respectively for coagulation by ferrous sulfate. Kinetics of COD removal at the optimum conditions showed that the reaction kinetics of COD removal during flocculation followed first-order mechanism.