Respirometric assessment of vegetable tanning process wastewater generated from tanneries

Abstract

Abstract Registration, Evaluation, and Authorization of CHemicals (REACH) regulations insist on ready biodegradability information for organic chemicals that are used on a large scale in industries. Leather industry being one such, involves addition of organic chemicals that are obtained from plant extracts for vegetable tanning process. In view of the fact that biodegradability assessment is of paramount importance now for industrial wastewaters, a study was conducted on vegetable tanning process wastewater generated from tanneries. As per the Organization for Economic Cooperation and Development (OECD) methods for ready biodegradability (301 C), respirometer studies were conducted on wastewater containing different tannin concentrations of 540 mg/L (T1), 900 mg/L (T2), and 1350 mg/L (T3). The oxygen uptake rate had shown a sharp initial peak at 74, 102, and 164 mg O2/d for the three samples T1, T2, and T3, respectively. The primary degradation % of tannins was found to be 78%, 50%, and 14% for T1, T2, and T3 respectively. The Chemical Oxygen Demand and Biochemical Oxygen Demand removal efficiency also decreased with increase in tannin concentration. The t1/2 values of tannin, calculated using the first‐order kinetic equation, was 8.8, 10.9, and 12.4 days and the experimentally observed t1/2 values were 9.8, 11.5, and 12.6 days for T1, T2, and T3 respectively. This study establishes that presence of tannins in the aerobic treatment significantly affect the oxygen uptake when the tannin concentration is increased. This study emphasizes that ready biodegradability assessment is essential to establish biodegradability of all the organic chemicals used during leather making process.

Keywords

• aerobic treatment
• biodegradability
• first‐order kinetics
• oxygen uptake
• Respirometry
• tannins