Tannery wastewater treatment process to minimize residual organics and generation of primary chemical sludge

Wastewater discharge from the leather manufacturing process involves various operations such as beam house, tanning and post-tanning. The conventional treatment system does not efficiently treat these kinds of wastewaters without the generation of any secondary pollutant. Mostly vast quantities of chemicals are added to the wastewaters to adjust pH to favour the treatment units that results in a huge amount of primary chemical sludge. This paper reports a new treatment approach by mixing various tannery operational wastewaters in the appropriate treatment units to adjust pH instead of adding chemicals. It also designed a treatment sequence to simultaneously treat all tannery operational wastewaters in such a way to suit their biodegradability and to avoid sludge to a greater extent. The treated water resulted in biochemical oxygen demand, 58 ± 39 mg L −1 ; chemical oxygen demand, 305 ± 35 mg L −1 ; total organic carbon, 94.93 ± 45.46 mg L −1 ; total nitrogen, 295 ± 226 mg L −1 ; ammoniacal nitrogen, 146 ± 75 mg L −1 .