Assessment of wastewater pollution in pig leather industry in China

Pig leather industry contributed significantly to the life of people all over the world, but serious water environmental problems have arisen. Investigation in tanneries with green pig hides in China showed that pollution resulted mainly from beamhouse operations. Assessment indicated that wastewater from pig-hides processing had: (1) wide variations of pH, (2) high levels of sulfide (S2-) and chromium, (3) high levels of neutral salts and ammonia nitrogen (NH 4+-N), (4) high levels of suspended solids (TSS) and oil & grease, and (5) low biodegradability. A tannery processing 10?000 pig hides per day generated chemical oxygen demand (COD) of 3.8112.31 tonnes and NH 4+-N 0.271.06 tonnes, respectively. The pollution loads were equivalent to those of a city of 60?000120?000 inhabitants, which has a COD of 3.910.56 tonnes/day and NH 4+-N of 0.4621.164 tonnes/day, respectively (SEPAC). And nearly 30% of the tanneries discharged their wastewater by screening only or by primary treatment like coagulationsedimentation, while the rest of them discharged directly into surface waters without any treatment.