WATER SCIENCE AND TECHNOLOGY, cilt.28, sa.2, ss.99-105, 1993 (SCI-Expanded)
Leather processing industry wastewaters contain several conventional pollutants as well as micropollutants.
Conventional pollutants can be effectively treated although considerable treatment comprised of several
stages is required. However, the potential of conventional methods to remove COD and micropollutants has
not been fully explored. The purpose of this paper is to investigate the extent of COD removal by
conventional methods. Experimental studies are conducted using raw wastewaters of industries applying
chromium tanning to cattlenhides and sheepskins. Biological treatability after pretreatment by chemical
coagulation is assessed using a lab-scale continuous activated sludge system. Results indicate that chemical
coagulation produces wastewaters with a COD of around 2000 mg/l almost independent of raw wastewater
quality. Activated sludge operated at 0.17 g BODs/g MLSS.d loading is found to provide limited nitrification
and almost complete BODs removal while the COD could only be reduced to around 500 mg/l. The residual
COD identified using a newly developed experimental approach shows that it cannot be reduced lower than
300-550 mg/l.