Tannery wastewater pre-treatment

摘要

Tannery wastewater is one of the most pollution sources. It can cause environmental problemsnrelated to its high organic matter, suspended solids and chromium. Chromium (III) salts are thenmost widely used chemicals for tanning processes, causing the tannery wastewater to be highlynpollutant with chromium. The main objective of this study is to investigate the pre-treatment ofnan actual Egyptian tannery wastewater using two systems; the first electrolytic system and thensecond physico-chemical system. The performances of electrolytic system at current of 10, 20,n30 and 40A were discussed. Poor removal efficiencies of chemical oxygen demand (COD), totalnsuspended solids (TSS), chromium (III), ammonia NHþn4nu0001u0002nand sulfide (S22) were obtained. In thensecond physico-chemical system, calcium hydroxide was used as a coagulant material fornchromium precipitation and plain sedimentation was applied for reducing of COD, biochemicalnoxygen demand (BOD5) and TSS. The results demonstrate 98.8% removal of chromium, 31%nremoval of COD, 25.8% removal of BOD5 and 51.2% removal of TSS.