Toxicity reduction in leather tanning wastewater by improved coagulation flocculation process

Abstract

The wastewater of leather industry which is one of the most widespread industries having large amount of water consumption and very high pollution loads, may be characterized by several key parameters including toxic pollutants exhibiting toxicity. Therefore the effluent of leather tanning industry must be handled carefully during both treatment plant design and operation.The aim of this study was to improve the coagulation process for toxicity reduction of raw wastewater taken from a leather tanning district central treatment plant (Solofra, (Avellino, Southern Italy). A series of jar test experiments on three samples taken between February and July 2005, were performed using ferric chloride, ferrous chloride, aluminium sulphate and polyaluminium ferric chloride (PAFC).The optimum coagulation conditions for the first sample were determined as 8.5 pH and 900 mg l -1 dose of PAFC with the addition of Ca(OH) 2 which resulted in a 76% COD and 98% TSS removal and more than 50% of D. magna immobilization (at 50% dilution) reduction. Coagulation experiments performed on second and third samples showed that PAFC resulted in the highest COD removal among the coagulants tested The results that PAFC, recently developed coagulant, is the most promising one for leather tanning wastewater, thus, improved coagulation followed by biological treatment can result in safe effluent to aquatic environment.

Evaluation of the Light/Dark Cycle and Concentration of Tannery Wastewater in the Production of Biomass and Metabolites of Industrial Interest from Microalgae and Cyanobacteria

“…Coagulation has been widely used due to its ease of operation; however, this process may generate secondary wastes. Likewise, compounds such as aluminum sulfate and ferric chloride affect the removal of suspended solids, COD, and chromium up to 46%, 37%, and 99%, respectively, at optimum coagulant concentrations and optimum pH values (7.5) [3,4]. Other processes, such as electrocoagulation, can remove up to 82% of COD [5,6].…”