Removal of organic pollutants from pharmaceutical industry wastewater by chemical coagulation and bentonite clay pretreatment

Abstract

The presence of substantial amounts of organic pollutants and toxic compounds are some of the factors that contribute to poor biodegradability of pharmaceutical wastewater. In this study, the removal of organic pollutants from pharmaceutical wastewater by chemical coagulation and bentonite clay was investigated. In one procedure, varying amounts of ferric sulphate and polyaluminium chloride were used for coagulation of the sample water. This was followed by flocculation and settling after which the treated effluent was collected and analyzed. In the second procedure, bentonite clay was added to the sample water and rapidly mixed at 400 rpm for 60 minutes before the coagulation/ flocculation processes were carried out as in the first procedure. The organic pollutant was measured in terms of Total Organic Carbon (TOC) and analyzed using a Shimadzu TOC-5000 carbon analyzer. The maximum TOC removal by polyaluminium chloride was 39.72% while that by ferric sulphate was 30.97%. With the use of bentonite clay, maximum TOC removal by polyaluminium chloride was 63.20% and that by ferric sulphate was 56.62%. There was a 97.40% removal of suspended solids with the use of bentonite clay compared to 82% obtained using chemical coagulants only. The improved results with the use of bentonite pre-treatment could be attributed to bentonite particles acting as nuclei for adsorption of organic compounds from wastewater as well as increasing the opportunity for particle collusion during coagulation/flocculation. Therefore, bentonite can offer a relatively lower cost option for the removal of organic carbon from pharmaceutical effluent.