CHEMICAL OXIDATION OF PRIMARY SLUDGES FROM COMMON EFFLUENT TREATMENT PLANTS USING PEROXIDES AND FENTON'S REAGENT

摘要

Hyderabad, the capital city of Andhra Pradesh, India is surrounded with as many as 8 large industrial estates of which the dominant type are pharmaceutical, bulk drug, textiles, dye and dye intermediates metal plating industries besides some chemical and allied product manufacturing industries. The effluents from these industries are generally treated in common effluent treatment plants (CETP's) two of which exist in the city of Hyderabad which treat around two million litres of effluent per day generating 1400 kilos of primary sludge. These effluent treatment plants adopt physico chemical treatments such as coagulation and sedimentation producing primary sludge, which is very complex in nature and not easily biodegradable. Presently these primary sludges are being disposed in a landfill. The high risk of groundwater contamination due to the existing landfills has changed the present perspective of the environmentalists and alternative methods for disposal of these toxic industrial sludges are being adopted. Chemical oxidation is one of several innovative technologies that show promise in destroying or degrading an extensive variety of hazardous wastes. The process of chemical oxidation is economically feasible as these oxidants are readily available, and treatment time is usually very short. In the present study lab scale experiments were carried out for the CETP primary sludge having 55.2% of initial Total Organic Matter (TOM) by varying the concentrations of strong chemical oxidants such as hydrogen peroxide, calcium peroxide and Fenton's reagent. pH, and Total Organic Carbon (TOC) were monitored during the reactions. Fenton's chemistry was studied over concentration ranges of 30-150 mg/gm of Hydrogen peroxide and 0.05-0.5 mg/gm FeS04.Under optimum conditions, maximum TOC reduction of 94% was achieved with Fenton's reagent as an oxidant at a concentration of 90 mg/g H_2O_2 and 0.5 mg/gm FeSO_4 in three hours. With Hydrogen peroxide 82% reduction was achieved in six hours at a concentration of 450 mg/gm and 72% reduction was achieved with calcium peroxide in five hours at a concentration of 600 mg/gm. These studies indicate chemical oxidation technology can be used as an effective means of remediation of complex organic wastes from common effluent treatment plants.