STUDIES ON THE TREATMENT OF DAIRY WASTE WATER BY CARROUSEL SYSTEM

Abstract

Carrousel system which is an extended aeration system is a low load modification of the activated sludge process, characterized by long retention times of mixed liquor in aeration tanks and high contact of activated sludge suspended solids in mixed liquor. The carrousel system has intensified the aeration system, and ditches of upto 4m deep can be operated successfully with a minimum velocity of liquid of about 0.15 m/sec. Maintenance of dissolved oxygen in the mixed liquor at a required level is based upon the performance of the aeration system adopted. Also dthe success of the process is reflected by settleability of biomass in a suitably sized settlement tank. In the present study, the waste employed for investigations was a synthetic dairy wastewater. The entire investigation and the experimental work was carried out in three phases of study. Phase I investigates the mass transfer efficiency of an aerator with respect to dissolve oxygen at different speeds of rotor (100, 120, 140, 150, 160 & 180 rpm.) and at a fixed immersion depth of rotor (30mm). A speed of 140 rpm was found most suitable to provide the necessary oxygenation capacity. Therefore the entire treatment process was conducted at this particular speed. viii In phase II the system was operated under six hydraulic detention times namely, 1, 1.5, 1.75, 2, 2.54 & 3 days with the influent concentration being maintain approximately varying (with DOD from 810 to 850 mg/lit and COD from 1320 to 1450 mg/lit). Each run consist of seven days, out of which three days for bacterial acclimatization and four days for analysis. The third phase deals with the determination of kinetic constants for carrying the treatability study. In this phase the system was operated over a range of substrate concentrations, i.e. at several different values of ec'S, and then kinetic constants, Y,K,K6, Kd &/14m were found. The observations revealed that the overall efficiency of the system is higher than conventional systems and holds good future especially when land requirement is one of the very important considerations for providing treatment.