EFFECT OF AERATION AND SURFACE ACTIVE AGENTS ON a-FACTOR OF WASTE WATER

Abstract

Aeration is basically a gas-liquid mass transfer process in which interface diffusion occurs when a driving force is created. In wastewater treatment process, aeration provides an aerobic environment for microbial degradation of organic matter. Diffused aeration is the injection of gas under pressure below the liquid surface. Fine pore diffused aeration has been employed in the wastewater treatment process for higher OTE (oxygen transfer efficiency). The parameter, which is directly related to the oxygen transfer is the overall mass transfer coefficient, KLa. It is affected by various factors — temperature, degree of mixing, wastewater characteristics, and type of aeration devices. Higher KLa denote the better rate of oxygen transfer in the systems. In the present work aeration process is carried out for both tap water and wastewaters using diffused aeration system for determination of KLa and alpha factor. The effect of surfactant (NaLSO4 ) on tap water and wastewater are also studied. The experiments are conducted on tap water at various flow rates (0.33L/S to 0.71 L/s) and at various liquid depths (0.57 m to 0.87 m) for determination of OTE (oxygen transfer efficiency) and alpha factors. The values of alpha factor varied from 0.42 to 0.76 and beta factor 0.87 and 0.9. The OTE generally increases with increasing with liquid depth. At liquid depth 0.87 m, it may vary from 1.07 to 2.0 % at flow rate 0.62 L/S. The surfactant present in both tap water and wastewaters reduce the value of KLa (overall mass transfer coefficient) and alpha factor.