STUDIES ON BIO-DEGRADATION OF ORGANIC WASTE IN UASB REACTOR

Abstract

Rapid urbanization and industrialization in the developing countries pose severe problems in collection, treatment and disposal of the organic effluents. The situation leads to serious public health and environmental problem. Increased discharged of domestic and industrial wastewater should be clean. Decreasing assimilative capacity of water bodies, need for water consumption and growing public awareness in the maintenance of clean environment, bring to fore the need for development of appropriate, cost effective and resources recovery based wastewater systems. Therefore, towards this direction, many aerobic and anaerobic processes have been developed for treatment of wastewater. The anaerobic digestion has been successfully used for the treatment of domestic and industrial wastewater. Different types of anaerobic digestion units have been developed and among these Upflow Anaerobic Sludge Blanket (UASB) reactor system has received wide recognition. In the last two and half decades, the UASB reactor has been recognized as an efficient and energy saving anaerobic wastewater system. The UASB reactor was developed by Lettinga and his co-worker in 1970,s in Netherlands. Since the development of UASB, it has been used for the treatment of variety of liquid wastes of various industries such as sugar, distillery, petrochemical, refineries, food processing etc. The main advantage of UASB reactor over other reactors is lower initial cost, low operational and maintenance cost, low energy consumption, generation of biogas, small land area required, high efficiency, no noise pollution etc. Main emphasis in the present work is on the following aspects, viz., design of UASB reactor, development of startup strategies to enhance granulation with mixed culture, COD removal efficiency and gas production rate with change organic loading rate (OLR). In the present studies, initially reactor was started with mixture of molasses and glucose (50% each) solution with organic loading rate (OLR) 0.933 g COD/L day. Thereafter, OLR being increased in steps. After 15 days of startup of reactor molasses solution was applied. The temperature (35+4° C), pH (6.8+0.4), and nutrient requirement were maintained. In this study COD: N: P ratio were maintained 300:10:1 by adding urea for nitrogen and potassium di-hydrogen phosphate for phosphorous. For a change of OLR upto 13.33 g COD/L day, all above mentioned parameter were studied.