Comparison of Physical and Chemical Treatment Methods For Rice Mill Wastewater and Subsequent Biomethane and Ammonia Generation
A small scale rice industry produces about 7000 Liter effluent per day having a Chemical Oxygen Demand
ranging from 4000 to 7000 ppm. The effluent contains mainly long chain carbohydrates which is ideal source of biogas
production. In this research work, physical and chemical methods for treatment of rice mill waste were investigated and
compared. Filtration, centrifugation and adsorption were used in physical method where as chemical methods included lime
treatment and hydrogen peroxide treatment. Filtration and centrifugation did not reduce COD values because impurities were
mainly in form of dissolved solids. Adsorption using bottom ash obtained from boiler located at rice mill reduced COD of
effluent by ca. 28%. Lime treatment ranging from 0.1 gm lime per 100 ml effluent to 2 gm per 100 ml effluent reduced COD
from ca. 23% to 43%, respectively. Hydrogen peroxide treatment gave best results of all treatments with ca. 98% reduction
in COD values. Sludge production was ca. 60% less in peroxide treated effluent as compared to lime treated effluent. The
sludge obtained from lime and peroxide treatment methods was further added to a batch anaerobic digester for biogas
production. Lime treated sludge reduced biogas production of a stable biogas producing digester due to increase in pH from
ca. 7.2 to 11.5. Biogas production was enhanced markedly when hydrogen peroxide treated sludge was added to anaerobic
digester as compared to lime treated sludge.
Keywords— Rice Mill Waste; Adsorption; Lime: Hydrogen Peroxide; Biogas.