FERRIC ION TOXICITY IN ANAEROBIC REATME.NT OF DOMESTIC WASTEWATER

Abstract

Anaerobic treatment is popular technique used for treatment of wastewater. Efficient and proper working of any treatment plant requires adequate microorganisms working inside reactor. Maximum rate of substrate utilization is most important for efficient treatment of wastewater. In certain cases toxicants such as heavy metals, organic compounds, chemicals enter wastewater they inhibit the working of microorganisms this causes reduction in treatment efficiency, even reactor failure may take place. In present study effects of iron (ferric ion) on anaerobic treatment of domestic wastewater were observed Two Anaerobic Baffle Reactors (ABRs) were allowed to attain Pseudo Steady State (PSS), they achieved PSS on day 134th day after they were started. The maximum COD removal efficiency observed was 92.8 and 92.6% in case of reactors Ri and R2 respectively. Then they were dosed with iron, dosing was done in pulse and continuous manner. Chemical Oxygen Demand (COD) was assessed to determine extent of inhibition. It was observed concentration of Fe3+ (00 t'gj~4were easily assimilable in anaerobic baffle reactor, but at higher concentration of iron sudden rise in toxicity of iron was seen. The COD removal dropped up to 60.8 % and 58.1% in case of pulse dosing and 84.5% in case of continuous dosing on seventh day from starting of dosing. Bioaccumulation of iron and drop in pH was observed, which were two major causes of toxicity of iron. The pulse dosing was observed to be more inhibitory than continuous dosing. Chapter I gives information of anaerobic digestion and anaerobic reactors. Chapter II discuses mechanism of inhibition and various aspects of inhibition are discussed, it also gives summary of toxic effects of other metals and compounds on anaerobic process. Toxicity of iron is also discussed. Chapter III explains material and methods used in study. Chapter IV discuses the experimental observations and results. Conclusion is incorporated in chapter V.