Influence of Metal Ions on Biodegradation of High Organic Load Wastewater by Photosynthetic Bacteria

Laboratory simulated brewery wastewater with chemical oxygen demand (COD) and total phosphorus (TP) of 10,000 and 685.6mg/L was used to study the effects of metal ions supplement on pollutants biodegradation by phototrophic bacteria named Rhodobacter sphaeroides Z08. The results showed that the process, when operated microaerobically at 20–30°C, influent supplemented with ferrous 50mg/L, molybdenum 200mg/L, and magnesium 400mg/L yielded 55 & 38; 43 &36; 41 & 36% reductions of COD and TP respectively at three day hydraulic retention time. Binary addition of ferrous and molybdenum increased the cell growth without any significant effect on the pollutants removal. Best impact was binary addition of ferrous and magnesium which yielded still 55% COD reduction but with higher bacterial biomass (1536mg/L DCW). Chemical analysis of the treated wastewater and the harvested biomass showed that majority of the inorganic constituents of the wastewater were assimilated by the bacteria which is an indication of its metal tolerance ability.