Ammonia nitrification of a petrochemical wastewater by the eight generation of microbial consortium of autotrophic bacteria

If present in drinking water, a nitrate concentration above the standard level may reduce to nitrite in the human digestive tract. It then converts hemoglobin to methemoglobin with a significant loss in oxygen-carrying capacity, which is responsible for developing methemoglobinemia. The nitrite may also react with amines forming carcinogenic nitrosamines. The wastewater of a petrochemical was initially treated with microorganism of the municipality of Shahrek-e-Ghareb located in Tehran. The prolonged, poor, and irreproducible results were perhaps due to the inorganic nitrogen in the wastewater and the higher ratio of heterotrophic bacteria present. The present study’s results further indicated that autotrophic organisms are required to synthesize nitrification of wastewater containing inorganic nitrogen compounds. The autotrophic bacteria from wastewater of depot 93 of the Shiraz petrochemical plant was partially purified by the dilution method for 13 generations. The experimental results showed that the 8th generation microbial consortium was an effective source of bacteria for nitrification in the above wastewater. Hydrochloric acid was used to reduce the original pH of the wastewater, which was 10.5, to about the neutral range. The medium pH and alkalinity were increased to pH: 7.8 ± 0.1 by using 2 V/W % sodium carbonate, which resulted in an 80% ammonia oxidation of the wastewater. After examining the effects of parameters such as feed concentration, inoculum size, initial pH, shaker's speed, and temperature on nitrification, it was observed that using the 8th generation of a microbial consortium with a temperature maintained at about 29 ˚C, a shaker speed of 2.5 s-1, pH: 7.8, and inoculum size of 10 % V/V, resulted in approximately 85% ammonia oxidation when used in a Watson medium, and 80 % ammonia oxidation when applied to petrochemical wastewater. The data was fit into a Monod type equation, and an agreement of 99.68 % was obtained.