Abstract:
This research studied nitrification of high urea concentrations, 50-1,000 mgN/L, at low pH to prevent ammonia gas production using trickling filter of low construction and maintenance cost. Controlled pH were 7, 6, 5, 4, and uncontrolled pH throughout the experiment. Results showed that at steady state, average specific nitrification rate at pH 6 was 0.577±0.004 gN/m2/d, similar to rate at pH 7 of 0.617±0.018 gN/m2/d, which was the optimum pH on the growth of nitrifying bacteria transforming urea to nitrate completely. Controlled pH at 5 founded that the average specific nitrification rate of 0.005±0.005 gN/m2/d and controlled pH at 4 did not find nitrate in every batch. Therefore, pH 6 was the most suitable low pH in trickling filter system for gas station restroom wastewater treatment which also eliminate odor of ammonia in the system with a yield of 0.032±0.023 gSS/gN. Moreover, results from uncontrolled pH showed that urea was not effectively treated since pH was decreased to lower than 6 and inhibited the nitrification process. From the effect of treating urea concentrations of 50, 100, 200, 500, and 1,000 mgN/L by controlled pH at 6, results showed that urea was treated to nitrate completely in all experiments. At steady state, nitrification rates followed Monod kinetics with km of 1.14±0.06 gN/m2/d and KS of 550.10±60.16 mgN/L. Therefore, trickling filter which was a biological aerobic treatment system using biofilm growth media can treat high urea concentration up to 1,000 mgN/L at pH 6 effectively.