Denitrification of simulated nitrate-rich wastewater using sulfamic acid and zinc scrap

An enhanced chemical denitrification process was studied as an alternative treatment of nitrate-rich wastewater which cannot be easily treated using conventional biological methods. To accelerate denitrification and to reduce the conversion to ammonia, nitrite reductants were added. In a batch test with the initial nitrate concentration of 500 mg NO3− -N per L, sulfamic acid and zinc were found to be the best nitrite and metal reductants, respectively. In a column test with the initial nitrate concentration of 500 mg NO3−-N per L, optimum results were experimentally obtained over a zinc scrap column with a 1.0 molar ratio of [NH2SO3H]/[NO3−-N] and the recirculating flow rate of 6 L min−1 at pH 2.5. Approximately 98.8 % of nitrate anions were removed, and the observed reaction rate constant (k) was 0.135 min−1. Zinc consumption was reduced to 46.6 % compared to the procedure without sulfamic acid, and sulfamic acid consumption was reduced to 40 % compared to the results of our previous study. Based on these experimental results, it was concluded that chemical nitrate denitrification using sulfamic acid and zinc scrap is an effective alternative treatment protocol for nitrate-rich wastewater.