Denitrification of ammonium nitrate industrial wastewater using sulfur and limestone packed bioreactor

Abstract

One of the ammonium nitrate industries in Indonesia, PT.X, is located in West Java. This industry produces wastewater containing 1890 mg/L ammonia-nitrogen, 1800 mg/L nitrate-nitrogen, and 51 mg/L nitrite-nitrogen. In industrial treatment, this wastewater is treated using activated sludge nitrification and anoxic denitrification by adding carbon sources such as methanol or glucose. Denitrification process using autotrophic bacteria is applied in wastewater treatment as an alternative method for reducing the cost of wastewater treatment. The bacteria can grow and develop on elemental sulfur. This paper presents the results of industrial wastewater treatment of ammonium nitrate by two processes: nitrification using activated sludge and denitrification using sulfur and limestone packed-bed bioreactors. Sulfur was used as an electron donor, reducing nitrate to nitrogen gas with sulfate as a by-product. Limestone was used as a material that could minimize the pH decrease caused by the sulfate formation. The residence time applied in this study was from 1 to 4 days; the longer the residence time, the higher the efficiency of nitrogen nitrate reduction. The highest efficiency of nitrate-nitrogen reduction was 97%, achieved at a residence time of 4 days at the nitrate-nitrogen initial concentration of 2,000 mg/L. The water pH during the denitrification process was in the range of 6.5-7.5, meeting the pH quality standard to be discharged into the environment.