Effects of ultraviolet-enhanced ozonation on the degradation of ammonia and urea in fertilizer plant wastewater

Ammonia and urea contained in fertilizer plant wastewater are pollutants to the environment. High concentration of ammonium and urea in wastewater can affects algae blooms in the ecosystem which will generate various diseases in aquatic biota. It is known that there are many methods for degradation of ammonium and urea contained in fertilizer plant wastewater. One of the potential method is ultraviolet-enhanced ozonation. Ozonation is oxidation with O3 that generates hydroxyl radicals which subsequently react with organic contaminants, while UV irradiation can break down O3 molecules and produce radical ions OH∗. The objectives of this study were to examine the effects of the utilization of the ultraviolet-enhanced ozonation method in degradation of various initial ammonium (100-300 ppm) and urea concentration (100-300 ppm) in inlet feed of ozonation-UV irradiation combination system. Some important variables such as contact time (0-120 minutes) and ozone feed rate of 0.2, 0.6, and 1.21 g/h were evaluated. Degradation process was carried out in two steps; ozonation and UV irradiation. Ozonation process was carried out in a contacting tank at a constant feed flow rate of 1.5 l/min and at room temperature, while UV irradiation process was conducted in pipeline equipped with a UV lamp at various contact time. The ultraviolet-enhanced ozonation could degrade ammonium and urea nitrogen up to 83.6% and 63.8%, respectively, at ozone feed rate 1,21 g/h, contacting time 60 and 120 min, initial feed concentration of ammonia (100 ppm) and urea (40 ppm).