Nitrogen removal from coke making wastewater through a pre-denitrification activated sludge process

Under the Industrial Emissions Directive (IED), coke production wastewater must be treated to produce an effluent characterised by a total nitrogen (TN) <50 mg/L. An anoxic-aerobic activated sludge pilot-plant (1 m(3)) fed with coke production wastewater was used to investigate the optimal operational requirements to achieve such an effluent. The loading rates applied to the pilot-plant varied between 0.198-0.418 kg COD/m(3).day and 0.029-0.081 kg TN/m(3).day, respectively. The ammonia (NH4+-N) removals were maintained at 96%, after alkalinity addition. tinder all conditions, phenol and SCN remained stable at 96% and 100%, respectively with both being utilised as carbon sources during clenitrification. The obtained results showed that influent soluble chemical oxygen demand (sCOD) to TN ratio of should be maintained at >5.7 to produce an effluent TN <50 mg/L. Furthermore, nitrite accumulation was observed under all conditions indicating a disturbance to the denitrification pathway. Overall, the anoxic-aerobic activated sludge process was shown to be a robust and reliable technology to treat coke making wastewater and achieve the LED requirements. Nevertheless, the influent to the anoxic tank should be monitored to ensure a sCOD:TN ratio >5.7 or, alternately, the addition of an external carbon source should be considered. (C) 2019 Elsevier B.V. All rights reserved.