Achievement and inhibition of nitrification in coking wastewater treatment by A/O1/H/O2 processes

Key words: 
• coking wastewater /
• nitrification /
• toxic pollutants

Abstract: Toxic pollutants from coking wastewater have negative impacts on nitrifying bacteria and can undermine the stability of nitrification process. This study investigated a wastewater treatment technique of A/O1/H/O2 based on the water monitoring data, several major pollutants were found to have inhibitory effect on nitrification in the second aerobic fluidized bed. The result indicated that phenol, SCN- and quinoline could inhibit the nitrification process, EC50 values of the pollutant were 34.26, 278.5 and 73.24 mg/L，respectively. In order to reach the optimum operating condition of the secondary aeration process, C/N ratio should be 4.3/1, pH 8～8.5 and DO 4～5 mg/L, under this condition ammonia level in the effluent was less than 5 mg/L. It showed that the coking wastewater biological treatment adopting A/O1/H/O2 could hold strong anti-inhibitory effect of toxic pollutants and also achieved low-power highperformance nitrification.