Simultaneous denitrification and organics removal by denitrifying bacteria inoculum in a multistage biofilm process for treating desulfuration and denitration wastewater

This study aimed to treat real wastewater from the desulfuration and denitration process in a petrochemical plant with high-strength nitrogen (TN approximate to 200 mg/L, > 90% nitrate), sulfate (2.7%) and extremely low-strength organics (CODCr < 30 mg/L). Heterotrophic denitrification of multistage anoxic and oxic biofilm (MAOB) process in three tanks using facultative denitrifying bacteria inoculum was developed to simultaneously achieve desirable effluent nitrogen and organics at different hydraulic retention time (HRT) and carbon to nitrogen (C/N) mass ratios. The optimum condition was recommended as a C/N ratio of 1.5 and a HRT of A (24 h)/O (12-24 h) to achieve > 90% of nitrogen and organics removal as well as no significant variation of sulfate. The denitrifying biofilm in various tanks was dominant by Hyphomicrobium (8.9%-25.7%), Methylophaga (18.6%-25.8%) and Azoarcus (3.3%-19.6%), etc., containing > 20% aerobic denitrifiers. This explained that oxic zone in MAOB process also exhibited simultaneous nitrogen and organics removal.

Automated summary

This study developed a heterotrophic denitrification process using multistage anoxic and oxic biofilm (MAOB) to treat wastewater with high-strength nitrogen, sulfate, and low-strength organics. The recommended optimum conditions were a C/N ratio of 1.5 and a HRT of A (24 h)/O (12-24 h) to achieve > 90% of nitrogen and organics removal. The dominant denitrifying biofilm species in the tanks included Hyphomicrobium, Methylophaga, and Azoarcus, containing > 20% aerobic denitrifiers.