Effect of supplementary carbon addition in the treatment of low C/N high-technology industrial wastewater by MBR

The effect of supplementary carbon addition for the treatment of high-technology industrial wastewater in a membrane bioreactor (MBR) was investigated. The MBR was operated for 302 days under different C/N (BODL/NH4+-N) ratios, i.e. 0.9–1 to 20 days, 1.6–21 to 42 days, 2.9–43 to 82 days, 3.6–83 to 141 days, 4.8–165 to 233 days and 9.3–240 to 302 days. Irrespective of the C/N ratios investigated, SS and BOD5 removal efficiencies were above 95% and above 80% COD removal efficiency was observed. In addition, complete nitrification was observed throughout the investigation. However, denitrification and total nitrogen removal efficiencies reached their maximum values at the highest C/N ratio (9.3) investigated. Real-time PCR analysis revealed 10 times higher ammonia oxidizing bacteria to total bacteria ratio under the highest C/N ratio condition (9.3) compared to the low C/N ratio condition (1.6).

► Addition of supplementary carbon source increased the efficiency of treatment.
► SS and BOD5 removals reached over 95% irrespective of C/N ratios investigated.
► Highest denitrification and total nitrogen removal efficiencies observed at a C/N ratio of 9.3.
► Complete nitrification observed under all C/N ratios investigated.
► Highest Ammonia oxidizing bacteria to total bacteria population ratio observed at a C/N ratio of 9.3.