Performance of anaerobic denitrifying upflow anaerobic sludge bed bioreactor (AD-UASB)

Nitrate-containing wastewater has a severely negative impact on the ecological environment, and anaerobic denitrification process is promising biotechnology for nitrate-containing wastewater treatment. The nitrogen removal performance of anaerobic denitrifying upflow anaerobic sludge bedbioreactor (AD-UASB) and granular sludge characteristics were investigated. The results showed the maximum nitrogen removal loading rate (NRR) was reached up to 28.6 kg/(m³·d) as nitrogen loading rate (NLR) was 28.8 kg/(m³·d). At the same time, the effluent NO₃⁻-N concentration and total nitrogen removal efficiency of AD-UASB was 5.09 mg/L and 99.51%, and the effluent NO₂⁻-N concentration was as low as 10.97mg/L without obvious accumulation. As NLR was elevated to 36 kg/(m³·d), the effluent NO₃⁻-N and NO₂⁻-N concentration were sharply increased to 199.62mg/L and 453.13mg/L, respectively, Thus, the denitrifying metabolic pathway was strongly suppressed which further led to the accumulation of NO₂⁻-N concentration and the collapse of AD-UASB performance. The granular sludge was broken up and washed out from the reactor, and meanwhile, the concentration of MLSS and MLVSS were declined to 55.09g/L and 24.7g/L, respectively. The research can provide a beneficial reference for the anaerobic denitrification biotechnology application in nitrate-containing wastewater treatment.