Comparison of the MBBR denitrification carriers for advanced nitrogen removal of wastewater treatment plant effluent

Yuan, Quan; Wang, Haiyan; Hang, Qianyu; Deng, Yangfan; Liu, Kai; Li, Chunmei; Zheng, Shengzhi

Comparison of the MBBR denitrification carriers for advanced nitrogen removal of wastewater treatment plant effluent

2015

The moving bed biofilm reactors (MBBRs) were used to remove the residual NO₃ ⁻-N of wastewater treatment plant (WWTP) effluent, and the MBBR carriers for denitrification were compared. The results showed that high denitrification efficiency can be achieved with polyethylene, polypropylene, polyurethane foam, and haydite carriers under following conditions: 7.2 to 8.0 pH, 24 to 26 °C temperature, 12 h hydraulic retention time (HRT), and 25.5 mg L⁻¹ external methanol dosage, while the WWTP effluent total nitrogen (TN) was between 2.6 and 15.4 mg L⁻¹ and NO₃ ⁻-N was between 0.2 and 12.6 mg L⁻¹. The MBBR filled with polyethylene carriers had higher TN and NO₃ ⁻-N removal rate (44.9 ± 19.1 and 83.4 ± 13.0 %, respectively) than those with other carriers. The minimum effluent TN and NO₃ ⁻-N of polyethylene MBBR were 1.6 and 0.1 mg L⁻¹, respectively, and the maximum denitrification rate reached 23.0 g m⁻² day⁻¹. When chemical oxygen demand (COD)/TN ratio dropped from 6 to 4, the NO₃ ⁻- N and TN removal efficiency decreased significantly in all reactors except for that filled with polyethylene, which indicated that the polyethylene MBBR can resist influent fluctuation much better. The three-dimensional excitation–emission matrix analysis showed that all the influent and effluent of MBBRs contain soluble microbial products (SMPs)-like organics and biochemical oxygen demand (BOD), which can be removed better by MBBRs filled with haydite and polyethylene carriers. The nitrous oxide reductase (nosZ)-based terminal restriction fragment length polymorphism (T-RFLP) analysis suggested that the dominant bacteria in polyethylene MBBR are the key denitrificans.

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