State key Laboratory of urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China; School of Environment, Harbin Institute of Technology, Harbin 150090, China.
State key Laboratory of urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China; School of Environment, Harbin Institute of Technology, Harbin 150090, China.
Water Res. 2022 Sep 1;223:118961. doi: 10.1016/j.watres.2022.118961. Epub 2022 Aug 7.
This study investigated the trade-off between energy saving and NO emission reduction of WWTP under the precise control of dissolved oxygen (DO) concentration through model simulation. A long-term dynamic model for full-scale WWTP GHG emissions was established and calibrated with monitored year-round hourly water quality data to quantify the annual GHG emissions from WWTP. Results showed that NO dominated the direct emission, up to 76.1%, and the variability of NO generation could better be revealed by dynamic simulation. Furthermore, GHG emissions of the WWTP were mainly contributed by electric energy, among which the blower consumes the most electricity. To reduce the electricity consumption of blowers, improve mechanical efficiency and reduce DO concentration should be considered. DO setting played a significant role in the NO and CH emission, electricity consumption and effluent quality, which was challenging to balance. The ultralow-oxygen (0-1/0.2-1 mg/L) and low oxygen (1-2 mg/L) control strategies were proposed, and their effects on total GHG emissions and effluent water quality were discussed. If the anaerobic environment (DO<0.2 mg/L)could be avoided, the control frequency (high and low) of the DO set-point did not have a significant effect on the emissions of NO and CH and the effluent quality. The ultralow-oxygen strategy (0.2-1 mg/L) with a high-frequency control strategy achieved the lowest GHG emissions under the current energy mix. However, by 2050, as the energy supply gets cleaner, the total GHG emissions of WWTPs with ultralow-oxygen aeration (0.2-1 mg/L) will exceed low-oxygen aeration by 3.6%-4.2%, as NO dominates 61.6%. Therefore, considering the trade-off between NO emission and energy saving in WWTP, ultralow-oxygen aeration is a transition scheme to cleaner energy.
本研究通过模型模拟，探究了在精确控制溶解氧（DO）浓度的条件下，污水处理厂（WWTP）在节能与减少 NO 排放之间的权衡。建立了一个全面的 WWTP 温室气体排放长期动态模型，并使用全年每小时水质监测数据进行了校准，以量化 WWTP 的年度温室气体排放。结果表明，NO 占直接排放的主导地位，高达 76.1%，通过动态模拟可以更好地揭示 NO 生成的变化性。此外，WWTP 的温室气体排放主要由电能贡献，其中鼓风机消耗的电量最多。为了减少鼓风机的耗电量，应考虑提高机械效率并降低 DO 浓度。DO 设置对 NO 和 CH 排放、电力消耗和出水水质有重要影响，需要在其中进行平衡。提出了超低氧（0-1/0.2-1mg/L）和低氧（1-2mg/L）控制策略，并讨论了它们对总温室气体排放和出水水质的影响。如果可以避免厌氧环境（DO<0.2mg/L），则 DO 设定点的控制频率（高和低）对 NO 和 CH 的排放以及出水水质没有显著影响。在当前能源组合下，采用高频控制策略的超低氧策略（0.2-1mg/L）实现了最低的温室气体排放。然而，到 2050 年，随着能源供应变得更加清洁，超低氧曝气（0.2-1mg/L）的 WWTP 的总温室气体排放量将比低氧曝气增加 3.6%-4.2%，因为 NO 占主导地位，达 61.6%。因此，考虑到 WWTP 中 NO 排放与节能之间的权衡，超低氧曝气是一种向更清洁能源过渡的方案。
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