Abstract

This study measured the effect of low activated sludge dissolved oxygen (DO) concentration on a membrane bioreactor (MBR) treating real urban wastewater with respect to organic matter and nitrogen removal efficiency and transmembrane pressure evolution. For this purpose, a full-scale experimental pre-denitrification MBR system was operated at a constant permeate flow rate of Q = 0.45 m³h⁻¹ with intermittent aeration. The experimental installation worked at high hydraulic retention time, variable sludge retention time and with activated sludge temperatures of between 22.0 to 31.3 °C. Mean DO concentrations in the activated sludge were gradually decreased from 1.25 mgO₂L⁻¹ to less than 0.20 mgO₂L⁻¹. Variations in DO set points did not affect the main operational parameters of the MBR system and no clear relation was shown between DO concentration decrease and membrane fouling. At DO concentrations lower than 0.2 mgO₂L⁻¹, a deterioration in MBR effluent quality was observed, mainly with respect to chemical oxygen demand, biochemical oxygen demand at five days and NH₄⁺, however, the opposite effect was observed for NO₃^-. These results indicate that employing low DO set points is a promising strategy for application in MBR systems.

摘要

本研究测量了低活性污泥溶解氧 (DO) 浓度对处理实际城市废水的膜生物反应器 (MBR) 在有机物和脱氮效率以及跨膜压力演变方面的影响。为此，在Q = 0.45 m ³ h ^-1的恒定渗透流速下操作全尺寸实验预反硝化MBR 系统并间歇曝气。实验装置在高水力停留时间、可变污泥停留时间和 22.0 至 31.3°C 的活性污泥温度下工作。活性污泥中的平均溶解氧浓度从 1.25 mgO ₂ L ^-1逐渐降低到小于 0.20 mgO ₂ L^-1。DO 设定点的变化不会影响 MBR 系统的主要操作参数，并且在 DO 浓度降低和膜污染之间没有显示出明确的关系。在 DO 浓度低于 0.2 mgO ₂ L ^{-1 时}，观察到 MBR 出水水质恶化，主要是在化学需氧量、五天生化需氧量和 NH ₄ ^{+ 方面}，然而，对于 NO ₃观察到相反的效果^- . 这些结果表明，采用低 DO 设定点是在 MBR 系统中应用的一种有前途的策略。