北湖污水厂改良A^(2)/O膜生物池混合液回流系统优化

Optimization of Mixed Liquid Reflux System in Modified A^(2)/O Membrane Bioreactor of Beihu Wastewater Treatment Plant

北湖污水处理厂有40×10^(4) m^(3)/d规模的污水采用高浓度改良A^(2)/O生物池+MBR组合工艺处理。为充分发挥其污泥浓度高、节省占地、出水水质好、自动化程度高的优点,消除其受混合液回流方式限制引发回流条件不好而导致生物脱氮除磷效果差的弊端,该工程提出一种混合液回流系统的优化设计方案,即采用改良A^(2)/O生物池混合液导流/分流装置。该装置由分流导流板系统、混合液导入系统及混合液导出系统组成,通过对导入及导出点所在的同一平面位置进行竖向分隔,形成两个相对独立的空间,在不同高度空间内实现不同分区之间的混合液导入与导出,从而构建出高效的混合液回流系统。该解决方案构思巧妙,简单易行,可广泛应用于各种具有推流结构形式、同步脱氮除磷及多级回流需求的生物池中,例如UCT工艺、VIP工艺、A^(2)/O及其各种变形工艺。该装置可节约能耗,提高生物脱氮除磷效果,北湖污水厂混合液回流能耗为0.0017 kW·h/m^(3),节能50%~85%,平均脱氮率为73%,最高达93%。

A combined process consisting of high concentration modified A^(2)/O biological tank and MBR is applied for the treatment of 40×104 m^(3)/d wastewater in Beihu wastewater treatment plant.In this project,an optimal design scheme of the mixed liquid reflux system,namely a modified A^(2)/O biological tank mixed liquid diversion/distribution device,was proposed to make full use of its advantages of high sludge concentration,small footprint area,good effluent quality and high degree of automation,and eliminate the disadvantages of poor biological nitrogen and phosphorus removal caused by the limitation of bad mixed liquid reflux conditions.The device consisted of a diversion/distribution plate system,a mixed liquid introduction system and a mixed liquid discharge system.By vertical separation of the introduction and discharge points in the same plane position,two relatively independent spaces were formed,and the introduction and discharge of the mixed liquid between different zones were realized in different height spaces,so as to build an efficient mixed liquid reflux system.The solution is ingenious and simple,and can be widely used in various biological tanks with plug-flow structure,simultaneous nitrogen and phosphorus removal and multi-stage reflux requirements,such as UCT process,VIP process,A^(2)/O and its various deformation processes.The device can save energy consumption and improve the effect of biological nitrogen and phosphorus removal.The energy consumption of mixed liquid reflux in Beihu wastewater treatment plant is 0.0017 kW·h/m^(2),which saves 50%-85%energy.The average denitrification rate was 73%,and the highest denitrification rate was 93%.