Ramphao M, Wentzel M C, Merritt R, Ekama G A, Young T, Buckley C A
Water Research Group, Department of Civil Engineering, University of Cape Town, Republic of South Africa.
Biotechnol Bioeng. 2005 Mar 20;89(6):630-46. doi: 10.1002/bit.20311.
Installing membranes for solid-liquid separation into biological nutrient removal (BNR) activated sludge (AS) systems makes a profound difference not only in the design of the BNR system itself, but also in the design approach for the whole wastewater treatment plant (WWTP). In multizone BNR systems with membranes in the aerobic reactor and fixed volumes for the anaerobic, anoxic, and aerobic zones (i.e., fixed volume fractions), the mass fractions can be controlled (within a range) with the interreactor recycle ratios. This zone mass fraction flexibility is a significant advantage in membrane BNR systems over conventional BNR systems with SSTs, because it allows for changing of the mass fractions to optimize biological N and P removal in conformity with influent wastewater characteristics and the effluent N and P concentrations required. For PWWF/ADWF ratios in the upper range (f(q) approximately 2.0), aerobic mass fractions in the lower range (f(maer) < 0.60), and high (usually raw) wastewater strengths, the indicated mode of operation of MBR BNR systems is as extended aeration WWTPs. Although the volume reduction compared with equivalent conventional BNR systems with secondary settling tanks is not as large (40% to 60%), the cost of the membranes can be offset against sludge thickening and stabilization costs. Moving from a flow-unbalanced raw wastewater system to a flow-balanced (f(q) = 1), low (usually settled) wastewater strength system can double the ADWF capacity of the biological reactor, but the design approach of the WWTP changes from extended aeration to include primary sludge stabilization. The cost of primary sludge treatment then has to be paid from the savings from the increased WWTP capacity.
在生物营养物去除（BNR）活性污泥（AS）系统中安装用于固液分离的膜，不仅会对BNR系统本身的设计产生深远影响，而且会对整个污水处理厂（WWTP）的设计方法产生深远影响。在好氧反应器中设有膜且厌氧、缺氧和好氧区体积固定（即固定体积分数）的多区BNR系统中，通过反应器间的循环比可以（在一定范围内）控制质量分数。与具有SSTs的传统BNR系统相比，这种区域质量分数的灵活性是膜BNR系统的一个显著优势，因为它允许改变质量分数，以便根据进水废水特性和所需的出水氮磷浓度优化生物脱氮除磷。对于较高范围的原水/厌氧消化水比例（f(q)约为2.0）、较低范围的好氧质量分数（f(maer) < 0.60）以及高（通常为原水）废水强度，MBR BNR系统的所示运行模式为延时曝气污水处理厂。尽管与具有二次沉淀池的等效传统BNR系统相比，体积减少幅度没有那么大（40%至60%），但膜的成本可以与污泥浓缩和稳定成本相抵消。从流量不平衡的原废水系统转变为流量平衡（f(q)=1）、低（通常为沉淀后）废水强度系统，可以使生物反应器的厌氧消化水容量翻倍，但污水处理厂的设计方法从延时曝气转变为包括初沉污泥稳定化。然后必须用污水处理厂容量增加所节省的费用来支付初沉污泥处理的成本。
