Membrane Bioreactors for Industrial Wastewater Treatment: Applicability and Selection of Optimal System Configuration

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Courtesy of Water Environment Federation (WEF)

ABSTRACT
The membrane biological reactor (MBR) configuration has proven to be optimal for treatment of many industrial wastewaters when treatment efficiency is an important consideration. Since installation of the first large, U.S., full scale MBR system for industrial wastewater treatment at the General Motors plant in Mansfield, Ohio in the early 1990s, use of membranes for biomasseffluent separation in biological systems has gained wide appeal both in this country and internationally. Industrial applications have ranged from nitrogen removal from food processing wastewaters to use of the technology to deal with complex organics in wastewaters originating from the production of pharmaceuticals and the manufacture of polymeric membrane materials. Historically, low membrane flux, low permeability, limited membrane life and high membrane costs hindered broad application of the MBR technology. The membrane industry, including independent research and development organizations and system suppliers, invested considerable effort to overcome these limitations over the past decade. The result has been a dramatic increase in the number of new commercial system embodiments of the MBR configuration offered by suppliers and a rapid acceleration in the use of the technology for treatment of industrial wastewaters and other aqueous streams.

MBR systems can be categorized according to the location of the membrane component. Until recently, the immersed or internal membrane MBR was typically more cost-effective than the external membrane MBR particularly in the treatment of larger wastewater flows. The technical advantages of the external membrane configuration, and recent significant membrane and system design advances resulting in reductions in operating power costs, have translated to broader application of this configuration. External membrane MBRs have recently been designed to treat wastewater flows as high as 3785 m3/day.

INTRODUCTION
The ideal bioreactor configuration for treatment of organic (e.g., measured as COD) or inorganic (e.g., ammonia, nitrate) contaminants present in industrial wastewaters will operate efficiently (i.e., at a high contaminant volumetric removal rate) while achieving the design performance objective (i.e., contaminant percent removal or effluent quality requirement). Bioreactor systems such as the conventional activated sludge system, sequencing batch reactor system and trickling filters although typically designed for operation at a lower volumetric removal rate, are often selected for applications under site conditions where space constraints are not a factor and/or other conditions which render the systems acceptable. The membrane biological reactor (MBR) configuration has proven to be optimal for treatment of many industrial wastewaters when treatment efficiency is an important consideration.

Since installation of the first large, U.S., full scale MBR system for industrial wastewater treatment at the General Motors plant in Mansfield, Ohio in the early 1990s (Knoblock et al., 1994), use of membranes for biomass-effluent separation in biological systems has gained wide appeal both in this country and internationally. Industrial applications have ranged from nitrogen removal from food processing wastewaters to use of the technology to deal with complex organics in wastewaters originating from the production of pharmaceuticals and the manufacture of polymeric membrane materials. Historically, low membrane flux (i.e., permeate production per unit of membrane area), low permeability (i.e., flux per unit of transmembrane pressure or TMP), limited membrane life and high membrane costs hindered broad application of the MBR technology. The membrane industry including independent research and development organizations and system suppliers, invested considerable effort to overcome these limitations over the past decade. The result has been a dramatic increase in the number of new commercial system embodiments of the MBR configuration offered by suppliers, and a rapid acceleration in the use of the technology for treatment of industrial wastewaters and other aqueous streams.

The purpose of this paper is to provide a general procedure for determining when the MBR configuration is optimal for treatment of an industrial waste stream and a framework for selecting the optimal commercial MBR system embodiment. The approach will be illustrated by full scale case studies.

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