The use of membrane bioreactors (MBRs) in activated sludge wastewater treatment has grown significantly in the last decade. While there is growing awareness and knowledge about the application of MBR technology in municipal wastewater treatment, not much information is available on the application of MBRs in industrial wastewater treatment. A comparative study of design data, operating conditions and the major challenges associated with MBR operations in 24 MBR plants treating both municipal and industrial wastewater, built by and/or operated by Praxair, Inc., is presented. Of the 24 MBR systems described, 12 of the plants used high purity oxygen (HPO). By enabling a wide range of food/microorganism ratios and loading conditions in the same system, HPO MBR systems can extend the options available to industrial plant operators to meet the challenges of wide fluctuations in organic loading and footprint limitations. While fouling in industrial MBR systems can be an issue, adequate flux and permeability values can be reliably maintained by the use of good maintenance strategies and effective process controls (pretreatment, cleaning and membrane autopsies).

An ozonation process was adopted for use in the full scale decolorization of the effluent from a High purity oxygen (HPO) activated sludge biological industrial textile wastewater treatment process. Prior to the adoption of the ozonation process, about 40% color removal was achieved through the biological process while the rest of the color removal was obtained through a tertiary, physical-chemical flocculation and coagulation process. Although the process was effective in removing color, large quantities of inert sludge were generated, making up as much as 60% of the total sludge from the plant. The cost for handling this sludge and for the purchase of the chemicals required for the Flocculation & Coagulation process was significant. The ozone based decolorization process has been effective in meeting effluent targets of 200 mg/l Pt-Co color and 50 NTU. The residual gas stream from the ozonation process comprising about 3.5% ozone (w/w) and about 2.5 metric tons/day of recovered oxygen is recycled back to the biological basin. The reuse of the vent gas stream from the contactor provides about 70% of the oxygenation demand at the facility. This type of recycle scheme which leverages the O 2 content in the vent gas stream for supplementing the O 2 demand in the biological basin has been implemented at a number of SAWM operated wastewater facilities, and is an effective tool for ensuring cost effective operations when ozone is used as an oxidizing agent in biological wastewater treatment systems.

Bubble column tests were conducted to compare the efficiency of ozone tertiary color removal for conventional activated sludge (CAS) gravity clarified effluent, sand filtered CAS effluent and immersed membrane bioreactor (iMBR) effluent. The ozone requirement to achieve the 200 mg/L platinum-cobalt color units (CU) target for the iMBR system was 26% that of the CAS system. The requirement for the sand filtered effluent was 42% of the CAS effluent. The lowest cost system was sand filtration, with a 18% savings compared to the base case.

The use of Membrane Bio-Reactors (MBR) in activated sludge wastewater treatment has grown significantly in the last decade. While there is growing awareness and knowledge about the application of MBR technology in municipal wastewater treatment, not much information is available on the application of MBR in industrial wastewater treatment. A comparative study of 24 MBR plants both municipal and industrial built by, and or operated by Praxair Inc. is presented. Of the 24 MBR systems described, 12 of the plants use high purity oxygen (HPO). By allowing a wide range of F/M ratios and loading conditions in the same system, HPO MBR systems can extend the options available to plant operators for impacting process variables as MLSS. While fouling can be an issue, adequate flux and permeability values can be reliably maintained by the use of good maintenance strategies and effective process controls (pretreatment, cleaning and membrane autopsies).

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