Microfiltration water reuse

The El Segundo, CA, Chevron refinery takes a further step in water reuse [76]. It receives 16,300 m /day of reclaimed water to feed its boilers. Microfiltration (ME) and RO are used to treat secondary effluent from the Hyperion Wastewater Treatment Plant to provide low-pressure boiler feedwater while a second pass RO is used to produce high-pressure boiler feedwater. 

Silva CM, Reeve DW, Woodhouse KA, Husain H, and Behmann H. Water reuse in the pulp and paper industry Evaluation of four microfiltration apphcations. Can. Pulp Pap. 1999 100(5) 38 3. 

Microfiltration and Ultrafiltration are the best available technology for water reuse. Two options are available conventional activated sludge followed by tertiary filtration and an integrated membrane bioreactor. Both provide effluent of high quality suitable for treatment by reverse osmosis. The cost of tertiary filtration can be lower than a membrane bioieactor if the water reclamation plant is designed for constant flow and is located at a different site. 

A complete process scheme for regeneration and reuse of spent final rinse water from an electroless plating operation has been developed by Wong et al. [105]. It includes (i) pre-treatment by microfiltration, UV irradiation, carbon adsorption (ii) heavy metal removal by nanofiltration and (iii) polishing using an ion exchange mixed bed. The results of a pilot study showed that high quality product water with an overall water recovery of 90% could be produced with an estimated payback period of less than 18 months. 

Micro-, ultra-, and nano-filtration can separate smaller particles using media with defined porous sizes (i.e., 10 1—1 pm in microfiltration, 10 2—10 pm in ultrafiltration, and 10 3— 10 2 pm in nanofiltration). Residual colloidal and suspended solids can be removed by microfiltration. Selected salts, most organic compounds, bacteria, protozoan cysts, oocysts and viruses are removed by nanofiltration, so that the treated water will be disinfected. This advanced filtration is used for the treatment of effluents for indirect potable reuse applications such as groundwater injection, water softening, decoloriza-tion, or removal of micropollution. 

Some areas of application are the nuclear industry and the treatment of radioactive liquid wastes, with two main purposes reduction in the waste volume for further disposal, and reuse of decontaminated water. Pressure-driven membrane processes (microfiltration, ultrafiltration, nanofiltration, and reverse osmosis [RO]) are widely used for the treatment of radioactive waste. 

This chapter, in addition to surveying membrane types and production, overviews applications of gas and liquid membrane separation and polymer films as banier layers. Water purification for reuse and in desalination using reverse osmosis and nano-, ultra-, and microfiltration are discussed. Electrodialysis, dialysis, and hemodialysis are also covered. Membranes in emerging technologies are described including fuel cell membranes, membranes in lithium batteries, conducting polymer membranes, and thin film membranes used in LED and photovoltaic applications. 

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