Technology Briefing

Benefits of RO Brine Recycle In Power Stations

By Michael Chan, P.E.

MEMBRANES MICROFILTRATION POWER RECYCLING REUSE REVERSE OSMOSIS WASTEWATER ZERO LIQUID DISCHARGE

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Abstract

Reverse Osmosis (RO) is a very common filtration technology employed in power plants for production of high-purity water. Because of the large volume and complex chemical characteristic of the RO brine wastewater produced, in the recent years, the power industry faces major regulatory, environmental, and economic challenges in the management of this by-product. The ever-increasing demand for clean water coupled with the limited RO brine disposal options led to the improvement of membrane technology for recycle and reuse of this wastewater stream.

This article will explore the dilemma and challenges that need to be recognized and overcome by the power industry in managing brine wastewater generated from the desalination process. The discussion will outline the role of tubular membrane microfiltration and the associated pretreatment chemistry as a viable approach to address the RO brine management concerns. A case study with detailed design and operation data is presented for a combined-cycle power station on the west coast where a membrane-based zero-liquid discharge (ZLD) system for RO brine recycling has been in operation for 5 years.

Introduction

Steam from water is the primary driving force for every power station. Electric power plants using different fuels, including coal, gas, oil, or nuclear, create steam that turns a turbine to produce electricity. The electricity generation process requires and consumes large volumes of high-purity water for boiler make-up and for cooling. Sources of water supply can vary from these sources: local water treatment plants, effluent from a local Publicly Owned Treatment Works (POTW), groundwater, and a nearby river or lake.

Each water source has unique characteristics, including organic material, dissolved minerals, microorganisms, and chemical contaminants. Each of these inherent characteristics can cause difficulties in a power plant. Therefore, the water has to be treated to minimize potential problems, since these problems could often result in either reduction of plant efficiency, or large capital costs. Those challenges are further compounded by the increasingly complicated contaminants found in raw water from various sources.

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Revised toray june 18.upm digital

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