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End elevation of RO Units

Reverse Osmosis Building

Introduction

This project involved the design, installation and commissioning a three-stream reverse osmosis water purification plant for the treatment of mains water from the Dalton Piercy WTW of Hartlepool Water, a process designed to achieve up to 85% permeate recovery. The ACWA treatment process replaced an existing demineralisation plant, and is part of a £1.1 million project installed to produce water for Hartlepool Water's industrial customer base.

Plant Description

Water from Hartlepool's Dalston Reservoir is delivered to the new plant via a double ring main. The water in the reservoir is drawn from 17 boreholes and contains relatively high levels of calcium and magnesium. The treatment plant is housed in a dedicated building sited within the industrial user's boundary.

The water is monitored for temperature, conductivity and pH before passing through a primary filtration system.

The incoming feed water is dosed with an antiscalant to prevent calcium carbonate and calcium sulphate deposition within the membrane array, and with neat sodium bisulphite, at 2mg/l to neutralise the 0.5 to 1 ppm free chlorine content. To allow bulk storage of chemicals, both dosing systems incorporate high capacity storage tanks.

The water feeds at 6 Bar mains pressure to the three treatment skids where cartridge filters remove any suspended solids greater than 5 microns in size.

The pressure is boosted to 20bar by Grundfos booster module pumps, these pumps including their motors are enclosed in a stainless steel tube as shown in the photograph below. The motor is water-cooled eliminating the usual noise created by a fan cooling system. The pump speed is controlled by the PLC via a variable speed drive to achieve a constant feed flow. The high pressure water feeds a 2 stage (8:4) membrane array. Each tube contains 7 x 8" diameter x 40" long membranes.

The concentrate pressure control valve operates under PLC control to achieve the correct concentrate flow thereby controlling the system recovery rate and permeate flow.

As the cartridge filters and RO membranes become progressively fouled, the pressure is automatically adjusted by the PLC, which allows the plant to function with limited operator attention. A central control panel and telemetry allows the client to check remotely on performance variables at any time.

Feedwater conductivity = 1,000 μs/cm. Conductivity of the permeate averages 18.5 μs/cm pH 6.5.

Side elevation of 1No of 3No RO Units

Chemical storage area