Water Treatment Costs Cut By Automation

All process in Anglian Water's Belstead treatment works near Ipswich have been automated by the installation of control equipment with remote monitoring capability, on-screen display of the entire operation and the ability to save electricity by switching between the local grid and a standby generator. Designed and manufactured by Max Wright Limited, the motor control centre and desks are among the most modern in the water industry today.

The treatment works, originally designed in the 1950s with some degree of automation, could not latterly be relied upon to operate unattended for even one day. The old wash-water pump was unreliable and spares were difficult to obtain and expensive. Anglian Water spent 250,000 pound modernising the pump house as part of a wider upgrade of the M & E (mechanical and electrical) infrastructure in the area.

Work was completed with no disruption to drinking water supplies. This was tribute to the engineering team, as Belstead is an important facility with a dedicated main to Stonelodge reservoir, one of only two feeding Ipswich and surrounding areas. At any one time the station can be pumping 120 litres of treated water per second, upto 20 per cent of total demand in the area.

The works technician in charge of this and other Anglian Water sites in the area, commented that 'Belstead used to be a manually intensive works. For instance, the filters needed to be cleaned every day for safety as we could not check the head loss. Now they are backwashed automatically every thrid day and as we are so confident about the control of the whole process we do not even have to use the head loss detection facility. We opt instead for time function control with the proviso that turbidity will also shutdown the filters.'

It also used to be difficult to control the level of treated water in the contact tank, which was described as 'very hands on'. Today the level is set at 80 per cent of capacity and the flows in and out of the tank are matched automatically to maintain the level. It is perhaps this performance which has impressed Anglian Water's management most, as it is a gauge of how accurately the entire plant is being run.

Now the treatment works operates completey unmanned and engineer attendance on site is reduced to the statutory minimum of three half hour visits per week to check the integrity of the building and glance at the mimic screen of the plant on the Max Wright Ltd. Control desk. The current one and half hours' weekly attendance contasts with four hours five days a week plus some weekend working previously needed to keep the old plant running. Labour savings are therefore considerable and will quickly amortise the investment in the new control equipment.

Control is provided by three modular PLCs, with PID loops, connected via a network to a computer running SCADA software for plant monitoring and control. Advanced facilities include remote monitoring capability and on-screen display of the entire operation. All plant communication with telemetry is via RS232 link including the chlorination system which is PLC controlled and hardwired as a safety backup. An advanced feature of the installation is the TRIAD system which cuts electricity bills by automatically switching the plant to run on a standby generator at times of peak power demand.

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