Technical description

Three of the four new works, at Halling, Charing and Goudhurst, treat iron-bearing groundwater. Treatment at each of these sites generally comprise aeration, sand filtration with automatic backwash, chlorine disinfection, washwater recovery and sludge thickening, with new plant as required.

Extensive monitoring and automatic control systems were installed and will include Motor Control Centres (MCC) and Human Machine Interface (HMI) units, chlorine residual monitoring and automatic shutdown, output and wastewater flow measurement, outlet turbidity monitoring and automatic shutdown systems.

Halling WTW

The original iron removal plant constructed in the mid -1960's had inadequate capacity, significant manual control and was unable to meet today's standards of efficiency and reliability. The original plant was demolished and replaced by a fully automated 4.0 Ml/d plant.

Charing WTW

Parts of the original works date from the late 19th Century and, whilst the plant had been periodically updated, operating and maintenance costs are high and the works did not provide sufficient reliability. The original plant was demolished and replaced by a fully automated 5.5 Ml/d plant.

Goudhurst WTW

The original water treatment plant was constructed in the late 19th Century. Substantial changes to the process had been made over the years however the process had high operating and maintenance costs and was not sufficiently reliable. Extensive consultation with local planning authorities was required to minimise visual impact of the new 10 Ml/d treatment plant.

Bewl Bridge WTW

The fourth treatment plant covered by the contract is Bewl Bridge WTW.The primary water source for the treatment works is Bewl Water, a large surface water storage reservoir. At periods of high demand the input is supplemented by a local groundwater source.

The original plant was constructed in 1980 and the existing 23 Ml/d treatment process includes screening, aeration, coagulation, flocculation, dissolved air flotation, ozonation, rapid gravity filtration (Granular Activated Carbon media), super and dechlorination.

In order to improve filtration and hence output water quality new GAC filters were constructed downstream of the existing filters, which in turn were refurbished and re-converted to sand media. The works also comprised all associated mechanical and electrical plant including monitoring and control equipment.