Kemical Dosing Ltd supply and install two Liquid Lime Dosing Plants for Wessex Water

Taunton Ham STW was the first plant to be supplied. This contract was managed by Interserve Construction Ltd. The plant was specified to meet the client’s requirement for its AMP 6 Phosphorous Removal Scheme.

The plant was designed to make up the required liquid lime solution at the designated concentration and re-circulate it through a common ring main alternating from the two mixing/dosing tanks while supplying two dosing points through a point of application box. The plant delivered the lime solution to either or both dosing points when called for at a variable rate within the threshold settings of the upper and lower dosing rates.

Two tanks were used balancing the mixing rate to finish each designated duty mixing tank batch before the maximum dosing rate could empty the designated duty dosing tank. The tanks rotated between duty dosing and duty mixing thereby allowing a continuous dosing operation as required.

The plant was designed to provide:

  • Continuous unattended operation – 24 hours/day for 7 days/week;
  • Automatic control of the lime dosing operations to optimise lime usage;
  • Plant availability in excess of 95% based on continuous operation over a three-year period;
  • A design life of the plant in excess of 25 years.

Thornford STW was the second Liquid Lime Dosing Plant to be supplied, this contract was managed by Wessex Engineering & Construction Services Ltd. The plant was specified to meet the client’s requirement for their requirement to provide sufficient alkalinity for nitrification.

The plant was intrinsically similar to the Taunton Ham Lime Dosing Plant and only required adapting to the site-specific layout and dosing rates required at Thornford. This involved some changes in flow rates resulting in different re-circulation pumps, instrumentation and control being used. The plant layout also changed allowing for the allocated footprint for the plant and meetings to agree access.


These plants were engineered, built and installed by Kemical Dosing Ltd while sub-contracting their services to Singleton Birch Ltd.