Phosphorus removal prompts major dosing pump order

Tightening regulatory requirements on phosphorus removal have resulted in the largest ever order of Qdos ReNu chemical metering pumps for Watson-Marlow Fluid Technology Solutions (WMFTS).

The 240 pumps are required by process specialist Colloide Engineering Systems which has built 115 chemical dosing skids for site upgrades by Severn Trent Water (STW). Colloide says four or five versions of each chemical dosing rig and multiple setups may be required at a single site. In addition, Colloide placed a further order for 40 Watson-Marlow 630 series process pumps for the skid packages.

The skids are being used to deliver the UK utility’s phosphorous removal programme for AMP7, the regulatory asset management period 2020-25.

Phosphorus is a normal part of domestic sewage and new legislation in the European Water Framework Directive requires water utilities to meet much tighter environmental discharge limits to reduce the amount entering rivers and streams. The minimum total phosphorus consent level has been tightened to 0.25mg/litre, which means introducing a range of processes and techniques, and investing in new equipment.

Chemical dosing is one approach being used by water companies to meet the new phosphorus consent, and equipment needs to be flexible and multi-chemical compatible. This means a range of dosing pumps able to handle different chemicals used in flocculation and coagulation – including ferric, aluminium chloride and polymers – may be required for each skid.

The order from Colloide includes Qdos peristaltic pumps with three different flow rates – Qdos 30, 60 and 120. These dosing pumps offer repeatable flow up to 120l/hr and a maximum operating pressure of 7 bar, whilst metering accuracy is assured to ±1%. Unlike traditional diaphragm metering pumps, the flow remains the same whatever the pressure value which provides greater dosing control leading to tangible chemical savings.