Wessex Water operates just over 400 Sewage Treatment Works (STWs) across Somerset, Wiltshire, Bristol, Gloucestershire and Dorset. Combined, these STWs treat 480 million litres of sewage from 2.8 million customers every day.
One of the STWs is Poole Sewage Treatment works which treats incoming sewage from the Poole area, serving a population of 168,397 people. Final effluent is discharged into Poole Harbour. Some of the sewage treatment tanks within the plant were showing signs of corrosion and spalled concrete due to the chemical reaction of Hydrogen Sulphide (H₂S) which is highly corrosive. South West Concrete Repairs (SWCR) were tasked with refurbishing the tanks to return them to full use.
Flexcrete products were specified for this project as we could provide a full suite of concrete repair and waterproofing materials. SWCR first cleaned the tanks using high pressure power washing before all the defective concrete was broken out. Steel reinforcement was cleaned, treated and replaced where required.
Two Flexcrete concrete repair mortars were used for the repair work – Monomix HD and Monopour PC6. Monomix HD is a trowel applied, waterproof, class R4 structural repair mortar which has excellent low sag properties and can be applied up to thicknesses of 80mm in a single application. Monopour PC6 is a non-shrink, pourable micro concrete designed for large areas of concrete repair. These repairs allowed the walls of the tanks to be reinstated to their original profile.
The final stage of the works was to spray apply two coats of Cemprotec E942 to all walls and floors within the sewage treatment tanks. Cemprotec E942 is a waterborne, epoxy and cementitious modified coating which can be applied to damp substrates with far lower levels of surface preparation than conventional coating systems. It can be applied in confined areas, as it has a water-based, environmentally friendly composition and releases no hazardous solvents or heavy odour. E942 will provide additional chemical resistance and will significantly extend the life expectancy of the tanks.
The final stage of works was to apply a two full coats of a cementitious waterproof coating to all wall and floors within the tanks.