CRL Surveys was commissioned by Ward and Burke Construction Limited to assess the condition of four large circular concrete digesters (AD1 to AD4) at one of the large water companies water treatment Works (STW). These digesters, which had been in operation for approximately 50 years, are essential in the wastewater treatment process, had started to shown signs of degradation due to long-term exposure to aggressive chemicals and water. Concrete Repairs Limited Surveys task was to focus specifically on Digester AD1 and carry out a detailed inspection of its structural components, including the walls, base, and associated Limpit and Inlet Chambers.
During the inspection of AD1, several key issues were uncovered. Cracking was observed in both the base slab and upper walls, with evidence of water leaking through the cracks. The cracks appeared horizontally and vertically at the joints where the concrete was cast, and the presence of white mineral deposits (efflorescence) and water stains indicated ongoing seepage. The internal surface of the Limpit Chamber was also found to be deteriorating, with rough areas and rusting visible on the concrete surface.
In addition to inspecting AD1, various repair works were carried out on Digester AD4. These repairs involved addressing the cracks and damaged areas on the walls and base. To seal the cracks and prevent further water intrusion, a resin was injected into both the internal and external wall cracks. A Masterseal 930/933 overbanding system was then applied over the cracks to provide an additional layer of protection. All the old protective materials, such as the white Hypalon and brown bituminous overbanding were removed from the construction joints and replaced with the Masterseal 930/933 system to enhance durability and protect against future damage.
Given the demanding wastewater environment in which these digesters operate—where the concrete is continually exposed to harsh chemicals and water, - CRL recommended using long-lasting repair solutions and protective coatings designed to withstand these tough conditions. They further emphasized the importance of regular maintenance to preserve the integrity of the digesters and ensure their continued functionality over time.
The inspections and repairs conducted on AD4 effectively addressed the immediate structural concerns, while CRL findings highlighted the critical need for ongoing maintenance to prevent further damage. Ensuring that these digesters remain operational and efficient requires diligent care, which will help avoid future deterioration and extend their operational lifespan.
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