The deal will see 800 MWH staff working across six major frameworks join RSK.
It is the latest water sector move for RSK following two years of significant investment with acquisitions including Water Research Council (WRc), Nicholas O’Dwyer and Binnies (formally the UK and Asia water businesses of Black & Veatch).
MWH Treatment will retain its leadership team, all employees and its 200-year-old brand.
MWH Treatment Managing Director, Paul Bresnan, said: “I am incredibly excited for MWH Treatment to be taking this fantastic next step. Being part of RSK will enable us to bring a broader and deeper offering to our clients by leveraging the wider group capabilities.”
“RSK really values our exceptional people along with the great relationships we have with our clients and joint venture partners,” he added.
Alan Ryder, RSK founder and chief executive officer, said: “The water sector is of huge importance to RSK and its strategy, so I couldn’t be more pleased to welcome MWH Treatment into the group. The company’s reputation across the UK is impeccable, and I see countless opportunities for collaboration and knowledge-sharing across the group.
“Paul and his team hold values very similar to those of the wider RSK group – something that I feel is so important in bringing businesses together.”