the bristol-based russell contracting company were awarded the contract for the new plant, and work started in october 1930 on a site located to the north east of the septic tanks. it would use three operating systems, with the majority of the flow using an air diffusion process, developed in-house. in order to allow comparisons to be made, two small sections would use the surface aeration or "simplex" system, and the bio-aeration or "sheffield" system, developed by john haworth at blackburn meadows sewage works in sheffield. a celebration dinner was held at manchester town hall on 15 may 1935 to mark the official opening of the new plant. the process was more efficient than the bacteria bed system, covering a much smaller area for the same volumes of sewage, and being largely automatic, used a lot less labour.