The scope of works under the phase 6 contract includes the installation of a new treatment unit, for use with an activated sludge process; demolition of certain facilities built under the first phase; relocation of a pipe rack; new inlet works; construction of a pumping station and a substation; and related civil, mechanical and electrical works. The consultant is the UK's Halcrow Group.

Seven contracting groups were prequalified to bid for the phase 6 contract. Among the prequalifiers was the local affiliate of Belgium's Six Constructwith the UK's Paterson Candy International, which carried out the third, fourth and fifth-phase expansions of the plant (MEED 7:5:99).