a campaign to improve water quality in the ship canal and the mersey basin began in 1985, which had implications for the treatment works. the national rivers authority set limits on the volumes of biological oxygen, suspended solids and ammonia in any effluent discharged in water courses. north west water elected to try a new process called biostyr to meet these demands, and subsequently, water quality in the canal reached the class 2 standard, enabling coarse fish to thrive. the old secondary beds were declared a site of biological importance in 1985. north west water was privatised with the passing of the water act 1989. a pilot biostyr plant was built in 1992, costing £2 million, and following the merger of north west water with the north west electricity board (norweb) in 1995, a contract for the construction of a 36 cell biostyr plant was awarded. the project, costing £50 million, was completed in 1998.