An ecological study of the Bromley oxidation ponds and surrounding environs.
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Since the early 1880's the Christchurch Drainage Board has discharged domestic and industrial sewage into the Estuary of the Avon and Heathcote Rivers at Bromley. From 1962 up to 30 million gallons per day of treated sewage have been discharged from a purification installation designed to give primary and secondary treatment, including a period of retention within a series of oxidation ponds. During this same period the estuarine waters have become increasingly enriched with nitrogen and phosphorus nutrient, resulting in extensive growths of macrophytic green algae (collectively termed sea lettuce) on the tidal flats. A greatly increased sewage flow from the treatment plant has undoubtedly contributed considerably to this accelerated eutrophication, and in 1968 the Christchurch Drainage Board instigated an investigation into the problem. The scope of this inquiry was widened in 1970 with the establishment of the Estuarine Research Unit attached to the Zoology Department, University of Canterbury, following the Drainage Board's receipt of a contracted report into flood alleviation in the Avon-Heathcote Estuary from the Hydraulics Research Station, Wallingford, England (hereafter referred to as the "Wallingford Report").