Blog-Projects
Cronulla Waste Water Treatment Plant
Sydney Water’s Cronulla WWTP was commissioned in 2001 to serve the catchment generally south and west of Botany Bay. It has five continuously aerated activated sludge reactors treating chemically dosed settled wastewater, and each reactor incorporates an anoxic zone. Each reactor has a volume of about 3,500m3 and a liquid depth of about 6.3m.
Each reactor is aerated by 300mm dia Nopon membrane diffusers set on fixed grids of PVC pipework, and there are 876 diffusers in each of the five tanks. There are six individual grids in each reactor, and air flow to each is independently regulated to maintain setpoint dissolved oxygen levels.
The plant was designed, built and originally operated by Australian Water Services, and its diffusers have been regularly tested and formic acid vapor dosed from the beginning by Tom Lawson’s former company Aqua-Audit. Largely as a result of this first-rate monitoring and maintenance regime, the original EPDM membranes gave almost 14 years of good service before they were replaced by Aer-Force in 2015.
The scope of work for this replacement work included supply and fitting of replacement Nopon membranes as well as all pipework joint seals and some broken couplings and diffuser retaining rings. This confined-space environment work was directed personally by Mike Young and three assistants, and was completed very satisfactorily using a special diffuser ring-removal tool imported by Aer-Force for this purpose from New Zealand.
The refurbished diffusers have now been in service for five years and, with the same acid vapour dosing regimen being maintained as before, can be expected to yield another ten years of good service. This plant has provided an object lesson in ‘gold standard’ diffuser testing and maintenance.
Tom Lawson (September 2020)