The Ballarat Prefermentor is the major fermentation tank of solid human waste for the regional city. Raw waste goes in, and begins the fermentation / reclaiming process. Because humans waste produces a highly concentrated amount of H2S gas, the acids, residues and chemicals contained in the waste react with concrete and destroy the integrity if not properly coated / protected. Within only 24 months of the commissioning this high capacity tank it had to be taken out of service due to the 300mm think walls being severely corroded.
Enter Asset Rehabilitation Services who specialize in protective coatings and repairs to concrete. Firstly the tank was drained and flushed , all surfaces were then sandblasted, scabbled, needle punched, ground and high pressure blasted back to sound concrete to remove residue and scaling. Once completely free of the acid effected concrete , ARS embarked on the rehabilitation process. The next process was to drill and crack inject the walls that had serve structural cracks with repair resins. What then followed was a series of preparation treatments complete with testing and evaluation by a supervising engineer. Steel work required different preparation and coating. Then came the spraying of PARCHEM ELS a two part coating that is specifically designed for use on surfaces in contact with raw sewage. A specialist product that requires specialist spray equipment and an exacting eye for quality assurance right down to temperature, dew point, humidity and UV conditions on the day/hour of application. Expert equipment and technicians are required to get this right.
The tank was in far worse condition then first thought. However it was given a new lease of life at a far lower cost than a new rebuild. Numerous problems were encountered during this project yet between the client and A.R.S all were resolved in a timely and cost effective way. The job was completed outdoors in arduous and at times extreme weather conditions, over a 16 week period. A rigorous fault test and independent report was conducted by supervising engineers (inspected and signed off at each hold point), no revisions or fails. All works were certified as being in accordance with manufacturers guidelines and to spec (report available on request).