AWC Provides Cleaning Solution For Ultrafiltration System at the Cincinnati Zoo

The Cincinnati Zoo uses an Ultrafiltration System (UF) to treat stormwater. The reclaimed water is collected from 14 acres of the park, including parking lots, animal exhibit yards, rooftop drains and walking path storm drains. Those sources are combined and run through a straining basin to a 300,000 gallon retention tank system. From there, the water is pumped from a wet well to the UF system, producing irrigation water and make-up water for various animal exhibits. These include underwater viewing of Polar Bears and Sea Lions, as well as moats for Lions, Cheetahs and African Painted Dogs.

The UF storm water recovery system was showing a drastic deterioration in product flow. A service company that was contracted performed an extensive cleaning. They first recirculated a competitor’s acid cleaner at a pH of 1.6 for two hours, followed by an alkaline cleaning at pH 12.8. The high pH cleaner was few more hours with a fresh alkaline solution at pH 12.4.

The system was finally cleaned with a second acid solution for another hour. The Transmembrane pressure (TMP) and flow did not recover to design values. Within a few days, the product flow started to decrease again until the UF system’s operation had to be completely halted.

The Cincinnati Zoo operations team requested AWC’s assistance in finding a solution to properly clean their UF elements. A cleaning study was performed and it was determined that a 2% solution of AWC UF-428, a high pH chlorinated cleaner, should be used at a pH 12.

The most effective cleaning protocol consisted of alternating forward and reverse circulations with soaking for a total of 6 hours.

These recommendations were implemented in cleaning the remaining modules. As a result, the UF membranes were revitalized with a 20 fold increase in flux and an 87% decrease in TMP.

AWC cleaning study enabled the Cincinnati Zoo to resume operation of the UF system at optimum performance, thereby allowing the zoo to handle the stormwater runoff.