The Cloevis® Biofilm Removal System: Results from Early US Commercial Applications

Free Nitrous Acid (FNA) is the active agent underlying a new biofilm removal technology (“Cloevis”) for controlling sulfide production in wastewater force mains. The technology was developed at the University of Queensland and, after initial field testing in Australia, commercial field tests in the U.S. began in late 2015. These early test sites were chosen to reflect a range of force-main situations, including: short vs long retention times; small vs large wastewater flows; and force mains heretofore treated with nitrate, iron salts, or no treatment. In all cases, the Cloevis technology was able to bring the sulfide levels under target limits, although auxiliary (complementary) treatments are needed in two scenarios: where pre-existing sulfide enters the force main segment either through the influent flow or through a manifolded (interconnecting) force main; and where the candidate force main has accumulated deposits of fats, oils, and grease that coat and protect the biofilm. This paper will describe the Cloevis technology and discuss the results from three of the early field tests in the U.S.