From August 23 – 26, I attended the IWA Specialized Conference on Biofilms in Drinking Water Systems. The conference was held in the beautiful Swiss town of Arosa, which is located in the Alps at an elevation of about 7,000 feet. The scenery was spectacular, as you can see from the pictures I took from the conference hotel. Each morning, I could go out for a vigorous and scenic walk from 6 to 7 AM. Not only was this great exercise, but it was a chance for me to get to know Arosa and relax my mind for the day’s activities.
The conference looked at “good” and “bad” biofilms. The good biofilms are the ones that we use in various biological processes to remove biodegradable contaminants. The main session of the conference featured a dozen talks on different aspects of aerobic biofiltration processes used to oxidize what is called “biological instability” in the water. Another name for biological instability is “electron donors,” and the key ones in drinking water are biodegradable organic matter, ammonium, ferrous iron, and manganese(II). I was very pleased to that biological instability and biofiltration have become internationally recognized in the drinking-water field. I first introduced the term biological instability in a 1984 JAWWA paper with Vernon Snoeyink. Thirty years later, it such common parlance that no one at the conference needed to mention that I had coined the term “once upon a time.”
I chaired a roundtable discussion on biological processes to reduce oxidized contaminants, such as nitrate, perchlorate, and selenate. Jess Brown of Carollo Engineers and Rob Nerenberg of U. Notre Dame joined me in introducing the topic and leading a lively discussion. Even though oxidized contaminants are at the core of research in the Swette Center, they had a low profile at the conference, except for my summary of our roundtable and two posters. I was glad to have the chance to open the eyes of most conference participants to the challenge of oxidized contaminants and that we have well-developed treatment options, such as the Membrane Biofilm Reactor.
For the “bad” biofilms, I learned a lot about two topics that are not in my normal field of vision, but are emerging as very important for drinking-water microbiology. The first is that the plumbing inside our homes and businesses – called premise plumbing – is where a lot of microorganisms grow and lead to health risks. Premise plumbing often has long periods of water stagnation, higher temperatures, corrosion, and loss of disinfectants. All of these lead to increased growth of biofilms that may harbor pathogens and that always lead to water-quality deterioration, such as taste, odor, and turbidity. The second topic is about the increasing occurrence of two opportunistic pathogens: Legionella and mycobacteria. Some intriguing facts I learned are that they can develop resistance to chlorine, are promoted by copper piping, and cannot be eliminated by physical cleaning or heavy chlorination. The greatest risk comes from inhaling them as aerosols, such as from showers and misters.