I was privileged to present at the 2010 Pumper & Cleaner Environmental Expo International in Louisville on operation and maintenance of aerobic treatment units. The presentation was on the basics, addressing the vast business opportunities in maintaining the many technologies emerging in our industry. In attendance were some seasoned O&M professionals, and they had good technical questions. So here is a follow-up for those who are dealing with a common problem.Why does it happen?One of the most common questions is how to deal with scum on the clarifiers. Sometimes the scum consistency is heavy and greasy, and sometimes it is
