From the (Water Environment Federation (Jeanette Brown):
One hundred years ago this year, H. W. Clark and S. De M. Gage from the Lawrence Experiment Station in Massachusetts reported results of studies on the purification of sewage using aeration in the 45th Annual Report to the State Board of Health of Massachusetts. They found that if you aerated sewage, you achieved a clarified sewage and a reduction of Total Kjeldahl Nitrogen. A year later, 1914, a team of British researchers, Edward Ardern and W.T. Lockett, added the concept of recycling sludge, patented the process, and published a paper which first used the term “Activated Sludge.” As we reflect on these past hundred years, we can truly realize the power of these discoveries.
While a few plants adopted the activated sludge process early on, its value was not recognized for many years. In fact, the activated sludge process was not implemented in many cities throughout the United States until after the Clean Water Act in 1972. Over the years, we have modified the process, improved upon it, made it more efficient, and used it to remove nitrogen and phosphorous as well as carbon. Moreover, we have come to understand the process on a microbial level, its complexity and power. I am still overwhelmed when I visit a treatment plant and see the quality of effluent that this amazing process can achieve.