AWWA JAW69262

When designed and operated properly, slow-rate biological filters (e.g. slow sand or riverbank filters) are successful at removing pathogens such as Escherichia coli for drinking water treatment. However, the exact mechanisms involved with pathogen removal in the schmutzdecke have not been well-defined. A better understanding of the removal mechanisms at work in biofilters will allow engineers to design more effective filters and allow operators to improve performance by creating conditions amenable to the most important removal mechanisms. Water suppliers can use the findings reported in this article to improve the performance of existing biofilters by adjusting operations in ways that increase biofilm growth and activity and protistan activity in the schmutzdecke. They can also structure pilot studies to improve design or operation by focusing on the removal mechanisms presented in the article. It is hoped that the information in this article will encourage suppliers to consider biological filtration as an alternative to other treatment technologies for meeting regulatory standards or their internal water quality goals. Includes 29 references, tables, figures.