AWWA WQTC52996

Filtration is an essential process in drinking water treatment.Recent Cryptosporidium outbreaks have highlighted concerns about filter efficiency and in particular particle breakthrough. Breakthrough has been linked to the ripening stage, when up to 90% of the entire breakthrough occurs, due to poor removal, and also during flow rate changes. This study aims to expand upon this knowledge, specifically by determining when flow rate changes occur. Laboratory experimentswere conducted on a single filter column which had a starting flow rate of 5 m/h. Various flow increases were introduced instantaneously at different points during the filter run with each flow change being 30 minutes in duration, after which the flow was returned to the starting value. The results show that flow rate changes cause an increase in particle breakthrough. This effect is more pronounced with flow changes later on in the runs and with higher magnitude flow rate increases. Includes 9 references, table, figures.