Dissolved Air Flotation Treatment Performance in High Intensity Runoff Conditions

The removal of natural organic matter (NOM) removal in drinking water treatment is required to reduce theformation of disinfection by-products (DBPs) when the water is disinfected with chlorine. Trihalomethanes(THM) and haloacetic acids (HAA) are two classes of DBPs that have been shown to be carcinogenic and areprovincially regulated based on maximum acceptable concentrations (MACs) outlined in the CanadianDrinking Water Quality Guidelines. The removal of particles that contribute to turbidity in the source water isequally important in treatment, as elevated turbidity can reduce the efficiency of disinfection processes andindicate the presence of pathogenic organisms in drinking water supplies. In Atlantic Canada, surface watersused for potable water sources are generally characterized as low turbidity and alkalinity, with elevated colorlevels that represents the presence of NOM. Dissolved air flotation (DAF) is a clarification technology used toremove particles and coagulated organic material in drinking water treatment. Over the past 10 years, severalnew water treatment plants built in Nova Scotia to meet regulatory requirements have been based on DAFtechnology due to superior treatment performance for low turbidity, high colored source waters. The BrierlyBrook Water Treatment Plant (BBWTP) in Antigonish, Nova Scotia is similar in plant design to several othermunicipalities. These utilities are more prone to process upsets during storm events (i.e., intenseprecipitation/rainfall) which can rapidly deteriorate the source water quality to conditions not ideal for DAFtechnology (e.g., spikes in turbidity and color). However, guidelines for operating DAF systems duringextreme weather events do not exist, which have become more prominent over the last several years in AtlanticCanada. Several approaches to managing treatment efficacy during high intensity storm events will beevaluated in this study that focus on both coagulation chemistry and DAF operations. This research project willbenefit the drinking water treatment industry through investigations into optimal response protocols to maintainpotable water quality targets and alleviate rising operational costs during extreme weather conditions.