This is the third in a series of articles about the major upgrades that OCWA—Central New York’s Water Authority—is making to its Lake Ontario Water Treatment Plant (LOWTP) over the next several years. This article discusses the piloting phase of the project which is currently ongoing.
Defining the most appropriate process modification(s) to be incorporated into the design upgrades will be heavily dependent on the results from the comprehensive ongoing bench and pilot scale studies. The upgrades under consideration include (i) installing settling equipment to convert the existing contact basins to sedimentation basins, (ii) improving settling and contact time by removing aged equipment from and adding baffles to the existing contact basins, and (iii) potential modifications to the media filters to improve overall filtration performance.
Processes (i) and (ii) are two different ways to achieve the same objective of improving coagulation/settling performance. These options are being considered to enhance the facility’s ability to respond effectively to potential increases in turbidity and solids loading which can occur as seasons change and large weather events cause variability in the lake. Process (iii) is a potential upgrade considering the age of the existing filter systems. However, process (iii) would need sufficient justification for its implementation, given how well the current filtration system has been working in terms of filter run times and filtered water quality. To evaluate the three processes a combination of bench scale and pilot scale testing is taking place.
Bench testing is being performed to refine the conditions to be tested during the pilot. The facilities’ existing polyaluminum chloride (PACL) coagulant has historically produced excellent results, but this is the opportune time to test other coagulants and/or polymers to evaluate the potential benefits. Additionally, bench scale testing will validate if the conceptual coagulation/settling modifications have potential or if the raw water quality is not conducive to them. Finally, it will ensure that the pilot scale testing is based on informed decisions regarding the apparent performance of the various treatment chemicals and process basin configuration by reducing the complexity of the pilot and allowing for focused effort on the most probable alternatives.
The pilot scale testing is being conducted over a minimum of three (3) two-week testing events, spread over three seasons (winter, spring, summer) to capture as much as possible the impact of seasonality on the results. Including a testing event during winter will be necessary, as it is expected that the performance under cold temperatures will produce the most challenging treatment scenario, which will be used as the basis for a conservative design of the upgrades. The subsequent seasonal testing will validate the treatment process stability under changing water temperature, conductivity, and turbidity.
(Pilot Scale Filtration System)
(Scale contact basin)
(Operating Pilot Scale Filtration System)