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Staff reports measurable improvements to taste, odor and hardness after treatment changes and source-water shifts
Summary
Utility staff reported progress on taste, odor and hardness problems tied to the South and North reservoirs, including increased use of City Ditch source water, temporary ozone trailer treatment and longer-term solids removal through the centrifuge project.
City staff provided an informational update on efforts to reduce taste, odor and hardness in Englewood's drinking water and described operational, source-water and treatment changes that staff say are producing measurable improvements.
Peter (Director/Staff member) introduced the briefing and credited Zach Alabasi, the water treatment manager, and operations staff for stepwise process optimization at the Allen Water Treatment Plant. Staff emphasized that all treated water continues to meet federal and state safety standards (EPA and the Colorado Department of Public Health & Environment monitoring and testing), while focusing on aesthetic issues (taste, odor and hardness).
Key operational changes and findings: - Source-water blending: Staff increased use of City Ditch water from 47 percent of raw water in 2023 to 82 percent in 2024. Staff said City Ditch water, drawn upstream near Chatfield, carries fewer urban-runoff contaminants than the upstream Union Avenue diversion and thus improves source-water quality for the plant. - Ozone trailer pilot: An ozone system deployed on a trailer has been used to reduce taste-and-odor compounds (including geosmin and MIB) along the flow path between the South Reservoir and North Reservoir; staff supplied sample figures showing reductions (for example, a compound value moving from 66 to 5.1 in the pilot data cited by staff). - Solids removal: Staff reiterated the solids-handling project (centrifuge replacement) and the potential for a one-time reservoir drawdown and mechanical removal by front-end loaders if needed to accelerate clearing accumulated solids. Removing solids from the South Reservoir is central to limiting compounds that short-circuit back to the plant intake and contribute to taste and odor. - Distribution and tank operations: Staff increased targeted hydrant flushing and installed tank mixers to reduce stratification and stagnation in overhead tanks, which can contribute to localized taste and odor issues. - Hardness trends: Staff presented data showing a measurable reduction and stabilization of finished-water hardness after shifting source-water use; staff emphasized the change reduced variability and lowered peak hardness values compared with the prior year.
Board members asked about algae in the North Reservoir, nutrient inputs and treatment options. Staff said algae can release taste-and-odor compounds and that piping City Ditch (eliminating open-channel runoff inputs) should reduce nutrient inputs that fuel algae. Staff said they are evaluating monitoring and potential algae treatments, including ultrasonic systems, and will present cost-benefit options to the board if a treatment is recommended.
The board received the informational update; staff said they will provide periodic follow-ups and an annual check-in on progress.
