Advanced Process Options for Persistent Taste and Odor at the Ni River Water Treatment Plant
- Aaron Duke, Chris Edwards, Erik Rosenfeldt, Meric Selbes
Like most reservoir supplies, the Ni River Reservoir provides good, stable water quality, but can experience periods of high algae in summer and high iron and manganese levels during reservoir turnover, with accompanying taste and odor changes. The Ni River WTP experienced an extended taste and odor (T&O) event during one of these turnover periods. A study was undertaken to identify the nature of the T&O in the Ni River Reservoir, and to identify appropriate treatment options for reducing the odor(s) at the Ni River WTP.
Four sampling events were conducted between April 2013 and April 2014 and the samples were analyzed for inorganic sulfur compounds, flavor profile analysis and MIB/geosmin. Sampling results suggested that the observed tastes and odors were Earthy/Musty associated with MIB and/or geosmin from Bluegreen algae (cyanobacteria), and Swampy/Marshy/Sulfur associated with the low dissolved oxygen conditions as the bottom of the reservoir.
While the treatment process at the Ni River WTP is capable of lowering odor in the finished water under normal to low raw water odor conditions, algae related products and organic odors present a potentially greater challenge. To mitigate the T&O episodes, several treatment alternatives were evaluated including reservoir aeration/mixing, activated carbon, ozone and UV-peroxide. While reservoir aeration/mixing methods can alleviate some T&O concerns, this strategy alone may not address T&O episodes. Preliminary analysis has indicated that oxidation with ozone will likely be more effective than implementation of activated carbon or UV-peroxide. Therefore, ozone treatment approach will be coupled with reservoir mixing/aeration to provide a multi-barrier approach to T&O episodes, while also achieving improvement with additional water quality concerns, including manganese, iron, turbidity, and organics. This presentation will present the approach utilized for identifying the raw water odors, and for selecting the appropriate treatment strategies for attaining multiple water quality goals.
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