Summary
Arizona State University has been working with regional water providers, like the Salt River Project, Central Arizona Project, and metropolitan Phoenix cities since 1998 on algae-related issues affecting drinking water supplies, treatment and distribution. The results have improved the understanding of taste and odor occurrence, control and treatment; improved the understanding of dissolved organic and algae dynamics and initiated a forum to discuss and address regional water quality issues. The monitoring benefits local water treatment plants by optimizing ongoing operations (i.e., reducing operating costs), improving the quality of municipal water for consumers, facilitating long-term water quality planning and providing information on potentially future-regulated compounds. ASU has been monitoring water quality in terminal reservoirs at Lake Pleasant, Saguaro Lake and Bartlett Lake continuously from 1998 to the present for algae-related constituents (taste, odors and, more recently, cyanotoxins), nutrients and disinfection by-product precursors (i.e., total and dissolved organic carbon and organic nitrogen). Additional monitoring has been conducted in the SRP and CAP canal systems and in water treatment plants in Phoenix, Tempe and Peoria. During this work, the Valley has been in a prolonged drought and recently had one above-average wet year.This data provides an important baseline for the development of new or expanded WTPs and the ongoing management of existing WTPs. The current work has improved the understanding of T and O sources and treatment, but additional research and monitoring into the future is necessary.
Reservoir monitoring is conducted once per month at Bartlett Lake, Saguaro Lake and Lake Pleasant, and quarterly at Roosevelt, Apache and Canyon Lakes. Samples are depth-integrated in the epilimnion and hypolimnion. CAP will collect samples from Lake Pleasant. SRP will collect samples from Bartlett, Saguaro, Roosevelt, Apache and Canyon Lakes at no cost to ASU or cities. Field measurements for temperature with depth will also be collected. River samples from the Salt River below Saguaro Lake at Blue Point Bridge and from the Verde River at the Beeline Highway will be collected once per month. Samples will be analyzed for carbon (TOC/DOC), total nitrogen, total phosphorous, arsenic, conductance and T and O compounds (MIB, geosmin, cyclocitrol). The purpose of the lake sampling is to provide early warning information on potentially large changes in water quality due to algae production, lake destratification and forest fires or other runoff events. Additional monthly sampling will be coordinated with the USGS at Salt River above Roosevelt, Verde River at Tangle and with CAP at Lake Havasu.
Canal monitoring is conducted once per month January through June and twice per month as needed during periods of higher T and O production July through December. Field measurements for temperature and pH will be collected. Sampling will include the CAP, Arizona and South canals at multiple locations. Monthly samples will be analyzed for carbon (TOC/DOC), total nitrogen, arsenic, conductance and T and O compounds (MIB, geosmin, cyclocitrol). Bi-weekly samples will be analyzed only for T and O compounds. The purpose of the canal sampling is to identify hot-spots of T and O production and to make recommendations to the cities, SRP and CAP to perform some type of treatment (brushing, copper, etc.). Additional canal sampling will be scheduled to further identify canal hot spots or to provide more frequent process control information.
WTP raw and finished water is collected once per month January through June and twice per month as needed during periods of higher T and O production July through December. WTP sampling will be conducted at two Tempe WTPs, one Peoria WTP, multiple Glendale WTPs and other selected WTPs. Monthly samples will be analyzed for carbon (TOC/DOC), total nitrogen, arsenic, conductance, and T and O compounds (MIB, geosmin, cyclocitrol). Bi-weekly samples will be analyzed only for T and O compounds. The purpose of the WTP sampling is to provide continued evaluation of water quality produced at the WTPs.
