Pacific Northwest Clean Water Association. Water Reuse A multifaceted resource

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1 Pacific Northwest Clean Water Association Water Reuse A multifaceted resource

2 Water Reuse A multifaceted resource City of St. George, Utah Case Study Presented by: Mike Chandler, P.E., Bowen Collins & Associates Ben Ford, Wastewater Manager, City of St. George

3 Location and Geography Home of Zion National Park Climate: Arid 8.25 inches annual rainfall Population: 80,000 one of nations fastest growing metropolitan areas Average Temp: High -79 F Low 48 F

4 Economy and Attractions Economy: Skywest Airlines Walmart Distribution Intermountain Health Care Blue Bunny Ice Cream Tourism: Golf and Softball Zion and Bryce National Parks Tuacahn Amphitheater Shakespearean Festival St. George Marathon (13 th Largest in Nation) Ford Ironman Triathlon

5 Reuse in St. George Located in the Northeast corner of the Mojave, water resources are precious Use of recycled wastewater was a desired regional goal, but cost prohibitive In 1987, what started as a lawsuit, ended in a win-win situation for the Bureau of Indian Affairs, St. George, the Paiute Indians, and all of Washington County St. George Salt Lake City

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7 A tertiary treatment phase was added to the St. George Regional Water Reclamation Facility to settle a water right dispute with the Paiute Tribe. (Funded by BIA) St. George began producing recycled wastewater (reuse water) in September of 2006 Major users include local golf courses, schools, parks, and farmers

8 Overcoming Challenges Design Criteria

9 St. George Facilities Description Reuse Facility

10 Construction Constructed in 2006 Total cost = $4.2 million Overview Metal building construction MGD Traveling bridge sand filters Liquid sodium hypochlorite (12%) storage and feed equipment 2 Chlorine contact chambers 3 Vertical turbine pumps (2,500 gpm each) Current Capacity: 7 Million gallons per day Average Daily Production: 2.5 Million gallons per day Future Phasing 1- Additional traveling bridge sand filter 1- Additional vertical turbine pump bay Future Capacity: 10.5 Million gallons per day

11 Plant Schematic

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13 Utah R-317 Regulations for Reuse Required Treatment Processes Type 1 - Use of Treated Domestic Wastewater Effluent Where Human Exposure is Likely Type II - Use of Treated Domestic Wastewater Effluent Where Human Exposure is Unlikely Type I and II BOD and total suspended solids concentrations must not exceed secondary quality effluent limits Filtration, such as sand and/or anthracite, approved membrane processes or other approved filtration processes. Additionally for Type I Disinfection - accomplished by chlorination, ozonation, or other chemical disinfectants, UV radiation, or other approved processes. Other

14 Utah R-317 Regulations for Reuse Water Quality Limits: BOD shall not exceed 10 mg/l as determined by composite sampling conducted once per week. Average daily turbidity shall not exceed 2 NTU, and turbidity shall not exceed 5 NTU at any time. Turbidity shall be measured continuously. The turbidity standard shall be met prior to disinfection. The weekly median E. coli concentration shall be none detected, as determined from daily grab samples, and no sample shall exceed 9 organisms/100 ml. The total residual chlorine shall be measured continuously and shall at no time be less than 1.0 mg/l after 30 minutes contact time at peak flow. The ph as determined by daily grab samples or continuous monitoring shall be between 6 and 9.

15 Compliance History Constituent Limit BOD (mg/l) 10 2 Turbidity (NTU) E. Coli (col/100ml) 2 (daily avg) 5 (N.T.E) Plant Average ND ph Chlorine residual (mg/l) 1 1

16 Operation and Maintenance Operational Challenges Turbidity spikes result of algae growth in filtration media Part of normal O&M is a monthly shock dosing of chlorine and backwash of filtration media to remove algae Flash mixer of chlorine needs periodic de-scaling

17 Lessons Learned Disinfection Sodium Hypochlorite generation system will replace bulk liquid system in the future Traveling bridge filters Provide high quality effluent Prone to algae growth, but easily controlled with periodic shock dose Effluent quality diminishes if filters are stressed above design level of 3.5 gpm/sf

18 Future Considerations Reuse Possibilities Can be used to: Resolve water rights disputes To replace potable water in outdoor irrigation In industrial processes that do not require potable or high purity water supply To enhance agricultural water sources To reduce total cost/impact of stringent nutrient requirements

19 Questions? Thank You