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WSB PROJECT EXPERIENCE EXAMPLE Biological Filtration Water Treatment Plant GLIBNT: CITY OF ST. MARTIN LOCATION ST. MARTIN, MN DURATION: 2017 The City of St. Martin, Minnesota had been operating its water system with two shallow wells(Wells 1 and 2),which had benzene levels above the maximum ` m£ contaminant level(MCL).The wells were located near a creek that was the outfall of a wastewater treatment system and considered vulnerable to contamination. The geology of the area is underlain with a granite shelf, Construction of the plant was completed in the fall of making it difficult to find sites with a sufficient yield 2017.The plant has three pressure filter vessels.The within the city limits,so the city drilled two new wells first vessel is a biological iron filter,which receives to the east of the city.The current wells are considered water after air(partially oxygen) is added to facilitate non-vulnerable, in contrast to the shallow wells by the the biological oxidation of iron. Additional air is then creek. However, high levels of iron and manganese in injected prior to the second vessel.The second the ground continued to cause aesthetic concerns, vessel is an ammonia nitrification filter, in which two especially with the staining of fixtures in people's reactions occur.The first reaction,the oxidation of homes. In addition, high levels of ammonia were ammonia to nitrite, is accomplished by nitrosomonas present in the new wells,although not as high as they genus microorganisms.The second reaction is by had been in the previous wells. the nitrobacter genus to convert the nitrite to nitrate. The City explored its options with WSB,Tonka Water, Oxidized manganese and any remaining biological matter are filtered with anthracite and green sand in the Minnesota Department of Health (MDH), and the US the third vessel.After filtration,three chemicals are Department of Agriculture(USDA) Rural Development. added:fluoride for dental care,chlorine for disinfection During this period St. Martin was meeting with the USDA and to maintain a residual in the distribution system, regarding its wastewater treatment system and found and sodium silicate for corrosion control.The filters out that the rates that they qualified for, based on per are backwashed with non-chlorinated water from a capita income,could be carried over to a water system. concrete backwash holding tank in order to not disrupt The city decided on biological treatment, using naturally the bio-growth on the filter media. occurring microorganisms instead of chemicals to The total project cost was approximately$3M, remove contaminants.The city leased a trailer to do a which included the plant and related infrastructure. biological filtration pilot study.City staff did the daily Approximately 45%of the project was funded with a grant testing and pilot work with oversight by WSB and Tonka and the rest from a 40-year loan at an annual interest rate Water.The pilot study was performed for four months of 1.875%, both from USDA Rural Development. to verify that the innovative technology would work with the city's groundwater. Upon achieving successful results from the pilot study,the city authorized WSB to P EY WSB STAFF. GREG JOHNSON, GREG GLUNZ design and bid the first fully biological filtration water treatment plant in Minnesota. A Proposal for Design,Bidding,and Construction Administration for a Water Treatment Plant for City of Lino Lakes Relative Experience,Qualifications,&References 127