Feature Get Your Feet Wet 84
By Darla Read When Shawn Kessel became city administrator for Dickinson, ND, the city had already begun the process of looking at how it was going to treat effluents and its wastewater. “It had become apparent that the lagoon-based system was not going to last long,” explains Kessel. He says that when the city began working with an engineering firm, Dickinson was expecting a population base of about 26,000, which would have worked fine with a rapid infiltration system. The firm Dickinson began, and continues, to work with is Apex Engineering Group. Project manage Karla Olson says the wastewater pond system—also known as a lagoon-based system and what Dickinson had—is a great, low-maintenance option for smaller communities. “At the time, the city was at 17,000 and looking up to 26,000, so our first recommendation was to expand the pond system,” she says. “Then the boom hit,” recalls Kessel. “We quickly understood that we were going to exceed the capacity long before the life of it.” Olson says that all of a sudden, the city was looking at growth up to 26,000 people in a couple of years instead of just 20 years, and says the pond would have been at capacity by the time it was constructed. The rapid population growth occurring in the region is due to the oil formations in the Bakken area. “It has created a lively economic environment,” explains Kessel, noting that it has resulted in Dickinson, ND being the third-fastest growing micropoliton city in the United States in 2012. Gauging growth Olson says looking at the population range of 35,000 to 38,000 meant that a pond system was no longer feasible for Dickinson’s rapid growth, so the company switched gears to a plant that would use aeration and mechanical means to speed up the process: more specifically, a mechanical wastewater treatment and reclamation facility. In addition to there being a difference in how wastewater is treated—naturally over time versus aided with mechanical equipment—there is a huge size difference between the two types of water treatment facilities; Dickinson’s existing pond system is spread over 200 acres, whereas the new mechanical wastewater treatment facility treats the water to a better quality and will only take up about eight acres. “...the initial estimate was between $13 and $20 million, whereas the new project has a price tag of $43 million, and that’s just to complete the first phase. Before the exact scope of the project was determined, staff from the City of Dickinson and Apex Engineering toured wastewater facilities across the United States that used some of the six technologies the company was considering, allowing staff to see firsthand the operation, maintenance and cost of the various treatment components. In the end, an integrated fixed-film activated sludge (IFAS) technology was recommended with a “flexible, modular approach” to prevent an unnecessarily large facility, which would have been expensive to construct and difficult to operate. The proposal also allows the city to double the capacity of the water reclamation facility in the same footprint. Projecting price tags The entire project will be built over three phases: phase one can service 35,000 people; phase two can service a community of 48,000; and the third phase can service 65,000, so the facility will be able to keep up with Dickinson’s projected growth. The sanitary collection system upgrades to convey wastewater from the existing ponds to the new facility will include a new 15-million gallon per day influent pump station. The station will include coarse screening to remove large debris before entering the two-and-a-half mile pipeline to the new facility. Additional collection system projects will occur over the next few years in subsequent phases. Because of the big change in the scope of the project from where it initially began, there was also a change in the cost. Kessel says the initial estimate was between $13 and $20 million, whereas the new project has a price tag of $43 million, and that’s just to complete the first phase. He says the operational expenses for this plant will also likely more than double because more technically trained people will be required to operate it than if there was an expanded pond system. Kessel says the city raised its sewer rate right away so that there would be some accessible funds for when construction began; that way, financing can be delayed as long as possible, too. The rate increase was minimal: from $1 to $2 per 1,000 gallons per household. Now, the city is undergoing a rate study, which he says likely means the rate will increase again in the future; an increase that will exceed what has traditionally been implemented, says Kessel. However, he says having such a facility provides a “sense of security” to the city and region. “We know it will be state-of-the-art,” says Kessel. “It will allow us to treat constituents we couldn’t treat as well before.” State-of-the-art screening The treatment facility consists of fine screening to remove debris to three millimeters, vortex grit removal, integrated fixed film activated sludge (IFAS) biological treatment, clarification and UV disinfection. Biosolids produced from the treatment process will be land-applied to adjacent agricultural fields as fertilizer. The average daily wastewater flow will be around 3.65-million gallons per day, with its peak hourly wastewater flow at nine-million gallons per day. The facility will be the first of its kind in North Dakota, using a biological treatment technology in the range of 15 to 20 years old; Olson says that most wastewater treatment technologies used were around 50 years old, making this fairly “new.” The IFAS process was selected due to the ease of expansion, quality of water produced, small footprint and ability to resist plant upsets. The facility will treat water to some of the most stringent effluent standards in North Dakota. Furthermore, “it will meet the expectations of today but also tomorrow. It will meet Environmental Protection Agency 85