St. Joseph Water Plant Provides Pulchritude on the Prairie
New Plant Reduces Sludge, Looks Good
From the Winter 2008-09 Minnesota Department of Health Public Water Supply Unit, Waterline, Minnesota Department of Health
The world abounds with examples of form taking precedence over function. However, the water treatment plant in St. Joseph, Minnesota, combines function and form. The plant, which opened in 2007 and removes iron and manganese, is on the edge of town, across Interstate 94 from the rest of the city.
Now standing virtually alone off the freeway and Stearns County Road 2, the plant was designed to be aesthetically pleasing in anticipation of the additional development that will be taking place in the area. They didnt want to build a typical square building, said operator Mike Sworski. Being the first ones out here, they wanted to set a pattern. With an arch and a curved roof, the structure has more of a look of a community center rather than a municipal utility.
But the building has some brawn in addition to the beauty as it features plate settlers to reduce the sludge, which typically would go to a sanitary sewer. The sewer is nearly a mile away, and plans to extend the line arent in the works and wont be until future development reaches the outskirts. We figured that out rather quickly when we got across the freeway, said John Thom of SEH, Inc. of Vadnais Heights, Minnesota, the design-engineering firm. With the sewer not an option, the plant was built with plate settlers, normally used in the wastewater industry, to keep the sludge to a minimum. The sludge is stored on site before being hauled into town.
The backwash water is recycled at 10 percent of the raw-water flow coming into the plant. So if we have 800 gallons coming in, 80 gallons go into plate settler, explained Sworski. The end result is 2 percent or less of waste from the backwash water. Sworski noted that at the old plant, which is still being used, the backwash water sits for eight hours. At the new plant, they are able to start the reclaim process right away.
The new plant oxidizes iron and manganese through aeration, then has four cells of anthracite/greensand filters. It can produce three million gallons per day, three times the capacity of the old plant, which is tucked in amid houses and other buildings in the heart of St. Joseph, leaving no room for expansion. Sand filters remove primarily iron at the old plant because water from the wells that serve it is low in manganese. The plants are run separately, and the water is blended in the distribution system.
With the construction of the new plant came three new wells and a one-mile extension of the distribution system. Thom said that the ground had to be built up since they were below the water table. The bottom of any basin must be above the water table by two feet, he explained.
It was quite the learning process for us, said Sworski of the plate settlers, adding, “It definitely does what its supposed to do.
|Plate settlers at the new plant (left). The existing plant (right) in the heart of St. Joseph.|