We are proud of the quality of the water we supply to more than 425,000 residents of Saint Paul and the surrounding communities. We consistently meet all United States Environmental Protection Agency (EPA) and Minnesota Department of Health regulations governing drinking water.

Watch where our water comes from and how it is treated:


Water Quality Reports

The EPA requires water suppliers to provide consumers with an annual report detailing all substances detected in the water in the prior year:


We hope that this report advances our customers' understanding of drinking water and heightens awareness of the need to protect precious water resources. You may request that a paper copy of the report be sent to you by calling a customer service representative at 651-266-6350 during normal business hours or by emailing us with your request. 

Monthly water analysis reports are available as well.

Treatment Process

The utility’s water treatment plant was built in 1920-1922, since then it has been enlarged, modernized, and provides up-to-date treatment techniques to ensure high quality drinking water. Water is treated in the following process:

Raw Water

The raw water is first treated in the supply lakes through oxygenation and the addition of ferric chloride to reduce algae growth. The amount of chemicals to be added at the treatment plant is determined by the raw water’s characteristics.


Scenic photo of Mississippi River

Mixing Basins

Chemicals are added as the water enters two rapid mixers: lime for softening and aluminum sulfate as a primary coagulant. Chemical reactions begin to change certain of the hardness compounds in the water from soluble to insoluble precipitates called “floc.” Floc absorbs color and entangles bacteria and other suspended matter. As the floc settles, the hardness is reduced, resulting in finished water hardness of about five grains per gallon (90 parts per million).


Photo of lime holding tanks in SPRWS water treatment building.


The water then passes through three basins called flocculators. Large, motor-driven paddles rotate slowly, causing the floc to come into contact with all suspended matter. The long, narrow basins ensure that the softening and coagulation agents have sufficient time to complete the chemical reaction and prevent the floc from settling. Ferric chloride is added as a flocculant aid. 


From the flocculators, the water enters into one of five clarifiers. Here, the velocity of the water is reduced, allowing the floc to settle rapidly to the bottom and the clear water to flow over the top of the basin. The settled floc is called spent lime and eventually flows to the dewatering plant, where the solids are separated and the remaining water content is recycled to the plant. The solid lime is trucked out for agricultural use.


Water clarification holding tank at SPRWS.

Recarbonation Chamber

As the water flows out of the clarifiers, it enters the recarbonation basin. Carbon dioxide gas is added to lower the pH of the water. Fluoride is also added in this chamber, which improves dental health. 


Water is then distributed to 24 filter units. Each filter has a bed of filter media 40 inches deep, consisting of 36 inches of granular activated carbon (GAC) on top of 4 inches of sand. Gravity pushes water through the filter and any remaining particulate matter is trapped in the filter. These filters remove particles as small as protozoa, and as such, provide a barrier against organisms such as Cryptosporidium and Giardia. The GAC filter media also remove taste and odor compounds from the water, helping it taste better. Filtered water is collected from the bottom of each filter and routed to the disinfection step.


Example GAC water filter used at SPRWS


Chlorine is then added to kill bacteria and virus. Free chlorine is in contact with the water for a period of time; then ammonia is added to react with the chlorine. This combined chlorine/ammonia compound is called chloramine. Chloramine is more stable than free chlorine, and allows for disinfectant to remain in the water even at the far reaches of our distribution system. Chloramine is also less likely to form unwanted disinfection by-products.

Quality Control

The water from the Mississippi River, the lake system, and the raw water entering the plant, are continuously subjected to bacteriological, biological, physical, and chemical analyses. All analyses is done by professional laboratory staff to determine the treatment required for softening and disinfection. Determination is also made on if the utility’s watershed restoration strategies are controlling algae effectively. Factors that may lead to deterioration of water quality are disclosed, and preventative measures are taken.

Taste and Odor Panel

Saint Paul Regional Water Services has convened a “Taste and Odor Panel” once a week since 1994. The panel of utility employees uses samples of both raw water and distributed water for detection of unwanted odors and smells. The origins of the samples are not known to the panel members. This process can give the utility’s laboratory advance warning of any problems in the water system.

Federal Surface Water Treatment Rule

Before the finished water leaves the plant, on-line analyzers ensure compliance with the federal Surface Water Treatment Rule. The water in the distribution system is routinely examined for chlorine residual and bacteriological content in accordance with standards set by the Environmental Protection Agency and the Minnesota Department of Health.

Watershed Protection & Restoration

The source water from the Mississippi River is pumped through a chain of natural lakes north of Saint Paul. When the lakes are at optimum elevations, there is an available supply of 3.6 billion gallons of water. In years past, excessive nutrients in the lake reservoir system created taste and odor problems. To address these problems, the utility and partnering neighbor municipalities, began a watershed management and reservoir restoration program.

Sampling Sites

The watershed strategy established 22 sampling sites which helped identify the basic problem, nutrient enrichment, created mainly by water from the Mississippi River and Rice Creek, recirculating reservoir sediments, and runoff from local watershed rainfall.

Control Measures

Excessive nutrients, called “phosphorous loads”, increase the amount of blue-green algae which imparts taste and odor compounds. To inhibit the growth of excessive algae several controls were implemented:

  • Installation of ferric chloride feed systems
  • Installation of aerators
  • Restoring water levels to near-natural conditions in certain wetlands

The control measures targeting the Mississippi source water and the lake sediment loads have successfully reduced the phosphorus concentration from approximately 60 to 80 micrograms per liter to 20 to 40 micrograms—very near the goal of 25 micrograms. For example, restoration work on the Lambert Creek watershed area was selected by the Governor's Clean Water Initiative in 2004 as one of two metro area clean water projects. The addition of a weir, pond, and ditch in the watershed will help us reduce the phosphorus levels of water coming into Vadnais Lake.


Watershed and reservoir management has reduced significantly taste and odor problems in the reservoir system and increased the effectiveness of the plant treatment process. Due to improved raw water conditions there has been a significant reduction in chemical cost.This approach allows Saint Paul Regional Water Services to provide quality, cost-effective water that meets regulations and customer expectations.

Upper Mississippi River Source Water Protection Project

The Upper Mississippi River Source Water Protection Project (UMRSWPP) was formed by the cities of St. Cloud, Minneapolis, and St. Paul, along with local units of government, to partner together for Source Water protection of the Upper Mississippi River.

Last Edited: April 6, 2021