Drinking Water Supply
BWL draws 100 percent of its water from wells which pump almost entirely from a layer of water-bearing sandstone 100 to 500 feet below the surface – the Saginaw Aquifer. The Saginaw Formation is shielded in most places from direct contact with the surface by layers of clay and shale, so contaminants do not easily get into the water at that level.
The 125 wells that make up the BWL system pump an average of approximately 19.2 million gallons per day (MGD) to either of two water conditioning plants. That's a lot of water! However, long-term measurements of the aquifer show that levels have not gone down overall and that the supply will be adequate for many years to come.
Water Conditioning
Soften
The BWL’s raw water supply is of great quality and only needs minor conditioning before distributing to our customers. The water received at the plant is softened, disinfected, and filtered. The raw well water has an average of 450 parts per million (ppm) hardness. The BWL uses a lime-soda ash process which removes excess calcium and magnesium, leaving an average of 97 ppm hardness in the finished water.
Disinfect
One of the key factors in the maintenance of good water quality lies in the establishment of a disinfectant residual. The BWL relies on the use of a type of chlorine called chloramine. Chloramine, which is a compound made up of chlorine and ammonia, has a number of advantages over "free chlorine."
- First, it lasts longer. As water travels through mains, it loses its residual much more slowly than it would with free chlorine. That means that less must be applied at the water conditioning plant to achieve a residual near the end of the system.
- Second, it imparts very little odor or taste. We are all familiar with the "swimming pool" odor of highly chlorinated water that detracts from its appeal. People seldom notice any odor from chloraminated water.
- Third, it results in lower disinfection by-products. Regulated compounds like trihalomethanes and haloacetic acids are reduced by up to 90 percent compared to waters using free chlorine.
Filter
The final step is filtration. The BWL uses sand filters for final clarification of our water, which ensure quality and great taste.
Additional Processes
Corrosion Inhibitor
Reducing the water's corrosiveness is important to keeping lead out of drinking water. In December 2016, the BWL replaced its last known active lead service line, but the BWL does not control the plumbing in the customer’s home or business. The BWL uses a phosphate compound to coat water pipes and prevent leaching of lead and copper into drinking water, which has shown past success in reducing lead levels. The level of corrosion control leaving our Water Conditioning Plants is tested every 4 hours and 30 minutes to confirm that proper levels of the additive are present. Also, quarterly sampling results from the distribution system are used to confirm that the proper additive levels are present throughout the BWL's service territory following treatment.
Fluoride
The raw water coming into our two water conditioning plants has a naturally occurring level of fluoride at approximately 0.35 ppm. The BWL adds fluoride to the water to bring it to the optimal level of 0.7 ppm recommended by the Center for Disease Control and Prevention (CDC) and the U.S. Public Health Service and approved by the EPA.
Water Distribution
After conditioning, the water is then pumped from one of the two Water Conditioning Plants over 800 miles of underground mains under pressure to our customers. The maintenance of that pressure ensures that when leaks occur, the leakage is of conditioned water out of the main, not of dirty water into the main. The BWL monitors water quality throughout the year at representative sites across the distribution system.
By conditioning the water, the BWL is able to stabilize the water brought to your tap. In maintaining consistency in the conditioned water, we offer you the ability to tailor the water to your use. The BWL Typical Analysis of Conditioned Water may give you an idea of what ranges you might expect for a variety of chemical measurements.
Frequently Asked Questions
The discoloration you see typically comes from iron that accumulated in cast iron water mains and has been picked up by a large change in flow. This change can be caused by main break, repair or replacement, flushing, firefighting activities, or anything else that disrupts the normal flow through the water main.
Although iron appears unappetizing and may impart a metallic or slightly bitter taste, it offers no health threat. Extremely high levels of iron can induce nausea and vomiting, but that amount would not taste good and one would have a hard time drinking it.
Call the BWL Water Dispatcher at 517-702-6490. We want to know about every instance of this occurring, both to respond to your concerns and to help us understand all of the conditions that produce this iron pick-up. If you must have a drink of water, drawing some into a pitcher or tall glass and letting it stand will give the discoloration a chance to settle. Generally, if you wait for a short period (an hour or so), then flush your faucet for 10 minutes, the discoloration will disappear.
As always, call the BWL Water Dispatcher at 517-702-6490 to alert us when you see something unusual in your water. This is not normally hazardous, but it’s helpful for us to know when and where this occurs. The two most typical causes for what you describe are easily distinguished from one another. The first is air, which can enter the water mains either from a main break or main isolation, or from air due to the use of certain wells in the BWL system. The second is from deposits of calcium carbonate that have been laid down in the mains over time and then picked up due to large changes in flow.
Collect cold water from your tap in a clear glass. If the water clears from the bottom up, it’s air. If the cloudiness is caused by calcium carbonate (product of the softening process), it will clear from the top down. Neither of these is hazardous, and both should disappear within hours. The exception might be during a dry, high-consumption summer, when many air-pumping wells must be used for extended periods. The air will take some time to work its way through the system once those wells are shut off again.
Some small amount of the dissolved iron from the water mains is carried into the bowl where it eventually meets oxygen at the surface and is oxidized. In the oxidized form, iron can no longer stay dissolved in the water and plates out on the porcelain surface. Iron oxide can stick to most any surface. It isn’t unusual for water that carries a very small amount of iron (0.1 parts per million) to, over a long period of time, cause bathtub surfaces and shower curtains to show an orange tint. The iron will not be visible in the water, but after it hits the air and the iron oxidizes, the iron oxide begins to accumulate on the surface. Most bathroom cleaners will remove this iron oxide.
Iron is the sixth most abundant element in the universe. It is usually found as an oxide ore; hematite. It can also be found in both surface water and in groundwater, but is more abundant in the latter.
Iron can occasionally be found in its elemental state, but reacts quickly with oxygen to produce oxides like magnetite (Fe3O4) and hematite (Fe2O3, otherwise known as “rust”). Iron can often be found dissolved in groundwater in its reduced form, where there is little oxygen present. In its oxidized form it becomes rust, and imparts a yellow, orange or brown color to water. Manganese is sometimes found associated with iron, but our local aquifer, the Saginaw, appears to have little or none.
Iron is a natural constituent of many soils and dissolves into water when oxygen is not around and groundwater is mildly acidic. Iron is naturally present in groundwater and because it is truly dissolved, is not normally visible to the eye. Some subsurface microbes use iron as an electron acceptor and then combine it with oxygen to form oxides. The BWL’s softening process removes almost all of the groundwater iron. What iron you see is almost always due to minor corrosion of cast iron water mains.