Saint Paul Regional Water Services

1water  I toured the Saint Paul Regional Water Services plant on far north Rice Street. SPRWS has been governed by a public/private partnership since the City took over from a visionary entrepreneur in the 1880's. 2water  Water for Saint Paul and some suburbs comes mostly from the Mississippi (at Fridley) but spends time in a chain of lakes before treatment. SPRWS is in negotiation with additional suburbs. 3water  This is the intake chamber and boat house on Vadnais Lake, the last in the chain. There are also ten ground water pumps for back up but 70 - 80% of our water comes from the river and lakes. 4water  The first step at the treatment plant is in the "floc tanks" where alum and quicklime are added. These raise the pH (softening the water) to enable subsequent treatment and cause particulates to clump together into muddy "floc."
5water  The ph goes up as the chemicals do their work. 6water  The huge, walk-in clarifier tanks date to the 1920's and are really cool spaces. Solids drop to the bottom and are moved to the center while clear water is taken from the top. 7water  "Dewatering" in a water plant sounds hilarious but makes sense as process. Floc-water is pumped over from the clarifiers and separated (dewatered). The remaining sheets of clay-like floc are spread on agricultural fields. 8water  Carbon dioxide is forced into the clarified water to bring the pH back down to about 8.6. Floride is added at this stage, a state-mandated law.
9water  With the pH back to an acceptable level, the remaining tasks are filtration for taste and odor as well as disinfection against viruses and bacteria. 10water  So here are the controls for the filtration tanks. Many complained of "fishy" water in Saint Paull in the 1990's, so something had to be done. 11water  Three foot thick beds of activated carbon were added to the bottoms of these tanks. "Activated" means that good bacteria are battling bad bacteria. Taste complaints are less than 10% of the pre-carbon era. 12water  Here is a model of the carbon bed, showing the additional four inches of sand at the very bottom. After this, a compound of chlorine + ammonia is added to kill remaining viruses and bacteria.
13water  Finally, it's done and ready for shipment. The water goes to 425,000 residents through 1,200 miles of water mains. Water consumption actually is dropping in the region because of conservation. 14water  The whole process, from river to distribution pipes, is monitored in this office.