Sanborn Municipal Utilities host Open House at New Water Treatment Plant
There was a guided tour of the new Water Treatment plant held on June 22nd from 2 p.m. to 7 p.m. With yummy grilled hamburgers and hot dogs for the public served from 5 p.m. to 7 p.m.
Visitors were able to tour the facility to find out how it works to make drinkable water for the community to use.
When did the project start and when was it finished? The project was bid in March 2020, the contractor mobilized to the site in May 2020, and Just 11 months later in April 2021, high quality water was flowing to the community, right on schedule. The cost for the new plant is $8 million. The cost is shared between residential and industry customers, resulting in a reasonable overall impact to rates. The water treatment plant is financed using Iowa State Revolving Fund. The Iowa Department of Natural Resources required the treatment system be tested before a new system was fully implemented to assure water quality standards are met.
The new plant is capable of treating 900,000 gallons per day with the ability to expand to 1.3 million gallons per day. The current average is between 400,000 to 500,000 gallons per day. Before the new water treatment plant the city’s average water use was 350,000-400,000 gallons per day.
Zim Zeutenhorst, City Administrator said “Usage has definitely gone up since the plant was built.”
Before the new water treatment plant, Sanborn had 4 shallow wells and one deep well that served as backup. When demand was less, shallow well water was pumped directly into the distribution system simply by chlorinating it. As demand grew, deep well water from the Dakota Aquifer, which is high in hardness, sulfates, iron and ammonia was utilized. That required a new treatment system. Deep water wells notoriously bring much uncertainty. First, until it is dug, there is no way to be certain that it will produce.
“One advantage of a deep well,” explained Zeutenhorst, “is that it is less affected by drought and other weather issues.” A disadvantage Zeutenhorst mentioned about deep wells is that they are full of minerals that can be hard to remove. To answer this dilemma, Sanborn installed, at the same site as the new well, a reverse osmosis (RO) water treatment facility.
What is Reverse Osmosis? Reverse osmosis is the process of removing contaminants from water when pressure forces it through a semi-permeable
membrane. The bag filters are changed every 3 to 6 months, the reverse osmosis skid has filter cartridges and they will need to be changed out in 5 to 7 years. The replacement cost of those filters is approximately $120,000 currently. The hybrid reverse osmosis (RO)/pressure filter treatment plant
significantly improved water quality for everyone.
Unfiltered water from the deep well comes into the plant and goes through a bag filter semipermeable membrane. Water flows from the more concentrated side (more contaminants) of the RO membrane to the less concentrated side (fewer contaminants) to provide clean drinking water. The fresh water produced is called the permeate. The concentrated water left over is called the waste or brine. The semipermeable membrane has small pores that block contaminants but allow water molecules to flow through and removes dissolved solids. Then The water goes through a cartridge filter then it goes through the reverse osmosis system. In osmosis, water becomes more concentrated as it passes through the membrane to obtain equilibrium on both sides. Reverse osmosis, however, blocks contaminants from entering the less concentrated side of the membrane. For example, when pressure is applied to a volume of saltwater during reverse osmosis, the salt is left behind and only clean water flows through.
The water from the shallow wells which are located a mile and a half outside of town comes into the plant and runs into a pressure filter. After that water get finished running in the pressure filter it is blended with the reverse osmosis water then the water is put into the big blue storage tanks on the north side of the building. From there the water is pumped out into the distribution system. The system runs 24 hours a day seven days a week during the summertime. During the winter the demand for water is less. There are two osmosis trains in the facility. There is room in the water treatment plant to get another osmosis train in. If another train is added they would need to add on to the blue filters that would make the water production 1.2 – 1.3 million gallons per day.
Adam Roelfs Public Works Superintendent says “There are 4-6 hours a day that we are running both of the osmosis trains to keep up with production.”
The water for right now doesn’t go into the water tower it goes into the distribution system. The water tower is empty at the moment as crews work to repaint it. The valve to the water tower is shut off but the pumps there are running pushing water out to the people. Roelfs explains “thats why we are seeing a fluctuation in water pressure in town”
The project was a huge success for the community in several ways:
• It was completed on time to provide the extra capacity needed.
• The project allowed the City to take 70% of their water from the Dakota, and only 30% from the shallow well source (compared to 50% Dakota/50% shallow pre-project). This significant change allows the City to rest their shallow source and allow it to be a sustainable resource for generations to come.
• The creative design allowed the plant to be constructed on a small parcel of available land.
• The water treatment plant will help the City come into compliance on chloride discharge.
• The City staff have an easy-to-operate plant that only requires staff to be on site two to three hours per day on a routine basis. If anything happens, something is not normal or anything wrong at the plant, the plant will automatically call the on-call number then will go down the list of numbers and keep calling those numbers until someone answers. Staff can set all the perimeters for the system like too high or too low water pressure.