Council nears water softening vote
- Published: April 2, 2015
Village Council is close to approving a water softening component to its proposed new water plant, slated for construction in 2016. The softening method favored by Council is one that reduces the extreme hardness in local water by about half, thus cutting softening costs for village industries and residents while also maintaining some of the health benefits of hard water.
“We heard from citizens that they don’t want added sodium and we heard from industrial customers that they needed added softness, so this is a good compromise,” Council President Karen Wintrow said at a special meeting last Wednesday, March 18. Project Engineer Sam Swanson of HNTB, the engineering firm that the Village has contracted with to design the new plant, presented options for water softening along with a recommendation for pellet softening, the method preferred by Council members and Village staff.
“We’re all in agreement on this,” Village Water and Wastewater Superintendent Joe Bates said at the meeting, referring to his staff.
The discussion on whether to add water softening capacity to the new water plant, and whether pellet softening is the best method, will continue at Council’s April 6 meeting. It is likely that Council will also vote to approve pellet softening at that meeting.
The softening question is one of the last remaining issues before the Village moves ahead with the plant design. After several years of research and discussion, Council at the end of last year voted to construct a new plant to replace the Village’s current aging plant.
While Council expected citizens to turn out for the March 18 meeting, only one did. Wintrow expressed her disappointment with the low turnout, and encouraged villagers to engage with the issue.
Why pellet softening?
The question of whether to include water softening capability in the new plant is linked to the extreme hardness of local water, which has a range of 275 to 553 milligrams of hardness per liter (caused by calcium and magnesium), when water above a level of 60 milligrams per liter is considered hard. Yellow Springs drinking water is sourced from groundwater, and the water’s hardness is connected to its proximity to the rock bed, from which calcium and magnesium dissolve into the water.
Hard water is considered destructive to pipes and appliances, and many villagers own home water softeners, according to a 2011 survey. But some prefer hard water for its possible health benefits, as longstanding research has linked hard water with greater heart health when compared to areas that have soft water.
The recommendation to move ahead with pellet softening came after a several-month exploration process by a group of Council members and Village employees. The group consisted of Council representatives Wintrow and Gerry Simms, Village Manager Patti Bates and Assistant Manager John Yung, Electric and Water Distribution Superintendent Johnnie Bates and water plant staff Joe Bates, Brad Ault and Richard Stockton.
The group in January and February visited about nine area water plants in Indiana and Ohio that each used one of the four most common municipal water softening methods: ion exchange, lime softening, nanofiltration or pellet softening. Pellet softening, used at a plant in Jackson County, Ohio, impressed the group because it’s a simple process with low operational costs, it’s considered environmentally friendly and relatively safe and is the least expensive, Simms said.
“Pellet softening was the most interesting” of the four softening methods, he said.
The group was also attracted to pellet softening because it would remove about half the hardness rather than most of the hardness from local water, therefore still providing the health benefits associated with hard water, Wintrow said. While a small amount of sodium would be added to local water during the process, it is about two to three times less than the amount added during the most frequently used water softening methods of lime softening or ion exchange, Swanson said.
The pellet softening process is a fairly simple one, according to Swanson of HNTB. The water is first pretreated to remove iron and manganese (which causes brown water), a process that involves aeration and the addition of chlorine; next, sodium hydroxide is added to increase the water’s pH level. Next, the treated water is pumped into a large cone-shaped tank about 18 feet tall for the softening process. The water flows up from the tank bottom at the same time that a fine sand floats down from the top, causing calcium in the water to scale onto the sand particles as the sand falls to the bottom, removing the calcium hardness from the water but leaving the magnesium. The softened water then flows through the plant’s filter and the sand is collected for removal or reuse.
The pellet softening process is popular in Europe but less known in this country, according to Swanson, who said this is the first pellet softening system that his company is designing. However, he said the design is a relatively simple one compared to other methods. Swanson estimated that about 5 percent of American municipalities use pellet softening.
Pellet softening includes adding sodium hydroxide, also known as lye or caustic soda, to the water. The chemical compound in larger quantities is corrosive and harmful to health, but the amount of sodium added during the process will be between 29 and 43 milligrams per liter, within the range of 27 to 57 milligrams per liter approved by the Environmental Protection Agency, or EPA.
Any health risks associated with sodium hydroxide would come with leaks or accidents, according to Swanson, who said that plant workers will not handle the compound. Rather, it will be trucked in, in a liquid form before being pumped into the tanks. Should a leak occur, the tanks are surrounded by sumps, or lower areas, in which any leakage would collect.
Sodium hydroxide is one of the most common chemicals used in the water softening process, according to Swanson, second only to chlorine, which is already used to disinfect local water.
“Nothing we’re recommending is atypical,” Swanson said, although he added that, “All chemicals used in the water treatment process need to be treated with respect.”
The pellet softening process will add about $600,000 to the $3.2 million projected price of the new water plant, according to Swanson. The cost covers the purchase of two pellet softening tanks. The operational cost of the process, which covers the cost of chemicals used and transport of sand, will be about $50,000 a year, and can be accomplished with the current water plant staff, Swanson said. In contrast, the annual operating costs for the other methods were about $110,000 yearly for nanofiltration, $90,000 for acid ion exchange and $130,000 for lime softening.
Once Council decides on the softening issue, the design phase will move ahead, according to Swanson, who said a conceptual design should be finished by summer 2015. Construction is slated to begin in 2016.