The technical name for the tiny particles is total dissolved solids (TDS). The TDS are a byproduct of the softening system at the water treatment plant, city engineer Brenda VanCleave said.
Before water reaches a Pickerington faucet, it is pumped from large wells near Diley Road. The hard well water is softened using a salt process similar to home water softeners.
Backwash from the water softener includes the TDS that are too small for filters to catch. The water treatment plant pumps the water to the city¹s wastewater treatment plant where it is added to the sewage. All the water is cleaned and poured into Sycamore Creek.
According to a report issued by URS, the engineering firm the city consulted, for six months of 2007, the water discharged into Sycamore Creek exceeded the OEPA¹s allowance for TDS.
"(TDS) are minerals so fine that they can¹t be filtered out," VanCleave said. "For the fish it is basically like breathing particles and it essentially chokes them."
VanCleave said the OEPA has not yet quantified the amount the city may be fined.
URS recommended that the city replace the salt-based water system with one that uses a membrane capable of filtering tiny particles. The membrane system, called reverse osmosis (RO), is estimated to cost $1.8 million to build.
The RO system would not only solve the TDS problem, but it would "produce a superior water quality with a lower sodium concentration," the report stated.
To pay for the RO system, URS recommended that Pickerington water customers pay an additional 90 cents per month.
"The need to increase rates needs further investigation," VanCleave said. "Depending on the savings realized by not using salt to soften the water, a rate increase may not be needed."
At its October meeting, the service committee will compare the RO to a list of 14 other options that URS and city staff have compiled.
One alternative is to dig a deep well to fill with the water treatment plant¹s backwash. That option could cost more than $2 million and not provide any benefit to water users such as improving the quality of the water, VanCleave said.
Another option would be to dilute the water from the wastewater treatment plant with water pumped from a well. It would cost a little more than $200,000, but it would not improve the quality of water.
The dilution well would require a large amount of water and it could affect the water supply of a dozen properties neighboring the wastewater treatment plant that depend on private wells, VanCleave said.
The city could restrict water softeners in homes or the city could limit lawn sprinklers as well.
According to URS, the concentration of TDS poured into Sycamore Creek reached its highest point for 2007 in June. Lawn watering factored into the increase.
Sprinklers spray water softened at the water treatment plant; however, unlike most water that a household uses, the lawn water does not enter the sanitary sewer, which then lessens the TDS dilution potential.
Although the water treatment plant creates more backwash to meet the increased dry-weather demand, the wastewater treatment plant does not have an increased amount of sewer water to help dilute the particles.
The service committee will meet at 7:30 p.m. Oct. 9 in City Hall to further discuss the issue.