New Millersport water treatment plant to restart soon
MILLERSPORT - Weeks of investigation and testing are paying off. The Village of Millersport's new one million gallon per day water treatment plant is expected to go back into production soon.
The new plant went on-line in mid-June, followed by complaints about discolored water. Village officials initially thought that a new water main that changed the direction of flow in part of the distribution system and higher pressure pumps were stirring up sediments in the distribution system. More than 100 fire hydrants were flushed in early July to clear the system of sediment and discolored water. But flushing didn't clear up the water.
At that point, attention turned to the new treatment plant and its computerized controls. Two new wells were drilled to serve the new plant. The two existing wells for the old plant went down about 200 feet, but these wells are deeper at about 325 feet. Their production capacity has been called "awesome." Even though they are within a hundred feet or so of one another, there are major differences in raw water quality, particularly in the levels of iron and manganese.
The new plant automatically rotates between the two wells when the process calls for raw water. At the old plant, operators had to manually switch between the two wells. Ordinarily, automatic rotation is beneficial since it makes sure both well systems are working and doesn't overtax one well or pump. However, in this case, that system initially aggravated the problem by treating different raw water in the same manner.
Most water treatment plants remove iron and manganese using an oxidation/filtration process. Iron and manganese are typically found dissolved in the raw water, but after contacting oxygen they form reddish-brown particles (iron) and brownish-black particles (manganese). They also can impart a metallic taste to the water.
Since both iron and manganese are dissolved in the water, they must first be oxidized into insoluble compounds so they can be filtered out of the water. Millersport uses both chlorine and sodium permanganate as oxidants. Chlorine as sodium hypchlorite (industrial bleach) and sodium permanganate are introduced into the raw water at the top of the "iron tank." The iron and manganese are oxidized and the water is forced through several filter levels including anthracite coal, greensand and several sizes of aggregate. These filters capture the now insoluble iron and manganese compounds.
Some of the now filtered water heads to the softeners which use a salt brine. Not all water is softened since too soft water can cause corrosion in pipes. The softened and unsoftened water are blended together in two clear well tanks. This water is rechlorinated, again with sodium hypochlorite, this time for disinfectant purposes.
There are three key treatment variables that affect water discoloration - the amount of chlorine and sodium permanganate used as oxidizers in the "iron tank" and the frequency that the filter layers in the bottom of the tank are backwashed to remove the captured iron and manganese compounds. This process was complicated because the raw water quality changed each time the process called for raw water since the wells are rotated. During the plant's initial startup not enough manganese was being oxidized and then removed by the filter layers in the "iron tank." However, when it was rechlorinated in the clear wells it was being oxidized, but that was after the filters. That discolored the water and that's what customers saw in their homes
health and businesses.
Village officials switched back to the old plant on July 24 to provide time to finetune the new plant. The automatic well rotation system has been temporarily disabled to reduce the variability. Specific levels of chlorine and sodium permanganate have now been set for each well. That process is quite time consuming. Too much sodium permanganate turns water pink. Plant operator Tom Boso said they tried to reach "pink water" concentrations for both wells and then worked backwards to get the right level. They have undertaken a similar trial and error approach to backwashing. That process is time consuming and eventually requirez the replacement of the costly filter media. The key is what is the point between too much and too little?
The new plant has been running in various test modes for a month. Water produced has been discharged to the canal. Water has been tested at several points in the process during each test, using the plant's quick test instruments backed up by results from an outside water testing laboratory. These test results are used to adjust the key treatment parameters.
A restart is set for next Tuesday with the treated water likely going into the distribution system. That restart will be closely monitored and the plant could shut down again if more adjustments are required.
Millersport has been working with Ohio EPA since the problems first appeared. "Ohio EPA believes that the engineers working with the water plant staff have determined the factors that caused the discolored water and those issues are being corrected," Ohio EPA environmental specialist Susan Applegate told The Beacon in an e-mail.
The water discoloration isn't an health issue. Water from the new plant was always safe to drink.