The final results have been received for the Monroe City Water Treatment Plant study. The yearlong study revealed five options for the City to consider improving overall water quality for the City’s customers. At the November 5 City Council meeting, engineers from Black & Veatch were present to report the findings from their study, giving a presentation.
Council members were told there are chemicals in the water source, including Magnesium, Ammonia and Carbon Chloride, which make it hard to produce quality water. The engineers explained by mixing and oxygenating Route J Reservoir’s water supply it will help overall improvement. The oxygen will reduce the odor and unpleasant taste by reducing algae.
Black & Veatch first looked at ways to improve the lake, Engineer Karen Dietze explained, “Aeration to the lake is critical no matter what option the City chooses. This will improve the taste and odor of the water, but won’t solve it completely.” Black & Veatch reported aeration of the lake should also improve the amount of chemicals being used.
Secondly, the study looked at ways to improve the plant. The conclusion reported five options to consider. Each option shows ways to eliminate the formation of total trihalomethanes (TTHM) and disinfection byproducts (DBP). The presentation included the explanation of each technical solution option the company suggested for improving treatment performance to maintain regulatory compliance. Black & Veatch also took into consideration the Chlorine Dioxide Pilot, which has been effective as a temporary treatment solution to produce safe and improved water for the City while the water study has been ongoing. The engineers noted the pilot option has produced quality water for the last two quarters of the testing period and maintained levels within regulation.
The first option is referred to as alternative one. The option suggests the City continue using the Chlorine Dioxide with chloramines as a secondary disinfectant. This option helps reduce chlorine demand.
The Pilot will have to continue until the City decides the long-term solution, Dietze stated, “Or this pilot is the long-term solution and is also the lowest cost option.” This plan also includes the installation of controls and monitors to be implemented at the plant. Mayor Potterfield inquired about the safety of the chemicals being used in the water and if this option was common practice. Dietze replied, “Yes the chemicals being used are safe and a large number of water plants use these practices with similar water sources.
The next option, alternative two, would also maintain the Chlorine Dioxide Pilot, but add aeration in the clear well to remove the DBP’s during a different stage of the water treatment process compared to the first option.
Black & Veatch reported alternative three is called Granular Activated Carbon adsorption and is very expensive. This option uses charcoal. Thermal activation of charcoal greatly improves its pore volume, surface area and structure making it a superb workhorse for water treatment. Adsorption is the primary mechanism by which GAC works and the primary reason it is widely used to reduce undesirable taste, odor and color and to improve the safety of drinking water by also effectively removing common disinfection byproducts (THMs), organic contaminants like chlorinated solvents and other industrial pollutants, pesticides, and select heavy metals such as lead and mercury.
The fourth option is alternative four, with reverse osmosis. This process removes all the elements, like magnesium and calcium, making the water aggressive, requiring the water to be treated with a lot of chemicals and pressure. This option is very expensive, Dietze stating, “This option would be extreme for what Monroe City needs.”
The last option, alternative five, is wholesale supply from Clarence Cannon Wholesale Water Commission (CCWWC). This alternative can only meet the demand of 600 gallons per minute. The demand needed for Monroe City is 1,000 gallons per minute. The report states the capital cost associated with switching to CCWWC is significant, essentially the same initial investment as implementing reverse osmosis at the treatment plant. However, the costs to purchase wholesale water $2.21 per 1,000 gallons is less than to treat water at the existing plant. Therefore, over time the cost gap between alternatives would narrow. Additional analysis is required to determine when and if this alternative becomes cost effective. Since CCWWC uses chloramines, this alternative should be compared with alternative one.
Dietze stated, “Whichever option the City chooses, providing aeration to the Route J Lake Reservoir water supply will be required.” The Board of Alderman ultimately will have to make a decision based on identifying the alternative that most effectively manages risk of future DBP violations, while balancing cost of implementation and impact to operations.
Black & Veatch made the recommendation to the Board of Alderman to consider alternative one. The total estimated cost to implement this alternative is $141,000. This alternative represents the lowest cost impact to the City and its rate payers, while providing a high degree of confidence that the treatment objectives will be met.