The Larry D. Moore Water Treatment Plant (WTP) project had an extensive list of goals, including increasing the water treatment capacity from 2.76 to 4 million gal per day (mgd) with expansion capability to 8 mgd, improving disinfection byproduct results within the distribution system, reaching total organic carbon removal from raw water of at least 30%, containing water treatment operations within a building, and becoming capable of treating two different water sources and maintaining separate water streams through the facility.
“The project’s overall goal was to provide a water treatment facility that could meet the technical and financial needs of two utilities (Roxborough and its wholesale customer utility), while at the same time improve water quality and save their customers millions of dollars,” said William Goetz of TST Infrastructure.
The plant was required to be built on the same property as the existing WTP and had to maintain existing water distribution and treatment operations during the construction of the new facility. The WTP was to be designed for an ultimate water treatment capacity of 8 mgd to provide regionalization of water treatment with a neighboring district. However, it was only provided with equipment for 4 mgd.
About halfway through construction, the owner’s collaborative partner elected to proceed with construction of an additional 2 mgd of treatment capacity to provide a current treatment capacity of 6 mgd. The additional 2 mgd was constructed after the initial 4 mgd was operational. This had to be completed while maintaining operations to the new 4-mgd portion of the WTP.
The new facility was required to decrease disinfection byproduct values within the distribution system. To accomplish this, engineers decided to reduce total organic carbon removal compared to the existing water treatment facility. Ultraviolet (UV) disinfection was selected as a disinfectant component for the water treatment specifically for Giardia lamblia and Cryptosporidium. By using UV, a lower disinfection residual is required, and only a residual must be maintained within the distribution system.
“The biggest obstacle was to integrate the different interests, financial abilities, raw-water qualities and the customer needs of two very different utilities to regionalize water treatment of their respective communities,” Goetz said.
The design of the 8-mgd facility divided the plant into two completely separate treatment trains to accommodate and appropriately treat two potentially different qualities of raw water supplies. The design incorporated all the equipment required for Roxborough to achieve its needed 4 mgd immediately, while the wholesale customer was allowed to gradually phase in the equipment required for its 4 mgd of treatment.
It is the first water treatment plant in Colorado to receive credits for utilization of UV light as the primary disinfectant, which reduced chlorine dosage needs and disinfection byproducts.
The plant tap water placed third in a recent taste-test conducted by the American Water Works Assn. The substantial economy of scale resulting from the cooperative and innovative regionalization of two communities’ water treatment systems is estimated to have saved the customers millions of dollars.
“Perhaps the most remarkable achievement of the overall project was the innovative, flexible and cost-effective facility that evolved through the unprecedented close cooperation of Roxborough, its wholesale customer, legal counsel and financial analyst all working as a team,” Goetz said.
Roxborough and its wholesale customer’s needs were met with a flexible, cost-saving WTP that is expected to take them into the next century. Since starting operation, total organic carbon removal has increased to a total of approximately 60% removal. Disinfection byproducts within the distribution system have decreased by approximately 80% from approximately 80 ppb to 17 ppb.
“I’m proud to be part of the team that made the project such a success in its delivery of award-winning water quality, regionalizing treatment, meeting our wholesale customer’s needs and ultimately saving our customers millions of dollars,” said Barbara Biggs, general manager of Roxborough Water and Sanitation District.