T019 Tri County SUD

Tri-County, in Riesel TX, has an arsenic removal system which reduces the arsenic concentration in their well water. The plant was commissioned by one of our competitors. The plant has a 3-filter system designed to treat their raw water from well #4 and #6. Both wells have a total capacity of 500 gpm flow. In addition to the filter system, a cooling tower, two intermediate storage tanks and a sludge tank are also installed at the plant. The temperate of the well water is about 150° F and the cooling towers reduce the temperature of the water to about 120° F. Once the water is treated, transfer pumps supply water to the elevated tank from where it is sent to the distribution system.

The client reached out to WETS in 2015 to perform a detailed pilot study because the arsenic plant did not meet expectations for arsenic removal from drinking water. WETS’ recommendations from the pilot study improved the performance of the arsenic plant; however, the issue with high tech instrumentation and operating controls still persisted and continuous plant supervision from the operator was required. Many chemicals were utilized in the process, all to no avail. Because of the complexities of the issues from plant maintenance, Tri-County ceased operation of the arsenic plant a few months later for about 6 years. Well water continued to flow to the storage tanks without any treatment. Only the cooling tower was utilized to reduce the temperature of the water. Because the well water was not being treated, Tri-county failed to comply with TCEQ’s arsenic requirements.

Another pilot study was conducted by WETS in July 2021 to determine a solution for their water treatment plant. Through the pilot study, WETS determined that an issue with fouling in the cooling tower system persists due to the presence of insoluble iron and manganese precipitates. The well water contains carbon dioxide which escapes once the water enters the cooling tower thus increasing the pH and converting the soluble Iron and Manganese to insoluble precipitates. This in turn, plugs the cooling tower internals. Orthophosphate is also utilized in the cooling tower process at Tri-County. Two pilot study procedures were performed by WETS. One study was performed at the well using raw water. The other pilot study was conducted using water samples containing orthophosphate from the GST which had gone through the cooling tower process. Based on the study, WETS recommended Tri-county a filter rehab project that included replacing the existing filter media and filter laterals, replacing valves, and adding a new chlorine line to activate the greensand within the filters. The use of orthophosphate was recommended to be continued to prevent the cooling tower from plugging.

WETS worked with Tri-county to make the adjustments and proposed changes to the existing arsenic water treatment system. New laterals with the correct sizing were manufactured at the WETS facility and the media was replaced with greensand and anthracite. Valves were replaced and the modifications were made to the control panel to successfully allow the arsenic plant to resume operation. The plant is still not operating as there are some minor issues with the electrical panels. We will update on our progress once the plant is operational.