Tyler’s water disinfection is an involved process
Published 11:49 pm Saturday, November 7, 2015
- Plant Operator William Bushong records data Wednesday from a battery of tests performed daily on treated water at the Lake Palestine plant off Old Noonday Road south of Tyler. Andrew D. Brosig/Tyler Morning Telegraph
It takes roughly 14 hours of sanitation for a single gallon of water to go from Lake Palestine to the tap in Tyler.
During that time, the water travels between 9 and 10 miles and is treated with seven cleansing compounds and pulled through a carbon filter.
It is this process that has been in the news recently, first when the city notified residents Oct. 27 of a contaminant violation and then when consumer advocate Erin Brockovich subsequently took to Facebook questioning the city’s disinfection process.
The city last week responded to residents’ concerns by calling a news conference and announcing the city hired an outside company to evaluate the system. Those results should be back within the next two weeks, and the city pledged to share the results publicly.
City officials maintain the water is safe. Mayor Martin Heines sipped city tap water before Wednesday’s news conference.
But residents remain concerned, responding to Brockovich’s most recent Facebook post on Thursday with hundreds of likes and shares and more than 50 comments citing various problems with the water.
City officials said they are committed to giving Tyler Water Utility customers a quality product.
“Tyler water utilities and our employees interact with every resident every day of their life, but because of the quality of the water we produce, rarely do people give it much more than a first thought because it works,” Tyler Water Utilities Director Greg Morgan said. “You turn on the tap, and it’s there. You can depend on it.”
MIXED REACTIONS
The spike in contaminants that triggered the violation was the first such incident on record with the Texas Commission on Environmental Quality, which has records dating to 2004.
Tyler Water Utilities exceeded the federal and state allowable level of contaminants known as haloacetic acids, a byproduct that is caused when chlorine reacts with organic compounds in the water. The regulation allows 60 parts per billion of the byproduct in the water. The city’s supply tested at 62 parts per billion.
City officials maintain that spike came from a flood of organic compounds washed into Lake Tyler and Lake Palestine – the city’s primary water sources – during an abnormally wet spring. The city since has taken extra measures to decrease the haloacetic acids at its treatment plants.
Following the spike in measured byproducts, Tyler Water Utilities conducted a chlorine burnout from August until the end of September. The process is described as similar to shocking a pool and involves switching from chloramines to free chlorine to kill bacteria in the water pipes. The use of burnouts is one of the practices with which Brockovich’s team takes issue.
Residents responded to news of the contamination violation with concerns such as itchy skin and discolored and foul-tasting water.
Others said they had no problems with the city’s water or how it’s processed.
Dr. Harmonie Hawley said there’s no reason to panic. She is an associate professor at The University of Texas at Tyler’s civil engineering department, holds a doctorate in biothermal engineering and is a registered environmental engineer in the state of New Jersey.
“The elevated level is very low …,” Hawley said. “I don’t think panicking is the way to go, especially since this is the first violation of the guidelines. If you see repeated violations, that’s when something needs to be done to bring that back down to an acceptable level.”
The chemical byproducts are associated with an increased risk of bladder, colon and rectal cancers if exposed to the byproducts over a long period of time and are regulated by the Environmental Protection Agency based on consumption over a lifetime of 70 years.
From a public health perspective, the risk of not disinfecting drinking water (and exposing people to microbes that can cause gastrointestinal illnesses) far outweighs the risk of byproducts, particularly at the low levels typically found in U.S. water supplies, the Texas Commission on Environmental Quality said in an email.
The EPA establishes its thresholds based on the average person drinking about half a gallon of water daily for the average lifetime of 70 years.
Dr. Jeffrey Levin, an occupational and environmental health sciences professor for UT Health Northeast, expressed his confidence in Tyler water Wednesday after the city’s news conference.
“I’ve lived here for 28 years, and I have no concerns,” he said. “I drink the water daily. It’s probably better water, qualitatively, than most anywhere I’ve been.”
The disinfection method used by the city of Tyler is standard in municipal water systems across the South, said Dr. Gerald Speitel, associate dean of academic affairs at the C.W. Cook Professorship in Environmental Engineering at the University of Texas at Austin.
He said chloramines – a mixture of chlorine and ammonia, which is what Tyler uses – result in fewer chemical byproducts than straight chlorine, which can see increases in byproduct production in warm water.
CITY RESERVOIRS
The city treats an average of 29 million gallons of water a day, with a peak demand of 49.6 million gallons during the summer.
The system serves approximately 109,242 people through 36,414 residential service connections, according to the TCEQ. The water primarily is drawn from Lake Tyler and Lake Palestine, but the city also has eight active wells and four emergency wells.
Average production is far below the current system capacity of 72 million gallons daily. Tyler projects it will have ample water supplies to serve the city and Smith County until 2084.
Eight million gallons a day can be produced through its wells, and 64 million gallons is split between the Lake Palestine and Golden Road treatment plants. On any given day, half of the water supply comes from Lake Palestine and half from Lake Tyler. In the summer, the city leans heavier on Lake Palestine because it’s larger and deeper. Lake Tyler and Lake Tyler East cover a combined 114 square miles, and Lake Palestine, which is fed by the Neches River, covers 839 square miles.
Surface water requires more processing than ground water, said utilities director Greg Morgan.
“You really can’t compare surface water to well water,” he said. “Well water comes out of the ground – in our case 900 to 950 feet down. The potential of contaminants and organics in the water is low. It’s not really an apples-to-apples comparison.”
Cleaning water from Lake Palestine is more challenging than Lake Tyler, primarily because the Neches River feeds it. It contains more organic matter (trees, primarily) and has a level of algae that’s not present in Lake Tyler.
“It’s like any surface water supply. It will fluctuate depending on the seasons of the year; it will fluctuate depending on rainfall and things washed into the water,” Morgan said.
WATER PROCESSING
The city’s water process starts by pulling water out of the lake. At Lake Palestine, three vertical pumps can pull 30 million gallons of water a day. Generally only two pumps are used, and the third serves as a backup. Lake Tyler has the same system.
The pumps are on a concrete bridge and sit at varying depths in the water so they do not interfere with each other’s abilities, and a filter on the pumps helps minimize pulling fish into the facility.
Using the varying levels also helps pull oxygenated water from the lake, which generally has less organic matter in it, said Kevin Hukill, Lake Palestine Water Treatment Plant water system superintendent.
From the pumps, the water travels 9 or 10 miles through a 54-inch pipe directly to the water treatment plant, where all the cleaning happens.
If there’s a significant amount of algae in the water, copper sulfate is added to the pipe leading to the plant to give it a maximum amount of time to kill the algae.
At the treatment plant, the water is given compounds to settle out floating particles. After that, the water is given a dose of chlorine and pulled through a filter. The final step is the addition of ammonia before it’s sent out to the distribution system.
The process for Lake Palestine’s water differs slightly from Lake Tyler in that it receives a blast of ozone as a pretreatment when it reaches the plant. That blast helps kill off organic matter that is more prevalent in Lake Palestine’s water.
Liquid oxygen is charged with electricity to create the ozone, which is a gas. That gas is then pumped through the bottom of two large tanks and bubbles through the water, similar to a pump in a fish tank. The ozone is used in a closed system to keep it out of the air.
Any gas that makes it through the water without hitting an organic compound is captured in the closed system and converted back to oxygen.
SEDIMENT SETTLEMENT
The next steps in the process are designed to get floating particles out of the water.
The water is given three chemicals: alum (a form of aluminum), powdered activated carbon and a bit of lime.
Powdered activated carbon acts like a sponge in the water.
“It soaks up organic compounds that cause taste and odor problems, and then it settles out in the sedimentation process,” Hukill said, adding carbon is not used at the Golden Road plant, which services Lake Tyler’s water.
“We don’t have the same organics at that lake (as) Lake Palestine,” Hukill said. “It’s a bigger lake, and it has more timber in it. Lake Tyler doesn’t have a lot of that.”
The alum acts like a magnet. In a process known as flocculation, it pulls dirt and other organic particles to it, and eventually becomes heavy and sinks to the bottom of the tanks.
The lime helps with the pH of the water, to make the alum work at maximum efficiency, Hukill said.
Officials said trace amounts of these chemicals end up in the final water product, but the majority are filtered out before leaving the plant. Tests are conducted to make sure water leaving the plant is within acceptable ranges for those chemicals.
Once the chemicals are added, the water goes through a rapid mixer.
The sedimentation process takes the longest in the sanitation process. Once the chemicals are added, it takes roughly six hours to go through a series of pools. The water moves via gravity from one area to another, slowly becoming clearer and clearer as sediment settles to the bottom of the tanks.
A scraper cleans out the sediment that falls to the bottom and sends it to the wastewater sanitation plant.
CHLORINATION, FILTRATION
The final pool is called a “stilling well,” which gives the water a chance to be very still before it falls via a mini waterfall into an area where chlorine is added.
Falling water allows oxygen to come back into the water, which helps with taste.
A polisher that helps the filter be more efficient in catching micro particles is added with the chlorine.
The water then flows to the top of one of eight filters and is drawn downward through the filter, which is made of a layer of fine sand on top of 36 inches of anthracite coal – a type of carbon.
The final step is to add ammonia and sodium hydroxide, which helps with the final water’s pH.
Hukill said maintaining a stable water pH consistency “gives us optimum performance on our chloramines, which means we can use less disinfectant and achieve the same results we need in the distribution system and keep the chlorine residuals at state-mandated levels.”
Water is then put into one of two, 2 million-gallon underground storage tanks at the facility and then distributed into the water system.
CONTINUOUS TESTING
At the plant, water is tested every two hours.
Water in the sediment basins is tested for turbidity, which is a measurement of the amount of particles in the water, alkalinity, pH and temperature. Finished water is tested for pH, alkalinity, chlorine levels and turbidity,
Tests for bacteria are sent to the Northeast Texas Public Health District.
“We collect 106 to 117 bacteria samples a month …” Hukill said. “We get a representation of all four quadrants of town.”
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