Floating snowmakers solve the problem of high humidity and low evaporation at Hargesheimer Water Treatment Plant.
Running both reverse osmosis trains at the Hargesheimer Water Treatment Plant posed the risk of overloading the three evaporation lagoons (39.5 million gallons total volume).
At full speed, each train generates 347 gpm of concentrate (500,000 gpd), but high humidity in summer reduces evaporation. “If the lagoons ever reached capacity, we’d have to shut down the trains during peak demand,” says Garry Houston, senior plant operator at the plant in Abilene, Texas. Draining concentrate slowly to a sewer wasn’t an option, as the inflow would upset the process at the wastewater plant.
In July 2009, operators installed a standard land model Turbomist evaporator by Slimline Manufacturing beside a lagoon. The unit sprayed 150 micron water droplets at 85 gpm to accelerate evaporation. “It helped, but it was a temporary measure until our 2015 upgrade,” says Houston.
That upgrade included a third-stage concentrator by H2O Innovation that went online in January 2016. The unit reduced concentrate to 145 gpm when run at a 58 percent recovery rate. At the same time, each lagoon received five 25 gpm floating SnowMakers built by SMI Evaporative Solutions. SMI SmartH2O software uses temperature and humidity to set the evaporators’ optimum water flow, sometimes as little as 2 gpm.
“If the temperature is 77 degrees with 73 percent humidity, the evaporators run at 8 gpm or 33 percent,” says Houston. “When the temperature goes up in the afternoon and the humidity goes down, the evaporators approach full speed. The other factor is wind. Any day it’s less than 20 mph is a calm day in Abilene, so the fine mist always evaporates before it can fall back into the lagoons.”
From December to February with temperatures below 35 degrees, the evaporators run very slowly or shut off. “It isn’t a problem because our water usage is down, we run the RO train slower, and less concentrate goes to the lagoons,” says Houston. “We have enough capacity to run both RO trains in an emergency.” The wind normally prevents ice from forming.