Process Water Management System Boosts Southern Star’s Recycling Effort

Before taking over as general manager of the Southern Star Concrete operations in Little Rock, Ark., Dan Davis spent time researching ready mixed reclaimer

Before taking over as general manager of the Southern Star Concrete operations in Little Rock, Ark., Dan Davis spent time researching ready mixed reclaimer systems as far back as 1994, when he was still overseeing the company’s Dallas-Ft. Worth area plants. He kept going back to the reclaimer design of Wisconsin-based Enviro-Port, because its systems are self-contained. Davis wasn’t as concerned with his return on investment in terms of money saved on water as he was in environmental issues. I feel that the return comes from the environmental preservation that takes place on the properties, that we are able to reuse 100 percent of our materials, and we’re not polluting the area around the plants, he says.

A 25-year ready mixed industry veteran, Davis currently manages seven plants. Beginning about five years ago, the Southern Star Little Rock facilities began adopting Enviro-Port’s process water management systems. Now, the company owns five unit, including one installed last year. Southern Star also bought an Enviro-Port reclamation system. Presently, Davis estimates that half-a-million gallons are sent through the equipment per month.

According to Enviro-Port, it can take a Type 1 reclaimer (sand and stone reclamation only) or stand-alone pit system and convert it into a Type 2 100 percent residual water rebatch system. The process water management system is a self-contained unit available in four sizes with 2,500-, 8,000-, 10,000-, and 17,000-gal. storage capacities. Size is determined by the batch plant’s water usage evaluation and production capabilities.

In terms of operation, the system uses a waste water pump system to agitate the process water containment pit. This, in turn, brings the settled portland cement solids and fine sand particles into suspension. Process water with suspended particles is pumped into the agitation tank. The tank is then filled to a predetermined set point where it is kept in agitated suspension. At this point, the fluid in the agitation can be chilled or heated depending on the climatic conditions with an Enviro-Port internal piping system. Product is then pumped to the batch plant for use in new mixes at predetermined ratios.

The specific gravity of the gray water is monitored with Enviro-Port’s completely automated software, which provides users on-screen solids readings. Furthermore, the company can take specific gravity indication one level further by retransmitting this value to the customer’s batch computer, thus permitting an automatic blending of gray water to fresh water. Customers also can choose to manually test their gray water with a hydrometer or weigh scale.

The above-ground construction of the process water management system also makes it easy to transport and relocate. Southern Star’s Davis adds that Enviro-Port was always quick to alert his company to any upgrade opportunities to his systems. I appreciated that whenever a change was introduced that Enviro-Port made it a point to notify us and allow us to upgrade, he says. The systems were easy to set up. However, training drivers on how to discharge into the hood of the system with the proper amount of ready mixed was part of a learning curve in adapting to the system. The batchman was able to become efficient with the system very quickly.

With the reclaiming system, returned ready mixed is poured directly into the intake hopper. Sand and stone are swept into the diagonal screw conveyor while residual water is kept in suspension in the agitation tank. Clean sand and stone are transported above the residual water level, where it is given a final rinse and stockpiled for reuse. (Separation can be performed with optional screen deck.) Residual water is metered back to the plant for reuse via a weigh batch or metering system. A plant’s existing process water and storm water can be introduced automatically into the Enviro-Port system for reuse in batching; the system can utilize this water rather than creating more.
Û Enviro-Port, 800/356-8106; e-mail: [email protected];