Wash Water Recycle System Makes Capital A Zero-Discharge Operator

With ever-tightening standards and regulations regarding ground water contamination, mixer truck drivers are increasingly challenged to clean their vehicles

With ever-tightening standards and regulations regarding ground water contamination, mixer truck drivers are increasingly challenged to clean their vehicles in an environmentally acceptable manner upon return to the yard. Traditionally, drivers simply hosed down their chutes, allowing dirty water to pool on the ground or filter into storm sewers. Today, however, authorities are concerned about the effect this high-pH slurry water has on fish-bearing streams and ground vegetation. Many contractors are now required to provide water-tight washout containers at their job sites.

About five years ago, Don Voges, general manager of Lincoln, Neb.-based Capital Concrete, attended a National Ready Mixed Concrete Association environmental seminar dealing with ground water contamination and decided that his one-plant operation was not going to be part of the problem. He had heard about the Vancouver-based Enviroguard’s chute wash system when it won the 2002 NRMCA Environmental Innovation Award and decided it sounded like the answer to his problem. Since that time, Capital’s 15-truck fleet has become part of a zero-discharge facility that is able to filter and reuse its water and unused aggregate, thanks to this system.

Enviroguard uses an air-operated pump, which taps into the truck’s air system, to pull out any remaining material in the mixer drum or coming down the chute. Material is pumped to a bucket equipped with a removable screen, which is attached by the driver. Clean coarse aggregate stays in the bucket and can either be dumped out on site or used again for another mix. The remaining slurry water is pumped from the bucket back into the mixer drum to be reused in the next batch. All contaminants remain in the truck. According to Voges, washout time using Enviroguard averages the same as or slightly more than traditional washout methods.

Capital Concrete initially installed four systems for a trial run, and they worked just like they said it would, says Voges. When trucks return to the plant with slurry in their drums, they dump into a Scrommel 2418 Reclaimer, with a five-weir setup that screens for sand and small rock. By the time the slurry gets to the fifth weir, the water is clean.

The reclaiming system is connected to the plant’s primary water recycling and retaining structure, which also collects rain water and water used to clean vehicle exteriors. We have a 160,000-gal. concrete pond on site. Everything slopes to that, explains Voges. That’s free water. Shortly after we installed the water recycling system, someone from the city water company came out to inspect our water meter because of dropped usage in the first six to 12 months. Even during a drought, we don’t have to add any water to the system.

Voges estimates that it cost Capital $1,200 per truck for each 55-lb. Enviroguard system, which includes a pump, hoses, and all necessary hardware. One or two workers can install the system in a little over an hour. In order for the system to work, drivers have to buy into it, he explains. They’re hesitant at first because it adds a little more time to each load, but it’s only three to five minutes more. There’s no excuse not to use it all the time.

From an economic standpoint, having this system has helped us get jobs, says Voges. In an environmentally sensitive metro area, we’re known for not contaminating ground water. As far as I know, we’re the only one in our market area [about a 30-mile radius from the plant] and possibly even in the state using this method.
Û Enviroguard, 604/261-2211; www.enviroguard.ca