By optimizing the fiber size at 0.1mm diameter and bladder pressure at 8 bar, 10 NTU turbidity and 8 mg/l suspended solids were achievable, corresponding to removal rates of 99% and 94%, respectively. The potential exists to reuse the filtrate as process water onsite because of the low total suspended solids (TSS) achieved.
The chart on page 44 shows a plot of turbidity, suspended solids, and flow rate achieved versus bladder pressure. The chart confirms that as bladder pressure increases, so does the level of filtration, and that the optimum bladder pressure for achieving a turbidity of less than 50 NTU is about 6.8 bar relating to a flow achievable from the test unit of about 450 l/h. Subsequent developments are showing greatly increased flows with similar filtration performance.
Visit www.fibrasolutions.com for more information, or telephone David Griffiths at 44 118 984 4077.CAPTURING PROBLEMS OUTSIDE THE GATES
Many producers have discovered that their responsibility to washout extends beyond their gates. Many local EPA regulators have identified chute washwater as a potential contaminate to groundwater.
Some contractors and developers have pushed the responsibility of chute washwater onto the producer.
According to Ron Lankester, marketing director for Enviroguard, a Vancouver, B.C., manufacturer of a drum-mounted washout system, home builders are taking a more serious approach to jobsite washout. Richmond America Homes, one of the largest home builders in the country, is talking of mandating that all of their ready-mixed producers monitor the discharge of their trucks at all times, says Lankester.
This might be one reason why his firm has sold more than 8000 units. The self-contained system enables the driver to wash down his discharge system without allowing process water to spill on the ground.
The driver hangs a capture bucket at the end of the chute; the bucket has a screen to separate any coarse aggregate from the process water. While the driver is spraying the chute, the process water is pumped back into the mixer's drum by a small auxiliary pump from the bucket's outlet. When the driver is finished, he empties the bucket's remaining contents into the drum.
This process takes the same time as a normal washout. When the truck returns to the plant, the process water and drum clean-out are emptied into the recycling system.
Visit www.enviroguard.ca, or telephone 604-861-7805.