WATER & WASTEWATER MANAGEMENT
downstream equipment from fouling, scaling, corrosion, and other forms of damage or premature wear due to contaminants present in the source water. For these reasons, cooling tower and boiler feed water are generally pre-treated. Membrane filtration is also used to treat non-potable water sources such as grey water and reclaimed/recycled “purple pipe” water. Because the membranes are made using
thin, porous sheets of material, failing to sufficiently pre-filter any large, suspended particles from the water can cause severe damage and fouling – leading to premature replacement and unnecessary maintenance, according to Robert Presser, vice president of Acme Engineering, a North American manufacturer of industrial self-cleaning strainers. “Most membrane filter manufacturers
recommend that all influents be pre- screened from 100 to 500 microns to maintain membrane filter efficiency,” says Presser, whose company is an ISO 9001:2015 certified manufacturer of environmental controls and systems with integrated mechanical, electrical and electronic capabilities. He adds that automatic scraper strainers are typically installed before the intake plenum of membrane filters, after the supply pumps.
EXTENDING MEMBRANE LIFE As an alternative to sand filters, centrifugal separators, and basket type strainers, automatic scraper strainers provide superior membrane protection while drastically reducing required maintenance. Automatic scraper strainers such as
those from Acme Engineering can provide continuous removal of suspended solids to comprehensively protect membrane systems. Te automatic units are motorised and designed to continually remove suspended particulates in industrial process water and wastewater to the specific size required down to .003 inches (75 microns). Conventional manual strainers can become clogged quickly due to limitations in straining area. When that occurs, cleaning or media replacement is required, which increases maintenance costs. Te other alternative for fine straining is automated backwash-style strainers of various designs. As particle sizes grow larger, however, large contaminants can jam up the backwash system or remain in the body of the strainer, requiring manual
removal and interruption of the process flow. With the automatic scraper
strainer, cleaning is accomplished by a spring-loaded blade and brush system, managed by a fully automatic control system. Four scraper brushes rotate at 8rpm, resulting in a cleaning rate of 32 strokes per minute. Te scraper brushes get into the wedge-wire slots and dislodge resistant particulates and solids. Tis approach enables the scraper strainers to resist clogging and fouling when faced with large solids and high solids concentration. It ensures a complete cleaning and is very effective against even organic matter “biofouling.” With this type of system, manual maintenance for cleaning is eliminated. Blowdown occurs only at the end of the intermittent scraping cycle when a valve is opened for a few seconds to remove solids from the collector area. Liquid loss is well below 1% of total flow. With so much to gain, chemical
processing managers worldwide should consider selecting an automated, self-cleaning system that is essentially “set-and-forget,” where automatic scraper strainers comprehensively protect delicate membranes and allow personnel to focus on other aspects of the facility.
Acme scraper strainer: screen and brush
ABOVE LEFT: Scraper strainers protect membrane systems ABOVE RIGHT: Acme scraper strainer used with membrane systems
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