Handling food processor wastewater treatment surprises with automatic scraper strainers

Strainers are designed for greater reliability than traditional options, working under unpredictable conditions such as varying pressure, particle size, solids load, and even sticky biologicals

By Del Williams, writer

For food processors, removing suspended solids such as fats, grease, grit, contaminants, and leftover process materials from liquids is necessary to comply with regulations like the EPA’s Clean Water Act, which sets wastewater standards for industry and national water quality criteria for pollutants in surface waters. To remain compliant, processors often use clarifiers, also known as settling tanks or settlers.

Clarifiers are designed to continuously remove the solids that accumulate due to sedimentation, the separation of suspended solids from a liquid by gravity. Concentrated impurities are discharged from the bottom of the tank while scum particles float to the surface of the liquid and are typically removed with strainers.

Although clarifiers are common, there are substantial limitations when conditions are unpredictable. The problem for wastewater treatment is that no fluid processing or filtration system remains static. Treatment conditions continually change due to variable factors such as pressure, particle size, solids loading, and even the presence of sticky biologicals.

“The flow rate and volume of suspended solids in the fluid changes depending on production demands and the equipment used as well as the time of day, day of the week, and seasonal factors,” said Robert Presser, vice-president of Acme Engineering.

Fortunately, a separation technology designed to tolerate variability – automatic scraper strainers – is used after clarifiers and before further processing when reliable, economic, low-maintenance water treatment is necessary. These self-cleaning scrapers filter out both tiny particles and larger debris, utilising a blade and brush that work together to keep all straining surfaces fully effective and free of obstruction.

The technology assures reliable straining that facilitates regulatory compliance. The approach also eliminates manual maintenance as well as equipment clogging and fouling issues with downstream water treatment processes such as membrane filtration, reverse osmosis, or ozone disinfection.

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