Top Sludge Dewatering and Management Techniques

It’s not the prettiest word in the English language, but sludge is a fact of modern life. According to a recent report, the United States produces about 7 million dry tons of it each year! Local governments are now required to treat waste water before the leftovers—sewer sludge—are safely recycled, incinerated, or buried in landfills. Here are the most common methods sewage treatment plants use for treating sewage sludge.

Sludge Thickening

With the help of gravity, sludge solids can be concentrated and removed from waste water. By increasing the solid content of the mixture to 5 or 6 percent, some of the contaminants in the water can be removed or destroyed. Because it does not reduce the mixture to a pure solid, thickening is generally used early on in the treatment process.

Sludge Dewatering

As its name implies, the dewatering process removes much of the liquid in the mixture and increases the solid content 15 to 30 percent. Air-drying, centrifugation, and belt processing (filtration) are also used to reduce the amount of contaminants.

Anaerobic Digestion

When waste water is kept in an oxygen-free environment for several weeks, anaerobic bacteria are encouraged to feed on the sludge. The natural result is a mixture that contains a higher concentration of solids, fewer pathogens, and the same amount of plant nutrients. As such, this treated sludge is more likely to be recycled and used as fertilizer.

Aerobic Digestion

By exposing waste water to oxygen, aerobic bacteria are allowed to feed on the sludge, decreasing volatile solids. The technique also increases solids content and reduces pathogens.

Alkaline Stabilization

Adding alkaline-rich materials, such as lime, to the mixture for several hours increases its pH level—which has numerous benefits. Not only does the technique reduce volatile solids, but it also decreases ammonia content.


After sludge dewatering takes the mixture closer to a solid state, an organic material high in carbon, such as sawdust, is added to the mixture. It is then composted for several days in an oxygen-rich environment. This technique helps reduce sludge volume and stabilize the remaining organic matter.

All of the aforementioned techniques help reduce the environmental impact of sewage sludge. M. W. Watermark provides equipment for sludge dewatering and solid/liquid separation, including filter presses, sludge dryers, and slant plate as well as dissolved air flotation clarifiers.

M.W. Watermark Sludge Dewatering and Management Techniques

Contact an M.W. Watermark Sales and Service team member today to learn more about sludge dewatering and management techniques for your particular application.

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About M.W. Watermark

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Top Sludge Dewatering and Management Techniques