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How to turn sewage sludge into concrete

water treatment plant

Malaysian researchers have developed a method to deal with wastewater sludge – turn it into concrete.

Malaysian wastewater plants for sewage treatment have a sludge problem, and it’s getting worse.

Sludge volumes are expected to rise, but environmental legislation means there are few options for disposal.

Burial is not an option because the sludge has a high heavy metal content.

Researchers from the Universiti Teknologi Mara think the solution could be to mix the sludge with cement to produce a concrete mixture to meet demand for materials on the country’s building sites.

The first step is to dry the wet sludge cake before grinding and sieving it to produce domestic waste sludge powder. This powder is then mixed with cement.

The researchers have experimented with 3, 5, 7, 10 and 15% sludge powder proportions in a cement to produce normal strength and two higher strength grades of concrete.

The results have been somewhat mixed. Concrete with added sludge powder decreased in compressive strength as the sludge powder proportion in the mix increased.

Water absorption and water permeability increased with higher sludge powder concentrations.

But mixtures with the highest sludge powder concentration – 15% – were found to have increased resistance to salt. 

Researchers now hope to improve the sludge powder’s quality with higher temperature incineration during the preparation stage – experimental temperatures will range from 600°C to 1,000°C.

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