What is Sewage Sludge?
This is a by-product of wastewater treatment. It contains organic chemicals, thus a need to treat it to avoid environmental repercussions. Let’s explore some approaches to use in sludge treatment.
Sludge Thickening
In this process, a gravity thickener is used to reduce the sludge’s volume to make it easy to handle. Alternatively, dissolved air floatation may be used, where air bubbles are used to thicken the sludge, causing the solid mass to float at the top.
Sludge Digestion
Sludge digestion is where all the organic solids in the sludge are broken down into stable substances. During this process, total solid mass is reduced, and all pathogens are destroyed, easing the dewatering process. This entire process results in a mixture of carbon dioxide and methane used to power the digestion tank and generate power.
Dewatering
Dewatering bags are very efficient in dewatering sludge. Sludge drying beds is another method, but it is very slow and takes a long time to dewater the sludge. Centrifugation is a preferred approach by waste management plans. In this process, sludge passes through a centrifuge, making it easy to retrieve all the water from the sludge, enabling easier handling of the solid waste. Other sludge or wastewater dewatering techniques are belt filter press and rotary drum vacuum filter.
Disposal
After effective dewatering of the sludge, it can be used as fertilizer. If the sludge has high toxic levels and cannot be reused or buried, it can be burnt up and converted into ash.
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