Managing your wastewater output is just as important as managing the manufacturing process for your intended products. Difficulties can arise, though, when handling the byproducts that come from waste treatment. In particular, various forms of sludge can arise from filtering wastewater. Disposing of or processing this sludge is a logistics problem on its own.
Why Treat Sludge?
Sludge is composed of the residue removed from wastewater—this can include organic compounds, inorganic sediments, pathogens and more. Wastewater is treated to keep these contaminants from entering the water supply, but the sludge itself is now also a pollutant, more highly concentrated than the wastewater was. These contaminants can leach into the soil, and the water content itself can seep into the ground and compromise building foundations.
The Stages of Sludge Treatment
Sludge treatment aims to reduce the volume and toxicity of sludge byproducts in order to make handling easier. This is done through multiple mechanical and chemical stages, usually consisting of:
- Thickening: solid particulates are made to aggregate together more closely and settle out of the liquid solvent, thus reducing the volume of sludge present. This is primarily a mechanical process, but clarifying agents may be added to catalyze aggregation.
- Digestion: organic compounds and harmful microorganisms are broken down by anaerobic bacteria that are capable of processing large organic molecules. Not only does this reduce toxicity and volume further, it can produce biogas used for energy.
- Dewatering: remaining water is removed to compact the sludge as much as possible for transport or disposal. Mechanical sludge dewatering equipment is quicker and more effective than drying beds.
Possible Uses for Sludge
While sludge is often hazardous, with proper treatment it can be a useful byproduct depending on the source and contents. The digestion process yields biogas, as noted, often applied to powering the treatment facility. Provided there aren’t high quantities of heavy metals present, the dewatered sludge can be used for composting or fertilizer. This allows organic compounds to be returned to the soil, and the sludge itself is useful for agriculture.