Wastewater flows through the main channel to the inflow of the treatment plant and into the basin for trapping grit and sand. Here, a series of coarse and fine rake screens remove solids larger than 3 millimetres. The rake screens transfer the material ready for disposal to a container.
The wastewater is then raised to the level of the treatment plant by screw pumps and flows under gravity into the grease and sand trap. Heavier solids settle to the bottom while aeration in the basin enables oil and grease to float to the surface. The solids are pumped into the sand washer while surface skimmers remove the grease and discharge it into the sludge tank next to the primary clarifier.
The wastewater continues to flow into the two primary clarifiers where, over a period of two hours, solids larger than 100 micrometres settle on the bottom forming a layer of sediment known as the primary sludge. This sludge is scraped into the thickener by bridge scrapers. From the thickener, it is transferred to the sludge tank and from there to digesters.
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