Sludge

The Highland Creek Treatment Plant - Primary settling: The next step in the treatment process is called Primary Sedimentation where the flow enters large tanks and its velocity is reduced, allowing settleable solids in the wastewater to settle to the bottom. Sludge collectors in the tanks sweep the settled sludge (called Raw Sludge) into sludge hoppers located on the bottom of the tank at one end, from where the sludge is pumped to a sludge blending tank. There are 12 Primary Sedimentation Tanks, four 48.4 m x 28.4 m rectangular tanks, and eight 18.3 m square tanks with a total volume of approximately 26,000 m3, and a total surface area of 8,177.4 m2. Activated sludge treatment: In the activated sludge process, effluent from the Primary Sedimentation Tanks is mixed with Return Activated Sludge from Final Sedimentation Tanks. This mixed liquor is aerated in Aeration Tanks. The activated sludge is made up of micro-organisms containing bacteria, which are a natural part of wastewater used to break down the organic solids in water.