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Multi-purpose ponds last stage in process 
The oxidation ponds cover 230 hectares and are an important wildlife sanctuary - as well as removing a portion of the remaining pollution from the water and reducing micro-organisms. The end of the process is when the liquid is discharged into the estuary on high tides. Raw sludge from the primary sedimentation tanks and biological solids from the secondary sedimentation tanks are pumped to four digesters. The tanks are heated to 38deg and bacteria break down the sludge, releasing methane and carbon dioxide in the process. The sludge is stored in open lagoons before being dewatered and used on land as a soil conditioner or a fertiliser. The methane is used for driving the plant's machines and provides electric power for the national grid. The heat recovered is used to heat the digesters. picDigester tanks (near the entrance to the wastewater plant) contain sludge and make gas, which is used to power some of the engines at the plant. |
