At a time when consumers are becoming more aware of the need to save water and transitioning towards greener practices, the lesser-known water treatment plants are capturing more attention. These plants are responsible for transforming waste water that would otherwise be discarded and become pollutants into reusable water for agriculture and in plumbing or even further distilled and enriched with nutrients for drinking water.
The water treatment process at these plants takes place in stages through a network of sewers that are connected to homes, commercial buildings or other infrastructure such as streets and schools. These sewers continuously deliver the waste water and solids to the treatment plant’s tanks or basins.
At the water treatment plant, it all begins with the pre-treatment phase. It mainly involves the removal of large particles in the water which may include chunks of garbage such as rags, plastic, leaves, branches, cans, stones, and other waste. This is raked away through screens within the water basins that are also capable of handling overflow of water in case of heavy rainfall. At this stage, smaller particles like bacteria, chemicals, and oils can still remain in the water as it passes on to the next stage.
Next comes the primary treatment phase where a more thorough filtration and clarification of the water happens. Here, the water collects in large basins or sedimentation tanks allowing the smaller particles to settle at the bottom due to gravity while the grease and oil rise to the surface. The fats and chemicals are therefore skimmed off at the surface and scrapers direct the solid matter into the sludge treatment equipment.
This is followed by secondary treatment where the water is further agitated and aerated to break it down and add microorganisms to remove carbon and nitrogen from organic waste. For instance, some plants mix biomass with the waste to develop activated sludge that will be recycled while other plants pass the waste over a biofilm. Other technologies may also be used such as biological aerated filters and membrane bioreactors. The treated water is then collected in a secondary tank for further clarification.
Finally, the sludge treatment phase begins. Here, the remaining water and sludge is treated with the help of gravity that separates the organic waste from heavy particles which will be transferred to a landfill. The leftover sludge is centrifuged through a thickener where the then stabilised sludge can be transformed into fertilizer. The waste water on the other hand is treated again to remove other unwanted chemicals and disinfected before being returned to the water supply.
All in all, throughout this whole process, the water treatment plant cleans sewage to remove pollutants and restore the oxygen content for cleaner water.
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