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Primary Water Treatments

When wastewater reaches a treatment plant, it must be treated and returned back to the environment where it flows down streams, evaporates into the atmosphere and even winds up in a drinking glass again. In order for this dirty water to be purified and become fit for use, it must go through many steps in the treatment process. Primary water treatment is where much of this process takes place.

  1. Screening

    • The initial step in primary water treatment is screening. Throughout its journey to the wastewater facility, water is likely to pick up solid material. The first step to removing the solids is to screen it. Screening means running the water through a screen filter so that larger pieces of debris cannot make it through to the next step.

    Aeration

    • Aeration is an important step in primary water treatment. Wastewater can take on foul odors and contain various gasses depending on its origin. To help remove its smell, water is simply shaken up to expose it to fresh air. Some of the dissolved gases are released from the water and then the water is sent into concrete holding tanks where more clean air is pumped through the water itself, according to the U.S. Geological Survey website.

      This process replenishes the oxygen in the water and helps keep organic material suspended while pieces of grit settle.

    Clarifying Tanks

    • Clarifying tanks are a series of tanks where the water sits undisturbed. Lighter impurities like oil and scum float to the water's surface, while sludge settles to the bottom. The tanks gently pump out the sludge from below while the scum on top gets skimmed away, according to the Ohio State University Extension website.

    Chlorination

    • Despite all efforts to purify the water through the primary treatment process, it still contains harmful bacteria that must be removed prior to being sent for further steps in the treatment process. Chlorine will help sanitize the water and kill the bacteria, according to the U.S. Geological Survey website. Since fish and other animals can be harmed by excessive chlorine, careful testing is done on the water to ensure levels are not too high. Sometimes other chemicals must be added to bring the levels down to acceptable.

    Solids

    • The leftover solids strained from wastewater are typically kept for several weeks in large "digesting" tanks where the materials are broken down and heat gets rid of harmful organisms within the waste. The remaining solids are buried in landfills or used for fertilizer.

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