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The Wastewater Recycling Process

Wastewater recycling is conducted by communities as well as industries and households that consume large volumes of water. Commonly practiced wastewater recycling processes consist of primary and secondary treatment stages. Primary treatment involves physical and mechanical procedures, while secondary treatment comprises biological and chemical methods. Technological improvements in the recycling process have enabled the production of efficiently purified water suitable for reuse.

  1. Primary Treatment: Physical and Mechanical

    • The initial stage of the wastewater recycling process removes large contaminants, which are physically or mechanically separated from raw sewage. This is important as they can damage the treatment system. Subsequently, sewage enters a chamber, and its flow is sufficiently slowed to allow smaller contaminants to settle. Use of a primary clarifier further slows flow, enabling sewage to separate into layers such as fats and oils that float to the top and organics that sink to the bottom.

    Secondary Treatment: Biological

    • The biological phase of secondary treatment involves applying microorganisms to digest organic pollutants. Wastewater is pumped into an aeration basin containing oxygen and aerobic microbes that feed on the organic material present. The microbes are then captured along with all remaining settled bio-solids. Chemical pollutants present in wastewater can disrupt this stage by killing microorganisms; hence, it is encouraged that chemicals are adequately disposed.

    Secondary Treatment: Chemical

    • Once organic pollutants are removed, wastewater is subjected to chemical treatment. The most common chemical used in this stage is chlorine, which kills all microbes left behind from the biological treatment stage. Chlorine is applied as liquid, gas or solid granules. Sulfur dioxide is used to remove chlorine from the final product, to prevent contamination of freshwater and harming aquatic life. Although cost-effective, chlorine is highly toxic to store and is sometimes replaced with ultraviolet radiation.

    Benefits and Challenges to Wastewater Recycling

    • Wastewater recycling lowers the demand for natural water sources and reduces water pollution. Yet concerns have also been raised over its quality, particularly for drinking purposes, although these have been reduced as technologies improve. Disposal of industrial and household chemicals as well as agents used to clean treatment systems hinders the biological stage of recycling and needs to be addressed.

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