Wastewater is characterized according to its physical, chemical and biological composition.

Depending on the level of pollutants and local regulations, physical, chemical and/or biological treatment will be used. Most of the time, the three treatments are combined to obtain the best water quality.

Wastewater characteristics vary considerably from industry to industry. Therefore, the specific characteristics will determine the treatment techniques to be used to satisfy the compliance discharge requirements.

Due to the large number of pollutants, characteristics are generally not considered for each substance. Materials with similar pollution effects are grouped into pollutant or characteristic classes.

Wastewater physical parameters

  • Color: Fresh wastewater is normally brown and yellowish, but over time it turns black.
  • Suspended solids: these are insoluble solids suspended in a liquid and visible to the naked eye
  • Temperature: For wastewater, it is correlated to the outside temperature while being warmer because almost nobody takes a cold shower
  • Turbidity: Due to suspended solids, wastewater will have higher turbidity.

Chemical characteristics of wastewater

Wastewater contains different chemicals in various forms, as shown below.

    • Chemical oxygen demand (COD): This is a measure of the amount of organic matter in wastewater based on the oxygen required to oxidize it.
    • Nitrogen: It is measured in its different forms: nitrite, nitrate, ammonia, and organic nitrogen (which is the amount of nitrogen present in organic compounds)
    • Phosphorus: It is generally measured in its mineral and organic form, total phosphorus
    • Chlorine (Cl-)
    • Sulfates (SO4-2)
    • Heavy metals

Biological parameters of wastewater

  • Biochemical Oxygen Demand (BOD) – BOD is the amount of oxygen required to stabilize organic matter using micro-organisms.
  • Oil and Grease – Oil and grease are generated from food waste and petroleum products.
  • Microbial life in wastewater: Wastewater contains the following microbes:
    • Bacteria
    • Protozoa
    • Mushrooms
    • Virus
    • Seaweed
    • Rotifers
    • Nematodes
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