What is wastewater

What is wastewater

Definition of wastewater

Wastewater is defined as the water left over from factories, companies, and farms, in addition to sewage from homes; Such as the water of swimming pools, toilets, showers, cleaning, etc., and for this reason, its pollution levels vary according to the place and how it is used. Therefore, wastewater treatment is very necessary for it to become usable again before it is returned to the water environment so that it does not increase more than its pollution.


wastewater components

Wastewater consists of 99.9% of natural water, and 0.1% of various pollutants that make it unusable. These pollutants include the following:

  • Nutrients: phosphorus and nitrogen.
  • Fats, oils, and lubricants: such as cooking oils and body lotions.
  • Pathogens: such as bacteria and viruses.
  • Biochemical oxygen demand: (in English: Biochemical Oxygen Demand); It is an indicator of the amount of oxygen that anaerobic bacteria need to break down organic materials in the water. A higher indicator indicates that there are more organic materials that need to be broken down in the water.
  • other solids.

wastewater sources

Wastewater sources are classified into two main sources as follows:

  • Domestic wastewater: usually generated from domestic activities; Such as cleaning, bathing, cooking, sanitary facilities, and others. It also includes the water that is drained from industrial and commercial buildings and institutions, and part of the groundwater, in addition to the water resulting from rainstorms. It should be noted that the treatment of domestic wastewater is becoming increasingly difficult; As a result of the increased quantities of chemicals entering domestic wastewater, such as medicines, personal care products, and others.
  • Industrial wastewater: It is the water resulting from industrial processes, and its treatment is more complex because it requires many tests during the treatment process, and it usually contains multiple pollutants, such as oils, medicines, pesticides, silt, chemicals, and other by-products.

Types of wastewater

There are two main types of wastewater, which are as follows:

  • Gray water:  It includes water from bathtubs, sinks, and washing machines, except for toilet water.
  • Blackwater: is the water coming out of the toilets, and the water emanating from the kitchen sinks, which are highly contaminated with cooking oils, grease, and food residues.

The importance of wastewater treatment

Wastewater treatment is defined as the process of removing impurities and pollutants from wastewater before it reaches groundwater sources or natural water bodies. such as oceans, lakes, rivers, and their estuaries, and the wastewater treatment process is important for preserving the environment and health in general, and the following are the most important reasons for wastewater treatment:

  • Preserving fisheries: Clean water is a key factor for animals and plants to live in the water and is therefore important for the fishing sector.
  • Preserving wild aquatic life: rivers, oceans, and others are linked to the lives of many creatures that depend on coasts, beaches, and swamps for food and rest, and are home to many fish and other aquatic animals.
  • Reducing health risks: Water contaminated with harmful bacteria transmits many diseases, and that is why it must be preserved and cleaned to be safe for everyone who approaches or relies on it.
  • Entertainment: Water areas are a source of luxury for many people, as some of them represent tourist areas that attract visitors to water activities. Like swimming, fishing, boating, and some others, it is a place to live for many people who prefer to live near the water.

How to treat wastewater

The wastewater treatment process takes place in 4 stages as follows:

  1. Primary treatment: includes the removal of large solids; Such as the waste that was wrongly discharged into the waterways from plastic containers and others, after that the water is passed through porous surfaces to get rid of small particles; such as sand and gravel, and finally the wastewater flows into large tanks and is left for some time until the rest of the solid materials such as mud settle, and the oily and foamy materials are also disposed of from the surface of the water.
  2. Secondary treatment: very small living organisms are added to the water, and their function is to analyze and dismantle the remaining dissolved substances in the water, so these organisms and other residues stick to the mud.
  3. Disposal of nutrients: Nutrients in wastewater cause; Such as nitrogen and phosphorus, the proliferation of algae and bacteria in waterways, which poses a threat to aquatic life, in addition to the visual pollution it causes, and dissolved oxygen is sometimes used to help marine organisms live, and it is worth mentioning that many water treatment plants exceed this stage because of the high cost required by their special equipment.
  4. Sterilization: At this stage, disease-causing microorganisms are disposed of in moderate-cost ways at the city level. This is done by adding chemicals to the liquid waste and exposing it to ultraviolet rays, and in some stations located in less densely populated areas, the liquid waste is collected for a certain period to ensure the death of all disease-causing microorganisms without the need for sterilization.
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