Wastewater treatment

Overview of wastewater treatment processes and technologies

Medical Disclaimer: The information on WikiMD is provided as an information resource only, and is not to be used or relied on for any diagnostic or treatment purposes. This information should not be used as a substitute for professional diagnosis and treatment. Please consult your health care provider before making any healthcare decisions or for guidance about a specific medical condition. WikiMD expressly disclaims responsibility, and shall have no liability, for any damages, loss, injury, or liability whatsoever suffered as a result of your reliance on the information contained in this site. By visiting this site you agree to the foregoing terms and conditions, which may from time to time be changed or supplemented by WikiMD. If you do not agree to the foregoing terms and conditions, you should not enter this site.

Wastewater treatment is a process used to convert wastewater into an effluent that can be either returned to the water cycle with minimal environmental issues or reused. The latter is called water reclamation because treated wastewater can then be used for other purposes. The treatment process takes place in a wastewater treatment plant (WWTP), often referred to as a sewage treatment plant (STP) or water pollution control plant.

Overview

Wastewater treatment is a critical component of modern public health and environmental protection. The primary objective is to remove as much of the suspended solids as possible before the remaining water, called effluent, is discharged back to the environment. As solid material decays, it uses up oxygen, which is needed by the plants and animals living in the water.

Stages of Treatment

Wastewater treatment generally involves three stages: primary, secondary, and tertiary treatment.

Primary Treatment

Primary treatment involves the physical separation of large solids from the wastewater. This is typically achieved through screening and sedimentation. Large debris is removed by screens, and grit is settled out in grit chambers. The remaining water is then allowed to settle in large tanks, where heavier solids sink to the bottom and are removed as sludge.

Secondary Treatment

Secondary treatment is designed to substantially degrade the biological content of the sewage, which is derived from human waste, food waste, soaps, and detergent. This is typically performed by indigenous, water-borne microorganisms in a managed habitat. Secondary treatment systems are classified as fixed-film or suspended-growth systems.

• Fixed-film systems include trickling filters and rotating biological contactors.
• Suspended-growth systems include activated sludge and aerated lagoons.

Tertiary Treatment

Tertiary treatment is the final cleaning process that improves wastewater quality before it is reused, recycled, or discharged to the environment. This treatment removes remaining inorganic compounds, and substances, such as the nitrogen and phosphorus. It is also used to remove pathogens, which ensures that the water is safe for human consumption.

Advanced Treatment Technologies

In addition to the conventional treatment processes, advanced treatment technologies are employed to address specific contaminants and improve the quality of the treated effluent.

• Membrane Filtration: Utilizes membranes to remove particles and microorganisms.
• UV Disinfection: Uses ultraviolet light to inactivate pathogens.
• Ozone Treatment: Employs ozone gas to oxidize and break down pollutants.

Environmental and Health Impacts

Proper wastewater treatment is essential for protecting ecosystems and human health. Untreated wastewater can lead to the contamination of drinking water sources, spread of diseases, and damage to aquatic life. Effective treatment reduces the risk of waterborne diseases and helps maintain the balance of natural ecosystems.

Also see

• Water pollution
• Sewage treatment
• Water purification
• Environmental engineering
• Public health

External links

• National Pollutant Discharge Elimination System (NPDES)
• WHO Guidelines on Wastewater Treatment