Reference terms from Wikipedia, the free encyclopedia

Sewage treatment

Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding environment or an intended reuse application, thereby preventing water pollution from raw sewage discharges. Sewage contains wastewater from households and businesses and possibly pre-treated industrial wastewater. There is a high number of sewage treatment processes to choose from. These can range from decentralized systems (including on-site treatment systems) to large centralized systems involving a network of pipes and pump stations (called sewerage) which convey the sewage to a treatment plant. For cities that have a combined sewer, the sewers will also carry urban runoff (stormwater) to the sewage treatment plant.

A large number of sewage treatment technologies have been developed. Very broadly, they can be grouped into high tech (high cost) versus low tech (low cost) options, although some technologies might fall into either category. To decide which sewage treatment process to choose engineers and decision makers need to take into account technical and economical criteria, as well as quantitative and qualitative aspects of each alternative.: 215  Often, the main criteria for selection are: desired effluent quality, expected construction and operating costs, availability of land, energy requirements and sustainability aspects. For example, broadly speaking, the activated sludge process achieves a high effluent quality but is relatively expensive and energy intensive compared to waste stabilization ponds which are a low cost treatment option but require a lot of land. In developing countries and in rural areas with low population densities, sewage is often treated by various on-site sanitation systems and not conveyed in sewers. These systems include septic tanks connected to drain fields, on-site sewage systems (OSS), vermifilter systems and many more. An advanced, fairly expensive, sewage treatment plant in a high-income country may include primary treatment to remove solid material, secondary treatment to digest dissolved and suspended organic material, tertiary treatment to remove the nutrients nitrogen and phosphorus, disinfection and possibly even a fourth treatment state to remove micropollutants (although this is still rare).

At the global level, an estimated 52% of sewage is treated. However, sewage treatment rates are highly unequal for different countries around the world. For example, while high-income countries treat approximately 74% of their sewage, developing countries treat an average of just 4.2%.

The treatment of sewage is part of the field of sanitation. Sanitation also includes the management of human waste and solid waste as well as stormwater (drainage) management. The term "sewage treatment plant" is often used interchangeably with the term "wastewater treatment plant".

Note:   The above text is excerpted from the Wikipedia article Sewage treatment, which has been released under the GNU Free Documentation License.

Check out these latest Nanowerk News:


Nanoparticle-formulated drug combination is effective in medulloblastoma, a pediatric brain tumor

Researchers have demonstrated that a novel combination of two drugs that act as targeted inhibitors, delivered in a nanoparticle formulation, extend the survival of mice with medulloblastoma.

Maize and milk proteins can replace fossil fuels and metals in the production of nanostructured surfaces

New research results open a future with more sustainably produced nanotechnology, where limited natural resources can be replaced with, among other things, maize and milk proteins.

Revealing lithium metal's electronic structure

Spectroscopy and theoretical calculations revealed the intrinsic spectroscopic signature of lithium metal and explained the origin of previous contradictory reports.

Scientists fabricate smart heat isolator

Researchers have developed a smart material that combines hollow multishelled structure TiO2 and a heat-sensitive polymer in order to automatically control heat transmission.

'Smart' saddle with triboelectric nanogenerators could help equestrians hit their stride (w/video)

Researchers have developed a prototype 'smart' saddle that could help equestrians improve their biomechanics. Moreover, the self-powered saddle can alert others when a rider takes a fall.

A bioelectronic tongue 'tastes' sweetness

Scientists have developed an ultrasensitive bioelectronic tongue that measures sweetness by mimicking human taste buds.

Disinfected with light: self-cleaning surfaces protect against the transmission of bacteria and viruses

By combining copper-doped titanium dioxide with layered silicates, researchers observed a synergistic effect that brings pathogenic bacteria and viruses more effectively into contact with the catalysts and accelerates their inactivation.

Silicon fluorescence shines through microcracks in cement, revealing early signs of damage

Researchers discovered by chance that common Portland cement contains nanocrystals of silicon that emit near-infrared fluorescence when illuminated with visible light.

Diamond quantum sensor detects 'magnetic flow' excited by heat

Researchers have successfully probe thermal-magnetic flow with a diamond-based quantum sensor, opening doors to heat-controlled quantum devices.

'Crazy' light emitters: Physicists see an unusual quantum phenomenon

Scientists have experimentally discovered an unusual quantum phenomenon for the motion of luminescent electronic quasiparticles in atomically-thin semiconductors.