Sludge is a semi-solid

slurry A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids or separating minerals, the liquid being a carrier that is pumped on a device such as a centrifugal pu ...

that can be produced from a range of industrial processes, from

water treatment Water treatment is any process that improves the Water quality, quality of water to make it appropriate for a specific end-use. The end use may be drinking water, drinking, industrial water supply, irrigation, river flow maintenance, water recrea ...

wastewater treatment Wastewater treatment is a process used to remove contaminants from wastewater and convert it into an effluent that can be returned to the water cycle. Once returned to the water cycle, the effluent creates an acceptable impact on the environme ...

or on-site

sanitation Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation systems ...

systems. For example, it can be produced as a settled suspension obtained from conventional drinking water treatment, as

sewage sludge Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term " septage" also refers to sludge from simple wastewater treatment but is connected to s ...

from wastewater treatment processes or as

fecal sludge Fecal sludge management (FSM) (or faecal sludge management in British English) is the storage, collection, transport, treatment and safe end use or disposal of fecal sludge. Together, the collection, transport, treatment and end use of fecal slud ...

from

pit latrines A pit latrine, also known as pit toilet, is a type of toilet that collects human feces in a hole in the ground. Urine and feces enter the pit through a drop hole in the floor, which might be connected to a toilet seat or squatting pan for user ...

and

septic tanks A septic tank is an underground chamber made of concrete, fiberglass, or plastic through which domestic wastewater (sewage) flows for basic sewage treatment. Settling and anaerobic digestion processes reduce solids and organics, but the treatme ...

. The term is also sometimes used as a generic term for solids separated from suspension in a liquid; this 'soupy' material usually contains significant quantities of 'interstitial' water (between the solid particles). Sludge can consist of a variety of particles, such as animal manure. Industrial wastewater treatment plants produce solids that are also referred to as sludge. This can be generated from biological or physical-chemical processes. In the

activated sludge process The activated sludge process is a type of biological wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa. It uses air (or oxygen) and microorganisms ...

for wastewater treatment, the terms "waste activated sludge" and "return activated sludge" are used. In

food processing Food processing is the transformation of agricultural products into food, or of one form of food into other forms. Food processing includes many forms of processing foods, from grinding grain to make raw flour to home cooking to complex industr ...

and beverage-making industries, sludge can have high protein content and other nutrients that can be used for beneficial purposes such as animal feed, thereby avoiding disposal at a

landfill A landfill site, also known as a tip, dump, rubbish dump, garbage dump, or dumping ground, is a site for the disposal of waste materials. Landfill is the oldest and most common form of waste disposal, although the systematic burial of the waste ...

References

{{Wastewater Environmental engineering Sanitation Sewerage