Glossary

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  X  Y  Z

A

Activated sludge: Activated sludge itself is an aqueous suspension of microorganisms cultivated in a waste treatment process to break down organic matter into carbon dioxide, water, and other inorganic compounds. The activated sludge process has three basic components: 1) a reactor in which the microorganisms are kept in suspension and aerated; 2) liquid-solid separation; and 3) a sludge recycling system for returning activated sludge back to the beginning of the process. The activated sludge process is a common method of secondary (biological) sewage (wastewater) treatment.

Advanced (tertiary) treatment: Treatment step added after secondary treatment stage to remove specific pollutants, such as nutrients, suspended solids, organics, heavy metals or dissolved solids (such as salts).

Aerobic: Living or taking place in the presence of air or free oxygen.

Anaerobic: Living or taking place without air or free oxygen.

Aquaculture: Raising plants or animals in water (water farming)

B

Biogas: Gas consisting mainly of methane produced by anaerobic digestion of organic waste. Biogas can be produced and collected at community wastewater treatment works, or in smaller scale household biogas plants, as has been practiced widely in China and South Asia.

Black water: Wastewater from the toilet, which contains heavy fecal contamination and most of the nitrogen in sewage.

Biochemical Oxygen Demand (BOD): BOD is the measure of the amount of oxygen required by bacteria to stabilize material that decomposes under aerobic conditions. BOD is a commonly used determinant of the organic strength of a waste, as it serves as an indicator of the waste’s capacity to remove oxygen from water.  Oxygen concentrations in water determine the quality of fish and other organisms that can survive and flourish in the water; severe oxygen depletion can create offensive conditions, including bad smells.

C

Composting latrine/composting toilet: (also called biological toilets, dry toilets and waterless toilets). These contain and control the composting of excreta, toilet paper, carbon additive, and, optionally, food wastes. Some composting toilets aim to separate urine (urine diversions toilets) to control the moisture of the compost.

Constructed Wetlands:  Engineered systems designed to optimize the physical, chemical, and biological processes of natural wetlands for reducing BOD and TSS concentrations in wastewater.

D

Desludging: Removing accumulated sludge from septic tanks, aqua-privies, etc.

Disability adjusted life years (DALYs):Public health metric of healthy life years lost to disease due to both morbidity and mortality, adjusted for disability.

Disinfection: The inactivation of disease-causing organisms using chemicals, radiation (also solar), heat or physical separation processes.

E

Ecological Sanitation (ecosan): Sanitation the design of which strives to protect ecosystems, and treats excreta as a valuable resource to be recycled. The term is widely understood to reflect this general approach to excreta management, but ecosan technology often implements the approach through the separation of urine and feces at the level of the individual toilet.

Effluent: Out flowing liquid.

Enabling Environment: Policies, financial instruments, formal organizations, community organizations and partnerships which together support and promote needed changes in hygiene practices and access to technology.

Environmental Sanitation: A wide range of interventions designed to create and maintain an environment conducive to human health. This includes sanitation (defined as the infrastructure and services required for the safe management of human excreta) but also includes solid waste management, drainage of surface water and sullage, vector control, air pollution control, etc.

Escherichia Coli (E.coli): A bacterium found in the gut of warm blooded living beings, used as an indicator of fecal contamination.

Excreta: Feces and urine.

F

Facultative Pond: A pond which is aerobic near the surface, but anaerobic at lower depths.

Facultative: The ability of microorganisms to live under either aerobic or anaerobic conditions.

Fecal Coliform Bacteria: Common, harmless forms of bacteria that are normal constituents of human intestines and found in human waste and in wastewater. Fecal coliform bacteria counts are used as an indicator of the possible presence of pathogenic microbes. (see E.coli above).

Fecal sludge: Fecal sludge is the solid or settled contents of pit latrines and septic tanks.  Fecal sludge differs from sludge produced in municipal wastewater treatment plants. Fecal sludge characteristics can differ widely from household to household, from city to city, and from country to country. The physical, chemical and biological qualities of fecal sludge are influenced by the duration of storage, temperature, intrusion of groundwater or surface water in septic tanks or pits, performance of septic tanks, and tank emptying technology and pattern.

Fecal-oral: Transmitted by any route enabling fecal material to reach the mouth.

G

Greywater: Water from the kitchen, bath, laundry and other domestic activities which should not normally contain much urine or excreta.  (Note that laundry wash water is likely to carry some fecal contamination).

Grit: Heavy mineral matter such as sand and gravel, usually removed before primary treatment.

Groundwater Table: The level at which the subsoil is saturated with water.

Groundwater: Water found below ground level in the soil.

H

Hygiene Education: An element of hygiene promotion concerned with teaching people about how diseases spread; for example through the unsafe disposal of excreta or by not washing hands with soap after defecation. Although this type of awareness-raising may be part of a larger hygiene promotion program, it should not be the sole focus of the program.

Hygiene Promotion: A planned approach to preventing sanitation-related diseases through the widespread adoption of safe hygiene practices. It begins with and is built on what local people know, do and want.

Hygiene: Behaviors related to the safe management of human excreta, such as  handwashing with soap or the safe disposal of children’s feces. Hygiene thus determines how much impact water and sanitation infrastructure can have upon health, because it reflects not the construction, but the use, of such facilities.

M

Maturation Pond: An aerobic pond for wastewater treatment, usually the final pond in a waste stabilization pond system.

N

Night Soil: Human excreta transported without flushing water

O

Off-site sanitation: System of sanitation where excreta are removed from the plot occupied by the dwelling and its immediate surroundings.

On-site sanitation: System of sanitation where the means of collection, storage and treatment (where this exists) are contained within the plot occupied by the dwelling and its immediate surroundings.

Organic Matter: Materials which come from animal or vegetable sources. Organic matter generally can be degraded by microorganisms.

P

Pathogens: Disease causing organisms. The main organisms that pose a threat to health related to poor sanitation are pathogenic bacteria, viruses, parasitic protozoa and helminths that are excreted in large numbers from infected individuals. Many of these organisms have low infectious doses (e.g., helminths, protozoa and viruses) which means that only small quantities of infectious agents are needed to infect a new host (the infective dose varies between organisms and with respect to the susceptibility of the exposed individual).

Pit Latrine: latrine with a pit for collection and decomposition of excreta and from which liquid infiltrates into the surrounding soil.

Pour-flush Latrine: Latrine that depends for its operation of small quantities of water, poured from a container by hand, to flush away feces from the point of defecation.

Primary Treatment: Initial wastewater treatment process to remove solids which settle by sedimentation, and floating objects by physical screening and skimming.

S

Sanitation Marketing: The use of marketing techniques to promote the construction and use of sanitation facilties.  Sanitation marketing considers the target population as customers. It borrows private sector experience to develop, place and promote an appropriate product: in this case the product is a toilet and excreta disposal system, be it sewerage connection, pit latrine or other mechanism. Critically the facilities must be readily available at an affordable price in the right place.

Secondary treatment: Wastewater treatment step following primary treatment to remove biodegradable dissolved and colloidal organic matter by using biological processes, such as activated sludge, trickling filters, or various kinds of ponds and lagoon systems.

Sanitation Promotion: Activities undertaken to stimulate household demand for, and the supply of, the sanitation hardware necessary to maintain a healthy environment: latrines, toilets, sewer connections, etc.

Septage: Fecal sludge removed from septic tanks

Septic Tank: An underground tank that treats wastewater by a combination of solids settling and anaerobic digestion. The effluents may be discharged into soak pits or small-bore sewers, and the solids have to be pumped out periodically. Emptying septic tank sludge and final disposal of this septage is a challenge to many countries, developed and developing alike.

Sewage: Human excreta and waste water, flushed along a sewer pipe.

Sewerage: A system of sewer pipes, manholes, pumps etc for the transport of sewage.

Sludge: A mixture of solids and water deposited on the bottom of septic tanks, ponds, etc. The term sewage sludge is generally used to describe residuals from centralized wastewater treatment, while the term septage is used to describe the residuals from septic tanks.

Sullage: Domestic dirty water not containing excreta. Sullage is also called grey water.

Suspended Solids: Solids that are in suspension in water or other liquids.

T

Total Solids: The sum of dissolved and suspended constituents in a sample, usually stated in milligrams per liter or percent.

V W

Vector: Insect or organism that carries disease from one animal or human to another (such as a mosquito, fly, or bilharzia-infected snail.)

VIP Latrine: (Ventilated Improved Pit latrine.) A VIP is a pit latrine with a slab and a ventilation pipe to remove foul smells from the pit and vent them to the air above the superstructure roof line. A fly screen is added to the top of the ventilation pipe to control flies. 

Wastewater:  The spent or used water from homes, communities, farms and businesses that contains enough harmful material to damage the water's quality. Wastewater includes both domestic sewage and industrial waste from manufacturing sources.

Water table: The level in the ground at which water is found when a hole is dug or drilled (same as Groundwater Table).