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  • Glossary
| Last Updated:15/03/2024



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Aquaprivies Latrine

An aquaprivy is a tank filled with water into which excreta fall via a drop pipe. Aquaprivies use a simple water seal to prevent odours getting out of the tank and have a soak away to dispose of sullage and effluent. It is important that the drop pipe reaches below the surface of the water in the tank to prevent the escape of odours. The tank should be watertight to prevent pollution of groundwater and requires emptying about every three years.

Air Pollution

Five major classes of pollutants are discharged into the air: carbon monoxide, particulates, sulfur oxides, hydrocarbons, and nitrogen oxides. In addition to the automobile, other major sources are from combustion of fuel in electric power plants, industrial processes, and space heating, from the combustion in solid-waste disposal, coal-waste fires, and agricultural burning.

Aerobic digester

An aeration tank that is used to treat waste activated humus or primary sludges or a mixture of them, usually in a small plant with extended aeration or contact stabilization treatment. A typical operational problem associated with an aerobic digester is pH control. For example, when pH drops, this may indicate normal biological activity or low influent alkalinity. This problem is corrected by adding alkalinity, i.e. lime, bicarbonate, etc.

Agenda 21; global sustainable development

The global sustainable development agenda set out in the Rio Declaration on Environment and Development, which was established at the Earth Summit in 1992. Agenda 21 consists of 40 chapters, and at its roots are 27 principles. There are four broad sections which cover a range of issues: social and economic dimensions; conservation and management of resources for development; strengthening the role of major groups; and implementation. Agenda 21 highlights the importance of national strategies with international cooperation. It concludes proposals for the integration of environment and development issues in decision making and provisions for international institutional arrangements and legal mechanisms. Agenda 21 is an important document which has broad support among nations on all aspects of environment related to social and economic growth.

Anganwadi and school toilet facilities

Schools and in particular Anganwadis [Anganwadi workers and helpers are the grassroots level functionaries at village level for delivery of services under Central and State Government (of India) Schemes] are equally important places to address the health issues of the children provided that necessary infrastructure is available. Improved health and quality learning are not possible in schools and Anganwadis as long as basic hygiene is lacking or sanitary facilities and water supply are missing or broken or not properly used. Lack of healthy environment is already resulting in high infant mortality and under five-mortality rate. There are approx. 6 lakh Anganwadi Centers in India and most of them are without toilet facilities. These Anganwadi Centers reach out to 12.5 million children (ICDS, MoHRD).

Activated Sludge

Activated sludge is a process in sewage treatment in which air or oxygen is forced into sewage liquor to develop a biological floc which reduces the organic content of the sewage. In all activated sludge plants, once the sewage has received sufficient treatment, excess mixed liquor is discharged into settling tanks and the supernatant is run off to undergo further treatment before discharge. Part of the settled material, the sludge, is returned to the head of the aeration system to re-seed the new sewage entering the tank. The remaining sludge is further treated prior to disposal.

Aeration Tank

An aeration tank is a place where a liquid is held in order to increase the amount of air within it. The most common uses of aeration tanks are in wastewater recovery, as the high oxygen levels will increase the speed at which the water is cleaned. There are two main methods of aerating liquid: forcing air through the liquid or forcing liquid through the air.

Atomic absorption spectroscopy

Atomic absorption spectroscopy (AAS) is a spectroanalytical procedure for the quantitative determination of chemical elements employing the absorption of optical radiation (light) by free atoms in the gaseous state.


Nonliving, as in abiotic factor, which is a nonliving physical and chemical attribute of a system, for example light, temperature, wind patterns, rocks, soil, pH, pressure, etc. in an environment.


An aerosol can be defined as a system of solid or liquid particles suspended in air or other gaseous environment. 


Afforestation is the planting of trees for commercial purposes, usually on land supporting non-forest veld types, e.g. grassland or fynbos.


Reducing the degree of intensity of , or eliminating pollution.

Abatement Debris

Waste from remediation activities.


underground source of water.


The process of an organism adjusting to chronic change in its environment.


Non-living chemical and physical factors of the environment.

Acid rain

The precipitation of dilute solutions of strong mineral acids, formed by the mixing in the atmosphere of various industrial pollutants -- primarily sulfur dioxide and nitrogen oxides -- with naturally occurring oxygen and water vapor.


Man-made, not natural.

Aerobic action

A biological process promoted by action of bacteria in the presence of dissolved oxygen.

Aquatic Environment

All organic and inorganic matter and living organisms and their habitats that are related to, live or are located in or on the water at the beds of shores of a water body.

Avian flu

An infectious respiratory disease caused by the H5N1 virus which usually affects species of bird, but can be contracted by humans following close or direct contact with infected birds


A genetic allergic hypersensitivity that makes an individual more likely to develop allergic reactions to specific allergens


A family of fungal organisms and moulds mainly found in soil; some of which can cause moderate to severe disease in humans including allergic reactions, skin lesions and ulcers

Antimicrobial resistance

The ability of a micro-organism to resist the action of antimicrobial or antibiotic drugs


A substance that when introduced into the body stimulates the production of an antibody by the immune system


A group of medicines used to treat infections caused by bacteria, but are ineffective against infections caused by viruses

Antibacterial hand wash / wipes:

A hand cleaning product containing antibacterial agents which destroys harmful bacteria

Allergic reaction

The hypersensitive response of the immune system to an allergen, often causing swelling, itching, wheezing, nasal congestion and difficulty in breathing


A substance that triggers an allergic reaction in people who are sensitive. Also called an antigen

Ammonia loading rate

The average daily ammonia load present within the wastewater entering a plant expressed as kg NH4-N per m³ of filter medium per day.


Conditions where there is a lack of oxygen or sources of oxygen.

Activated Sludge Plant

A plant mixing aerated wastewater with a suspended biomass. A downstream settling tank is used to separate the clarified effluent form the biomass, which is recycled to the inlet of the works.

Advanced Primary Treatment

During wastewater treatment at the Point Loma Wastewater Treatment Plant, ferric chloride and organic polymers are added to the sedimentation tanks to help waste particles bond together in large enough masses to settle out.

Advanced Wastewater Treatment

Any treatment of sewage water that includes the removal of nutrients such as phosphorus and nitrogen and a high percentage of suspended solids.

Activated coal

This is the most commonly used adsorption medium, produced by heating carbonaceous substances or cellulose bases in the absence of air. It has a very porous structure and is commonly used to remove organic matter and dissolved gases from water. Its appearance is similar to coal or peat. Available in granular, powder or block form; in powder form it has the highest adsorption capacity.

Acid Deposition ("acid rain")

Water that falls to or condenses on the Earth's surface as rain, drizzle, snow, sleet, hail, dew, frost, or fog with a pH of less than 5.6.

Abandoned well

A well whose use has been permanently discontinued or which is in a state of disrepair such that it cannot be used for its intended purpose.


A measure of a substances ability to neutralize acid. Water containing carbonates, bicarbonates, hydroxides, and occasionally borates, silicates, and phosphates can be alkaline. Alkaline substances have a pH value over 7.


Farming of plants and animals that live in water, such as fish, shellfish, and algae.


Acequias are gravity-driven waterways, similar in concept to a flume. Most are simple ditches with dirt banks, but they can be lined with concrete. They were important forms of irrigation in the development of agriculture in the American Southwest. The proliferation of cotton, pecans and green chile as major agricultural staples owe their progress to the acequia system.


The process of reduction of a compound's concentration over time. This can be through absorption, adsorption, degradation, dilution or transformation.

Atomic number

A specific number that differs for each element, equal to the number of protons in the nucleus of each of its atoms.


Sediments deposited by erosion processes, usually by streams.


A site in electrolysis where metal goes into solution as a cation leaving behind an equivalent of electrons to be transferred to an opposite electrode, called a cathode.


Aquaclude Rocks and soils which transmit water with difficulty, e.g. clay, shale and unfractured granite.

Aqueous vapor

The gaseous form of water. See water vapor.

Anticorrosion treatment

Treatment to reduce or eliminate corrosion-producing qualities of a water.


The unit of measurement of electrical current. It is proportional to the quantity of electrons flowing through a conductor past a given point in one second and is analogous to cubic feet of water flowing per second. It is the current produced in a circuit by one volt acting through a resistance of one ohm.

Aerated Pond

A natural or artificial wastewater treatment pond in which mechanical or diffused air aeration is used to supplement the oxygen supply.


Policies which ensure protection of water quality for a particular water body where the water quality exceeds levels necessary to protect fish and wildlife propagation and recreation on and in the water. This also includes special protection of waters designated as outstanding natural resource waters. Antidegradation plans are adopted by each state to minimize adverse effects on water.


Tiny airborne droplets of water or other liquid. Aerosols are generated by misuse of high pressure hoses used to clean and sanitize equipment, floors, and drains. Microorganisms or harmful chemicals within aerosol droplets can rapidly spread through a plant. Workers should therefore protect exposed food and food contact surfaces when cleaning and sanitizing and use care when using high pressure hoses.


The action of one particle rubbing against the other in a filter media or ion exchange bed that can in time cause breakdown of the particles.

Assimilative Capacity

The capacity of natural water to receive wastewaters or toxic materials without negative effects and without damage to aquatic life or humans who consume the water.

Aqueous solubility

The maximum concentration of a chemical that dissolves in a given amount of water.


The condition of water or soil that contains a sufficient amount of alkali substance to raise the pH above 7.0.


Simple rootless plants that grow in sunlit waters in proportion to the amount of available nutrients. They can affect water quality adversely by lowering the dissolved oxygen in the water. They are food for fish and small aquatic animals.


Cauldron of boiling water used during trials by ordeal.

Aggressive water

Water which is soft and acidic and can corrode plumbing, piping, and appliances.

Amprometric titration

A way of measuring concentrations of certain substances in water using the electric current that flows during a chemical reaction.

Ambient medium

Material surrounding or contacting an organism (e.g., outdoor air, indoor air, water, or soil through which chemicals or pollutants can reach the organism.

Appropriative rights

"First in time, first in right” principle of allocating water rights based. Usually involves a user being allowed to take water from a particular source without regard to the contiguity of the land to the source.


Waterproof leggings.

Annular space

The space between two concentric cylindrical objects, one of which surrounds the other, such as the space between the walls of a drilled hole and a casing.


Life without water.


Reflecting or reflected light; sound or water.

Available chlorine

A measure of the amount of chlorine available in chlorinated lime, hypochlorite compounds, and other materials.

Acute Care

Health care provided to treat conditions that are short term and episodic in nature.

Absorption Trench

Excavation in fill or soil, being an ingredient of a leaching bed where a distribution pipe will be or is placed, which allows permeation of the effluent into the fill or soil.

Acoustic Logging

Acoustic Logging is a method of determining the location of a leak in a water main, by placing listening devices at known distances along the main.



A term meaning without water.


Arborloo is a type of composting toilet. Combining a user interface and a storage and composting pit. The shallow pit is filled with excreta and soil/ash and then covered with soil. The decommissioned full pit poses no immediate health risk and the contents will degrade naturally over time. Alternatively, a tree planted on top of the nutrient-rich pit will vigorously grow.


Transmission from human to human and potentially from human to animal.

Anaerobic digestion

a method of composting that does not require oxygen. This composting method produces methane. Also known as anaerobic composting

Aerobic composting

a method of com-posting organic wastes using bacteria that need oxygen. This requires that the waste be exposed to air, either via turning or by forcing air through pipes that pass through the material.

Asbestos Abatement

Procedures to control fiber release from asbestos-containing materials in a building or to remove them entirely, including removal, encapsulation, repair, enclosure, encasement, and operations and maintenance programs. (EPA Glossary)


A mineral fiber that can pollute air or water and cause cancer or asbestosis when inhaled. EPA has banned or severely restricted its use in manufacturing and construction. (EPA Glossary)


An underground water-bearing formation that is capable of yielding water. Aquifers have specific rates of discharge and recharge. As a result, if groundwater is withdrawn faster than it can be recharged, the underground aquifer cannot sustain itself. (WFL)

Application of Pit Humus and Compost

Compost is the soil-like substance resulting from the controlled aerobic degradation of organics. Pit humus is the term used to describe the material removed from a double pit technology (S.4, S.5 or S.6) because it is produced passively underground and has a slightly different composition than compost. Both products can be used as soil conditioners. 




Aerated Pond

Aerated ponds are aerobic wastewater treatment ponds (also called waste stabilisation ponds) in which the natural oxygenation is enhanced by mechanical or diffused air injection to achieve high rates of organic degradation and nutrient removal. Aerated ponds can treat almost all wastewater as long as they are biodegradable. Dependent on the type of treatment, a pre-treatment unit is required (e.g. settling, screening, etc.). If completely mixed, the aerated ponds also require a sedimentation step at the output. The process set-up is then in essence similar to activated sludge systems without sludge return. 


Activated Sludge

An activated sludge process refers to a multi-chamber reactor wastewater treatment unit to produce a high-quality effluent. Flocs of microorganism are suspended and mixed with wastewater in an aerated tank. As microorganism grow, they degrade organics and remove nutrients from the sludge and transform it to water, gas, energy and new cell material. To maintain aerobic conditions and to keep the activated sludge suspended, a continuous and well-timed supply of oxygen is required. An activated sludge unit is normally combined to a primary and tertiary treatment unit. Excess sludge produced through bacteria growth needs also to be removed regularly and treated appropriately. 



AAP Annual Action Plan

Adequate hygiene

Adequate hygiene: Level of hygiene sufficient for the prevention of public health risk.

ARWSPP :Accelerated Rural Water Supply Programme

AAP - Annual Action Plan