ENVIS Centre on Hygiene, Sanitation, Sewage Treatment Systems and Technology

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.

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.

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.

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.

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 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.

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 (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. 

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.

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.

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

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.

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

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

A hand cleaning product containing antibacterial agents which destroys harmful bacteria

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

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.

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.