Absorption is the incorporation of a substance in one state into another of a different state (e.g. liquids being absorbed by a solid or gases being absorbed by a liquid).

Absorption chillers are refrigerators that use heat energy as an input, rather than mechanical energy. Absorption chillers are useful, where electricity is no available or where there is an easily available source of heat (e.g. sun, hot water). The heat is used to evaporate a liquid to a gas. The gas then moves to the condenser where the heat dissipates and the gas is turned back into a liquid. Then, the cooled liquid is directed into the evaporator, where it turns into a gas and pulls heat from the air. Then the gas moves from the evaporator into the compressor and the process starts again.

An accumulation tank or a continuously fed batch is characterised by an increasing effective reactor volume with time. When the reactor is full and reaction time is over, it is emptied and refilled again as batch reactors.

Acetogenesis is the third step of anaerobic digestion. Products from fermentation (organic acids, alcohols) are converted into hydrogen (H2), carbon dioxide (CO2) and acetic acid (CH3COOH). To produce acetic acid, acetogenic bacteria need oxygen and carbon. For this, they use the oxygen solved in the solution or bound-oxygen. Hereby, the acid-producing bacteria create an anaerobic condition, which is essential for the methane-producing microorganisms responsible for the further step of anaerobic digestion which is methanogenesis.

Acidic is an adjective describing the properties of having a pH below 7. Its opposite is alkaline or basic.

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.

The process by which molecules of a substance, such as a gas or a liquid, collect on the surface of another substance, such as a solid. The molecules are attracted to the surface but do not enter the solid's minute spaces as in absorption.

Learning opportunities for adults exist in a variety of settings, ranging from a formal institution to day to day practical learning at work. It is important to acknowledge prior knowledge and experiences of learners, including their ability to recognize their own skills as lifelong learners. Considerations for adult development and learning include biological and psychological development and socio cultural and integrative perspectives on development.

Advanced facultative ponds are the first step in advanced integrated wastewater pond (AIWP) systems. They consist of a conventional facultative pond, containing a digestion pit on its bottom, where solids are trapped and transformed into methane by anaerobic digestion. The surface aerobic layer is about 1 meter deep and helps reducing potential odour problems. Biogas may be collected using a submerged gas canopy and potentially used for energy production.

Advanced integrated wastewater pond systems are improved conventional waste stabilisation pond (WSP) systems and are based on a series of four advanced ponds: An advanced facultative pond (AFP) containing a digester pit which functions much like an anaerobic pond integrated into the facultative pond; A high rate pond (HRP), covered by algae which provide oxygen to the water and take up organics and nutrients; An algal settling pond (ASP), where most of the algae produced in the HRP is removed; And finally an maturation pond (MP) for biological and solar disinfection.

The term advanced oxidation processes (AOP), describes a series of processes which are used for the chemical treatment of organic and inorganic pollutants in wastewaters. AOPs are based on the generation of reactive oxygen species (ROS) such as hydroxyl radicals. Generating hydroxyl radicals is possible via various ways such as photocatalytic, electrochemical, sonochemical. Typical AOPs are H2O2/hv, ozone/hv, ozone/H2O2/hv, TiO2/hv, (photo-)Fenton systems and electrochemical processes.

Advanced wastewater treatments, in opposition to natural systems require generally highly engineered biological processes, which leads to a reduction in space requirement to achieve similar performances. However, due to the complexity of the process and the high requirements for energy and operation and maintenance, advanced systems inhere a higher risk of technical failure.

Advection fog is a certain type of fog, that requires a steady wind that moves a fog layer that has formed upwind of a given site.

Advisory Services in Environmental Management

Advocacy is the action of delivering an argument to gain commitment from political and social leaders and to prepare a society for a particular issue (DE JONG 2003). Advocacy involves the selection and organisation of information to create a convincing argument, and its delivery through various interpersonal and media channels (e.g. public speaking, project visits, petitions, engaging celebrities, radio and newspaper). Influencing and involving important leaders is one of the essentials of advocacy, because political support together with support from community leaders and religious leaders can give a water-related project or campaign a powerful boost (SCHAAP & VAN STEENBERGEN 2001).

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.

Describes biological processes that require oxygen to drive cellular respiration and store energy.

Aerobic digestion describes the microbial transformation of organic matter into water, heat and CO2 in presence of oxygen. Aerobic digestion is used in wastewater treatment to both organic matter and the volume of sludge. As for anaerobic digestion, process rates increases with increasing temperature. Aerobic sludge digestion facilities may be designed for batch or continuous flow operations and the process results in approximately 50% reduction in solids content for typical municipal wastewaters. Typical wastewater treatments, using aerobic digestion are activated sludge systems, trickling filters, aerobic ponds etc.

A lagoon that forms the third treatment stage in waste stabilization ponds (WSP). It is a shallow pond with large surface area to enable light penetration and oxygenation by wind mixing. The effluent is generally free of pathogens but rich in nutrients and can be reused for fertigation or aquaculture.

Aerobic wastewater treatments use aerobic microorganisms to transform pollution into a variety of oxidized end products, carbon dioxide, and metabolized biomass. Generally, aerobic wastewater treatment is faster than anaerobic treatments but require the supply of oxygen, which can be expensive, and energy consuming.

Aeroponics is the process of growing plants in an air or mist environment without the use of soil or an aggregate medium. The word "aeroponic" is derived from the Greek meanings of "aero" (air) and "ponos" (labour). Unlike hydroponics, which uses water as a growing medium and essential minerals to sustain plant growth, aeroponics is conducted without a growing medium. Aeroponic equipment involves the use of sprayers, misters, foggers, or other devices to create a fine mist of water to deliver nutrients to plant roots. Because water is used in aeroponics to transmit nutrients, it is sometimes considered a type of hydroponics.

Anaerobic microorganisms, which are not sensitive to oxygen and can growth both in its absence and in its presence.

African Development Bank

African Development Fund

African Ministers Conference On Water

African Union

The first UN Conference on Environment and Development in 1992 adopted an agenda for environment and development in the 21st Century. This “Agenda 21: A Programme of Action for Sustainable Development” reaffirmed that sustainable development was delimited by the integration of the economic, social and environmental pillars. The “Agenda 21” is not legally binding, a reason to be criticised by many.

Soil particles can stick together and build aggregates where water can be enclosed.

Agricultural issues provides background knowledge that is necessary to understand loop-oriented approaches in the management of water and wastewater - such as soil properties, plant requirements, etc.

Agricultural wastewater is all waters that have been used in agriculture and are refused. They are either biodegradable (most often) and can be treated and reused similar to blackwater (e.g. manure from livestock); or they are not biodegradable (e.g. water containing a lot of residues from pesticides etc.) and require an advanced oxidation processes for treatment.

Air stripping is the transferring of volatile components of a liquid into an air stream. It is a chemical engineering technology used for the purification of groundwater and wastewater containing volatile compounds.

Algae Settling Pond follow the high rate algae pond in a advanced integrated pond systems. They are designed to settle out algae, and especially important if the water from the high rate algae pond is to be used for crop irrigation. The hydraulic retention time in algae settling ponds are of about two days and the harvested algae can be used as a nitrogen-rich fertilizer, or as protein-rich animal or fish feed (for further cultivation of high protein foodstuffs), modern medicine and even cosmetics for the idle.

A rapid increase in the population of algae in an aquatic system, e.g. as a result of an excess of nutrients (particularly phosphorus and nitrogen). As more algae and plants grow, others die. This dead organic matter becomes food for bacteria that decompose it. With more food available, the bacteria increase in number and use up the dissolved oxygen in the water. When the dissolved oxygen content decreases, many fish and aquatic insects cannot survive.

Alkaline is an adjective describing the properties of having a pH greater than 7. It is the opposite of acidic.

The alkalinity measures the capacity of water to neutralise acids. The alkalinity depends on amount of carbonates, bicarbonates, hydroxides, and occasionally borates, silicates and phosphates. Alkalinity stabilises water at pH levels around 7 (neutral). However, high water acidity decreases alkalinity and may cause harmful conditions for aquatic life. Alkalinity is expressed in ppm or mg of calcium carbonate per litre (mg/L CaCO3).

An alluvial river is a river in which the bed and banks are made up of mobile sediment and/or soil. Alluvial rivers are self-formed, meaning that their channels are shaped by the magnitude and frequency of the floods that they experience, and the ability of these floods to erode, deposit, and transport sediment. As such, alluvial rivers can assume a number of forms based on the properties of their banks; the flows they experience; the local riparian ecology, and the amount, size, and type of sediment that they carry. These forms can be meandering, braiding, wandering and (occasionally) straight.

Colourless astringent compound that is a hydrated double sulphate of aluminium and potassium, used in water purification.

See ammonium.

Ammonia nitrogen (NH4-N) is found in aqueous solutions as ammonium ion (NH4+) or ammonia gas (NH3), depending on the pH and the temperature of the solution. It is a bioavailable form of the macronutrient nitrogen and found in many fertilisers. It is also the result of the decomposition of organic nitrogen in wastewaters. At high pH, NH3 is predominant. NH3 is volatile, colourless and has a pungent odour. If it escapes to the atmosphere, it can travel large distances and resettle with the rain, what can lead to overfertilisation (eutrophication) and acidification of ecosystem.

Describes biological processes that that occur in the absence of any form of oxygen available for metabolic activity. Anaerobic processes are either hindered, or halted by the presence of oxygen.

ANAMMOX stands for Anaerobic Ammonium Oxidation. It is quite a new process, which combines ammonia and nitrite into dinitrogen gas directly instead of passing through a two stage process of aerobic nitrification and anaerobic denitrification. Compared to conventional nitrification/denitrification in activated sludge systems, ANAMMOX eliminates the necessity of an organic carbon source for nitrification, reduces energy demand for aeration and has a smaller production of excess sludge and lower CO2 emissions.

An anaerobic baffled reactor (ABR) is an improved Septic Tank with a series of baffles under which the wastewater is forced to flow. The increased contact time with the active biomass (sludge) results in increased retention and anaerobic degradation of suspended and dissolved organic pollutants. ABRs are robust and can treat a wide range of wastewater, but both remaining sludge and effluents still need further treatment in order to be reused or discharged properly.

A biogas reactor or anaerobic digester is an anaerobic treatment technology that uses organic material (e.g. wastewater, kitchen wastes, etc.) and produces (a) a digested slurry (digestate) that can be used as a fertilizer and (b) biogas that can be used for energy.

Anaerobic biogas settlers are air-tight reactors used for the pre-settlement of municipal wastewaters and the conversion of the settled sludge into biogas via anaerobic digestion. Biogas is recovered and can be transformed into heat, light or any other energy. The reactors are round or square - much like a septic tank, but with biogas collection. As the wastewater flows into the tank, organic solids start to settle to the ground. The liquid phase continuous to further treatment steps after a relatively short hydraulic retention time, while the sludge is kept in the tank for several months to years (long sludge retention time). The remaining slurry is almost pathogen free and can be used as soil amendment (optionally after an aerobic composting post-treatment or drying/humification in a sludge drying bed). Biogas settlers are most often used at community or institutional level as first treatment step of a decentralized wastewater treatment systems (DEWATS) for the pre-treatment of biodegradable domestic or industrial wastewaters.

The degradation and stabilization of organic compounds by microorganisms in the absence of oxygen, leading to production of biogas.

An anaerobic filter is a fixed-bed biological reactor with one or more filtration chambers in series. As wastewater flows through the filter, particles are trapped and organic matter is degraded by the active biomass that is attached to the surface of the filter material. Anaerobic filters are similar to septic tank, with the difference, that wastewater, once entered into the tank must flow downwards (anaerobic downflow filter) or upwards through a filter media (anaerobic upflow filter). Anaerobic filters are used as secondary treatment in household-level or decentralised wastewater treatment systems. As for any anaerobic digestion process, biogas can be recovered and transformed to energy or light.

A lagoon that forms the first treatment stage in waste stabilization ponds. It is a rather deep pond (3 to 5 m) with small surface area. As wastewater flows in, suspended solids settle to the ground and degraded by anaerobic microorganism. As for any anaerobic digestion process, biogas can be recovered and transformed to energy or light.

Anaerobic Wastewater Treatment processes are based on the treatment of waste and wastewater by a process called anaerobic digestion. During anaerobic digestion, the organic matter in the waste and wastewaters is transformed to biogas, a mix of methane (CH4) and carbon dioxide (CO2) and a nutrient rich sludge. Biogas can be transformed into heat or power and has therefore a large potential as a renewable energy source. The nutrient-rich sludge can be composted and used as fertilising soil amendment in agriculture. Typical biogas sanitation technologies are biogas settlers, upflow anaerobic sludge blanket (UASB) reactors, anaerobic baffled reactors (ABRs) and anaerobic filters for municipal wastewaters; and biogas reactors (batch, fed-batch PFR or CSTR) for the treatment of slurries and solid organic wastes from agriculture and industry.

Anal Cleansing Water is water used to cleanse oneself after defecating and/or urinating; it is generated by those who use water, rather than dry material, for anal cleansing. The volume of water used per cleaning typically ranges from 0.5 L to 3 L.

The causative organism, which was responsible for the Anammox reaction was named Candidatus Brocadia anammoxidans. This organism is a member of the planctomycetes and therefore lacks peptidoglycan in its cell wall, divides by budding, and has a compartmentalised cytoplasm. Candidatus Brocadia anammoxidans is able to anaerobically oxidise ammonium and nitrite to nitrogen gas. The key enzyme involved in this reaction, hydroxylamine oxidoreductase, is located in an organelle-like structure called an anammoxosome. The ability to oxidise ammonium anaerobically makes Candidatus Brocadia anammoxidans potentially useful for reducing, or eliminating, ammonium from wastewater.

Anoxic describes processes, which occur in the absence of molecular gaseous oxygen, but other forms of oxygen are still present (in opposite to anaerobic, which means that there is no oxygen at all) and used for the respiration of microorganism. Anoxic conditions are often found at the interface between aerobic and anaerobic environments (e.g. in trickling filters or in facultative ponds).The biological conversion of nitrate is to nitrogen gas is anoxic. This process is also known as denitrification.

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.

Depending on the treatment type and quality, digested or stabilized sludge can be applied to public or private lands for landscaping or agriculture.

To protect the immediate surroundings of a well, a concrete slab is installed around the water extraction point.

The aqua privy is a simplified variation of the septic tank. It is a simple storage and settling tank immediately under the latrine floor. Excreta drop directly into the tank through a pipe. Te bottom of the pipe is submerged in the liquid in the tank, forming a water seal to prevent escape of flies, mosquitoes and smell. Effluent usually infiltrates into the ground through a soak pit. Accumulated solids (sludge) must be removed frequently and enough water must be added to compensate for evaporation and leakage losses (in order to maintain the water seal).

Aquaculture refers to the controlled cultivation of aquatic plants and animals such as fish, crustaceans and aquatic plants. Aquaculture can be part of an integrated sanitation system making use of nutrients and heat from pre-treated wastewater.

Aquaponics is the symbiotic cultivation of plants and aquatic animals in a recirculating environment. Aquaponic comes from the two words aquaculture and hydroponic. The main aim of such systems is the recycling of the nutrients contained in the water from aquatic animal effluent. The system contain of to interlinked compartement, one for growing plants and one for growing aquatic animals. The plants take up the nutrients, allowing them to grow and reducing or eliminating the water's toxicity for the aquatic animal. Thus the water can be recirculated back to the animal pond where it will be charged again by nutrients.

An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, or silt) from which groundwater can usefully be extracted using a water well.

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.

Oslo, Norway. www.amap.no

Arid climate is characterised by high evaporation and low precipitation. This climate is typical for desert or semi-desert as well as big continental areas surrounded by mountains.

Pentavalent Arsenic

Trivalent Arsenic

Artesian springs occur when water is trapped between impervious layers and is forced to the surface under pressure. At these springs, the water comes out of the ground vertically.

Artificial fertilisers are plant nutrients produced through chemical processes to nurture soil and foster plant growth. Artificial fertilisers mainly consist of plant macronutrients such as Nitrogen, Potassium, Phosphorus and Sulphur, but lack other essential substances (micronutrients). Artificial fertiliser are able to improve the chemical properties of soils, but as they contain no organic substances, they are not able to counter the loss of organic substance through harvesting, which is important for soil structure. On the other hand, organic fertilisers produced out of biodegradable waste – such as e.g. kitchen residues, manure and other organic waste – are complete fertilisers that are able to improve both physical and chemical properties of the soil, and that are normally more balanced in their composition, containing macro- and micronutrients.

Artificial recharge is the planned, man-made increase of groundwater levels. By improving its natural replenishment capacities and percolation from surface waters into aquifers, the amount of groundwater available for abstraction is increased. Treated effluent and/or stormwater is discharged into aquifers either directly or after pre-treatment (e.g. wastewater stabilisation ponds or constructed wetlands). This is particularly useful in areas where water and groundwater resources are heavily utilised and acute problems with dropping watersheds, soil salinisation, saltwater intrusion in coastal areas or water scarcity in general exist.

An automated irrigation system refers to the operation of the system with no or just a minimum of manual intervention. Almost every irrigation system can be automated with the help of timers, sensors, computers, or mechanical appliances.

This is an intermittent gravity-flow irrigation system consisting of a storage tank equipped with one or more siphons. The water in the tank flows to the field because of the siphon effect. As soon as the tank is empty, the flow stops. For the next irrigation process, the tank has to be filled-up to restart the siphon effect again. To learn more about possible siphon designs see VORTECH (2009).

With Awareness Raising Tools, you try to influence social norms, attitudes and values of people so they will change their behaviour because they are convinced that they are doing the right thing and their actions are in line with their personal values. Different types of information, education and communication (IEC) instruments can be used to initiate behavioural change and to stimulate social pressure towards sound and sustainable policies.

Awareness raising includes an array of different technologies to make people aware of a problem, a new approach, a solution etc.