Aerobic : means ‘requiring oxygen'. Aerobic processes can only function in the presence of molecular oxygen (O2), and aerobic organisms are those that use oxygen to drive cellular respiration and store energy

Anaerobic: means ‘in the absence of oxygen'. Aerobic processes are either hindered, or halted by the presence of oxygen. anaerobic processes are often more foul-smelling than aerobic processes.

Anal cleansing water is water that is collected after having been used to clean oneself after defecating (and/or urinating). It is generated by those who use water, rather than dry material for anal cleansing.

Anoxic: means ‘deficient in oxygen'. Organisms that can live in an anoxic environment can use oxygen that is bound in other molecules (e.g. nitrate, sulphate). Anoxic conditions are often found at the interface between aerobic and anaerobic environments (e.g in trickling filters or in facultative ponds).

Bacteria : bacteria are simple, single cell organisms. Bacteria obtain nutrients from their environments by excreting enzymes which dissolve complex molecules into more simple ones that can then pass through the cell membrane. Bacteria live everywhere on earth and are essential for maintaining life and performing essential ‘services' such as composting, aerobic degradation of waste, and digesting food in our stomachs; some types however can be pathogenic and cause severe illness.

BOD/ Biochemical Oxygen Demand . It is a measure of how much oxygen is consumed by microbes as they degrade organic matter. It is a proxy measure for the amount of organic material that is present in water: the more organic content, the more oxygen required to degrade it (high BOD), the less organic content, the less oxygen required to degrade it (low BOD)

Biological treatment : the use of living organisms (e.g. bacteria) to treat waste; this is contrast to chemical treatment which relies on chemicals to transform or remove contaminants from waste.

Biodegradable : can be broken down into basic molecules (e.g. carbon dioxide, water) by organic processes carried out by bacteria, fungi, and other microoganisms.

Biomass : refers to the quantity of living organisms. It is often used to describe the ‘active' part of the sludge that is responsible for degrading the organic matter.

Biogas: The common name for the mixture of gases released from anaerobic digestion. Typically biogas is comprised of methane (50-75%), carbon dioxide (25-50%) and varying quantities of nitrogen, hydrogen sulphide, water and other components.

Blackwater : the mixture of urine, faeces and flushing water along with anal cleansing water (if anal cleansing is practiced) or dry cleansing material (e.g. toilet paper) It is very high in organics and pathogens.

Brownwater : the mix of faeces and flushing water, but with NO urine.

Cesspit: An enclosed container used for storing sewage.

Chemical treatment : the treatment of wastewater using chemicals to remove pollutants from the wastewater. A common example is the use of alum for coagulation or chlorine for oxidation.

C:N ratio : carbon to nitrogen ratio. This ratio describes the relative amounts of dry available carbon to dry available nitrogen. The ideal value for microbes is around 30:1 (usually expressed as just 30)

Coagulation : the process of forming small clumps so particles so that they may be more easily settled out of wastewater.

COD : Chemical Oxygen Demand is similar to BOD but measuring the amount of oxygen consumed by a chemical oxidizing agent. COD is always equal to or higher than BOD because of the organic compounds which can only be oxidized chemically.

Combined Sewer : a sewer system that is designed to carry both blackwater from homes and stormwater (rainfall). Combined sewers must be much larger than Separate Sewers to account for the high volume.

Compost/ Humus : is the earth-like, brown/black material that is the result of decomposed organic matter; generally is has been hygienized sufficiently that it can be used safely in agriculture.

Composting : the controlled aerobic degradation of organic matter by bacteria, fungi, worms, and other organisms to create a sanitized, humus-like product. The composting process is characterized by a sharp, and persistent heat change that can raise the temperature of the compost pile up above 70 degrees C.

Concrete: A mixture of cement, sand, gravel and water that will harden into a solid, stone-like material.

Decentralization : the shift of decision making and responsibility from central authorities to the same level at which the policies are directed.

Decomposition : the transformation of dead organic material (plants, animals, etc.) into more basic compounds and elements.

Desludging: The process of removing sludge, that is, the accumulated solids and liquids, from a tank, pit, or other storage unit.

Digestion : similar to decomposition, but usually applied to the decomposition of organic materials (including bacteria) by bacteria, in sludge.

Dry Cleansing Materials: may be paper, corncobs, rocks or other dry materials that are used for anal cleansing (instead of water). Depending on the system, the dry cleansing materials may be collected and disposed of separately. For the sake of simplicity they are not shown on the system diagrams

Ecological Sanitation : is a term applied to waste treatment technologies when they not only limit the spread of disease, but protect the environment and return nutrients to the soil in a beneficial way.

Effluent : the general name for a liquid that leaves the place or process from where it originated

Environmental Sanitation: as oppossed to simply ‘sanitation', seeks to include all aspects of the physical environment which may affect human health and well-being; typical examples of an environmental sanitation program may include potable water, solid waste management, drainage, storm water management, and sanitation.

Eutrophication : the process by which a water body becomes over-enriched with nutrients, resulting in an over-abundance of life and a depletion of oxygen.

Evaporation : the process of water changing from a liquid state to a gaseous state.

Evapotranspiration : evaporation that is facilitated by vegetation. Plants emit water through their stoma (pores) thus providing a greater surface from which water can evaporate.

Excreta : is the mixture of urine and faeces that is not mixed with any flushing water

Faecal Sludge is the general term for the undigested, or partially digested slurry or solid that results from the storage or treatment of blackwater or excreta

Faeces : refers to (semi-solid) excrement without any urine or water

Floatation: The processes whereby lighter fractions of a wastewater, including fats, oils, soaps, etc., rise above the water and the solids, and can thus be separated.

Flushwater is the water that is used to move excreta, urine or faeces from the user interface into the next process technology.

Footprint: describes the surface area required by a given installation, that can not be used for any other purpose

Greywater : the total of water generated from the washing of food, clothes, and people. It does not contain excreta, but it still contains pathogens and organics.

Groundwater: Water that is naturally present beneath the surface of the ground. In some instances groundwater may be found several centimeters below the surface, or it may be up to a hundred meters below the surface. Groundwater is generally quite clean and can be used for drinking water; for this reason care must be taken not to contaminate ground water with sewage.

Health : ‘'is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.'' (WHO, 1948).

Helminth : A parasitic worm, i.e. one that lives in or on its host, causing it damage.

Humus : an earth-like dark brown or black material comprised primarily of decomposed organic material.

Hydraulic Gradient: The surface slope of a liquid in a pipe, i.e. the liquid will flow along the hydraulic gradient of the system and if there is a inflow that is lower than the gradient, water will flow upwards to meet the gradient line.

Influent : the general name for the liquid that enters into a place or process; the effluent of one process is the influent of the next.

Invert: the bottom of the inside of a pipe. The depth of the invert is especially important when designing sewers.

Leachate : the liquid fraction of a mixed waste that, through gravity or filtration, is separated from the solid component.

Microbe : general name given to a micro-organism; a microscopic bacterium.

Micropollutants : are pollutants which are present in extremely low concentrations, but whose effect is known to be significant. Pharmaceuticals and hormones are two groups of micropollutants which are causing increasing concern for their effects on the endocrine system and sexual development.

Monitoring : is the continuous collection and assessment of data (qualitative and quantitative) with the intended goal of optimizing performance and minimizing flaws.

Nightsoil: The name generally given to excrement that may be collected manually. Generally this practice is carried out where there is both no infrastructure for collection and storage and also where there is agricultural land that can receive the waste. Unprotected handling and use in agriculture should be treated with caution

Nutrient : any substance (including protein, fat, carbohydrate, vitamins, or minerals) that is used for growth. In wastewater treatment systems, ‘nutrient' usually refers to nitrogen and/or phosphorus since they are primarily responsible for eutrophication.

Operation and Maintenance all work relating to the day-to-day activities that keep a process or system functioning smoothly to prevent delays, repairs and/or downtime.

Organics : general name given to organic materials. An organic is any molecule that contains carbon. Examples of organic compounds are proteins, lipids, amino acids, vitamins, and other building blocks of life. Organics refers to the organic material that must be added to some technologies in order to make them function properly (e.g. composting chambers).

Pathogen : a micro-organism that is capable of causing disease in plants or animals (including humans).

Parasite: any organism that lives on or in another organism and damages its host

Percolation: The movement of liquid through soil with the force of gravity

pH : the measure of the acidity or alkalinity of a substance. A pH value below 7 indicates that it is acidic, a pH value above 7 indicates that it is basic (alkaline).

Retention time: The theoretic time that one unit of water (or sludge) stays in one tank or pond. When referring to units of water, the term Hydraulic retention time is often used (HRT) and is calculated by: HRT= V/Q, where V is the volume of the tank and Q is the rate at which the water leaves (e.g. m 3 /sec)

Runoff : also referred to as Surface Runoff. It is the quantity of water that falls as precipitation but does not infiltrate to the groundwater table.

Sanitation : a general term used to describe a battery of actions that all aim to reduce the spread of pathogens and maintain a healthy living environment. Specific actions related to sanitation include, wastewater treatment, solid waste management and storm water management.

Scum : General name given to the top, floating layer of material that sits above the water. It is most noticeable in septic tanks where distinct layers of scum, water, and sludge form over time.

Sedimentation : the process of allowing particles that are heavier than water to sink down, so that the clarified liquid on the top can be collected.

Septage : ‘liquid and solid material pumped from a septic tank, cesspool or other primary treatment source'. (Bellagio, 2005)

Sewage : General name given to the mixture of water and excreta (urine and faeces), although more technically it should be referred to as blackwater.

Sewer : an open channel or closed pipe used to conveying sewage

Sewerage : all the components of a system used for collecting, transporting and treating sewage (including pipes, pumps, tanks, etc.)

Sludge : the thick, viscous layer of materials that settles to the bottom of septic tanks, ponds, and other sewage systems. Sludge is comprised mostly of organics, but also sand, grit, metals, and various chemical compounds.

Stabilized : the term used to describe the state of organic material that has been completely oxidized and sterilized. When most of the organic mater has been degraded, bacteria begin to starve and consume their own cytoplasm. The organic matter left by the dead bacteria is then degraded by other organisms, which results in a fully stabilized product.

Stakeholder : any group, person, or agency that has an interest in or is affected by a policy, plan, or project.

Stormwater is the general term for the rainfall that runs off of roofs, roads and other surfaces before flowing towards low-lying land. It is the portion of rainfall that does not infiltrate into the soil

Sullage: Old word for greywater: includes wastewater from cooking, washing, and bathing, but does not include any excreta.

Superstructure : Name given to the structure that provides privacy to a person using a toilet/bathing facility. A superstructure may be permanent and made of concrete or bricks, or mobile and made of bamboo or cloth.

Surface water: Term to describe rainwater that runs overland (i.e. does not infiltrate the ground). Surface water, unlike ground water is not safe for consumption generally as it accumulates pathogens, metals, nutrients and chemicals as it flows across contaminated surfaces.

Sustainability : meets the needs of the present without compromising the ability of future generations to meet their own needs (Brundtland Commission)

Sustainable Sanitation: The main objective of a sanitation system is to protect and promote human health by providing a clean environment and breaking the cycle of disease. In order to be sustainable a sanitation system has to be not only economically viable, socially acceptable, and technically and institutionally appropriate, it should also protect the environment and the natural resources (SuSanA)

Urea : the organic molecule (NH 2 ) 2 CO that is excreted in urine as a way of ridding the body of excess nitrogen. With time, the urea in urine breaks down into carbon dioxide and ammonia, which is readily used by organisms in soil.

Urine is the liquid waste produced by the body to rid itself of urea and other waste products

Vector : the organism that transmits a disease to the host (the vector itself may be a host, but is not the ‘true host'). Flies are vectors as they can transmit pathogens from faeces to humans.

Ventilation : the movement of air; air is both supplied to, and removed from a space.

WC: Derived from the words ‘Water Closet'. It is an ambiguous term that can either refer to the actual room where a toilet is located, or the actual toilet itself.

Washer: is the general name for those who use water to cleanse after defecating

Wastewater : traditionally described as any water that has been used and is unfit for further use. The term is applied broadly to all waters originating in toilets, showers, sinks, washing areas, factories, etc. More recently terms such as ‘blackwater', ‘greywater' and ‘yellow water' have been adopted both as a way to describe the composition more accurately, and to emphasize the fact that used waters have nutrients, are valuable, and should not be ‘wasted'.

Water table: the top level of the groundwater; also referred to as the groundwater table. A water table is not static and can vary with season, year, and usage.

Wiper : is the general name for those who use solid materials, like paper, to cleanse after defecating.