Glossary

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Vacutug
The vacutug consists of a 0.5 m³ steel vacuum tank connected to vacuum pump, which is connected to a gasoline engine. On level ground, the vehicle is capable of around 5 km/h. The waste sludge can be discharged under gravity or by slight pressurisation from the pump. Synonyms: Mini-tug
Vacuum
A vacuum describes a space or container entirely devoid of air resulting in an under-pressure and an airflow towards the vacuum space.

Vacuum On Demand
A vacuum system where the system's pump generates vacuum in the piping only when a toilet is flushed or a greywater tank is discharged. Used in small systems with 4 to 10 toilets. Synonyms: VOD
Vacuum Sewers
Vacuum sewerage systems consist of a vacuum station, where the vacuum is generated; the vacuum pipeline system; collection chambers with collection sumps; and interface valve units. In contrast to conventional gravity sewerage systems with intermediate pumping stations, the pressure within the vacuum system is maintained below atmospheric pressure. Following the suction crated by the valve, batches of wastewater are forced to flow from the collection chambers towards the vacuum station. The valves are operated pneumatically and no electricity is needed. Vacuum sewerage is particularly advantageous where water is scarce; the natural slope is insufficient for gravity flow; in areas with poor subsoil conditions (e.g. rocky soil, high groundwater table); where operation is seasonal or water flow strongly intermittent; or in areas prone to flooding.
Vacuum Truck
A truck equipped with a pump and a storage tank. The pump is connected to a hose, which is lowered down into a septic tank or pit, and the sludge is pumped up into the tank. Generally, the storage capacity of a vacuum truck ranges between 4 and 6 m³.

Vault Composting Toilet
Composting toilet using an above vault as a composting chamber (e.g. continuous composting, concrete or brick double-vaults or movable containers).

Vector
The organism that transmits a disease to the host (the vector itself may be a host, but is not the ‘true host’) is a vector. Flies are vectors as they can transmit pathogens from faeces to humans.
Ventilated Improved Pit Latrine
A ventilated improved pit latrine (VIP) is similar to a single pit latrine, with addition of a vertical vent pipe made out of PVC, bricks, PET bottles etc. Wind blowing across the top of the vent pipe sucks air out of the pit while fresh air flows into the pit through the squat hole. Due to this airflow, odour and flies in the latrine superstructure are reduced. The flow of air can be increased when the pipe is painted black: the air in the vent heats up, rises, and creates and updraft which helps to pull air, moisture and smells out of the pit. The top of the pipe should be covered with a mesh to stop flies from entering or leaving the pit through the vent. The VIP design can be used for both single and double pits. Single pits need to be emptied or relocated when full. When double pits are used, one side is used at a time until it is full and then the second side is used. In this way, no new pits need to be constructed. Dry anal cleansing is advantageous to minimise water content. VIPs, like single pit latrines, are among the simplest and cheapest toilet system, although no treatment is included. Even though odour and fly nuisances are reduced through the aeration in VIPs, the risk of groundwater contamination due to infiltration remains high, particularly in densely populated areas.
Abbreviation: VIP
References:
Informed Choice Catalogue
Ventilation
The provision of fresh air to a room, building etc.

Vermicomposting
Vermicomposting is the process of using earthworms to break down organic waste in order to create a faster than normal composting. The worm population is self regulating and will increase to the point where available food and space constrain further expansion. The process must be monitored for such parameters as moisture content and temperature but is not labor-intensive. Compared to ordinary soils, the earthworm castings (the material produced from the digestive tracts of worms) contain much more nitrogen (N), phosphorus (P) and potassium (K). They are rich in humic acids and improve the structure of the soill if used as a soil conditioner. The worms are placed in bedding made of loose materials such as coconut husk or shredded paper in a shallow box or tub and fed with soft organic matter such as kitchen waste. After about two months the compost can be harvested by putting the compost in the shape of a cone and scrapping of the top layers. The worms go to the bottom of the cone as they run away from light. Vermicomposting is a popular sustainable low-cost treatment for organic solid wastes (kitchen wastes, plant wastes). It is also applied to treat fecal matter, such as human excreta in the form of sewage sludge, sieved blackwater or faeces. Vermicomposting is also used to produce Terra Preta. Synonyms: Vermicompost, Worm Compost
Vertical Flow Constructed Wetland
In vertical constructed wetlands (CW), wastewater is fed from the top and then gradually percolates down through the sand/gravel bed and is collected by a drainage network at the base. Sub-surface CWs have the advantage of better oxygen transmission and less problems due to mosquito or fly breeding compared to surface flow CWs. Synonyms: Sub-surface Flow Constructed Wetland, Sub-surface Vertical Flow Constructed Wetland, VF
Abbreviation: VF

Vertical Garden
The term vertical garden refers to any kind of construction and support structure for growing plants in an upwards-directed, vertical way and thereby efficiently and productively making use of the existing space for food or other kind of plant production. A huge variety of different designs and concepts are available including greywater towers, green walls or living walls. The reuse of different composts (e.g. compost, vermicompost or terra preta) from household wastes and reclaimed water (e.g. greywater) or urine can be considered in vertical gardening allowing to enhance food production and to close the nutrient and water cycle at a local level. Synonyms: Green Wall, Living Wall

Vision
A vision is a desired future state.

VLOM pumps
A VLOM pump can be operated and sustained using Village Level Operation and Maintenance. The term VLOMM is also used, meaning Village Level Operation and Management of Maintenance. One of the basic aims of a VLOM hand pump is to make all the main wearing parts easy to reach and replace, and to reduce the wear and tear on the pump by good design.
References:
VLOM Pumps
Volatile Fatty Acid
Volatile fatty acids are fatty acids with a carbon chain of six carbons or fewer. They can be created through fermentation in the intestine. Synonyms: VFA
Abbreviation: VFA
References:
http://en.wikipedia.org
Volumetric Organic Load
The volumetric organic load is used to design wastewater treatment units. It can be calculated by multiplying the BOD (mg/L) of the raw water by the influent flow Q (m3/day) and then dividing this volumetric load by the pond volume. Synonyms: gBOD/m3/day
Abbreviation: gBOD/m3/day

Vyredox
The Vyredox method for water purification was developed in Finland and is now also used in Sweden and some other countries. It oxidises the ferrous ion, which is soluble in water, to the ferric ion, which is insoluble, before the water enters the well.