Objective Tree
An objective tree starts with the over-arching objective. This is put in a box at the top of a page. The branches going down from this are those things you wish to achieve that will lead to the main objective (subgoal). Start a new branch for each individual subgoal, and add the steps necessary to achieve this subgoals. This process is continued until you have a "tree" that covers all your separate objectives. The end product will look somewhat similar to a "family tree".
Office for Coordination of Humanitarian Affairs
OCHA is the part of the United Nations Secretariat responsible for bringing together humanitarian actors to ensure a coherent response to emergencies. OCHA also ensures there is a framework within which each actor can contribute to the overall response effort Sinónimos: OCHA
Abbreviation: OCHA
Offsite Sanitation
A sanitation system in which excreta and wastewater are collected and conveyed away from the plot where they are generated. An off-site sanitation system relies on a sewer technology (e.g. simplified sewer, solids free sewer or conventional sewer) for conveyance.
On-site Storage and Treatments
Human excreta and wastes, if not directly transported to a centralised sewer system, need to be collected in order to prevent odour, fly breeding and health risk from pathogens. Sometimes, such collection facilities also include directly a treatment or pre-treatment of the collected products.

On-site Wastewater Treatment
On-site wastewater treatment is used to treat wastewater from one or several households or institutions and business and to return treated wastewater back into the immediate environment. Such systems are based on the principle of low organisation and maintenance. The main advantage is the lower costs, because the systems do not require large collection networks and generally work without technical energy and are constructed with locally available materials. Sinónimos: Decentralised Wastewater Treatment

Onsite Sanitation
A sanitation system in which excreta and wastewater are collected, stored and/or treated on the plot where they are generated. There are two main categories of on-site sanitation technologies: ‘wet’ which require water for flushing; and ‘dry’ which do not require any water for flushing. Sinónimos: On-site Sanitation
Open Comparative Consequence Analysis
Open Comparative Consequence Analysis Sinónimos: OCCA
Abbreviation: OCCA

Open Defecation Field
Excreta disposal system for ex-situ (camp) situations with the presence of a large number of people. It is only recommended as an extreme short-term solution and when enough space is available. In practice, this method does not seem to be very widely implemented. The system should also include hand-washing facilities, supervision, and excreta should be covered with soil as soon as possible.
Open Defecation Free
An area is declared as open defecation free if people stop to defecate in the open for good. Open defecation is still a big problem worldwide, and it is estimated that 1.2 billion people practise open defecation, leading to the occurrence of many diseases.
Abbreviation: ODF

Open Planning of Sanitation Systems
The objective of the Open Planning of Sanitation Systems approach is to provide a practical guideline for the planning and implementation of sanitation projects based on sanitation system function requirements rather than technologies. This shall improve the sustainability of sanitation systems. Sanitation systems can be regarded as sustainable if they protect and promote human health, do not contribute to environmental degradation or depletion of the resource base, and are technically and institutionally appropriate, economically viable and socially acceptable – furthermore, they have to remain functional over time. The OPSS planning process itself is performed in five steps that are briefly explained. The planning and implementation tool is based on the Open Comparative Consequence Analysis methodology that has been developed in Sweden by WRS Uppsala AB. The approach itself was established by EcoSanRes. Sinónimos: OPSS
Abbreviation: OPSS

Operation and Maintenance
Routine or periodic tasks required to keep a process or system functioning according to performance requirements and to prevent delays, repairs or downtime. Sinónimos: O&M
Operation and Maintenance of Water Distribution
Operation and maintenance of large water distribution systems is essential for the sustainable water supply regarding financial and health aspects. Main tools for operation and maintenance include leakage control, prevention of recontamination and continuous supply (opposed to intermittent supply). The system can be optimised energetically, or operation and maintenance can be significantly lowered by decentralisation.

Optimisation of Water Use at Home
Extracting more water than the natural system is able to regenerate, will lowering the water table and can cause dramatic effects on water quality, future water supplies and agriculture. With clever water saving methods in your home (e.g. water saving taps and showerheads, greywater reuse, etc.) you and, your community can contribute to use less water and benefice the environment.

Optimisation of Water Use in Agriculture
Water scarcity, together with the increasing global demand for water in many sectors, including agriculture, has turned out to be a global concern. A growing world population and the adverse impacts of climate change lead to an increasing competition for water use by industrial and domestic uses and agriculture for food production. Various irrigation and moisture control techniques have been adopted to improve water use efficiency for crop production, reduce the damage caused by drought and the water use for agriculture.

Optimisation of Water Use in Industry
Annual water volume use by industry is growing at an enormous rate. There is an urgent need to find ways of saving, reusing and recycling water, and to develop methodologies to improve water resource management in Industries. There are various ways in which industry can use water more efficiently. Pachinery, industrial processes and related support services require large quantities of water, which can be reduced; Process water can be recycled and reused; Leaks can be identified and fixed; One can install water efficient equipment and the industrial wastewater might be reused for other activities such us aquaculture.

Organics are any compounds that contain carbon (other than simple binary compounds and salts). Examples of organic compounds are proteins, lipids, amino acids, vitamins, and other building blocks of life. Sinónimos: Organic Compound, Organic Material
Organic Matter
Mostly rotten plant deri-vates incorporated in the soil to improve the root conditions Sinónimos: Organic sub-stances, Soil organic matter, humus
Organic Nitrogen
The term organic nitrogen is used to describe a nitrogen compound that had its origin in living material. The nitrogen in protein and urea is organic nitrogen. Organic nitrogen can enter wastewater as bodily wastes, discarded food material, or as component of cleaning agents.

Organics refers to biodegradable plant material (organic waste) that must be added to some technologies in order for them to function properly (e.g., composting chambers). Organic degradable material can include, but is not limited to, leaves, grass and market waste. Sinónimos: Organic Solid Waste, Organic Waste
Organização das Nações Unidas para Alimentação e a Agricultura
A FAO é uma organização das Nações Unidas cujo objetivo é aumentar a capacidade da comunidade internacional para de forma eficaz e coordenada, promover o suporte adequado e sustentável para a Segurança Alimentar e Nutrição global. Para isso, realiza programas de melhoria da eficiência na produção, elaboração, comercialização e distribuição de alimentos e produtos agropecuários, além de projetos que contribuam para a redução da pobreza rural e o crescimento económico global. Sinónimos: FAO
Abbreviation: FAO
Other Water Sources
Other water sources in SSWM refer to tools that are not considering the exploitation of surface, rain or groundwater (e.g. bottled water, water source protection) or the usage of reclaimed water sources. The usage of reclaimed water will be discussed in the use and reuse sections.

Overhung Latrine
An overhung latrine consists of a superstructure and floor built over water. A squat hole in the floor allows excreta to fall directly, or via a chute into the water below. Overhung latrines are rarely appropriate (due to the direct pollution of water) and should only be considered if other options are not possible, such as in areas prone to continued flooding. The receiving water must be sufficiently deep throughout the year, preferably should be saline to prevent human consumption, and should be flowing away from settlements.
In chemistry, oxidation describes the process of combining or becoming combined with oxygen. Oxidation can take place chemically or it can be catalysed by a microbial process (by bacteria). In wastewater treatment, oxidation means when bacteria oxidise organic loads in the wastewater in a fast single step process leading to the production of CO2 and heat. The process rate increases along with increasing temperature. Examples of application of oxidation are Trickling Filters, Rotating Biological Contactors, Aerobic Ponds, Aerated ponds, Activated sludge, etc. Sinónimos: Aerobic Digestion

Oxidation Ditch
Oxidation ditches are large round or oval ditches (channel reactors) used for the aerobic treatment of wastewater. One or more horizontal aerators guarantee oxygen supply and mix and move the prescreened content around the ditch. Operation can be continuous or intermittent. Primary sedimentation is usually not required, but secondary sedimentation tanks are generally used. Oxidation ditches are suitable for areas where land availability is high. They have the advantage that they are relatively easy to maintain (compared to activated sludge systems) and are resilient to shock loads as it often occurs in smaller communities (i.e. at breakfast time and in the evening). Sinónimos: OD
Ozonation is a water treatment process that destroys microorganisms and degrades organic pollutants through the infusion of ozone, a gas produced by subjecting oxygen molecules to high electrical voltage. Sinónimos: Ozonisation