A kind of high-pressure membrane filtration process in which particles which are in the range of 1 to 10 nanometres are removed. Such particles are for instance ions of heavy metals. To remove all soluble particles, one would need an even finer process (i.e. reverse osmosis).

National Action Plan on Climate Change

National Advisory Group on Urban Sanitation

The National Urban Sanitation Policy was launched in 2008 by the Ministry of Urban Development of India, emphasing the need of defining integrated city-wide sanitation plans including institutional strengthening, awareness generation, behavioural changes, pro-poor approaches and cost effective technologies aiming at developing state sanitation strategies and city sanitation plans, that should lead to open defecation free cities, as well as sanitary and safe disposal of all human and liquid wastes.

National Water Supply and Sanitation Council

Natural coagulants are coagulants derived from plants and other locally available materials from the surrounding nature. Typical natural coagulants are prickly pear cactus, moringa seeds, broad beans and fava beans, which can be used for enhanced sedimentation as a pre-treatment step of drinking water.

Natural organic matter is broken down organic matter that comes from plants and animals in the environment. Organic matter is a collective term, assigned to the realm of all of this broken down organic matter. Basic structures are created from cellulose, tannin, cutin, and lignin, along with other various proteins, lipids, and sugars. It is very important in the movement of nutrients in the environment and plays a role in water retention on the surface of the planet.

Microorganisms in soils, wetlands and riparian areas utilise or break down numerous chemical and biological contaminants in the water and thereby purify it.

The NARE is an easily customized initial multi-sectoral needs assessment designed for refugee emergencies.

A negative externality is a term used in economic theory. It applies, when the cost a consumer pays is smaller than the social costs of the product. The external costs are then passed on to society. A common example for a negative externality is pollution.

The Nephelometric Turbidity Unit is used in water treatment in order to describe the turbidity of a liquid and is measured with a calibrated nephelometer, an instrument for measuring the size and concentration of particles suspended in a liquid or gas by means of the ligh it scatters.

Netherlands Development Organisation

Ready source of information for decision makers and individuals involved in setting up municipal wastewater systems and concepts for management of excreta in communities (developed for West Africa). The guide, offered as CD-Rom, as a link on the internet (www.netssaftutorial.com) and in a printed version, illustrates a participatory approach to sanitation planning, dealing with the complex stakeholders concerns when deciding and implementing a sanitation system. It takes the user through a seven-step-approach, each of them with pre-selected questions and answers, case studies, links for further information and tools to facilitate the adoption of participatory sanitation planning in localities in West Africa.

New Partnership for Africa's Development

A historical term for faecal sludge.

Nitrification is an aerobic process carried out by a series of bacterial population that sequentially oxidize ammonium (NH4+) and organic nitrogen to nitrate (NO3-) with intermediate formation of nitrite (NO2-). The first step of nitrification is carried out by bacteria called nitrosomonas : 2NH4+ + 3O2 -> 2NO2- + 4H+ + 2H2O. The second step is carried out by nitrobacter bacteria: 2NO2-+O2 -> 2NO3-. The two steps can also be described in a single reaction: NH4+ + 2O2 -> NO3- + H2O + H+. Once nitrate has formed, the wastewater can undergo a denitrification process in order to reduce nitrate to nitrogen gas, that is released into the atmosphere. Since complete nitrification is a sequential reaction treatment process, systems must be designed to provide an environment suitable for the growth of both groups of nitrifying bacteria.

When ammonium salts, atmospheric nitrogen, etc. have been oxidised to nitrites and nitrates, mainly by the action of bacteria.

Nitrogen is a chemical element which can be found in fresh water and wastewater in many different forms. In wastewater for example mainly organic nitrogen which comes from the rejections of food can be found. This nitrogen is an essential nutrient and can lead to algal bloom, eutrophication and water pollution. In its reduced form (ammonium, NH4+ and ammonia NH3), it is transformed into nitrate, a process which consumes a lot of oxygen leading to oxygen depletion in the water. Nitrate (NO3-) is also a drinking water pollutant while nitrite (NO2-) is toxic to fish. Nitrite can be transformed to nitrate and nitrate can be transformed to gazeous nitrogen gas (N2) and released to the atmosphere (denitrification). Nitrogen is also an important constituent of fertilisers used for food production. Today, nitrogen used for food production is mainly mineral nitrogen which is mined consuming huge amounts of energy. By recycling nitrogen contained in wastewater, the pollution of ecosystems could be reduced and the energy consumption by nitrogen mining avoided.

When organic material is applied to the soil, the decomposing microbes multiply quickly. For growth, they need nutrients, especially nitrogen, like plants do. If the applied plant material does not contain sufficient nitrogen, the micro-organisms will take it from the soil. This process is called nitrogen immobilisation, as the nitrogen is fixed temporarily in the microbes and released only after some time. During this time, the microbes compete with the plants for nitrogen and the crop may suffer from malnutrition. Nitrogen-immobilisation can occur when the following materials are applied: straw or grain husks, material containing wood (e.g. twigs, saw dust), half rotten compost. To prevent nitrogen-immobilisation. Old or rough plant materials should be applied to the soil at least 2 months before planting or sowing the main crop.

Wastewater from industry, businesses or agriculture, that contains chemical pollution, which is toxic for microorganisms and can therefore not be treated by biological wastewater treatment units. In order to degrade the toxic chemicals, other processes such as advanced oxidation processes (AOP) need to be applied. Often, it is possible to degrade first the toxics with AOPs after which the wastewater becomes biodegradable and can be treated as municipal wastewater. This can reduce costs, as generally AOPs require more technical know-how and energy.

Non-Governmental Organization

Pre-treated greywater is applied intermittently to the surface of a filter media, percolates through an unsaturated filter zone where physical, biological and chemical processes treat the water. The treated greywater is collected in a drainage network or infiltrates the underlying soil.

Nonpoint source pollution generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage or hydrologic modification. The term "nonpoint source" refers to any source of water pollution that does not meet the legal definition of "point source".

N, P, and K are the periodic chart symbols for Nitrogen, Phosphorus and Potassium. These three elements are the primary macronutrients for plant growth and are the main elements compound fertilisers will contain. Secondary macronutrients are Calcium (Ca), Sulfur (S) and Magnesium (Mg).

Any substance that is used for growth. Nitrogen (N), phosphorus (P) and potassium (K) are the main nutrients contained in agricultural fertilisers. N and P are also primarily responsible for the eutrophication of water bodies.

The ability of the soil to supply plants with nutrients due to the amount of nutrients within, without releasing them.