Wastewater in the context of "Blackwater (waste)"

Reuse of human excreta is the safe, beneficial use of treated human excreta after applying suitable treatment steps and risk management approaches that are customized for the intended reuse application. Beneficial uses of the treated excreta may focus on using the plant-available nutrients (mainly nitrogen, phosphorus and potassium) that are contained in the treated excreta. They may also make use of the organic matter and energy contained in the excreta. To a lesser extent, reuse of the excreta's water content might also take place, although this is better known as water reclamation from municipal wastewater. The intended reuse applications for the nutrient content may include: soil conditioner or fertilizer in agriculture or horticultural activities. Other reuse applications, which focus more on the organic matter content of the excreta, include use as a fuel source or as an energy source in the form of biogas.

There is a large and growing number of treatment options to make excreta safe and manageable for the intended reuse option. Options include urine diversion and dehydration of feces (urine-diverting dry toilets), composting (composting toilets or external composting processes), sewage sludge treatment technologies and a range of fecal sludge treatment processes. They all achieve various degrees of pathogen removal and reduction in water content for easier handling. Pathogens of concern are enteric bacteria, virus, protozoa, and helminth eggs in feces. As the helminth eggs are the pathogens that are the most difficult to destroy with treatment processes, they are commonly used as an indicator organism in reuse schemes. Other health risks and environmental pollution aspects that need to be considered include spreading micropollutants, pharmaceutical residues and nitrate in the environment which could cause groundwater pollution and thus potentially affect drinking water quality.

Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from residences and from commercial, institutional and public facilities that exist in the locality. Sub-types of sewage are greywater (from sinks, bathtubs, showers, dishwashers, and clothes washers) and blackwater (the water used to flush toilets, combined with the human waste that it flushes away). Sewage also contains soaps and detergents. Food waste may be present from dishwashing, and food quantities may be increased where garbage disposal units are used. In regions where toilet paper is used rather than bidets, that paper is also added to the sewage. Sewage contains macro-pollutants and micro-pollutants, and may also incorporate some municipal solid waste and pollutants from industrial wastewater.

Sewage usually travels from a building's plumbing either into a sewer, which will carry it elsewhere, or into an onsite sewage facility. Collection of sewage from several households together usually takes places in either sanitary sewers or combined sewers. The former is designed to exclude stormwater flows whereas the latter is designed to also take stormwater. The production of sewage generally corresponds to the water consumption. A range of factors influence water consumption and hence the sewage flowrates per person. These include: Water availability (the opposite of water scarcity), water supply options, climate (warmer climates may lead to greater water consumption), community size, economic level of the community, level of industrialization, metering of household consumption, water cost and water pressure.

Sustainable sanitation is a sanitation system designed to meet certain criteria and to work well over the long-term. Sustainable sanitation systems consider the entire "sanitation value chain", from the experience of the user, excreta and wastewater collection methods, transportation or conveyance of waste, treatment, and reuse or disposal. The Sustainable Sanitation Alliance (SuSanA) includes five features (or criteria) in its definition of "sustainable sanitation": Systems need to be economically and socially acceptable, technically and institutionally appropriate and protect the environment and natural resources.

The purpose of sustainable sanitation is the same as sanitation in general: to protect human health. However, "sustainable sanitation" attends to all processes of the system: This includes methods of collecting, transporting, treating and the disposal (or reuse) of waste.

The water industry provides drinking water and wastewater services (including sewage treatment) to residential, commercial, and industrial sectors of the economy. Typically public utilities operate water supply networks. The water industry does not include manufacturers and suppliers of bottled water, which is part of the beverage production and belongs to the food sector.

The water industry includes water engineering, operations, water and wastewater plant construction, equipment supply and specialist water treatment chemicals, among others.

Waste are unwanted or unusable materials. Waste is any substance discarded after primary use, or is worthless, defective and of no use. A by-product, by contrast is a joint product of relatively minor economic value. A waste product may become a by-product, joint product or resource through an invention that raises a waste product's value above zero.

Examples include municipal solid waste (household trash/refuse), hazardous waste, wastewater (such as sewage, which contains bodily wastes (feces and urine) and surface runoff), radioactive waste, and others.

Suspended solids refers to small solid particles which remain in suspension in water as a colloid or due to motion of the water. Suspended solids can be removed by sedimentation if their size or density is comparatively large, or by filtration. It is used as one indicator of water quality and of the strength of sewage, or wastewater in general. It is an important design parameter for sewage treatment processes.

It is sometimes abbreviated SS, but is not to be confused with settleable solids, also abbreviated SS, which contribute to the blocking of sewer pipes.

Water resources are natural resources of water that are potentially useful for humans, for example as a source of drinking water supply or irrigation water. These resources can be either freshwater from natural sources, or water produced artificially from other sources, such as from reclaimed water (wastewater) or desalinated water (seawater). 97% of the water on Earth is salt water and only three percent is fresh water; slightly over two-thirds of this is frozen in glaciers and polar ice caps. The remaining unfrozen freshwater is found mainly as groundwater, with only a small fraction present above ground or in the air. Natural sources of fresh water include frozen water, groundwater, surface water, and under river flow. People use water resources for agricultural, household, and industrial activities.

Water resources are under threat from multiple issues. There is water scarcity, water pollution, water conflict and climate change. Fresh water is in principle a renewable resource. However, the world's supply of groundwater is steadily decreasing. Groundwater depletion (or overdrafting) is occurring for example in Asia, South America and North America.

Desalination is a process that removes mineral components from saline water. More generally, desalination is the removal of salts and minerals from a substance. One example is soil desalination. This is important for agriculture. It is possible to desalinate saltwater, especially sea water, to produce water for human consumption or irrigation, producing brine as a by-product. Many seagoing ships and submarines use desalination. Modern interest in desalination mostly focuses on cost-effective provision of fresh water for human use. Along with recycled wastewater, it is one of the few water resources independent of rainfall. As stress on the need for freshwater intensifies globally, desalination has become a key part of strategies for global water security. According to a 2019 review in Science of the Total Environment, around 95 million cubic meters per day of desalinated water is produced worldwide, and the demand for desalinated water is expected to grow significantly to help close the global water supply gap.

Due to its energy consumption, desalinating sea water is generally more costly than fresh water from surface water or groundwater, water recycling and water conservation; however, these alternatives are not always available and depletion of reserves is a critical problem worldwide. Desalination processes are using either thermal methods (in the case of distillation) or membrane-based methods (e.g. in the case of reverse osmosis).