Every ninth inhabitant of the planet does not have access to clean water near their home. And the situation is constantly getting worse. According to UN estimates, 9.8 billion people will live on Earth by 2050. Climate change, as well as the development of agriculture and industry to meet the needs of an ever-growing population, will lead to a serious reduction in available water resources.
According to the WaterAid research project, 60% of the world's population already lives in areas where water supply cannot or will soon cease to meet demand. The water crisis is most painfully manifested in the Middle East, Central Asia and North Africa.
Both developed and developing countries face one common problem — the growth of industrial and urban wastewater. This, in turn, encourages developers from different countries to search for new and increasingly advanced water purification technologies.
Traditional cleaning methods include the use of adsorbents, reverse osmosis, ion exchange and electrostatic precipitation. Their disadvantages are high cost, poor reusability and low efficiency. Despite the progress made in the development of new technologies over the past decade, their use is limited mainly due to the properties of materials and cost.
In 2020, the volume of the global market for water purification technologies was estimated at $50.5 billion. Until 2026, the market will grow by about 7% annually due to rapidly declining freshwater resources worldwide.
Let's list five of the most innovative, in our opinion, water purification technologies.
1. Membrane separation
This is a long-standing and popular method of water purification from impurities and pollutants. There are many technologies that work like a filter: they pass water through a film with microscopic holes. The water passes through, and the polluting particles get stuck on the membrane.
Methods of modern membrane separation, such as reverse osmosis (removes particles even with a size of 0.001-0.0001 microns — hardness salts, sulfates, nitrates, sodium ions, dyes, etc.), can purify water from 99.5% of impurities. But for this, the pore size must be less than a micron. The main disadvantage of the technology is the high cost of maintenance (membranes are often clogged).
2. Irradiation
As the name suggests, this process is based on the exposure of radiation to wastewater to destroy organic pollutants. Radiation sources range from gamma rays to ultraviolet light.
Irradiation is usually used for disinfection, but some methods, for example, ionizing irradiation, combined with the addition of ozone or hydrogen peroxide, improve the efficiency of decomposition of organic impurities, including pesticides and phenols.
Modern UV treatment systems offer the use of LED lamps. Now such lamps are beginning to be actively introduced in the utility sector, and are also used by NASA in the agency's space developments.
3. Purification by nanoparticles
People have been using substances such as charcoal for a long time to purify water by adsorption. When cleaning with nanoparticles, the same mechanics is used, but with nanoscale particles. Various types of nanomaterials — metal nanoparticles, nanosorbents, bioactive nanoparticles, nanofiltration (NF) membranes, carbon nanotubes (CNTs), zeolites and clay — have proven to be effective materials for wastewater treatment. Their use eliminates pesticides and heavy metals in the water. Carbon nanotubes are also considered as a breakthrough technology for desalination of seawater to the drinking stage. The main disadvantage of the technology is the cost.
4. Bioaugmentation
The organic method of purification is the addition of a mixture of microorganisms to the water, which destroys and removes impurities. These microorganisms include enzymes and safe bacteria that naturally decompose pollutants such as oils or carbon products. But bioaugmentation can affect the ecosystem of microflora and, as a result, disrupt the purification process. Therefore, this technology cannot yet be used to obtain drinking water.
5. Membrane bioaugmentation
Membrane Bioreactors (MBR) are a hybrid technology that includes membrane separation and bioaugmentation. Wastewater after biological treatment with activated sludge is fed into a container called a bioreactor. In this container there are membranes that divide wastewater into two streams — active sludge, reused for biological purification, and clean water.
There are two main types of MBR on the market — vacuum (or gravity) flow systems and pressurized systems. Vacuum systems are immersed in water and have membranes installed either inside bioreactors or in a subsequent tank. The second type of MBR, where the flow is controlled by pressure, is an in-tube cartridge system located outside the bioreactor.
The advantage of membrane bioaugmentation is a small area for biological purification. MBR reactors increase the capacity of treatment facilities without increasing the area of structures.
The reuse of wastewater for irrigation and other non-drinking purposes has become commonplace and has existed for decades. For example, in Israel, almost 90% of the country's wastewater is reused in agriculture.
A reliable technological scheme, which includes at least five stages, is necessary for the post-treatment of wastewater to the drinking state. Australia, Singapore, Namibia, South Africa, Kuwait, Belgium, the United Kingdom and the United States (the states of California and Texas) reuse treated wastewater of drinking quality. In these countries, underground or surface water sources (dams) are replenished with purified water.
River water used in various cities for the production of drinking water contains large volumes of wastewater. Recycled water is safe to drink, but some people can't overcome the feeling of disgust. Periodically, actions to overcome psychological barriers are held all over the world. So, Microsoft founder Bill Gates drank a glass of liquid that was processed from human fecal matter into drinking water using the Omniprocessor technology of the Bill and Melinda Gates Foundation. And the French company Veolia has launched a joint project in the Czech Republic with the Čížová brewery, which brewed beer from recycled drains.
