Access to clean safe water is of utmost importance for human health and society at large. Drinking water scarcity is one of the most problematic crises facing the world today; despite water being one of the most abundant resources globally, less than 1% is considered clean water available for human consumption. Climate change, population growth, aging infrastructure, and urbanization are increasingly important variabilities in water supply. Water users must rely on new safe water sources, and cleantech innovators are being sought to deploy previously untried treatment technologies.
Due to the high risk of exposure to various contaminants in drinking water, point-of-use (POU) drinking water treatment is rapidly expanding. One of the major growth contributors to the POU treatment systems market is the increasing human population, which is expected to rise to 8.6 billion in 2030. This exponential growth will surely trigger a greater demand for POU as clean water becomes scarcer.
POU treatment technologies now include various combinations of string-wound sediment filters, activated carbon, modified carbon, ion exchange and redox media filters, reverse osmosis membranes, ultraviolet lamps, nanotechnology-based solutions, UV and UF treatment combinations, and organic and biodegradable filtering solutions.
Many of these technologies are well proven, highly commoditized, and cost effective. Advanced oxidation processes, which are chemical oxidation processes that use powerful transitory species such as hydroxyl radicals and sulphate radicals, are also of interest, as they can be generated from water using solar energy, electrical energy, sound energy, and other sources.
Ensuring Microbial Safe Water
Early in the 21st century, the World Health Organization stated, “Water entering the distribution system must be microbiologically safe and ideally should also be biologically stable.” Biological stability of drinking water refers to the concept of providing consumers with drinking water of same microbial quality at the tap as produced at a water treatment facility. However, uncontrolled growth of bacteria can occur during distribution in water mains and premise plumbing and can lead to problems:
- Hygienic: development of opportunistic pathogens
- Aesthetic: deterioration of taste, odor, color
- Operational: fouling or biocorrosion of pipes
How do safe water experts steer the microbial community of water to a state that is resistant toward invasion and/or growth of unwanted microorganisms and does not show excessive regrowth during distribution? To become biostable, drinking water should contain a relatively high amount of bacteria compared to the amount of growth-limiting factors available. Both the source water quality and the water treatment are crucial for the production of biostable drinking water. Two main conditions should be fulfilled for obtaining biostable water.
- The total nutrient and energy availability should be below the threshold concentration to select for K-strategists and not induce regrowth that can lead to water quality deterioration, and in extreme cases pose health risks — regrowth of pathogens.
- The total bacterial load should be close to the carrying capacity.
One interesting approach to remove nutrients and microorganisms to ultra-low levels at the end of the treatment train is reverse osmosis (RO). RO is an emerging technology that physically retains bacteria and nutrients by pushing the water molecules over a membrane under high pressure.
Biofiltration — activated carbon filtration — is often applied after physicochemical treatment to avoid regrowth in the distribution network and to remove trace pollutants. This treatment step is crucial for obtaining biostable drinking water, as nutrients will be removed by a combination of adsorption and controlled microbial growth on the filter.
Utilizing the Venturi Effect for Safe Water
Since water quality degradation may occur in the distribution system, one solution could be widespread implementation of a point-of-entry (POE) water treatment where a system is installed at a household’s or building’s water main intake ahead of the structure’s taps, faucets, or other dedicated outlets used to dispense water for drinking, cooking, and bathing. Typical POU systems contain water treatment technologies such as media filtration, RO membranes, UV disinfection, and remineralization.
A postdoctoral researcher working in Dhaka realized that automated disinfection at the tap would be beneficial in order to make drinking water safe. At the time, most technologies for treating water needed a reliable source of electricity and a constant water supply, and these are access points that most low income communities lack.
Why isn’t a treatment plant that distributes drinking water through a piped system effective in many such communities?
- Their systems supply water intermittently through unpressurized and leaky pipes.
- Contaminants can get in through these leaks.
- Other technologies for purifying water are typically designed for home use.
Amy Dickering and her team determined that automated disinfection could sterilize water in communities where there are many diseases circulating and where there is no access to clean water or sanitation tools.
Enter the Venturi, which automatically dispenses liquid chlorine at the point where users collect water, which is usually a tap connected to a piped system or storage tank. It requires no electricity or moving parts. The research team has tested the Venturi in labs and at field sites in Bangladesh and Kenya, including at community water taps, hospitals, and health clinics. So far, they’ve interested businesses that sell water to customers in and around Kisumu, Kenya in the device.
Because they also want to test this technology’s health benefits in specific settings, they’ve partnered with CARE, an international humanitarian aid organization, to find out whether the Venturi can work reliably in hospitals and clinics in western Kenya. The tests will determine its real life impact.
Techies out there will recognize the derivation of “Venturi.” The Venturi effect is the phenomenon that occurs when a fluid that is flowing through a pipe is forced through a narrow section, resulting in a pressure decrease and a velocity increase. The effect is mathematically described through the Bernoulli equation and can be observed in both nature and industry. Many industry applications rely on this effect as they need to be able to predict a fluid’s reaction when flowing through constricted piping.
The primary challenge faced by the cleantech companies focused on improving drinking water is the varying quality of water available across a wide geographical area, according to a 2022 market report. The chemical and physical properties of water differ from place to place, such as heavy metal contamination or hard and soft water. This means key players need to design either universal water treatment solution or particular treatment solutions targeting particular geographical areas.
Another major challenge to the POU water treatment systems market is the wide penetration of purified water bottle companies that also serve to solve the problem of unsustainable and toxic drinking water. Places like Flint, Michigan have an aggravated problem of lead contamination in drinking water. Thus, bottled water seems to be the safer option compared to POU water treatment systems as perceived by the affected citizens.
It helps that MIT researchers have developed a portable desalination unit, weighing less than 10 kilograms, that can remove particles and salts to generate drinking water. Other innovators are at work, too, drawing upon accepted practices combined with innovative technologies to solve the drinking water crisis that looms on the planet. If you know a credible clean tech innovator whose focus is on safe water at the tap, share the shout-out in the Comments section below.
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