The right kind of filter can keep microplastics out of drinking water

Less than 10% of the plastic that has even been created in the world has been recycled. The fact that plastic does not dissolve but rather breaks down into tiny fragments that might pollute soil and water is one of the main environmental problems with this. Microplastics are tiny plastic granules that are between one micrometer and five millimeters long; nanoplastics are ones that are even smaller than one micrometer.

Water sources including lake water, groundwater, and tap water have so far been proven to contain microplastics, and it is likely that they also include the much smaller nanoplastics. In reality, investigations have found nanoplastics in ice samples from the North and South pole regions, lake water in Switzerland, and even Chinese tap water. However, because it can be difficult to identify them, which can make it harder to address the issue, the exact degree of microscopic plastic contamination of drinking water sources is still unknown.

The potential health impact of small plastic particles

Microplastics were recently discovered for the first time in human blood and live lung tissues, but their implications on human health are still not completely understood. The human gut microbiota may become unbalanced as a result of ingested microplastic particles, which may contribute to the emergence of gastrointestinal illnesses such irritable bowel syndrome and inflammatory bowel disease. A clear connection hasn't been made yet, though.

According to Ralf Kägi, head of the Particle Laboratory at the Swiss Federal Institute of Aquatic Science and Technology, releasing massive amounts of non-biodegradable, synthetic material into the environment—which produces micro- and nano-plastic particles—is not a wise idea, regardless of any risk considerations.

“Nano-plastic particles may have unwanted effects on ecosystems and human health,” he continues. “The smaller the particles, the higher the likelihood that they can be taken up by any organism and distributed, for example, in the gastrointestinal tract.”

Given that nanoplastics are predicted to become more prevalent in water sources as plastics continue to deteriorate, drinking water treatment procedures must be set up to get rid of them.

The number of nanoplastics in water sources is expected to increase in the future as plastics continue to degrade, therefore drinking water treatment processes must be equipped to remove them.

Various filtration processes may help provide drinkable water without plastics

According to several research, drinking water treatment facilities are capable of adequately filtering nanoplastics. According to a study that was published in Science of The Total Environment, a typical drinking water treatment facility can remove nanoplastics by about 88.1 percent when it uses sand and granular activated carbon (GAC) filters, which are the same kind of filters that are used in many water pitcher filters. If coagulation is additionally employed, the removal efficiency can rise to 99.4%.

A separate research that was published in the Journal of Hazardous Materials discovered that slow sand filtration is at least as successful as other treatment methods at removing nanoplastic particles from water sources. This process uses schmutzdecke, a thick, biologically active layer that sits on top of quartz sand to clean water. Prior to reaching the sand layers below it, untreated water flows through the biological layer.

According to Kägi, one of the study's authors, the biologically active layer—which is made up of creatures like bacteria, algae, and protozoans—is particularly good at trapping micro- and nano-plastic particles as well as the vast majority of other particulate materials.

In order to evaluate various water treatment techniques and replicate the removal of nanoplastics in a full-scale drinking water treatment plant, pilot-scale filtering studies were carried out at the Zurich Water Works.

About 70% of the nanoplastics were kept in the first 0.1 meters of the sand bed in the pilot-scale slow sand filtration unit, and the retention rate increased to 99.5 percent at 0.9 meters. Other methods weren't as efficient. For instance, during water treatment, ozonation or the addition of ozone to the water has little impact on the retention of nanoplastics. In contrast, just 10% of the water was retained by activated carbon filtration in the first 0.9 meters of the filter.

Despite how intriguing this information is, slow sand filtering is a somewhat outdated technique. In 1875, it was employed for the first time in the United States. It was nevertheless a promising filtration technique for rural populations even though it progressively lost popularity in the late 1800s due to its sluggish flow rate and inability to handle muddy source waters.

Due to their substantial space needs, slow sand filters are also being phased out in newly built water facilities. These are then swapped out with ultrafiltration, a type of membrane filtration system that physically separates or strains things from water, such sand or algae, using synthetic polymer membranes. Although they are often more costly, Kägi claims that they are less space-consuming and have an efficiency that is equivalent to slow sand filters.

There is very little study on the subject, although membrane-based filtering technologies seem to be more efficient than other methods for removing micro- and nano-plastic particles. According to a research from 2021 that was published in the journal Water Science & Technology, both laboratory and real-scale filtration findings showed that the membrane filtration technology was 100% effective at eliminating microplastics from wastewaters.

“Membrane filtration systems are expected to even outperform slow sand filtration systems regarding the retention of micro- and nano-plastic particles,” according to Kägi. The ability of some water treatment techniques to effectively remove plastic particles from tainted water sources is highly encouraging, but the actual cause of the issue still has to be addressed. In order to provide plastic-free, potable water, reducing plastic use to the absolute minimum is still crucial.