By Peter S. Cartwright, PE
We are constantly exposed to particles in our environment: in the air we breathe, the food we eat and the water we drink. This article addresses the latter. Particles can be classified as either natural in origin (dirt, silt, dust, microorganisms, etc.) or from anthropogenic sources (human made). This article addresses particles generated by human activities. A significant contributor to this contamination is tire particles. As of 2017, the quantity of these particles is estimated to be 270,000 tons/year.(1) And yet, the major contributor to anthropogenic pollution is plastics.
It is estimated that since the beginning of large-scale production and use in about 1950, more than 7,000-million tons (8,300-million metric tons) of virgin plastics have been manufactured to date.(2) These include all plastics, but the primary resins are the low- and high-density polyethylenes. As of 2015, less than nine percent of plastics are recycled, 12 percent incinerated and the remaining 79 percent thrown away or landfilled every year.(2) Virtually none of these plastics is biodegradable.
Figure 1 illustrates the global production, use and fate of plastic resins, fibers and additives (in metric tons).(2) Figure 2 is chronological and based on assuming today’s rate of use and disposal practices. The solid lines show historical data to 2015; the dashed lines are projections to 2050.(2) Globally, more than 300 million tons of plastic per year are manufactured and eventually thrown away.(2) Think about it: one million plastic bottles are manufactured every minute throughout the world and that rate is expected to increase 20 percent by 2021.(3) The National Park Service estimates that Americans use (and discard) 500-million plastic drinking straws each day!
Regardless of where they originate (household, store, manufacturing plant, etc.), plastics are flushed down the sink and toilet, landfilled, incinerated or just carelessly discarded. Those that become part of sewage sludge or a landfill ultimately end up in the soil or in a water body (lake, river, ocean). It is estimated that between 10- and 20-million tons of plastic reach the ocean every year and the rest end up in the soil.(1,4,5) Note that virtually every lake and river ultimately discharges into an ocean, sea or gulf. Somewhere between 90,000 and 1,000,000 tons of plastic bits are estimated to be inadvertently added to soils during agricultural activities annually.(6) Figure 3 illustrates an overview of plastic pollution (data are metric).(6)
Although plastics will not biodegrade, most are readily broken down by ultraviolet radiation from the sun and movement within the oceans. Regarding the sizes of these particles, some experts use the designations noted in Table 1.
Concentration measurements of the smaller microplastics (as well as all of the nanoplastics) using the traditional TSS analytical procedure (Standard Methods 2540 D) are difficult because this procedure specifies that filter-disc products from any one of five manufacturers be used and the pore sizes of these discs vary from 0.7 to 1.5µ. This means that particles below at least 0.7µ are not even counted.
Some particles will sink, while others will float. Considerable publicity has been devoted to gyres, huge areas of floating plastic in the oceans. Five separate gyres have been identified, with the area of the largest claimed to be as big as the state of Texas.(4) One study estimates that that there are 5.25 trillion (that’s 5,250,000,000,000) particles floating on ocean surfaces, weighing almost 270,000 tons.(7) And yet, floating particles are believed to represent only one percent of all the plastics in the oceans. Whereas about five percent of the total weight of plastics is located on beaches, the remaining 94 percent is either on the ocean floor or trapped in glaciers.(8) Figure 4 illustrates the sources and weight of plastic particles in the oceans.(8)
The ubiquitous nature of these particles on and in ocean sediment is underscored by the fact that a recent study found particles in crustaceans dwelling at the bottom of the deepest trenches in the oceans. These trenches are as deep as 36,000 feet below the surface. Between one-half and all of the animals sampled had particles in their guts.(9) Plastic particles also include synthetic fibers in textile products. Although fibers can enter the environment simply through the wearing of clothes, the greatest contribution to our water supplies is from the action of washing. One study found that acrylic fabrics released 730,000 fibers per wash, five times more than polyester/cotton fabric and 50 percent more than polyester.(1) A comprehensive academic study examined 159 globally sampled tap waters and found that 81 percent contained plastic fibers greater than 2.5 microns in length.(10)
Accurate data on quantities of particles in our water supplies are extremely difficult to obtain; however, there are numerous estimates out there. One predicts that if our rate of plastics production continues and no mitigation measures are taken, by 2050 (on a weight basis), there will be more plastic in the oceans than fish.(11) The same study indicates that nearly all sea birds and half of sea turtles have plastics in their bodies. In 2005, an albatross was found with plastic debris in its gut from a World War II plane that had crashed in the ocean more than 5,000 miles away.(6)
An indication of the extremely slow rate of plastics decomposition in the water environment can be found in Table 2. It is important to note that the decomposition of plastics does not make them go away; they just break down into smaller and smaller particles.
Another issue with plastic particles in water is that they adsorb soluble pollutants known as pharmaceutical and personal care products (PPCPs ). There are estimated to be more than 85,000 dissolved organic chemicals in all water supplies, ranging from prescription drugs to soluble consumer, industrial and agricultural products.(4) In addition, bacteria readily attach to surfaces and form biofilm colonies on the particles, which then absorb even more chemicals. These attached contaminants are often released into the water stream. Although THMs (trihalomethanes) are disinfection byproducts, they are dissolved organic compounds similar to PPCPs.
Obviously, the presence of particles in water means that they are in our drinking water. Treatment plant filtration technologies are incapable of removing particles much below 10µ in size. Although accurate counts are virtually impossible to obtain, a significant percentage of the total volume of plastics in the environment is estimated to be in the micro and nano size range: less than 10µ. Whether plastic particles have an effect on human health is unknown at this time, but, intuitively, particularly with the fact that PPCPs are associated with them (and supported by documented effects on aquatic creatures), it’s difficult to believe that a link will not ultimately be identified.
As the result of behavior based on ignorance, carelessness or just plain arrogance, we have gotten into this mess of contaminants that just won’t go away. Is there anything we can do about it? Well, yes we can and here are some strategies.
Regulatory. The US EPA Long Term 1 Enhanced Surface Water Treatment Rule (virtually identical to the WHO requirements) mandates that for drinking water produced by conventional and direct filtration systems, “…samples for turbidity must be less than or equal to 0.3 NTU in at least 95 percent of the samples in any month.” While there is technically no direct relationship between turbidity and suspended solids (one is light scattering by suspended materials and the other total weight of particles above a certain size), they are both related to the suspended solids content of a water sample. These solids include dirt, dust, sand, colloids, algae, pollen and all microorganisms, such as Cryptosporidium and Giardia (and of course, plastic). A turbidity of 0.3 NTU is roughly equivalent to a TSS level in the range of 0.05 to 0.10 mg/L. So for municipal supplies, this rule ensures that the total concentration of particles in our drinking water should be less than 0.10 mg/L (ppm).
With regard to wastewater discharge, the most detailed regulations appear to be those from US EPA. The Secondary Treatment Standard requires that the 30-day average of TSS from a publicly owned treatment works (POTW) not exceed 30 mg/L. Wastewater reuse is gaining momentum and innovative technologies are being employed to produce fit-for-purpose supplies. These will certainly mandate TSS reduction, but based on the above stated limitations of current TSS measurement technology, it is important to realize that, in actuality, many more tiny particles may actually be present.
Material changes. There have been a number of biodegradable plastic polymers developed over the years (primarily based on corn starch), but cost and some questionable claims have limited their acceptance by the consumer. Biodegradable plastic bags for kitchen scraps are widely available in Europe now. Plastic straws are virtually always used only once and are so small and light that they are rarely recycled. An edible (and biodegradable) drinking straw made from seaweed is now on the market.(13) Known as Lolistraw, this product exemplifies the out-of-the-box thinking required to address these issues.
Behavioral changes. Humankind must rethink how we look at particle pollution. If we continue to use chemical products based on fossil fuels, we must be aware that they cannot decompose into the basic chemical building blocks of carbon and water. We must embrace recycling as never before. Most thermoplastics can be recycled and such plastics as polyethylene terephthalate (drinking and soda bottles) can be easily reused for the same purpose. Consumers must demand deposits on bottle purchases. Deposits provide a strong incentive to take bottles back to the store where recycling is facilitated. A number of states have mandated this and it is widely practiced in Europe.
There is no good reason why plastic carrier (single-use) bags should not be banned. This practice is widely accepted in Europe and some US states; some local communities also have bans in place. Some communities mandate that stores only supply paper bags to the shopper; however, the carbon footprint of paper bags is as high as that of plastics, although paper is recyclable and renewable. Obviously, the real solution is to bring a reusable bag on all shopping trips and many consumers have voluntarily embraced this practice. Although a number of manufacturers of consumer products are advertising that they have (or intend to) adopt sustainable practices, the initiative really must come from the consumer.
The world’s largest recyclable materials importer, China, has recently informed the World Trade Organization that it will ban imports of 24 categories of these materials. In 2017, China imported 16-million tons of waste plastics from the developed world, with the US accounting for over three-million tons.(14)
Regarding textiles, the current trend of fast fashion (take-make-and-dispose) is frightening and it is estimated that the equivalent of one garbage truck of clothes is discarded every second. Five-hundred-thousand tons of microfibers end up in the ocean every year.(15) This reference outlines a movement to persuade manufacturers to phase out the use of hazardous materials, to recycle old fabrics and to use renewable resources.
Treatment technologies. Concerning our drinking water, municipal treatment is largely ineffective in removing suspended solids below 10-20µ and only if the water undergoes media filtration. Roughly 10 percent of the suspended solids will be absorbed by the sludge. The same is true with municipal wastewater treatment plants, with the notable exception of those plants with MBR technology. This treatment is much more effective because it utilizes MF/UF membrane technology, as described below.
Only those technologies capable of extremely fine filtration will remove the small particles. The cross-flow, pressure-driven membrane separation technologies of microfiltration, ultrafiltration, nanofiltration and reverse osmosis are all capable of removing particles to one degree or another. The key is particle size. Most microfiltration membranes are effective down to at least 0.1µ; ultrafiltration can remove particles in the 0.01µ range and nanofiltration should be able to remove down to 0.005µ. Reverse osmosis, the tightest of all, should remove virtually any size particle. Additionally, this technology, combined with activated carbon adsorption, will also significantly reduce the concentration of PPCPs and other dissolved chemicals.(4)
There isn’t much we can do about the huge quantity of plastics now covering this planet. Certainly, efforts can be made to recover and recycle plastics in landfills and gyres; however, our primary activities should concentrate on minimization of disposable and other discarded plastics in the future. Although the manufacturer has the ultimate responsibility for this remediation activity, to ensure success, the initiative must begin with the consumer.
- Geoff Fisher, “Marine Litter and Microplastics—Problem or Opportunity?” Fiber Engineering, December 2017. www.fiberjournal.com.
- Roland Geyer, Jenna R., Jambecle, Kara Lavender Law, 19 July 2017, “Production, use, and fate of all plastics ever made.” Science Advances 2017; 3; e1700782.
- Sandra Laville, Matthew Taylor, “A million bottles a minute: world’s plastic binge ‘as dangerous as climate change’.” The Guardian, June 28, 2017. https://www.theguardian.com/environment/2017/jun/28/a-million-a-minute-worls-plastic-bottle-binge-as-dangerous-as-climate-change
- Peter S. Cartwright, “The Next Drinking Water Contamination Issue.” Water Conditioning & Purification International. August 2017. email@example.com.
- Timothy Hoellein, “Wastewater Treatment Plants Significant Source of Microplastics in Rivers, New Research Finds.” American Geophysical Union. 24 February 2016.
- EE Ling Ng, “Planet Plastic.” The Scientist, June, 2017, www.the-scientist.com.
- Marcus Eriksen, et. al. “Plastic Pollution in the World’s Oceans: More than 5 trillion plastic pieces weighing over 25,000 tons afloat at sea.” December 10, 2014, Plos One. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0111913.
- Eunomia Research and Consulting, Ltd. “Plastics in the Marine Environment.” June 2016. www.eunomia.co.uk.
- Stephanie Pappas, “Even at 36,000 feet deep, ocean creatures have plastic in their guts,” November 16, 2017, Live Science. https://www.livescience.com/60954-plastic-found-in- deepest-livving-dreatures.thml?utm_source=notification.
- Mary Kosuth, Sheri A. Mason, Elizabeth V. Wattenberg, Anthropogenic contamination of tap water, beer, and sea salt. In review.
- Sarah Kaplan, By 2050, there will be more plastic than fish in the world’s ocean, study says. Washington Post Morning Mix, January 20, 2016.
- The Microbead-Free Waters Act: FAQs. https://www.fda.gov/Cosmetics/GuidanceRegulation/LawsRegulations/ucm531849.htm.
- Straw Pollution Is a Huge Problem. Here’s a Solution. https://www.care2.com/greenliving/straw-pollution-is-a-huge-problem-heres-a-solution.html.
- China bans foreign waste—but what will happen to the world’s recycling? The Independent. https://www.independent.co.uk/environment/china-foreign-waste-ban-recycling-a8011801.html
(15) Fast-Fashion’s Environmentally Destructive Habits. https://www.alternet.org/print/environment/fast-fashion-environmentally-haunting-trends
About the author
Peter Cartwright entered the water purification and wastewater treatment industry in 1974 and has had his own consulting engineering firm since 1980. He has a degree in chemical engineering from the University of Minnesota and is a registered Professional Engineer in that state. Cartwright has provided consulting services to more than 250 clients globally. He has authored over 300 articles, written several book chapters, presented over 300 lectures in conferences around the world and is the recipient of several patents. Cartwright also provides extensive expert witness testimony and technology training courses. He is on numerous editorial advisory boards and technical review committees of several trade publications and a frequent lecturer in numerous technical conferences globally. Cartwright is a recipient of both the Award of Merit and Lifetime Member Award from the Water Quality Association and is the Technical Consultant for the Canadian Water Quality Association. He was the 2016 McEllhiney Distinguished lecturer for the National Ground Water Research and Educational Foundation and gave over 35 lectures throughout the world on groundwater contaminant mitigation. Cartwright can be reached via email, firstname.lastname@example.org or visit his website, www.cartwright-consulting.com