* Marine Coatings 3.7%
Personal Care Products 2%
Plastic Pellets 0.3%
MICROPLASTICSSmall plastics that are produced, such as nurdles and microbeads (primary), or those that degrade from larger pieces of plastic (secondary). Scientists have found microplastics in a dizzying array of places, from human blood and stool to sea ice in the Arctic.
COMMON SOURCESThese are the four most common sources* of microplastics in our environment. Synthetic textiles and vehicle tires account for more than half
of the world’s volume of
Common sources of ingestion of microplastics
by the public include:
• Tap Water
• Bottled Water
• Select Crops
• Clothing Microfibers
• Beer, Plastic Tea Bags
Although most plastic water bottles can be easily recycled, only 15-35% end up in recycling facilities.
End up in landfills
It can take up to 1,000 years for plastic water bottles in landfills to fully decompose.
The regulatory definition of microplastics includes nanoplastics.
VISIBLE TO NAKED EYE
Microplastics can adsorb orders of magnitude more chemicals than the water around them.
Microplastics may include three separate vectors including: inherent toxicity of the insoluble particle, adsorbed chemicals, and microbial pathogens as biofilms.
SMALL HEX NUT
One plastic bottle will, over time, break down into more than 10,000 micro-plastic pieces. Bottled water consistently has higher amounts of microplastics than tap water.
SHAPES along 3 axes
1 nm-100 nm
Three TypesPOLYMETRICComposition of >=1% polymeric materials by mass.
SYNTHETICDoes not occur naturally in the environment.
SOLIDSMaterials cannot be considered a liquid or
When conducting mass balances on wastewater treatment plants, a noteworthy percentage of microplastics are often not traced after the influent. It is believed that these microplastics could occur in the sludge.
Accumulation of microplastics in soil from biosolids has been linked to decreased agricultural yield
Shed from garments in washing machines and drain with the effluent water at much higher volumes than personal care products and cosmetics.
More than 1,900 microplastic fibers
can be released from a
single synthetic garment in one wash cycle. These fibers can pass through the most commonly used screen
filters in wastewater treatment facilities.
Microplastics in drinking water, wastewater effluent, stormwater, and biosolids are a rising challenge across the globe.
A myriad of sources for microplastics enter wastewater facilities, typically hindering utilities from decreasing their occurrence. Beyond municipal sources for microplastics, industrial, stormwater, landfill, and food waste slurry may increase concentrations in the effluent and/or biosolids.
Combined influent from wastewater collection systems collect microplastic debris from the environment and other sources.
Microplastics that meet current reporting criteria often constitute a vast majority of those identified in wastewater effluent.
Removal rates dramatically vary by facility type and the processes employed.
Coagulation, flocculation, and sedimentation in drinking water treatment plants remove high percentages of large and small microplastics. Advanced treatment further increases removal rates.
Finished drinking water typically contains relatively low concentrations of large and small microplastics. Widespread quantification of submicron plastics and nanoplastics in drinking water has not yet been established.
Residuals from wastewater treatment processes are often further conditioned along solid stream processes then land-applied through beneficial reuse as biosolids.
Microplastics in biosolids may accumulate in the soil and early studies indicate plant uptake may occur. Microplastics from the biosolids may also be removed from the upper portions of amended soil to occur in agricultural runoff
Studies indicate that the ultimate fate of many microplastics is in deep sea sediment.
WATER CYCLEMillions of tons of minute plastic debris travel by air, land, and sea, transported in our planet’s water cycle.
Precipitation, runoff, and infiltration deposit the pollutants. Evaporation, transpiration, and condensation, return debris to the atmosphere.
Biomagnification of micro- plastics is occurring, beginning with the smallest organization
in the food chain – zooplankton.
Residue from nets, fishing
line, and paint fragments
from boat hulls, contribute
to microplastic debris.
CAYLA COOK, PE
Cayla is a technical expert on specific soluble and particulate contaminants in water and wastewater.
Lower Removal Rates
REMOVAL RATESResearch is still in the earliest stages for determining the removal rate of various technologies for microplastics. Not all studies quantify removal rates for all particle size ranges, therefore, studies on the same technology may lead to different results when quantifying dramatically different
Some treatment types or aged infrastructure may, in fact, increase microplastic levels.
Higher Removal Rates
REVERSE OSMOSISPerhaps the most puzzling of all results are a variety of removal rates for reverse osmosis (RO). Studies have indicated that zeta potential and temperature play a strong role in the removal of micropollutants that may be associated with microplastics. The size range and morphology, e.g., fibers and fragments, may play a strong role in their removal efficiency.
* Sand filtration data is incomplete due in part to the many variations of sand filtration types/designs.
OXIDATIONStudies often indicate an increase in microplastic quantities following oxidation. This could be due to the embrittlement of softer plastic types like microfibers and/or breakdown caused by shear force. This is also a topic of research in recent years to determine if this degradation can be harnessed for beneficial purposes.
MBRsWhile MBRs are indicated for a higher removal rate than some other technologies, challenges arise with impacts to reversible and slight irreversible membrane fouling due to microplastics.
NOTE: A wide range of
different materials, additives, and degrees of weathering, e.g., fragility of the environ- mental particles, provide
greater difficulty in comparing
laboratory studies to actual influent microplastic qualities.