Microplastics R&D

It is no secret that much of the plastic produced and used throughout the world ends up in waterways. Often it takes the form of “microplas­tics,” tiny bits about the size of a sesame seed that have broken apart or have been inten­tion­ally designed that way. Microplas­tics can also come from degraded trash, as well as from the large volume of other items such as nurdles (pre-production plastic pellets) or flake plastics that can be released during production, a major issue at production facilities as well as with shipments to plastic extrusion or use facilities.

Research into microplas­tics’ impact is in its early stages. Stan­dard­ized field methods for collecting samples have been developed and are continuing to evolve, but still much is unknown about these materials and their impact on the environment and public health. Among the challenges to under­stand­ing are that the smallest microplas­tics are under 50 microns, small semi-plastics can show up in the water column, and all can be ingested and consumed by biota.

The petro­chem­i­cal industry is keenly aware of the need to know more about and address microplas­tics and their release into the environment. During pellet and flake production at petro­chem­i­cal plants, occasional upsets occur and fine-grained and film-like plastic debris—pellets, flakes, and powder—are released from facility operations areas. Pellet loss occurs at various stages of operation such as storage, bulk container loading or unloading, and sampling. For instance, small amounts of pellets remain on top of the railcars after product loading, which are later blown by the wind to ground. These solids are lighter than water and generally tend to float, so if left uncontained, the plastic debris gets swept into stormwater systems and to outfalls or treatment facilities, and ultimately into lakes, rivers, and oceans.

To further investigate into how water treatment tech­nolo­gies may contend with the unwanted release of microplas­tics, CDM Smith is working with a polymer plant in Texas to conduct research treata­bil­ity studies that ultimately aim to keep plastic waste from reaching our nation’s waterways. To do so, CDM Smith has engaged one of our state-of-the-art labo­ra­to­ries in Denver, Colorado, to char­ac­ter­ize microplas­tics and evaluate feasible treatment approaches.

“This R&D work is important in preventing further escalation of plastics entering our waterways,” says Kevin Molloy, vice president at CDM Smith, “partic­u­larly throughout the Gulf Coast, where many petro­chem­i­cal plants produce polypropy­lene pellets or related plastic debris.”

“Realizing source control and stormwater management are key to discharge prevention, we are performing a microplas­tics char­ac­ter­i­za­tion and treata­bil­ity study in the laboratory,” explains Todd Burgesser, CDM Smith analytical chemist. “Once this analysis is completed, we will know the most effective water treatment approach to design in order to capture this debris and stop it from reaching nearby waterways.”

The preliminary work included a site visit to the polymer plant to understand the site conditions and how plastic partic­u­lates affect onsite wastewater and stormwater. Various settleabil­ity tests were conducted to assess gravity separation of plastic particulate. Sieve analysis specific to plastic pellets (ASTM D1921) helped to determine particle size distri­b­u­tion.

This lab work along with stormwater modeling allowed CDM Smith’s research team to develop the design basis criteria for effective stormwater management and treatment for plastic pellets, with floatation, filtration and screening evaluated for the proposed outfall improve­ments. Under­stand­ing the behavior of plastic partic­u­lates as a whole and the potential residual polymer after treatment helps define a cost-effective treatment approach.