Project Overview

Artificial turf arenas, originally developed for their durability and low maintenance, have fundamentally shifted from a sustainable solution to a significant, growing contributor to microplastic contamination. This environmental risk is driven by the degradation of turf fibers due to mechanical wear from cleats, weathering, and UV radiation. The resulting fragments, containing toxic polymers, primarily polyethylene (PE) and polypropylene (PP), are transported through the sub-surface drainage layers and directly discharged into adjacent waterways, posing serious and complex ecological risks.

Currently, technology to mitigate this contamination is only conceptual. Existing concepts often propose implementing filtration solely through catch basins within the existing drainage network. However, these solutions are characterized by high operational costs, complex installation, and a susceptibility to clogging. This absence of a robust, preventative filtration strategy embedded within the field structure itself represents a critical technological gap that must be addressed. 

This void creates a unique opportunity to create a cost-effective, multi-layered filtration system designed for implementation during new field construction. The success of this approach is rooted in the efficiency of adsorption and sediment technologies. Filtration media, specifically selected sediments and adsorbents, are effective at removing polymer ions due to their unique surface area, surface charge, and hydrophobic interactions with microplastics. Since common sediments are already a cheap and common subsurface fill, integrating a functional filtration layer is highly feasible. 

To ensure the system's effectiveness, the filtration layers must be chemically tuned to the specific contaminants identified in the field’s runoff. As Table 1 details the compounds present, the core challenge is designing layers that exhibit a high chemical affinity for PE and PP. Therefore, the primary objective of this project is to successfully implement and validate a layered filtration system that demonstrates sustained, high-efficiency removal of these specific microplastic compounds from turf runoff.

Box

• 6 - 2 x 2 x 2 ft. box

• Plywood siding, held together with 2 x 4's. Plexiglass front for viewing port while water filters through sediment.

• Engineered slope for drainage at the bottom of the box

• Mesh over PVC outlet for drainage capture

Sediment Layers

Six filtration configurations were developed to compare removal efficiency, hydraulic performance, and cost. Across all boxes, base layers include graded sand, geotextile separators, and course gravel to minimize infiltration and prevent particle movement. The primary filtration media between all six boxes is as follows:  

• Activated Carbon
  This media showcases the highest microplastic adsorption efficiencies of 80-95% due to its highly porous structure and large surface area, which traps and holds particles as water flows through. However, activated carbon is the most expensive material among these options. 

• Natural Fibers
  Natural Fibers, when layered above activated carbon, increase retention of polyethylene microplastics because of their porous structure with internal channels that aid in water flow. This is an inexpensive and renewable option to test amongst activated carbon properties. 

• Biochar
  This media is a charcoal-like material made from biomass that is heated through pyrolysis. It is stated to capture 70-90% of microplastics with a significantly lower cost relative to activated carbon. Its high porosity and adsorption made biochar the best performance-to-cost ratio media. 

• Pine Bark
  Pine bark captures microplastics through its porous structure and chemical attraction through tannic acid, that mind to microplastics. With biochar, this combination provides most capture efficiency, but higher cost that could be equal to activated carbon. 

• Sawdust and Polyphenol-Treated Media
  Sawdust and polyphenol, when paired, have a filtration effectiveness of 90-99%. This is the highest filtration out of the six designs, but is by far the most costly. This solution is effective for higher cost, higher filtration needs. 

• Granular Limestone
  Limestone is stated to remove 50-70% of microplastics through filtration and surface roughness effects. It performs lower than the other filtration groups but provides a low-cost option to sports field arenas.