Anaerobic digestion can help remove microplastics — a large cause of water pollution — during the sewage treatment process
Microplastics, or tiny fragments of plastic, include microbeads, the plastic pellets present in thousands of household and personal care products, including toothpaste, cosmetics, and beauty scrubs. They also include fragments from the breakdown of anything in our lives made out of plastic — even synthetic fabrics.
The surface of microplastic particles can host pathogenic bacteria and other pollutants, which can be more harmful than the bacteria commonly found in riverine environments.
Because of their small size, many pass unfiltered through the wastewater treatment process. They make their way down the drain and into waterways all the way to the ocean, where they cause water pollution. Microplastics pose an environmental hazard for aquatic animals, both in fresh water and in seawater.
Solving the Microplastics Problem
While some cosmetic companies are removing microbeads from their ingredient lists and some municipalities, states, and countries have already banned their use, hundreds of billions of microplastics particles are already present in the environment. One important step to solving the problem is to prevent microplastics from entering the waterways in the first place.
Anaerobic digestion (AD) is showing promise as another prospective solution.
A recent study, published in Environmental Science & Technology, reveals that AD can be an effective method of reducing the amount of microplastic in sewage sludge. The study shows that AD is much more effective at reducing the particles than other common methods such as thermal drying or lime stabilization. While the study collected only a few samples, researchers are still calling the results promising and deserving of further study.
A lot of attention has been paid to these particles in oceans, but so far there’s much less research into the effect of microplastics in freshwater systems and farmland.
Benefits of Anaerobic Digestion
This potential of anaerobic digestion to reduce microplastics pollution is just one of its benefits. It’s used in waste-to-energy plants to generate biogas, which is used to produce thermal energy and electricity, which can be sold to the grid or used on-site to save money. Capturing the gaseous byproducts of waste digestion also reduces greenhouse gases that escape unused into the atmosphere.
Many waste materials can be treated with anaerobic digestion, making it a renewable energy source. Wastewater from breweries, paper mills, dairies, sludge from food processing plants, as well as biomass, food waste, manure, and agricultural waste are all good candidates for AD. This digestion process can lead to the reduction of sludge volume by up to 90%, significantly reducing the amount sent to landfills.
Overall, anaerobic digestion offers several promising solutions to reduce pollution in landfills and waterways. Besides the technology’s ability to turn waste into energy and reduce waste bound for landfills, it may also offer a solution to reducing the microplastics pollution.
The full study — “Microplastics in Sewage Sludge: Effects of Treatment,” is available from Environment Science & Technology/ACS Publications.