- A TOTALLY PREVENTABLE SOURCE
At the recent, Sixth International Marine Debris Conference (March 12-16, 2018, San Diego, CA), the problem of microplastics was a major topic, one of great interest to anyone associated with wastewater treatment but particularly to wastewater treatment plants (WWTPs), as they put it.
There are no current requirements on wastewater treatment plants (WWTPs) to address this issue, but it may be coming – something a person may see if they follow discussions at international conferences such as these. The title of the session was, Microplastics in Wastewater Treatment Plants – A Totally Preventable Source.1
Below are three of the session abstracts, as listed on their website.
Hrissi Karapanagioti, et al. wrote:
“Marine pollution by microplastics, plastic particles in the size range 1 nm to 5 mm, is a recognized emerging issue. Although they [wastewater treatment plants (WWTPs)] remove the solid waste arriving to their screens, they are not designed to remove microplastics. There are a few studies measuring the concentration of microplastics in the effluent. It seems that the concentrations are low but the actual amount ending up in the sea is quite significant. The present study is an extensive study surveying 101 WWTPs in various areas throughout Greece. Based on the results, the total amount of solid waste arriving to these 101 WWTPs is calculated equal to 3.7 108 L per week. Screens collect this amount but 94% of the WWTPs have screens with gaps larger than 5 mm. This suggests that microplastics are passing through preatreatment to the main WWTP.
Indeed, 89% of the WWTP managers observed microplastics anywhere in the plant. Cotton swabs are identified as the most common microplastic found in WWTPs and the surrounding marine and coastal areas of the effluent pipes. Informing the public as well as operators and engineers about this problem is necessary.”1
Paul Helm, et al. wrote:
“Contamination by microplastic particles (MPPs) is well-documented in marine, and more recently, freshwater environments. Sampling in urban streams, wastewater effluents, and nearshore waters of the Great Lakes has shown that there are numerous types of MPPs entering the lakes. Typical reporting of MPP research and monitoring results includes the listing of abundances (counts per unit area, volume, or mass) and grouping of types of MPPs into broad categories such as fragments, film, foam, fibers, and pellets/beads. However, such broad categories may be insufficient for directing management actions for MPPs reductions and to measure the success of such actions.
We present morphological characteristics of MPPs, which can be used to expand their source-type categorization/classification. For example, rigid plastic particles resembling shavings, cuttings, and trimmings clearly generated by mechanical means, normally categorized as ‘fragments’, are indicative of commercial plastic activities. These ‘commercial fragments’ comprised a significant portion (>50%) of the up to 19 million MPPs/square km found in Humber Bay along the waterfront of Toronto, Canada. Our 2015 sampling of nearshore waters, streams and wastewater effluents in this region of the Great Lakes demonstrates the influence of more specific sources when detailed categories are used to characterize MPP profiles. Emissions of MPPs, likely from plastic product manufacture and recycling, are indicated to be a significant source to western Lake Ontario, and these findings form the basis for advice to resource managers regarding strategies to reduce to the occurrence of MPPs in the Great Lakes.”1
Artem Dyachenko, et al. wrote:
“A regional effort to optimize sampling, extraction, identification and quantitation of microplastic particles in secondary Wastewater Treatment Plant (WWTP) effluent is presented. The study found that wastewater samples require special handling in order to remove inherent organic material-related interferences. Sequential wet peroxide oxidation (WPO) digestion leads to cleaner extracts with significantly reduced amounts of major wastewater related interferences such as cellulose and fatty acids. An attempt to count and type microparticles extracted from secondary wastewater effluent has been made and results were extrapolated using WWTP’s average daily flow rates. Findings reveal significant discrepancy in microparticle count in extracts obtained from two hour sampling at peak flow and 24 hour composite sampling events.
The vast majority of microparticles could be categorized as fragments whereas pellets or beads appear to contribute less than 10% of the overall microparticle count. Many microplastic particles in wastewater are not homogenous with traces of other compounds present and visual microscopic identification alone is not sufficient in determining microplastics presence, which should be confirmed with an appropriate spectroscopic technique (e.g. micro-FTIR). Normal handling of some microplastic particles during analysis led to fragmentation, which could bias the final results. The need for a robust screening and quantitation of micorplastics with the tools accessible to wastewater laboratories and challenges of current methodologies are discussed.”1
From another angle the Nebraska Extension Educator Meghan Sittler recently answered a question that further shows these concerns.
Q: I recently read concerns about microplastics in municipal wastewater systems. Is that something I need to be concerned about in my own wastewater system?
Meghan: Microplastics are defined by the National Oceanic and Atmospheric Administration (NOAA) as ‘small plastic pieces less than five millimeters in length’ (that’s about the size of a sesame seed). Microplastics can occur from larger plastic pieces that have broken a part, from residues used in other plastic products or increasingly commonly as microbeads, which are used in face scrubs, body washes or other personal care or household cleaning products. Plastics, other than a small percentage made of biodegradable material, do not readily break down over time.
Municipal wastewater systems are concerned about the build-up of these microplastics within their infrastructure used to treat and discharge wastewater. Similar concerns are valid for onsite wastewater systems. Depending on the size and amount of the microplastics as well as the components of your system, build up or blockage can occur, cause damage, and limit the functionality of your system. Additionally, the microplastics if included in the treated water discharged from your system, will enter the soil profile and can ultimately end up in groundwater or surface water resources.
A federal law, passed in 2015, bans the use of microbeads in personal care products by the end of 2019. However, it is a good idea to take stock of what products you may have in your home and consider purchasing microbead or microplastic free products to protect your system and the environment.”2
Whichever way this goes, Wastewater treatment plants (WWTPs) are becoming more of the common language. We don’t generate this waste, but as long as we are being looked as ‘A Totally Preventable Source,’ we may need to give this issue a closer look.