Microplastics in the NZ water environment - should we be worried?

Garry Macdonald, Business Development Director – Water Market Segment (Beca Ltd)

Bridget Rule, Associate Environmental Engineer – Water (Beca Ltd)

Nicole Fahrenfeld, Associate Professor – Civil & Environmental Engineering (Rutgers University, New Brunswick, NJ, USA)

Belinda Sturm, Professor – Environmental Engineering and Associate Vice Chancellor (University of Kansas, Lawrence, KS, USA)

One of the most topical emerging contaminants in the water environment is microplastics. There are many sources of these microconstituents in our wastewater streams due to the ubiquity of plastics used in modern society, thereby becoming prevalent in all municipal and industrial waste streams, and in the water environment. The quantity and composition of microplastics entering wastewater treatment plants and ending up either captured or released into the environment are the subject of much international research effort. If captured in the liquid stream processes, there is also great interest in which stage microplastics ultimately sequester and what impact they have on the quality and end-uses of biosolids and reuse water streams, as well as how macro-plastics break down, over time, into micro- and nano-plastics.

It appears from university research and monitoring at USA and European WWTPs (Microplastics in the Water Environment: Should We Be Worried and Why?, Knowledge Development Forum: WEFTEC 2020, New Orleans) that conventional secondary and tertiary treatment processes are very successful at removing a range of microplastics, however given the large effluent flow volumes, even small concentrations of micro- and nano-plastics can still be a large burden discharged to the marine and freshwater environment. This is without any consideration of how stormwater discharges with macro- and micro-plastic content are also contributing to this contamination of our environment.

This session, of significance to wastewater systems and stormwater operators and managers, will bring together a range of national and international research to discuss the current state of knowledge on microplastics, and where our research and management efforts on microplastics should be focused in the near and long-term, as well as implications for treatment process selection and standardisation of analytical techniques. In New Zealand, we can expect in the near future higher standards for our WWTP discharges – and probably our stormwater discharges - and we must be in a position to determine the optimum liquid stream and solid stream processes to ensure that microplastics do not become any more of a problem in our aquatic and land environments than they are now.