Oral Presentation Society of Environmental Toxicology and Chemistry Australasia 2023

A nexus of contaminants: understanding the potential risks and benefits of wastewater microplastics and their plastisphere communities (#160)

Olga Pantos 1 , Regis Risani 2 , Joanne Kingsbury 1 , Louise Weaver 1 , Hayden Masterton 1 , Jessica Wallbank 3 , Stefan Maday 3 , Maisie Hopkins 4 , Gavin Lear 3
  1. The Institute of Environmental Science and Research, Ilam, Christchurch, New Zealand
  2. SCION, Rotorua, New Zealand
  3. University of Auckland, Auckland, New Zealand
  4. University of Canterbury, Christchurch, New Zealand

Wastewater treatment plants (WWTPs) are a rich source of microbes, microplastics (MPs) and chemical contaminants. Plastics provide a physical surface for microbes to settle and benthic communities to develop. Chemicals are also a key component of the plastisphere, present in both the plastic substrate and associated biofilm. These include both chemical additives inherent in the plastics, and extrinsic chemicals from other sources, which in the WWTP environment includes heavy metals, pharmaceuticals, biocides and industrial chemicals. The surface properties and polymer type of plastics, as well as the associated chemicals may all influence plastisphere composition and function and consequently their potential environmental impact. Of specific concern are pathogenic and antibiotic-resistant bacteria (ARB) which have previously been identified within the plastisphere of microplastics discharged from WWTPs, therefore suggesting MPs act as vectors and refugia for microbes, allowing them to enter the environment untreated.

This is the first study to examine WWTP plastisphere microenvironments in New Zealand. The relationship between plastics, chemical contaminants and microbes present in the WWTP system and therefore their potential impact on release into the environment were examined. Next-generation sequencing was applied to identify changes in microbial biofilm community composition, biogeochemical function and putative pathogens and ARB presence as well as potential plastic degraders on five common plastics of either unaged or artificially UV-aged condition. Biofilm was sampled after 2, 6, 26 and 52 weeks of constant submersion in an oxidation pond. Trace elements in both the biofilm and plastics were analysed using ICP-MS at the same time points.

Plastisphere communities did not correspond to plastic-associated trace elements, but biofilm chemistry varied over time.Potential human fungal and bacterial pathogens varied with substrate type and time, with abundance of anti-microbial resistance genes predominantly those involved in antibiotic inactivation and antibiotic efflux. Fungal and bacterial plastic degraders demonstrated temporal differences.