Biological treatment shaping microplastic-associated microbial communities in wastewater treatment plant

Abstract

Microplastics (MPs) are mostly released into the environment by wastewater treatment plants (WWTP). MPs in wastewater serve as substrates for microbial colonization, facilitating biofilm development. Previous studies have demonstrated that MP biofilm communities can bypass WWTP treatment and infiltrate the receiving environment. Thus, understanding how MP biofilm communities change following the WWTP treatment stages is crucial. This study evaluated the microbial communities of raw wastewaters and MP biofilms at different WWTP treatment stages. Five wastewater samples from a WWTP were collected: influent, post-preliminary, post-primary, post-sequencing batch reactor (SBR), and post-disinfection. Two different types of MPs, polypropylene (PP) and polyethylene (PE), were utilized for generating biofilms in wastewaters. A significant decrease in the physicochemical characteristics of the wastewater following SBR treatment was noted. The PCoA analysis revealed that the microorganisms in PP biofilms and PE biofilms were classified into two separate groups: the pre-SBR group and the post-SBR group. The changes in microorganisms inside the MP biofilms before and after SBR were thoroughly analyzed at the phylum, class, and species levels. A modest correlation was seen between the two primary bacterial species and the environmental markers (EC, COD, TSS, and NH4+). The results showed that SBR reduced wastewater contaminants and changed MP biofilm communities. SBR also significantly lowered the quantity of bacteria sticking to MPs and increased microorganism selectivity. The research findings enhance understanding of MP biofilm progress at WWTPs, facilitating the suggestion of operational modifications to enhance the MP biofilm treatment.