(469h) Interactions of Graphene Oxide with the Microbial Community of Biologically Active Filters from a Water Treatment Plant

With widespread occurrence and increasing concern of emerging contaminants in source water, biologically active filters (BAF) have been gaining acceptance in water treatment. Granular activated carbon (GAC), with its extensive surface area, micro-sized pores, and durable structure, provides a supporting substrate for advancing sustainable biofilms in BAF systems. In recent years, graphene oxide (GO) has been exploited to treat contaminants including atrazine, cephalexin, chloroquine, dipyrone, and drug-resistant bacteria and pathogens. Interestingly, in recent studies, GO has demonstrated biocompatibility through interactions with living organisms. Furthermore, with a surface area greater than GAC, the GO provides potentially more interactions between the substrate, contaminants, and microorganisms. As a result, GO in a GAC-BAF composite may enhance microbial growth and stimulate biodegradation in a BAF system. However, interactions between GO and the microbial community in water treatment processes such as BAFs remain unstudied. Therefore, in this research, we investigated the effect of GO on the properties and bacteria growth rate in a GAC-based BAF. The GO synthesized was characterized with a number of tools, including scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectrometry. Results demonstrated that GO exhibited the characteristic surface functional groups, particle size, and morphology. The GAC-BAF samples in this study were collected from the Passaic Valley Water Commission (PVWC) in New Jersey, that serves water to a significant portion of Northern New Jersey. Source water was prepared to simulate the influent water composition of the treatment plant and used as a culture medium for this study. The effect of GO on microbial growth was assessed through adenosine triphosphate (ATP) analysis by exposing the microbial community of GAC-BAF (200 mg/L) to GO concentrations (25 μg/L to 1000 μg/L) over 48 h. With an initial ATP concentration in the GAC-BAF of 26-70 ng ATP/cm³, results showed an increase to 660 ng ATP/cm³ after incubating in source water without GO (control). Interestingly, significant increases in ATP concentrations were observed by as much as 5% to 52% in the presence of GO compared to the control without GO. The growth rate was fit with the Monod equation revealing it exceeded the control by 20% to 46%. Specifically, the specific growth rate constant in the control batch (0.111 ± 0.01) h^-1 increased by approximately 50% (0.162 ± 0.01) h^-1 when exposed to 25 μg/L of GO. To address the potential toxicity of GO on the microbial community, reactive oxygen species (ROS) generation was measured using nitro blue tetrazolium (NBT) assay. During the exponential growth phase, compared to the control, ROS generation was not observed in the presence of GO. Further experiments are being conducted to characterize the BAF microbial community upon exposure to GO concentrations using Next-generation sequencing (Illumina MiSeq). This research provides new insights into the application of a bio-optimized BAF for advanced and sustainable water treatment or water reuse.