Mechanism of nanoplastics capture by jellyfish mucin and its potential as a sustainable water treatment technology.

The accumulation of nanoplastics (NPs) in the environment has raised concerns about their impact on human health and the biosphere. The main aim of this study is to understand the mechanism that governs the capture of NPs by jellyfish mucus extracted from the jellyfish Aurelia sp. (A.a.) and compare the capture/removal efficiency to that of conventional coagulants and mucus from other organisms. The efficacy of A.a mucus to capture polystyrene and acrylic NPs (∼100 nm) from spiked wastewater treatment plant (WWTP) effluent was evaluated. The mucus effect on capture kinetics and destabilization of NPs of different polymer compositions, sizes and concentrations was quantified by means of fluorescent NPs, dynamic light scattering and zeta potential measurements and visualized by scanning electron microscopy. A dosing of A.a. mucus equivalent to protein concentrations of ∼2-4 mg L-1 led to a rapid change in zeta potential from a baseline of -30 mV to values close to 0 mV, indicating a marked change from a stable to a non-stable dispersion leading to a rapid (<10 min) and significant removal of NPs (60 %-90 %) from a stable suspension. The A.a. mucus outperformed all other mucus types (0-37 %) and coagulants (0 %-32 % for ferric chloride; 23-40 % for poly aluminum chlorohydrate), highlighting the potential for jellyfish mucus to be used as bio-flocculant. The results indicate a mucus-particle interaction consisting of adsorption-bridging and "mesh" filtration. Further insight is provided by carbohydrate composition and protein disruption analysis. Total protein disruption resulted in a complete loss of the A.a. mucus capacity to capture NPs, while the breaking of disulfide bonds and protein unfolding resulted in improved capture capacity. The study demonstrates that natural jellyfish mucin can capture and remove NPs in water and wastewater treatment systems more efficiently than conventional coagulants, highlighting the potential for development of a new type of bio-flocculant.

Microplastic distributions in a domestic wastewater treatment plant: Removal efficiency, seasonal variation and influence of sampling technique.

Wastewater treatment plants (WWTPs) serve as an important route of microplastics (MPs) to the environment. Therefore, more effective MPs sampling and detection methodologies, as well as a better understanding of their influence on MPs occurrence and distributions in WWTP effluents, are needed for better removal and control. In this work, the efficiency of a municipal WWTP to remove MPs was assessed by collecting samples from raw to tertiary effluent during a 12-month sampling campaign (season-based) using different sampling methods (containers, 24-h composite and large grab samples). MPs retrieved from different treatment units within the WWTP were identified and quantified using plastic/non-plastic staining followed by optical microscopy, SEM and µ-Raman microscopy. Overall, the mean removal efficiency of MPs in the WWTP was 97%, with most MPs removed by the secondary stage and a mean effluent concentration of 1.97 MPs L-1 after sand filtration. The relative abundance of particles was lower than fibers in treated effluent compared with the raw wastewater, with MP fibers constituting 74% of the total MPs in raw wastewater and 91% in treated effluent. Taking seasonal variations into account is important as total MPs concentration in the effluent was notably higher in winter compared with the other seasons. Increasing the sampled volume using large samples or 24-h composite samples significantly reduced the variability between replicates. However, MPs concentration post the tertiary stage was significantly lower using morning sampling (9 am) by large grab sampling method (1.2 MPs L-1) compared to 24-h composite sampling (3.2 MPs L-1) possibly due to intra-daily changes. Using a finer mesh size (0.45 µm) to capture MPs beyond the size range typically studied (≥20 µm) effectively doubled the number of MPs detected in the tertiary effluent and highlights the importance of standardizing sampling procedures.