microplastics removal efficiencies by non-sewered and sewered wastewater treatment systems and potentials of the algal-bacterial system

Wastewater treatment systems (wwtss) are a major source of microplastics (mps) in the environment. in this study, the influent, effluent, and sludge samples from three non-sewered and two sewered wwtss were analyzed. the samples were collected and filtered through two sized mesh sieves (5.6 and 0.3 mm). the retained residues were pretreated and observed under a digital microscope for their abundance and characteristics. results showed that mps concentrations in the influent of the non-sewered and sewered wwtss were 3 – 6 and 1.6 – 2.0 particles/l, respectively, with the removal efficiencies ranging from 83 – 94 and 74 – 78 %. due to their higher mps loading rates and shorter hrt, the sewered wwtss had less efficient in mps removal than the non-sewered wwtss. polyethylene terephthalate (pet) was the most polymer type found in all samples, while fiber accounted for about 70-95% of all samples. the results indicated that the mps in wastewater could be partially removed and accumulated with the sludge in both non-sewered and sewered wwtss. to minimize the impacts of mps contained in the treated effluents, the results of the biosorption experiments showed the potential of the algal-bacterial system in which the operation time of 96 h had the highest biomass production of 220 mg/l and the mp removal efficiency and capacity of 88-90% and 587 mg/g, respectively. because the algal-bacterial system operating at 96 h was effective in cod, tn and tp removal, it is strongly recommended for use in both mp removal and wastewater treatment.