Semi-crystalline microplastics in wastewater plant effluents and removal efficiencies of post-treatment filtration systems

Implications of the operation of continuous granular activated carbon filters on the effluent quality

Granular activated carbon (GAC) filtration is a commonly used method for advanced wastewater treatment. Filters can be operated continuously or discontinuously, with continuous operation not requiring feed flow interruption for backwashing and circulation (B/C). This study investigated the influence of B/C on the effluent quality of continuous filters. Two continuous GAC filters were operated for 1.5 years, with analysis of dissolved substances and particulate matter in the influent and effluent. The results indicated that various B/C modes had no impact on the removal of dissolved organic carbon and organic micropollutants (OMP), achieving an OMP removal of over 70% after 5,600 treated bed volumes (m3 treated wastewater per m3 GAC). However, it was evident that continuous B/C over 2-4 h resulted in increased turbidity, total suspended solids over 30 mg/L and total phosphorus concentrations of 1.3 mg/L in the filter effluent. Additionally, the study demonstrated that longer and more intensive B/C processes resulted in GAC size degradation with AC concentrations of up to 6.9 mg/L in the filter effluent, along with a change in GAC particle size. Furthermore, the importance of pre-filtration in reducing particulate matter in the filter influent and decreasing hydraulic head loss could be demonstrated.

Microplastics in a small river: Occurrence and influencing factors along the river Oker, Northern Germany

Much attention regarding the environmental pollution by plastics had focused on the Oceans. More recently, contamination of freshwater ecosystems has been addressed but information from smaller rivers in moderately populated catchments is still comparatively scarce. This study explored the microplastic (MP) occurrence in the small regional river Oker, Northern Germany (catchment area 1822 km2, population of ca. 500,000, discharge approx. 12 m3 s-1). MPs (fibers and fragments in the size range 0.3-5 mm, identification by microscopy) were found in all 10 in-stream samples collected along the course of the river, ranging between 28 and 134 particles m-3 with an overall average of 63 particles m-3. This MP concentration found in the small river Oker is similar to, or higher than, that reported for larger rivers in similar environments in Central Europe. On average, higher MP concentration was found at urban (71 particles m-3) compared to rural sampling sites (51 particles m-3). Within the Oker catchment, in-stream MP concentration showed no or low correlation to the catchment-scale factors of catchment size and population. Additional samples taken from three locations directly influenced by discharges of potential MP point sources confirmed wastewater treatment plants of different capacities and an urban rainwater sewer as sources. Our results support findings that MP concentrations in small rivers are crucially influenced by local sources, superimposing linear relationships to factors of catchment size and -population. They show that even small rivers draining moderately populated catchments may exhibit comparatively high concentrations of MPs, and thereby represent underestimated pathways of MP in the environment.

A review of microplastics in wastewater treatment plants in Türkiye: Characteristics, removal efficiency, mitigation strategies for microplastic pollution and future perspective

The effluent of WWTPs is an important source of microplastics (MP) for the aquatic environment. In this review study, MPs in wastewater treatment plants (WWTP) in Türkiye and their removal from WWTPs are reviewed for the first time. First, MP characteristics in the influent and effluent of WWTPs in Türkiye are discussed. In the next section, the abundance of MPs in the influent and effluent of WWTPs in Türkiye and the MP removal efficiency of WWTPs in Türkiye are evaluated. Then, the results of studies on MP abundance and characteristics in Türkiye's aquatic environments are presented and suggestions are made to reduce MPs released from WWTPs into the receiving environments. Strategies for reducing MPs released to the receiving environment from WWTPs of Türkiye are summarized. In the last section, research gaps regarding MPs in WWTPs in Türkiye are identified and suggestions are made for future studies. This review paper provides a comprehensive assessment of the abundance, dominant characteristics, and removal of MPs in WWTPs in Türkiye, as well as the current status and deficiencies in Türkiye. Therefore, this review can serve as a scientific guide to improve the MP removal efficiency of WWTPs in Türkiye.

Adsorption interactions between typical microplastics and enrofloxacin: Relevant contributions to the mechanism

Microplastics (MPs) are increasingly contaminating the environment and they can combine with antibiotics as carriers to form complex contaminants. In this study, we systematically investigated the interactions between the antibiotic enrofloxacin (ENR) and MPs comprising polyethylene (PE), polyvinyl chloride (PVC), and polystyrene (PS). Characterization was performed by using conventional techniques and the mechanisms involved in interactions were initially explored based on adsorption kinetics, isotherms, and resolution experiments, and the adsorption capacities of the MPs were determined. In addition, the extended Derjaguin-Landau-Verwey-Overbeek theory was used to investigate the interaction mechanisms. The results showed that the interactions were weaker in strong acidic and alkaline environments, and the interactions were also inhibited at higher salt ion concentrations. The saturation adsorption amounts of ENR on PVC, PE, and PS were 74.63 μg/g, 103.09 μg/g, and 142.86 μg/g, respectively. The interactions between MPs and ENR were dominated by hydrophobic interactions, followed by van der Waals forces and acid-base forces. This study provides new insights into the adsorption behavior of ENR by MPs.

Emerging isolation and degradation technology of microplastics and nanoplastics in the environment

Microplastics (MPs, less than 5 mm in size) are widely distributed in surroundings in various forms and ways, and threaten ecosystems security and human health. Its environmental behavior as pollutants carrier and the after-effects exposed to MPs has been extensively exploited; whereas, current knowledge on technologies for the separation and degradation of MPs is relatively limited. It is essential to isolate MPs from surroundings and/or degrade to safe levels. This in-depth review details the origin and distribution of MPs. Provides a comprehensive summary of currently available MPs separation and degradation technologies, and discusses the mechanisms, challenges, and application prospects of these technologies. Comparison of the contribution of various separation methods to the separation of NPs and MPs. Furthermore, the latest research trends and direction in bio-degradation technology are outlooked.

Microplastic removal in managed aquifer recharge using wastewater effluent

Microplastic (MP) pollution has emerged as a pressing environmental issue, with its impacts on ecosystems and human health yet to be fully understood. This study aims to investigate the presence and distribution of MPs in the soil of a managed aquifer recharge (MAR) system, built with different reactive barriers of natural materials and irrigated with the secondary effluent of a wastewater treatment plant (WWTP). MPs were extracted from reactive barrier material following an approach based on the density separation of MPs with posterior oxidant digestion, combined with visual and chemical characterisation by Fourier-Transform Infrared Spectroscopy (FTIR). The results revealed the widespread occurrence of MPs in the MAR soil samples. MPs concentration in the different barrier materials ranged from 60 to 236 n kg-1. The most dominant morphologies were fragments (60%) and fibers (17%), and the most abundant colour was white (51%), followed by transparent MPs (20%). Polypropylene (PP) was detected in all the samples with an abundance of 47%, followed by polyethylene (PE, 34%). The interplay of barrier composition significantly influences the retention of MPs, with compost (T5) and woodchips (T4) exhibiting the most notable retention rates. Remarkably, the outer layers of the reactive barriers display superior retention compared to the deeper layers. The findings of this study demonstrate the good performance of the MAR system in retaining MPs and contribute to the growing body of knowledge on MPs pollution in freshwater systems while providing insights into the dynamics of MPs transport and accumulation in soil. Such information can inform the development of effective wastewater management strategies to mitigate the impacts of these pollutants on water resources and safeguard the environment.

A review of microplastic removal from water and wastewater by membrane technologies

Microplastics (MPs) cannot be completely removed from water/wastewater in conventional wastewater treatment plants (WWTPs) and drinking water treatment plants (DWTPs). According to the literature analysis, membrane technologies, one of the advanced treatment technologies, are the most effective and promising technologies for MP removal from water and wastewater. In this paper, firstly, the properties of MPs commonly present in WWTPs/DWTPs and the MP removal efficiency of WWTPs/DWTPs are briefly reviewed. In addition, research studies on MP removal from water/wastewater by microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), and membrane bioreactors (MBRs) are reviewed. In the next section, membrane filtration is compared with other methods used for MP removal from water/wastewater, and the advantages/disadvantages of the removal methods are discussed. Moreover, the problem of membrane fouling with MPs during filtration and the potential for MP release from polymeric membrane structure to water/wastewater are discussed. Finally, based on the studies in the literature, the current status and research deficiencies of MP removal by membrane technologies are identified, and recommendations are made for further studies.

Quantification of microplastics in wastewater systems of German industrial parks and their wastewater treatment plants

Microplastics (MP) enter the aquatic environment via several pathways. Many research groups have focused on municipal discharge, while research on industrial sources is rare. This study provides one of the first insights into MP occurrence and distribution in the wastewater systems of industrial parks (IPs) and their wastewater treatment plants (IPWWTPs). The effluents from production plants as well as influent, effluent, and internal samples from the IPWWTPs were assessed. Sampling methods for parallel MP mass and number analyses were developed for varying conditions. The total item emissions of MP (≥10 μm) into the environment were analyzed using μ-Raman spectroscopy and ranged from 3 · 10² to 8 · 10⁴ MP m^-3, with a median of 6 · 10³ MP m^-3 per IPWWTP. Masses analyzed using differential scanning calorimetry showed an MP mass discharge into the environment of 0.2 to 11 mg m^-3 with a median of 3.7 mg m^-3 per IPWWTP. MP item concentrations within an IPWWTP varied by two to three log levels over several days. Fibers were rare in all samples. Polymer types varied depending on the types of industrial sites and the production plants discharging into the IPWWTP. Within an IP, MP could be allocated to its dischargers, which could be useful for future regulatory requirements. Further research is needed to include different types of IPs producing various polymers and additional processing plants to expand this data set.