Microplastic distribution and their abundance along rivers are determined by land uses and sediment granulometry

Microplastics in freshwater ecosystems have gained attention for their potential impact on biodiversity. Rivers are complex and dynamic ecosystems that transport particles and organic matter from the headwaters through watersheds to the ocean. Changes in land use and the presence of wastewater treatment plants (WWTPs) increase the risk of plastic contamination. Simultaneously, hydromorphological features of the watershed can influence the dispersion and retention of microplastics. This study assesses the impact of urban land uses and river hydromorphology on microplastic abundance and spatial distribution in two watersheds with contrasting land uses. Unexpectedly, our findings show that microplastics were widespread throughout watersheds both in water (3.5 ± 3.3 particles/L) and sediments (56.9 ± 39.9 particles/g). The concentration of microplastics in sediments significantly increased in granulometry ranging from 0.5 to 1 mm. Microplastics in running waters are significantly correlated with increasing urban land use coverage. However, the presence and distance of WWTPs did not affect microplastic distribution. In conclusion, contrasting patterns were observed for suspended and sedimented microplastic particles: suspended microplastics were associated with an anthropogenic effect, whereas the concentration of microplastics in sediments was determined by riverbed granulometry. Our results suggest that the interaction of anthropogenic and environmental factors shapes microplastic distribution along the rivers and their subsequent transport toward the coastal ocean. Finally, a review of the current literature reveals the absence of standardization in field and laboratory assessment techniques and measurement units, representing a challenge for intercomparisons of river microplastic studies.

Disintegration of biochar adsorbent under the hydraulic conditions of fixed bed water treatment

Recent studies have provided promising evidence for potential applications of biochar in environmental engineering, including its use as an alternative carbonaceous adsorbent for water and wastewater treatment. Carbonaceous adsorbents, such as activated carbon and biochar, are prone to disintegration and erosion due to water flow, potentially leading to the co-transport of hazardous contaminants with eroded fine particles (1 μm or smaller). Despite its significance in overall performance assessment, the stability and erodibility of biochar as an adsorbent in fixed bed water treatment have received limited research attention. This paper presents the results of a series of filtration tests and microscopic examinations to evaluate the disintegration of activated carbon and three types of biochar filters under the hydraulic conditions of fixed bed filtration. A novel testing design was employed to study the effects of fluid velocities and ionic strengths on disintegration, mass loss, and the morphology of granular adsorbents before and after water flushing. The results indicate that disintegration of both activated carbon and biochar is continuous but exhibits different behaviour with pore volume. Although fluid velocity influenced erosion rates, minimal differences were observed in overall mass loss. Ionic strength had a more pronounced impact on the erodibility and stability of particles in suspension by altering electrical conductivity and Zeta potential. Disintegration of hardwood biochar was found to be comparable to that of activated carbon; however, impurities in biochar (elements other than carbon and oxygen) are more likely to be flushed out, creating additional pathways for co-transport of contaminants.

Microplastic biofilms in water treatment systems: Fate and risks of pathogenic bacteria, antibiotic-resistant bacteria, and antibiotic resistance genes

Microplastics (MPs) biofilms in drinking water and wastewater treatment plants (DWTPs and WWTPs) have gained increasing attention due to their potential to come into close contact with humans. This review examines the fate of pathogenic bacteria, antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARGs) in MP biofilms and their impact on operations in DWTPs and WWTPs, as well as the associated microbial risks for ecology and human health. The literature shows that pathogenic bacteria, ARBs, and ARGs with high resistance can persist on MP surfaces and may escape treatment plants, contaminating drinking and receiving water. Nine potential pathogens, ARB, and ARGs can be retained in DWTPs and sixteen in WWTPs. While MP biofilms can improve the removal of MPs themselves, as well as the associated heavy metals and antibiotic compounds, they can also induce biofouling, hinder the effectiveness of chlorination and ozonation, and cause the formation of disinfection by-products. Furthermore, the operation-resistant pathogenic bacteria, ARB, and ARGs on MPs may have adverse impacts on receiving ecosystems, as well as biosecurity issues, including a range of human diseases, from skin infections to pneumonia and meningitis. Given the significant implications of MP biofilms for aquatic ecosystems and human health, further research is necessary on the disinfection resistance of microbial populations in MP biofilm. This study provides valuable insights into the comprehensive understanding of the changes of MP biofilms in water and wastewater treatment systems as well as their impacts on ecology and human health.

Identifying active concentrations of biopolymers for enhancing membrane nanofiltration performance: From bench-scale tests to real production considerations

In the last decades, membrane-based nanofiltration (NF) technique has been widely applied for safe and high-quality drinking water production worldwide. NF membrane fouling has become one of the main obstacles in its application due to high operation cost, and thus numerous efforts have been made. However, there is still a large disconnect between academic findings and their applications. Hence, novel approaches for further exploitation and application are required based on feasibility of implementation. In this work, an optimized design of membrane-based NF plants was proposed, inspired by natural biopolymers present in feed water of NF unit. Specifically, we found beneficial functions of biopolymers, including NF membrane fouling alleviation and effluent quality improvement; these advantages could only be "activated" under a certain concentration range of biopolymers (0-1 mg C/L here), and less or more is not acceptable. This indicated that a NF unit is better to follow a microfiltration (MF) (instead of ultrafiltration (UF) which removes biopolymers) process during which natural biopolymers could be remained; also, this approach is suggested to be valid across different seasons when biopolymers' concentrations could be controlled within an "activated" range by mixing MF and UF permeates. Furthermore, three representative reference biopolymers with different, confirmed spatial structures and molecular weight (MW) were used to elucidate the micro-level functions of natural biopolymers on NF membranes, suggesting that cake layer structures shaped by various biopolymers determine the resulting NF performance. Overall, this innovative proposal is expected to be considered and adopted towards more energy-efficient NF technology for drinking water supply.

Science-society-policy interface for microplastic and nanoplastic: Environmental and biomedical aspects

The global concern over the possible consequences of the downsizing of plastic to microplastics (MPs) and nano plastics (NPs) needs to be addressed with a new conceptual framework. The transformation of plastics to MPs and NPs can be discussed in terms of fundamental physics principles applicable to micro and nanophase matter and colloidal science principles. Further, accurate and reliable detection and characterization of MPs and NPs are crucial for an extensive understanding of their environmental and ecological impacts. The other decisive factor that can classify MPs and NPs as hazardous to existing nanomaterials is discussing the cytotoxicity study on human cell lines. The human health risk assessment that might arise from the ingestion of MPs and NPs can be addressed about contrast agents used for medical imaging. However, the lack of standard analytical techniques for MPs and NPs measurement is an emerging challenge for analytical scientists due to their complex physicochemical properties, especially in environmental samples. This review article navigates readers through the point of origin of MPs and NPs and their interdisciplinary aspects. Biomedical applications of plastics and concerns over the toxicity of MPs and NPs are further analyzed. Moreover, the analytical challenges of MPs and NPs have been discussed with critical inputs. Finally, the worldwide efforts being made for creating a common platform of discussion on a different aspect of plastic pollution were taken into account.

Using excitation-emission matrix fluorescence to evaluate the performance of water treatment plants for dissolved organic matter removal

This study is aimed at assessing the performance of water treatment plants (both wastewater and drinking water treatment plants) for dissolved organic matter (DOM) removal using excitation-emission matrix fluorescence (EEMF) as the monitoring technique. The influent from the wastewater treatment plant (WWTP) of Burgos (Spain) is characterized from the presence of protein-like peaks (T1 and T2) and humic-like peaks (A and C), T2 and A showing the highest fluorescence intensity. The percentages of total removal in the effluent were in the following order: peak T1 (65%) > peak A (45%) > peak C (34%) > peak T2 (26%). The humic-like peaks were the most removed at the primary sedimentation stage, whereas peak T1 was by far the most removed in the biological reactor. Protein-like peaks T1 and T2 experienced a slight increase in the final effluent in comparison to their fluorescence at the previous stage (the exit of the biological reactor), an increase that can be explained by the release of SMP (soluble microbial products) from the biomass in the secondary clarifier. A poor correlation was obtained between peak T2 fluorescence and COD, BOD (r² = 0.34-0.38). The natural water from the Úzquiza reservoir in Burgos (Spain) is characterized by the only presence of humic substances: a majority peak A (fulvic-like) and a weak peak C (humic-like). The whole fluorescent DOM was removed by coagulation-flocculation but a low fluorescence peak T2 appeared at the final stage, coming from protein-like SMPs released by the biomass attached to the filters.

Dataset on physicochemical and microbial properties of raw water in four drinking water treatment plants based in South Africa

The present paper aims at determining the status of surface water quality by applying the treatability index for the raw water in four water treatment plants (WTPs), namely Vaalkop, Klipdrift, Wallmansthal, and Cullinan. These plants are based in South Africa. Sampling was conducted from July 2011 to June 2018 (7 years). The collected water samples were analysed on monthly basis over the specified period. Three Hundred and thirty six (336) water samples were collected and analysed. The Treatability Index (TI) was calculated for twenty-one physicochemical and microbial parameters, which include pH, conductivity, chloride, sodium, potassium, hardness, alkalinity, precipitation potential, turbidity, colour, E. coli, organic carbon, chlorophyll, nitrite, ammonia, nitrates, phosphate, iron, manganese, and sulphate. The computed TI values range from 0.1 to 1755.5 and the water quality was unsuitable for a number of defined uses. The data demonstrated high treatment demand for raw water. On that note, the surface water from the monitored places is not suitable for drinking purposes. The data and treatability index denoted the need for treatment prior consumption. The collected water quality data can be reused for future references, modelling, and trending of historic data to understand current and prospect future changes in the properties of our raw water qualities.

Membrane ageing in full-scale water treatment plants

Membrane filtration is a rapidly expanding choice for drinking water treatment. Unfortunately, there is limited data on long-term changes in the membranes' performance as they age. The present research investigated changes in performance factors as well as chemical characteristics for hollow-fibre ultrafiltration membranes that ranged in age from 8 full-scale drinking water treatment plants. Membranes were harvested by plant operators regularly and analyzed using standardized laboratory tests. Approximately half of the membranes were a new PVDF-based chemistry. These were observed to have insignificant changes in performance factors and chemical characteristics since their beginning of operation. However, because these membranes were newer, only data for the first 5 years of operation was available. The other half of the membranes, with an older PVDF-based chemistry, were observed to have stable behaviour until approximately 5 years of operation; after this time, performance factors and chemical characteristics of the membranes began to change significantly. For these membranes, the clean water resistance and fouling rate increased after 5 years of operation. The mechanical properties of these membranes also deteriorated after 5 years of operation, suggesting that their susceptibility to breach is higher after prolonged use. These changes in performance factors paralleled, and were possibly caused by, the removal of hydrophilic additives from the membrane material. Clean water resistance was identified as a good benchmark for all the parameters studied, a finding that is useful for water treatment facilities in quickly assessing the status of their membranes. Finally, although cumulative exposure dose (C*t) was not used as a metric of membrane age, we observed that when higher doses of hypochlorite were applied, all metrics changed faster than expected based only on years of operation. Therefore, limiting the magnitude of the cumulative hypochlorite dose is essential in managing membrane deterioration. This research illuminates the knowledge gap between bench-scale ageing studies and operational water treatment plants.

Health risk assessment of trihalomethanes in water treatment plants in Jiangsu Province, China

Probabilistic lifetime cancer risks and non-cancer risks of trihalomethanes (THMs) through ingestion, dermal contact, and inhalation exposure in 88 drinking water treatment plants (WTPs) with raw waters from five water systems (WSs) in Jiangsu Province were analyzed and compared. Concentrations of THMs in finished water of study WTPs varied, ranging from 18.81 to 38.96 μg/L, which are lower than the maximum of 80 μg/L recommended by USEPA. The results of health risk assessment indicated that cancer risk as well as non-cancer risks of THMs in WTPs sourced from five water systems decreased in the order of WS3 > WS5 > WS2 > WS1 > WS4. The comparison among multiple exposure routes indicated that when non-boiled drinking water is consumed, ingestion has the highest exposure route, with exposure values greater than dermal contact and inhalation for WTPs with raw water from all five water systems. However, when drinking boiled water, dermal contact is the major risk source for WTPs with raw water from WS1 and WS2, instead of dermal contact, inhalation becomes the major risk source for WTPs with raw water from WS3, WS4, and WS5. In WTPs with raw water from water systems WS1, WS3, WS4, and WS5, dibromochloromethane (DBCM) in THMs has the highest contribution to cancer risk, while chloroform in THMs has the highest contribution to non-cancer risk. However, in WTPs with raw water from water system WS2, bromodichloromethane (BDCM) has the highest contribution to both cancer risk and non-cancer risk. The results also indicated that females are prone to cancer risk induced by THMs since Chinese people are accustomed to drinking boiled water. The results supply valuable information for health departments to put forward more specific and efficient policies to control water borne diseases.

Water treatment plant site location using rough set theory

Currently, advanced methods have been developed to select an appropriate site for an engineering project. The ability to make a good decision in site selection can help the engineers to reduce the expensive costs, which are very important in large construction projects. In this paper, a new approach for site selection is presented. This method is based on rough set theory which is a mathematical theory presented by professor Pawlak. In this study, the results of the rough set decision-making are compared with the results of the regression method in a practical case study for the site location of a water treatment plant in Ardabil Province in the northwest of Iran, to demonstrate that the rough set theory provides a useful method for site selection. The results of practical studies indicate that using this method for site selection decision-making can reduce costs and prevent hazards that may happen due to civil engineering uncertainties.