Drinking Water Treatment Processes Research Articles

The effectiveness and feasibility of ball-milled powdered activated carbon (BPAC) for removal of organic pesticides in conventional drinking water treatment process

In the conventional drinking water treatment process (CDWTP), powdered activated carbon (PAC) is commonly used for removing organic pesticides, or other organic contaminants. However, the hydraulic retention time (HRT) in CDWTP is insufficient for fulfilling PAC adsorption equilibrium to realize its full capacity. This study examined the adsorption kinetics, adsorption thermal dynamics, and removal efficiency for six organic pesticides using the ball-milled PAC (BPAC) with varying particle sizes in CDWTP. Based on the experiments with the pesticides of atrazine, diazinon, dimethoate, fenitrothion, isoproturon and thiometon, the results indicated that as the particle size reduced from around 38 μm for the commercial PAC to 1 μm for the BPAC, the adsorption rates for hydrophobic pesticides increased up to twentyfold. Diffusional adsorption from the bulk solution to the external PAC surface is the most likely predominant mechanism. This could allow a sufficient pesticides’ adsorption within the limited HRT and to achieve a great depth removal of these toxic compounds. However, the addition of BPAC with a diameter of 1 μm was observed to significantly increase residual particles in treated water after the conventional treatment process. With a further systematic evaluation of both adsorption rate and particle penetration, a particle size of around 6 μm BPAC was considered a practical compromise between the adsorption rate and particle penetration for real application. Results from five surface waters of different water quality indicated that, compared to commercial PAC, application of 6 μm BPAC could achieve up to a 75% reduction in adsorbent dosage while maintaining around the same pesticide removal efficiencies. Additionally, thermodynamic analyses suggest that adsorption of these pesticides could be enthalpically or entropically driven depending on the degree of pesticide hydrophobicity.

The coagulation process for enveloped and non-enveloped virus removal in turbid water: Removal efficiencies, mechanisms and its application to SARS-CoV-2 Omicron BA.2

The coagulation process has a high potential as a treatment method that can handle pathogenic viruses including emerging enveloped viruses in drinking water treatment process which can lower infection risk through drinking water consumption. In this study, a surrogate enveloped virus, bacteriophage Փ6, and surrogate non-enveloped viruses, including bacteriophage MS-2, T4, ՓX174, were used to evaluate removal efficiencies and mechanisms by the conventional coagulation process with alum, poly‑aluminum chloride, and ferric chloride at pH 5, 7, and 9 in turbid water. Also, treatability of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a recent virus of global concern by coagulation was evaluated as SARS-CoV-2 can presence in drinking water sources. It was observed that an increase in the coagulant dose enhanced the removal efficiency of turbidity and viruses, and the condition that provided the highest removal efficiency of enveloped and non-enveloped viruses was 50 mg/L of coagulants at pH 5. In addition, the coagulation process was more effective for enveloped virus removal than for the non-enveloped viruses, and it demonstrated reduction of SARS-CoV-2 Omicron BA.2 over 0.83-log with alum. According to culture- and molecular-based assays (qPCR and CDDP-qPCR), the virus removal mechanisms were floc adsorption and coagulant inactivation. Through inactivation with coagulants, coagulants caused capsid destruction, followed by genome damage in non-enveloped viruses; however, damage to a lipid envelope is suggested to contribute to a great extend for enveloped virus inactivation. We demonstrated that conventional coagulation is a promising method for controlling emerging and re-emerging viruses in drinking water.

Cost-effective synthesis of magnetic graphene oxide nanocomposite from waste battery for the removal of arsenic from aqueous solutions: Adsorption mechanism with DFT calculation

In this study, magnetic graphene oxide (MGO-Fe3O4) nanocomposite was prepared by co-precipitating of FeCl3.6H2O and FeCl2.4H2O on waste battery-derived graphene oxide and used as an adsorbent for the efficient removal of As(III) from aqueous solutions. The prepared nanocomposite was characterized by Fourier transformed infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, zeta potential, and a vibrating sample magnetometer. These characterizations revealed that spare like Fe3O4 nanoparticles (10.5 nm) were decorated on graphene oxide nanosheets and showed excellent saturation magnetization (89.73 emu/g). The adsorption of As(III) by MGO-Fe3O4 was optimized by analyzing various parameters. Experiments showed that 98 % of As(III) was removed at neutral pH in a just 20 min, even though the adsorbent dose was only 0.14 g/L. The adsorption kinetic and isotherm were best fitted with the pseudo-second order kinetic and Frendlich isotherm model. The maximum adsorption capacity (qmax) was found to be 50.2 mg/g at room temperature. Thermodynamic studies showed that the As(III) adsorption process was spontaneous and exothermic in nature. The enhanced adsorption capacity and magnetic properties of MGO-Fe3O4 are crucial in the drinking water treatment process due to the easy magnetic separation of MGO-Fe3O4 from aqueous solution after the adsorption process. Density Functional Theory (DFT) was also used to investigate the interaction between MGO-Fe3O4 and As(III), which further suggested that MGO-Fe3O4 and As(III) mostly interact with each other through surface complexation and hydrogen bonding.

Applying Recurrent Neural Networks and Blocked Cross-Validation to Model Conventional Drinking Water Treatment Processes

The jar test is the current standard method for predicting the performance of a conventional drinking water treatment (DWT) process and optimizing the coagulant dose. This test is time-consuming and requires human intervention, meaning it is infeasible for making continuous process predictions. As a potential alternative, we developed a machine learning (ML) model from historical DWT plant data that can operate continuously using real-time sensor data without human intervention for predicting clarified water turbidity 15 min in advance. We evaluated three types of models: multilayer perceptron (MLP), the long short-term memory (LSTM) recurrent neural network (RNN), and the gated recurrent unit (GRU) RNN. We also employed two training methodologies: the commonly used holdout method and the theoretically correct blocked cross-validation (BCV) method. We found that the RNN with GRU was the best model type overall and achieved a mean absolute error on an independent production set of as low as 0.044 NTU. We further found that models trained using BCV typically achieve errors equal to or lower than their counterparts trained using holdout. These results suggest that RNNs trained using BCV are superior for the development of ML models for DWT processes compared to those reported in earlier literature.

Application and environmental impact of loose nanofiltration in surface water treatment

Loose nanofiltration (LNF) membranes with a molecular weight cutoff (MWCO) of about 1000 Da have great potential for high selectivity between natural organic matter (NOM) and mineral salts. Therefore, they are interesting for treatment plants for purifying oligotrophic lake waters with an elevated NOM concentration. This study was conducted to determine the design and operational expenses as well as the environmental impact of an LNF-based drinking water treatment process that removes NOM from Finnish surface water. Two LNF membranes with similar MWCOs were selected, and the results were compared to ultrafiltration, nanofiltration, and conventional treatment. One LNF membrane demonstrated a rejection rate of NOM higher than 95 % and a low rejection rate of hardness at about 40 %, while the other LNF membrane performed similarly to an ultrafiltration membrane. The LNF-based treatment process would increase operational expenses by 53—69 % but at the same time decrease the environmental impact by >18 %. Improved removal of aromaticity and low molecular weight compounds could lower the disinfection byproduct formation potential and microbial growth in the network, thus reducing the required chlorine dosage in the network and possibly bringing further cost savings.

Removal efficiency and mechanism of geosmin by modified micro-nano bubbles in drinking water treatment process

The problem of odor and taste caused by geosmin had been widely discussed globally. While existing water treatment processes were difficult to remove geosmin cleanly and efficiently, and the traditional aeration method of micro-nano bubbles (MNBs) led to low removal efficiency due to the low probability of collision between the bubbles and the contaminants. In this study, micro-nano bubble modification technique was used to improve the removal efficiency. Three surface modifiers, hexadecyl trimethyl ammonium bromide (CTAB), chitosan (CTS), and poly dimethyl diallyl ammonium chloride (PDADMAC), were selected for this study. The effects of the surface modifiers on the properties of MNBs and the effects of these changes on the removal efficiency of GSM were explored. The experimental results showed that when all three modifiers were dosed at 5 mg/L, the PDADMAC-modified MNBs had the best GSM removal effect of 70.9 %, while the Zeta potential of the effluent was lower at 4.17 mV, which had less influence on the downstream process, and was an ideal modifier. The contribution of various removal pathways to GSM removal was also explored through intermediate product analysis combined with variable control experiments. The experimental results showed that the enhanced removal of GSM was attributed to the enhanced capture of GSM by PDADMAC-modified MNBs and the enhanced oxidation of GSM by PDADMAC-modified MNBs. At the same time, the removal efficiency of this process in natural waters decreased by <5 % only. This study could provide data and theoretical support for the enhanced removal of olfactory compounds by modified MNBs for application in practical engineering.

Performance of Rapid Sand Filter Dual Media for Microplastic Removal in the Water: The Effect of Microplastic Size and Effective Size of Filter Media

Microplastics (MPs) significantly damage the environment and human health, leading to a growing global concern. MPs have been detected not only in the natural environment but also in the drinking water treatment process. One of the configurations of the drinking water treatment unit is filtration. Only a few research studies have been published on microplastic removal in the water system. This study was conducted to determine the performance of a rapid sand filter (RSF) in removing microplastics in water with a variation in the effective size (ES) of silica sand and microplastic size. In this study, microplastics are artificially made with size variations of &lt; 400 μm and &gt;400 μm. The filtering uses two variations in the adequate size (ES) of silica sand, namely 0.4 mm and 0.7 mm. At the same time, anthracite is only a control variable with ES = 0.69 with a flow speed of 4 m / h and an observation time of 30, 60, 90, and 120 minutes. The results show that the filter media ES 0.4 has the highest efficiency values of 91.30% for the microplastic size MPs &lt;400 µm and 95.80 % for the larger microplastic &gt;400 µm. In addition, the average percentage removal of ES 0.7 mm was 77.24 % for the size of MPs &lt;400 µm and 95.77% for the size of Mps &gt;400 µm. Gaining insight into the mechanisms involved in removing microplastics from drinking water is essential for developing more effective techniques for eliminating them.

Comprehensive effects of microplastics on algae-laden surface water treatment by coagulation-ultrafiltration combined process: Algae cultivation, coagulation performance and membrane fouling development

In coastal areas, the surface water has been simultaneously exposed to the algae blooms caused by eutrophication and the microplastics (MPs) pollution originating from active human activities. As a practical alternative to address these issues in drinking water plant, coagulation-ultrafiltration combined process is still confronted with the limited understanding about the comprehensive effects of MPs on algae-laden surface water (ASW) treatment. Considering the migration of MPs in nature environment and drinking water treatment process, this study first aims to systematically investigate the influence of MPs on algae cultivation, coagulation performance and membrane fouling development. The results of algae cultivation indicate that MPs stimulated the algae activity by 58 % and then constantly suppressed the secretion of protein-like, humic-like and polysaccharide-like metabolites. The variation of particle size distribution and zeta potential confirm that MPs acted as nuclei to facilitate the development of large coagulation flocs with an increasing average size from 82.6 μm to 107.6 μm, during which the negatively charged pollutants were neutralized and removed from ASW. According to the SEM images, MPs could destroy the structure of fouling layer on 50 kDa membranes during the filtration of ASW coagulation effluent. Its synergistic effect with the enhanced coagulation performance and the suppressed EOM secretion contributed to the alleviation of membrane fouling caused by overlapped large-sized foulants. However, the interaction between the enriched organic foulants by MPs and the deposited coagulants on 300 kDa membranes facilitated the development of cake layer, leading to the deterioration of membrane permeability. This study emphasizes the importance in concerning the existence of MPs during the treatment of ASW by coagulation-ultrafiltration combined process and their exact influence in water purification efficiency.

Dihalogenated nitrophenols in drinking water: Prevalence, resistance to household treatment, and cardiotoxic impact on zebrafish embryo

Dihalogenated nitrophenols (2,6-DHNPs), an emerging group of aromatic disinfection byproducts (DBPs) detected in drinking water, have limited available information regarding their persistence and toxicological risks. The present study found that 2,6-DHNPs are resistant to major drinking water treatment processes (sedimentation and filtration) and households methods (boiling, filtration, microwave irradiation, and ultrasonic cleaning). To further assess their health risks, we conducted a series of toxicology studies using zebrafish embryos as the model organism. Our findings reveal that these emerging 2,6-DHNPs showed lethal toxicity 248 times greater than that of the regulated DBP, dichloroacetic acid. Specifically, at sublethal concentrations, exposure to 2,6-DHNPs generated reactive oxygen species (ROS), caused apoptosis, inhibited cardiac looping, and induced cardiac failure in zebrafish. Remarkably, the use of a ROS scavenger, N-acetyl-l-cysteine, considerably mitigated these adverse effects, emphasizing the essential role of ROS in 2,6-DHNP-induced cardiotoxicity. Our findings highlight the cardiotoxic potential of 2,6-DHNPs in drinking water even at low concentrations of 19 μg/L and the beneficial effect of N-acetyl-l-cysteine in alleviating the 2,6-DHNP-induced cardiotoxicity. This study underscores the urgent need for increased scrutiny of these emerging compounds in public health discussions.

Removal of Human Coronavirus OC43 (HCoV-OC43) in Simulated Drinking Water Treatment Processes

Removal of Human Coronavirus OC43 (HCoV-OC43) in Simulated Drinking Water Treatment Processes

Is monochloramine pre-oxidation a viable strategy for enhancing the treatment efficiency of algae-laden water with conventional drinking water treatment process?

Algal blooms worldwide pose many challenges to drinking water production. Pre-oxidation with NaClO, KMnO4, or ozone is commonly used to enhance algal removal in conventional drinking water treatment processes. However, these currently utilized oxidation methods often result in significant algal cell lysis or impede the operation of the subsequent units. Higher algal removal with pre-chlorination in algal solutions prepared with natural water, compared to those prepared with ultrapure water, has been observed. In the present studies, preliminary findings indicate that ammonium in natural water alters chlorine species to NH2Cl, leading to improved treatment efficiency. NH2Cl with 1.5–3.0 mg∙L−1 as Cl2 with an oxidation time of 3–7 h significantly enhancing algal removal by coagulation. The selective oxidation of surface-absorbed organic matter (S-AOM) by NH2Cl, followed by the subsequent peeling off of this material from the algal surface, leading to an increase in zeta potential from −20.2 mV to −3.8 mV, constitutes the primary mechanism of enhanced algal removal through coagulation. These peeled S-AOM retained their large molecular weight and acted as polymer aids. Compared with NaClO and KMnO4, NH2Cl displays the best performance in improving algal removal, avoiding cell lysis, and decreasing the potential for nitrogenous disinfection byproducts formation under the reaction conditions used in this study. Notably, in major Chinese cities, water purification plants commonly rely on suburban lakes or reservoirs as water sources, necessitating the transportation of raw water over long distances for times up to several hours. These conditions favor the implementation of NH2Cl pre-oxidation. The collective results indicate the potential of NH2Cl oxidation as a viable pretreatment strategy for algal contamination during water treatment processes.

Study on Conventional Drinking Water Treatment for Removing Emerging Contaminants: A Literature Review

Emerging contaminants (ECs) are substances that can be synthetic or natural, or even microorganisms that are usually not monitored in the environment and could be harmful to the environment and human health. These chemicals can include pharmaceuticals, such as ibuprofen and acetaminophen, and industrial chemicals, e.g., perfluorooctanoic acid (PFOA). Common conventional drinking water treatment plants (CDWTP) are not designed to remove emerging contaminants, so these compounds can enter the water system and affect the drinking water treatment process. This study aims to focus on the performance of CDWTP in removing ibuprofen, acetaminophen, and PFOA parameters, as well as determine suitable water treatment units to eliminate these parameters from the system. An extensive literature review was conducted and further analysed using descriptive and qualitative analysis to understand the unit performance in removing emerging contaminants, followed by the simple simulation to determine the types of advanced drinking water treatment facilities that perform better in eliminating ECs. The results show that CDWTP could reduce ibuprofen concentration in water with 40%, 20%, and 36% efficiency through coagulation-flocculation, sand filtration, and disinfection, respectively. Acetaminophen removal is up to 67%, 51%, and 66.45% during coagulation-flocculation, sand filtration, and disinfection, respectively. However, PFOA removal is only up to 5%, 7%, and 2% during coagulation-flocculation, sand filtration, and disinfection, respectively. Membrane treatment technology with reverse osmosis could remove ibuprofen, acetaminophen, and PFOA compounds more effectively with removal efficiencies of 99.99%, 96%, and 100%, respectively.

Sulfidated nanoscale zero-valent iron derived from iron sludge for tetracycline removal: Role of sulfur and iron in reactivity and mechanisms

Iron sludge, produced during the drinking water treatment process, can be recycled as potential iron resource to create environmental functional material. In this study, sulfur-iron composites derived from iron sludge (S–Fe composites) was synthesized through sulfidation and carbonization, and used for the tetracycline (TC) removal under aerobic and anoxic conditions. The reactivities of these as-prepared products were strongly depended on pyrolysis temperatures. In particular, sulfidated nanoscale zero-valent iron loaded on carbon (S-nFe0@CIS) carbonized at 800 °C exhibited the highest TC removal efficiency with 86.6% within 30 min at circumneutral pH compared with other S–Fe composites. The crystalline structure of α-Fe0, FeSx and S0 as main active sites in S-nFe0@CIS promoted the degradation of TC. Moreover, the Fe/S molar ratios significantly affected the TC removal rates, which reached the best value as the optimal S/Fe of 0.27. The results illustrated that the optimized extent of sulfidation could facilitate electron transfer from nFe0 towards contaminants and accelerate Fe(III)/Fe(II) cycle in reaction system compared to bared nFe0@CIS. We revealed that removal of TC by S-nFe0@CIS in the presence of dissolved oxygen (DO) is mainly attributed to oxidation, adsorption and reduction pathways. Their contribution to TC removal were 31.6%, 25.2% and 28.8%, respectively. Furthermore, this adsorption-oxygenation with the formation of S-nFe0@CIS-TC* complexes was a surface-mediated process, in which DO was transformed by the structural FeSx on complex surface to •OH with the generation of H2O2 intermediate. The intermediates of TC and toxicity analysis indicate that less toxicity products generated through degradation process. This study provides a new reclamation of iron sludge and offers a new insight into the TC removal by S-nFe0@CIS under aerobic conditions.

Optimization of Breakpoint Chlorination Technologies for Drinking Water Treatment: a Hungarian Case Study

Ammonium ion is one of the major pollutants found in drinking water sources in Hungary, especially in deep aquifers. under oxidative conditions, ammonium can transform into nitrite ions in the water system, posing potential health risks. In Hungary mostly biological process or breakpoint chlorination are used to eliminate ammonium ion from raw water during the drinking water treatment process. When breakpoint chlorination is applied, harmful by-products are formed. Trihalomethanes concentrations have long been regulated in Hungary, therefore during the design and optimization of the breakpoint technologies trihalomethane concentrations have been considered. However, haloacetic acids (HAA5) and chlorate ion have been recently regulated in accordance with EU Directive 2020/2184. Chlorate is a by-product that appears in treated water when sodium hypochlorite is used in breakpoint chlorination.Experiments were carried out at four Hungarian case study areas to determine the optimal strategy for breakpoint chlorination: applying higher chlorine dosages with lower contact times, or lower chlorine dosages with higher contact times. The investigations concluded that the preferable dosing strategy is to use lower chlorine concentrations and longer contact times. This approach reduces chemical demand (cost-effective) and has a neutral effect on THMs formation. it can be concluded that when the raw water contains ammonium ion concentrations above 0.5 mg/l, the use of sodium hypochlorite may raise concerns due to elevated chlorate ion levels in the treated water, particularly during summer. Further research is required to expand the optimization strategy, considering not only ammonium and trihalomethane concentrations but also chlorate concentrations.

Evidence-based framework to use in situ phycocyanin readings for cyanobacterial risk assessment within drinking water treatment plants

A framework is proposed using multi-stream phycocyanin probe readings to manage cyanobacterial risks at the source water and across the drinking water treatment processes.

Study on the nanofiltration membrane fouling control and cleaning efficiency of micro- and nanobubbles

To effectively prevent membrane fouling caused by inorganic scales, which block membrane pores during the nanofiltration process for direct drinking water treatment, the effects of micro/nanobubble introduction on membrane fouling control and membrane cleaning were studied during nanofiltration. The results showed that membrane flux increased 6.3% after micro- and nanobubbles were continuous introduced during the nanofiltration process. Micro- and nanobubbles effectively controlled membrane fouling and had less of an influence on the surface functional groups and polymer layers than did scale inhibitors. The membrane flux of the nanofiltration membrane after cleaning with micro- and nanobubbles decreased gradually with increasing cleaning time, and the membrane flux of the nanofiltration membrane after four rounds of cleaning decreased by 33%. Moreover, micro/nanobubble cleaning did not change the physical or chemical properties of the nanofiltration membrane and delayed the ageing rate of the nanofiltration membrane.

Impact of agricultural activities on the occurrence of N-nitrosamines in an aquatic environment.

N-Nitrosamines, nitroso compounds with strong carcinogenic effects on humans, have been frequently detected in natural waters. In agricultural areas, there is typically a lack of drinking water treatment processes and distribution systems. As a result, residents often consume groundwater as drinking water which may contain N-nitrosamines, necessitating the investigation of the occurrence, sources, and carcinogenic risk of N-nitrosamines within the groundwater of agricultural areas. This study identified eight N-nitrosamines in groundwater and river water in the Jianghan Plain, a famous agricultural region in central China. N-Nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosomorpholine (NMOR), N-nitrosopyrrolidine (NPYR), and N-nitrosodi-n-butylamine (NDBA) were detected in groundwater, with NDMA being the main compound detected (up to 52 ng L-1). Comparable concentrations of these N-nitrosamines were also found in river water. From laboratory experiments, we found a tremendous potential for the formation of N-nitrosamines in groundwater. Principal component analysis and multiple linear regression analysis results showed that the primary sources of N-nitrosamines in groundwater were the uses of nitrogen fertilizers and pesticides carrying specific N-nitrosamines such as NPYR. The average total carcinogenic risk values of detected N-nitrosamines were higher than the acceptable risk level (10-5), suggesting a potential carcinogenic risk of groundwater. Further research is urgently needed to minimize N-nitrosamine levels in the groundwater of agricultural areas, particularly in those where pesticides and fertilizers are heavily used.

Reinforcement learning-based DSS for coagulant and disinfectant dosage selection on drinking water treatment plants

Abstract The treatments to be applied for water purification must be dynamically adaptable to the raw water conditions. Currently, treatments are applied based on standards that are not optimized for the circumstances of each drinking water treatment plant (DWTP), neither for critical events. This paper presents a methodology for the creation of an Artificial Intelligence (AI) decision support system (DSS), encompassing the principal steps of the drinking water treatment processes (coagulation, sedimentation, filtration and disinfection), based on reinforcement learning techniques, that provides suggestions about the most efficient treatments (coagulant and chlorine dosages) for various raw water conditions, including critical events such as heavy rain and saline intrusions. Together with the model, a retraining strategy is included so the DSS adapts itself to the specific circumstances of each different DWTP. The model has been developed and validated in a DWTP replica. Furthermore, the model has been provided to a real DWTP to obtain feedback from experienced staff. The results and evaluation of the model are promising as a first approach on a DSS for drinking water treatments suggestion, although future versions might require more water quality parameters to characterize the raw water.

An XAS study of Hg(II) sorption to Al-based drinking water treatment residuals

Drinking water treatment residuals (DWTRs) are produced from the coagulation and flocculation processes in conventional drinking water treatment. The abundant metal oxide content of these materials resulting from the use of coagulants, like alum and ferric chloride, has driven strong research interest into the reuse of DWTRs as sorptive materials. Using a suite of aluminum-based DWTRs, we provide new insights into Hg(II) sorption mechanisms. Experiments performed at circum-neutral pH show that sorption capacities are related to the amount of organic carbon/matter present in DWTRs. We found that carbon rich samples can scavenge about 9000 mg/kg of Hg, in contrast to 2000 mg/kg for lime based DWTRs. X-ray absorption spectroscopy (XAS) at the Hg L3 edge further characterizes mercury coordination. X-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) results point to a partial association of mercury with sulfur at low mass loadings, transitioning to a full association with oxygen/carbon at higher concentrations of sorbed Hg(II) and in DWTRs with limited sulfur content. These results suggest that sorption of Hg(II) is primarily controlled by the carbon/organic matter fraction of DWTRs, but not by the coagulants.

Identification and quantification of nanoplastics (20–1000 nm) in a drinking water treatment plant using AFM-IR and Pyr-GC/MS

Nanoplastics, owing to their small particle size, pose a significant threat to creatures, deserving heightened attention. Numerous studies have investigated microplastics pollution and their removal efficiency in drinking water treatment plants, none of which have involved nanoplastics due to lacking a suitable analytical method. This study introduced a feasible method of combing AFM-IR and Pyr-GC/MS to identify and quantify nanoplastics (20–1000 nm) for a preliminary understanding of their fate during drinking water treatment processes. Resolving of chemical functional groups and pyrolysis products from AFM-IR and Pyr-GC/MS data demonstrated the presence of PE and PVC nanoplastics in this drinking water treatment plant. The initial influent abundances of PE and PVC nanoplastics were 0.86 μg/L and 137.31 μg/L, with subsequent increase to 4.49 μg/L and 208.64 μg/L in ozonation contact tank unit. Then a gradual decreasing was observed along water process, achieving 98.4% removal of PE nanoplastics and 44.0% removal of PVC nanoplastics, respectively. Although this drinking water treatment plant has exhibited a certain level of nanoplastics removal efficiency, particular attention should be directed to the oxidation unit, which appears to be a significant source of nanoplastics. This study will lay a foundation for revealing nanoplastics pollution in the environment.