Conventional Drinking Water Treatment Plants Research Articles

Enhancing nanoplastics removal by metal ion-catalyzed ozonation

Nanoplastics (NPs), characterized by sizes < 1 µm, are not completely removed in conventional drinking water treatment plants affecting human health. Catalytic ozonation appears as a promising alternative due to its ability to oxidize emerging pollutants by generating hydroxyl radicals with higher removal rate and mineralization than single ozonation. In this work, catalytic ozonation was investigated for the removal of polystyrene nanoplastics (PSNPs) by employing transition metal ion catalysts, Fe3+, Co2+, Ni2+, and Zn2+. The single ozonation of PSNPs, in the absence of catalyst, led to low turbidity reduction (33 %) and low mineralization rate (16 %) even after 2 h reaction time. Nevertheless, the rapid size reduction of PSNPs by >99 % in less than 5 min of ozonation (TOD: 30 mg L−1) was confirmed. This fact could imply a new issue under the ozone disinfection conditions by the formation of smaller-size particles. However, in the presence of Co2+ (1 mM), the highest PSNPs ozonation performance was achieved, decreasing the turbidity up to 65 % and achieving 70 % of mineralization in the same ozonation time. The scavenger experiments with methanol confirmed that direct ozonation and catalyst role were responsible for PSNPs degradation, with the generation of •OH being the most dominant catalytic mechanism. Therefore, although single ozonation at disinfection doses reduced the particle size of PSNPs, the catalytic process demonstrated greater efficacy in the total removal of PSNPs. These results highlight the need to further investigate ozonation of NPs intermediates, and the synergic improvements of catalytic ozonation for their mineralization.

Determination of oxidation rate constant for nodularin‐r, saxitoxin, dc‐saxitoxin, and neo‐saxitoxin with conventional water treatment plant oxidants and advanced oxidation processes

AbstractThe effectiveness of chemical oxidation depends on the type of cyanotoxins present in the water and varies with the water quality parameters. This study investigated four cyanotoxins to understand their reactions with conventional drinking water treatment plant oxidants and with advanced oxidation. Kinetic rate constants between saxitoxin, and two variants (dcSTX and neoSTX), and nodularin‐R with chlorine, monochloramine, permanganate, ozone, and hydroxyl radicals (UV‐H2O2) were developed under different pH and temperature conditions. Nodularin‐R kinetic rate constants were comparable to peer‐reviewed microcystin‐LR rate constants with reaction rates in the order of OH radicals &gt; ozone &gt;&gt; chlorine &gt; permanganate &gt;&gt; monochloramine. The speciation of saxitoxins with pH had a dominant effect on their reaction rates with the listed oxidants. Chlorine was the only oxidant effective for saxitoxins removal. The reaction rates of saxitoxins with OH radicals varied slightly with pH but were around two orders of magnitude less than microcystin‐LR's.

Impact of harmful algal bloom severity on bacterial communities in a full-scale biological filtration system for drinking water treatment

The occurrence of harmful algal blooms (HABs) in freshwater environments has been expanded worldwide with growing frequency and severity. HABs can pose a threat to public water supplies, raising concerns about safety of treated water. Many studies have provided valuable information about the impacts of HABs and management strategies on the early-stage treatment processes (e.g., pre-oxidation and coagulation/flocculation) in conventional drinking water treatment plants (DWTPs). However, the potential effect of HAB-impacted water in the granular media filtration has not been well studied. Biologically-active filters (BAFs), which are used in drinking water treatment and rely largely on bacterial community interactions, have not been examined during HABs in full-scale DWTPs. In this study, we assessed the bacterial community structure of BAFs, functional profiles, assembly processes, and bio-interactions in the community during both severe and mild HABs. Our findings indicate that bacterial diversity in BAFs significantly decreases during severe HABs due to the predominance of bloom-associated bacteria (e.g., Spingopyxis, Porphyrobacter, and Sphingomonas). The excitation-emission matrix combined with parallel factor analysis (EEM-PARAFAC) confirmed that filter influent affected by the severe HAB contained a higher portion of protein-like substances than filter influent samples during a mild bloom. In addition, BAF community functions showed increases in metabolisms associated with intracellular algal organic matter (AOM), such as lipids and amino acids, during severe HABs. Further ecological process and network analyses revealed that severe HAB, accompanied by the abundance of bloom-associated taxa and increased nutrient availability, led to not only strong stochastic processes in the assembly process, but also a bacterial community with lower complexity in BAFs. Overall, this study provides deeper insights into BAF bacterial community structure, function, and assembly in response to HABs.

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.

Fate of Cryptosporidium and Giardia through conventional and compact drinking water treatment plants

Over the past three decades, a notable rise in the occurrence of enteric protozoan pathogens, especially Giardia and Cryptosporidium spp., in drinking water sources has been observed. This rise could be attributed not only to an actual increase in water contamination but also to improvements in detection methods. These waterborne pathogens have played a pivotal role in disease outbreaks and the overall escalation of disease rates in both developed and developing nations worldwide. Consequently, the control of waterborne diseases has become a vital component of public health policies and a primary objective of drinking water treatment plants (DWTPs). Limited studies applied real-time PCR (qPCR) and/or immunofluorescence assay (IFA) for monitoring Giardia and Cryptosporidium spp., particularly in developing countries like Egypt. Water samples from two conventional drinking water treatment plants and two compact units (CUs) were analyzed using both IFA and qPCR methods to detect Giardia and Cryptosporidium. Using qPCR and IFA, the conventional DWTPs showed complete removal of Giardia and Cryptosporidium, whereas Mansheyat Alqanater and Niklah CUs achieved only partial removal. Specifically, Cryptosporidium gene copies removal rates were 33.33% and 60% for Mansheyat Alqanater and Niklah CUs, respectively. Niklah CU also removed 50% of Giardia gene copies, but no Giardia gene copies were removed by Mansheyat Alqanater CU. Using IFA, both Mansheyat Alqanater and Niklah CUs showed a similar removal rate of 50% for Giardia cysts. Additionally, Niklah CU achieved a 50% removal of Cryptosporidium oocysts, whereas Mansheyat Alqanater CU did not show any removal of Cryptosporidium oocysts. Conventional DWTPs were more effective than CUs in removing enteric protozoa. The contamination of drinking water by enteric pathogenic protozoa remains a significant issue globally, leading to increased disease rates. Infectious disease surveillance in drinking water is an important epidemiological tool to monitor the health of a population.

A case study of comparative techno-economic and life cycle assessment of tap water versus household reverse osmosis-based drinking water systems in a North Indian city

Abstract Household reverse osmosis (RO)-based water purifiers have gained popularity in India due to concerns about the quality of tap water. However, the widespread adoption of these systems has significant impacts on water pricing and the environment. The objective of this study was to assess the techno-economic performance and life cycle assessment (LCA) of household RO-based water purifiers in Srinagar city of North India. Our results demonstrate that household ROs reduce the concentration of important dietary minerals such as fluoride and magnesium in drinking water by 50%. In addition, the average total water cost from a household RO is three to four times more than what is being paid for tap water. Two different scenarios were compared in LCA. The first scenario was safe drinking water from a conventional drinking water treatment plant (scenario 1), while the second scenario was water from a household RO system (scenario 2). The results showed that the environmental impacts of abiotic depletion, acidification of water bodies, eutrophication, global warming and ozone depletion in scenario 2 were higher than in scenario 1. The findings infer that water utilities should encourage citizens to rely on conventional tap water as a cheaper and environmentally friendly option compared to household ROs.

Contamination of neonicotinoid insecticides in source water and their fate during drinking water treatment in the Dongguan section of the Pearl River

Neonicotinoid insecticides (NEOs) as well as their metabolites are highly mobile on the subsurface and can potentially contaminate drinking water sources; however, their pollution status and fate in the drinking water system remains ambiguous. In this study, six parent NEOs and two characteristic metabolites were measured in drinking water source protection area (source water, n = 52) and two related drinking water treatment plants (DWTPs) (n = 88) located in the Dongguan section of the Pearl River. The ubiquitous of NEOs was observed in source water with the mean concentration of total NEOs (ΣNEOs) at 240 ng/L. Although advanced DWTP (A-DWTP; range: 26 % to 100 %) showed better removals of ΣNEOs and all individual NEOs rather than those in conventional DWTP (C-DWTP; range: −53 % to 28 %), the removals were still low for acetamiprid (ACE, 26 %), thiacloprid (THD, 59 %), thiamethoxam (THM, 56 %) and N-desmethyl-acetamiprid (N-dm-ACE, 45 %) in A-DWTP. Removal rates were positive in chlorination (48 %), final stage of sedimentation (F-Sed, 24 %), and granular activated carbon (GAC) filter effluent (19 %) in A-DWTP. It worthy to note that ΣNEOs has high negative removal rates at the start stage of sedimentation (S-Sed, −83 %), middle stage of sedimentation (M-Sed, −47 %), and sand filter effluent (−42 %) water in C-DWTP, which resulted in negative removals of ΣNEOs (−9.6 %), imidacloprid (IMI, −22 %), clothianidin (CLO, −37 %), flupyradifurone (FLU, −76 %), and N-dm-ACE (−29 %) in C-DWTP. Residual levels of NEOs were high in source water, and their low or negative removals in DWTPs should be highly concerning. Results would fill the existing knowledge gap of NEOs in aquatic environment and provide a scientific dataset for policy-making on pollution control and environmental protection.

Performance of Conventional Drinking Water Treatment Plants in Removing Microplastics in East Java, Indonesia

Performance of Conventional Drinking Water Treatment Plants in Removing Microplastics in East Java, Indonesia

Contamination and removal efficiency of microplastics and synthetic fibres in a conventional drinking water treatment plant in Geneva, Switzerland

Although it is known that freshwater resources are contaminated with microplastics (MPs), still limited information is known about the efficiency of large drinking water treatment plants (DWTP) to remove microplastics. Moreover, reported concentrations of MPs in drinking water variates from some units to thousands of units per litre and the sampling volumes used for MPs analysis are generally heterogeneous and limited. The present study evaluates the removal of MPs and synthetic fibres in the main DWTP of Geneva, Switzerland, by considering large sampling volumes at different time intervals. Furthermore, contrary to other studies, this DWTP does not count with a clarification process before sand filtration and coagulated water is sent directly to sand filtration. In this study a distinction is made between microplastics as fragments, films, pellets, and synthetic fibres. Raw water and effluents of each filtering mass (sand and activated carbon filtration) are analysed for the presence of MPs and synthetic fibres with sizes ≥63 μm using infrared spectroscopy. Concentrations of MPs in raw water range from 25.7 to 55.6 MPs/m3 and in treated water from 0 to 4 MPs/m3, respectively. Results show that 70 % of MPs are retained during sand filtration and total removal is equal to 97 % in treated water after activated carbon filtration. Concentration of identified synthetic fibres is low (average value of 2 synthetic fibres/m3) and constant in all steps of water treatment. Chemical composition of microplastics and synthetic fibres is found more heterogeneous in raw water than after sand filtration and activated carbon filtration, indicating the persistence of some types of plastics (like polyethylene and polyethylene terephthalate) in water treatment processes. Heterogeneities in MP concentrations are observed from one sampling campaign to another, indicating significant variations of MP concentrations in raw water.

Microplastic Removal from Drinking Water Using Point-of-Use Devices.

The occurrence of microplastics in drinking water has drawn increasing attention due to their ubiquity and unresolved implications regarding human health. Despite achieving high reduction efficiencies (70 to >90%) at conventional drinking water treatment plants (DWTPs), microplastics remain. Since human consumption represents a small portion of typical household water use, point-of-use (POU) water treatment devices may provide the additional removal of microplastics (MPs) prior to consumption. The primary objective of this study was to evaluate the performance of commonly used pour-through POU devices, including those that utilize combinations of granular activated carbon (GAC), ion exchange (IX), and microfiltration (MF), with respect to MP removal. Treated drinking water was spiked with polyethylene terephthalate (PET) and polyvinyl chloride (PVC) fragments, along with nylon fibers representing a range of particle sizes (30-1000 µm) at concentrations of 36-64 particles/L. Samples were collected from each POU device following 25, 50, 75, 100 and 125% increases in the manufacturer's rated treatment capacity, and subsequently analyzed via microscopy to determine their removal efficiency. Two POU devices that incorporate MF technologies exhibited 78-86% and 94-100% removal values for PVC and PET fragments, respectively, whereas one device that only incorporates GAC and IX resulted in a greater number of particles in its effluent when compared to the influent. When comparing the two devices that incorporate membranes, the device with the smaller nominal pore size (0.2 µm vs. ≥1 µm) exhibited the best performance. These findings suggest that POU devices that incorporate physical treatment barriers, including membrane filtration, may be optimal for MP removal (if desired) from drinking water.

Risk Analysis and Evaluation of the Current Situation in Terms of Work Safety in The Drinking Water Treatment Plant

Water treatment plants are the most important facilities used to provide potable water to settlements and clean water. These facilities raise water quality to the desired standards physically, bacteriologically, and chemically. A conventional drinking water treatment plant consists of aeration, coagulation, flocculation, settling, filtration and disinfection units. Each of these units has its hazards. For this reason, if adequate safety precautions are not taken, the possibility of plant employees being, exposed to these hazards will be quite high. Risks arise as a result of exposure to hazards in every workplace. It is important to analyze these risks and determine the precautionary priorities and to ensure health and safety in the workplace. In this study, the hazards that employees may be exposed to in a drinking water treatment plant in the Eastern Black Sea region were determined. All the units of the facility were examined and all risks that would affect the employees and the working order of the facility were calculated with the matrix method. After the risk levels have been determined, in the study the risks named as unacceptable and as to be considered are presented and the precautions to be taken in the facility are listed to be protected from these risks. As a result of the study, the importance of personal protection measures and safety culture, especially collective protection measures, was emphasized for the employees in such workplaces containing complex units.

Estimation of sludge production in conventional drinking water treatment plants trough prediction models

El tratamiento de agua para consumo humano en plantas de tratamiento de agua potable (PTAP) convencionales, genera lodos que se retienen principalmente en la etapa de sedimentación y para hacer un manejo adecuado es importante conocer las cantidades producidas. Para aportar a este fin, en este estudio se evaluaron diferentes modelos empíricos (AFEE, Cornwell &amp; Koppers, Coşkun, CETESB, AWWA y Kawamura) y estocásticos (ARIMA) para la predicción de la producción de lodos de una PTAP convencional que utiliza sulfato de aluminio como coagulante. Entre los modelos empíricos, los tres primeros presentaron un mejor ajuste frente a los datos observados; sin embargo, el estocástico ARIMA (0,1,2) fue el de mejor predicción con una diferencia de 1.51% entre el valor pronosticado y el observado (2173,65 ± 549 vs 2207 Kg / día de lodos en base seca), lo que demuestra su aplicabilidad para estimar la producción de lodos.

NaClO-based rapid sand filter in treating manganese-containing surface water: Fast ripening and mechanism

Recently, seasonal manganese contamination in the surface water is capturing ever-increasing attention and has posed significant challenges to the safety of water supply in the conventional drinking water treatment plants. This study aimed to develop new strategies to enhance the manganese removal by the sand filter. The synergistic effects of filter material type, filter layer thickness, filtration rate, and NaClO addition on the manganese removal performance, were systematically investigated. The results indicated that modified zeolite exerted the highest adsorption capacity (5.200 mg/g) for manganese. Introducing the NaClO oxidation would effectively improve the manganese removal efficiency (from 32 % to 97 %) by the modified zeolite filter compared to the control system at the filtration rate of 8 m/h, owing to the fast formation of catalytic oxidation capability. Accordingly, the effective layer thickness of modified zeolite can be shortened from 100 cm to 10–20 cm to engineer a double-layer filter consisting of both a thin modified zeolite layer and a thick natural quartz sand layer. Besides, NaClO involvement would neutralize the adverse effects of manganese removal caused by the filtration rate increase, and facilitate the formation of auto-catalytic manganese oxides (MnOx) with rough, heterogeneous, and porous surface morphology, as well as numerous tremella-like and sponge-type structures, which was related to the fast removal of manganese. These findings are full of significance in developing simple, practical, and cost-effective strategies for seasonal manganese contamination.

Assessing the efficiency of drinking water treatment plant and the impact of broken distribution systems on water quality of Wukari-Ibi plant

Water treatment is essential in the provision of potable drinking water to communities. However, studies have shown that many local conventional drinking water treatment plants in Nigeria are ineffective in removing contaminants. This study evaluated the efficiency of drinking water from Wukari-Ibi plant by assessing water samples before and after treatment and comparing results to national and international drinking water standards. Forty water samples were collected and selected physical and biological parameters were determined according to standard laboratory procedures. The results indicated that after treatment, turbidity (6.74 NTU) and coliform count (17 cfu/100 mL) were still significantly greater than standard guidelines, which suggest that the treatment plant is unable to reduce the concentration of these contaminants to a safe level for consumption. Furthermore, assessing water at consumer taps indicated that broken distribution system is likely serving as a potential pathway for contamination. The plant removal efficiency of colour, turbidity, Total Dissolved Solids, hardness, and coliform count was computed as 74.7%, 66.57%, 32.58%, 30.11%, and 59.88% respectively. Overall, the removal efficiency was 52.77% which is considered unacceptable for the supply of potable drinking water. The study concludes that cost and poor skilled personnel are the major factors in the inefficient treatment and therefore we suggest a low-cost treatment using activated carbon from locally sourced plants to be incorporated for effective removal of contaminants. There is also a need for government to invest in infrastructure and equipment so as to upgrade the treatment plant.

Optimization of polypropylene microplastics removal using conventional coagulants in drinking water treatment plants via response surface methodology.

The ubiquitous presence of microplastics (MPs) in aquatic environments has been studied widely. Due to toxicological impacts of MPs and associated contaminants, it is crucial to understand the performance of MPs removal in drinking water treatment plants (DWTPs). Few studies have investigated removal characteristics of MPs via coagulation/flocculation processes, yet removal characterization of polypropylene microplastics (PPMPs) in this process is poorly understood. This study aims to optimize coagulation of virgin PPMPs in conventional DWTPs. In this study, samples were synthesized through response surface methodology (RSM), polyaluminium chloride (PACl) was applied as a conventional coagulant to remove PPMPs in the coagulation/flocculation process, which has the least density among common polymers and is one of the most abundant manufactured polymers worldwide. A particle size analyzer (PSA) was used to measure floc size at different pH levels. Additionally, a zeta potential analyzer was used to measure stability of the flocs at different pH. Base on the experimental range in Design-Expert, results revealed that the optimum removal rate was predicted to be at pH 9, PACl concentration of 200ppm, polyacrylamide (PAM) concentration of 21ppm, and PPMPs size of d < 0.25mm. According to the predicted optimum condition, actual and predicted removal rates were 18.00 ± 1.43% and 19.69%, respectively. According to this study, PACl is not capable of efficiently removing virgin PPMPs in DWTPs, thereby exposing humans to eco-toxicological impacts of PPMPs through tap water.

Endotoxin removal efficiency in conventional drinking water treatment plants, a case study in Egypt

The present study determines the endotoxin removal efficiency of drinking water treatment plants (DWTPs) in Egypt, as examples of conventional treatment methods used in developing countries. The total endotoxin in source water (Nile River) of these DWTPs ranged from 57 to 187 EU∙mL−1, depending on the location of treatment plants. Coagulation/ flocculation/sedimentation (C/F/S) after chlorine pre-oxidation removed bound endotoxins by 76.1–85.5%, but caused cell lysis and increased free endotoxins by 28.2–33.3% of those detected in raw waters. Rapid sand filtration had not significant effect on free endotoxins, but reduced bound endotoxins by 23–33.3%. Final chlorine disinfection also reduced bound endotoxins to levels around 1 EU/mL, accompanied by an increase in free endotoxins (37–112 EU∙mL−1) in finished waters. Simultaneously, final chlorine disinfection removed all heterotrophic bacteria, with low cyanobacterial cell numbers (348–2 450 cells∙mL−1) detected in finished waters. Overall, conventional treatment processes at these DWTPs could removal substantial amounts of bound endotoxins and bacterial cells, but increase free endotoxins through cell lysis induced by pre-oxidation and final chlorine disinfection. The study suggests that conventional processes at DWTPs should be optimized and upgraded to improve their performance in endotoxin removal and ensure safe distribution of treated water to consumers.

Tap water as a natural vehicle for microorganisms shaping the human gut microbiome.

Fresh potable water is an indispensable drink which humans consume daily in substantial amounts. Nonetheless, very little is known about the composition of the microbial community inhabiting drinking water or its impact on our gut microbiota. In the current study, an exhaustive shotgun metagenomics analysis of the tap water microbiome highlighted the occurrence of a highly genetic biodiversity of the microbial communities residing in fresh water and the existence of a conserved core tap water microbiota largely represented by novel microbial species, representing microbial dark matter. Furthermore, genome reconstruction of this microbial dark matter from water samples unveiled homologous sequences present in the faecal microbiome of humans from various geographical locations. Accordingly, investigation of the faecal microbiota content of a subject that daily consumed tap water for 3 years provides proof for horizontal transmission and colonization of water bacteria in the human gut.

Contamination and Removal Efficiency of Microplastics and Synthetic Fibres in a Conventional Drinking Water Treatment Plant

Microplastics have been detected all around the globe in freshwaters which are frequently used to produce drinking water. Therefore, the contamination of raw water with microplastics that supplies drinking water treatment plants, and their removal efficiency is raising more concern and interest. In the present study, we evaluated the microplastic contamination in a conventional drinking water treatment plant (Geneva, Switzerland) and the contribution of coagulation on the efficiency of the filtration systems (sand and activated carbon filtrations) in the removal efficiency of microplastics (MPs) and synthetic fibres. This work was performed in a pilot station that replicates the main drinking water treatment process. Raw water and effluents of each filtering processes were analysed for the presence of MPs and synthetic fibres with sizes ≥ 63 μm using infrared spectroscopy. The contamination of MPs in raw water and in drinking water ranged from 19.5 to 143.5 MPs/m3 and from 0 to 8 MPs/m3 (in presence and absence of coagulant), respectively. On the other hand, concentration of synthetic fibres ranged from 7.7 to 23.8 synthetic fibres/m3 in raw water and from 0 to 3 synthetic fibres/m3 in drinking water. Results show that on average 89% of microplastics and 81% of synthetic fibres (≥63 μm) are retained in water treatment in absence of coagulant. Better final removal efficiency of microplastics (97%) and synthetic fibres (96%) was observed in drinking water with coagulation treatment. The chemical composition of microplastics and synthetic fibres is found more heterogeneous in raw water than after sand filtration and activated carbon filtration.

Occurrence of titanium dioxide nanoparticle in Taihu Lake (China) and its removal at a full-scale drinking water treatment plant.

The occurrence of titanium dioxide nanoparticle (TNP), an emerging contaminant, in Taihu Lake of China was investigated. Ti was present at a concentration of 224 ± 59 μg/L in the water samples collected from a water source in east Taihu Lake. Approximately 0.19% of the Ti-containing matter was at the nano-scale. Scanning Electron Microscope analysis verified the existence of Ti-containing components, such as TiOx and FeTiOx. Furthermore, Ti K-edge X-ray absorption near-edge structure spectroscopy was used to detect the phase composition of nano-scaled Ti-containing matter. The spectra showed the three characteristic peaks of TiO2 in the samples, suggesting the occurrence of TNP in Taihu Lake. A least-squares linear combination fitting analysis indicated that the TNP concentration in the water source was ~0.77 μg/L in water and ~0.85 μg/g-dry in sediment. The removal performance of the TNP at a full-scale conventional drinking water treatment plant indicated that ~61% of TNP was removed via coagulation/sediment, sand filtration, and disinfection/clear water reservoir. The coagulation/sediment process accounted for approximately 70% of the total removed TNP. The finished water contained ~ 0.30 μg/L TNP. This study is the first that reported the presence and transport of TNP in a full-scale drinking water treatment system.

Conventional and biological treatment for the removal of microplastics from drinking water

This study examines the removal of microplastics and other anthropogenic particles (>10 μm) from surface water by a full-scale conventional drinking water treatment plant. The treatment process is composed of coagulation with aluminum hydroxide, flocculation, anthracite-sand filtration, and chlorination. Samples were also collected from pilot-scale biological filters consisting of anthracite-sand or granular activated carbon (GAC) media operated with or without pre-ozonation and at a range of different empty-bed contact times (EBCTs). Particles in 10 L water samples collected in duplicate using a fully enclosed sampling apparatus were separated using sieves with 500 μm, 300 μm, 125 μm, and 45 μm openings followed by filtration through 10 μm polycarbonate filters. Particles were counted using stereomicroscopy and characterized using μ-Raman spectroscopy. Full-scale conventional treatment removed 52 % of anthropogenic particles when comparing raw (42 ± 18 particles/L) and finished water (20 ± 8 particles/L). Coagulation, flocculation, and sedimentation accounted for the highest removal (70 %) of any individual unit process. Overall removal was reduced to 52 %, the difference being attributed to airborne particle deposition that occurred while water was detained in a clearwell (exposed to atmosphere via ventilation) that was used to achieve the required contact time for disinfection. The majority of the particles (>80 %) were identified as fibers 10–45 μm; microplastics were predominantly composed of polyester while the non-plastic anthropogenic particles were primarily cellulose. None of the pilot filter configurations examined resulted in significantly fewer microplastics when compared to full-scale conventional filtration. This study illustrates that the removal efficiency of conventional treatment may be limited when considering microfibers <45 μm in size.