Municipal Water Treatment Plant Research Articles

Deciphering the degradation of sulfonamides by UV/chlorination in aqueous solution: kinetics, reaction pathways, and toxicological evolution

UV/Cl is a cost-effective process and is often used in municipal water treatment plants as well as in industrial applications. UV/Cl method is found highly effective in degrading contaminants, including pathogens, The conventional methods for water treatment have been proven inefficient for the complete elimination of pollutants and generate harmful by-products in the environment. This study evaluated the efficacy of three different treatment methods, chlorination alone, UV photolysis, and UV/Cl, for the degradation of sulfonamides (SAs) in water. The results highlighted that UV/Cl treatment was an efficient method for enhancing the degradation of sulfisoxazole (SFX), sulfadimethoxine (SAT), and sulfaguanidine (SG), with substrates degrading in 5, 6.5, and 4 min. The study also investigated the reactive species generated in the UV/Cl system and found that ·OH was the species responsible for the elimination of SFX. Additionally, the study explored the intermediate products generated during the degradation of SFX under the UV/Cl system, identifying VI distinct degradation pathways. The presence of ·OH radicals significantly enhanced the degradation of SFX, while some chlorine species also contributed to the degradation. The study predicted the toxicity of degradation products from the UV/Cl system using the ECOSAR (Ecological Structure Activity Relationships) program and found that the final degradation products of SFX were non-toxic, but concerns were raised about acute toxicity.

Applying Microbial Source Tracking Techniques for Identification of Pathways of Faecal Pollution from Water Sources to Point of Use in Vhembe District, South Africa

A safe water supply is a necessity, but it remains one of the backlogs of services rendered in rural areas of developing countries. This leads to vulnerable communities using water from available sources that is unsafe as it is contaminated with faecal matter. Microbial source tracking (MST) methods are gold-standard techniques that detect the exact sources of faecal contamination. This study, therefore, tracked and identified the exact sources of faecal contamination from the catchment to the point of use in rural areas of Vhembe District Municipality. Collected water samples (n = 1048) were concentrated by membrane filtration for the enumeration and detection of E. coli, followed by DNA extraction. The extracted DNA was subjected to a quantitative polymerase chain reaction (qPCR) to track target host-specific Bacteroidales genetic markers from the water source to the point of use. Rivers and dams exhibited maximum E. coli counts of up to 90 CFU/100 mL during the wet season and up to 50 CFU/100 mL during the dry season. Due to the effective treatment of these water sources, no E. coli bacteria were detected in any of the sampled municipal drinking water treatment plants at the point of treatment, while this indicator bacterium was detected at the point of use (households), with a maximum of 4 CFU/100 mL recorded during both the wet and dry seasons. Overall, the most prevalent MST marker exhibited during the wet season was BacCan (dog-associated, 6.87%), followed by BacCow (cow-associated, 5.53%), while Pig-2-Bac (pig-associated, 2.48%) was the least prevalent. The most prevalent marker exhibited during the dry season was BacCan (5.34%), followed by BacCow, with Pig-2-Bac (1.72%) being the least prevalent. A positive correlation (r = 0.31, p = 0.001) was established between the presence of the MST markers and detected E. coli from water sources to the point of use. The knowledge of the faecal contamination attributes in both public and domestic domains will assist in developing prevention and control strategies.

Taxonomic report of filamentous fungi presents in sewage waste sludge with biotechnologi-cal potential

There is few information regarding the identification of filamentous fungi present in sewage sludge, the importance of these microorganisms lies in the potential use they have in the food, pharmaceutical and agri-environmental industries as they are beneficial in the remediation of water, sludge and soil contaminated by Heavy metals and hydrocarbons also contribute to the adsorption of nutrients by crops. The use of residual sludge once decontaminated by these microorganisms can be used in agriculture as soil structure improvers, organic fertilizers and as an amendment to prevent soil erosion. The objective of this research was to characterize and identify fast and medium-growing filamentous fungi from sewage sludge. The residual sludge was collected directly from the thickness of the municipal water treatment plant of Cd. Victoria, Tamaulipas, Mexico. Subsequently, the fungi were isolated on agar plates and identified using morphological characters of the colonies and by PCR and diana sequences. The species identified were: Trichoderma longibrachiatum, Aspergillus terreus, Tylopilus porphyrosporus and Aspergillus fumigatus. Being the first report for Mexico of fungal species that grow in residual sludge from water treatment plants. The molecular characterization of the species of filamentous fungi found in sewage sludge will allow progress in research focused on knowing the advantages and biological and chemical mechanisms of these microorganisms for the development of biotechnological processes and products, with high agricultural potential and environmental.

How to Pump Wastewater Treatment Chemicals

Municipal water treatment plants are demanding environments for chemical metering pumps

Electrocatalytic detection of Hg(II) using a platinum electrode modified with composite film of cobalt(II) phthalocyanine tetra-substituted with 1-(methoxymethyl)-benzotriazole groups and co-electropolymerized polypyrrole

The presence of mercury adversely affects the daily lives of humankind due to its acute toxicity and environmental persistence. Therefore, the development of cost-effective smart materials which can allow the real time, ultrasensitive and discriminatory monitoring of mercury concentrations in industrial and municipal water treatment plants is an imperative. It is foreseen that this proposed water quality assurance measure will be of utmost importance to identify the culprits for the wide prevalence of this heavy metal ion in the environment. Herein, a platinum electrode (Pt) was modified via the simultaneous electropolymerization of polypyrrole (PPy) and the co-electrodeposition of tetra-[4-((1H-benzotriazole)methoxy)phthalocyaninato]cobalt(II) (CoPc-Bzt, 2, (Btz = benzotriazole)). The complementary electrode modification processes were performed in a 1:1 (v: v) DMF: acetonitrile containing 1 M tetrabutylammonium hexafluorophosphate electrolyte solution over 20 cycles using cyclic voltammetry to afford the chemically modified electrode (CME), Pt|PPy/2. Differential pulse anodic stripping voltammetry (DPASV) was used to detect Hg(II) ions using the CME within a 10 µM to 100 µM linear range while calculated limits of detection and quantification (LOD and LOQ) were determined as 3.11 and 10.00 µM, respectively. The analytical performance of the CME rendered a statistically accepted percentage recovery (97.4%) whereas that of Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES) is 112.3%.

Comparison of 17β-estradiol, bisphenol-A and caffeine concentration levels before and after the water treatment plant.

This article compares the concentration levels of 17β-estradiol (E2), bisphenol-A (BPA) and caffeine (CAF) in the Sinos River, Brazil, which is a source of drinking water and the presence of contaminants after the conventional treatment in a municipal water treatment plant (WTP). A total of nine sampling campaigns were carried out, with sample collection in the Sinos River, upstream and downstream of the WTP, in addition to a drinking water sample (DW). The samples were extracted with solid phase extraction (SPE) and the concentration by liquid chromatography coupled to mass spectrometry (LC-MS). The maximum concentration in the Sinos River was 6,127.99 ng·L-1 for E2, 3,294.63 ng·L-1 for BPA and 1,221.95 ng·L-1 for CAF. In drinking water, the concentration range of E2, BPA and CAF was from less than the Detection Limit (DL) up to 437.50 ng·L-1, <DL up to 2,573.34 ng·L-1 and <DL up to 832.30 ng·L-1, respectively. In conclusion, the concentrations of these pollutants present in the Sinos River are high, which may represent a negative environmental impact on this water source. Drinking water indicates the need for a new treatment process that could promote the removal of these compounds.

LED-irradiated photo-Fenton process on pollutant removal: outcomes, trends, and limitations.

This manuscript critically reviews the state of the art on the application of photo-Fenton processes irradiated by light-emitting diode arrays (LED) with a focus on the removal of contaminants of emerging concern (CEC) from aqueous matrices. LEDs are clean, low-cost radiation sources with longer lifespan compared to mercury lamps. This study covers the influence of LED sources, wavelengths, and dose upon CEC removal, and the potential for disinfection, abatement of antibiotic-resistant bacteria (ARB), and genes (ARG). The bibliographic search was performed in Scopus database using keyword combinations and resulted in a portfolio containing 52 relevant articles published between 2010-2023. According to reviewed papers, LED photoreactor design has evolved in the past decade aiming to improve CEC degradation in aqueous matrices while reducing construction and operation costs, and energy consumption. Among several reactors (annular, fluidized bed, parallel plate, wireless, pathway systems, and microreactor) surveyed for their performance and scalability, LED chips and strips are particularly suitable for application due to their wide emission angle (≈120°) and small size (mm2), which allow for, respectively, efficient illumination coverage and flexible arrangement and design. LED microreactors are very efficient in the degradation of contaminants and scalable with reduced area requirements. Although most studies were performed in synthetic solutions and at laboratory scale, the externally LED irradiated cylindrical reactor was successful for application in full-scale municipal water treatment plants. Future studies should focus on evaluating CEC removal in wastewater using scalable devices for continuous operation of solar photo-Fenton at night.

An Experimental Study on optimizing Wastewater Filtration through Conventional and Capped Rapid Sand Filter

Abstract: Rapid sand filtration is a widely adopted technique for purifying water in various applications, ranging from municipal water treatment plants to industrial processes. This abstract provides an overview of the rapid sand filter, highlighting its key principles, advantages, and applications. The rapid sand filter is a gravity-driven filtration system that utilizes a bed of sand as the primary filtration medium. Water flows through the sand bed under gravity or low-pressure conditions, undergoing physical andbiological processes that remove suspended solids,pathogens, and other impurities. The sand bed acts as a physical barrier, trapping and retaining particles while allowing the passage of clean water. This abstract discusses the key factors influencing the efficiency of rapid sand filters, including sand grain size, uniformity, and depth. The control of filtration rate, backwashing frequency, and the use of coagulants or flocculants are also addressed, as they significantly impact the filter's performance. Proper maintenance and monitoring are crucial to ensure optimal filter operation and prevent clogging or biofilm formation. Rapid sand filtration offers several advantages, such as simplicity, cost-effectiveness, and ease of operation. It is capable of achieving high removal efficiencies for suspended solids, turbidity, and certain pathogens, making itsuitable for a wide range of water treatment applications

Impacts of hydraulic fracturing wastewater from oil and gas industries on drinking water: Quantification of 69 disinfection by-products and calculated toxicity

Oil and gas production generates large amounts of brine wastewater called “produced water” with various geogenic and synthetic contaminants. These brines are generally used in hydraulic fracturing operations to stimulate production. They are characterized by elevated halide levels, particularly geogenic bromide and iodide. Such salt concentrations in produced water may be as high as thousands of mg/L of bromide and tens of mg/L of iodide. Large volumes of produced water are stored, transported, reused in production operations, and ultimately disposed of by deep well injection into saline aquifers. Improper disposal may potentially contaminate shallow freshwater aquifers and impact drinking water sources. Because conventional produced water treatment typically does not remove halides, produced water contamination of groundwater aquifers may cause the formation of brominated and iodinated disinfection by-products (I-DBPs) at municipal water treatment plants. These compounds are of interest because of their higher toxicity relative to their chlorinated counterparts. This study reports a comprehensive analysis of 69 regulated and priority unregulated DBPs in simulated drinking waters fortified with 1 % (v/v) oil and gas wastewater. Impacted waters produced 1.3×–5× higher levels of total DBPs compared to river water after chlorination and chloramination. Individual DBP levels ranged from (<0.1–122 μg/L). Overall, chlorinated waters formed highest levels, including trihalomethanes that would exceed the U.S. EPA regulatory limit of 80 μg/L. Chloraminated waters had more I-DBP formation and highest levels of haloacetamides (23 μg/L) in impacted water. Calculated cytotoxicity and genotoxicity were higher for impacted waters treated with chlorine and chloramine than corresponding treated river waters. Chloraminated impacted waters had the highest calculated cytotoxicity, likely due to higher levels of more toxic I-DBPs and haloacetamides. These findings demonstrate that oil and gas wastewater if discharged to surface waters could adversely impact downstream drinking water supplies and potentially affect public health.

Spatiotemporal distribution of opportunistic pathogens and microbial community in centralized rural drinking water: One year survey in China

Centralized water supply in rural areas, supported by small waterworks (small-central mode) and by municipal water treatment plants (urban-extension mode), is an important guarantee to implement the Rural Revitalization Strategy Plan (2018–2022) in China. Opportunistic pathogens (OPs) could not be evaluated by the national drinking water sanitation standards in China (GB 5749–2022), posing potential microbial risks in rural drinking water. In this study, the spatiotemporal distribution of OPs, microbial community and the associated functional composition under two central water supply modes were investigated by molecular approaches. The results indicated that OPs were widely presented in the rural drinking water regardless of water supply modes, and were more abundant than those in the urban tap water. The insufficient residual chlorine and higher turbidity triggered more microbial proliferation, posing a seasonal variation of OPs gene copy numbers and bacterial community compositions. In warm seasons of summer and autumn, the gene copies of E. coli, M. avium, Pseudomonas spp. and the amoeba host Acanthamoeba spp. achieved up to 4.92, 3.94, 6.75 and 3.74 log10 (gene copies/mL), respectively. Potential functional prediction indicated higher relative abundance of pathogenic genes and infectious risks associated with the rural drinking water under small-central water supply mode. This one-year survey of the spatiotemporal distribution of OPs and microbial community provided scientific insights into microbial safety of rural drinking water, prompting attention on small-central water supply mode against OPs risks.

Application of tannin-based coagulant for high-range turbidity surface water clarification

Abstract This study aimed to evaluate the performance of a tannin-based coagulant in clarifying drinking water from a high-range turbidity river and characterizing the sludge. Tanfloc MTH product was selected for this investigation. The study site was surface water located in southern Brazil (Caveiras River, Brazil). Samples were collected just before the Parshall flume in the municipal water treatment plant in Lages (Brazil) for nine months, at least once a week. Jar testing evaluated turbidity removal, alkalinity consumption, optimal coagulant dosage, and settling velocity. After flocculation and settling, the sludge generated from the jar test was submitted to metal and thermogravimetric analyses. The use of tannin reduced the average water turbidity from 26.1 ± 56.1 to 0.94 ± 0.26 NTU, apparent color from 145 ± 190 to 3 ± 3 Pt-Co, and there was no variation in the pH. Additionally, the settling velocity of the flocs reached a maximum turbidity removal at 3.5 cm·min−1. Furthermore, the metal concentrations in the sludge showed a majority of aluminum and iron, and thermogravimetric analysis revealed 64% weight loss. In conclusion, Tanfloc presented the potential to be used in surface water clarification from the Caveiras river, and the extensive turbidity range observed during this study did not affect the operational stability.

Full‐scale application of an electrochemical disinfection solution in a municipal drinking water treatment plant

AbstractFew studies employ electrochemical technology for urban water disinfection. This paper presents the replacement of a Cl2 gas system by an on‐site chlorine generation system (electrochemical disinfectant solution, EDS) and application at a water treatment plant. The study compares the Cl2 gas and EDS systems over 36 months, with 18 months for Cl2 gas and, after the implementation, 18 months for the EDS system (12‐month dry season and 6‐month wet season). Turbidity, residual Cl2, pH, total and faecal coliforms and DBPs were monitored. Turbidity was within legal limits and DBPs below both legal limits and limits of detection. For Cl2 gas, residual Cl2 suffered a decrease in wet and dry periods. However, the EDS maintained residual Cl2 to the network tips without significant variations, with operational costs reduced by ~41%. The study demonstrates that on‐site Cl2 generation can be employed for water disinfection for large urban areas with considerable economic and technical advantages.

Evaluation of the effects of water quality on drinking preferences of heifer calves

Drinking water quality requirements focus mainly on removing hazardous substances from the water supply, making it safe to drink and appropriate for livestock use. However, there is a concern that high mineral content in water may affect the drinking behavior of heifer calves, which may affect health and performance. In South Dakota, the primary water sources for agricultural use are surface or groundwater. Water quality varies between different regions of the state; in the eastern part of the state, the water is classified as “hard water” and calcium is the primary mineral found in the water. Our objective was to determine the water intake and drinking preference of heifer calves offered water treated with a reverse osmosis system (ROW), water treated by a municipal city water treatment plant (TW), and local untreated well water (UWW). Six Holstein heifer calves (100 ± 6.5 d of age; 137 ± 5.9 kg of body weight) were used in a sequential elimination study. The calves were kept in individual pens (1.5 × 3 m) and fed similar pellet and grass hay rations. Three troughs (14 L) of water were provided for each heifer calf and refreshed 3 times per day. Three water types were randomly assigned to the troughs, and an extra trough on each side was left empty to avoid preferential behavior by location. Throughout the 8-d experiment period, the intake of each type of water by each calf was measured. During the study adaptation phase, heifer calves were given TW for 3 d to establish baseline intake. During phase 1, all 3 water types were offered for 3 d. The most-consumed water of each heifer calf was removed after intake data were collected. During phase 2, the remaining 2 water types were offered for 2 d. Water preference ranking by heifer calf was determined based on intake amounts. Kendall's coefficient of concordance (W) was calculated to evaluate the agreement of preference among the heifer calves. The total average water intake was 16.0 ± 2.14, 15.8 ± 1.95, and 14.9 ± 2.21 kg/d for the adaptation phase, phase 1, and phase 2, respectively. During phase 1, average intake was 7.10 ± 3.97, 5.10 ± 3.59, and 3.55 ± 4.89 kg/d for ROW, TW, and UWW, respectively. Three heifer calves preferred ROW first and TW second. Two heifer calves selected TW first and ROW second. One heifer calf chose UWW first and was a potential outlier in the group for taste preference. Average preference rankings were 1.67, 1.83, and 2.50 for ROW, TW, and UWW, with lower numbers indicating greater preference. Overall, most of the heifer calves in the trial showed similar preferences (W = 0.53), meaning that when one heifer calf had a preference for a particular water type, there was a trend for all the calves to prefer that water type. Results showed that the calves slightly preferred ROW over TW, and preferred both ROW and TW over UWW, with greater consumption of ROW when all 3 water types were offered.

Tracking domestic wastewater and road de-icing salt in a municipal drinking water reservoir: Acesulfame and chloride as co-tracers

Developing strategies to identify the origins of contaminants in watersheds is crucial for source water protection. The use of multiple tracers improves the ability to identify contamination events originating from various land use activities. The objective of this study was to evaluate the use of acesulfame and chloride as co-tracers to represent the impact of pollution originating from wastewater and road de-icing on water quality in a municipal drinking water source. The study included a two-year sampling and water quality analysis program in numerous locations within a drinking water reservoir comprising a lake (upstream) and a river (downstream) which supply raw water to a municipal water treatment plant. Results showed that the spatial variability of acesulfame and chloride within the watershed of the lake-river systems depends on the location of contaminant sources, mainly municipal wastewater and septic tank discharges (for acesulfame) and the presence of small tributaries of the lake and river (for chloride). Temporal variability of the tracers under study differed according to the sampling location and was mainly affected by seasonal conditions. Correlation analyses between the two tracers in lake and river waters (in terms of concentrations and loads) made it possible to pinpoint the probable origins of contamination. The assessment of the spatio-temporal variability of these co-tracers within the lake-river watersheds allowed for the delineation of priority intervention zones as a decision-making tool for municipal authorities in improving drinking water source protection.

Analytical pyrolysis of poly(dimethylsiloxane) and poly(oxyethylene) siloxane copolymers. Application to the analysis of sewage sludges

Dimethicone (poly(dimethylsiloxane), PDMS) and its copolymers bearing a poly(ethylene glycol) (PEG) side chain (PEG-12 dimethicone and PEG-8 dimethicone) are utilised as ingredients in personal care products. These materials along with bis-PEG-18 methyl ether dimethyl silane were analysed by Py-GC–MS. The pyrolysates of dimethicone was dominated by cyclic dimethyl siloxanes from D3 to over D10. Besides Dn, the pyrolysates of PEG-dimethicone were featured by the presence of linear dimethyl siloxanes Ln. Hydroxylated siloxanes were also tentatively identified. Pyrograms were also characterised by PEG oligomers with different terminal groups (hydroxyl, ethyl, ethenyl). The molecular structure of pyrolysis products from the combined structural units of PDMS and PEG could not be assigned. Internal standard calibration protocols using pyrolysis products of PEG-12 dimethicone (L6, L8, L9, and triethyleneglycol monoethyl ether) exhibited satisfactory linearity (R2 > 0.992) in the 0.75−58 μg range and repeatability (RSD < 15 %). Three samples of dried sewage sludge from a municipal water treatment plant were extracted with tetrahydrofuran and the extracts analysed by Py-GC–MS. The pyrograms were characterised by intense signals due to the lipid matrix (hydrocarbons, fatty acids, steranes, sterenes, sterols). Dn and Ln were identified indicative for the presence of siloxanes at levels around 60−290 μg gdw−1, while pyrolytic markers of PEG were not revealed. The recovery of PEG-12 dimethicone (17 μg) in spiked sample was 76 %. Galaxolide, galaxolide lactone and triclosan were identified in the pyrograms. The results of this study evidenced the potential of Py-GC–MS as a screening tool for the determination of cosmetic ingredients in sewage sludge.

Nanofiltration to Purify Drinking Water from Cyanobacteria and Microcystins in Water Supply Systems

The pollution of a surface water supply source (Kuibyshev reservoir) with cyanobacterial metabolites under the conditions of the increased biogenic load has been estimated. During the period of mass growth of Cyanobacteria, the reservoir water quality deteriorates in some indicators, including the smell, taste, and content of organic and toxic substances. Among the wide range of cyanotoxins, microcystin-LR, the permissible concentration of which in drinking water should not exceed 1 μg/dm3, poses the greatest threat to the population. Global warming creates favorable conditions for the rapid growth of Cyanobacteria, therefore, the issue of providing the population with high-quality drinking water will further become aggravated.Conventional process lines at municipal water treatment plants are ineffective in removing intracellular and extracellular cyanotoxins. The best and safest barrier against the ingress of cyanotoxins into drinking water can be membrane technologies that allow ultrafiltration of bacterial cells without mechanical damage and nanofiltration of cyanotoxins dissolved in water.

Operating parameters optimization of combined UF/NF dual-membrane process for brackish water treatment and its application performance in municipal drinking water treatment plant

As an important water resource, brackish water has been extensively utilized in the industry. However, there are few cases of municipal potable water treatment plants that use low chloride content brackish water as the source. In this paper, the brackish water treatment efficiency of ultrafiltration (UF)/nanofiltration (NF) dual-membrane process was evaluated in a municipal potable water treatment plant, combining with a pilot optimization experiment. Results showed that UF guaranteed the inlet water quality of NF and NF could efficiently reject organics and salts, with a chloride removal over 95 %. Pilot experiment showed that the UF membrane flux decreased only 12 % after continuously 30-days operation under the optimized UF operation conditions, effectively extending the chemical cleaning interval. Response surface method was adopted in the NF removal efficiency and energy consumption optimization. With the increase of feed water conductivity, the influences of pressure and recovery on the removal efficiency were strengthened, and the removal efficiency could be regulated over a wider range. When the conductivity was less than 3500 μS/cm, NF could perform high treatment efficiency under the operation pressure of 0.65−0.85 MPa and recovery of 55–70 % . Besides, as feed conductivity increased, it was necessary to increase the pressure and reduce the recovery within this range to maintain efficient operation. This paper will provide a guidance for the UF/NF dual-membrane process design and operational optimization.

Artificial neural network modelling of faecal coliform removal in an intermittent cycle extended aeration system-sequential batch reactor based wastewater treatment plant

Artificial neural network (ANN) models have been designed to predict faecal coliform and total coliform removal for an intermittent cycle extended aeration-sequential batch reactor (ICEAS-SBR). Wastewater influent pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), oil & grease (O&G), total kjeldahl nitrogen (TKN), ammonical nitrogen (AN), total phosphorus (TP), faecal coliform, and total coliform were used to develop the network. The data used to train and test the network were obtained from the Jamnagar municipal corporation-waste water treatment plant (JMC-WWTP). Feedforward backpropagation algorithm with learngdm learning function was used to develop ANN models. The number of neurons in hidden layer were varied between 2–10 to find the most reliable network. The optimum ANN models were selected for faecal coliform and total coliform on trial-and-error method. The performance of designed models was tested by computing correlation coefficient, mean absolute deviation (MAD), root mean square error (RMSE), and mean absolute percentage error (MAPE). The network with 6 hidden neurons was optimum for faecal coliform, and 8 hidden neurons was optimum for total coliform. The produced simulation results were within 5 % of MAPE for both faecal and total coliform. The ANN models allow faecal coliform and total coliform levels in the treated wastewater effluent to be regulated that reduces the public and in particular the oyster consumer’s health risks.

Understanding and Improving Microplastic Removal during Water Treatment: Impact of Coagulation and Flocculation.

The efficacy of plastic particle removal by municipal water treatment plants is currently uncertain, and the mechanisms involved in microplastic (MP) coagulation and flocculation have only been superficially investigated. The removal of pristine versus weathered plastic debris and the impact of plastic particle size on removal remain largely unexplored. In this study, coagulation, flocculation, and settling performances were investigated using pristine and weathered MPs (polyethylene (PE) and polystyrene (PS) microspheres, and polyester (PEST) fibers). Weathering processes that changed the surface chemistry and roughness of MPs impacted MP affinity for coagulants and flocculants. A quartz crystal microbalance with dissipation monitoring was used to identify the mechanisms involved during MP coagulation and flocculation. Measured deposition rates confirmed the relatively low affinity between plastic surfaces and aluminum-based coagulants compared to cationic polyacrylamide (PAM). In every case examined, coagulant efficiency increased when the plastic surface was weathered. Removals of 97 and 99% were measured for PEST and weathered PE, respectively. Larger pristine PE MPs were the most resistant to coagulation and flocculation, with 82% removal observed even under enhanced coagulation conditions. By understanding the interaction mechanisms, the removal of weathered MPs was optimized. Finally, this study explored the use of settled water turbidity as a possible indicator of MP removal.

Contaminants, mutagenicity and toxicity in the surface waters of Kyiv, Ukraine

Kyiv is Ukraine's capital and largest city. Home to 3 million people, this area has a rich history of agriculture and industry. The Dnieper River is Ukraine's largest river and it passes through the center of Kyiv. Little information on emerging and legacy compounds or their toxicity in the Dnieper River exists. For this investigation, water was sampled for PAHs, PCBs, metals and emerging contaminants including pharmaceuticals and personal care products. The effects of surface waters in the Dnieper were evaluated using the Ames, chronic and acute daphnia, and a ciliate (Colpoda stennii) assays. Concentrations of legacy and emerging contaminants were found in seven stations near the municipal water treatment plant (MWTP) and receiving waters. The MWTP appeared to remove some of the emerging contaminants, however the legacy compounds (PCBs and PAHs) were not affected by the MWTP and appeared to be more wide-spread indicating a number of sources to the Dnieper River. Acute and chronic toxicity were associated with the influent and effluent of the MWTP, however mutagenicity was noted in surface waters throughout the Dnieper River including upstream of the MWTP. This study provides the first snapshot of possible human health and ecological risks associated with surface waters of the Dnieper. More research on seasonal changes and sources of toxicity, mutagenicity and contaminants would aid in completing a more comprehensive risk assessment of surface waters of the Dnieper River.