Conventional Water Treatment Plants Research Articles

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.

Assessment of cyanobacteria and their taste and odorous metabolites in the lower River Murray: 2000–2022

AbstractCyanobacteria continue to contribute to the taste and odor issues (T&O) in the lower River Murray. A review on the cyanobacteria and T&O data collected in the last 22 years showed that there has been a shift in cyanobacterial community and subsequent T&O profiles. The increased numbers and changes in cyanobacteria occurrence have likely influenced the resultant T&O profiles. T&O challenges started occurring more frequently post‐2015. Although the river has historically been affected by geosmin challenges, up to 999 ng/L of geosmin and 155 ng/L of 2‐methylisoborneol (MIB) concentrations that have been detected along the river. Findings from this study showed that of the 22 water treatment plants investigated, the more advanced ultrafiltration membrane and granular activated carbon system treatment plants were able to mitigate most of the T&O challenges whereas the conventional water treatment plants were more likely to have T&O breakthrough instead.

Summer odors to winter blooms: Treatment validation in the lower River Murray

AbstractA 12‐event survey of 8 water treatment plants (WTPs) was conducted to determine the impact of the 2021 summer (January) to winter (August) cyanobacterial challenge on WTP performance. High cyanobacterial numbers (>20,000 cells/mL) and high taste and odor (T&O) concentrations (>100 ng/L) were encountered. The summer to winter transition of this cyanobacterial challenge also saw the proliferation of Pseudanabaena blooms which challenged conventional WTPs and a breakthrough of cells was detected. This required further investigation into optimizing Pseudanabaena removal in WTP processes. WTP sampling determined that the sludge lagoons provided conducive conditions for cell accumulation and metabolite release. These cells and T&O compounds were recycled back into the head of the WTP through the supernatant return flows. In the most extreme case, 512 ng/L of T&O compounds was detected in the supernatant return. This study highlighted the need to understand the potential risks that treatment plants can encounter and ensure appropriate management during and after cyanobacterial events.

Efficiency of a gravity-driven membrane in a water treatment plant

Abstract Membrane filtration technology is widely applied in conventional surface water treatment plants because of its low power load and high filtration accuracy. This study follows the transition from a power-driven to a gravity-driven siphon-submerged ultrafiltration membrane system in a drinking water treatment plant in Shandong Province, China. The proportion of space membrane areas in the tank was further developed, by increasing the membrane areas of a single tank to 1.6 times that before the transformation, and the design production capacity of a single tank is increased from 10,000 m3/d before the transformation to 16,700 m3/d. The recovery rate of a single tank was also increased from 96.28 to 97.77%. The energy consumption per ton of water decreased from 0.06 to 0.017 MJ. The annual carbon emissions reduction reached 197.13 tons per tank. In terms of the water quality, the algae removal rate from surface water by the ultrafiltration membrane reached 100%. Further, the removal rates of 2 μm particles, turbidity, and chlorophyll were above 99%. Our results suggest that gravity-driven siphon-submerged ultrafiltration promotes environmental protection, energy conservation, and emissions reduction. This technology introduces a new development direction for membrane filtering in drinking water treatment plants.

Assessment of Drinking Water Quality and the Efficiency of the Two Water Treatment Plants in UP, India

This study presents the analysis of the water quality and efficiency of two water treatment plants (370 MLD Palra Reservoir and 310 MLD Conventional Water Treatment Plant). These facilities are catering the water demand of Agra city, having a population of about 2.5 million people. Results have shown that the canal water in Pahansu at Bulandshahr District from the Ganga River has mainly two physical concerns; turbidity and total suspended solids. Other parameters like TDS (Total Dissolved Solids), Hardness, Alkalinity, ORP (Oxidation Reduction Potential) and E.C (Electrical Conductivity) were also measured, but their concentration met the BIS recommended values for mentioned water quality parameters. During the study, it was found that the average TSS concentration at Palra reservoir is 468 mg/l, and the same is removed by about 50% with the help of the sedimentation process. The initial turbidity level is about 10.55 NTU, whereas, after sedimentation, it is 9.12 NTU. After primary treatment, the raw water is conveyed to the 310 MLD Conventional Water Treatment Plant at Sikandara Agra through an under-gravity pipeline traversing 134kms. The Conventional Water Treatment Plant involves Coagulation, Flocculation, Sedimentation, Filtration and Disinfection Processes. Raw water at the inlet has turbidity and TSS around 16.9 NTU and 187 mg/l, respectively. About 50% turbidity removal and 70% TSS removal occur in the clari-flocculator, and the remaining get removed during the rapid sand filtration process, thus, giving final water free from turbidity and TSS. Other parameters of the treated water, like pH, Alkalinity, Hardness, TDS etc., are well within the prescribed limits.

Vertical tubular flocculator: Alternative technology for the improvement of drinking water treatment processes in rural areas

The guarantee of access to safe drinking water for rural communities is a great challenge due to the increase in contamination and deterioration of water sources. Rural areas face technological, financial, and operational limitations, having poor water quality, generally. The purpose of this study was to evaluate the efficiency of a vertical tubular flocculator (VTF) to be used as part of the purification process in rural areas where small flows are used. An experimental treatment system (ETS) implemented in the field was used. The VTF was implemented using PVC pipes and fittings. Tests were carried out with the same raw water used from a conventional treatment plant with aluminum sulfate as a coagulant. The optimal coagulant dose applied in the ETS was determined by the jar test. In the VTF, the length, turbidity, and flow of the raw water were varied. The hydraulic behaviour of the VTF was evaluated with the analysis of the time distribution curve of concentration of a tracer applying the Wolf-Resnick model. A low residence time VTF was obtained, representing a new efficient flocculation model for the reduction of turbidity and colour. The results showed that the turbidity of the raw water, the residence time, and the degree of agitation are important parameters in the operation and efficiency of a VTF. There was a predominance of plug flow in the reactor. The obtained results were compared with the efficiency of a conventional water treatment plant used in the study site. The results obtained indicated that this ETS that integrates a VTF with settling and filtration can be a useful tool for rural areas. It was recommended to replicate this study with wastewater, other dimensions of the VTF, to establish a specific methodology for the design of the VTF, to evaluate the dosage with dose bombs for improving the results of VTF, and to elaborate a hydraulic model for VTF.

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.

Predicting aluminium using full-scale data of a conventional water treatment plant on Orontes River by ANN, GEP, and DT

Predicting aluminium using full-scale data of a conventional water treatment plant on Orontes River by ANN, GEP, and DT

Predicting aluminium using full-scale data of a conventional water treatment plant on Orontes River by ANN, GEP, and DT

Predicting aluminium using full-scale data of a conventional water treatment plant on Orontes River by ANN, GEP, and DT

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 & 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.

Mechanism and thermodynamics of adsorption of diclofenac on graphene-based nanomaterials

The widely used anti-inflammatory diclofenac (DCF) is one of the pharmaceutical drugs most frequently detected in the environment as it is not fully degraded by conventional water treatment plants. Carbon-based adsorbent nanomaterials are attractive for the treatment of wastewater contaminated by pharmaceuticals, due to their high affinity for organic pollutants, high loading capacity, and the efficient regeneration. To obtain insight at molecular level into factors affecting the adsorption of DCF by carbon nanomaterials, molecular dynamics simulations are carried out considering the pure (pG), hydroxyl- (G-OH) and epoxy- (G-COC) functionalized graphene. Also, a material presenting both functional groups is considered (GOX). DCF is adsorbed spontaneously by all materials, but with different types of interactions: π -π and CH-π interactions are present for pG and G-COC, while also hydrogen bonds are formed in the case of G-OH and GOX. While DCF is adsorbed on pG it can translate, this is not the case for the other materials. Spontaneous aggregation leading to the formation to small clusters is observed in all cases when several DCF molecules are present in the system. Free energy calculations give ΔGads which are close to experimental data and follow the order pG < G-COC ∼ G-OH. While for pG adsorption is favored by a negative enthalpy, for the other materials is entropy-driven. We show that surface desolvation plays a major role in determining the thermodynamic affinity order for DCF adsorption. This study provides a theoretical basis for the design and optimization of adsorbent materials with high affinity for DCF.

Photoinduced degradation of three azole compounds from 3rd EU watchlist monitored by high-resolution higher-order mass spectrometry – Part I: A mechanistic study

• Nine new degradation and transformation products of azoles were identified. • HR-MS and HR-MS/MS revealed structures from hydroxyl radical and photo-absorption induced reactions. • Direct and indirect mechanism of degradation could be discerned. Pesticides are found in water bodies worldwide. Among them, there are azoles which are used as fungizides. Hence, tebuconazole, imazalil and penconazole have been included into the 3 rd EU watchlist to survey their presence in water bodies. Pesticides mostly enter the aquatic environment through leaching from agriculture, fruit washing or via conventional sewage water treatment plants, which are often not able to completely eliminate these pesticides. Advanced purification processes have become intensely researched. The advanced oxidation process, UVC and UVA irradiation and addition of the radical scavenger tert -butanol, was investigated using high-resolution higher-order mass spectrometry to gain kinetic and mechanistic insight. Structure elucidation of degradation and transformation products revealed fragments and also multiple hydroxylated intermediates depending on the UV source and the presence of radical scavenger. Hydroxyl radical-induced indirect degradation was found to dominate a direct photoreaction pathway induced by photo-absorption by the initial substance. The indirect mechanism did not occur during UVA irradiation due to the lack of hydroxyl radicals. The radical scavenger decelerated or prevented degradation. In total, nine new degradation and transformation products were identified. Mass spectrometry revealed product structures of the pesticides substituted with one or more hydroxyl radical groups, cyclization and substitution of chlorine by a hydroxyl radical.

Performance Evaluation of Water Treatment Plant of Kekri, Rajasthan, India

Drinking water is a sole element of human life. The rapidly growing population is adding to the excessive demand for water. Increasing demand for drinking water is rising the over-exploitation of water. Raw water sources require water treatment with a high production capacity of treatment. Present research provides a case study of the water treatment plant of Kekri, Rajasthan, India. In these two water treatment plants water purification efficiency is good as compared to conventional water treatment plants. Adding poly aluminum Chloride as a coagulant increases water treatment efficiency. Many parts of the water treatment plant add coagulation-flocculation, filtration, and disinfection by using poly aluminum chloride. Two water treatment plants with the capacity of 142 MLD and 132 MLD are having the net purifying capacity to remove the turbidity and Color. In this research, it has been found that turbidity removal of 142 MLD and 132 MLD WTP was found about 83.4 and 74.1% respectively. Total dissolved solid of surface reservoir Bisalpur dam found within acceptable limits. Total dissolved solids in Bisalpur dam surface water such as Chloride, Fluoride, and Nitrates were found of 60 mg/l, 0.3 mg/l, and 2 mg/l respectively. The pH value of surface water was found of 7.90 and remains almost constant with the seasonal variation impact. Turbidity and color reduction were found within the acceptable limit according to Indian standard 10500-2012.

Membrane technology as an emergency response against drinking water shortage in scenarios of dam failure

With dam failure events, there can be changes in water quality and difficulties in the operation of water treatment plants (WTPs) since they were not designed for water treatment under severe pollution conditions. To avoid that, it was investigated two strategies based on pre-oxidation, ultrafiltration (UF) and reverse osmosis (RO) integrated into a conventional treatment process (coagulation, flocculation, and sand filtration) or with each other, with the potential to reduce the risks of drinking water shortage and guarantee a safe drinking water supply. The study considered the context of the Velhas river basin (Brazil), where water quality is compromised by high turbidities (500–3000 NTU) and excessive arsenic (∼0.4 mg/L), iron (∼50 mg/L), and manganese (∼3 mg/L) levels. They were only partially removed by conventional treatments (removals: 74 ± 21%) and potability standards were only achieved after the membrane separation processes were considered (As: <0.01 mg/L, Mn: <0.1 mg/L, and Fe: <0.3 mg/L). The high water quality after RO enables its blend with the stream obtained after sand filters and would allow for greater flexibility during the operation of WTPs operation. Despite the susceptibility to fouling and most frequent maintenance, the pre-oxidation-UF-RO system would also guarantee a safe drinking water supply. The decision for the most adequate strategy was then based on a multicriteria analysis. A retrofit of conventional WTPs by their integration with UF-RO was classified as the best strategy for centralized facilities, whereas pre-oxidation-UF-RO better fits the reality of decentralized treatments given the lower costs and deployment time. The methodology based on multicriteria analysis and water treatment technologies, exemplified by membranes in this study, presented satisfactory results for different scenarios of critical treatment.

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.

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.