Drinking Water Treatment Systems Research Articles

Assessing the impacts of extreme weather events on potable water quality: the value to managers of a highly participatory, integrated modelling approach

Abstract A decision support tool was created to estimate the treatment efficiency of an Australian drinking water treatment system based on different combinations of extreme weather events and long-term changes. To deal with uncertainties, missing data, and nonlinear behaviours, a Bayesian network (BN) was coupled with a system dynamics (SD) model. The preliminary conceptual structures of these models were developed through stakeholders' consultation. The BN model could rank extreme events, and combinations of them, based on the severity of their impact on health-related water quality. The SD model, in turn, was used to run a long-term estimation of extreme events' impacts by including temporal factors such as increased water demand and customer feedback. The integration of the two models was performed through a combined Monte Carlo–fuzzy logic approach which allowed to take the BN's outputs as inputs for the SD model. The final product is a participatory, multidisciplinary decision support system allowing for robust, sustainable long-term water resources management under uncertain conditions for a specific location.

Formation kinetics of disinfection byproducts in algal-laden water during chlorination: A new insight into evaluating disinfection formation risk

It is necessary and important to investigate the formation of disinfection byproducts (DBPs) in water treatment systems for the management of disinfection formation risk. In the present study, the formation potential of trichloromethane (TCM) and haloacetic acids in different algal metabolites were compared, and the formation kinetics of these DBPs were investigated. The results indicated that DBP formation potential, the traditional index widely used to evaluate the disinfection formation risk, can represent neither the total precursors of DBPs nor the possible generated amounts of DBPs in drinking water systems. Kinetic analyses showed that the formation of DBPs could be well described by a classical second-order reaction kinetic model and that the actual concentrations of DBPs during chlorination were predictable with the model. The formation of DBPs in drinking water treatment systems was highly dependent on the total precursors of DBPs in water and the formation rate of DBPs with chlorine; the latter is usually underestimated in previous studies. Because of their high reactivity, TCM in hydrophilic extracellular organic matter and trichloroacetic acid in all algal metabolites should be serious considerations in the management of disinfection formation risk.

Rad]OH mineralization of norfloxacin in the process of algae bloom water treatment in a drinking water treatment system of 12,000 m3 per day

The accumulation of antibiotics in river watersheds and lakes could induce the spread of antibiotic-resistance genes in drinking water, causing damage to human health. An OH equipment, that produces OH by strong ionization discharge combined with water jet cavitation effect, was installed in a drinking water treatment system of 12,000 m3 per day in Xiang’an water plant, Xiamen of China. The NFX as a model antibiotic was mixed into a branched pipe at a flow rate of 1.0 m3 h−1 for OH mineralization. As a result, the OH after coagulation sedimentation at 1.0 mg L−1 and after sand filtration at 0.5 mg L−1 degraded NFX to not detected within only 20 s. Moreover, the OH mineralizes the NFX into CO2 and H2O by breaking the CF bond, and opening the piperizine, nalidixic, and benzene rings, while NaClO only opens the piperizine ring and adversely forms chlorinated intermediates. By OH disinfection at 0.5 mg L−1 in the main pipe of 500 m3 h−1, all algae blooms were inactivated; the tests of 106 drinking water quality indicators satisfied the Chinese Standards; any disinfection by-products, such as bromate and trihalomethanes (THMs) were not be detected. By NaClO disinfection, the total THMs increased to 190 μg L−1, which is 2.4 times higher than the limit regulated by Environmental Protection Agency (80 μg L−1). To prevent the spread of antibiotic-resistance genes in humans, OH advanced oxidation based on strong ionization discharge could be apply to mineralize antibiotics during practical drinking water treatment.

Isolation and Transcriptome Analysis of Phenol-Degrading Bacterium From Carbon-Sand Filters in a Full-Scale Drinking Water Treatment Plant.

Phenol is a typical organic contaminant in the environment. To date, the biodegradation of phenol by microorganisms remains the preferred method for its removal and remediation, but data on phenol removal by drinking water biofilters are lacking. In this study, we used high-throughput sequencing to investigate the microbial community structure in a carbon–sand biofilter. The results indicated that the predominant bacterial group was Bacilli, followed by Gammaproteobacteria, Clostridia, and Alphaproteobacteria. In addition, a strain was capable of degrading phenol at low concentrations of 500 μg/L within 100 min was isolated and identified as Rhodococcus sp. CS-1. Transcriptome analysis results showed that Rhodococcus sp. CS-1 was able to degrade phenol via both the catechol and protocatechuate branch of the β-ketoadipate pathway. Furthermore, some novel candidate biomarkers (copper oxidase, copper chaperone, and MarR/DeoR/TetR family transcriptional regulators) were successfully identified to be potentially involved in phenol biodegradation. This study indicates that carbon–sand filters have the potential for remediation of phenol. The application of native microorganisms to drinking water treatment system is an adaptive strategy in oligotrophic water environments.

Solubility, partitioning, oxidation and photodegradation of dichloroacetamide herbicide safeners, benoxacor and furilazole

Approximately 242 million kg of herbicides are applied in the United States (US) annually. While herbicides prevent the growth of weeds, they can damage crops resulting in so called “herbicide injury.” To increase herbicidal tolerance of crops, herbicide safeners are commonly added to formulations. Herbicidal safeners are labeled as inert ingredients in herbicide formulations and typically minimal fate and transport information is available. The objective of this study is to experimentally derive the aqueous solubility, octanol-water partition coefficient, and photo-degradation and permanganate oxidation of two dichloroacetamide safeners, benoxacor and furilazole. These results can be used to understand the environmental chemodynamics of these compounds and their degradation via common drinking water treatment systems containing permanganate. The aqueous solubility of benoxacor and furilazole was 22 and 235 mg L−1 respectively while the estimated solubility from EPI Suite was 102.7 and 255 mg L−1 respectively. The log octanol-water partition coefficient of benoxacor and furilazole was 2.23 and 1.96 respectively. The selected safeners were not photodegradable to any great extent. Both benoxacor and furilazole oxidation were found to be second order with respect to initial KMnO4 concentrations. The results of this study can be used to predict distribution of safeners after application in agricultural fields and aid in the design of treatment systems.

Chemical oxidants affect byssus adhesion in the highly invasive fouling mussel Limnoperna fortunei

Biofouling by the invasive mussel species Limnoperna fortunei has caused severe negative consequences in various freshwater ecosystems, but there is still a lack of effective antifouling strategies for this species, particularly in drinking water treatment systems where many existing strategies cannot be used. Chemical oxidants have been proposed to potentially control fouling mussels by influencing 3,4‑dihydroxyphenylalanine oxidation involved in byssus adhesion. To test this potential control strategy, L. fortunei adults were exposed to four oxidants: sodium hypochlorite (NaClO), potassium permanganate (KMnO4), hydrogen peroxide (H2O2) and chloramine T (CAT) at concentrations of 0.5, 1.0, 3.0 and 5.0 mg L−1 for one week. The results showed that low concentrations of KMnO4 stimulated foot protein secretion, which was beneficial to byssus production (number and length). NaClO and H2O2, but not KMnO4 and CAT, significantly inhibited byssus production and reduced breaking force, causing an increased byssus shedding rate. However, only NaClO dissolved byssus and altered the failure location from the byssal thread to adhesive plaque, even when exposed at low concentrations, showing its great impacts on byssus adhesion. Further analysis of polyphenoloxidase activities and gene expression profiles of LfBP-1, LfFP-2 and LfBP-3 revealed that chemical oxidants affected byssus adhesion by altering Dopa oxidation and foot protein gene expressions. This study, therefore, suggests that a low concentration of NaClO can be used as an alternative and environmentally friendly chemical for controlling L. fortunei biofouling by weakening byssus adhesion.

Optimization of Coagulation and Ozonation Processes for Disinfection by–Products Formation Potential Reduction

Optimization of coagulation and ozonation processes for removal of disinfection by–products (DBP) formation potential in raw water was conducted by a pilot scale system. Proper poly–aluminum–chloride–sulfates (PACS), pre–ozone and post–ozone dosages are required for improving the removal performance of DBP formation potential to guarantee the safety of drinking water. Considering the treatment performances and economic costs, the optimum PACS, pre–ozone and post–ozone dosages for treating raw water with high organic concentration should be around 8.9 mg/L Al2O3, 0.5 and 2.5 mg/L, respectively. The combined drinking water treatment system of pre–ozonation, coagulation/sedimentation, sand filtration, post–ozonation, granular activated carbon filtration and disinfection is a promising process to reduce DBP formation potential from raw water in southern China. Under the optimum conditions, this combined system removed total trihalomethanes and haloacetic acids formation potential 50.16 and 69.10%, respectively.

Environmental social benefits for water potabilization in the palafític peoples of cienaga grande de Santa Marta-Colombia

Water purification involves the use of technologies, in which various treatment processes are carried out, whose purpose is to remove contaminants in water up to certain concentrations, which do not represent a risk to human health (Rojas, 2015). An unconventional drinking water treatment system refers to alternative treatments, either by advanced potabilization processes or by decentralized or emerging systems.

Modified biosand filter coupled with a solar water pasteurizer: Decontamination study

Modified biosand filters (MBSF) and solar pasteurizers have been used as individual drinking water treatment systems around the world. The aim of this study is to evaluate the performance of a MBSF coupled with a solar pasteurizer for effective treatment systems for source water. The MBSF was designed with an extra disinfection layer with zero valent iron (ZVI) and three layers of underdrain to remove Escherichia coli (E. coli), total coliforms and turbidity. A flat solar panel with a solenoid valve was used as a solar pasteurizer and an extra disinfection system to remove residual E. coli and total coliforms from filtered water. The pasteurizer produced an average of 4.5 l of pasteurized water per day. 75 °C was selected as pasteurization temperature. A 96.25% reduction (log 1.65) in total coliforms, 98% reduction (log 2.27) in E. coli and 94.8% reduction in turbidity was observed in the filtered water samples. After the pasteurization, 100% of the E. coli and 99.99% of the total coliforms reductions were observed in the filtered and the unfiltered water. The turbidity level of the pasteurized unfiltered water did not meet the drinking water standards. However, the water quality met World Health Organization drinking water standards for the MBSF system coupled with the solar pasteurizer.

HRT EFFECT ON SIMULTANEOUS COD, AMMONIA AND MANGANESE REMOVAL FROM DRINKING WATERTREATMENT SYSTEM USING A BIOLOGICAL AERATED FILTER (BAF)

Three different hydraulic retention times (HRTs) were investigated for NH +-N and Mn2+ removal using an upflow biological aerated system (BAF) as a new approach in drinking water treatment system. Currently in Malaysia, there is no specific treatment for NH +-N and Mn2+ in drinking water treatment plant. BAF is a well known system in biological treatment for wastewater but not for drinking water treatment. This study showed that at 24 hours operation of BAF system, about 91.3% of COD, 94.4% of NH4-N and 83.4% of Mn2+ were efficiently removed. When HRT was decreased to 12 and 6 hours, there was insignificant removal difference in COD and NH +-N removal. Instead, the Mn2+ removal significantly showed an increasing trend (p<0.05) as the HRT was decreased with the removal percentages of 92.1% (12 hours) and 94.8% (6 hours). Real-time monitoring through pH, ORP and DO profiles confirmed that completed simultaneous NH +-N and Mn2+ removal occurred within 6 to 7 hours HRT.

Drinking Water Treatment by Inductively Coupled Plasma System to Remove of Microorganisms in River Water

Inductively coupled plasma system was used in drinking water treatment system to kill the microorganisms in water such as total coliforms (TC), fecal coliforms (FC) and other coliforms (OC) from river water. The aim of this study was to investigate the effect of flowrate on removal efficiency (RE), death rate, and death yield and energy consumption of bacteria's. The frequency of the system was set at 4.6 MHz. The results show that the removal efficiencies and death rate of TC, FC and OC decreased with increasing flowrate. Compared to FC, the first-order reactions of TC and OC were lower in the following order: FC &gt; OC &gt; TC. The death yield of TC and OC significantly increased when the removal efficiency increased. The electromagnetic flux varied from 19.44 to 20.55 W/cm2 and the energy consumption was 0.26, 0.32, and 0.67 with flow rate at 20, 10 and 5 mL/minute, respectively. These results are very necessary to improve drinking water treatment.

Effect of Biological Contact Filters (BCFs) on Membrane Fouling in Drinking Water Treatment Systems

Membrane fouling is a serious problem in drinking water treatment systems. Biological contact filters (BCFs) are often used as a pretreatment to remove ammonia, dissolved organic matter (DOM), and metal ions such as iron and manganese. In this study, the effect of BCF as a pretreatment for membrane fouling was evaluated using a laboratory-scale mini module consisting of a mini BCF column and a mini MF column. Initially, it was confirmed that the main foulant was a biopolymer (at low concentration) in the raw water. Subsequently, the biopolymer concentrations in the BCF influent and effluent were measured with the excitation emission matrix (EEM) fluorescence spectroscopy and the liquid chromatograph organic carbon detector (LC-OCD). The fouling potential of the BCF influent and effluent was also measured to evaluate MF membrane fouling rate. The results demonstrate that application of the BCF reduced the biopolymer concentration of the effluent and reduced membrane fouling. The effect of BCF was also established in an actual drinking water treatment plant. It was found that optimizing the contact time of raw water with the BCF was crucial to reduce membrane fouling.

Trace Element Removal in Distributed Drinking Water Treatment Systems by Cathodic H2O2 Production and UV Photolysis.

As water scarcity intensifies, point-of-use and point-of-entry treatment may provide a means of exploiting locally available water resources that are currently considered to be unsafe for human consumption. Among the different classes of drinking water contaminants, toxic trace elements (e.g., arsenic and lead) pose substantial operational challenges for distributed drinking water treatment systems. Removal of toxic trace elements via adsorption onto iron oxides is an inexpensive and robust treatment method; however, the presence of metal-complexing ligands associated with natural organic matter (NOM) often prevents the formation of iron precipitates at the relatively low concentrations of dissolved iron typically present in natural water sources, thereby requiring the addition of iron which complicates the treatment process and results in a need to dispose of relatively large amounts of accumulated solids. A point-of-use treatment device consisting of a cathodic cell that produced hydrogen peroxide (H2O2) followed by an ultraviolet (UV) irradiation chamber was used to decrease colloid stabilization and metal-complexing capacity of NOM present in groundwater. Exposure to UV light altered NOM, converting ∼6 μM of iron oxides into settable forms that removed between 0.5 and 1 μM of arsenic (As), lead (Pb), and copper (Cu) from solution via adsorption. After treatment, changes in NOM consistent with the loss of iron-complexing carboxylate ligands were observed, including decreases in UV absorbance and shifts in the molecular composition of NOM to higher H/C and lower O/C ratios. Chronoamperometric experiments conducted in synthetic groundwater revealed that the presence of Ca2+ and Mg2+ inhibited intramolecular charge-transfer within photoexcited NOM, leading to substantially increased removal of iron and trace elements.

Microbial Communities Shaped by Treatment Processes in a Drinking Water Treatment Plant and Their Contribution and Threat to Drinking Water Safety.

Bacteria play an important role in water purification in drinking water treatment systems. On one hand, bacteria present in the untreated water may help in its purification through biodegradation of the contaminants. On the other hand, some bacteria may be human pathogens and pose a threat to consumers. The present study investigated bacterial communities using Illumina MiSeq sequencing of 16S rRNA genes and their functions were predicted using PICRUSt in a treatment system, including the biofilms on sand filters and biological activated carbon (BAC) filters, in 4 months. In addition, quantitative analyses of specific bacterial populations were performed by real-time quantitative polymerase chain reaction (qPCR). The bacterial community composition of post-ozonation effluent, BAC effluent and disinfected water varied with sampling time. However, the bacterial community structures at other treatment steps were relatively stable, despite great variations of source water quality, resulting in stable treatment performance. Illumina MiSeq sequencing illustrated that Proteobacteria was dominant bacterial phylum. Chlorine disinfection significantly influenced the microbial community structure, while other treatment processes were synergetic. Bacterial communities in water and biofilms were distinct, and distinctions of bacterial communities also existed between different biofilms. By contrast, the functional composition of biofilms on different filters were similar. Some functional genes related to pollutant degradation were found widely distributed throughout the treatment processes. The distributions of Mycobacterium spp. and Legionella spp. in water and biofilms were revealed by real-time quantitative polymerase chain reaction (qPCR). Most bacteria, including potential pathogens, could be effectively removed by chlorine disinfection. However, some bacteria presented great resistance to chlorine. qPCRs showed that Mycobacterium spp. could not be effectively removed by chlorine. These resistant bacteria and, especially potential pathogens should receive more attention. Redundancy analysis (RDA) showed that turbidity, ammonia nitrogen and total organic carbon (TOC) exerted significant effects on community profiles. Overall, this study provides insight into variations of microbial communities in the treatment processes and aids the optimization of drinking water treatment plant design and operation for public health.

Persistence of antibiotic resistance genes and bacterial community changes in drinking water treatment system: From drinking water source to tap water

As emerging contaminants, antibiotic resistance genes (ARGs) have become a public concern. This study aimed to investigate the occurrence and diversity of ARGs, and variation in the composition of bacterial communities in source water, drinking water treatment plants, and tap water in the Pearl River Delta region, South China. Various ARGs were present in the different types of water. Among the 27 target ARGs, floR and sul1 dominated in source water from three large rivers in the region. Pearson correlation analysis suggested that sul1, sul2, floR, and cmlA could be potential indicators for ARGs in water samples. The total abundance of the detected ARGs in tap water was much lower than that in source water. Sand filtration and sedimentation in drinking water treatment plants could effectively remove ARGs; in contrast, granular activated carbon filtration increased the abundance of ARGs. It was found that Pseudomonas may be involved in the proliferation and dissemination of ARGs in the studied drinking water treatment system. Bacteria and ARGs were still present in tap water after treatment, though they were significantly reduced. More research is needed to optimize the water treatment process for ARG removal.

Inhibition of Daphnia magna's occurrence in drinking water treatment process by controlling its phototactic behavior.

Cladocera zooplankton as carriers of bacteria result in biological risk due to their occurrence in drinking water treatment systems. In this paper, bench-scale experiments were performed to investigate the inhibition effect on Daphnia magna (D. magna) by controlling its phototactic behavior. The results showed that UVA had a negative effect on the phototaxis of D. magna, indicating an active movement away from light source, while blue light was positive in inducing phototactic behavior. The water quality could influence the phototactic behavior of D. magna. When the turbidity value was higher than 10 NTU or total organic carbon (TOC) concentration was beyond 4 mg/L, the phototaxis of D. magna to UVA (25 μw/cm2 intensity) or blue light (1,000 Lux intensity) was significantly weakened. It was difficult for D. magna to offset the effect of water flow by its phototactic movement when the flow rate was higher than 10 mm/s. According to the above results, with suitable process parameters in full-scale experiments, the occurrence of D. magna in the effluent of sedimentation tank and activated carbon filter was obviously inhibited by the UVA irradiation and blue light induction, respectively.

Comparison of biofilm cell quantification methods for drinking water distribution systems

Drinking water quality typically degrades after treatment during conveyance through the distribution system. Potential causes include biofilm growth in distribution pipes which may result in pathogen retention, inhibited disinfectant diffusion, and proliferation of bad tastes and odors. However, there is no standard method for direct measurement of biofilms or quantification of biofilm cells in drinking water distribution systems.Three methods are compared here for quantification of biofilm cells grown in pipe loops samplers: biofilm heterotrophic plate count (HPC), biofilm biovolume by confocal laser scanning microscopy (CLSM) and biofilm total cell count by flow cytometry (FCM) paired with Syto 9. Both biofilm biovolume by CLSM and biofilm total cell count by FCM were evaluated for quantification of the whole biofilms (including non-viable cells and viable but not culturable cells). Signal-to-background ratios and overall performance of biofilm biovolume by CLSM and biofilm total cell count by FCM were found to vary with the pipe material. Biofilm total cell count by FCM had a low signal-to-background ratio on all materials, indicating that further development is recommended before application in drinking water environments. Biofilm biovolume by CLSM showed the highest signal-to-background ratio for cement and cast iron, which suggests promise for wider application in full-scale systems.Biofilm biovolume by CLSM and Syto 9 staining allowed in-situ biofilm cell quantification thus elimination variable associated with cell detachment for quantification but had limitations associated with non-specific staining of cement and, to a lesser degree, auto-fluorescence of both cement and polyvinyl chloride materials.Due to variability in results obtained from each method, multiple methods are recommended to assess biofilm growth in drinking water distribution systems. Of the methods investigated here, HPC and CLSM and recommended for further development towards application in full-scale systems. HPC is a sample and widely applied method that quantifies viable culturable cells. CLSM analysis allows the elimination of experimental variables associated with cell detachment and affords the opportunity to evaluate biofilm components such as extracellular polymeric substances through the addition of specific probes. These two methods can be applied together to assess biofilms known to degrade treated water quality during conveyance in full-scale drinking water treatment systems. The significance of improved biofilm assessment methods for drinking water distribution systems lies in advancing understanding of biofilm growth and control mechanisms that may lead to improved water quality during conveyance and at the tap for greater public health protection.

Projecting Financial Capability in Small Canadian Drinking Water Treatment Systems

This article determines the minimum service population for which construction and operation of drinking water treatment systems become financially viable by comparing costs with revenue. The feasibility of five solutions that have been implemented in Canada are discussed and tested for financial viability using a novel methodology. Recently published cost equations predict that drinking water treatment plants become financially viable at an estimated population of 920 for surface water sources and 360 for groundwater sources. Intersection points between the cost and revenue curves occur at considerably higher populations than predicted by the Statistics Canada–Calgary Regional Partnership cost equations, highlighting the challenges small systems face in providing drinking water in a sustainable and affordable manner. Decision makers should consider alternative solutions for drinking water supply at unviable service populations, including delivery of water via small diameter “trickle fill” distribution systems, point‐of‐entry and point‐of‐use treatment, and bottle fill stations.

Water Supply in Developing Countries: Student Experiences in the Dominican Republic

In 2010, the United Nations established access to safe drinking water as a basic human right; however, many areas around the globe still lack access. The interdisciplinary service-learning course “Water Supply in Developing Countries” was established at Purdue in 2012 to address the complex issue of water insecurity around the world. Over the past five years, the course has produced teams involving students from nursing, engineering, agricultural economics, biology, and food science working together to develop sustainable, community-scale drinking water treatment systems. In partnership with Aqua Clara International, the student team in 2017 established a drinking water treatment system at the Ana Julia Diaz Luna primary school in the rural community of Las Cañas, Dominican Republic. In addition to the focus on a physical water system, they also collaborated with local educators to design a water, sanitation, and hygiene (WASH) education program. Students guided development of sustainable economic strategies to utilize the system for generation of revenue to reinvest in maintenance and improvements. The observations and lessons learned from the completed stages of this project have been applied to improve the effectiveness and efficiency of subsequent interventions.

A-19 上質水供給設備の開発 : その1 連続通水実験による処理性能の把握とおいしさの評価

A-19 上質水供給設備の開発 : その1 連続通水実験による処理性能の把握とおいしさの評価