Advanced Water Treatment Processes Research Articles

Preparation of alumina-zirconia (Al-Zr) ceramic nanofiltration (NF) membrane for the removal of uranium in aquatic system

Abstract In this research, ceramic nanofiltration (NF) membranes were prepared by depositing alumina-zirconia (Al-Zr) nanoparticles into the pores of ceramic ultrafiltration (UF) membranes for the removal of radioactive uranium in an aquatic system. The modified ceramic membranes showed NF membrane performance with around 1,000 Da molecular weight cut-off (MWCO) and 58% CaCl2 rejection. The removal efficiencies of uranium species by these successfully modified ceramic NF membranes exhibited differences depending on the pH conditions (pH 5.0, 7.4, and 10.0), and achieved the highest rejection of 91% at pH 7.4. This behavior is due to the dominant aqueous species of uranium in pH 7.4, (UO2)2CO3(OH3)−, which has the largest molecular weight among the conditions and the negatively charged species having electrostatic attraction to the positively charged ceramic NF membranes. The ceramic NF membrane prepared here is expected to be feasible in the advanced water treatment process to remove radioactive compounds.

Emerging pollutants removal through advanced drinking water treatment: A review on processes and environmental performances assessment

Abstract The presence of emerging pollutants in the aquatic environment in relatively small concentrations and the fact that they cannot be removed by conventional water/wastewater treatment processes bring new challenges in terms of adequate selection of technologies from the technical, economical and environmental points of view. Generally, literature discusses emerging pollutants’ removal at significant concentrations (such as those in wastewater), while few studies consider their low concentrations occurring in raw water. This study presents a comprehensive review of the research efforts related to the occurrence, fate, health effects and impacts of emerging pollutants on advanced drinking water treatment and the environmental performance evaluation of different technological options, with a focus on pilot and full-scale installations. All presented case studies consider pollutants removed, process conditions and removal efficiencies, thus making possible comparisons between membrane processes, advanced oxidation processes and adsorption on activated carbon and other materials. The study is completed by an analysis of the environmental assessment instruments (life cycle assessment, carbon, water footprints, other type of assessments) that may be used for selecting sustainable advanced drinking water treatment processes able to remove emerging pollutants. This paper critically reviews the main research topics concerning emerging pollutants: classification, legislative framework, up-to-date removal processes and their environmental performances assessment, to offer a comprehensive analysis of the strategic issues that may constitute future research directions for sustainable water supply.

Performance of ozonation and biological activated carbon in eliminating sulfonamides and sulfonamide-resistant bacteria: A pilot-scale study

Removal of sulfonamides (SAs) by an integrated ozonation and biological activated carbon filtration (O3-BAC) process, as an advanced drinking water treatment process, was evaluated in a pilot-scale study. Furthermore, the effects of the O3-BAC process on sulfonamide-resistant bacteria (SRB) and on the removal of total organic carbon, UV254, and turbidity were investigated. Results indicate that ozonation could effectively remove SAs from water at an appropriate ozone dose with an improvement of water quality; however, BAC filtration would lead to an increase of SRB. In addition, the performance of the integrated process in eliminating disinfection byproducts formation potential (DBPsFP) in chlorination was evaluated. The results show ozonation would result in an increase of DBPsFP, while subsequent BAC filtration could effectively reduce DBPsFP to the safety-standard level of water quality. Overall, effective removal was achieved by the O3-BAC process in terms of the reduction of SAs but not of SRB. Subsequent disinfection is significant and biological safety should be evaluated further to ensure the effectiveness of the integrated process and the security of water quality.

A novel concept to integrate energy recovery into potable water reuse treatment schemes

AbstractPotable water reuse applications can provide a safe and sustainable water supply where conventional freshwater resources are limited. The objectives of this study were fourfold: (i) to analyse existing potable water reuse applications regarding operational characteristics and energy demands, (ii) to determine the theoretical energy potential of wastewater and identify opportunities for energy recovery, (iii) to define design requirements for potable water reuse schemes that integrate energy recovery and (iv) to propose strategies for more energy efficient potable water reuse schemes. Existing potable water reuse schemes commonly utilize conventional wastewater treatment processes including biological nutrient removal followed by advanced water treatment processes. While meeting high product water quality, these treatment schemes are characterized by relatively high specific energy demands (1.18 kWh/m3). Given that the theoretical energy potential of municipal wastewater is approximately two times higher (2.52 kWh/m3), opportunities exist to integrate energy recovery strategies. We propose three alternative potable water reuse schemes that integrate energy recovery from carbon via methane and nitrogen via either the coupled aerobic–anoxic nitrous decomposition operation process or partial nitritation/anammox. Compared to conventional potable water reuse schemes, the energy requirements of these schemes can be reduced by 7–29% and the overall energy balance by 38–80%.

Sample handling and data processing for fluorescent excitation-emission matrix (EEM) of dissolved organic matter (DOM)

In environmental engineering and science, fluorescent excitation-emission matrix (EEM) has increasingly been utilized to characterize chromophoric dissolved organic matter (CDOM). This study aims to delineate EEM data processing, including calculation of total fluorescence (TF) which is an emerging water quality parameter often used as a surrogate for micropollutant removal by advanced water treatment processes. In addition, sample handling procedures such as storage, use of preservatives, and oxidant quenching agents were evaluated. In this study, three antimicrobial preservatives were tested: sodium azide, sodium omadine, and thymol. All the tested preservatives altered optical properties of samples, and were therefore not suitable for the preservation of EEM samples. Without preservative, storage of samples at 4 °C maintained TF within 7.5% of its original value for 21 days, while TF of samples stored at the room temperature more drastically changed (up to 15%). The impacts of three oxidant quenching agents including ascorbic acid, sodium bisulfite, and sodium thiosulfate on EEM were also tested. Among the quenching agents, sodium bisulfite was found to be suitable since it little influenced optical properties of samples while the other two were not favorable due to interference. We also scrutinized the use of TF as surrogate to monitor micropollutant rejection by nanofiltration membrane.

Experimental Application of an Advanced Separation Process for NOM Removal from Surface Drinking Water Supply

Natural organic matter (NOM) in drinking water supplies significantly impacts on water supply quality and treatment, due to observed reactivity with many dissolved and particulate species. Several technologies are used nowadays to remove NOM from the water supply. The evolution of water-related directives, and progressively more restrictive standards for drinking water, however, call for the investigation of advanced, more efficient, and cost-effective water treatment processes. This paper contains a brief overview on the state-of-the-art methods for NOM removal from supply waters, and describes the experimental application of an advanced technology, tested and validated at the pilot scale on the water supply source of a town in Poland. The process allowed significant removal of natural organic matter (about 50% as Dissolved Organic Carbon) and turbidity (from 50% to 90%), however, these results requested significant additions of powdered activated carbon. The key to success of this type of process is a correct setup with the identification of optimal types and dosages of reagents. Based on the results of the tests conducted it is foreseeable that this technology could be used onsite, not only for removal of NOM, but also of other hard-to-tackle pollutants potentially contained in the freshwater supply and not presently considered.

Development of a Concentration Prediction Model for Disinfection By-product according to Introduce the Advanced Water Treatment Process in Water Supply Network

Development of a Concentration Prediction Model for Disinfection By-product according to Introduce the Advanced Water Treatment Process in Water Supply Network

The conformation-independent QSPR approach for predicting the oxidation rate constant of water micropollutants

In advanced water treatment processes, the degradation efficiency of contaminants depends on the reactivity of the hydroxyl radical toward a target micropollutant. The present study predicts the hydroxyl radical rate constant in water (k OH) for 118 emerging micropollutants, by means of quantitative structure-property relationships (QSPR). The conformation-independent QSPR approach is employed, together with a large number of 15,251 molecular descriptors derived with the PaDEL, Epi Suite, and Mold2 freewares. The best multivariable linear regression (MLR) models are found with the replacement method variable subset selection technique. The proposed five-descriptor model has the following statistics for the training set: [Formula: see text], RMS train = 0.21, while for the test set is [Formula: see text], RMS test = 0.11. This QSPR serves as a rational guide for predicting oxidation processes of micropollutants.

Removal of Selected Micropollutants During Conventional and Advanced Water Treatment Processes

Micropollutants such as caffeine, carbamazepine, metoprolol (MTP), and sulfamethoxazole (SMZ), which are frequently detected in aquatic environments, were selected, and their removal and persistence using classical water treatment processes (coagulation, adsorption, and chlorination), and advanced oxidation processes (AOPs) (ozonation, UV photolysis, UV/H2O2, and UV/chlorine) were examined using liquid chromatography–tandem mass spectrometry (LC-MS/MS). While SMZ was most effectively removed, MTP showed the lowest removal efficiency in all applied water treatments. During coagulation and adsorption processes, SMZ was effectively removed by electrostatic interaction. Chlorination was not effective for removal of the selected micropollutants. Among AOPs, UV/chlorine reaction showed the most effective removal (90–100%) for selected micropollutants, including MTP. Considering its persistence, MTP was proposed as an indicator micropollutant during water treatment.

Tracking changes in composition and amount of dissolved organic matter throughout drinking water treatment plants by comprehensive two-dimensional gas chromatography–quadrupole mass spectrometry

Dissolved organic matter (DOM) can affect the performance of water treatment processes and produce undesirable disinfection by-products during disinfection. Several studies have been undertaken on the structural characterization of DOM, but its fate during drinking water treatment processes is still not fully understood. In this work, the nontargeted screening method of comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC×GC-qMS) was used to reveal the detailed changes of different chemical classes of compounds in DOM during conventional and advanced drinking water treatment processes at three drinking water treatment plants in China. The results showed that when the dissolved organic carbon removal was low, shifts in the DOM composition could not be detected with the specific ultraviolet absorbance at 254nm, but the changes were clear in the three-dimensional fluorescence excitation-emission matrix or GC×GC-qMS analyses. Coagulation-sedimentation processes selectively removed 37–59% of the nitrogenous compounds, alcohols and aromatic hydrocarbons but increased the concentrations of halogen-containing compounds by 17–26% because of the contact time with chlorine in this step. Filtration was less efficient at removing DOM but preferentially removed 21–60% of the acids. However, other organic matter would be released from the filter (e.g., nitrogenous compounds, acids, and aromatic hydrocarbons). Biological activated carbon (BAC) treatment removed most of the compounds produced from ozonation, particularly ketones, alcohols, halogen-containing compounds and acids. However, it should be noted that certain highly polar or high molecular weight compounds not identified in this study might be released from the BAC bed. After the whole treatment processes, the concentrations of nitrogenous compounds, alcohols, alkenes, aromatic hydrocarbons and ketones were decreased more by the advanced treatment processes than by the conventional treatment processes. Alcohol and ketone removals were probably related to the reduction in protein-like materials. Alkane removal was probably related to the reduction in fulvic acid-like and humic acid-like materials.

Formation and control of nitrogenous DBPs from Western Australian source waters: Investigating the impacts of high nitrogen and bromide concentrations

We studied the formation of four nitrogenous DBPs (N-DBPs) classes (haloacetonitriles, halonitromethanes, haloacetamides, and N-nitrosamines), as well as trihalomethanes and total organic halogen (TOX), after chlorination or chloramination of source waters. We also evaluated the relative and additive toxicity of N-DBPs and water treatment options for minimisation of N-DBPs. The formation of halonitromethanes, haloacetamides, and N-nitrosamines was higher after chloramination and positively correlated with dissolved organic nitrogen or total nitrogen. N-DBPs were major contributors to the toxicity of both chlorinated and chloraminated waters. The strong correlation between bromide concentration and the overall calculated DBP additive toxicity for both chlorinated and chloraminated source waters demonstrated that formation of brominated haloacetonitriles was the main contributor to toxicity. Ozone–biological activated carbon treatment was not effective in removing N-DBP precursors. The occurrence and formation of N-DBPs should be investigated on a case-by-case basis, especially where advanced water treatment processes are being considered to minimise their formation in drinking waters, and where chloramination is used for final disinfection.

Biologically active filters – An advanced water treatment process for contaminants of emerging concern

With the increasing concern of contaminants of emerging concern (CECs) in source water, this study examines the hypothesis that existing filters in water treatment plants can be converted to biologically active filters (BAFs) to treat these compounds. Removals through bench-scale BAFs were evaluated as a function of media, granular activated carbon (GAC) and dual media, empty bed contact time (EBCT), and pre-ozonation. For GAC BAFs, greater oxygen consumption, increased pH drop, and greater dissolved organic carbon removal normalized to adenosine triphosphate (ATP) were observed indicating increased microbial activity as compared to anthracite/sand dual media BAFs. ATP concentrations in the upper portion of the BAFs were as much as four times greater than the middle and lower portions of the dual media and 1.5 times greater in GAC. Sixteen CECs were spiked in the source water. At an EBCT of 18 min (min), GAC BAFs were highly effective with overall removals greater than 80% without pre-ozonation; exceptions included tri(2-chloroethyl) phosphate and iopromide. With a 10 min EBCT, the degree of CECs removal was reduced with less than half of the compounds removed at greater than 80%. The dual media BAFs showed limited CECs removal with only four compounds removed at greater than 80%, and 10 compounds were reduced by less than 50% with either EBCT. This study demonstrated that GAC BAFs with and without pre-ozonation are an effective and advanced technology for treating emerging contaminants. On the other hand, pre-ozonation is needed for dual media BAFs to remove CECs. The most cost effective operating conditions for dual media BAFs were a 10 min EBCT with the application of pre-ozonation.

The occurrence and removal of algae (including cyanobacteria) and their related organic compounds from source water in Vaalkop Dam with conventional and advanced drinking water treatment processes

Cyanobacterial bloom formation in freshwaters, such as rivers, lakes and dams, is known to occur throughout the world. The Vaalkop Dam, which serves as source to the Vaalkop drinking water treatment works (DWTW), is no exception. Blooms of cyanobacteria occur annually in Vaalkop Dam as well as in dams from which Vaalkop is replenished during low-rainfall periods. These blooms during the summer months are associated with the production of cyanotoxins and taste and odour compounds such as geosmin and MIB. The Vaalkop DWTW uses a combination of conventional and advanced water treatment processes to deal with the cyanobacteria and their related organic compounds in the source water. The overall objectives of this study were to: (i) investigate the occurrence of algae (including cyanobacteria) and cyanotoxins in the Vaalkop Dam; (ii) establish which environmental variables are responsible for the development and onset of algae, and (iii) determine whether the Vaalkop DWTW is able to eliminate the influence that algae (including cyanobacteria) may have on the drinking water. Multivariate statistical analyses revealed seasonal variation in algal assemblages in the raw water. The risk of cyanobacteria bloom formation proved to be especially high during the summer months as the nutrients needed for cyanobacterial growth are available and the temperature range is optimal, causing the production of geosmin, MIB and microcystin. The presence of Ceratium hirundinella (O.F. Muller) Dujardin, in the source water appears to exacerbate the negative effect that cyanobacteria have on the drinking water treatment process. When Ceratium hirundinella is present, floc formation is inhibited, causing more of the problematic algae to penetrate into the drinking water. Even though advanced treatment options such as ozone and granular activated carbon filters are used at Vaalkop DWTW, the effects of the organic compounds produced by cyanobacteria are not entirely eliminated during the treatment process. Keywords : potable water treatment, geosmin, MIB (2-methylisoborneol), microcystin, granular activated carbon (GAC), ozone

Catalytic reduction of bromate over monometallic catalysts on different powder and structured supports

Bromate in water has been associated with cancer risks for lifetime exposures, and present technologies for its removal have important drawbacks that create a need for the development of new and more efficient alternatives. Heterogeneous catalysis has been explored for the removal of inorganic pollutants from water with promising results. In this work we aim to improve the efficiency of the catalytic reduction of bromate to bromine by exploring different supports (activated carbon, titanium dioxide and multi-walled carbon nanotubes) for the catalytic metallic phase (Pd, Pt, Rh and Ru). Improvements of the turn-over frequency in the order of 1000 from previously reported activated carbon supported catalysts were obtained with titanium dioxide and multi-walled carbon nanotubes for experiments using 10mgL−1 initial concentration of bromate; leading to complete conversion into bromide in under 5min for TiO2 and 30min for MWCNT.On the other hand, the use of structured catalysts for advanced water treatment processes has been recently shown as a promising alternative for conventional catalysts. We demonstrate the application of highly active metal-support pairings on a structured catalyst towards bromate removal during continuous operation, achieving up to 87% bromate conversion at steady-state.

A pilot plant study using conventional and advanced water treatment processes: Evaluating removal efficiency of indicator compounds representative of pharmaceuticals and personal care products

With widespread occurrence of pharmaceuticals and personal care products (PPCPs) in the water cycle, their presence in source water has led to the need to better understand their treatability and removal efficiency in treatment processes. Fifteen indicator compounds were identified to represent the large number of PPCPs reported worldwide. Criteria applied to determine the indicator compounds included PPCPs widely used, observed at great frequency in aqueous systems, resistant to treatment, persistent in the environment, and representative of classes of organics. Through a pilot plant investigation to understand the optimal combination of unit process for treating PPCPs, 12 treatment trains with their additive and synergistic contributions were investigated; processes included dissolved air flotation (DAF), pre- and intermediate-ozonation with and without H2O2, intermediate chlorination, dual media filtration, granular activated carbon (GAC), and UV/H2O2. Treatment trains that achieved the greatest removals involved 1. DAF followed by intermediate ozonation, dual media filtration, and virgin GAC; 2. pre-ozonation followed by DAF, dual media filtration, and virgin GAC; and, 3. DAF (with either pre- or intermediate oxidation) followed by dual media filtration and UV/H2O2. Results revealed significant removal efficiencies for virgin GAC (preceded by DAF and intermediate ozonation) and UV/H2O2 with an intensity of 700 mJ/cm2, where more than 12 of the compounds were removed by greater than 90%. Reduced PPCP removals were observed with virgin GAC preceded by pre-ozonation and DAF. Intermediate ozonation was more effective than using pre-ozonation, demonstrating the importance of this process targeting PPCPs after treatment of natural organic matter. Removal efficiencies of indicator compounds through ozonation were found to be a function of the O3 rate constants (kO3). For compounds with low O3 rate constants (kO3 < 10 M−1s−1), H2O2 addition in the O3 reactor was required. Of the 15 indicator compounds, tri(2-chloroethyl) phosphate (TCEP) and cotinine were observed to be the most recalcitrant. Although UV/H2O2 with elevated intensity (700 mJ/cm2) was effective for PPCP removals, energy requirements far exceed intensities applied for disinfection.

The removal of organic precursors of DBPs during three advanced water treatment processes including ultrafiltration, biofiltration, and ozonation.

The removal efficiency of organic matter, the formation potential of trihalomethanes (THMFP), and the formation potential of haloacetic acids (HAAFP) in each unit of three advanced treatment processes were investigated in this paper. The molecular weight distribution and the components of organic matter in water samples were also determined to study the transformation of organic matter during these advanced treatments. Low-molecular-weight matter was the predominant fraction in raw water, and it could not be removed effectively by ultrafiltration and biofiltration. The dominant species of disinfection by-product formation potential (DBPFP) in raw water were chloroform and monochloroacetic acid (MCAA), with average concentrations of 107.3 and 125.9μg/L, respectively. However, the formation potential of chloroform and MCAA decreased to 36.2 and 11.5μg/L after ultrafiltration. Similarly, biological pretreatment obtained high removal efficiency for DBPFP. The total THMFP decreased from 173.8 to 81.8μg/L, and the total HAAFP decreased from 211.9 to 84.2μg/L. Separate ozonation had an adverse effect on DBPFP, especially for chlorinated HAAFP. Numerous low-molecular-weight compounds such as aldehydes, ketones, and alcohols were generated during the ozonation, which have been proven to be important precursors of HAAs. However, the ozonation/biological activated carbon (BAC) combined process had a better removal efficiency for DBPFP. The total DBPFP decreased remarkably from 338.7 to 113.3μg/L after the O3/BAC process, far below the separated BAC of process B (189.1μg/L).

Adsorption characteristics of Effluent Organic Matter and Natural Organic Matter by Carbon Based Nanomaterials

Natural Organic Matter (NOM) and Effluent Organic Matter (EfOM) have been regarded as the major membrane foulants in advanced water treatment or wastewater reuse processes. In this study, the adsorption of Suwannee River NOM (SRNOM) and EfOM from a wastewater treatment plant by Carbon-Based Nanomaterials (CBNs) including Single-Wall Carbon Nanotube (SWCNT), Multi-wall Carbon Nanotube (MWCNT) and Expanded Graphite (EG) was investigated to mitigate their membrane fouling potentials. Adsorption of SRNOM and EfOM showed Langmuir type adsorption with constant adsorption enthalpy, regardless of the adsorbents. MWCNT showed the highest adsorption capacity for SRNOM and EfOM, while SWCNT showed the greatest reduction in Soluble Microbial Products (SMP) in EfOM. The UV/Vis spectrophotometry, fluorescence spectrophotometry, and size exclusion chromatography showed that high molecular weight fraction of SRNOM and EfOM was preferentially adsorbed onto ordered CBNs such as SWCNT, MWCNT, and EG. It was also evidenced that SMP adsorptions by SWCNT was significantly higher than those by MWCNT. The results imply that a pretreatment with SWCNT or EG can reduce membrane fouling via adsorption of SMP and high molecular weight organic fractions in EfOM.

대청호 추동취수탑 부근의 수질변화 특성

AbstractThis study has been carried out to provide the basic data obtained from the evaluation of the variation of water quality around the Chudong intake tower in Daechung resevoir, which may be able to help the establishment of a pure water supply policy. Five sites around the Chudong intake tower were selected, and the average data for recent ten years(from year 2004 to year 2013) were analysed. The average water quality around Chudong intake tower are as followed; pH 7.5, DO 8.7 mg/L, BOD 1.0 mg/L, COD 3.0 mg/L, SS 3.0 mg/L, TN 1.495 mg/L, TP 0.017 mg/L, and Chlorophyll-a 6.5 mg/m 3 were matched the good class by comparing with the living environment standard of reservoir. COD values of higher than 3.0 mg/L after July were likely due to non-point pollutants and algae outbreak during rainy summer season. Total phosphorus rose sharply in the summer season, and then algae watch was issued consistently for average 40 days. Total nitrogen to total phosphorus ratio was average 90, and it is important to control the inflow phosphrous from small stream for proper management to block an algae growth according to eutrophication. It was recommended to operate the algae removing boats around intake tower from July to October, and was required advanced water treatment processes to remove NBD COD and bad odor and taste due to algae growth. Key words:Algae watch, Chudong intake tower, Management to block algae growth, Total nitrogen to total phosphorus ratio

Public Perceptions of Direct Potable Reuse in Four US Cities

This work is motivated by technical advancements related to direct potable reuse (DPR) and the importance of public values when considering alternative water resources. This study involved the distribution of an online survey to residents in four US cities about existing tap water supplies and “purified water,” defined as “municipal wastewater that has undergone advanced water treatment processes, thus resulting in water quality that, at a minimum, complies with drinking water regulations.” Overall, 50–60% of respondents were in support of using purified water as potable water. Contaminant concerns were highest for taste/smell and microbial contaminants in both current tap water and purified water. Survey results highlight the importance of addressing certain areas when communicating about DPR to the public, such as barriers against microbial contamination, the trustworthiness of utilities, potential improvements over the status quo, and community‐specific drivers that necessitate the use of purified water in a given setting.

고도처리공정에서 다양한 수질에 따른 미량유기오염물질 제거특성

고도처리공정에서 다양한 수질에 따른 미량유기오염물질 제거특성