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Biostable drinking water, which limits bacterial growth and community changes, is obtained by removing bacterial growth-promoting nutrients, such as assimilable organic carbon (AOC), through a range of treatment processes. To date, various controlled laboratory bacterial growth tests have been developed using different inoculum types to study the growth-promoting nutrients in water. However, many countries have not considered limiting bacterial growth by reducing the growth-promoting nutrients in drinking water, because they primarily use chlorine in their distribution systems. This review provides an overview of the available methods to analyze dissolved growth-promoting nutrients in water and summarizes the current knowledge on nutrient characteristics and concentrations in water from source to tap, through various treatment processes. Bacterial growth-promoting nutrients in surface water are affected by seasonal variables, such as water temperature, precipitation, and algal blooms. The use of groundwater, bank filtration, and artificial recharge of water sources provide low bacterial growth-promoting nutrient concentrations in drinking water. The treatment type as well as operational conditions significantly affect biostable drinking water production. To achieve water biostability, it is important to understand not only the water treatment process but also the distribution conditions, including the impact of pipe materials on the nutrient levels in water. The impact of climate change on biostability as well as the role of complex and particle bound nutrients on microbial growth in drinking water distribution systems should be investigated in future studies.

In this study, the effects of algal organic matter (AOM) from Microcystis aeruginosa on the attenuation of selected trace organic contaminants (TrOCs) were observed in managed aquifer recharge using laboratory scale soil columns. Changes in dissolved organic matter and bacteriological characteristics were also investigated to elucidate the performance of managed aquifer recharge during algal bloom. AOM exhibited a high ratio of biopolymers and low molecular weight neutrals in dissolved organic matter. Dissolved organic matter was effectively removed even after the addition of AOM (4 mg L−1) in the feed water during soil passage; however, the removal rate was significantly reduced under abiotic conditions, confirming that the main removal mechanisms of dissolved organic matter involve biodegradation. AOM exhibited a much higher ratio of assimilable organic carbon/dissolved organic carbon than river water. Attenuation of four hydrophilic acid TrOCs (diclofenac, bezafibrate, ibuprofen, and ketoprofen) was significantly reduced in the presence of AOM during soil passage, but neutral TrOCs were not affected by AOM. It was difficult to remove carbamazepine using managed aquifer recharge. AOM influenced the attenuation of gemfibrozil, diclofenac, bezafibrate, ibuprofen, ketoprofen, carbamazepine, pentoxifylline, and phenacetin even after ozonation, followed by soil passage. Thus, it is important to monitor the removal of some TrOCs in managed aquifer recharge during algal blooms.

A hybridization of managed aquifer recharge (MAR) with pre-oxidation processes was conducted in this study to investigate changes in dissolved organic matter characteristics and the attenuation of selected trace organic contaminants (TrOCs). Potassium permanganate, chlorine, and ozone treatments were used for pre-oxidation, which effectively attenuated some TrOCs, particularly the combination of MAR with ozone achieved 84-99% attenuation. The pre-oxidation step using potassium permanganate showed high removal of carbamazepine (96%). Moreover, MAR was also combined with nanofiltration (NF) as a multi-barrier concept for the removal of persistent TrOCs after MAR. A short-chain polyfluoroalkyl substance (PFAS) was effectively removed after combining MAR columns with NF membranes. Thus, pre-oxidation coupled with MAR followed by NF could potentially enhance the removal of selected TrOCs.

A hybrid process of managed aquifer recharge with pre-oxidation was investigated as part of a multiple-barrier approach for safe water production. This study evaluated O3 and O3/H2O2 for the pre-oxidation of urban surface water prior to managed aquifer recharge (MAR) and compared their effectiveness with respect to trace organic contaminants (TrOCs), biostability, and trihalomethane formation potential. The combination of pre-oxidation and MAR was performed using long-term column studies, and the results confirmed the removal of 64 and 56% dissolved organic carbon by using O3 and O3/H2O2, respectively. MAR combined with O3 and O3/H2O2 achieved >50% removal of dissolved organic carbon with the first 5 days of residence time. O3 alone showed better performance in alleviating trihalomethane formation potential during chlorination compared to using O3/H2O2. The pre-oxidation of urban surface water was effective in attenuating selected TrOCs (35 - >99% removal), and subsequent MAR achieved >99% removal of selected TrOCs within the first 5 days, regardless of pretreatment methods examined in this study. The results of this study provide an understanding of the effects of O3 and O3/H2O2 as pre-oxidation processes on urban surface water prior to MAR, as well as the resulting impact on MAR.

Bacterial aerosols resulting from membrane bioreactor (MBR) processes, which require excessive aeration in a confined space, are important to investigate because of their possible adverse effects on human health. This study investigated the influence of solid retention time (SRT) on bacterial aerosols from MBRs. Moreover, powdered activated carbon (PAC) and calcium were used to attenuate bacterial aerosol emissions from MBRs. The particulate matter (PM) emitted from the MBRs was reduced by 30.5 and 25.2% at SRTs of 20 and 80 d, respectively, compared to the level emitted at an SRT of 10 d. Total cell counts were similarly reduced at SRTs of 20 and 80 d. Longer SRTs also led to greater reductions in the particle size distribution of the sludge within 10 μm. Several factors in the MBR influenced the behavior of the bacterial aerosol emissions from the MBRs. This study showed that changes in viscosity and particle size induced by the SRT influenced the bacterial aerosol emissions in MBRs. Therefore, SRT was identified as an important design parameter affecting bacterial aerosol emissions in MBR processes. The amounts of particulate matter and bacterial aerosols were reduced in MBRs using PAC and calcium, both of which exerted an immediate effect on the bacterial aerosol emissions in MBRs by increasing the aerosol-particle size.

This study evaluated the performance of a pilot-scale hybrid constructed wetland system for secondary effluent and investigated bulk organic matter characteristics. The hybrid constructed wetland consisted of a vertical-flow (VF) bed followed by a horizontal-flow (HF) bed. We also investigated the effects of hydraulic loading rates and influent organic load on the performance of the pilot-scale VF-HF hybrid constructed wetland. The results showed a high removal efficiency for suspended solids (>95%) and organic matter as determined by total organic carbon (>98.5%) and dissolved organic carbon (>70%), but no significant change in nitrogen removal was observed. The wetland treatment efficiency for suspended solids and organic matter showed a good buffer capacity even when hydraulic loading rates increased from 750 to 1500 L m−2 d−1 and 500–1000 L m−2 d−1 during the VF and HF stages, respectively. Moreover, there was no significant change in the performance when influent organic load increased eight-fold. Fluorescence excitation-emission matrix and liquid chromatography-organic carbon detection (LC-OCD) were used to investigate the dissolved organic matter characteristics in the hybrid VF-HF constructed wetland. Fluorescence excitation-emission matrix spectroscopy showed that both protein- and humic-like substances did not significantly change in the effluent when hydraulic loading rates and organic load increased by two- and eight-fold, respectively. Biopolymers determined using LC-OCD were effectively removed via the VF and HF stage wetlands, indicating the occurrence of biodegradation. Fluorescence excitation-emission matrix spectroscopy and LC-OCD provided the fate of dissolved organic matter characteristics in the hybrid VF-HF constructed wetland.

This study is the first to demonstrate the capability of Cl– to markedly accelerate organic oxidation using thermally activated peroxymonosulfate (PMS) under acidic conditions. The treatment effici...

Biofilm formation has been frequently identified as a pathway of nosocomial infection in polymeric tubes used for patients of all ages. Biofilm formation on tube surfaces can lead to hygienic failure and cause diarrhea, stomach pain, inflammation, and digestive system disease. This study investigated the influence of polymeric tube materials in contact with water on the biomass formation potential and migration potential of microbially available carbon from plasticizers using a BioMig test. The thermoplastic elastomer tube, which is reusable, leached a relatively low amount of assimilable organic carbon to water. In contrast, the assimilable organic carbon migration potential of polyurethane was the most significant, 6-fold greater than that of the thermoplastic elastomer. Moreover, the same materials (e.g., silicone) produced via different manufacturing processes showed significant differences in migration behaviors. The potential biomass formation observed in polyurethane was approximately 7 × 109 cells cm−2 for both Aeromonas hydrophila and Escherichia coli strains. This study highlights the importance of choosing the correct material characteristics of polymeric tubes in contact with water to protect them from bacterial contamination. Therefore, manufacturers can use the BioMig test to evaluate and produce more hygienic and biostable tubes.

In this study, the feasibility of the membrane distillation (MD) process as a wastewater reclamation system for portable reuse was investigated. The flux was stably maintained at about 20 L/m2h (LMH) at ΔT 30 °C, compared to higher flux at ΔT 50 °C, which showed a rapid decrease in the flux due to severe fouling. MD produced excellent quality of potable water satisfied the drinking water standards of Korea from effluent of sewage treatment plant (ESTP). The fractions of the hydrophobic OC (HOC) and chromatographic DOC (CDOC) from LC-OCD analysis was firstly suggested to understand different organic transport during the MD process. The transport of organic matters across the MD membrane mitigated at low operation temperature and the transported organics in all the tested waters were mostly volatile low molecular weight organics, aromatic amino acids. All of thirteen selected pharmaceuticals were completely removed by MD, regardless of their properties. In order to retard the membrane fouling of the MD process, coagulation and filtration pre-treatments were applied. The pre-treatment process coupled MD process could successfully remove impurities including NH4-N without severe membrane fouling. Moreover, coagulation pretreatment reduced transport of ammonia due to decrease in pH.

This study achieves a better understanding how Scenedesmus quadricauda microalgae participate in the phycoremediation of a reverse osmosis (RO) concentrate at a high salinity (8000 mg Cl− L− 1). Algal treatment of the RO concentrate under continuous illumination resulted in a notable increase in the biodegradability of dissolved organic matter, subsequent removal of biodegradable fractions, and simultaneous removal of nutrients (N and P). This is the first time that S. quadricauda is shown to induce the degradation of polymeric organic matter in the RO concentrate, which is typically refractory to microbial decomposition. In this study, the mechanisms for algae-induced degradation were investigated by measuring the hydrogen peroxide (H2O2) released out of algal cells and dispersed in the aqueous phase. The algae-induced biodegradation process has an advantage over typical electrochemical oxidation technologies in that photo-sensitive living organisms are capable of self-repair, reproduction, and nutrient uptake. Our results indicate that the use of algae-induced oxidation is highly feasible as a safe, inexpensive technology to pre-treat non- or slowly-biodegradable organic matter in wastewater prior to downstream biological processing.

This study investigated the role of soil mixture blocks (SMBs) in the removal of trace organic contaminants and the changes in dissolved organic matter characteristics in a laboratory-scale multi-soil-layering (MSL) system. The experimental setup included three soil-based water treatment systems, namely MSL, MSL without SMBs (zeolite/slag), and a sand filter. The effect of SMBs in the removal of dissolved organic matter in MSL was not significant, but the use of zeolite/slag in MSL enhanced the removal of humic substances and building blocks. Through membrane fractionation, the size distribution of dissolved organic matter in the MSL system was not changed, and the majority of the dissolved organic matter is below 1 kDa. Ten pharmaceutically active compounds and three endocrine-disrupting compounds were used to investigate the removal of selected trace organic contaminants in the MSL system, zeolite/slag, and sand filter. The attenuation of pentoxifylline, caffeine, 17α-ethinylestradiol, estrone, and 17β-estradiol in the MSL system was similar to that for zeolite/slag, and the removal efficiency was greater than 80%. However, pentoxifylline, caffeine, 17α-ethinylestradiol, estrone, and 17β-estradiol exhibited relatively low removal efficiencies in the sand filter compared to those in the MSL system and zeolite/slag. Results from this study provide insight into the removal of selected trace organic contaminants in MSL system, which could be considered as one of the series of barriers to remove trace organic contaminants in wastewater.

In this study, natural organic matter (NOM) characteristics were investigated over three years of monthly monitoring to determine the effect of seasonal variations on NOM levels from source to tap. Liquid chromatography with organic carbon detection (LC-OCD) was used to determine NOM characteristics and the level of reduction of biodegradable dissolved organic carbon (BDOC). The average dissolved organic matter concentration in the source water (Lake Paldang, Korea) was not significantly different between summer and winter. However, the distribution of NOM components, such as biopolymers, building blocks, low molecular weight (MW) neutrals and acids, identified by LC-OCD, varied seasonally. While high MW NOM was preferentially removed by coagulation/sedimentation/rapid sand filtration (CSR), no seasonal effects were observed on the removal of high MW NOM. CSR and biological activated carbon (BAC) filtration showed a better efficiency of BDOC removal in winter and summer, respectively. High concentrations of chlorine used in the treatment plants in summer resulted in 10% higher DOC concentrations during disinfection. Overall NOM removal efficiencies from source to tap were 45% and 35% for summer and winter, respectively. Principal component analysis also indicated that seasonal variations (principal component 1) showed the strongest positive correlation with the overall performance of water treatment. The long-term monitoring of drinking water treatment processes showed that seasonal variations were important factors affecting NOM characteristics during water treatment.

This study investigated the effect of powdered activated carbon and calcium on trihalomethane toxicity in zebrafish embryos and larvae in hybrid membrane bioreactors. Two hybrid membrane bioreactors were configured with the addition of powdered activated carbon or calcium to reduce the trihalomethane formation potential. Trihalomethane formation decreased by approximately 37.2% and 30.3% in membrane bioreactor-powdered activated carbon and membrane bioreactor-calcium, respectively. Additionally, the toxic effect of trihalomethane formation was examined on zebrafish embryos and larvae. About 35% of the embryos exposed to trihalomethanes (800 ppb) showed signs of deformation, with the majority displaying coagulation within 24 h after exposure. Color preference tests, which were conducted to identify any abnormal activities of the embryos, showed an increase in preference from short to longer wavelengths upon exposure to high levels of trihalomethanes. This may indicate damage to the optical organs in zebrafish when exposed to trihalomethanes. Behavioral analysis showed reduced mobility of zebrafish larvae under different trihalomethane concentrations, indicating a decrease in the average activity time with an increasing trihalomethane concentration. The membrane bioreactor effluents were toxic to zebrafish embryos and larvae in the presence of high trihalomethane concentrations. To understand the mechanism behind trihalomethane toxicity, further studies are needed.

The influences of natural organic matter (NOM) and bacteriological characteristics on the biological stability of water were investigated in a full-scale drinking water treatment plant. We found that prechlorination decreased the hydrophobicity of the organic matter and significantly increased the high-molecular-weight (MW) dissolved organic matter, such as biopolymers and humic substances. High-MW organic matter and structurally complex compounds are known to be relatively slowly biodegradable; however, because of the prechlorination step, the indigenous bacteria could readily utilise these fractions as assimilable organic carbon. Sequential coagulation and sedimentation resulted in the substantial removal of biopolymer (74%), humic substance (33%), bacterial cells (79%), and assimilable organic carbon (67%). Rapid sand and granular activated carbon filtration induced an increase in the low-nucleic-acid content bacteria; however, these bacteria were biologically less active in relation to enzymatic activity and ATP. The granular activated carbon step was essential to securing biological stability (the ability to prevent bacterial growth) by removing the residual assimilable organic carbon that had formed during the ozone treatment. The growth potential of Escherichia coli and indigenous bacteria were found to differ in respect to NOM characteristics. In comparison with E. coli, the indigenous bacteria utilised a broader range of NOM as a carbon source. Principal component analysis demonstrated that the measured biological stability of water could differ, depending on the NOM characteristics, as well as on the bacterial inoculum selected for the analysis.

Biofilm formation on biofilters can influence their hydraulic performance, thereby leading to head loss and an increase in energy use and costs for water utilities. The effects of a range of factors, including hydrogen peroxide and phosphate, on the performance of biological activated carbon (BAC) and biofilm formation were investigated using laboratory-scale columns. Head loss, total carbohydrates, and proteins were reduced in the nutrient-enhanced, oxidant-enhanced, and nutrient + oxidant-enhanced BAC filters. However, there were no changes in the removal of dissolved organic matter, trihalomethane formation potential, or selected trace organic contaminants. The biofilm formation on polyvinyl chloride and stainless steel coupons using the laboratory biofilm reactor system was lower when the effluent from a nutrient-enhanced column was used, which indicated that there was less biofilm formation in the distribution systems. This may have been because the effluent from the nutrient-enhanced column was more biologically stable. Therefore, enhanced biofiltration could be used not only to reduce head loss in biofilters, but also to delay biofilm formation in distribution systems.

This study achieves a better operational simplicity for the phycoremediation of reverse osmosis (RO) concentrate using Scenedesmus quadricauda microalgae. Under continuous illumination with CO2 supplementation, algal growth in the RO concentrate resulted in a conversion of polymeric organic matter (a mixture of humic substances and polysaccharides) to biodegradable fractions and their prompt removal along with inorganic nutrients (NO3- and PO43-). The algal-induced degradation of humic-like substances which are typically refractory to microbial decomposition was demonstrated in an indirect manner. In this study, we also investigated the effects of algal treatment on the growth of Escherichia coli and removal of trace organic compounds (TOrCs) from the RO concentrate. Our results indicate that algal treatment of the RO concentrate using aeration with 10% (v/v) CO2 under continuous illumination is highly feasible as a safe and inexpensive technology to remove non- or slowly-biodegradable organic matter, reduce enteric bacteria, and attenuate TOrCs in wastewater. However, the results should not be generalized, but critically discussed, due to limitations of using the synthetic RO concentrate in evaluating the performance of wastewater remediation with microalgae.

The diversity of organic micropollutants (OMPs) in aquatic environments has been increasing rapidly during the last decade. Therefore, it is important to monitor and attenuate emerging contaminants before they can negatively affect the aquatic environment. However, due to the diversity and complexity of OMPs, there are limitations to using a single method for treating a combination of these pollutants. To address this issue, a mobile water treatment system (MWTS) equipped with different treatment units was designed to remove OMPs under field conditions. The MWTS was configured with various modular units including coagulation, flocculation, dissolved air flotation, membrane filtration, ozone oxidation, granular activated carbon, and UV disinfection. Each treatment unit could be operated either individually or in different combinations to identify the optimal configuration of treatment units for the removal of OMPs. To investigate the effectiveness of the MWTS, twelve OMPs were selected and introduced simultaneously into the feed water samples collected from different rivers throughout Korea. The current study proved that the MTWS is an effective solution to treat OMPs and is a time saving treatment system. The combined effects of the different treatment units removed over 99% of the selected OMPs, regardless of their physicochemical properties. Moreover, since the system is mobile, on-site analyses can be conducted to identify the most effective treatment method and configuration for each OMP.

Nanoparticle toxicity to biological activities in activated sludge is largely unknown. Among the widely used nanoparticles, silica nanoparticles (SNP) have a limited number of studies associated with inhibition to the activated sludge process (ASP). We demonstrated SNP inhibition of activated sludge respiration through oxygen uptake rate (OUR) measurement. Based on the percentage inhibition of total oxygen consumption (IT), we observed that smaller SNPs (12 nm, IT = 33 ± 3%; 151 nm, IT = 23 ± 2%) were stronger inhibitors than larger SNPs (442 and 683 nm, IT = 5 ± 1%). Transmission electron micrographs showed that some of the SNPs were adsorbed on and/or apparently embedded somewhere in the microbial cell membrane. Whether SNPs are directly associated with the inhibition of total oxygen uptake warrants further studies. However, it is clear that SNPs statistically significantly altered the composition of microbial membrane lipids, which was more clearly described by principal component analysis and weighted Euclidian distance (PCA-ED) of the fatty acid methyl ester (FAME) data. This study suggests that SNPs potentially affect the biological activity in activated sludge through the inhibition of total oxygen uptake.

In this study, the organic components were identified that are mainly responsible for the formation of disinfection byproducts (DBPs) and for the biostability of urban surface water. The compositional distribution of dissolved organic matter (DOM) was strongly associated with the potential for both DBP formation and bacterial growth. Further evaluation was carried out (1) to compare the potential for DBP formation upon chlorination of treated water, (2) to determine the biostability that might result from minimizing assimilable organic carbon (AOC), and (3) to use laboratory-scale soil-column experiments to compare the effects of removal of trace organic chemicals (TOrCs) between managed aquifer recharge (MAR) hybrid systems (such as bank filtration followed by artificial recharge and recovery: ARR), and ozonation followed by ARR. Our fractionation and removal methods provided useful insights into the removal of problematic organic components using MAR hybrid systems. Pretreatment with a small amount of ozone (∼0.7 mg-O 3 mg-C −1 ) resulted in improved ARR performance, especially from removing organic acids from DOM, which substantially decreased the potential for DBP formation, while the robust removal of AOC was attributed to a significant decrease in non-acidic and more hydrophilic fractions during soil passage. Both pretreatments used in this study were effective in the removal of selected TOrCs, but carbamazepine was persistent during soil passage. The pretreatment, which used ozonation before ARR, significantly enhanced the removal of carbamazepine; therefore, ozonation followed by ARR is considered an effective way to enhance removal of persistent compounds.

Two different quaternary amine polymers were examined as primary coagulants for the removal of natural organic matter (NOM) and concurrent production of flocs favorable for downstream membrane separation. The primary issue explored was the relationship between various coagulation conditions on the floc characteristics and the subsequent performance of microfiltration when filtering coagulated NOM. The size distribution and morphological properties of flocs formed through the coagulation of NOM were characterized and the effects of polymer type and dose on these characteristics were also examined. Coagulation of NOM using polydiallyldimethyl-ammonium chloride (pDADMAC) produced looser and less settleable flocs compared to dosing the equivalent amount of epichlorohydrin/dimethylamine (epi/DMA). This was associated with the formation of a relatively denser cake layer on the top of the membrane for the filtration of NOM coagulated with epi/DMA. The charge neutralization coagulation condition with the polymers removed almost all of the fouling tendency that had occurred when filtering raw NOM. The median diameter and the fractal dimension of the flocs produced increased as the zeta potential approached zero, which resulted in the formation of a cake layer that was easily removed from the surface of the membrane.

Laboratory-scale batch and soil columns experiments were conducted to investigate the attenuation of estrogens (17β-estradiol and 17α-ethinylestradiol) during managed aquifer recharge. The role of microbial activity in the removal of selected estrogens was evaluated by comparing the results from biotic and abiotic batch experiments. Moreover, batch experiments were carried out using the sand media prepared over different acclimation periods to investigate the impact of acclimation periods on the removal of selected estrogens. Batch studies showed that adsorption was the dominant removal mechanism in the removal of 17β-estradiol and 17α-ethinylestradiol. 17β-estradiol and 17α-ethinylestradiol were attenuated by 99% and 96%, respectively, in batch experiments under oxic conditions. Redox conditions did not show any significant effect on the attenuation of 17β-estradiol. However, the net estrogenicity of 17β-estradiol remaining was lower under oxic conditions (130 ng estradiol-equivalents/L) than anoxic conditions (970 ng estradiol-equivalents/L). Column studies operated at 17 h of empty bed contact time also demonstrated that removal mechanism of 17α-ethinylestradiol was more dependent on adsorption than biodegradation.

Organic micropollutants (OMPs) represent a major constraint in drinking water supply. In the past, emphasis has been on individual treatment processes comprising conventional treatment (coagulation, sedimentation, and filtration) followed by advanced treatment processes (adsorption, ion-exchange, oxidation, and membrane separation). With the depletion of water resources and high demand for power and chemical usage, efforts need to be made to judiciously use advanced treatment processes. There is a new interest in multiple barriers with synergies in which two coupled processes can function as a hybrid process. Within the context of this paper, the hybrid processes include a natural treatment process coupled with an advanced process. Pilot/full-scale studies have shown efficient removal of OMPs by these hybrid processes. With this hybridization, the usage of resources such as power and chemicals can be reduced. In this study, coupling/hybridization of aquifer recharge and recovery (ARR) with oxidation (O3), advanced oxidation process which involves OH radicals (AOP), nanofiltration (NF), reverse osmosis (RO) and granular activated carbon (GAC) adsorption for OMP removal was studied. O3 or AOP as a pre-treatment and GAC, NF, RO, or UV/chlorination as a post-treatment to ARR was studied. NF can be replaced by RO for removal of OMPs since studies have shown similar performance of NF to RO for removal of many OMPs, thereby reducing costs and providing a more sustainable approach.

Three identical bench-scale membrane bioreactors (MBRs) were operated to investigate the formation of effluent organic matter (EfOM) via biodegradation at different solid retention times (8, 20 and 80 days). The characteristics of organic matter in supernatants, bound extracellular polymeric substances (EPS), soluble microbial products (SMP) and effluents changed at different solid retention times (SRTs). EfOM characteristics affecting membrane fouling with respect to total hydraulic resistances and specific cake resistances were investigated using advanced organic characterization tools. EfOM characteristics determined by size exclusion chromatography with organic carbon detection, fluorescence excitation–emission matrix spectroscopy and polarity rapid assessment method were compared with the membrane fouling. In this study, a database collected from three identical bench-scale MBRs operated at different SRTs for 12 months is analyzed to investigate the intercorrelations (either positive or negative) between EfOM characteristics and membrane fouling using principal component analysis (PCA). Principal component-1 embodied the characteristics of EfOM (i.e., aliphatic biopolymers vs. aromatic humic substances), and explained 59% of the data variability. This study provides useful data on EfOM characteristics with membrane fouling, and a multivariate statistical analysis (PCA) can be used to depict the intercorrelations between EfOM characteristics and SRTs in MBRs.

This study mainly evaluated the effectiveness of ozonation toward the enhancement of the removal efficiencies of antibiotic-resistant bacteria (ARB), pB10 plasmid transfer, and pB10 plasmids under different pH and suspended solids (SS) and humic acid concentrations. First, chlorination was tested as a reference disinfection process. Chlorination at a very high dose concentration of Cl2 (75 mg L(-1)) and a long contact time (10 min) were required to achieve approximately 90% ARB and pB10 plasmid transfer removal efficiencies. However, even these stringent conditions only resulted in a 78.8% reduction of pB10 plasmid concentrations. In case of ozonation, the estimated CT (concentration × contact time) value (at C0 = 7 mg L(-1)) for achieving 4-log pB10 plasmid removal efficiency was 127.15 mg·min L(-1), which was 1.04- and 1.25-fold higher than those required for ARB (122.73 mg·min L(-1)) and a model nonantibiotic resistant bacterial strain, E. coli K-12, (101.4 mg·min L(-1)), respectively. In preventing pB10 plasmid transfer, ozonation achieved better performance under conditions of higher concentrations of humic acid and lower pH. Our study results demonstrated that the applicability of CT concept in practice, conventionally used for disinfection, might not be appropriate for antibiotic resistance control in the wastewater treatment process. Further studies should be conducted in wastewater engineering on how to implement multiple barriers including disinfection to prevent ARB and ARG discharge into the environment.

Phosphorus removal has been studied for decades to reduce the environmental impact of phosphorus in natural waterbodies. Slag has been applied for the phosphorus removal by several mechanisms. In this study, sodium hydroxide coating was applied on the slag surface to enhance the efficiency of precipitation-coagulation process. In the batch test, it was found that the capacity of the slag to maintain high pH decreases with increasing its exposure time to the aqueous solution. In the column test, the coarse-grained coated slag showed higher phosphorus removal efficiency than the fine-grained uncoated slag. The coated slag maintained pH higher than uncoated slag and, accordingly, the removal efficiency of phosphorus was higher. Especially, when pH was less than 8, the removal efficiency decreased significantly. However, coated slag provided an excess amount of aluminum and sodium. Thus, a return process to reuse aluminum and sodium as a coagulant was introduced. The return process yields longer lifespan of slag with higher phosphorus removal and lower concentration of cations in the effluent. With the return process, the phosphorus removal efficiency was kept higher than 60% until 150 bed volumes; meanwhile, the efficiency without return process became lower than 60% at 25 bed volumes.

Soil column experiments were conducted to investigate the effects of effluent organic matter (EfOM) characteristics on the removal of bulk organic matter (OM) and pharmaceutically active compounds (PhACs) during managed aquifer recharge (MAR) treatment processes. The fate of bulk OM and PhACs during an MAR is important to assess post-treatment requirements. Biodegradable OM from EfOM, originating from biological wastewater treatment, was effectively removed during soil passage. Based on a fluorescence excitation-emission matrix (F-EEM) analysis of wastewater effluent-dominated (WWE-dom) surface water (SW), protein-like substances, i.e., biopolymers, were removed more favorably than fluorescent humic-like substances under oxic compared to anoxic conditions. However, there was no preferential removal of biopolymers or humic substances, determined as dissolved organic carbon (DOC) observed via liquid chromatography with online organic carbon detection (LC-OCD) analysis. Most of the selected PhACs exhibited removal efficiencies of greater than 90% in both SW and WWE-dom SW. However, the removal efficiencies of bezafibrate, diclofenac and gemfibrozil were relatively low in WWE-dom SW, which contained more biodegradable OM than did SW (copiotrophic metabolism). Based on this study, low biodegradable fractions such as humic substances in MR may have enhanced the degradation of diclofenac, gemfibrozil and bezafibrate by inducing an oligotrophic microbial community via long term starvation. Both carbamazepine and clofibric acid showed persistent behaviors and were not influenced by EfOM.

Organic micropollutants (OMPs) are detected in sources for drinking water and treatment possibilities are investigated. Innovative removal technologies are available such as membrane filtration and advanced oxidation, but also biological treatment should be considered. By combining an advanced oxidation process with managed aquifer recharge (MAR), two complementary processes are expected to provide a hybrid system for OMP removal, according to the multiple barrier approach. Laboratory scale batch reactor experiments were conducted to investigate the removal of dissolved organic carbon (DOC) and 14 different pharmaceutically active compounds (PhACs) from MAR influent water and water subjected to oxidation, under different process conditions. A DOC removal of 10% was found in water under oxic (aerobic) conditions for batch reactor experiments, a similar value for DOC removal was observed in the field. Batch reactor experiments for the removal of PhACs showed that the removal of pharmaceuticals ranged from negligible to more than 90%. Under oxic conditions, seven out of 14 pharmaceuticals were removed over 90% and 12 out of 14 pharmaceuticals were removed at more than 50% during 30 days of experiments. Under anoxic conditions, four out of 14 pharmaceuticals were removed over 90% and eight out of 14 pharmaceuticals were removed at more than 50% over 30 days' experiments. Carbamazepine and phenazone were persistent both under oxic and anoxic conditions. The PhACs removal efficiency with oxidized water was, for most compounds, comparable to the removal with MAR influent water.

Soil aquifer treatment (SAT) is a cost-effective natural wastewater treatment and reuse technology. It is an environmentally friendly technology that does not require chemical usage and is applicable to both developing and developed countries. However, the presence of organic matter, nutrients, and pathogens poses a major health threat to the population exposed to partially treated wastewater or reclaimed water through SAT. Laboratory-based soil column and batch experiments simulating SAT were conducted to examine the influence of temperature variation and oxidation–reduction (redox) conditions on removal of bulk organic matter, nutrients, and indicator microorganisms using primary effluent. While an average dissolved organic carbon (DOC) removal of 17.7 % was achieved in soil columns at 5 °C, removal at higher temperatures increased by 10 % increments with increase in temperature by 5 °C over the range of 15 to 25 °C. Furthermore, soil column and batch experiments conducted under different redox conditions revealed higher DOC removal in aerobic (oxic) experiments compared to anoxic experiments. Aerobic soil columns exhibited DOC removal 15 % higher than that achieved in the anoxic columns, while aerobic batch showed DOC removal 7.8 % higher than the corresponding anoxic batch experiments. Ammonium-nitrogen removal greater than 99 % was observed at 20 and 25 °C, while 89.7 % was removed at 15 °C, but the removal substantially decreased to 8.8 % at 5 °C. While ammonium-nitrogen was attenuated by 99.9 % in aerobic batch reactors carried out at room temperature, anoxic experiments under similar conditions revealed 12.1 % ammonium-nitrogen reduction, corresponding to increase in nitrate-nitrogen and decrease in sulfate concentration.

Managed aquifer recharge is a robust barrier in the multi-barrier approach to supply safe drinking water. The removal performance of gesomin and 2-methylisoborneol through managed aquifer recharge was investigated using batch and column experiments. Batch experiments were carried out to investigate the removal of geosmin and 2-methylisoborneol (MIB) in the presence of different types of biodegradable organic matter using different types of water. Five different types of water spiked with 70–293 ng/L of geosmin and MIB were used in batch reactors, and complete removal of geosmin and MIB (down to the detection limit) was achieved in all cases. Soil column studies showed that biodegradation contributed to the removal of geosmin and MIB by 23 and 31%, respectively (empty bed contact time: 17 hours). The removal of geosmin and MIB appeared to be influenced more by microbial activity than the initial concentrations of geosmin and MIB. Adsorption was found to be the dominant mechanism (major role) followed by biodegradation (minor role) for geosmin and MIB removals during soil passage. Managed aquifer charge can therefore be used as a robust barrier to remove taste and odor (T&O) causing compounds.

Natural water treatment systems such as bank filtration have been recognized as providing effective barriers in the multi-barrier approach for attenuation of organic micropollutants for safe drinking water supply. In this study, the role of biodegradation in the removal of selected pharmaceutically active compounds (PhACs) during soil passage was investigated. Batch studies were conducted to investigate the removal of 13 selected PhACs from different water sources with respect to different sources of biodegradable organic matter. Neutral PhACs (phenacetine, paracetamol, and caffeine) and acidic PhACs (ibuprofen, fenoprofen, bezafibrate, and naproxen) were removed with efficiencies greater than 88% from different organic matter water matrices during batch studies (hydraulic retention time (HRT): 60 days). Column experiments were then performed to differentiate between biodegradation and sorption with regard to the removal of selected PhACs. In column studies, removal efficiencies of acidic PhACs (e.g., analgesics) decreased under conditions of limited biodegradable carbon. The removal efficiencies of acidic PhACs were found to be less than 21% under abiotic conditions. These observations were attributed to sorption under abiotic conditions established by a biocide (20 mM sodium azide), which suppresses microbial activity/biodegradation. However, under biotic conditions, the removal efficiencies of these acidic PhACs were found to be greater than 59%. This is mainly attributed to biodegradation. Moreover, the average removal efficiencies of hydrophilic (polar) neutral PhACs (paracetamol, pentoxifylline, and caffeine) with low octanol/water partition coefficients (log Kow less than 1) were low (11%) under abiotic conditions. However, under biotic conditions, removal efficiencies of the neutral PhACs were greater than 98%. In contrast, carbamazepine persisted and was not easily removed under either biotic or abiotic conditions. This study indicates that biodegradation represents an important mechanism for the removal of PhACs during soil passage.

Dunea, the drinking water company for The Hague and surroundings, has as objective the production of drinking water of impeccable quality, particularly with respect to organic micropollutants. As organic micropollutants are only a minor part of the total natural organic matter, a challenge is posed in targeting the removal of a very small, specific part of the DOC, without removing all of the natural organic matter. In addition, organic micropollutants encompass a broad range of physicochemical properties, which make their removal by a single treatment step impossible. Combining AOP with artificial recharge and recovery, two complementary processes are expected to provide a hybrid system for organic micropollutant removal, according to the Dutch multiple barrier approach. Pilot-scale experiments with O3 and different advanced oxidation processes (UV/H2O2, UV/O3 and O3/H2O2) were carried out in cooperation between Dunea and ITT Wedeco. The pilot installation had a capacity of about 0.5–2.0 m3/h, with a varying LP-UV-dose, ozone dose and peroxide dose. Atrazine, isoproturone, carbamazepine, diclofenac and ibuprofen are well removed by UV/H2O2 as well as by O3/H2O2. In general, O3/H2O2 is a more energy efficient process compared to UV/H2O2. MTBE is best removed by O3/H2O2, Amidotrizoic acid and iohexol are best removed by UV/H2O2.

Natural organic matter (NOM) occurs throughout the hydrologic cycle, varying in both amount and character. In this paper, a description of NOM in surface and drinking water, in groundwater and in seawater is presented. Water samples representing these environments were collected and characterized using multiple NOM characterization techniques, including fluorescence excitation emission matrices (F-EEM) and size exclusion liquid chromatography with organic carbon detection (LC-OCD). The results show that the raw surface water as well as the treated water comprises mainly (>70%) of humic substances. The biopolymers, which are more readily biodegradable, contribute up to 2% of the NOM in the raw water but this is completely removed after treatment. For sea water samples, humic substances represent about 50% of the dissolved organic carbon concentration (DOC), while the fraction with size bigger than 20 kDa (biopolymers) represents about 7%. During soil passage, there was preferential removal of non-humic substances (i.e., biopolymers) from wastewater effluent-impacted surface water while the specific ultraviolet absorbance (SUVA), which reflects the aromatic characteristics of organics in a sample, showed an increasing trend along the depth of the soil column. This is a consequence of the removal of non-humic substances (biopolymers) which results in an increase in aromaticity.

Soil column (SC) experiments were conducted to investigate the feasibility of using silver nanoparticles (AgNPs) as microbial inhibitors; the microbial viability affecting the degradation of pharmaceutically active compounds (PhACs) and the characteristics of organic matter during managed aquifer recharge were specifically evaluated. Natural surface water samples treated with AgNPs (0, 2.5, 5, and 10 mg L − 1 ) were continually fed into the soil columns for 2 years. The adverse impact of AgNPs on the cell membrane integrity and microbial enzymatic activity was quantitatively determined using flow cytometry and adenosine triphosphate analysis. The increase in AgNP concentration in the feed water (up to 10 mg L − 1 ) resulted in a corresponding deterioration in the performance of the managed aquifer recharge (MAR), with respect to the removal of organic carbon, oxidation of nitrogenous compounds, and PhAC attenuation. The fluorescence excitation–emission matrices of feed water and treated water showed the favorable removal of protein-like substances compared to humic-like substances regardless of the AgNP concentrations; however, the extent of removed fractions decreased noticeably when the microbial viability was lowered via AgNP treatment. The biological oxidation of organic nitrogen was almost completely inhibited when 10 mg L − 1 AgNP was added during soil passage. The attenuation of bezafibrate, ketoprofen, diclofenac, clofibric acid, and gemfibrozil was strongly associated with the significant deterioration in biodegradation as a result of AgNP activity.

Wastewater effluents have recently gained a great deal of attention as a new water resource due to the increasing fresh water demand in Korea. The color content was one of the troublesome parameter...

A pilot-scale sludge treatment plant was built to investigate the feasibility of ozonation processes for waste activated sludge treatment. Ozonation of wastewater sludge resulted in mass reduction by mineralization as well as by supernatant and filtrate recycle. Another advantage of sludge ozonation is a significant improvement of settleability and dewaterability. Experimental results showed that mass reduction of 70% and volume reduction of 85% compared with the control sludge was achieved through the sludge ozonation at a dose of 0.5 gO3/gDS. It is also interesting to note that the filterability deteriorates up to ozone dose of 0.2 gO3/gDS and then improves considerably at a higher ozone dose. The filterability could be improved by chemical conditioning even at a low ozone dose. The economic feasibility by cost analysis reveals that ozonation processes can be more economical than other alternative processes for sludge treatment and disposal at small-sized wastewater treatment plants.

The feasibility of ozone treatment of municipal sludge for sludge reduction and carbon source production has been investigated. Significant accumulation of solubilized organics and unsettlable micro-solids (UMS) was observed at relatively low ozone dosages while mineralization became dominant at higher dosages. Batch denitrification experiments showed that the solubilized organics and the UMS could be utilized as carbon sources for nitrogen removal. In terms of overall sludge reduction, 54% reduction of the total sludge mass could be achieved by ozone treatment at 0.2 g-O3/g-MLSS.

Injecting acetate into the sludge layer during the settling and decanting periods was adopted to enhance phosphorus release inside the sludge layer during those periods and phosphorus uptake during the subsequent aeration period in a KIST Intermittently Decanted Extended Aeration (KIDEA) process. The relationship among nitrification, denitrification and phosphorus removal was investigated in detail and analyzed with a qualitative floc model. Dependencies of nitrification on the maximum DO level during the aerobic phase and phosphorus release on residual nitrate concentration during the settling phase were significant. High degree of nitrification resulted that phosphorus release inside the sludge layer was significantly interfered with nitrate due to the limitation of available acetate and the carbon sources from influent. Such limitation was related to the primary utilization of organic substance for denitrification in the outer layer of the floc and the retarded mass transfer into the inner layer of the floc. Nevertheless, effects of acetate injection on both denitrification and phosphorus release during the settling phase were significant. Denitrification rate after acetate injection was two times as high as that before acetate injection, and phosphorus release reached about 14 mg PO43--P/g MLVSS/hr during the decanting phase after the termination of denitrification inside the sludge layer. Extremely low level of maximum DO (around 0.5 mg/L) during the aerobic phase may inhibited nitrification, considerably, and thus nearly no nitrate was present. However, the absence of nitrate increased when the phosphorus release rate was reached up to 33 mg PO43--P/g MLVSS/hr during the settling and decanting phase, and nearly all phosphorus was taken up during subsequent aerobic phase. Since the sludge layer could function as a blocking layer, phosphorus concentrations in the supernatant was not influenced by the released phosphorus inside the sludge layer during the settling and decanting period. Phosphorus removal was directly (for uptake) and indirectly (for release) dependent on the median and maximum DO concentration during the aerobic phase, and those optimal values may exist within the range from 0.2 to 0.6 mg/L and 0.4 to 1.2 mg/L, respectively.

Aerobic biodegradation of a photoprocessing wastewater (with a silver level attained after silver recovery) was assessed using fill-and-draw activated sludge reactors. The extractability of silver from the resulting waste activated sludge was also determined. Simulated, fixer-derived wastewater was fed to the activated sludge reactors at a volumetric loading level of 40% along with an organic mixture. The biodegradation of the organic mixture was not affected by the photoprocessing wastewater. Thiosulfate was completely oxidized to sulfate. Complete conversion of ammonia to nitrite was observed, but much lower levels of nitrate were detected in the fixer and fixer-plus-silver-amended reactors, as compared to the control reactor (fed only the organic mixture). Silver at an influent total silver concentration of 1.85 mg/L did not result in any adverse effects on the activated sludge process. Filtered (through a 0.2-μm membrane filter) effluent silver concentrations were below the detection limit of 0.01 mg/L. Practically, all silver was associated with the sludge solids and the mean steady-state silver content of the sludge was 1.84 mg Ag/g mixed liquor suspended solids. When fresh sludge and aerobically digested sludge solids were subjected to the toxicity characteristic leaching procedure, the resulting silver concentration was at least 40 times lower than the regulatory limit of 5 mg Ag/L.

Reduction of bulk organic matter, nitrogen, and pharmaceutically active compounds from primary effluent during managed aquifer recharge was investigated using laboratory-scale batch reactors. Biologically stable batch reactors were spiked with different concentrations of sodium azide to inhibit biological activity and probe the effect of microbial activity on attenuation of various pollutants of concern. The experimental results obtained revealed that removal of dissolved organic carbon correlated with active microbial biomass. Furthermore, addition of 2 mM of sodium azide affected nitrite-oxidizing bacteria leading to accumulation of nitrite-nitrogen in the reactors while an ammonium-nitrogen reduction of 95.5 % was achieved. Removal efficiencies of the hydrophilic neutral compounds phenacetin, paracetamol, and caffeine were independent of the extent of the active microbial biomass and were >90 % in all reactors, whereas removal of pentoxifylline was dependent on the biological stability of the reactor. However, hydrophobic ionic compounds exhibited removal efficiency >80 % in batch reactors with the highest biological activity as evidenced by high concentration of adenosine triphosphate.

Characterization of bulk organic matter and different fractions present in wastewater treatment plant effluents is important in order to understand their fate, transport, and impact during subsequent treatments for water reuse applications. Much of the existing knowledge on bulk organic matter characterization protocols of organic matter is based on drinking water. Based on the results obtained from laboratory-scale and field studies, this chapter illustrates how different state-of-the-art characterization techniques such as dissolved organic carbon, dissolved organic nitrogen, fluorescence emission excitation matrices, liquid chromatography with online organic carbon detection, and XAD fractionation can be used to differentiate natural organic matter from effluent organic matter.

Managed aquifer recharge (MAR) is a natural water treatment process that induces surface water to flow in response to a hydraulic gradient through soil/sediment and into a vertical or horizontal well. It is a relatively cost-effective, robust and sustainable technology. Detailed characteristics of bulk organic matter and the occurrence and fate of pharmaceutically active compounds (PhACs) during MAR processes such as bank filtration (BF) and artificial recharge (AR) were reviewed. Understanding the fate of bulk organic matter during BF and AR is an essential step in determining pre- and/or post-treatment requirements. Analysis of organic matter characteristics using a suite of analytical tools suggests that there is a preferential removal of non-humic substances during MAR. Different classes of PhACs were found to behave differently during BF and AR. Antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs), beta blockers, and steroid hormones generally exhibited good removal efficiencies, especially for compounds having hydrophobic-neutral characteristics. However, anticonvulsants showed a persistent behavior during soil passage. There were also some redox-dependent PhACs. For example, X-ray contrast agents measured, as adsorbable organic iodine (AOI), and sulfamethoxazole (an antibiotic) degraded more favorably under anoxic conditions compared to oxic conditions. Phenazone-type pharmaceuticals (NSAIDs) exhibited better removal under oxic conditions. The redox transition from oxic to anoxic conditions during soil passage can enhance the removal of PhACs that are sensitive to redox conditions. In general, BF and AR can be included in a multi-barrier treatment system for the removal of PhACs.

Understanding the fate of effluent organic matter (EfOM) and natural organic matter (NOM) through riverbank filtration is essential to assess the impact of wastewater effluent on the post treatment requirements of riverbank filtrates. Furthermore, their fate during drinking water treatment can significantly determine the process design. The objective of this study was to characterise bulk organic matter which consists of EfOM and NOM during riverbank filtration using a suite of innovative analytical tools. Wastewater effluent-derived surface water and surface water were used as source waters in experiments with soil columns. Results showed the preferential removal of non-humic substances (i.e. biopolymers) from wastewater effluent-derived surface water. The bulk organic matter characteristics of wastewater effluent-derived surface water and surface water were similar after 5 m soil passage in laboratory column experiment. Humic-like organic matter in surface water and wastewater effluent-derived surface water persisted through the soil passage. More than 50% of total dissolved organic carbon (DOC) removal with significant reduction of dissolved oxygen (DO) was observed in the top 50 cm of the soil columns for both surface water and wastewater effluent-derived surface water. This was due to biodegradation by soil biomass which was determined by adenosine triphosphate (ATP) concentrations and heterotrophic plate counts. High concentrations of ATP in the first few centimeters of infiltration surface reflect the highest microbial activity which correlates with the extent of DOC reduction. Good correlation of DOC removal with DO and biomass development was observed in the soil columns.

A pilot-scale facility integrated with an ozonation unit was built to investigate the feasibility of using ozone-disintegration byproducts of wasted biomass as a carbon source for denitrification. Ozonation of biomass resulted in mass reduction by mineralization as well as by ozone-disintegrated biosolids recycling. Approximately 50% of wasted solids were recovered as available organic matter (ozonolysate), which included nonsettleable microparticles and soluble fractions. Microparticles were observed in abundance at relatively low levels of ozone doses, while soluble fractions became dominant at higher levels of ozone doses in ozone-disintegrated organics. Batch denitrification experiments showed that the ozonolysate could be used as a carbon source with a maximum denitrification rate of 3.66 mg nitrogen (N)/g volatile suspended solids (VSS) x h. Ozonolysate was also proven to enhance total nitrogen removal efficiency in the pilot-scale treatment facility. An optimal chemical oxygen demand (COD)-to-nitrogen ratio for complete denitrification was estimated as 5.13 g COD/g N. The nitrogen-removal performance of the modified intermittently decanted extended aeration process dependent on an external carbon supply could be described as a function of solids retention time.