DOC Reduction Research Articles

Nanofiltration combined with ozone-based processes for the removal of antineoplastic drugs from wastewater effluents

Over the past years, there has been an increasing concern about the occurrence of antineoplastic drugs in water bodies. The incomplete removal of these pharmaceuticals from wastewaters has been confirmed by several scientists, making it urgent to find a reliable technique or a combination of techniques capable to produce clean and safe water. In this work, the combination of nanofiltration and ozone (O3)-based processes (NF + O3, NF + O3/H2O2 and NF + O3/H2O2/UVA) was studied aiming to produce clean water from wastewater treatment plant (WWTP) secondary effluents to be safely discharged into water bodies, reused in daily practices such as aquaculture activities or for recharging aquifers used as abstraction sources for drinking water production. Nanofiltration was performed in a pilot-scale unit and O3-based processes in a continuous-flow column. The peroxone process (O3/H2O2) was considered the most promising technology to be coupled to nanofiltration, all the target pharmaceuticals being removed at an extent higher than 98% from WWTP secondary effluents, with a DOC reduction up to 92%. The applicability of the clean water stream for recharging aquifers used as abstraction sources for drinking water production was supported by a risk assessment approach, regarding the final concentrations of the target pharmaceuticals. Moreover, the toxicity of the nanofiltration retentate, a polluted stream generated from the nanofiltration system, was greatly decreased after the application of the peroxone process, which evidences the positive impact on the environment of implementing a NF + O3/H2O2 process.

Disposal of MIEX desorbent at high salinity by ZVI/H2O2 Fenton-like system: Optimization, performance and mechanisms

Magnetic ion exchange resin (MIEX) pretreatment has been widely used to enhance the performance of waterworks, but the high-salinity organic desorbent produced during the resin regeneration is difficult to be safely disposed of. The present study aimed to investigate the removal of DOM and retention of salts from MIEX desorbent via zero-valent iron (ZVI)-assisted Fenton reaction. ZVI/H2O2 mediated Fenton reaction was further validated by various analytical approaches such as 3D-EEM, Molecular weight distribution, Zeta potential, size, dissolution of iron ions, etc. In batch experiments, 73.26% reduction of DOC and 97.66% of UV254 were achieved in 40 min at optimal H2O2 concentration (20 mM), 2 g/L dose of ZVI, and pH of 3, respectively. The removal of organics was ascribed to the direct oxidation of ZVI/H2O2 and flocculation of the iron released during the oxidation. It should be noted that the high concentration of Cl- in system favored the organic removal and its enhanced performance lied in the production and oxidation of HOCl/OCl-. The treated liquid can be reused to regenerate the saturated resin with only a small amount of salt supplementation to obtain a similar recovery performance to that of a freshly configured 10% NaCl solution. Moreover, the retrieval and utilization of ZVI particles and other properties of MIEX desorbent after ZVI/H2O2 treatment were all promising and up to the mark: after four reuses, the mineralization of organic matter differs by 8.81% from the first time, which could be compensated by supplying new ZVI. This research will facilitate the recycling of resin desorbate and expand the market for MIEX applications.

Ferrate-enhanced electrocoagulation/ultrafiltration system on municipal secondary effluent treatment: Identify synergistic contribution of coagulant and oxidation

Herein, we presented a ferrate-enhanced electrocoagulation/ultrafiltration (fECUF) system with three pathways of contaminants removal during the oxidation of Fe(II), realizing superior water production, excellent fouling control, and outstanding environmental risk reduction in municipal wastewater reuse. The system addressed the issue of the rapid inorganic membrane fouling caused by the traditional electrocoagulation processes. The formation of a unique cake layer with a bilayer structure in fECUF was favored to decrease the accumulation of organics and inorganics in membrane pores and maintain the membrane flux. Compared with the UF control system, the fECUF system decreased the transmembrane pressure by 63.13%. Redundancy analysis confirmed that oxidation dominated the removal of humic-like substances and UV254, while oxidation and coagulation synergistically promoted the reduction of DOC, protein-like substances, and trace organics. Also, coagulation contributed to the removal of antibiotics resistance genes (ARGs), which reduced their ability to be widely transmuted by a horizontal gene transfer mechanism. Compared to the UF control system, 4.48–39.76 times higher reduction of four ARGs were obtained in fECUF. Overall, this study has verified the potential advantages of the fECUF system in membrane fouling control and contaminants reduction for water reclamation.

The Tbx6 Transcription Factor Dorsocross Mediates Dpp Signaling to Regulate Drosophila Thorax Closure

Movement and fusion of separate cell populations are critical for several developmental processes, such as neural tube closure in vertebrates or embryonic dorsal closure and pupal thorax closure in Drosophila. Fusion failure results in an opening or groove on the body surface. Drosophila pupal thorax closure is an established model to investigate the mechanism of tissue closure. Here, we report the identification of T-box transcription factor genes Dorsocross (Doc) as Decapentaplegic (Dpp) targets in the leading edge cells of the notum in the late third instar larval and early pupal stages. Reduction of Doc in the notum region results in a thorax closure defect, similar to that in dpp loss-of-function flies. Nine genes are identified as potential downstream targets of Doc in regulating thorax closure by molecular and genetic screens. Our results reveal a novel function of Doc in Drosophila development. The candidate target genes provide new clues for unravelling the mechanism of collective cell movement.

An efficient system of aerogel adsorbent combined with membranes for reuse of shale gas wastewater

The internal reuse of shale gas flowback and produced water (SGFPW) can ease the pressure on treatment and management costs and freshwater supply. Internal reuse of SGFPW based on membrane treatments is faced with major challenges of the divalent ion and organic pollutant removal as well as membrane fouling control. To solve these problems, a green and efficient adsorbent of porous biochar aerogel (PBA) was combined with ultrafiltration (UF)-nanofiltration (NF) for SGFPW internal reuse in this study. The removal performance of dissolved organic carbon (DOC, >85.9%) and divalent ions (>70.6%) for three SGFPW showed feasibility of PBA-UF-NF process for internal reuse. Three-dimensional excitation-emission matrix (3D EEM) fluorescence spectrum, organic fractionation and the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory were used to identify the organic composition of SGFPW and analyze membrane fouling. PBA tended to adsorb hydrophobic fraction and alleviated UF membrane fouling caused by attractive hydrophobicity. NF membrane fouling was mitigated due to the increased polar repulsion as well as the decreased synergistic fouling between organics and divalent cations through the reduction of DOC by PBA. PBA-UF-NF process had good performance on organic pollutant and divalent ion removal with decreasing membrane fouling, presenting potential to treat SGFPW onsite for internal reuse.

Photocatalytic ozonation in water treatment: Is there really a synergy between systems?

Numerous studies report on the synergy between ozonation and photocatalytic oxidation (TiO2/UVA), which could open the way to the application of photocatalytic ozonation (PCOz) in water treatment. With the aim of establishing the existence of this synergy and its origin, in this work, using TiO2 P25, 365 nm UVA LEDs and ozone transferred doses up to 5 mg (mg DOC0)−1 (DOC0 7 – 10 mg L−1), a systematic study has been carried out featuring the effect of pH, alkalinity and water matrix in each of the systems involved in PCOz, with special attention to the role of organics adsorption onto TiO2. In ultrapure water, an increase in pH and carbonates content exerted a slight negative effect on the photocatalytic degradation of primidone (low adsorption onto TiO2 and mainly abated by free HO•), this effect being higher on its mineralization. The negative effect of pH and alkalinity was much stronger for oxalic acid (high tendency to adsorb and mainly oxidized by positive holes). Accordingly, the results obtained at pH < pHpzc (point of zero charge of the catalyst) in ultrapure water cannot at all be extrapolated to secondary effluents, since their composition negatively affects the photocatalytic performance. At the experimental conditions applied, only for the secondary effluent a synergy between O3/UVA and TiO2/UVA systems was observed. This synergy would be related, on the one hand, to the generation, from the matrix itself, of reactive entities or intermediates that promote the decomposition of ozone into HO•; and, on the other hand, to an increase in catalyst activity as the matrix UVA absorption decreases, rather than from direct interactions between both systems. Despite de above, ozone requirement to achieve a significant reduction of DOC is high and would only be an interesting strategy for the elimination of ozone-refractory micropollutants.

Preliminarily comparative performance of removing bisphenol-S by ferrate oxidation and ozonation

Bisphenol-S (BS) has recently raised public concerns for its adverse effect on the health safety and ecological security. BS concentrations were detected in many water resources, ranging from 10 ng L−1 to 300 μg L−1, so that various purification techniques have been sought to remove BS. This study investigated the performance of ozonation and ferrate oxidation in the degradation of BS since they are both promising oxidants with high redox potential among water treatment chemicals. It was observed that both ozone and ferrate can achieve over 99% of BS concentration reduction and up to 22.5% of DOC reduction for dosing 0.036 mM of either ferrate or ozone. The vibrio fisheri toxicity exhibited a decline in the treated samples after ozonation or ferrate oxidation. According to the mass spectra analyzed, the degradation pathways were proposed and oxidation products (OPs) were identified. BS degradation by ozonation and ferrate oxidation followed a similar route and four common OPs (OP-249; OP-497-a; OP-497-b, and OP-201) were detected. While ferrate treatment produced one more intermediate (OP-217), ozonation did not, which is attributed to the intensified decomposition of BS by ozonation. The major impact of this study is that ferrate treatment is comparable to the ozonation in removing BS, and further research continuing from this study is necessary to explore the BS removal in various waters with more complex matrixes (e.g., high natural organic matter contents), to investigate BS degradation mechanisms in depth, and to conduct pilot-scale and full-scale trials to establish operational database in running ferrate oxidation and/or ozonation for the treatment of BS in practical world.

Impact of Ozone Used-Alone and Coagulation Aid Treatment on The Reduction of Trihalomethanes Components

The whole research paper examines the impact of ozone as either a just use-alone and coagulation benefit, mainly upon the reduction of dissolved organic carbon from the water with a moderate rate of DOC 10.75 mg/land CaCO3 calcium hardness 300 mg/l. A raw water sample has been taken from the Tigris River (Baghdad, Iraq) was being adopted in research work. The performance of ozone therapy has been assessed by calculations of DOC, DOC quantities, UV254, as well as total trihalomethane (TTHM). Research findings have shown that with 0.9 mg O3/mg DOC ozone use-alone, approximately 60% UV254 reduction and approximately 28% DOC reduction will occur.DOC fractionation analysis indicates that within the water samples, ozone could alter the composition of DOC, transform the hydrophobic fractions toward hydrophilic fractions and reduce TTHM. Ozone was also responsible for a significant reduction in particle stability as well as the dissolved calcium content. Improved water flocculation and improved DOC removal were triggered by these simultaneous ozonation effects. This resulted in a decrease in the coagulant dosage while the dosage of ozone is considerably higher over 0.3 mg O3/mg DOC has added before ferric sulfate coagulation. The pre-ozonation coagulation method also accomplished favorable removal of TTHM with all tested ozone doses (0 to 0.9 mg O3/mg DOC), resulting in lower TTHM during pre-ozonated coagulated waters unlike those through related ozonated waters.

Comparative removal of imidacloprid, bisphenol‐S, and azithromycin with ferrate and FeCl3 and assessment of the resulting toxicity

AbstractBACKGROUNDEmerging micro‐pollutants (EMPs) in water have received much attention due to their potential hazards to human health and ecological security. Ferrate has been researched in recent years to remove both particulate and dissolved impurities (including EMPs) from water, and its promising performance has been attributed to the high oxidation capacity and coagulation functions. However, limited research has compared ferrate with coagulation alone in the treatment of EMPs, which is one of the major objectives of this study.RESULTSThree emerging micro‐pollutants (EMPs), imidacloprid (IMP), bisphenol‐S (BS), and azithromycin (AZM) were chosen for this study. In all cases, ferrate outperformed to ferric chloride in the removal of the EMPs. For a given ferrate dose of 0.05 mM, 99% of BS, 85% of AZM, and 78% of IMP were removed for a start concentration of 10 μg L−1. However, if the start concentration was 1000 μg L−1, removal efficiency was decreased to 82% for BS, 62% for AZM, and 22% for IMP. pH 5 was favorable to the EMP removal by ferrate for the study conditions. Although higher removals of IMP, BS, and AZM were achieved by ferrate in comparison to those by ferric chloride, only 20% DOC removal was achieved by the ferrate. The formation of various oxidation products in the degradation process resulted in the disparity of the solution toxicity; that of BS was reduced but those of IMP and AZM increased after ferrate treatment. Nevertheless, the toxicity of ferric chloride treated samples was all increased.CONCLUSIONFerrate has higher efficiency comparing with FeCl3 to remove IMP, BS, and AZM. Degradation of the EMPs by ferrate was more efficient in acidic conditions (pH 5) and at the EMPs' lower initial concentrations for the given conditions. IMP was more resistant to the ferrate treatment compared to BS and AZM under the same conditions. Overall, 20% DOC reduction was achieved by ferrate for pH 5. Finally, the toxicity of BS can be reduced but those of IMP and AZM were increased after ferrate treatment, whilst the toxicity of ferric chloride treated samples was all increased. © 2020 Society of Chemical Industry

Removal of natural organic matter and ammonia from dam water by enhanced coagulation combined with adsorption on powdered composite nano-adsorbent

Abstract Enhanced coagulation and adsorption were investigated in separate and combined processes to alleviate problems created by high levels of NOM (15 mg L−1) and ammonia (2.5 mg L−1 NH4-N) in dam water. Raw water acidification to pH 6.2 with optimised enhanced coagulation in jar tests achieved effective (68%) DOC reduction and satisfactory residual turbidity, aluminium, and colour, however removed only 5% ammonia. Adsorption on the nano-adsorbent (termed ACZ) led to 45% DOC reduction and excellent 58% ammonia removal in 30 min. Concurrent enhanced coagulation and complementary adsorption using only 80 mg L−1 alum and 150 mg L−1 ACZ doses showed high performance with 76% ammonia, 90% DOC, and 95% trihalomethanes formation potential (THMFP) reduction in 20 min time. Concurrent treatment can be simply implemented utilising readily available rapid mixers and flocculators, and operated on demand. Pre-adsorption and consecutive enhanced coagulation using the same alum and ACZ doses resulted in slightly better DOC but reduced (61%) ammonia removal. The results showed that concurrent treatment could safely resolve a challenging operational problem. ACZ combines the distinct advantages of zeolite and activated carbon in a single product, and may find additional uses in removing taste and odour, heavy metals, and synthetic organic matter from ground and surface waters.

Effect of peroxymonosulfate oxidation activated by powdered activated carbon for mitigating ultrafiltration membrane fouling caused by different natural organic matter fractions

Powdered activated carbon (PAC) adsorption has been widely applied prior to ultrafiltration membrane for potable water production. However, the impact of PAC adsorption on membrane fouling was still controversial. To solve this problem, combined PAC and peroxymonosulfate (PMS) pretreatment was proposed in this study. The application of PAC/PMS for mitigating membrane fouling by natural organic matter (NOM) has been evaluated, and compared with PMS oxidation or PAC adsorption alone. The influence of NOM fractions on the control efficiency was also investigated using humic acid (HA), bovine serum albumin (BSA), sodium alginate (SA), and their mixture (HA-BSA-SA). The performance was examined through normalized flux decline, fouling resistances analysis, scanning electron microscopy, and model fits. The results indicated that PAC and PMS exhibited a remarkable synergistic effect in the reduction of NOM, with the DOC reduction rates of 53.6%, 24.3%, 27.1% and 31.4% for HA, BSA, SA and HA-BSA-SA, respectively. PAC adsorption exhibited limited influence on mitigating membrane fouling, and the co-existence of PAC and HA even exacerbated fouling due to the synergistic fouling effect between them. By contrast, PAC/PMS pretreatment efficiently reduced both reversible and irreversible fouling resistances. The control efficiency was closely associated with the NOM fractions in the feed water, and followed the order of SA > HA-BSA-SA > BSA > HA. The fouling mitigation by PAC/PMS was attributed to both PAC adsorption and oxidation with SO4− and OH. The experimental results are expected to provide a feasible strategy of PAC/PMS for fouling mitigation, and simultaneously solve the problem faced by PAC adsorption.

Pilot-scale comparison of cyclically and continuously operated drinking water biofilters: Evaluation of biomass, biological activity and treated water quality

The objective of this pilot study was to evaluate the impact of cyclical (operated 8–12 h per day) and continuous biofilter operation with respect to biomass development, biological enzyme activity and treated water quality (in terms of organics, nutrients and disinfection by-product (DBP) formation potential). Continuously operated biofilters developed greater densities of biomass, as measured by ATP, when compared to cyclically operated filters; reducing the empty bed contact time (EBCT) increased biomass density under continuous flow conditions. However, once normalized to biomass, it was shown that cyclically operated filters exhibited higher enzyme activity, indicating that this method of operation may improve bacterial function. Reduction of organics was generally similar for both continuous and cyclical filters with the same EBCT, however, cyclical filters demonstrated higher variability during the first 4 h following start-up. Overall, HAA formation potential was better controlled by continuously operated filters, due to poor performance by the cyclical filters upon start-up while THM precursors were removed equally well by all filters. To understand the removal capacity for NDMA precursors through biological filters, both naturally occurring NDMA FP and NDMA FP resulting from spiked anthropogenic precursors was monitored through the filter depth. All the filters removed 90% of the naturally occurring NDMA FP within the first 45 cm; cyclical operation resulted in higher reduction of spiked anthropogenic NDMA precursors (50% higher than continuously operated) demonstrating the advantage of routine shut down on overall microbial activity.Tools to monitor and predict biofilter performance are in high demand. Here we present an “effective activity” term which combines enzyme activity with contact time (EBCT). Effective esterase activity was strongly correlated to DOC reduction as a function of filter operation (cyclical or continuous) and EBCT; effective phosphatase activity was indicative of phosphate removal. The results of this study indicate that routine shut down of the filters as this location improved enzyme activity without compromising control of chlorinated DBPs (THMs and HAAs) or NDMA derived from natural and anthropogenic precursors.

Effect of sulfate radical-based oxidation pretreatments for mitigating ceramic UF membrane fouling caused by algal extracellular organic matter

Algal extracellular organic matter (EOM) released from Microcystis aeruginosa can cause severe membrane fouling during algae-laden water treatment. To solve this problem, three typical sulfate radical-based advanced oxidation processes (SR-AOPs), i.e., ferrous iron/peroxymonosulfate (Fe(II)/PMS), UV/PMS and UV/Fe(II)/PMS, were employed as membrane pretreatment strategies. Their performance on mitigating EOM fouling of a ceramic UF membrane was systematically investigated and compared in the present study. The results indicated that SR-AOPs pretreatments could promote the reduction of DOC and UV254, and the removal performance showed an apparent regularity of UV/Fe(II)/PMS > Fe(II)/PMS > UV/PMS. The pretreatments were very effective for decomposing high-MW biopolymers (>20,000 Da) into low-MW humic substances (1000–20,000 Da), thus reducing the accumulation of high-MW biopolymers on membrane surface. With respect to membrane fouling control, Fe(II)/PMS significantly mitigated both reversible and irreversible membrane fouling, whereas UV/PMS only reduced reversible fouling, and exhibited little effect on irreversible fouling. By contrast, UV/Fe(II)/PMS showed the best performance for fouling reduction due to the synergistic effect of UV and Fe(II) for PMS activation. The dominating fouling mechanism was governed by both pore blockage and cake filtration, likely due to the bimodal MW distribution of EOM, and SR-AOPs pretreatments delayed the transition from pore blockage to cake filtration. In addition, SR-AOPs prior to UF membrane were also very effective to improve the removal of micropollutants (i.e., ATZ, SMT and p-CNB). These results demonstrate the potential application of SR-AOPs as pretreatment for membrane fouling control during algae-laden water treatment.

Long-term performance of biological ion exchange for the removal of natural organic matter and ammonia from surface waters

Anionic exchange is an effective treatment option for the removal of natural organic matter from surface waters. However, the management of the spent brine regenerant often limits the adoption of this process. The current study reports one year of operation of ion exchange resins under biological mode (BIEX, i.e. without regeneration to promote biofilm growth on the media) compared to the performance of (i) ion exchange with weekly regeneration (IEX), (ii) granular activated carbon under biological mode (BAC) and (ii) granular activated carbon under adsorption mode (GAC). Four parallel pilot filters (GAC, BAC, IEX and BIEX) were fed with a colored and turbid river water without pretreatment. Although IEX provided the best performance (80% DOC removal) throughout the study, BIEX achieved a similar performance to IEX prior to DOC breakthrough (92 days) and subsequently achieved a mean DOC removal of 62% in warm water conditions. The GAC filter was rapidly exhausted (2 weeks) while the BAC filter only provided a 5% DOC reduction. Full nitrification was observed on both the BIEX and BAC filters under warm water conditions (>15 °C). After one year of operation, BIEX was successfully regenerated with brine. According to a mass balance, 69% of DOC removal in BIEX was due to ion exchange while we assume the remainder was biodegraded. Operation of ion exchange in biological mode is a promising option to reduce spent brine production while still achieving high DOC removal.

Mineralization of the antineoplastic drug carboplatin by heterogeneous photocatalysis with simultaneous synthesis of platinum-modified TiO2 catalysts

Photocatalytic oxidation of carboplatin, a platinum antineoplastic drug, has been investigated in aqueous heterogeneous solutions containing TiO2 photocatalysts. The current study, besides the photocatalytic degradation of the drug, examines the utilization of the photo-reduction process occurring on the surface of the catalyst, leading simultaneously to the photo-deposition and recovery of platinum. TiO2 photocatalytic process was evaluated for its ability to degrade the molecule of carboplatin and concurrently result in the synthesis of efficient platinum modified TiO2 catalysts. The degradation kinetic was studied under different operational conditions, such as type of photocatalyst, catalyst loading, initial pH and addition of electron acceptors. Three systems were evaluated namely, TiO2 P25 under UV-A and TiO2 Kronos vlp 7000 under UV-A or visible illumination, with respect to their activity for substrate degradation and mineralization and their ability to bind platinum on their surface during photocatalytic oxidation of the drug. The initial degradation rate (r0) decreased in the order TiO2 P25/UV-A > TiO2 Kronos vlp 7000/UV-A > TiO2 Kronos vlp 7000/visible light. For TiO2 P25/UV-A, the addition of 100 mg L−1 H2O2 increases slightly the initial mineralization rate, while degradation rates gradually decrease as photocatalysis takes place in neutral and alkaline pH. Phytotoxicity measurements, showed that heterogeneous photocatalytic oxidation in the presence of TiO2 P25 is capable of reducing the phytotoxicity of carboplatin. For TiO2 P25 and TiO2 Kronos vlp 7000 under UV-A illumination, photo-reduction and deposition of platinum is fully accomplished within 60 min of oxidation, while for TiO2 Kronos vlp 7000 in the presence of visible light, the percentage of platinum deposited on the surface of the catalyst reaches 40%. Platinum photo-deposition is feasible, employing TiO2 P25, even after the catalyst is reused. The synthesized platinum modified TiO2 P25, demonstrated higher photocatalytic efficiency in comparison to the bare one, leading to 100% degradation of the model pollutant malachite green and 40% DOC reduction, after 30 min of photo-oxidation.

A comparative study of ozonation, iron coated zeolite catalyzed ozonation and granular activated carbon catalyzed ozonation of humic acid

This study compares ozonation (O3), iron coated zeolite catalyzed ozonation (ICZ–O3) and granular activated carbon catalyzed ozonation (GAC–O3) for removal of humic acid from an aqueous solution. The results were evaluated by the removal of DOC that specifies organic matter, UV254 absorbance, SUVA (Specific Ultraviolet Absorbance at 254 nm) and absorbance at 436 nm. When ozonation was used alone, DOC removal was 21.4% at an ozone concentration of 10 mg/L, pH 6.50 and oxidation time of 60 min. The results showed that the use of ICZ or GAC as a catalyst increased the decomposition of humic acid compared to ozonation alone. DOC removal efficiencies were 62% and 48.1% at pH 6.5, at a catalyst loading of 0.75 g/L, and oxidation time of 60 min for ICZ and GAC, respectively. The oxidation experiments were also carried out using <100 kDa and <50 kDa molecular size fractions of humic acid in the presence of ICZ or GAC. Catalytic ozonation also yielded better DOC and UV254 reduction in both <50 kDa and <100 kDa fractions of HA compared to ozonation.

Tracking ultrasonically structural changes of natural aquatic organic carbon: Chemical fractionation and spectroscopic approaches.

In this study, the structural alteration to DOC for a range of ultrasound treatments was investigated with chemical fractionation and UV-vis spectroscopic measurement. Ultrasound treatments were applied in continuous and pulsed modes at power levels of 48 and 84 W for effective treatment times of 5 and 15 min. Overall results show that the ultrasound treatments tended to degrade the hydrophobic aromatic fraction, while increasing the hydrophilic fraction to a lesser extent. The highest recorded reduction of hydrophobic DOC (17.8%) was achieved with pulse treatment of 84 W for15 min, while the highest increase in the hydrophilic DOC (10.5%) was obtained with continuous treatment at 84 W and 5 min. The optimal ultrasound treatment conditions were found to be pulse mode at high power and short treatment time, causing a minimal increase in the hydrophilic fraction of 1.3% with moderate removal of the hydrophobic fraction of 15.52%. The same treatment conditions, with longer treatment time, resulted in the highest removal of SUVA254 and SUVA280 of 17.09% and 16.93, respectively. These results indicate the potential for ultrasound treatments in DOC structural alteration. The hydrophobic fraction showed strong and significant correlations with UV absorbance at 254 and 280 nm. A254/A204 also exhibited strong and significant correlations with the hydrophobic/hydrophilic ratio. The other UV ratios (A250/A365 (E2/E3) and A254/A436) had weak and insignificant correlations with the hydrophobic/hydrophilic ratio. This confirms the applicability of UV indices as a suitable surrogate method for estimating the hydrophobic/hydrophilic structure.

A hybrid process of biofiltration of secondary effluent followed by ozonation and short soil aquifer treatment for water reuse

The Shafdan reclamation project facility (Tel Aviv, Israel) practices soil aquifer treatment (SAT) of secondary effluent with hydraulic retention times (HRTs) of a few months to a year for unrestricted agricultural irrigation. During the SAT, the high oxygen demand (>40 mg L−1) of the infiltrated effluent causes anoxic conditions and mobilization of dissolved manganese from the soil. An additional emerging problem is the occurrence of persistent trace organic compounds (TrOCs) in reclaimed water that should be removed prior to reuse. An innovative hybrid process based on biofiltration, ozonation and short SAT with ∼22 d HRT is proposed for treatment of the Shafdan secondary effluent to overcome limitations of the existing system and to reduce the SAT's physical footprint. Besides efficient removal of particulate matter to minimize clogging, coagulation/flocculation and filtration (5–6 m h−1) operated with the addition of hydrogen peroxide as an oxygen source efficiently removed dissolved organic carbon (DOC, to 17–22%), ammonium and nitrite. This resulted in reduced effluent oxygen demand during infiltration and oxidant (ozone) demand during ozonation by 23 mg L−1 and 1.5 mg L−1, respectively. Ozonation (1.0–1.2 mg O3 mg DOC−1) efficiently reduced concentrations of persistent TrOCs and supplied sufficient dissolved oxygen (>30 mg L−1) for fully oxic operation of the short SAT with negligible Mn2+ mobilization (<50 μg L−1). Overall, the examined hybrid process provided DOC reduction of 88% to a value of 1.2 mg L−1, similar to conventional SAT, while improving the removal of TrOCs and efficiently preventing manganese dissolution.

Mature landfill leachate treatment by coagulation/flocculation combined with Fenton and solar photo-Fenton processes

This work reports the treatment of a mature landfill leachate through the application of chemical-based treatment processes in order to achieve the discharge legal limits into natural water courses. Firstly, the effect of coagulation/flocculation with different chemicals was studied, evaluating the role of different initial pH and chemicals concentration. Afterwards, the efficiency of two different advanced oxidation processes for leachate remediation was assessed. Fenton and solar photo-Fenton processes were applied alone and in combination with a coagulation/flocculation pre-treatment. This physicochemical conditioning step, with 2gL−1 of FeCl3·6H2O at pH 5, allowed removing 63% of COD, 80% of turbidity and 74% of total polyphenols. Combining the coagulation/flocculation pre-treatment with Fenton reagent, it was possible to reach 89% of COD removal in 96h. Moreover, coagulation/flocculation combined with solar photo-Fenton revealed higher DOC (75%) reductions than single solar photo-Fenton (54%). In the combined treatment (coagulation/flocculation and solar photo-Fenton), it was reached a DOC reduction of 50% after the chemical oxidation, with 110kJL−1 of accumulated UV energy and a H2O2 consumption of 116mM. Toxicity and biodegradability assays were performed to evaluate possible variations along the oxidation processes. After the combined treatment, the leachate under study presented non-toxicity but biodegradability increased.

낙동강 수계 내 유기물 시료에 따른 생분해 특성

This research was carried out to examine the concentration and fate of dissolved organic matter due to the increased detention time in middle and down stream of the Nakdong River. Aldo the characteristics of biodegradation of DOM were investigated according to the various water sources. The approaches used to characterize DOM biodegradability include the changes in DOC concentration and DOM fraction. Long-term biodegradation test for each organic source was also conducted. As the result, maximum 50% of DOC was reduced during the first 30 days of biodegradation tests. After 30 days, biodegradation of organic matter was continuously progressed, as showing continuous reduction of DOC. While DOC concentration was reduced, SUVA values for the organic matters were increased. Properties of dissolved organic matter by water sources also showed decreasing hydrophilic components while showing increased hydrophobic components. The more rapid reduction of the hydrophilic components than hydrophobic components might be due to the preferential degradation of the hydrophilic components by microorganisms during biodegradation process.