Secondary Wastewater Effluent Research Articles

Solar photon-Fenton process eliminates free plasmid DNA harboring antimicrobial resistance genes from wastewater

This work aimed to assess the elimination and inactivation of resistance-conferring plasmids (RCPs) present in suspension in secondary wastewater by solar photo-Fenton as these are important vectors for the dissemination of antimicrobial resistance. Experiments were performed in synthetic secondary wastewater (SWW) and municipal wastewater treatment plant effluent (MWWTPE). Solar photo-Fenton (50 mg L−1 of H2O2 and 30 mg L−1 of Fe2+) was carried out for 60 min at neutral pH by applying the intermittent iron addition strategy. The removal of RCPs was assessed by Real-Time Polymerase Chain Reaction (qPCR). The transformation of competent non-resistant E. coli was used to evaluate the inactivation of target RCPs harboring antibiotic resistance genes (ARGs) to ampicillin (pSB1A2) or kanamycin (pSB1K3) after treatment and controls. Solar photo-Fenton completely removed RCPs initially present in both matrixes (SWW and MWWTPE), showing enhanced performance compared to the dark Fenton process. Both RCPs were inactivated after 30 min of solar photo-Fenton treatment, while 60 min were necessary to achieve the same effect for the dark Fenton reaction under similar conditions. These results indicate the potential of solar photo-Fenton to improve wastewater quality and reduce the spread of antimicrobial resistance in the environment by hampering the discharge of cell-free RCPs present in suspension in MWWTP onto environmental waters.

Enhanced Treatment of Municipal Wastewater Effluents by Fe-TAML/H2O2: Efficiency of Micropollutant Abatement.

Combining iron with a tetraamido-macrocyclic ligand (Fe-TAML) as a catalyst and with hydrogen peroxide (H2O2) as the bulk oxidant is a process that has been suggested for the oxidative abatement of micropollutants during water treatment. In this study, the reactivity of the Fe-TAML/H2O2 system was evaluated by investigating the degradation of a group of electron-rich organic model compounds with different functional groups in a secondary wastewater effluent. Phenolic compounds and a polyaromatic ether are quickly and substantially abated by Fe-TAML/H2O2 in a wastewater effluent. For tertiary amines, a moderate rate of abatement was observed. Primary and secondary amines, aromatic ethers, aromatic aldehydes, and olefins are oxidized too slowly in the investigated Fe-TAML/H2O2 systems to be significantly abated in a secondary wastewater effluent. Trichlorophenol is readily oxidized to chloromaleic acid and chlorofumaric acid, which support a one-electron transfer reaction as the initial step of the reaction between Fe-TAML/H2O2 and the target compound. Fe-TAML/H2O2 does not oxidize bromide to hypobromous acid; however, iodide is oxidized to hypoiodous acid, and as a consequence, the H2O2 consumption is accelerated by a catalytic reaction in iodide-containing water. Overall, Fe-TAML/H2O2 is a rather selective oxidant, which makes it an interesting system for the abatement of electron-rich phenolic-type pollutants.

Evaluation of the concentration and contribution of superoxide radical for micropollutant abatement during ozonation

Due to the fast reaction of superoxide radical (O2•−) with ozone (O3), it has been suggested that O2•− is present at very low concentrations during ozonation. Therefore, while O2•− has been considered a critical chain carrier for promoting O3 decomposition to hydroxyl radicals (•OH), the direct reactions of O2•− with micropollutants have been assumed to be insignificant during ozonation. In this study, we monitored the exposures of O3, •OH, and O2•− by following the depletion of O3, p-chlorobenzoic acid (pCBA, as •OH probe), and tetrachloromethane (CCl4, as O2•− probe) during ozonation of various water matrices (surface water, groundwater, and secondary wastewater effluent). For a given water matrix, the ratio between •OH and O3 exposures (Rct), O2•− and O3 exposures (RSO), as well as O2•− and •OH exposures (RSH) remained almost constant over the entire reaction time. This suggests that during ozonation, the ratios between the transient concentrations of •OH and O3, O2•− and O3, and O2•− and •OH were also constant and equaled to the Rct, RSO, and RSH, respectively. Based on the O3, •OH, and O2•− exposures observed during ozonation, a chemical kinetic model was proposed to simulate the abatement of ten ozone-resistant micropollutants in the three water matrices by ozonation. The results indicate that due to the higher concentrations of O2•− than •OH (RSH = ~5–8), the reactions with O2•− played a non-negligible or even dominant role in the abatement of some micropollutants that have similar or higher O2•− reactivity than •OH reactivity (e.g., tetrachloroethylene, chloroform, and PFOA). Compared with the previous model that neglected the contribution of O2•− to micropollutant abatement, the proposed model more accurately simulated the abatement efficiencies of the test micropollutants during ozonation. These results indicate that the proposed model can provide a useful tool for the generalized prediction of micropollutant abatement by ozonation.

Performance of a Slurry Photocatalytic Membrane Reactor for the Treatment of Real Secondary Wastewater Effluent Polluted by Anticancer Drugs

The emergence of non-biodegradable and persistent compounds in European surface waters calls for the development of innovative advanced water treatments. Therefore, this work aimed to assess the pe...

Algal extracellular organic matter mediated photocatalytic degradation of estrogens

Estrogens are among the most concerned emerging contaminants in the wastewater treatment effluent due to their sexual disruption in aquatic wildlife. The use of microalgae for secondary wastewater effluent polishing is a promising approach due to the economic benefit and value-added products. In this study, three microalgae species, including Selenastrum capricornutum, Scenedesmus quadricauda and Chlorella vulgaris were selected to conduct batch experiments to examine important mechanisms, especially the role of algal extracellular organic matter (AEOM) on two selected estrogens (17β-estradiol, E2 and 17α-ethynylestradiol, EE2) removal. Results showed that estrogens could not be significantly degraded under visible light irradiation and adsorption of estrogens by microalgae was negligible. All three living microalgae cultures have ability to remove E2 and EE2, and Selenastrum capricornutum showed the highest E2 and EE2 removal efficiency of 91% and 83%, respectively, corresponding to the reduction of predicted estrogenic activity of 86%. AEOM from three microalgae cultures could induce photodegradation of estrogens, and AEOM from Selenastrum capricornutum and Chlorella vulgaris achieved 100% of E2 and EE2 removal under visible light irradiation. Fluorescence excitation–emission matrix spectroscopy identified humic/fulvic-like substances in AEOM from three microalgae cultures, which might be responsible for inducing the indirect photolysis of E2 and EE2. Therefore, in the living microalgae cultures, the major estrogens removal mechanisms should include biotransformation as well as AEOM meditated photocatalytic degradation. Since removal rates through photodegradation could be faster than biotransformation, the AEOM mediated photocatalytic degradation can play a potential role to remove emerging contaminants when using microalgae technology for wastewater effluent treatment.

Emerging organic contaminants and odorous compounds in secondary effluent wastewater: Identification and advanced treatment

This study aims to address organic micropollutants in secondary effluents from municipal wastewater treatment plants (WWTPs) by first identification of micropollutants in different treatment units, and second by evaluating an advanced treatment process for removals of micropollutants. In secondary effluents, 28 types of pharmaceutical and personal care products (PPCPs), 5 types of endocrine disrupting chemicals (EDCs) and 3 types of odorous compounds are detected with total concentrations of 513 ± 57.8 ng/L, 991 ± 36.5 ng/L, 553 ± 48.3 ng/L, respectively. An integrated process consisting of in-situ ozonation, ceramic membrane filtration (CMF) and biological active carbon (BAC) filtration is investigated in a pilot scale (1000 m3/d) for removal of micropollutants in secondary effluents. The total removal efficiencies of PPCPs, EDCs and odorous compounds are 98.5%, 95.4%, and 91.1%, respectively. Removal mechanisms of emerging organic contaminants (EOCs) and odorous compounds are discussed based on their physicochemical properties. The remarkable removal efficiencies of micropollutants by the pilot system is attributed to synergistic effects of combining ozonation, ceramic membrane filtration and BAC filtration. This study provides a cost-effective and robust technology with the capability of treating secondary effluents for reuse applications.

Pre-chlorination effects on fouling during microfiltration of secondary municipal wastewater effluent

Chlorination-induced changes in the physicochemical characteristics of effluent organic matter (EfOM) and their role in fouling of hollow fiber polyvinylidene fluoride (PVDF) microfiltration membranes during wastewater reclamation was mechanistically investigated. Pre-chlorination strongly influenced pressure rise during constant flux forward filtration as well as hydraulically irreversible fouling by backwashing with low doses exacerbating it and high doses alleviating it. Dose-dependent fouling trends originated from alterations in EfOM size and polarity and consequently its interactions with the membrane based on whether applied chlorine concentrations were above or below a threshold value. Variations in macroscopic phenomena such as sorption tendency, streaming potential, and initial fouling upon exposure to pre-chlorinated EfOM were consistent with favorable adhesion energies calculated using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. Progressive fouling even though XDLVO theory predicted unfavorable EfOM-EfOM cohesive energies under all chlorination conditions demonstrated that hydrodynamics (permeation drag) dominated later stages of fouling. EfOM in the raw wastewater was largely deposited on the membrane surface resulting in compressible cake filtration. In contrast, pre-chlorination fragmented EfOM leading to intrapore fouling (standard blocking) at the beginning stages of filtration later transitioning to surface fouling (intermediate blocking).

Total nitrogen removal in biochar amended non-aerated vertical flow constructed wetlands for secondary wastewater effluent with low C/N ratio: Microbial community structure and dissolved organic carbon release conditions

Biochar was utilized to intensify constructed wetland (CW) for further organic and nitrogen removal from secondary wastewater. Four sets of non-aerated biochar amended vertical flow CW (VFCW) were developed to investigate the synergistic effects of biochar and microbes on pollutant removal. Results showed that the average COD and nitrogen removal efficiencies of VFCW1 (with 1% w/w biochar with microbe and plants) achieved 89.1 ± 5.6% and 90.2 ± 3.1% respectively, and their corresponding removal rates of 10.2 ± 0.8 mg-COD/(m3.d) and 3.57 ± 0.3 mg-TN/(m3.d) which were 35 and 52.3% higher than control. The biochar’s dissolved organic carbon release in VFCWs indicated that water and acidic media portray the optimum conditions for nitrogen removal. The 16S RNA gene sequencing analysis indicated that in the biochar-amended VFCWs, bacterial phylum Proteobacteria (24.13–51.95%) followed by Chloroflexi (5.64–25.01%), Planctomycetes (8.48–14.43%), Acidobacteria (2.29–11.65%) were abundantly enhanced. Conclusively, incorporating biochar in non-aerated VFCWs is an efficient technique for enhancing nitrogen removal from secondary effluent.

N-Nitrosodimethylamine Formation during UV/Hydrogen Peroxide and UV/Chlorine Advanced Oxidation Process Treatment Following Reverse Osmosis for Potable Reuse.

Chloramines applied to control microfiltration and reverse osmosis (RO) membrane biofouling in potable reuse trains form the potent carcinogen, N-nitrosodimethylamine (NDMA). In addition to degrading other contaminants, UV-based advanced oxidation processes (AOPs) strive to degrade NDMA by direct photolysis. The UV/chlorine AOP is gaining attention because of its potential to degrade other contaminants at lower UV fluence than the UV/hydrogen peroxide AOP, although previous pilot studies have observed that the UV/chlorine AOP was less effective for NDMA control. Using dimethylamine (DMA) as a model precursor and secondary municipal wastewater effluent, this study evaluated NDMA formation during the AOP treatment via two pathways. First, NDMA formation by UV treatment of monochloramine (NH2Cl) and chlorinated DMA (Cl-DMA) passing through RO membranes was maximized at 350 mJ/cm2 UV fluence, declining at higher fluence, where NDMA photolysis outweighed NDMA formation. Second, this study demonstrated that chlorine addition to the chloramine-containing RO permeate during the UV/chlorine AOP treatment initiated rapid NDMA formation by dark breakpoint reactions associated with reactive intermediates from the hydrolysis of dichloramine. At pH 5.7, this formation was maximized at a chlorine/ammonia molar ratio of 3 (out of 0-10), conditions typical for UV/chlorine AOPs. At 700 mJ/cm2 UV fluence, which is applicable to current practice, NDMA photolysis degraded a portion of the NDMA formed by breakpoint reactions. Lowering UV fluence to ∼350 mJ/cm2 when switching to the UV/chlorine AOP exacerbates effluent NDMA concentrations because of concurrent NDMA formation via the UV/NH2Cl/Cl-DMA and breakpoint chlorination pathways. Fluence >700 mJ/cm2 or chlorine doses greater than the 3:1 chlorine/ammonia molar ratios under consideration for the UV/HOCl AOP treatment are needed to achieve NDMA control.

Accumulation of heavy metals and bacteriological indicators in spinach irrigated with further treated secondary wastewater

Shortage of water for agriculture has resulted in the need to explore the use of wastewater for irrigation, however this can pose a health problem to the people emanating from the produced food as a result of the accumulation of pollutants. The purpose of this research was to investigate the accumulation of some heavy metals and bacteriological indicators in the different parts of spinach vegetable irrigated with secondary wastewater effluent treated through a pilot filtration system. There was a variation of heavy metals accumulation in the roots, stem and leafy parts of the vegetable. Bioaccumulation factors of some metals were greater than 1 in the roots and stems but not in the leaves. Three heavy metals being copper, iron and zinc revealed high translocation factors in the stems than leaves; whereas arsenic, chromium, nickel, manganese and lead had high translocation factors in the leaves than stems. Health index coefficients in the stem during the first, second and third months were 2.33, 0.18 and 3.57 respectively, and corresponding values in the leaves were 0.68, 0.09 and 6.75 if consumed by adults. The health index values greater than 1 in children were 2.68 in the stem during the first month and then 4.1 and 7.76 in the stem and leaves during the third month for spinach consumed by children. There was no bacteriological indicators detected in the aboveground parts of the vegetable. To conclude, irrigation of vegetables should be practiced using secondary treated wastewater and monitoring over time intervals in order to safe guard human health.

Simultaneous photometric determination of oxidation kinetics and average manganese valence in manganese products in situ formed in the reactions of aqueous permanganate with model organic compounds and natural organic matters

In this study, a colorimetric method using 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonate (ABTS) was adopted to investigate oxidation kinetics by permanganate (Mn(VII)) in trace levels (lower than 1 mg/L or 6 µM) and measure average manganese valence in manganese product bulks in (i) synthetic waters containing selected model compounds with electron-rich moieties, (ii) natural organic matters (NOM) isolate solution, and (iii) real water samples including river water, reservoir water and secondary wastewater effluent. The second-order rate constant for Mn(VII) oxidation of phenol determined using ABTS method was demonstrated to be comparable to that measured by traditional high-performance liquid chromatography (HPLC) method at pH 5–9. This method was applied to measure the rate constants of the reactions between Mn(VII) and model compounds with electron-rich moieties. Average manganese valence in manganese product bulks from Mn(VII) oxidation of selected model compounds was lower than 4 at acidic pH, suggesting that Mn(III) was likely to be generated during Mn(VII) oxidation. Possible mechanisms for Mn(III) formation via one/two-electron process were also proposed. Mn(VII) reaction with NOM isolate sample followed two-phase kinetics with rate constants of 3.47 × 10-5 s−1 (mg C/L)-1 and 6.94 × 10-6 s−1 (mg C/L)-1 in the initial and secondary phases at pH 8. Similarly, two-phase kinetics were also found in the consumption of Mn(VII) in real waters. Mn(VII) consumption rates in different real waters followed the order of their dissolved organic carbon levels. In contrast, chlorine decay rates were mainly based on the order of their dissolved organic nitrogen levels. Moreover, average valence in manganese products in real water samples was determined as around 4, which was mainly ascribed to the one-electron-transfer processes of Mn(VII) with NOM constituents in real water samples such as phenols and amines at ambient weak alkaline pH.

Total coliform and Escherichia coli in microplastic biofilms grown in wastewater and inactivation by peracetic acid.

Microplastics (MP) have been proposed as a vector for pathogenic microorganisms in the freshwater environment. The objectives of this study were (a) to compare the fecal indicator growth in biofilms on MP and material control microparticles incubated in different wastewater fractions and (b) to compare MP biofilm, natural microparticle biofilm, and planktonic cell susceptibility to disinfection by peracetic acid (PAA). Biofilms were grown on high-density polyethylene, low-density polyethylene, polypropylene MP, or wood chips (as a material control) and incubated in either wastewater influent or pre-disinfection secondary effluent. Reactors were disinfected with PAA, biofilms were dislodged, and total coliform and Escherichia coli were cultivated. Fecal indicators were quantifiable in both MP and wood biofilms incubated in the wastewater influent but only on the wood biofilms incubated in secondary wastewater effluent. More total coliform grew in the wood biofilms than MP biofilms, and the biofilms grown on MP and woodchips were more resistant to disinfection than planktonic bacteria. Thus, it may be possible to refer to the disinfection literature for fecal indicators in biofilm on other particles to predict behavior on MP. Treatments that remove particles in general would help reduce the potential for fecal indicator bypass of disinfection. PRACTITIONER POINTS: MP biofilm had lower concentrations of fecal indicators than wood biofilm Biofilm on MP was not more resistant to disinfection than wood biofilm Biofilms, regardless of substrate, were more resistant to disinfection than planktonic organisms.

Nanofiltration retentate treatment from urban wastewater secondary effluent by solar electrochemical oxidation processes

Comparison of electrochemical processes at pilot plant scale for the elimination of organic microcontaminants in actual urban wastewater treatment plant secondary effluents pre-treated by nanofiltration ([Cl−] = 1100–2000 mg L−1) membranes (for reducing total volume to be treated and increase water salinity), has been addressed. Anodic oxidation (AO), solar-assisted AO, electro Fenton (EF) and solar photoelectro-Fenton (SPEF) processes have been evaluated by using, when required, ethylenediamine-N,N’-disuccinic acid (EDDS) as complexing agent to maintain iron in solution at natural pH. Target water was spiked with a mix solution of microcontaminants: pentachlorophenol, terbutryn, chlorfenvinphos and diclofenac at initial concentrations of 500 and 100 μg L−1, each. AO and EF processes obtained similar degradation rates as added EDDS competed with microcontaminants for oxidant species. SPEF and solar assisted AO showed that high chloride concentrations was a crucial factor since chlorine species generated by solar-assisted AO were enough for efficient microcontaminant removal avoiding the addition of EDDS. Degradation monitoring of microcontaminants contained in actual urban wastewater treatment plant effluents was carried out by liquid chromatography coupled to hybrid quadrupole-linear ion trap-mass spectrometry.

Performic Acid Disinfection of Municipal Secondary Effluent Wastewater: Inactivation of Murine Norovirus, Fecal Coliforms, and Enterococci.

Performic acid (PFA) is an emerging disinfectant to inactivate bacterial and viral microorganisms in wastewater. In this study, the inactivation kinetics of murine norovirus (MNV) by PFA, in phosphate buffer and municipal secondary effluent wastewater, are reported for the first time. PFA decay followed first-order kinetics and the inactivation of MNV was governed by the exposure of microorganisms to PFA, i.e., the integral of the PFA concentration over time (integral CT or ICT). The extension of the Chick-Watson model, in the ICT domain, described well the reduction of MNV by PFA, with determined ICT-based inactivation rate constants, kd, of 1.024 ± 0.038 L/(mg·min) and 0.482 ± 0.022 L/(mg·min) in phosphate buffer and wastewater, respectively, at pH 7.2. Furthermore, the simultaneous PFA inactivation of MNV and fecal indicators indigenously present in wastewater such as fecal coliforms and enterococci showed that 1-log reduction could be achieved with ICT of 2, 1.5, and 3.5 mg·min/L, respectively. When compared with the most commonly used peracid disinfectant of municipal wastewater, peracetic acid (PAA), the ICT requirements determined using the fitted ICT-based kinetic models were ∼20 times higher for PAA than PFA, indicating a much stronger inactivation power of the PFA molecule.

Predictive models for the degradation of 4 pharmaceutically active compounds in municipal wastewater effluents by the UV/H2O2 process

Pharmaceutically active compounds (PhACs) have been frequently detected in aquatic environment and raised concerns because of their environmental persistence and potential ecological risk, especially carbamazepine (CBZ), erythromycin (ERY), atenolol (ATL) and clofibric acid (CA). The UV/H2O2 advanced oxidation process was considered as an effective process to remove pharmaceuticals in wastewater. Because of the diverse structure of pharmaceuticals and the various wastewater matrices, this study established two models to predict the degradation of 4 PhACs in wastewater by UV/H2O2. Besides, the degradation pathway and toxicity of 4 PhACs by UV/H2O2 were explored. The degradation of 4 PhACs by UV/H2O2 followed the pseudo first-order kinetics pattern. The degradation rate of pharmaceuticals decreased as CBZ > ATL > CA > ERY. A kinetic model combining the steady state concentrations of HO∙ successfully predicted the degradation process of pharmaceuticals in 14 secondary municipal wastewater effluents. Also, a water matrix prediction model by response surface methodology (RSM) was established to estimate the degradation of pharmaceuticals well. A detailed and systematic comparison of two models in the objectives of models, predicting target contaminants, types of wastewater and parameters of models was made. In addition, the tentative transformation pathways of 4 PhACs by UV/H2O2 were proposed. 4 PhACs after UV/H2O2 treatment enhanced the toxicity, and prolongation of treatment time can reduce the toxicity on the luminescence.

Removal of trace organic contaminants from wastewater by superfine powdered activated carbon (SPAC) is neither affected by SPAC dispersal nor coagulation

Powdered activated carbon (PAC) is increasingly used as tertiary treatment for the removal of trace organic contaminants (TrOCs) from wastewater (WW). To enhance the sorption kinetics and capacity, the PAC particles can be milled down to superfine powdered activated carbon (SPAC). However, the small-grained SPAC particles are prone to aggregation, which may impact their treatment performance. In this study we examined the effect of SPAC dispersion and aggregation on TrOC removal kinetics and sorption capacity. Specifically, we assessed how two interventions that modulate the apparent size of SPAC - ultrasonication and coagulation - affect the uptake of TrOCs in secondary WW effluent. We quantified the removal of fourteen TrOCs, of which twelve are indicator substances for micropollutant removal in WWTPs as designated by the Swiss Water Protection Ordinance. We determined that at high SPAC doses (> 1.6 mgSPAC/mg Dissolved Organic Carbon [DOC]), the TrOC removal kinetics were fast even for aggregated SPAC, such that SPAC dispersal by ultrasonication yielded no benefit. At low SPAC doses (< 1.6 mgSPAC/mgDOC) and contact times (< 2 minutes) ultrasonication was beneficial, in particular if the SPAC particles reached complete dispersion prior to exposure to TrOCs. However, the energy consumption of such an ultrasonication step should be carefully weighed against the additional energy requirement associated with using a higher SPAC dose. Finally, a coagulant to mitigate membrane fouling can be added simultaneously with the SPAC without compromising the TrOC removal efficiency. We conclude that under realistic SPAC application scenarios in WWTPs, interventions that disperse SPAC during TrOC sorption are not necessary, and processes that aggregate SPAC are acceptable.

Ozonation in advanced treatment of secondary municipal wastewater effluents for the removal of micropollutants.

The objective of this study was the experimental evaluation of ozonation as an additional treatment step for the removal emerging contaminants from secondary effluents of two wastewater treatment plants (WWTPs), one receiving a primarily domestic wastewater (WWTP-A), and the other one domestic sewage together with pretreated tannery wastewater streams (WWTP-B). The experimental runs were conducted at two different pH values (i.e., original pH and adjusted pH of 10) and at six different ozone doses ranging between 0.2 and 1.5mg O3/mg DOC. A total of 20 compounds, including 12 micropollutants (MPs) and 8 metabolites, were selected as the target analytes for the evaluation of ozonation performance. When the tested MPs and metabolites were considered individually, the maximum elimination level for each compound was reached at different doses; therefore, optimum ozone doses were determined based on the reduction of the total MP content. Ozonation at the original pH with an ozone dose in the range of 0.4-0.6 and 0.8-1.0mg O3/mg DOC was selected as the optimum operating condition for WWTP-A and WWTP-B, respectively, both resulting in an average overall removal efficiency of 55%. Ozone treatment yielded only poor elimination for o-desmethyl naproxen (15%), which was found to be by far the main contributor accounting alone for approximately 30% of the total MP concentration in the secondary effluents. The systematic approach used in this study could well be adopted as a guide to other domestic and municipal WWTPs, which are thought to have a highly variable composition in terms of the MPs and metabolites.

Quantification of the electron donating capacity and UV absorbance of dissolved organic matter during ozonation of secondary wastewater effluent by an assay and an automated analyzer

Ozonation of secondary wastewater treatment plant effluent for the abatement of organic micropollutants requires an accurate process control, which can be based on monitoring ozone-induced changes in dissolved organic matter (DOM). This study presents a novel automated analytical system for monitoring changes in the electron donating capacity (EDC) and UV absorbance of DOM during ozonation. In a first step, a quantitative photometric EDC assay was developed based on electron-transfer reactions from phenolic moieties in DOM to an added chemical oxidant, the radical cation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS·+). The assay is highly sensitive (limit of quantification ∼0.5 mgDOC·L−1) and EDC values of model DOM isolates determined by this assay were in good agreement with values determined previously by mediated electrochemical oxidation (slope = 1.01 ± 0.07, R2 = 0.98). In a second step, the photometric EDC measurement method was transferred onto an automated fluidic system coupled to a photometer (EDC analyzer). The EDC analyzer was then used to monitor changes in EDC and UV absorbance of secondary wastewater effluent treated with ozone. While both parameters exhibited a dose-dependent decrease, a more pronounced decrease in EDC as compared to UV absorbance was observed at specific ozone doses up to 0.4 mgO3·gDOC−1. The concentration of 17α-ethinylestradiol, a phenolic micropollutant with a high ozone reactivity, decreased proportionally to the EDC decrease. In contrast, abatement of less ozone-reactive micropollutants and bromate formation started only after a pronounced initial decrease in EDC. The on-line EDC analyzer presented herein will enable a comprehensive assessment of the combination of EDC and UV absorbance as control parameters for full-scale ozonation.

Preparation and evaluation of zeolites for ammonium removal from municipal wastewater through ion exchange process

The application of ion exchange process for ammonium (NH4+-N) removal from wastewater is limited due to the lack of suppliers of engineered zeolites which present high ammonium exchange capacity (AEC) and mechanical strength. This study focuses on the preparation and evaluation of synthetic zeolites (Zeolite1-6) by measuring AEC and resistance to attrition and compression, against natural (clinoptilolite) and engineered zeolite (reference, Zeolite-N). At high NH4+-N concentrations, Zeolite6 and Zeolite2 showed capacities of 4.7 and 4.5 meq NH4+-N/g media, respectively. In secondary effluent wastewater (initial NH4+-N of 0.7 meq NH4+-N/L), Zeolite1, 2 and 6 showed an AEC of 0.05 meq NH4+-N/g media, similar to Zeolite-N (0.06 meq NH4+-N /g media). Among the synthetic zeolites, Zeolite3 and 6 showed higher resistance to attrition (disintegration rate = 2.7, 4.1 NTU/h, respectively) when compared with Zeolite-N (disintegration rate = 13.2 NTU/h). Zeolite4 and 6 showed higher resistance to compression (11 N and 6 N, respectively). Due its properties, Zeolite6 was further tested in an ion exchange demonstration scale plant treating secondary effluent from a municipal wastewater treatment plant. However, Zeolite6 disintegrated after 2 months of operation, whilst Zeolite-N remained stable for 1.5 year. This highlighted the importance of the zeolite’s mechanical strength for successful application. In particular, future work should focus on the optimization of the zeolite production process (temperature, time and dimension of the kiln during calcination) to obtain an engineered zeolite with a spherical shape thus reducing eventual sharp edges which can affect mechanical strength.

Combination of flow cytometry and molecular analysis to monitor the effect of UVC/H2O2 vs UVC/H2O2/Cu-IDS processes on pathogens and antibiotic resistant genes in secondary wastewater effluents

The efficiency of a new Advanced Oxidation Process (AOP), namely the photo Fenton like process UV-C/H2O2/IDS-Cu, in removing determinants of antibiotic resistance and pathogenic bacteria was compared to a consolidated AOP (namely UV-C/H2O2) in a secondary treated municipal WasteWater (WW). A reductionist experimental laboratory-based approach was applied on real WW and the parameters were collected by an alternative integrated approach using (i) flow cytometry to enumerate bacteria and test for the fitness of the bacterial communities and (ii) molecular analyses to define the community composition (16S rRNA amplicon sequencing) and the abundances of Antibiotic Resistance Genes (ARGs) and of the class 1 integron (intI1 gene) (by quantitative PCR). The same approach was applied also to post-treatment regrowth tests (24 h) to define the potential persistence of the tested parameters. These experiments were performed in both, human pathogens favorable conditions (HPC, in rich medium and 37°C) and in environmental mimicking conditions (EMC, original WW and 20°C). UV-C/H2O2/IDS-Cu process resulted to be more effective than the UV-C/H2O2in inactivating bacterial cells in the EMC post-treatment regrowth experiments. Both AOPs were efficiently abating potential human pathogenic bacteria and ARGs in the HPC regrowth experiments, although this trend could not be detected in the measurements taken immediately after the disinfection. In comparison with the UV-C/H2O2, the UV-C/H2O2/IDS-Cu process did not apparently offer significant improvements in the abatement of the tested parameters in the WW effluent but, by evaluating the results of the regrowth experiments it was possible to extrapolate more complex trends, suggesting contrasting efficiencies visible only after a few hours. This study offers a detailed view on the abatement efficiency of microbiological/genetic parameters for the UV-C/H2O2/IDS-Cu process, calling for technical adjustments for this very promising technology. At the same time, our results clearly demonstrated the inadequacy of currently applied methodologies in the evaluation of specific parameters (e.g. determinants of antibiotic resistance and pathogenic bacteria) in WW.