Secondary Wastewater Effluent Research Articles

IoT-Based Tryptophan-like Fluorescence Portable Device to Monitor the Indicators for Microbial Quality by E. coli and Biochemical Oxygen Demand (BOD5)

Tryptophan-like fluorescence (TLF) is a key indicator of water contamination, particularly of microbial origin and biodegradable organic compounds. This study introduces an Internet of Things (IoT)-enabled portable device (IoT-TLF-PD) for real-time monitoring of microbial quality and biochemical oxygen demand (BOD5). The device was tested using surface water (S1), secondary wastewater (S2), and final wastewater effluents (S3). Results showed significant correlations between TLF intensity, Escherichia coli (E. coli) counts, and BOD5, with R2 values of 0.77 (S1), 0.61 (S2), and 0.76 (S3) for BOD5, and 0.60 (S2) to 0.68 (S3) for E. coli. Considering various water samples, a strong correlation was found between E. coli and BOD5 with TLF intensity normalized by total organic carbon (TOC) concentration (TLF intensity/TOC). The R2 value for E. coli was 0.92, and for BOD5, it was 0.77. This indicates the necessity of accounting for organic matter concentration when interpreting TLF intensity in water quality assessments. The study confirmed the potential of the IoT-TLF-PD to serve as a cost-effective, real-time indicator for assessing water quality, especially for detecting microbial contamination. This technology offers a valuable tool for environmental monitoring and water management.

Mathematical modeling of ozone decomposition processes in wastewater treatment: A lumped kinetic approach with initial ozone demand

Ozone-based processes involve complex reaction networks and exhibit matrix-dependent decomposition patterns when dosed to wastewater effluents. Existing models for ozone decomposition are either too complex or not sufficiently descriptive of the regime manifested during initial ozone demand and decay. Models incorporating detailed reactions have shown limited applicability due to the high number of initial states and state variables involved. This study introduces a new mathematical model that balances accuracy and complexity in describing the main phases of ozone decomposition in secondary wastewater effluents. Specifically, a simplified model is proposed based on lumped variables, including initial ozone demand, two classes of organic matter (slow and fast reacting), radical forming (and ozone-decomposing) compounds, radical scavengers, and a hypothetical target contaminant. Results revealed that the model can predict with reasonable accuracy both the rapid initial ozone demand (occurring at very short timescales <10 s) and the slower ozone decomposition processes (occurring at longer timescales >30 s). A global sensitivity analysis was also conducted to further model refinement and simplification, which led to the elimination of three reactions connected to the generation and consumption of radicals (threshold |RXY| ≥ 0.05). Satisfactorily low residual values (RMSE≤7·10−6 M) were observed in all cases. Finally, the adequacy of the model was further tested against an independent set of ozone decomposition experiments obtained from the literature, confirming its suitability in describing ozone decomposition in secondary wastewater effluents with initial ozone demand.

Molecular insights into the degradation of organic matter from secondary swine wastewater effluent: A comparative study of advanced oxidation processes

Advanced oxidation processes (AOPs) are promising for the treatment of secondary swine wastewater effluents, however, the molecular-level understanding of effluent organic matter (EfOM) removal and transformation during AOPs is limited. This study employed molecular-level characterization based on Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and bulk characterizations to investigate these processes in various AOPs, including Cu-Fenton, UV-Cu-Fenton, Fenton, UV-Fenton, and UV/H2O2 treatments. Our findings revealed that the removal rates of dissolved organic carbon and EfOM molecules follow the sequence of UV-Fenton > Fenton > UV-Cu-Fenton > UV/H2O2 > Cu-Fenton, correlating with the rates of H2O2 decomposition during reactions. AOPs with faster H2O2 decomposition, indicative of higher reactive oxygen species generation, predominantly mineralize rather than transform EfOM. Linkage analysis highlighted oxygen addition and deamination as the primary transformation reactions, with variations in the dominance levels of these reactions across different AOPs. Recalcitrant molecule, particularly CHNO and CHO types, including low-molecular-weight carboxyl-rich alicyclic molecules, pose challenges in treatment. To enhance the efficacy of secondary effluent treatment, strategies focusing on the targeted removal of such recalcitrant EfOM should be developed. This study provided new insights into the selection and optimization of AOPs for secondary swine wastewater effluent treatment.

Iron–molybdenum bimetals incorporated montmorillonite-based catalytic ceramic membrane for heterogenous Fenton reaction towards the degradation of micropollutants in water

This study developed an innovative material approach that integrated Fenton catalysis with membrane filtration in a single system using iron–molybdenum bimetal oxides (FeMoO) incorporated montmorillonite (MMT)-based ceramic membrane (FeMoMMTCM) to achieve continuous Fenton reaction for water purification. The embedded bimetallic FeMoO catalyst created abundant active Fe(II) sites on the external and internal surfaces of the ceramic membrane (CM) for H2O2 activation. Using naproxen (NPX) as a model micropollutant in water, the FeMoMMTCM/H2O2 system achieved a 98.6 % removal of NPX (10 mg/L) within a filtration period of 3.4 min through the membrane, in comparison to a 17.5 % removal by FeMoMMTCM filtration with no H2O2 dosing and a 21.1 % removal by the FeMoO-less MMTCM/H2O2 system. The catalytic membrane demonstrated its high NPX removal efficiency over multiple cycles, retaining its effectiveness even in the presence of co-existing ions and organic matter in the water matrix. Furthermore, the FeMoMMTCM/H2O2 system was able to remove nearly 70 % of residual organic pollutants from the actual secondary wastewater effluent. The quenching tests and electro-paramagnetic resonance (EPR) detection confirmed the generation of hydroxyl (OH) and superoxide (O2−) radicals from H2O2. The excellent catalytic performance can be attributed to the Fe-Mo bimetallic catalyst, in which the active Mo(VI)/Mo(IV) cycle can facilitate the Fe(II)/Fe(III) cycle for continuous Fenton reaction. The cost analysis indicates that the low-cost MMT and its low sintering temperature for ceramics would greatly decrease the cost of MMTCM (243.1 US$/m2 vs. 541.5 US$/m2 of alumina-based CM). Overall, the research presents a technical strategy for the fabrication of highly cost-effective catalytic membranes with Fenton reaction for removing micropollutants from water.

Degradation of extracellular antibiotic resistance genes using peracetic acid (PAA) and performic acid (PFA)

Antibiotic resistant bacteria (ARB) associated infections are identified as a major threat to human health in the 21st century. Wastewater contains antibiotic resistance determinants and they are discharged to aquatic environments with treated or untreated effluents. These antibiotic resistance determinants can be taken up by environmental bacteria via horizontal gene transfer (HGT) and they can become antibiotic resistant. Among antibiotic resistance determinants, extracellular DNA containing antibiotic resistance genes can be up taken by environmental bacteria via natural transformation. Therefore, we evaluated the suitability of low-cost disinfectants peracetic acid (PAA) and performic acid (PFA) on inactivating total and functional extracellular ARGs in ultrapure water and secondary wastewater effluent matrices using pUC19 as a model ARG. Performance of PAA and PFA in inactivating extracellular ARGs was compared with the performance of free chlorine disinfection. RT-qPCR results showed that inactivation of ampR gene in pUC19 plasmid suspended in ultrapure water and wastewater secondary effluent by free chlorine was higher compared to PAA and PFA. However, the reduction of functional pUC19 by PAA and PFA were comparable to free chlorine. Transformation frequency of pUC19 treated by PAA and PFA achieved the maximum possible reduction within a shorter time compared to free chlorine treatment, highlighting the possibility of having disinfection chambers with smaller footprints in wastewater treatment plants. These results suggest the suitability of PAA and PFA for inactivation of ARGs in aquatic samples as alternative disinfectants to free chlorine.

Ozonation of the antiviral oseltamivir in wastewater effluent: Matrix effect, oxidation pathway, and toxicity assessment

The potential environmental impacts of commonly employed antiviral drugs and their byproducts have attracted attention but remain largely unexplored. In this study, ozone (O3) was used to remove the oseltamivir phosphate (OP), a widely used antiviral, from different water matrices, including secondary municipal wastewater effluent (WWE). Over 90 % of OP was removed from a buffer solution using 10 µM of O3 in a short reaction time (30 s), while pseudo-first-order kinetics constants (K) showed a strong linear relationship with the initial O3 dosage. The pH of the solution was found to be an important factor in the ozonation process since the degradation mechanisms and, thereby, the K values are affected by the structural conformations of OP (protonated or deprotonated forms), the generation of hydroxyl radicals (•OH) under mild basic conditions, and the depletion of O3 under extreme basic pH. In addition, common inorganic ions slightly affect the K values, but increasing the ionic strength negatively influences the degradation process. Organic components in WWE also reduced the efficiency; however, over 95 % of OP degradation was achieved using a ratio of O3 dosage to dissolved organic carbon (DOC) of 0.544 g O3 g–1 DOC. Finally, a degradation pathway was proposed based on the detection of byproducts formed by direct ozonation and hydroxylation reactions. Acute toxicity and genotoxicity assessments on ozonated matrices, especially the WWE sample, suggest that these byproducts have no potential toxic effects. All these findings strongly suggest that ozonation can effectively degrade antivirals in municipal effluents.

Coupling UVC254 nm-LED/H2O2 and Fenton processes for disinfection and contaminants of emerging concern removal in continuous mode for wastewater reclamation in accordance with EU 2020/741

A novel strategy based on the sequential combination of UVC254 nm-LED/H2O2 and the Fenton process at neutral pH in continuous flow mode for wastewater reclamation has been assessed. The concentration of Escherichia coli (E. coli) reached water class A according to the European Union (EU) Regulation 2020/741 (≤10 CFU/100 mL) and a 87 ± 2 % of the contaminants of emerging concern (CECs) load was removed, complying with the new proposal regarding Urban Wastewater Treatment (Directive COM (2022) 541). To reach these results, initially the municipal wastewater secondary effluent was kept under UVC254 nm-LED/H2O2 process with a hydraulic residence time (HRT) of 5 min, a liquid depth of 5-cm and 1.8 mmol L−1 of H2O2. In the sequence, addition of Fe2+ to the outside of the UVC254 nm-LED reactor was added to acquire the desired concentration of 1.8 mmol L−1 Fe2+ (Fenton process). To obtain the same disinfection and CECs degradation by only UVC254 nm-LED/H2O2 process, 45 min-HRT were necessary. These results show that the coupled processes are the best strategy, given the reduction in HRT (from 45 to 5 min) and total cost (from 1.79 to 0.54 € m−3). In addition, new research on the application at pilot scale will encourage to evaluate the long-term toxicity of the reclaimed wastewater and to identify the main transformation products of the most abundant CECs.

Long term operation of a continuous submerged photocatalytic membrane reactor utilizing membrane distillation: Membrane performance and treatment efficiency

Long term (200 h) continuous operation of a submerged photocatalytic membrane reactor utilizing direct contact membrane distillation (SPMR-DCMD) is presented. Various types of feed contaminated with ketoprofen were treated: brackish water (BW), seawater (SeaW), and secondary wastewater effluent (SE). Ketoprofen decomposition after 24 h exceeded 99.5 %, regardless of feed type. The distillate showed no toxicity to Aliivibrio fischeri. A significant decrease in flux after 100–124 h of BW and SeaW treatment occurred due to scaling, while for SE the flux remained almost constant for 200 h. This indicates that a shorter study would not allow a proper analysis of the process. A scaling layer was formed regardless of feed type, and the formation of CaSO4⋅2H2O, CaCO3 or (Ca,Mg)CO3 was proved. The porous structure of the deposit during SE treatment prevented significant flux deterioration. The formed TiO2 layer protected the membrane from damage by the growing salt crystals.

Photocatalytic Degradation of Losartan with BiOCl/Sepiolite Nanocomposites

Developing highly active and available, environmentally friendly, and low-cost photocatalytic materials is one of the most popular topics in photocatalytic degradation systems. In the present study, a series of BiOCl/Sepiolite composite photocatalysts were prepared (in the range of 5%BiOCl/Sepiolite–30%BiOCl/Sepiolite). Their characterization was conducted using X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy, nitrogen physical physisorption at the temperature of liquid nitrogen (77 K), and attenuated total reflectance-Fourier transform infrared spectroscopy. Results showed that composite photocatalysts possess superior efficiency than the parent materials for losartan, an antihypertensive agent, degradation in water, with the sample with only 10%wt. BiOCl shows the highest performance. The beneficial effect of the addition of sepiolite to BiOCl is derived from the increase in surface area, the prevention of particle aggregation, and the efficient separation of photogenerated species. Increasing catalyst concentration from 125 mg/L up to 500 mg/L was accompanied by an increase in the apparent kinetic constant from 0.077 min−1 to 0.197 min−1 while varying losartan concentration from 0.25 to 5.00 mg/L slowed down the removal efficiency. In addition, losartan degradation was only partially hampered in the case of bottled water, whereas it was practically stopped in a secondary wastewater effluent. Overall, this study serves as a useful guide for using geopolymers in photocatalytic applications.

A high-flux atomically dispersed MIL-100 (Fe) incorporated PMS-based LDH catalytic membrane for the removal of micropollutants from secondary effluent wastewater

This study fabricated a CoFe layered double hydroxide (CoFeLDH) membrane incorporating the metal–organic framework (MOF) MIL(100)Fe, tailored for a peroxymonosulfate (PMS) based system. Among various combinations of MOF and LDH nanosheets on a PVDF substrate, the highest water flux, reaching 1900 L/m2/hr/bar, was achieved with an LDH/MOF ratio of 5:1 and an MOF concentration of 0.025 M. The optimized membrane exhibited exceptional performance, achieving 99 % degradation of ranitidine at 0.1 mM PMS. The LDH MOF catalytic membrane exhibited excellent treatment performance in real water matrices and demonstrated long-term operational efficiency. The effective removal of ranitidine by this catalytic membrane was attributed to a synergistic combination of radical (SO4− and OH) and non-radical (singlet 1O2 and electron transfer O2) oxidation pathways, with SO4− and singlet 1O2 playing a predominant role. Post-activation, 40 % of surface Co2+ and 65 % of Fe2+ in the LDH MOF membrane were found in the + III oxidation state, highlighting the significance of metal catalytic sites and the reusability potential of the membrane. The durability of the membrane was evident through 10 cycles, achieving a flux recovery ratio of 95 % in the first cycle and sustaining efficient performance across pH variations (3 to 9) and exposure to various anions. Importantly, negligible metal leaching was observed for the real water samples, ensuring suitability for large-scale applications.

Ferrate as a coagulant prior to sand filters treating secondary wastewater effluent for reuse.

Wastewater reuse is one of the crucial water resources in Egypt due to the ongoing need to increase water resources and close the supply-demand gap. In this study, a new coagulant has been investigated before sand filters as an advanced wastewater treatment method. The sand filter pilot was run at a hydraulic loading rate of 0.75 m/h and two different dosages of three coagulants (Alum, FeCl3, and Ferrate VI) were selected using the jar tests. The sand filter without coagulant removed 12% of BOD5 and 70% of turbidity. Applying in-line coagulation before the sand filter provided effluents with better quality, especially for turbidity, organics, and microorganisms. Ferrate provided the highest removal of turbidity (90%) and BOD5 (93%) at very low dosages and lower costs compared with other coagulants, however, it adversely impacted both conductivity and dissolved solids. A significant effect on reducing bacteria was obtained with 40.0 mg/L of alum. According to the study's findings, the ferrate coagulant enhanced the sand filter's performance producing effluents with high quality, enabling it to meet strict water reuse regulations as well as aquatic environmental and health preservations.

Achieving realistic ozonation conditions with synthetic water matrices comprising low-molecular-weight scavenger compounds

Ozonation is used worldwide for drinking water disinfection and increasingly also for micropollutant abatement from wastewater. Identification of transformation products formed during the ozonation of micropollutants is challenging due to several factors including (i) the reactions of both oxidants, ozone and hydroxyl radicals with the micropollutants, as well as with intermediate transformation products, (ii) effects of the water matrix on the ozone and hydroxyl radical chemistry and (iii) the generation of oxidation by-products. In this study, a simple approach to achieve realistic ozonation conditions in the absence of dissolved organic matter has been developed. It is based on composing synthetic water matrices with low-molecular-weight scavenger compounds (phenol, methanol, acetate, and carbonate) that mimic the chemical interactions of ozone and hydroxyl radicals with real water matrices. Synthetic waters composed of only four low-molecular-weight compounds successfully replicated two lake waters and two secondary wastewater effluents, matching instantaneous ozone demand, ozone and hydroxyl radical exposures in the initial phase, as well as the ozone evolution in the second phase of the ozonation process. The synthetic water matrices also reproduced the effects of temperature and pH changes observed in real waters. The abatement of two micropollutants, bezafibrate and atrazine, and the formation of the corresponding transformation products during ozonation were in agreement for synthetic and real waters. Furthermore, the kinetics and extent of bromate formation during ozonation in synthetic water were comparable to real lake water and wastewater. This supports the robustness of the proposed approach because bromate formation is very sensitive to the interplay of ozone and hydroxyl radicals. Furthermore, with the novel reaction system, a significant effect of hydroxyl radicals scavenging by carbonate on bromate formation was demonstrated. Overall, the herein-developed approach based on synthetic water matrices allows to perform realistic ozonation studies including both oxidants, ozone and hydroxyl radicals, without the constraints of using dissolved organic matter.

Study of the Bunsen–Roscoe Reciprocity Law in Solar Water Disinfection (Optical Effect) for E. coli, E. faecalis and C. perfringens

Water stress and water quality represent major environmental challenges in the 21st century. In response, wastewater management and its potential reuse emerge as strategies to mitigate these problems. This research aims to verify the law of reciprocity in the solar disinfection process of real secondary wastewater effluents for different faecal microorganisms. Flat disinfection reactors, subjected only to natural and continuous UV radiation, were used. The study focused on the optical effect of UV radiation, eliminating the significant influence of the thermal effect and its synergy in solar disinfection at temperatures above 45 °C, by controlling the temperatures of the water samples to levels below 20 °C. Three experimental tests were carried out on sunny days. Each test comprised two trials, under the following conditions: (a) low solar irradiance over a prolonged time (duration approximately: 2.6 h) and (b) high solar irradiance and a shorter period of time (approximately 2 h), with each receiving the same UV dose. Inactivation kinetics was analysed for E. coli, E. faecalis, and C. perfringens (including spores). The results validated the reciprocity law for E. coli in all tests for UV doses &gt; 20 Wh/m2, showing no significant deviations, with inactivation rates of 0.44 to 0.51 m2/Wh for initial concentrations of 106–107 CFU/100 mL. In contrast, for E. faecalis, the reciprocity was only valid at intensities &lt; 700 W/m2, with rates of 0.04 and 0.035 m2/Wh for 105–106 CFU/100 mL; above this irradiance value, the law varied significantly and was not valid. C. perfringens did not show significant disinfection results during the experiments to verify this law, mainly due to the resistance of its spores. Additional experimentation with C. perfringens is necessary, by extending the length of the experiments and/or conducting them at higher irradiance values, in order to reach bacterial inactivation to enable the analysis of the reciprocity law. In general, the main conclusion from these results is that the reciprocity law in solar disinfection would be difficult to use for the estimation of water solar disinfection based on the irradiance and exposure times, as there are deviations from it at least in one specie (E. faecalis). Mores studies should be carried out to fully understand and determine the validity of this law and its potential application for forecasting solar water disinfection.

Green electrospun Janus membrane of polyether block amide (PEBA) doped with hierarchical magnesium hydrogen phosphate for the removal of pharmaceuticals and personal care products

It has been a challenge to prepared polyether block amide (PEBA) fibrous membrane via solution electrospinning. The only few reported methods though involved hazardous solvents and surfactants which were against the principle of green chemistry. In this work, uniform fibrous membrane of PEBA was successfully fabricated by solution electrospinning with a bio-based solvent dihydrolevoglucosenone (Cyrene). To further improve the mechanical strength and adsorption performance of the PEBA membrane, a hierarchical magnesium hydrogen phosphate (MgHPO4·1.2H2O, MHP) was synthesized to blend evenly into the PEBA matrix. A Janus MHP/PEBA membrane with one side of hydrophobic surface and the other side of hydrophilic surface was subsequently prepared, which exhibited fast adsorption, high capacity, good selectivity and reusability towards ibuprofen, acetaminophen, carbamazepine and triclosan. In addition, the Janus membrane showed high removal efficiency of the above contaminants in secondary wastewater effluent with good long term stability. It demonstrated that this Janus MHP/PEBA membrane had a good potential in practical wastewater treatment.

Reusable and inductively regenerable magnetic activated carbon for removal of organic micropollutants from secondary wastewater effluents

This work introduces a new sustainable alternative of powdered activated carbon (PAC) - magnetically harvestable and reusable after regeneration via inductive heating - for the adsorptive removal of organic micropollutants (OMP) from secondary wastewater effluents. For this purpose, two commercial PACs - lignite “L” (1187 m2/g) and coconut “C”-based (1524 m2/g) - were modified with magnetic iron oxide following two different synthesis approaches: infiltration (“infiltr”) and surface deposition (“depos”) route. The resulting magnetic powdered activated carbons (mPAC) and their precursor PACs were fully characterized before application. The iron oxide content of the modified “L” and “C” samples was ∼30 % and ∼20 %, respectively. Iron oxide gives the PAC beneficial magnetic properties for easy magnetic separation and simultaneously acts as an inductively heatable agent for the carbon regeneration. The infiltrated samples displayed better inductive heating performance and regeneration than their deposited counterparts. Tests with real wastewater showed fast adsorption kinetics of the organic load following the pseudo-second-order kinetic model. Adsorption isotherms were compliant with the Freundlich isotherm model. Sample “L-infiltr” had the best overall adsorption performance throughout 5 reuse cycles when intermediately inductively regenerated (<3 % drop in organics removal per cycle with intermediate regeneration vs. ∼10 % drop per cycle without regeneration). The treated supernatant was additionally tested for 31 representative organic micropollutants and their transformation products (pharmaceuticals, personal care products, industrial chemicals, etc.), where 26 OMPs had consistently high removal (>85 %) throughout 5 cycles with intermediate regeneration and for 28 OMPs the total adsorption efficiency dropped by <5 % after 5 cycles.

Rejection of malathion by nanofiltration and reverse osmosis membranes exposed to foulant and two clean-in-place procedures

ABSTRACT This research tested the treatment efficacy of an Energy Savings Nanofiltration 1 Low Fouling (ESNA 1-LF) nanofiltration (NF) and an Energy Saving Polyamide 2 (ESPA2) reverse osmosis (RO) membrane for removing malathion from water. Both membranes are of composite polyamide construction. The study included measuring malathion rejection using both pristine membranes and membranes exposed to a simulated secondary wastewater effluent foulant before and after two types of clean-in-place procedures. Across all conditions studied, malathion rejection ranged from 84 to 95% for the ESNA1-LF NF membrane and 77 to 94% for the ESPA2 RO membrane. Contact angle measurements were also collected for each membrane exposure condition. While the contact angle measurements indicated changes to the hydrophobicity of the selective layer of the membranes, they did not correlate to changes in the performance of malathion rejection. As expected, it was observed that malathion rejection improved with the introduction of foulant. Also, the clean-in-place procedures helped restore flux while maintaining malathion rejection.

Influence of ozonation and UV/H2O2 on the genotoxicity of secondary wastewater effluents

The implementation of novel wastewater treatment technologies, including Advanced Oxidation Processes (AOPs) such as ozonation and ultraviolet radiation (UV) combined with hydrogen peroxide (H2O2), can be a promising strategy for enhancing the quality of these effluents. However, during effluent oxidation AOPs may produce toxic compounds that can compromise the water reuse and the receiving water body. Given this possibility, the aim of this study was to evaluate the genotoxic potential of secondary effluents from two different Wastewater Treatment Plants (WWTP) that were subjected to ozonation or UV/H2O2 for periods of 20 (T1) and 40 (T2) minutes. The genotoxic potential was carried out with the Comet assay (for clastogenic damage) and the Micronucleus assay (for clastogenic and aneugenic damage) in HepG2/C3A cell culture (metabolizing cell line). The results of the comet assay revealed a significant increase in tail intensity in the Municipal WWTP (dry period) effluents treated with UV/H2O2 (T1 and T2). MN occurrence was noted across all treatments in both Pilot and Municipal WWTP (dry period) effluents, whereas nuclear buds (NBs) were noted for all Pilot WWTP treatments and UV/H2O2 treatments of Municipal WWTP (dry period). Moreover, the UV/H2O2 (T1) treatment of Municipal WWTP (dry period) exhibited a noteworthy incidence of multiple alterations per cell (MN + NBs). These findings imply that UV/H2O2 treatment demonstrates higher genotoxic potential compared to ozonation. Furthermore, seasonal variations can have an impact on the genotoxicity of the samples. Results of the study emphasize the importance of conducting genotoxicological tests using human cell cultures, such as HepG2/C3A, to assess the final effluent quality from WWTP before its discharge or reuse. This precaution is essential to safeguard the integrity of the receiving water body and, by extension, the biotic components it contains.

The Role of Ozonation as an Advanced Oxidation Process for Attenuation of 1,4-Dioxane in Potable Reuse Applications

ABSTRACT The combination of ozone and hydrogen peroxide (O3/H2O2), or the peroxone process, has often been used as an advanced oxidation process (AOP) in groundwater remediation and drinking water applications. This historical precedent sometimes leads to the misconception that H2O2 addition is required to achieve AOP conditions during ozonation. This is not the case for secondary or tertiary wastewater effluent applications, in which ozone reacts with abundant dissolved organic carbon (DOC) to generate hydroxyl radicals (∙OH). This study demonstrates the use of ozone with and without H2O2 addition to yield ∙OH exposures (up to 10−9 M-s) capable of achieving > 0.5-log10 attenuation of the industrial contaminant and probable human carcinogen 1,4-dioxane. This low molecular weight compound is commonly used as a surrogate when establishing AOP design criteria for potable reuse applications. DOC-normalized ozone doses (i.e., O3/DOC ratios) of ~ 1.0 and ~ 1.3 achieved 0.5-log10 attenuation of 1,4-dioxane with O3/H2O2 and O3, respectively. Also, a predictive model based on ∙OH exposure was accurate within approximately ± 10%. These results suggest that ozonation’s role as an AOP, even in the absence of H2O2, should be acknowledged in regulatory frameworks to reduce unnecessary treatment redundancy and facilitate broader implementation of potable reuse.

Removal of most frequent microplastic types and sizes in secondary effluent using Al2(SO4)3: choosing variables by a fuzzy Delphi method

Microplastics (MPs) as an emerging pollutant can affect aquatic organisms through physical ingestion, chemical problems and possible creation of biological layers on their surfaces in the environment. One of the significant ways for MPs to enter the aquatic environment is through the effluent discharge of wastewater treatment plants (WWTPs). In this study, first, the concentration and characteristics of MPs in secondary wastewater effluent, and the influential variables related to the coagulation process, for MPs removal were identified using systematic reviews of previous studies. Then, the most proper MPs characterization and coagulation variables were chosen by experts’ opinions using a fuzzy Delphi method. Therefore, the experiment tested in conditions close to the full-scale wastewater treatments. Finally, in the laboratory removal of MPs by coagulation of polyamide (PA), polystyrene (PS), and polyethylene (PE), < 125 and 300–600 μm in size, was tested by a jar test applying Al2(SO4)3 in doses of 5 to 100 mg/L plus 15 mg/L polyacrylamide as a coagulant aid. Using R and Excel software, the results were analyzed statistically. It was concluded that the maximum and minimum removal efficiency was 74.7 and 1.39% for small PA and large PE, respectively. Smaller MPs were found to have higher removal efficiency. The MPs type PA achieved greater removal efficiency than PS, while PE had the least removal efficiency.

Optimizing SRT for improved biomass production and nutrient removal from wastewater secondary effluent in a continuous mode MPBR system with Monoraphidium sp.: An experimental and growth kinetics model approach

This study aimed to evaluate the impacts of solids retention time (SRT) and influent nutrient concentration on the specific growth rate and nutrient removal efficacy of Monoraphidium sp. in a continuous mode membrane photobioreactor (MPBR). At SRT of 1 d, maximum biomass productivity of 421 mg·L−1·d−1 and nutrient removal rates of 59.9 % and 79.8 % for total nitrogen (TN) and total phosphorus (TP) were achieved. After reducing the influent nutrient concentration, Monoraphidium sp. maintained high biomass productivity of 385 mg·L−1·d−1 and nutrient removal rates of >95 % for TN and TP. The most important factor in Monoraphidium sp. growth assessment was intracellular nitrogen concentration (QN) rather than extracellular nutrient concentration. Flynn modified Droop model showed a better fit when the dimensionless parameter (Kq) was 0.235 for the relationship between the specific growth rate (μ) and QN. The model also revealed that even at low nitrogen concentrations (0.1 mg·L−1), the nitrogen removal capacity of Monoraphidium sp. was equal to its maximum removal capacity. Even at different extracellular nutrient concentrations, the Flynn model showed a linear relationship between μ and light irradiance per unit algae biomass (Iavp), when Iavp was below 18 μmol·g−1·s−1. This study highlights the promising potential of Monoraphidium sp. in MPBR. It demonstrates that considering QN and Iavp is essential for optimizing MPBR to achieve high biomass production and inorganic nutrient removal from secondary wastewater effluent.