Treated Wastewater Effluent Research Articles

Chemical characterization of riverine sediments affected by wastewater treatment plant effluent discharge

This study was aimed at assessing the contribution of wastewater treatment effluents to the contamination profile of the sediments of receiving waterways. Three wastewater treatment plants (WWTP) were addressed, encompassing different population equivalent sizes, urbanization degrees and treatment methods translating differences in expected contamination patterns. Within each WWTP system, the assessment targeted the effluent and sediment samples collected upstream and downstream the effluent discharge point; contaminants belonging to several concerning chemical classes (metals and metalloids; pesticides; pharmaceuticals and personal care products, PPCPs; and polycyclic aromatic hydrocarbons, PAHs) were quantified both in effluent and sediment samples. Clear associations between contaminants present in the effluent and corresponding sediment samples were not always verified. In fact, a noticeable difference between the number or abundance of contaminants detected in effluents and in sediments, suggesting that effluents are not always the most likely source (e.g. PAHs). However, sediment contaminants that were likely sourced by the effluents were also identified (e.g. PPCPs). Sediment analysis offers an important historical view of contamination, especially in flowing recipient ecosystems where any characterization over the water matrix is ephemeral and linking exclusively to the moment of sampling. Hence, sediments should be considered for the establishment of WWTP operational benchmarks regulating the emission of contaminants, which is currently focused mostly on effluent composition thus potentially over/underestimating the longer-term impact of effluent discharge in the recipient waterways.

Electroactive Ultrafiltration Membrane for Simultaneous Removal of Antibiotic, Antibiotic Resistant Bacteria, and Antibiotic Resistance Genes from Wastewater Effluent.

To combat the spread of antibiotic resistance into the environment, we should adequately manage wastewater effluent treatment to achieve simultaneous removal of antibiotics, antibiotic resistant bacteria (ARB), and antibiotic resistance genes (ARGs). Herein, we fabricate a multifunctional electroactive poly(vinylidene fluoride) ultrafiltration membrane (C/PVDF) by phase inversion on conductive carbon cloth. The membrane possesses not only excellent retention toward ARB and ARGs but also exhibits high oxidation capacity as an electrode. Notably, sulfamethoxazole degradation involving hydroxylation and hydrolysis by the anode membrane is predominant, and the degradation efficiency is up to 81.5% at +4 V. Both electro-filtration processes exhibit significant ARB inactivation, anode filtration is superior to cathode filtration. Moreover, the degradation of intracellular ARGs (iARGs) located in the genome is more efficient than those located in the plasmid, and these degradation efficiencies at -2 V are higher than +2 V. The degradation efficiencies of extracellular ARGs (eARGs) are opposite and are lower than iARGs. Compared with regular filtration, the normalized flux of electroactive ultrafiltration membrane is improved by 18.0% at -2 V, 15.9% at +2 V, and 30.4% at +4 V during treating wastewater effluent, confirming its antifouling properties and feasibility for practical application.

Fluoride pollutants removal from industrial wastewater

BackgroundThe main object of the present study is the industrial wastewater effluent treatment resulting from a solar cell manufacturing process, which is a Joint Egyptian Chinese Renewable Energy laboratory, in Sohag Governorate. Fluoric and hydrochloric acids are the main pollutants causing a pH of 1 to 3. The effluent is neutralized by the addition of both potassium hydroxide and calcium hydroxide to permit the precipitation of the resulting sparingly soluble calcium fluoride. The chlorides are partially precipitated as calcium chloride, and the further addition of hydrated aluminum sulfate is used to precipitate the remaining extra chloride as an insoluble complex to reach the allowable chloride concentration in the treated effluent. Set of experiments at bench and pilot scales were run to achieve the optimum conditions for defluorination and dichlorination taking into consideration not exceeding the allowable ranges of pollutants as soluble salts in the final effluent.ResultsExperimental results showed that the performance of a pilot scale was satisfactory in fluorides, chlorides, and dissolved solids by 97.64, 78.85, and 79.4% removal, respectively. Based on these results a full-scale industrial treatment unit was designed for construction and operation as a treatment unit for industrial wastewater contaminated with fluorides as main pollutant.ConclusionsThe recommended treatment procedure succeeded in the removal of fluorides and chlorides as main contaminants in the effluent which permit the use of treated water in the irrigation of non-edible plants, according to Egyptian Code No. (501/2015).

Submarine Outfalls of Treated Wastewater Effluents are Sources of Extensively- and Multidrug-Resistant KPC- and OXA-48-Producing Enterobacteriaceae in Coastal Marine Environment.

The rapid and ongoing spread of carbapenemase-producing Enterobacteriaceae has led to a global health threat. However, a limited number of studies have addressed this problem in the marine environment. We investigated their emergence in the coastal waters of the central Adriatic Sea (Croatia), which are recipients of submarine effluents from two wastewater treatment plants. Fifteen KPC-producing Enterobacteriaceae (nine Escherichia coli, four Klebsiella pneumoniae and two Citrobacter freundii) were recovered, and susceptibility testing to 14 antimicrobials from 10 classes showed that four isolates were extensively drug resistant (XDR) and two were resistant to colistin. After ERIC and BOX-PCR typing, eight isolates were selected for whole genome sequencing. The E. coli isolates belonged to serotype O21:H27 and sequence type (ST) 2795, while K. pneumoniae isolates were assigned to STs 37 and 534. Large-scale genome analysis revealed an arsenal of 137 genes conferring resistance to 19 antimicrobial drug classes, 35 genes associated with virulence, and 20 plasmid replicons. The isolates simultaneously carried 43–90 genes encoding for antibiotic resistance, while four isolates co-harbored carbapenemase genes blaKPC-2 and blaOXA-48. The blaOXA-48 was associated with IncL-type plasmids in E. coli and K. pneumoniae. Importantly, the blaKPC-2 in four E. coli isolates was located on ~40 kb IncP6 broad-host-range plasmids which recently emerged as blaKPC-2 vesicles, providing first report of these blaKPC-2-bearing resistance plasmids circulating in E. coli in Europe. This study also represents the first evidence of XDR and potentially virulent strains of KPC-producing E. coli in coastal waters and the co-occurrence of blaKPC-2 and blaOXA-48 carbapenemase genes in this species. The leakage of these strains through submarine effluents into coastal waters is of concern, indicating a reservoir of this infectious threat in the marine environment.

Nanofiltration as an Efficient Tertiary Wastewater Treatment: Elimination of Total Bacteria and Antibiotic Resistance Genes from the Discharged Effluent of a Full-Scale Wastewater Treatment Plant

Wastewater reuse for agricultural irrigation still raises important public health issues regarding its safety, due to the increasing presence of emerging contaminants, such as antibiotic resistant bacteria and genes, in the treated effluents. In this paper, the potential for a commercial Desal 5 DK nanofiltration membrane to be used as a tertiary treatment in the wastewater treatment plants for a more effective elimination of these pollutants from the produced effluents was assessed on laboratory scale, using a stainless steel cross-flow cell. The obtained results showed high concentrations of total bacteria and target carbapenem and (fluoro)quinolone resistance genes (blaKPC, blaOXA-48, blaNDM, blaIMP, blaVIM, qnrA, qnrB and qnrS) not only in the discharged, but also in the reused, effluent samples, which suggests that their use may not be entirely safe. Nevertheless, the applied nanofiltration treatment achieved removal rates superior to 98% for the total bacteria and 99.99% for all the target resistance genes present in both DNA and extracellular DNA fractions, with no significant differences for these microbiological parameters between the nanofiltered and the control tap water samples. Although additional studies are still needed to fully optimize the entire process, the use of nanofiltration membranes seems to be a promising solution to substantially increase the quality of the treated wastewater effluents.

Bioanalytical and chemical-specific screening of contaminants of concern in three California (USA) watersheds

To broaden the scope of contaminants monitored in human-impacted riverine systems, water, sediment, and treated wastewater effluent were analyzed using receptor-based cell assays that provide an integrated response to chemicals based on their mode of biological activity. Samples were collected from three California (USA) watersheds with varying degrees of urbanization and discharge from municipal wastewater treatment plants (WWTPs). To complement cell assay results, samples were also analyzed for a suite of contaminants of emerging concern (CECs) using gas and liquid chromatography-mass spectrometry (GC- and LC-MS/MS). For most water and sediment samples, bioassay equivalent concentrations for estrogen and glucocorticoid receptor assays (ER- and GR-BEQs, respectively) were near or below reporting limits. Measured CEC concentrations compared to monitoring trigger values established by a science advisory panel indicated minimal to moderate concern in water but suggested that select pesticides (pyrethroids and fipronil) had accumulated to levels of greater concern in river sediments. Integrating robust, standardized bioanalytical tools such as the ER and GR assays utilized in this study into existing chemical-specific monitoring and assessment efforts will enhance future CEC monitoring efforts in impacted riverine systems and coastal watersheds.

Integrated estrogenic effects and semi-volatile organic pollutants profile in secondary and tertiary wastewater treatment effluents in North China

Endocrine-disrupting effects on aquatic organisms caused by wastewater discharging have raised extensive concerns. However, the efficiency of various wastewater treatment processes to remove estrogenic activity in effluents and the association with organic micropollutants was not well known. We evaluated the estrogenic activity using a well-characterized in vivo bioassay featuring the Chinese rare minnows (Gobiocypris rarus) and analyzed 886 semi-volatile organic compounds (SVOCs) in effluents from four secondary wastewater treatment plants (SWTP A-D) and a tertiary wastewater treatment plant (TTP E) that utilized various common treatment processes in northern China. The final effluents from SWTPs and TTP E all exhibited estrogenic effects, increasing male fish plasma vitellogenin (VTG) contents and estradiol/testosterone (E2/T) ratios. Key regulating genes in the male fish liver including vtg1, vtg3, era, erβ, and cyp19a were upregulated. TTP E demonstrated high performance in reducing estrogenic activity in the effluents, with a reduction of 64% in integrative biomarkers of estrogenic response (IBR). UV disinfection at SWTPs removed IBR by 14%− 33%, while ozone disinfection at TTP E did not reduce IBR. Several SVOCs including alkanes, chlorobenzenes, and phthalates, detected at ng/L to µg/L level, significantly correlated with effluent estrogenic activity. Our findings suggest the necessity and the potential means to improve the efficiency of current wastewater treatment approaches to achieve better protection for aquatic organisms against the joint effects of mixtures of various categories of micropollutants in effluents.

Environmental impact assessment of discharge of treated wastewater effluent in Upper Iskar sub-catchment

The upper Iskar sub-catchment is one of Bulgaria’s most important economic and socially significant water sources because of its role in supplying Sofia with drinking water. Among the critical factors that carry potential high-risk levels for water quality in this hydrosystem are the discharge from the Samokov Wastewater Treatment Plant (WWTP), diffuse pollution from agriculture, and the percolation of untreated sewage from the small villages. In this study, we assessed the effect of treated wastewater effluent on water quality, and on the ecological state and microbial communities in the river sector of Samokov’s WWTP discharge area. The assessment was based on the complex use of chemical and microbiological indicators and biological quality elements. The concentrations of organics, nutrients and microcomponents were determined with results confirming the expected increase for parameters associated with the discharge of urban wastewater. The ecological state, according to macrozoobenthos indicators, was “good” throughout the river sector but local deterioration was registered in a proximal location downstream of the WWTP outfall. The analysis of stream water and bed sediment microbial communities by a fluorescent technique showed the high metabolic activity and intensive transformation processes in addition to high abundance registered with standard cultivation methods. The importance of the studied sub-catchment for the functioning of the urban water cycle, and for the quality of Sofia’s drinking water, underlines the need to extend an existing monitoring program with a more detailed assessment of the environmental impact of wastewater discharge.

Evaluation of the Adsorptive Potential of Zeolite Volcanic Tuff in Single and Binary Aqueous Solutions of the Basic Blue 41 Cationic Dye

AbstractA volcanic tuff of clinoptilolite type has been assessed in regards to its efficiency on Basic Blue 41 (BB‐41) cationic dye removal from aqueous solutions. Optimal working conditions were established by considering influences of the particle sizes, initial pH, dye concentration, contact time, and temperature. Tuff samples have been characterized by using SEM/EDX, FT‐IR, and N2 gas adsorption‐desorption techniques. Experimental data at equilibrium showed a better fitting of adsorption kinetics on pseudo‐second‐order and Langmuir models, whereas the thermodynamic parameters indicate an endothermic spontaneous process. Tuff particles of 47 μm medium sizes, which own the highest zeolite content, were found to be the most suitable for practical use as adsorbents, attaining a maximum adsorptive capacity of 123.5 mg g−1 pure dye at 323 K, equivalent to 303 mg g−1 commercial product containing 40 % dye. A potential interference involving the retention pattern was furthermore evaluated within binary systems with other two cationic dyes, Rhodamine B (RhB) and Methylene Blue (MB). The adsorbent shows a relevant selectivity towards BB‐41, influenced by commercial dye additives, structural configuration, molecular size, and contact time, with the 99.7 % dye removal efficiency at 24 hours only slightly depressed in binary systems with RhB ‐ 97.4 %, respective MB ‐ 90.2 %. This study confirmed the tuff particles as efficient adsorbents for the treatment of textile wastewater effluents.

High-efficiency treatment of electroless nickel plating effluent using core-shell MnFe2O4-C@Al2O3 combined with ozonation: Performance and mechanism

Heterogeneous catalytic ozonation (HCO) has been widely applied for the treatment of wastewater. In order to maintain the structural stability and surface catalytic activity of heterogeneous catalysts during the HCO treatment of electroless nickel plating effluent (ENPE), a MnFe2O4-C@Al2O3 catalyst with a core-shell structure was synthesized. MnFe2O4-C@Al2O3 was characterized and applied in the removal of total nickel (TNi) and organic contaminants from actual ENPE, using a coupled system of HCO combined with a magnetic dithiocarbamate chelating resin (MnFe2O4-C@Al2O3/O3-MDCR). Results show that embedding Al2O3 with C and MnFe2O4 significantly increased the TNi removal efficiency (99.3%), enhanced the O3-utilization efficiency and improved the generation of reactive oxygen species (ROS). The reaction rate (k = 0.7641 min−1) and O3-utilization efficiency established for TNi removal (ΔTNi/ΔO3 =0.221) by the MnFe2O4-C@Al2O3/O3-MDCR system, were 220% and 140% higher than the Al2O3/O3-MDCR system, respectively. Catalytic mechanism analysis demonstrated that surface hydroxyl groups, oxygen vacancy, metals, the carbon surface and its functional groups, can all potentially serve as catalytic active sites, with 1O2 and •OH considered to the predominant ROS. Overall, these findings verify that the synthesized MnFe2O4-C@Al2O3 catalyst possesses excellent catalytic capabilities and outstanding structural stability, making it suitable for practical application in the treatment of wastewater effluent.

Pharmaceuticals and personal care products (PPCPs): Environmental and public health risks

AbstractPharmaceuticals and personal care products (PPCPs) are those substances used for medical care, cosmetics, hygiene and health care purposes. Due to their globally high production and consumption rates and rapid discharge into the environment without control, they are of considerable public concern. Many of them, particularly antibiotics, analgesics, endocrine disruptors and microbial/disinfecting substances are frequently detected in wastewater treatment effluents, fresh water systems and groundwater in concentrations ranging from ng L−1 to mg L−1. Moreover, most of them are persistent and tend to bioaccumulate in cell tissue, being transported subsequently to vegetables, crops and drinking water sources. As such, a large group of PPCPs are recognized with their potential to impair the ecosystem and/or to induce health risks, so that they have been classified under “emerging contaminants.” The present study is a comprehensive review of the literature on the occurrence, fate and potential environmental and health risks of PPCPs in the aquatic and terrestrial environments. It also encompasses the reported cases of human health disorders or risks, although the data so far is inadequate for presenting a complete assessment. Finally, the study covers a short review of the most promising advanced technologies for their partial or ultimate elimination from wastewater treatment effluents and water.

Removing microplastics from wastewater using leading-edge treatment technologies: a solution to microplastic pollution-a review.

Microplastics (MPs) in environmental studies have revealed that public sewage treatment plants are a common pathway for microplastics to reach local surroundings. Microplastics are becoming more of a worry, posing a danger to both marine wildlife and humans. These plastic items not only contribute to the macrocosmic proliferation of plastics but also the scattering of microplastics and the concentration of other micropollutant-containing objects, increasing the number of pollutants identified. Microplastics' behavior, movement, transformation, and persistence mechanisms, as well as their mode of action in various wastewater effluent treatment procedures, are still unknown. They are making microplastics made from wastewater a big deal. We know that microplastics enter wastewater treatment facilities (WWTPs), that wastewater is released into the atmosphere, and that this wastewater has been considered to represent a threat to habitats and ground character based on our literature assessment. The basic methods of wastewater and sewage sludge, as well as the treatment procedure and early characterization, are covered throughout the dissection of the problematic scientific conceptualization.

Fabrication of Biochar Materials from Biowaste Coffee Grounds and Assessment of Its Adsorbent Efficiency for Remediation of Water-Soluble Pharmaceuticals

Biowaste coffee grounds have been recognized as an effective and relatively low-cost adsorbent to complement conventional treatment techniques for removing emerging contaminants (ECs) from the waste stream through modification to useful biochar. The purpose of this study was to make biochar from biowaste coffee grounds through the pyrolysis process and investigate its potential capacity for the removal of pharmaceuticals from water. The biochar was prepared by pyrolysis process under argon gas conditions, and its adsorption capacity for pharmaceuticals was evaluated. The as-prepared biochar shows a surface area of 232 m2 g−1. The adsorption of salicylic acid, diclofenac, and caffeine onto the biochar show adsorption capacities of 40.47 mg g−1, 38.52 mg g−1, and 75.46 mg g−1, respectively. The morphology, functional groups, crystallinity, and specific surface area were determined by SEM, FTIR, XRD, and BET techniques, respectively. Kinetic results reveal that the experimental data fit the pseudo-second-order model and the Temkin isotherm model. In conclusion, these results illustrate the potential of biochar produced from biowaste coffee grounds could play an important role in environmental pollution mitigation by enhancing removal of pharmaceuticals from conventional wastewater treatment effluent, thereby minimizing their potential risks in the environment.

Enhanced biological wastewater treatment using sodium alginate-immobilized microorganisms in a fluidized bed reactor

In this study, a microbial consortium isolated from an activated sludge tank of a conventional wastewater treatment plant was immobilized using sodium alginate (SA) as a support material for contaminant biodegradation in wastewater. A volume of 500 mL of activated sludge was immobilized in the SA beads (with a mass concentration of 25 g/L). The resulting SA beads were characterized, introduced into a fluidized bed reactor, fed with 1000 mL of the sample, and characterized again after the treatment process. The SA-immobilized microorganisms were tested first for degradation of organic matter (expressed as chemical oxygen demand) and total phosphorous in domestic wastewater, achieving removal efficiencies of 71% and 93%, respectively, after 12 h. Subsequently, the SA-immobilized microorganisms were tested for degradation of a basic blue 9 (BB9) textile dye in a condition that simulated textile wastewater. The efficiency of the BB9 degradation was found to be as high as 99.5% after 2 h. According to these results, SA-immobilized microorganisms were found to be an environmentally friendly and cost-effective alternative for treatment of municipal and industrial wastewater effluents.

Microplastic Pollution in Surface Waters of Urban Watersheds in Central Texas, United States: A Comparison of Sites With and Without Treated Wastewater Effluent

Most studies of microplastics in freshwater have investigated presence in creeks and rivers below sewage effluents and storm drains. This study examines microplastic distribution in surface waters, including springs and primary streams, located within small, urban Karst watersheds, with and without sources of wastewater treatment discharge. Study locales were in Texas, United States, either in Waco on the Brazos River or in or downstream from San Marcos on the San Marcos River. Research teams collected 800 ml surface water from four different small watersheds and an urban pond (n = 779) and filtered them through 53 μm Nitex mesh. Teams collected samples from springs or primary streams to the lower end of creeks and across stream transects based on distance from the bank and the presence of vegetation and debris. Teams also replicated samples seasonally. Stereo microscopy examined each filter for microplastic particles and subsequently color and type (i.e., fragment, fiber, or sphere). Additionally, we analyzed the influence of urbanization and land use on the origin and transport of the microplastics. Overall, the filters recovered 1,198 microplastic fibers and fragments. On average, 56.7% of all samples at each study locale contained microplastics. Particle abundance was the highest at Proctor Springs (x¯=3.38) and lowest at the pond (x¯=0.98), both headwaters. Local human use and runoff were thus potentially important factors in microplastic presence, while sewage discharge was not unilaterally the primary determinant of microplastic abundance. Peak pollution events occurred in June, September, and October, indicating seasonality of rainfall and recreation affected microplastic frequency and type.

Free radicals removing extracellular polymeric substances to enhance the degradation of intracellular antibiotic resistance genes in multi-resistant Pseudomonas Putida by UV/H2O2 and UV/peroxydisulfate disinfection processes

UV-based advanced oxidation processes (UV-AOPs) have been recommended to disinfect wastewater treatment plant (WWTP) effluents to control the dissemination of antibiotic resistance, but the mechanism of intracellular antibiotic resistance genes (i-ARGs) degradation by UV-AOPs is still poorly understood. Here we compared the efficacies of UV, UV/H2O2, and UV/PDS in degrading seven i-ARGs carried by a multi-drug resistant P. putida MX-2 isolated from sewage sludge and investigated the roles of free radicals and UV irradiation in degrading the carried i-ARGs in UV-AOPs. The results suggested that although UV/H2O2 and UV/PDS were only slightly superior to UV to inactivate P. putida MX-2, they significantly promoted the degradation of i-ARGs. The generated free radicals mainly reacted with the bacterial extracellular polymeric substances (EPS), increased the cell membrane permeability of bacteria, and consequently facilitated UV irradiation enter into the intracellular environment to damage the i-ARGs, thus enhancing their degradation during UV-AOPs processes. Our findings suggested that the removal of bacterial EPS by free radicals greatly contributed to the degradation of i-ARGs by UV irradiation in UV-AOPs, and more efficient approaches that are capable of removing EPS should be further developed to effectively control the dissemination of antibiotic resistance by UV treatment of wastewater effluent.

Physicochemical Characterization of Natural Rocks and Their Applications for Wastewater Treatment

Arid countries such as Arabian Gulf countries are suffering from a water shortage, especially with the recent high-water demand. The best solution for this shortage is the management of currently available water resources, through the reuse of treated wastewater for irrigation purposes. This solution also solves the problem of regularization of wastewater discharge, with positive impacts on the environment. This study aimed to apply an innovative, advanced method for treating wastewater with a favorable environment, low economic cost, and less energy consumption. The research investigated the possibility of using natural rocks such as volcanic and zeolite for advanced treatment of wastewater effluent. The research methodology relied on an experimental work in the lab scales and applied on materials available in Saudi Arabia. The experiments included a leaching batch test to first examine what leaches out from these rocks into water. Then, the materials were tested with wastewater effluent. The main mechanism of treatment was based on the absorption process. The results exhibited significant improvement in the water quality of treated wastewater. On the other hand, the results of the leaching tests showed many ions being dissolved from both rocks into water; thus, it is recommended to soak and flush these solid materials with clean water before using them for the treatment process. Further research is required to determine the best pretreated methods to be applied on these rocks to improve their performance as absorbents.

Laccase-Driven Transformation of High Priority Pesticides Without Redox Mediators: Towards Bioremediation of Contaminated Wastewaters.

In this study, Pleurotus dryinus was grown on municipal biosolids (BS) as the substrate to produce laccase for the removal of pesticides (fungicides, herbicides, and insecticides) from wastewater. Among the various types of BS tested, sterilized biosolids were the most promising substrate for laccase production by P. dryinus with a maximal laccase activity (162.1 ± 21.1 U/g dry substrate), followed by hygenized biosolids (96.7 ± 17.6 U/g dry substrate), unsterilized biosolids (UBS) (31.9 ± 1.2 U/g dry substrate), and alkali-treated biosolids (8.2 ± 0.4 U/g dry substrate). The ultrasound-assisted extraction of this enzyme from fermented UBS was carried out with 0.1 M phosphate buffer at pH 7.0, which increased the enzyme activity of the crude extract by 30%. To test the catalytic potential of the biocatalyst in real matrices, 1 U/ml of recovered crude laccase extract was applied for 24 h for the removal of 29 pesticides (nine fungicides, 10 herbicides, and 10 insecticides) either separately or as a mixture from spiked biologically treated wastewater effluent. When treated with crude enzyme extract, high-priority herbicides metolachlor and atrazine were completely removed, while 93%–97% of the insecticides aldicarb, spinosad, and azinphos-methyl and up to 91% of kresoxim-methyl were removed. Promising results were obtained with BS-derived crude enzyme extract exhibiting improved pesticides removal, which may be due to the mediator effect resulting from the catalytic transformation of other molecules in the cocktail. The results demonstrated a promising integrated bioprocess for the removal of pesticides in wastewater using crude laccase obtained from BS.

Enhanced production of microalgae-originated photosensitizer by integrating photosynthetic electrons extraction and antibiotic induction towards photocatalytic degradation of antibiotic: A novel complementary treatment process for antibiotic removal from effluent of conventional biological wastewater treatment

Antibiotic residues in effluents from bio-treated wastewaters are mainly responsible for the spread of antibiotic resistance genes in the environment. Conventional physicochemical treatments are thought to be unsustainable due to high energy consumption, large consumption of chemicals and environmental unfriendly processing step. In this study, a novel approach by integrating photosynthetic electrons extraction from microalgae with antibiotic induction was used to enhance the production of microalgae-originated photosensitizer for photolytic removal of antibiotic residues in effluents from conventional bio-treated wastewaters. Results showed that the accumulation of photoactive substances in extracellular polymeric substance (EPS) of chlorella vulgaris was positively related to the amounts of photosynthetic electrons extracted by the electrode which is a potential-dependent process and can be further enhanced by tetracycline (TC) induction. The protein and humic acid which are considered two main photoactive substances in EPS produced at 0.6 V accumulated to a high level of 320 and 24 μg/cm3 and were further increased to 380 and 48 μg/cm3 when TC was added which were 4.7 and 6.4-folds higher than that produced at potential free in the absence of TC. The EPS produced at 0.6 and 0.8 V led to 1.34 and 1.53-fold acceleration in photosensitized degradation of TC compared to that of EPS free in secondary effluent of municipal wastewater treatment plant. The complex heterocyclic ring structure of TC was broken down into simple monocyclic aromatic compounds, indicating a marked reduction in biotoxicity and recalcitrance. The hydroxyl radical played a main role for the photolysis of TC followed by singlet oxygen. This technology provides a new alternative to conventional physicochemical treatment as complementary treatment processes for biological wastewater treatment in terms of antibiotics removal.

Polystyrene nanoplastics and wastewater displayed antagonistic toxic effects due to the sorption of wastewater micropollutants

The knowledge about the interaction of nanoplastics with other aquatic pollutants and their combined effects on biota is very scarce. In this work, we studied the interaction between polystyrene nanoplastics (PS NPs) (30 nm) and the micropollutants in a biologically treated wastewater effluent (WW). The capacity of PS NPs to sorb micropollutants was studied as well as their single and combined toxicity towards three freshwater organisms: the recombinant bioluminescent cyanobacterium, Anabaena sp. PCC 7120 CPB4337; the duckweed, Spirodela polyrhiza and the cladoceran, Daphnia magna. The endpoints were the inhibition of bioluminescence, the growth inhibition of the aquatic plant and the immobilization of D. magna after 24, 72 and 48 h of exposure, respectively. Combination Index (CI)-isobologram method was used to quantify mixture toxicity and the nature of interactions. PS NPs sorbed a variety of chemicals present in WW as micropollutants in a range of tens of ng/L to μg/L. It was found that those pollutants with positive charge were the main ones retained onto PS NPs, which was attributed to the electrostatic interaction with the negatively charged PS NPs. Regarding the toxicological effects, single exposure to PS NPs affected the three tested organisms. However, single exposure to WW only had a negative impact on the cyanobacterium and S. polyrhiza with no observed toxicity to D. magna. Regarding PS NPs-WW combined exposure, a reduction of toxicity in comparison with single exposure was observed probably due to the sorption of micropollutants onto PS NPs, which resulted in lower bioavailability of the micropollutants. In addition, the formation of PS NPs-WW heteroaggregates was observed which could result in lower bioavailability of PS NPs and sorbed micropollutants, thus lowering toxicity. This study represents a near-realistic scenario approach to the potential sorption of wastewater pollutants onto nanoplastics that could alter the toxicological effect on the biota.