Conventional Wastewater Treatment Plants Research Articles

Degradation of micropollutants by gamma irradiation: Insight of transformation product formation explored by suspect and non-target screening using LC-HRMS

Conventional wastewater treatment systems have limitations in removing diverse micropollutants present with the complex matrix. As an alternative, advanced oxidation processes such as gamma-irradiation have been proposed. The aim of the study was to get insight into the decomposition of persistent pharmaceuticals (carbamazepine, cetirizine, tramadol) by gamma irradiation in pure water and effluent, and the formation and pathway of transformation products (TPs) identified via suspect/non-target screening using LC-HRMS. For TPs, the environmental risk assessment was also conducted with Quantitative Structure Activity Relationship (QSAR) based estimations. The decomposition effect was estimated with the removal rate and radiation chemical yield (G-value). The results indicated that the removal rate increased as the absorbed dose increased, up to 5 kGy, completely eliminating the target pharmaceuticals (initial nominal concentration: 10 mg/L) in pure water. However, the degradation in effluent was negatively affected by the organic matrix. By employing suspect/non-target screening techniques, a tentative identification of 30 transformation products (TPs) was achieved, providing insights into the degradation pathway. They were mainly formed through hydroxylation reaction by OH⸱. As a result of the QSAR estimation for the hazard of TPs, most of the TPs showed a lower risk than the parent compound. It indicates that the gamma-irradiation can be used as an alternative process to eliminate hardly degradable micropollutants in conventional wastewater treatment plant in a way to mitigate the environmental risk.

Simultaneous enhanced removal of pharmaceuticals and hormone from wastewaters using series combinations of ultra-violet irradiation, bioremediation, and adsorption technologies

Pharmaceuticals and hormones presence in effluent of conventional municipal wastewater treatment plants (WWTPs) have been widely reported. Medicinal mushrooms such as Ganoderma species and bentonite clay were recently found to have promising results in wastewater treatment with potential advantages in the removal of pharmaceuticals. Here we investigated a hybrid treatment comprising of three separate processes (no chemicals) i.e., UV irradiation, biological, adsorption (bentonite + dolomite) in a series to enhance the simultaneous removal pharmaceuticals and hormone from wastewaters (real and synthetic). In this study, fungal species Ganoderma lucidum (GLSB) and Ganoderma neo-japonicum (GJSG) are used separately in bioreactors. The work investigated removal efficiencies of four (4) pharmaceuticals and a hormone. The results showed that all investigated pharmaceuticals and hormone were removed in hybrid treatment during 54.5 h treatment. Both GLSB and GJSG reactor series treatments achieved maximum removal in both synthetic and real domestic wastewater. Overall, this study provides promising suggestions for the upgrade and design of WWTPs to simultaneous complete removal of pharmaceuticals and hormone. Present study is a beginning for future development of sustainable tertiary hybrid treatment process in addition to existing WWTPs processes to completely remove the emerging pollutants.

On the rise: Development of a multi-tiered, indoor duckweed cultivation system.

Duckweed species (Lemnaceae) are suitable for remediation and valorization of agri-feed industry wastewaters and therefore can contribute to a more sustainable, circular economy where waste is a resource. Industrial applications will, however, require space efficient cultivation methods that are not affected by prevailing weather conditions. Here, the development and operation of a multi-tiered duckweed bioreactor is described. The developed prototype bioreactor depicted in this paper is composed of four cultivation layers (1m2 each) with integrated LED lighting (generating up to 150 μmol m-2 s-1 ), a system of pumps and valves to manage the recirculatory flow (2.5Lmin-1 ) of wastewater, and an automatic harvesting system. Using a nutrient poor medium, good growth of the duckweed species Lemna minor was achieved in the bioreactor, and this was matched by strong nutrient depletion from the medium, especially for phosphorus (45-mg total phosphorus [TP] removed per m-2 day-1 ). A fully automatic harvesting arm reliably captured similar amounts of duckweed biomass across multiple harvesting cycles, revealing a future scenario whereby labor and interventions by human operators are minimized. Further developments to advance the system towards fully automated operation will include, for example, the use of specific nutrient sensors to monitor and control medium composition. It is envisaged that multi-tiered, indoor bioreactors can be employed in the agri-feed industry where wastewaters are, in many cases, continuously generated throughout the year and need remediating immediately to avoid costly storage. Given the extensive use of automation technology in conventional wastewater treatment plants, multi-tiered duckweed bioreactors can be realistically integrated within the operating environment of such treatment plants. PRACTITIONER POINTS: Duckweed is suitable for remediation and valorization of agri-feed wastewater. Industrial duckweed applications require space efficient cultivation methods. Development and operation of a multi-tiered duckweed bioreactor is detailed. Flow dynamics and automatic harvesting in the bioreactor are optimized. It is concluded that a multi-tiered bioreactor can be used in industry.

Coupled adsorption-photocatalysis process for the removal of diclofenac using magnetite/reduced graphene oxide nanocomposite

Diclofenac (DCF) is frequently detected in water bodies (ng/L to g/L) as it is not completely removed by conventional wastewater treatment plants. Adsorption and photocatalysis have been studied as promising methods for treating DCF; however, both processes have limitations. Thus, in this study, the removal efficiency of DCF is evaluated using a magnetite/reduced graphene oxide (Fe3O4/RGO) nanocomposite via a coupled adsorption-catalysis process. The Fe3O4/RGO nanocomposite was successfully synthesized using a microwave-assisted solvothermal method and exhibited a bandgap of 2.60 eV. The kinetic data best fitted the Elovich model (R2 = 0.994, χ2 = 0.29), indicating rapid adsorption. The maximum DCF adsorption capacity calculated using the Langmuir model was 80.33 mg/g. An ultraviolet C (UVC) light source and 0.1 g/L of Fe3O4/RGO nanocomposite were the optimum conditions for the removal of DCF (C0 = 30 mM) by a coupled adsorption-photocatalysis process (first-order rate constant (k) = 0.088/min), which was greater than the single adsorption (k = 0.029/min) and pre-adsorption and post-photocatalysis (k = 0.053/min) processes. This indicates that the adsorbed DCF did not hamper the photocatalytic reaction of the Fe3O4/RGO nanocomposite, but rather enhanced the coupled adsorption-photocatalytic reaction. DCF removal efficiency was higher at acidic conditions (pH 4.3–5.0), because high H+ promotes the generation of certain reactive oxygen species (ROS) and increases of electrostatic interaction. The presence of NaCl and CaCl2 (10 mM) did not notably affect the total DCF removal efficiency; however, Ca2+ affected the initial DCF adsorption affinity. Scavenger experiments demonstrated O2∙− and h+ play a key ROS than ·OH to degrade DCF. The acute toxicity of DCF towards Aliivibrio fischeri gradually decreased with increasing treatment time.

Graphene oxide quantum dots membrane: a hybrid filtration-advanced technology system to enhance process of wastewater reclamation

The inability of wastewater treatment plants to effectively remove emerging pollutants has necessitated the need to develop newer advanced technologies. An integrated approach of combining advanced oxidation processes (AOPs) and membrane technologies promises superior performances. In this study, graphene oxide quantum dots-based membranes (GQDs-Ms) were fabricated via the phase inversion method. The GQDs-Ms revealed high oxygen content and a negative surface charge. The incorporating graphene oxide quantum dots (GQDs) into the polymer matrix led to enhanced hydrophilicity, pore size, porosity, improved flux as well as superior inhibition of Escherichia coli cells. A multi-AOPs approach was used in this work, wherein AOPs were applied as both pre-treatment (using GQDs) and post-treatment (combining GQDs with peracetic acid) in the disinfection of wastewater. The evaluation of GQDs-Ms performance was carried out and compared with a commercial membrane (Film Tec™NF270). The obtained % removals with GQDs-Ms were 83.45%, 64.12%, 40.76% and 70.36% for turbidity, total dissolved solids, total organic carbon and electrical conductivity, respectively, which compared nearly with commercial membrane’s performance. Interestingly, the integrated hybrid system can further remove and inactivate microbes in wastewater. The developed hybrid filtration-advanced technology system can substantially improve conventional wastewater treatment plants for water reuse.

The Aquatic Environment and Pharmaceutical Products- A Review

In recent decades, more and more pharmaceutical products exist in the nature. In many parts of the Globe, and especially close to urban areas, medicines have been presented in surface waters, groundwaters and soils. This is related to the growth in the utilisation of medicine and the development of analytical detection techniques in order determination of these traces of compounds in the environment. Pharmaceuticals reach the nature through the discharge of effluents from urban waste water treatment plants, the discharge of effluents from hospitals and drug factories, the using of sewage sludge in agriculture, the breeding of herbivorous animals, the treatment of pets, the spreading of manure and aquaculture, the improper disposal in landfills of unused pharmaceutical substances and contaminated waste. Researches showed that pharmaceutical products and residues are mainly present in water bodies and that they are partly eliminated by conventional wastewater treatment plants, which currently cannot effectively filter all pharmaceuticals.

The Biofactory: Quantifying Life Cycle Sustainability Impacts of the Wastewater Circular Economy in Chile

The wastewater circular economy (WW-CE) represents a solution to improving sanitation coverage and management worldwide. However, the transition to circular wastewater treatment plants (WWTPs) requires facilitation to enhance decision-makers’ understanding of the integral sustainability impacts of the WW-CE. This research implemented a Life Cycle Sustainability Assessment (LCSA), combining Life Cycle Assessment, Social Life Cycle Assessment and Life Cycle Costing with a Multi-criteria Decision Making (MCDM) model to quantify the environmental, social, and economic impacts of different WWTPs technologies. Two real WWTPs (Plant A and Plant B) in Chile have embraced alternative WW-CE configurations, adopting the title Biofactories, and are considered as case studies in this investigation. A comparative LCSA considered the service of a 1,000,000-population equivalent, under three scenarios: wastewater discharge without treatment, conventional WWTPs, and biofactory WW-CE configurations. The results demonstrate that the transition to WW-CEs improved integral sustainability, and decreased integrated environmental, social, and economic impacts by 30% in Plant A, demonstrating better performance in terms environmental and social impacts. However, a 58% decrease in integral sustainability impacts for Plant B was achieved via the economic advantage of the thermal hydrolysis pre-treatment of sludge. The urgent need to adopt sustainable decision-making models to improve sanitation coverage and sustainability performance of the sanitation industry across the globe is discussed. The WW-CE in Chile presents an opportunity for this to be achieved.

Utilization of Microalgae for Urban Wastewater Treatment and Valorization of Treated Wastewater and Biomass for Biofertilizer Applications

Rapid urbanization has substantially increased freshwater consumption and consequent wastewater generation. The produced wastewater is an abundant resource of phosphorus, nitrogen, and organics. Currently, well-established activated sludge processes are utilized in conventional wastewater treatment plants to remove organics. However, removing nitrogenous and phosphorus compounds continues to be challenging and energy-intensive for urban wastewater treatment plants. Therefore, the current study aims to understand how photosynthetic microalgae can recover phosphorus and nitrogen from urban wastewater and how wastewater-grown microalgae biomass may be used as a biofertilizer and biostimulant. Utilizing microalgae biomass treated with urban wastewater as a biofertilizer promotes plant growth in a manner similar to other organic manures and conventional fertilizers while minimizing nutrient loss to the soil. Furthermore, the microalgal recovery of nutrients from urban wastewater could have potential energy reductions of 47% and 240% for nitrogen and phosphorus, respectively. In addition to producing treated wastewater suitable for a variety of irrigation systems, microalgae biomass is a potential sustainable alternative resource that could reduce conventional inorganic fertilizer usage.

Carbon footprint of a conventional wastewater treatment plant: An analysis of water-energy nexus from life cycle perspective for emission reduction

Reducing greenhouse gas (GHG) emissions is of far-reaching implications for the sustainable development of a conventional domestic wastewater treatment plant (WWTP). GHG emissions of the WWTP in different working loads were monitored to quantify the influence of critical processes on GHG emissions and shed light on the relations between direct and indirect GHG emissions with the water-energy nexus. The life cycle carbon footprint of the WWTP was assessed to find the most critical impact factor. A conceptual model of direct and indirect GHG emissions was established based on the water-energy nexus and life cycle assessment (LCA). Results showed that direct GHG emissions were highest in medium working load in May. While high indirect GHG emissions were in February, with the highest working load. Methane (CH4) emission rates, from 44.39 ± 42.49 to 4.94 ± 2.29 kg CO2e·d−1, decreased along the treatment processes due to oxidation. Dissolved CH4 in wastewater mainly came from the influent that was 0.08 ± 0.04 kg CH4·d−1. The increase of nitrous oxide (N2O) emissions and dissolved N2O occurred in the secondary treatment stage and was affected by the C/N ratio. The operation and maintenance phase had the most significant carbon footprint due to 86.4% of indirect GHG emissions from electricity usage through LCA. Electricity usage and glucose dosing were significantly correlated with N2O emissions but had no contribution to CH4 emissions. The conceptual model qualitatively demonstrated that direct and indirect GHG emissions reduced as electricity usage decreased based on the water-energy nexus. This study provided new insight into the analysis of GHG emissions from WWTPs.

Catalytic wet air oxidation of sulfamethoxazole and tetracycline using platinum-based catalysts at eco-operating conditions

Conventional wastewater treatment plants (WWTP) are unsuitable for emerging contaminants' elimination. Most of these pollutants persist after the treatment and threaten the receiving environment. Catalytic wet air oxidation (CWAO) is one of the promising solutions to treat these concentrated active molecules. This study reports the catalytic degradation tests on sulfamethoxazole (SM) and tetracycline (TET) using platinum (Pt) supported on cerium oxide (Ce) and mixed cerium and zirconium oxides (CeZr). Pt/CeZr catalyst showed 98 % TET elimination at 50 °C under atmospheric pressure (Patm). Furthermore, the test at room conditions reached 92 % removal. Pt/Ce test enabled 77 % SM elimination and reached 45 % SM mineralization. Toxicity assessment confirmed the environmental legibility of the treated solution using CWAO. The outcomes of this study showed an eco-energetic, eco-friendly, and efficient way to treat wastewater loaded with pharmaceutical pollutants.

Pharmaceutically active compounds in aqueous environment: recent developments in their fate, occurrence and elimination for efficient water purification.

The existence of pharmaceutically active compounds (PhACs) in the water is a major concern for environmentalists due to their deleterious effects on living organisms even at minuscule concentrations. This review focuses on PhACs such as analgesics and anti-inflammatory compounds, which are massively excreted in urine and account for the majority of pharmaceutical pollution. Furthermore, other PhACs such as anti-epileptics, beta-blockers and antibiotics are discussed because they also contribute significantly to pharmaceutical pollution in the aquatic environment. This review is divided into two parts. In the first part, different classes of PhACs and their fate in the wastewater environment are presented. In the second part, recent advances in the removal of PhACs by conventional wastewater treatment plants, including membrane bioreactors (MBRs), activated carbon adsorption and bench-scale studies concerning a broad range of advanced oxidation processes (AOPs) that render practical and appropriate strategies for the complete mineralization and degradation of pharmaceutical drugs, are reviewed. This review indicates that drugs like diclofenac, naproxen, paracetamol and aspirin are removed efficiently by conventional systems. Activated carbon adsorption is suitable for the removal of diclofenac and carbamazepine, whereas AOPs are leading water treatment strategies for the effective removal of reviewed PhACs.

Enhancing the selective ciprofloxacin adsorption in urine matrices through the metal-doping of carbon sorbents

Pharmaceuticals excreted after administration can pollute water sources given their ineffective removal in conventional wastewater treatment plant. Among the techniques used during tertiary wastewater treatment, adsorption is an effective and cost-efficient method for removing antibiotics. This study aimed to investigate the adsorption of ciprofloxacin (CIP) on metal-doped granular activated carbon (GAC) and evaluate the impact of urine on CIP adsorption for pristine, pre-oxidized, and metal-doped GAC. The results showed that the uptake of CIP by iron (Fe)-doped GAC was higher than Ag-doped, pre-oxidized, and pristine GAC in single-solute isotherms (DI water). This higher uptake was attributed to the presence of Fe content (1.2%) on the carbon surface, which can strongly interact with zwitterionic CIP at a neutral pH. However, when synthetic human urine was introduced, the adsorption of CIP was negatively affected due to pore blockage and competition for available sorption sites on the GAC. Among the four types of GACs tested, the lowest reduction in CIP uptake in the urine solution was observed for Fe-doped GAC followed (%17) by pre-oxidized (64%), Ag-doped (%69), and pristine F400 (76%) carbon. These results suggested that the complexation between CIP and Fe-doped GAC in urine was stronger due to its higher functionalization compared to Ag-doped, pre-oxidized, and pristine GAC. As the equilibrium concentration of CIP increased, the competition between CIP and urine decreased on the surface of Fe-doped carbon, owing to the limited competition from urine for the available active sorption sites.

Nanoscale Zero-Valent Iron (nZVI) for Heavy Metal Wastewater Treatment: A Perspective

Industries such as non-ferrous metal smelting discharge billions of gallons of highly toxic heavy metal wastewater (HMW) worldwide annually, posing a severe challenge to conventional wastewater treatment plants and harming the environment. HMW is traditionally treated via chemical precipitation using lime, caustic, or sulfide, but the effluents do not meet the increasingly stringent discharge standards. This issue has spurred an increase in research and the development of innovative treatment technologies, among which those using nanoparticles receive particular interest. Among such initiatives, treatment using nanoscale zero-valent iron (nZVI) is one of the best developed. While nZVI is already well known for its site-remediation use, this perspective highlights its application in HMW treatment with metal recovery. We demonstrate several advantages of nZVI in this wastewater application, including its multifunctionality in sequestrating a wide array of metal(loid)s (> 30 species); its capability to capture and enrich metal(loid)s at low concentrations (with a removal capacity reaching 500 mg·g−1 nZVI); and its operational convenience due to its unique hydrodynamics. All these advantages are attributable to nZVI’s diminutive nanoparticle size and/or its unique iron chemistry. We also present the first engineering practice of this application, which has treated millions of cubic meters of HMW and recovered tons of valuable metals (e.g., Cu and Au). It is concluded that nZVI is a potent reagent for treating HMW and that nZVI technology provides an eco-solution to this toxic waste.

Real-time integration of microalgae-based bioremediation in conventional wastewater treatment plants: Current status and prospects

With rising water scarcity leading to a risk of affecting 1.69 to 2.37 billion people in urban residents, the treatment and reuse of wastewater have been identified as one of the main avenues to preserve global water resources. Thus, wastewater treatment plants with capacities ranging from 8000 to 200,000 tons/day have been implemented to treat wastewater and discharge effluent with improved quality parameters. Nonetheless, the generation of 160,000–210,000 tons/year of sludge and the requirement for advanced treatment to achieve non-detectable residues are significant concerns for highly effective wastewater treatment. In this context, microalgae with the potential of effective nutrient removal from wastewater streams have been exploited in wastewater treatment at primary, secondary and tertiary treatment stages. Microalgae-based bioremediation generates valuable biomass with metabolites, namely lipids, proteins, and carbohydrates, which could be utilized in the value-added production of biofuels, biofertilizers, etc. Moreover, microalgae integrated wastewater treatment systems would substantially remove residual pollutants, nutrients, and pathogens with high removal efficiencies. Hence, the integration of microalgae into the conventional wastewater treatment process enhances the process sustainability while contributing to the concept of a circular bioeconomy. Nevertheless, limited studies are available on the potential of integrating microalgae in the conventional wastewater treatment plants for real-world applications, although several reviews are available in the literature focusing the microalgae-based wastewater treatment in a general context. Thus, the current review aims to address this gap in the literature by comprehensively assessing the prospects of integrating phycoremediation as the secondary and tertiary/advanced wastewater treatment processes, while discussing the challenges and future perspectives in the research domain.

Effect of electron beam irradiation on estrogens removal from treated wastewater

In order to remove micro pollutants such as estrogens efficiently from wastewater, it is often recommended that conventional wastewater treatment plants (WWTP) be retrofitted with an advanced oxidation process (AOP) for post-treatment purposes. This study examined the effects of electron beam (EB) absorbed dose on the removal of estrogens from biologically treated wastewater. Known concentrations of E1, E2, E3 and EE2 (0.2, 0.5, 5.0 and 10 µg/l) were spiked into samples obtained from a municipal wastewater plant, which were then irradiated with EB doses of 0.2, 2.0, 5.0 and 10.0 kGy. Levels of estrogen after irradiation were analyzed using the liquid-chromatography mass-spectrometry (LC-MS). According to the results obtained, the concentration of estrogens decreased steadily with an increasing absorbed dose up to 2 kGy. However, there was no significant increase in estrogen removal at EB doses above 2 kGy. It is estimated that the removals of the different types of estrogen are ranged from 86 % to 99 %. E2 was found to be the fastest estrogen to be degraded, followed by E3, EE2, and E1.

The role of stormwater infrastructure in regional methane emissions.

Stormwater infrastructure has been recently indicated as a potential hotspot for methane (CH4) emissions. Although local assessments based on direct CH4 measurements are increasingly available, there is currently no standardized approach for evaluating CH4 emissions from different types of stormwater infrastructure, including permanently impounded or fast-draining structures in Urban Drainage Systems (UDS). Therefore, a comparative analysis with wastewater infrastructure systems, such as wastewater treatment plants (WWTPs), is not yet possible. Here, we present a conceptual framework for the first-order quantification and upscaling of CH4 emissions from stormwater infrastructure at local and national scales. We combined in-situ and ex-situ measurements of CH4 emissions with purposely acquired data from selected stormwater facilities to provide initial estimates of CH4 emissions and emission factors for stormwater infrastructure in Germany. The results show that while stormwater infrastructure might emit comparable amounts of CH4 per area as natural and anthropogenically impacted inland waters, it may exhibit higher mean emission factors (up to 7 times) than conventional WWTPs, indicating less efficiency in limiting CH4 emissions than WWTPs. This is particularly true for permanently impounded facilities, which showed substantially higher mean surface CH4 emissions (up to 632mg m-2 d-1) than fast-draining infrastructure (0.5-1.28mg m-2 d-1). Permanently impounded sedimentation basins for stormwater management alone may reach up to 60% of the total CH4 emissions originating from WWTPs in Germany. These results are in conflict with the ongoing trend towards increasing implementation of impounded stormwater infrastructure systems, highlighting the urgent need for more extensive assessments of their impact on CH4 dynamics.

A novel approach in remediation of diclofenac from environmental water samples using silver nanocomposite polymer inclusion membrane

Diclofenac is an efficient anti-inflammatory drug used as an antipyretic and analgesia in human and animal medicine. As such they are indiscriminately consumed with or without the prescription of a physician which has led to usage above recommendation, wasted, and improper disposition; thus, has become persistently found in aqueous environment. As a result of their low solubility, they adhere strictly to biosolids during wastewater treatment which leads to incomplete removal of this contaminant by conventional wastewater treatment plants. Hence, the need for other water treatment technologies to remove this environmental stressor. Polymer inclusion membranes (PIMs) used in this study were impregnated with silver nanoparticles (AgNPs) and were investigated for the complete removal of DCF. Under optimum conditions, the best membrane's performance with 100 % transport efficiency was recorded at pH 3, with 5 % AgNPs. Further addition of AgNPs >5 % reduced the efficiency of the membranes in terms of water uptake capacity, ion-exchange capacity, permeability and transport efficiency. The stability/reusability was investigated over a 12-cyclic mass transfer. The stability of the membrane was evaluated based on the percentage mass loss and transport efficiency over the successive cycle. Thus, after the 7th cycle, about 15 % weight of the membrane was lost with a decline in transport efficiency. However, the nanocomposite PIM maintained stability with no mass losses or further decline in transport efficiency after the 7th cycle. Finally, the nanocomposite membrane was used to preconcentrate DCF from wastewater samples, and it recorded an enrichment factor between 23.5 and 24.8 and a transport efficiency between 94.1 and 99.2 %.

Sources of Antibiotic Contamination in Wastewater and Approaches to Their Removal—An Overview

In the practice of medicine, antibiotics are extremely important and are employed in the treatment of infections. A lot of antibiotics are consumed by humans and excreted via urine and feces into sewage systems and treatment plants. These are considered to be non-biodegradable, and over the years they accumulate in the aquatic environment. The presence of antibiotics in water resources causes the emergence of antibiotic-resistant bacteria, posing a serious threat to the health of human beings. Water bodies must be adequately treated before being discharged to prevent the spread of antibiotic resistance. In the present article, the sources of antibiotics and strategies used for their effective removal, such as ultrafiltration, microfiltration, nanofiltration, membranous biological reactor treatment, Advanced Oxidation Process (AOP), Reverse Osmosis (RO) and Nano sorbents, are discussed. Conventional wastewater treatment plants are not able to eliminate antibiotics deposition/resistance genes effectively and efficiently. In this regard, the adsorption method is the most effective way of removing antibiotics from wastewater from various sources.

Antibiotic ciprofloxacin removal from aqueous solutions by electrochemically activated persulfate process: Optimization, degradation pathways, and toxicology assessment

Ciprofloxacin (CIP) is a commonly used antibiotic in the fluoroquinolone group and is widely used in medical and veterinary medicine disciplines to treat bacterial infections. When CIP is discharged into the sewage system, it cannot be removed by a conventional wastewater treatment plant because of its recalcitrant characteristics. In this study, boron-doped diamond anode and persulfate were used to degrade CIP in an aquatic solution by creating an electrochemically activated persulfate (EAP) process. Iron was added to the system as a coactivator and the process was called EAP+Fe. The effects of independent variables, including pH, Fe2+, persulfate concentration, and electrolysis time on the system were optimized using the response surface methodology. The results showed that the EAP+Fe process removed 94% of CIP under the following optimum conditions: A pH of 3, persulfate/Fe2+ concentration of 0.4 mmol/L, initial CIP concentration 30 mg/L, and electrolysis time of 12.64 min. CIP removal efficiency was increased from 65.10% to 94.35% by adding Fe2+ as a transition metal. CIP degradation products, 7 pathways, and 78 intermediates of CIP were studied, and three of those intermediates (m/z 298, 498, and 505) were reported. The toxicological analysis based on toxicity estimation software results indicated that some degradation products of CIP were toxic to targeted animals, including fathead minnow, Daphnia magna, Tetrahymena pyriformis, and rats. The optimum operation costs were similar in EAP and EAP+Fe processes, approximately 0.54 €/m3.

Plant-Waste-Derived Sorbents for Nitazoxanide Adsorption.

The increased application of drugs during the COVID-19 pandemic has resulted in their increased concentration in wastewater. Conventional wastewater treatment plants do not remove such pollutants effectively. Adsorption is a cheap, effective, and environmentally friendly method that can accomplish this. On the other hand, maintaining organic waste is required. Thus, in this study, plant waste-derived pelletized biochar obtained from different feedstock and pyrolyzed at 600 °C was applied for the adsorption of nitazoxanide, an antiparasitic drug used for the treatment of SARS-CoV-2. The adsorption was fast and enables one to remove the drug in one hour. The highest adsorption capacity was noted for biochar obtained from biogas production (14 mg/g). The process of NTZ adsorption was governed by chemisorption (k2 = 0.2371 g/mg min). The presence of inorganic ions had a detrimental effect on adsorption (Cl-, NO3- in 20-30%) and carbonates were the most effective in hindering the process (60%). The environmentally relevant concentration of DOM (10 mg/L) did not affect the process. The model studies were supported by the results with a real wastewater effluent (15% reduction). Depending on the applied feedstock, various models described nitazoxanide adsorption onto tested biochars. In summary, the application of carbonaceous adsorbents in the pelletized form is effective in nitazoxanide adsorption.