Background There is concern that the microbially rich activated sludge environment of wastewater ... more Background There is concern that the microbially rich activated sludge environment of wastewater treatment plants (WWTPs) may contribute to the dissemination of antibiotic resistance genes (ARGs). We applied long-read (nanopore) sequencing to profile ARGs and their neighboring genes to illuminate their fate in the activated sludge treatment by comparing their abundance, genetic locations, mobility potential, and bacterial hosts within activated sludge relative to those in influent sewage across five WWTPs from three continents. Results The abundances (gene copies per Gb of reads, aka gc/Gb) of all ARGs and those carried by putative pathogens decreased 75–90% from influent sewage (192-605 gc/Gb) to activated sludge (31-62 gc/Gb) at all five WWTPs. Long reads enabled quantification of the percent abundance of ARGs with mobility potential (i.e., located on plasmids or co-located with other mobile genetic elements (MGEs)). The abundance of plasmid-associated ARGs decreased at four of fi...
Antimicrobial resistance (AMR) is a global threat as the existing health care may become ineffect... more Antimicrobial resistance (AMR) is a global threat as the existing health care may become ineffective. Antibiotics, antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARGs) considered as emerging contaminants are the three major components of AMR. India is one of the largest consumers of antibiotics with defined daily dose (DDD) of 4,950 per 1,000 population in 2015. By 2030, therapeutic and nontherapeutic use of antibiotics in veterinary animals is projected to increase by 18%. Antibiotics, ARB, and ARGs in the solid and liquid waste generated enter the environment via different pathways. The major sources of antibiotics, ARB, and ARG include domestic, hospital, and pharmaceutical industry wastewater apart from the solid/liquid waste generated from veterinary and food animals. Existing conventional wastewater treatment technologies like activated sludge process (ASP) do not ensure complete removal of antibiotics, ARB, and ARGs from wastewater. Similarly, the sludge generated find its way to agriculture land and eventually spread resistance in the environment. Once introduced in the environment, elimination of these contaminants is difficult. India’s action plan on AMR in 2017 regulates antibiotic use for human and animal and addresses environment AMR spread from all possible sources and containment. In 2020, the Government of India introduced discharge standard for 121 antibiotics in the effluents of bulk drug manufacturing industries, formulation industries, and common effluent treatment plant (CETP) receiving pharmaceutical wastewater.
Abstract Petroleum refining generates hazardous sludge with polyaromatic hydrocarbons and heavy m... more Abstract Petroleum refining generates hazardous sludge with polyaromatic hydrocarbons and heavy metals. The main objective of the study was to evaluate the performance of microwave pyrolysis for the recovery of oil from furnace oil sludge. The characteristics of furnace oil tank bottom sludge such as pH, moisture, viscosity, and volatile hydrocarbon content were determined. Thermal Gravimetric Analysis has been done to determine the cracking and degradation range of oily sludge. Gas Chromatography-Mass Spectrometry was used to fingerprint the hydrocarbon. Pyrolysis experiments were conducted in lab-scale pyrolysis set up with different susceptors and sludge in a specific weight ratio. The process parameters like microwave power, sludge: susceptor ratio were optimized to increase the oil yield. Graphite mixed sludge in 1:5 ratio at 450 W power shown higher oil yield. The calorific value of oil and char were determined as 44,442.9 and 16,686.58 kJ /kg. Physicochemical characteristics of oil such as flash point, density, and kinematic viscosity are 94 °C, 874.9, kg/m3, and 4.063 cSt. Cetane index and sulfur content were measured as 40.9, 6.85 g/kg respectively. The gas analysis had shown the presence of H2, CO2, CO, and CH4 compounds. Char contains a higher percentage of carbon, Fe, Al, Ni, Pb, Cd, and S compounds.
Abstract The catalytic pyrolysis of different types of polyolefin and multilayer packaging based p... more Abstract The catalytic pyrolysis of different types of polyolefin and multilayer packaging based plastic wastes in the presence of commercial zeolite catalyst was studied in the batch pilot scale reactor. Different types of multi-layer plastics such as biaxial oriented polypropylene (BOPP), metalized biaxial oriented polypropylene layers (MET/BOPP), poly ethylene terepthalate (PET), metalized polyethylene-terepthalate (MET/PET), PET combined polyethylene (PET/PE) and mixed polyolefin plastic wastes obtained from the municipal corporation were pyrolyzed to determine the oil, gas and char distribution. BOPP based plastic waste exhibited higher oil yield and calorific value (65–70%, 45.14 KJ/g) compared to PET based MLPs (17.8 %, 30 KJ/g) and laminated metalized plastics (13 %, 37 KJ/g). Modifying the feed composition by mixing of polyolefins-based waste plastics with PET based MLPs and BOPP/MET BOPP doubled the liquid yield and notably altered the physicochemical characterization of the resulted pyrolysis oil. Char yield in the polyolefins-based waste is observed to be lesser than the MLP based waste plastics. GC–MS analysis revealed the percentage area of hydrocarbons compounds of the pyrolysis oil obtained from PET based MLP experiments contains high fractions of medium and heavier range hydrocarbons (C11 – C20, C21 – C30). Sulfur content in the oil from different MLPs was measured as below the detection limit. Functional groups of hydrocarbons of oil were analyzed using FT-IR. Solids were characterized for the presence of heavy metals such as Al, Cr, Cu, Co, Pd, and Ni.
Riverine systems play an important role in the global carbon cycle, and they are considered hotsp... more Riverine systems play an important role in the global carbon cycle, and they are considered hotspots for bacterial activities such as organic matter decomposition. However, our knowledge about these processes in tropical or subtropical regions is limited. The aim of this study was to investigate anthropogenically induced changes of water quality, the distribution of selected pharmaceuticals, and the effects of pollution on greenhouse gas concentrations and bacterial community composition along the 800 km long Cauvery river, the main river serving as a potable and irrigation water supply in Southern India. We found that in situ measured pCO2 and pCH4 concentrations were supersaturated relative to the atmosphere and ranged from 7.9 to 168.7 μmol L−1, and from 0.01 to 2.76 μmol L−1, respectively. Pharmaceuticals like triclosan, carbamazepine, ibuprofen, naproxen, propylparaben, and diclofenac exceeded warning limits along the Cauvery. Proteobacteria was the major phylum in all samples,...
Simulation models that describe the flow and transport processes of pesticides in soil and ground... more Simulation models that describe the flow and transport processes of pesticides in soil and groundwater are important tools to analyze how surface pesticide applications influence groundwater quality. The aim of this study is to investigate whether the slow decline and the stable spatial pattern of atrazine concentrations after its ban, which were observed in a long-term monitoring study of pesticide concentrations in the Zwischenscholle aquifer (Germany), could be explained by such model simulations. Model simulations were carried out using MODFLOW model coupled with the HYDRUS-1D package and MT3DMS. The results indicate that the spatial variability in the atrazine application rate and the volume of water entering and leaving the aquifer through lateral boundaries produced variations in the spatial distribution of atrazine in the aquifer. The simulated and observed water table levels and the average annual atrazine concentrations were found to be comparable. The long-term analysis o...
Environmental Science and Pollution Research, 2019
Pharmaceutical contaminants present in wastewaters cause severe health hazards among chronically ... more Pharmaceutical contaminants present in wastewaters cause severe health hazards among chronically exposed population. Emerging pharmaceutically active contaminants pose a serious challenge to conventional treatment technologies. Employing advanced treatment technologies for the abatement of such contaminants is usually energy-intensive. In this study, a complex pharmaceutical wastewater from a pharmaceutical industry in California, USA, was treated by employing a novel bio-electrochemical treatment train system. Labeled “Bio-electroperoxone,” our proposed system comprises (i) an electrically bound biofilm reactor (EBBR) that accelerates bacterial adhesion for the removal of biodegradable and persistent organics and (ii) an electroperoxone reactor that removes recalcitrant organics with minimal energy uptake. The EBBR comprises a platinum-coated titanium cathode and a conductive nematic liquid crystal display electrode (NLCE) obtained from electronic waste that serves as the anode. Characterization of functional groups, morphology, and elemental mapping of NLCE were carried out to explain mechanisms for rapid biofilm attachment. The concomitant electroperoxone reactor comprises a platinum-coated titanium (Pt-Ti) anode and a reticulated vitreous carbon (RVC) cathode that catalyzes the two-electron reduction of oxygen to form in situ H2O2. The bio-electroperoxone system (i) inactivated 99.99% of the micro-organisms, removed (ii) 92.20% of the color, (iii) 84.72% of the total suspended solids, and (iv) 89% of the total organic carbon (TOC). Possible mechanisms for the degradation of organic contaminants are elucidated. Bio-electroperoxone thus paves the way for an efficient and sustainable approach for the efficient removal of both biodegradable and recalcitrant, persistent organic contaminants from pharmaceutical and possibly other complex wastewaters.
Abstract The study focuses on the biodegradation kinetics of organophosphate pesticides (OPs), ch... more Abstract The study focuses on the biodegradation kinetics of organophosphate pesticides (OPs), chlorpyrifos and dichlorvos by enriched cultures and its application in pesticide transport models. Pseudomonas aeruginosa and Taonella mepensis were the species identified in dichlorvos enriched culture (DEC) while Pseudomonas aeruginosa and Methylobacterium zatmanii were present in chlorpyrifos enriched culture (CPEC). DEC readily degraded dichlorvos as the sole carbon source at higher concentrations up to 1000 mg/L while CPEC rapidly degraded chlorpyrifos up to 100 mg/L. On addition of 1 g/L C of dextrose, dichlorvos degradation efficiency significantly increased only at higher pesticide concentrations while there was no effect on chlorpyrifos degradation. Cross-feed and mixed-feed studies highlighted that, CPEC degraded dichlorvos as a sole substrate and a mixture of both the pesticides effectively when compared to DEC. Edward inhibition and Haldane inhibition models satisfactorily simulated the biodegradation kinetics of dichlorvos and chlorpyrifos by DEC and CPEC respectively. The biokinetic parameters; maximum specific growth rate (µmax), half saturation constant (KC), yield coefficient (Y) and inhibition concentration (Ki) for the selected pesticides were thus estimated from the best fit biokinetic models. Further, batch determined biokinetic parameters were successfully applied to pesticide transport model and used to simulate breakthrough curves (BTCs) from flow-through pesticide soil column studies. The results indicated that the enriched microbes are promising candidates for insitu bioremediation of contaminated waters and soils. In addition, the estimated biokinetic constants can be used to assess the biodegradation capabilities of the enriched cultures and act as input parameters for transport models.
This study demonstrates the use of disposed liquid crystal display (LCD) glass as a supporting ma... more This study demonstrates the use of disposed liquid crystal display (LCD) glass as a supporting matrix for the fabrication of a binder/linker free thin film graphene electrode. Graphene oxide (GO) was drop casted onto the LCD matrix and electrochemically reduced to form an ErGO–LCD electrode which was subsequently employed for the electro-Fenton oxidation of ciprofloxacin. Fourier transform infrared spectroscopy confirms the presence of (i) functional groups such as C═O, N–H, C≡N, and C–N on the LCD matrix, (ii) attachment of GO onto the LCD, and (iii) reduction of oxygen functionalities at the surface of the ErGO–LCD electrode. Raman and X-ray photoelectron spectroscopy were performed to examine the nature and chemical composition of the GO–LCD and ErGO–LCD electrodes. Cyclic voltammetry and electrochemical impedance spectroscopic studies revealed the enhancement of the oxidation–reduction properties and reduction of charge transfer resistance (Rct 17 Ω) in the presence of [Fe(CN)6]3–/4– redox species. El...
PurposeSoil organic carbon enrichment by addition of organic amendments (OAs) is a common agricul... more PurposeSoil organic carbon enrichment by addition of organic amendments (OAs) is a common agricultural and gardening practice. Such amendments can cause ambiguous environmental effects; it could enhance the sorption of pesticides by increasing soil organic carbon content, and on the contrary, dissolved organic matter (DOM) from OAs could facilitate their leaching. This study evaluated the influence of OAs, mixed waste compost, and dried goat organic manure on the sorption of organophosphates, dichlorvos, and chlorpyrifos.Materials and methodsSoil (15 cm depth) was collected from an agricultural field and stored. Dissolved organic matter (DOM) extracted from the amendments and the amended soils was characterized by fluorescence spectroscopy and Fourier transform infrared spectroscopy (FT-IR). Initially, studies were carried out to evaluate the effect of DOM from organic amendments (OA-DOM) and dissolved humic acids (HAs) as model DOM on the sorption of selected pesticides. In the later part, OAs (2.5 and 5% w/w) were added to the soil, and sorption experiments were carried out using amended soil to understand the combined effects of insoluble and soluble organic carbon fraction. As dichlorvos sorption was found to be very low, desorption experiments were conducted only for chlorpyrifos using 0.01 M CaCl2 and DOM solutions.Results and discussionThe spectroscopic characterization of OA-DOM revealed that it mainly contained large amounts of highly humified and aromatic material. OA-DOM and HAs had a similar effect on pesticide sorption leading to a slight but not significant increase in dichlorvos sorption while a substantial reduction in chlorpyrifos sorption was observed. Surface tension analysis highlighted that OA-DOM and HAs might have caused greater solubilization of chlorpyrifos, thus reducing sorption. Further, it also promoted greater desorption of adsorbed chlorpyrifos. These results seem to be related to the humified and aromatic nature of OA-DOM and HAs, determining the interactions between hydrophobic chlorpyrifos and DOM. On the contrary, the addition of OAs to soil promoted greater chlorpyrifos and dichlorvos sorption, but a clear correlation between increase in soil organic carbon and pesticide sorption could not be established.ConclusionsThe study highlighted that the net effect of OA application was an increase in pesticide sorption that depended on the nature of DOM and pesticide properties. The interactions of hydrophobic chlorpyrifos with DOM can lead to a significant reduction in sorption to such an extent that the sorption in the presence of substantial DOM concentration can be less than the sorption without it.
In this paper, advanced oxidation process (AOP) combining ultrasound (US) and Fenton's proces... more In this paper, advanced oxidation process (AOP) combining ultrasound (US) and Fenton's process was proposed for the treatment of total petroleum hydrocarbons present in oil spill sludge. The effect of several parameters like pH, ultrasonic power, weight ratio of hydrogen peroxide to iron [H2O2/Fe2+], Fenton reagent dosage, addition of salts and contact time were analyzed for the reduction of Petroleum Hydrocarbons (PHCs) in terms of hydrocarbon fractions (nC7-C10, nC11-C20). Chemical characterization of oil spill sludge was analysed by gas chromatography- mass spectrum (GC-MS) Elemental analyser, Fourier Transform Infra Red (FT-IR) Analyser and particle size analyser. Experiments were conducted for identifying the wide range of hydrocarbons fractions (nC7-C10, nC11-C20 and nC21-C30). Results shown that maximum solubilisation and PHC removal rate of up to 84.25% could be achieved at a pH of 3.0, sludge/water ratio of 1:100, ultrasonic power of 100 W with 40-50% ultrasonic amplitude, a H2O2/Fe2+ weight ratio of 10:1, and an ultrasonic treatment time of 10 min. The lower and medium fractions (nC7-C10, nC11-C20) were amenable to degradation due to ultrasound treatment compared to the heavier carbon fraction (nC21-C30). The study concludes that the combined sono-Fenton (SF) process significantly enhanced the degradation of oil spill sludge as compared to ultrasound treatment and Fenton oxidation alone. The enhanced solubilisation achieved by US alone is highly beneficial when we couple this with biodegradation which will be greatly facilitated by the enhanced solubility.
Abstract Recently, hybrid capacitive deionization devices have gathered much attention due to hig... more Abstract Recently, hybrid capacitive deionization devices have gathered much attention due to high ion removal capacity, rapid ion capture and excellent stability. In this study, sodium ion battery material-reduced graphene oxide/cobalt oxide (rGO/Co3O4) has been successfully synthesized and investigated as a potential cathode for hybrid capacitive deionization (HCDI) systems for the first time. The structure and morphology of rGO and rGO/Co3O4 composites have been analyzed using XRD, FT-IR, TGA and SEM. The characterization confirms the homogeneous crystal growth of Co3O4 on the rGO sheets, with rGO weight % of 9.4 (rGO/Co3O4-A) and 25.2 (rGO/Co3O4-B). The cyclic voltammetry studies indicated that the rGO/Co3O4-B electrode exhibited high specific capacitance (210 F g−1 at 5 mV s−1) with redox properties. This paper also investigates the influence of initial concentration and voltage on the ion removal capacity of the rGO and rGO/Co3O4 composites. The rGO/Co3O4-B based HCDI system presents a significantly high ion removal capacity of 18.63 mg g−1 (250 mg L−1, 1.6 V), which is 2.8 times higher than pure rGO based CDI system (6.45 mg g−1). Also, the rGO/Co3O4 composites exhibited excellent regeneration ability indicating its potential use in high performance CDI systems.
Antibiotic resistance is a pervasive global health threat. To combat the spread of resistance, it... more Antibiotic resistance is a pervasive global health threat. To combat the spread of resistance, it is necessary to consider all possible sources and understand the pathways and mechanisms by which resistance disseminates. Best management practices are urgently needed to provide barriers to the spread of resistance and maximize the lifespan of antibiotics as a precious resource. Herein we advise upon the need for coordinated national and international strategies, highlighting three essential components: (1) Monitoring, (2) Risk Assessment, and (3) Mitigation of antibiotic resistance. Central to all three components is What exactly to monitor, assess, and mitigate? We address this question within an environmental framework, drawing from fundamental microbial ecological processes driving the spread of resistance.
Background There is concern that the microbially rich activated sludge environment of wastewater ... more Background There is concern that the microbially rich activated sludge environment of wastewater treatment plants (WWTPs) may contribute to the dissemination of antibiotic resistance genes (ARGs). We applied long-read (nanopore) sequencing to profile ARGs and their neighboring genes to illuminate their fate in the activated sludge treatment by comparing their abundance, genetic locations, mobility potential, and bacterial hosts within activated sludge relative to those in influent sewage across five WWTPs from three continents. Results The abundances (gene copies per Gb of reads, aka gc/Gb) of all ARGs and those carried by putative pathogens decreased 75–90% from influent sewage (192-605 gc/Gb) to activated sludge (31-62 gc/Gb) at all five WWTPs. Long reads enabled quantification of the percent abundance of ARGs with mobility potential (i.e., located on plasmids or co-located with other mobile genetic elements (MGEs)). The abundance of plasmid-associated ARGs decreased at four of fi...
Antimicrobial resistance (AMR) is a global threat as the existing health care may become ineffect... more Antimicrobial resistance (AMR) is a global threat as the existing health care may become ineffective. Antibiotics, antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARGs) considered as emerging contaminants are the three major components of AMR. India is one of the largest consumers of antibiotics with defined daily dose (DDD) of 4,950 per 1,000 population in 2015. By 2030, therapeutic and nontherapeutic use of antibiotics in veterinary animals is projected to increase by 18%. Antibiotics, ARB, and ARGs in the solid and liquid waste generated enter the environment via different pathways. The major sources of antibiotics, ARB, and ARG include domestic, hospital, and pharmaceutical industry wastewater apart from the solid/liquid waste generated from veterinary and food animals. Existing conventional wastewater treatment technologies like activated sludge process (ASP) do not ensure complete removal of antibiotics, ARB, and ARGs from wastewater. Similarly, the sludge generated find its way to agriculture land and eventually spread resistance in the environment. Once introduced in the environment, elimination of these contaminants is difficult. India’s action plan on AMR in 2017 regulates antibiotic use for human and animal and addresses environment AMR spread from all possible sources and containment. In 2020, the Government of India introduced discharge standard for 121 antibiotics in the effluents of bulk drug manufacturing industries, formulation industries, and common effluent treatment plant (CETP) receiving pharmaceutical wastewater.
Abstract Petroleum refining generates hazardous sludge with polyaromatic hydrocarbons and heavy m... more Abstract Petroleum refining generates hazardous sludge with polyaromatic hydrocarbons and heavy metals. The main objective of the study was to evaluate the performance of microwave pyrolysis for the recovery of oil from furnace oil sludge. The characteristics of furnace oil tank bottom sludge such as pH, moisture, viscosity, and volatile hydrocarbon content were determined. Thermal Gravimetric Analysis has been done to determine the cracking and degradation range of oily sludge. Gas Chromatography-Mass Spectrometry was used to fingerprint the hydrocarbon. Pyrolysis experiments were conducted in lab-scale pyrolysis set up with different susceptors and sludge in a specific weight ratio. The process parameters like microwave power, sludge: susceptor ratio were optimized to increase the oil yield. Graphite mixed sludge in 1:5 ratio at 450 W power shown higher oil yield. The calorific value of oil and char were determined as 44,442.9 and 16,686.58 kJ /kg. Physicochemical characteristics of oil such as flash point, density, and kinematic viscosity are 94 °C, 874.9, kg/m3, and 4.063 cSt. Cetane index and sulfur content were measured as 40.9, 6.85 g/kg respectively. The gas analysis had shown the presence of H2, CO2, CO, and CH4 compounds. Char contains a higher percentage of carbon, Fe, Al, Ni, Pb, Cd, and S compounds.
Abstract The catalytic pyrolysis of different types of polyolefin and multilayer packaging based p... more Abstract The catalytic pyrolysis of different types of polyolefin and multilayer packaging based plastic wastes in the presence of commercial zeolite catalyst was studied in the batch pilot scale reactor. Different types of multi-layer plastics such as biaxial oriented polypropylene (BOPP), metalized biaxial oriented polypropylene layers (MET/BOPP), poly ethylene terepthalate (PET), metalized polyethylene-terepthalate (MET/PET), PET combined polyethylene (PET/PE) and mixed polyolefin plastic wastes obtained from the municipal corporation were pyrolyzed to determine the oil, gas and char distribution. BOPP based plastic waste exhibited higher oil yield and calorific value (65–70%, 45.14 KJ/g) compared to PET based MLPs (17.8 %, 30 KJ/g) and laminated metalized plastics (13 %, 37 KJ/g). Modifying the feed composition by mixing of polyolefins-based waste plastics with PET based MLPs and BOPP/MET BOPP doubled the liquid yield and notably altered the physicochemical characterization of the resulted pyrolysis oil. Char yield in the polyolefins-based waste is observed to be lesser than the MLP based waste plastics. GC–MS analysis revealed the percentage area of hydrocarbons compounds of the pyrolysis oil obtained from PET based MLP experiments contains high fractions of medium and heavier range hydrocarbons (C11 – C20, C21 – C30). Sulfur content in the oil from different MLPs was measured as below the detection limit. Functional groups of hydrocarbons of oil were analyzed using FT-IR. Solids were characterized for the presence of heavy metals such as Al, Cr, Cu, Co, Pd, and Ni.
Riverine systems play an important role in the global carbon cycle, and they are considered hotsp... more Riverine systems play an important role in the global carbon cycle, and they are considered hotspots for bacterial activities such as organic matter decomposition. However, our knowledge about these processes in tropical or subtropical regions is limited. The aim of this study was to investigate anthropogenically induced changes of water quality, the distribution of selected pharmaceuticals, and the effects of pollution on greenhouse gas concentrations and bacterial community composition along the 800 km long Cauvery river, the main river serving as a potable and irrigation water supply in Southern India. We found that in situ measured pCO2 and pCH4 concentrations were supersaturated relative to the atmosphere and ranged from 7.9 to 168.7 μmol L−1, and from 0.01 to 2.76 μmol L−1, respectively. Pharmaceuticals like triclosan, carbamazepine, ibuprofen, naproxen, propylparaben, and diclofenac exceeded warning limits along the Cauvery. Proteobacteria was the major phylum in all samples,...
Simulation models that describe the flow and transport processes of pesticides in soil and ground... more Simulation models that describe the flow and transport processes of pesticides in soil and groundwater are important tools to analyze how surface pesticide applications influence groundwater quality. The aim of this study is to investigate whether the slow decline and the stable spatial pattern of atrazine concentrations after its ban, which were observed in a long-term monitoring study of pesticide concentrations in the Zwischenscholle aquifer (Germany), could be explained by such model simulations. Model simulations were carried out using MODFLOW model coupled with the HYDRUS-1D package and MT3DMS. The results indicate that the spatial variability in the atrazine application rate and the volume of water entering and leaving the aquifer through lateral boundaries produced variations in the spatial distribution of atrazine in the aquifer. The simulated and observed water table levels and the average annual atrazine concentrations were found to be comparable. The long-term analysis o...
Environmental Science and Pollution Research, 2019
Pharmaceutical contaminants present in wastewaters cause severe health hazards among chronically ... more Pharmaceutical contaminants present in wastewaters cause severe health hazards among chronically exposed population. Emerging pharmaceutically active contaminants pose a serious challenge to conventional treatment technologies. Employing advanced treatment technologies for the abatement of such contaminants is usually energy-intensive. In this study, a complex pharmaceutical wastewater from a pharmaceutical industry in California, USA, was treated by employing a novel bio-electrochemical treatment train system. Labeled “Bio-electroperoxone,” our proposed system comprises (i) an electrically bound biofilm reactor (EBBR) that accelerates bacterial adhesion for the removal of biodegradable and persistent organics and (ii) an electroperoxone reactor that removes recalcitrant organics with minimal energy uptake. The EBBR comprises a platinum-coated titanium cathode and a conductive nematic liquid crystal display electrode (NLCE) obtained from electronic waste that serves as the anode. Characterization of functional groups, morphology, and elemental mapping of NLCE were carried out to explain mechanisms for rapid biofilm attachment. The concomitant electroperoxone reactor comprises a platinum-coated titanium (Pt-Ti) anode and a reticulated vitreous carbon (RVC) cathode that catalyzes the two-electron reduction of oxygen to form in situ H2O2. The bio-electroperoxone system (i) inactivated 99.99% of the micro-organisms, removed (ii) 92.20% of the color, (iii) 84.72% of the total suspended solids, and (iv) 89% of the total organic carbon (TOC). Possible mechanisms for the degradation of organic contaminants are elucidated. Bio-electroperoxone thus paves the way for an efficient and sustainable approach for the efficient removal of both biodegradable and recalcitrant, persistent organic contaminants from pharmaceutical and possibly other complex wastewaters.
Abstract The study focuses on the biodegradation kinetics of organophosphate pesticides (OPs), ch... more Abstract The study focuses on the biodegradation kinetics of organophosphate pesticides (OPs), chlorpyrifos and dichlorvos by enriched cultures and its application in pesticide transport models. Pseudomonas aeruginosa and Taonella mepensis were the species identified in dichlorvos enriched culture (DEC) while Pseudomonas aeruginosa and Methylobacterium zatmanii were present in chlorpyrifos enriched culture (CPEC). DEC readily degraded dichlorvos as the sole carbon source at higher concentrations up to 1000 mg/L while CPEC rapidly degraded chlorpyrifos up to 100 mg/L. On addition of 1 g/L C of dextrose, dichlorvos degradation efficiency significantly increased only at higher pesticide concentrations while there was no effect on chlorpyrifos degradation. Cross-feed and mixed-feed studies highlighted that, CPEC degraded dichlorvos as a sole substrate and a mixture of both the pesticides effectively when compared to DEC. Edward inhibition and Haldane inhibition models satisfactorily simulated the biodegradation kinetics of dichlorvos and chlorpyrifos by DEC and CPEC respectively. The biokinetic parameters; maximum specific growth rate (µmax), half saturation constant (KC), yield coefficient (Y) and inhibition concentration (Ki) for the selected pesticides were thus estimated from the best fit biokinetic models. Further, batch determined biokinetic parameters were successfully applied to pesticide transport model and used to simulate breakthrough curves (BTCs) from flow-through pesticide soil column studies. The results indicated that the enriched microbes are promising candidates for insitu bioremediation of contaminated waters and soils. In addition, the estimated biokinetic constants can be used to assess the biodegradation capabilities of the enriched cultures and act as input parameters for transport models.
This study demonstrates the use of disposed liquid crystal display (LCD) glass as a supporting ma... more This study demonstrates the use of disposed liquid crystal display (LCD) glass as a supporting matrix for the fabrication of a binder/linker free thin film graphene electrode. Graphene oxide (GO) was drop casted onto the LCD matrix and electrochemically reduced to form an ErGO–LCD electrode which was subsequently employed for the electro-Fenton oxidation of ciprofloxacin. Fourier transform infrared spectroscopy confirms the presence of (i) functional groups such as C═O, N–H, C≡N, and C–N on the LCD matrix, (ii) attachment of GO onto the LCD, and (iii) reduction of oxygen functionalities at the surface of the ErGO–LCD electrode. Raman and X-ray photoelectron spectroscopy were performed to examine the nature and chemical composition of the GO–LCD and ErGO–LCD electrodes. Cyclic voltammetry and electrochemical impedance spectroscopic studies revealed the enhancement of the oxidation–reduction properties and reduction of charge transfer resistance (Rct 17 Ω) in the presence of [Fe(CN)6]3–/4– redox species. El...
PurposeSoil organic carbon enrichment by addition of organic amendments (OAs) is a common agricul... more PurposeSoil organic carbon enrichment by addition of organic amendments (OAs) is a common agricultural and gardening practice. Such amendments can cause ambiguous environmental effects; it could enhance the sorption of pesticides by increasing soil organic carbon content, and on the contrary, dissolved organic matter (DOM) from OAs could facilitate their leaching. This study evaluated the influence of OAs, mixed waste compost, and dried goat organic manure on the sorption of organophosphates, dichlorvos, and chlorpyrifos.Materials and methodsSoil (15 cm depth) was collected from an agricultural field and stored. Dissolved organic matter (DOM) extracted from the amendments and the amended soils was characterized by fluorescence spectroscopy and Fourier transform infrared spectroscopy (FT-IR). Initially, studies were carried out to evaluate the effect of DOM from organic amendments (OA-DOM) and dissolved humic acids (HAs) as model DOM on the sorption of selected pesticides. In the later part, OAs (2.5 and 5% w/w) were added to the soil, and sorption experiments were carried out using amended soil to understand the combined effects of insoluble and soluble organic carbon fraction. As dichlorvos sorption was found to be very low, desorption experiments were conducted only for chlorpyrifos using 0.01 M CaCl2 and DOM solutions.Results and discussionThe spectroscopic characterization of OA-DOM revealed that it mainly contained large amounts of highly humified and aromatic material. OA-DOM and HAs had a similar effect on pesticide sorption leading to a slight but not significant increase in dichlorvos sorption while a substantial reduction in chlorpyrifos sorption was observed. Surface tension analysis highlighted that OA-DOM and HAs might have caused greater solubilization of chlorpyrifos, thus reducing sorption. Further, it also promoted greater desorption of adsorbed chlorpyrifos. These results seem to be related to the humified and aromatic nature of OA-DOM and HAs, determining the interactions between hydrophobic chlorpyrifos and DOM. On the contrary, the addition of OAs to soil promoted greater chlorpyrifos and dichlorvos sorption, but a clear correlation between increase in soil organic carbon and pesticide sorption could not be established.ConclusionsThe study highlighted that the net effect of OA application was an increase in pesticide sorption that depended on the nature of DOM and pesticide properties. The interactions of hydrophobic chlorpyrifos with DOM can lead to a significant reduction in sorption to such an extent that the sorption in the presence of substantial DOM concentration can be less than the sorption without it.
In this paper, advanced oxidation process (AOP) combining ultrasound (US) and Fenton's proces... more In this paper, advanced oxidation process (AOP) combining ultrasound (US) and Fenton's process was proposed for the treatment of total petroleum hydrocarbons present in oil spill sludge. The effect of several parameters like pH, ultrasonic power, weight ratio of hydrogen peroxide to iron [H2O2/Fe2+], Fenton reagent dosage, addition of salts and contact time were analyzed for the reduction of Petroleum Hydrocarbons (PHCs) in terms of hydrocarbon fractions (nC7-C10, nC11-C20). Chemical characterization of oil spill sludge was analysed by gas chromatography- mass spectrum (GC-MS) Elemental analyser, Fourier Transform Infra Red (FT-IR) Analyser and particle size analyser. Experiments were conducted for identifying the wide range of hydrocarbons fractions (nC7-C10, nC11-C20 and nC21-C30). Results shown that maximum solubilisation and PHC removal rate of up to 84.25% could be achieved at a pH of 3.0, sludge/water ratio of 1:100, ultrasonic power of 100 W with 40-50% ultrasonic amplitude, a H2O2/Fe2+ weight ratio of 10:1, and an ultrasonic treatment time of 10 min. The lower and medium fractions (nC7-C10, nC11-C20) were amenable to degradation due to ultrasound treatment compared to the heavier carbon fraction (nC21-C30). The study concludes that the combined sono-Fenton (SF) process significantly enhanced the degradation of oil spill sludge as compared to ultrasound treatment and Fenton oxidation alone. The enhanced solubilisation achieved by US alone is highly beneficial when we couple this with biodegradation which will be greatly facilitated by the enhanced solubility.
Abstract Recently, hybrid capacitive deionization devices have gathered much attention due to hig... more Abstract Recently, hybrid capacitive deionization devices have gathered much attention due to high ion removal capacity, rapid ion capture and excellent stability. In this study, sodium ion battery material-reduced graphene oxide/cobalt oxide (rGO/Co3O4) has been successfully synthesized and investigated as a potential cathode for hybrid capacitive deionization (HCDI) systems for the first time. The structure and morphology of rGO and rGO/Co3O4 composites have been analyzed using XRD, FT-IR, TGA and SEM. The characterization confirms the homogeneous crystal growth of Co3O4 on the rGO sheets, with rGO weight % of 9.4 (rGO/Co3O4-A) and 25.2 (rGO/Co3O4-B). The cyclic voltammetry studies indicated that the rGO/Co3O4-B electrode exhibited high specific capacitance (210 F g−1 at 5 mV s−1) with redox properties. This paper also investigates the influence of initial concentration and voltage on the ion removal capacity of the rGO and rGO/Co3O4 composites. The rGO/Co3O4-B based HCDI system presents a significantly high ion removal capacity of 18.63 mg g−1 (250 mg L−1, 1.6 V), which is 2.8 times higher than pure rGO based CDI system (6.45 mg g−1). Also, the rGO/Co3O4 composites exhibited excellent regeneration ability indicating its potential use in high performance CDI systems.
Antibiotic resistance is a pervasive global health threat. To combat the spread of resistance, it... more Antibiotic resistance is a pervasive global health threat. To combat the spread of resistance, it is necessary to consider all possible sources and understand the pathways and mechanisms by which resistance disseminates. Best management practices are urgently needed to provide barriers to the spread of resistance and maximize the lifespan of antibiotics as a precious resource. Herein we advise upon the need for coordinated national and international strategies, highlighting three essential components: (1) Monitoring, (2) Risk Assessment, and (3) Mitigation of antibiotic resistance. Central to all three components is What exactly to monitor, assess, and mitigate? We address this question within an environmental framework, drawing from fundamental microbial ecological processes driving the spread of resistance.
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Papers by Indumathi Nambi