Adsorption of an antiseptic in a functionalized fixed-bed: Analysis of breakthrough scenarios and validation of simplistic models defending a novel proposition.

BACKGROUND: Chlorhexidine gluconate (CHG) and cetrimide, which are widely used in various pharmaceutical compositions, are considered potentially hazardous compounds. This combination was largely used during and after Covid 19 pandemic for sanitization. Removal of these two compounds from pharmaceutical waste-water with commercial and functionalized activated carbon in a packed bed column is reported. METHODS: Effects of changes in bed height, flow rate, and initial concentration on the performance of the packed bed are analyzed using Yoon-Nelson, BDST and Thomas models for commercial scale-up operation. The effects of primary design parameters like bed depth and operating parameters like inflow rate and inlet concentration of influent wastewater are studied on the extent of removal of cetrimide and chlorhexidine gluconate. Granular activated carbon (GAC) is functionalized using HF and NH4OH. The extent of enhanced adsorption using the functionalized GAC is demonstrated using breakthrough curves. SIGNIFICANT FINDINGS: K. H. Chu's iconic proposition is validated. Breakthrough time (BT) increases with bed heights and it is less in the case of cetrimide as compared to chlorhexidine gluconate. This shows that cetrimide wins in the competition and occupies the pores much faster than CHG. Mostly, BT-CHG (GAC) < BT-CHG (FAC-HF) < BT-CHG (FAC-NH3) and BT-cetrimide (GAC) < BT-cetrimide (FAC-NH3) < BT-cetrimide (FAC-HF) for a particular bed height. BT-CHG(FAC-HF)BT-cetrimide(FAC-HF)

Biosorption of p-chloro meta xylenol (PCMX) by bacterium-encapsulated calcium alginate beads in a novel plug flow process.

P-Chloro-Meta-Xylenol (PCMX) is a widely used disinfectant. In the current pandemic scenario, its consumption has increased largely, and as a result, wastewater is loaded heavily with PCMX as a contaminant. Remediation of this ecologically toxic phenolic compound is therefore a burning issue. This study proposes an eco-friendly biosorption-based remediation technique to remove PCMX. A novel isolated phenol-resistant gram-negative bacterium, Pandoraea sp. strain BT102, is first encapsulated in biopolymeric calcium alginate beads. These beads are packed in a long adsorption tube and the contaminated water was passed through this packed tube resembling a plug flow reactor. This unique plug-flow set-up is capable of reducing PCMX concentration from 100 mg L-1 to 2.85 µg L-1 within 4 h using only 30 g of adsorbent, resulting in 99.99% removal efficiency. Adsorption isotherms and kinetics are studied using batch experimental data. A PCMX loading capacity of the encapsulated calcium alginate beads is found to be 961.7 mg g-1, and the Freundlich isotherm results suggested the phenomenon of cooperative adsorption. A good agreement of the pseudo-second-order kinetic model along with the intra-particle diffusion model suggests a multilayer diffusion-controlled adsorption process. Biosorption of PCMX by the bacterium-modified beads was confirmed by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), and Fourier-Transform Infrared spectroscopy (FT-IR) analyses. The application of multivariate model-based Response Surface Methodology (RSM) reveals flow rate to be the most important factor controlling the rate of bioremediation.

Odour impact assessment using kinetics and optimization: case studies on removal of multiple volatile organo-sulphur compounds from sewage wastewater using porous functional materials.

Expanding industries and booming population have led to the increase in the installation of wastewater and sewer systems, even in close proximity to residential areas. Emissions from these installations particularly volatile organo-sulphur compounds (VOSCs) such as methyl mercaptan (CH3SH), ethyl mercaptan (C2H5SH), dimethyl sulphide (CH3SCH3) and carbon disulphide (CS2) are a nuisance to people even when present in small concentration. Strategies for removal involve addition of chemicals or other chemical processes which are generally expensive. Biofilters, on the other hand, consume large amount of energy and wash waters. Hence keeping commercialization in mind, it is important to develop a strategy which would be cost-effective and at the same time be effective to remove most of the odorous compounds present in these systems. In the present research work, granular activated carbons (GAC) are functionalized with alkali solution to improve the adsorption capacity. Liquid phase batch adsorption is performed with GAC and various functionalized activated carbons (FACs) with the help of raw sewage water from a local sewage water treatment plant. Concentration of odour was evaluated by two methods-olfactometry-based analysis for sensory measurement and GCMS-based analysis for analytical estimation of a specific odorous compound. The adsorption capacities of the functionalized GACs are higher primarily because of complex formation at the surface of modified GACs. Pseudo-second-order kinetic model agreed well with experimental results with the rate constant being 0.0191 mg/l min and 0.0153 mg/l min for methyl and ethyl mercaptan adsorption onto FAC-NH3. Boyd's film diffusion along with rate kinetic model supported that chemical adsorption forms the rate-limiting step. Response surface methodology (RSM) was used to optimize the removal of VOSCs with respect to different process parameters like adsorbent amount and time. The olfactometry removal of overall odour was also optimized taking 6 factors in the Box Behnken design. Variance of analysis results indicated that all the models displayed considerable goodness of fit with R2 values close to 1. Methyl mercaptan turned out to be the highest contributor to the overall odour as confirmed both from experimental and optimization study. The optimized olfactometry odour removal (77.4%) along with CH3SH removal (80.34%), C2H5SH removal (59.16%), CH3SCH3 removal (63.21%) and CS2 removal (71.95%) was found at optimum process conditions, with amount of adsorbent of 10.29 g, adsorption time of 2.92 h. This result indicates that methyl mercaptan (CH3SH) is the highest odour contributing component out of the studied VOSCs. The results show promising potential for the use of activated carbon as an adsorbent for removal of odorous compounds from STPs.

Interference-free electrocatalysis of p-chloro meta xylenol (PCMX) on uniquely designed optimized polymeric nanohybrid of P(EDOT-co-OPD) and fMWCNT modified glassy carbon electrode.

p-Chloro-meta-Xylenol (PCMX) is an environmentally hazardous phenolic compound having biocidal and antiseptic activity. Very few research publications addressed monitoring this contaminant. This paper presents a rapid sensing system to quantify it in waste water samples. The electrochemical activity of PCMX was exploited through a unique polymeric nanocomposite modified transducer for its quantification. Poly[(3,4-Ethylenedioxythiophene)-co-(o-phenylenediamine)] [P(EDOT-co-OPD)] was deposited through one-step electropolymerization technique on the glassy carbon electrode (GCE) modified by functionalized multi-wall carbon nanotubes (fMWCNTs). An optimized combination of these constituents was evaluated using response surface methodology (RSM) based Box-Behnken experimental design. This maximized the response for PCMX using differential pulse voltammetry (DPV). The sensing matrix was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The structural and morphological study of the modified film was conducted by Fourier transform-infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), and field emission scanning electron microscope (FESEM). The anodic peak current could be read from a wide range of 0.5-225 µM calibration curve with a detection limit of 0.2545 µmol L-1. Interestingly this work did not use any biomaterial in the modification but achieved interference-free response with excellent selectivity, sensitivity (0.4668 µA µM-1 cm-2), reproducibility (RSD = 2.2%), and repeatability. The sensing platform showed good stability (85.7%) of 3 months even after 150 times repetitive use. Its applicability for real samples was established by good correlation with standard methods.

Treatment of industrial effluents and assessment of their impact on the structure and function of microbial diversity in a unique Anoxic-Aerobic sequential batch reactor (AnASBR).

A novel Anoxic-Aerobic Process (AnAP) that eliminated the anaerobic process was optimized and operated for the simultaneous remediation of phosphate, nitrate, and chemical oxygen demand (COD) from industrial effluents. Two sequential batch reactors (SBR) with AnAP were established for the treatment of effluent from two industries; phosphate fertilizer (AnASBR_PPL) and dairy industry (AnASBR_DW). The adaptability of the bacterial consortium in the SBRs, dominated by denitrifying phosphate accumulating organisms (DNPAOs), facilitates the stable performance of AnAP for simultaneous nutrient and COD removal. Up to 90% and ~80% of COD removal were achieved in AnASBR_PPL and AnASBR_DW, respectively. Nearly complete denitrification was observed along with phosphate removal accounted for ~90% in both the reactors. Granulation of sludge has been widely reported in aerobic reactors; however, interestingly, in this study, partial granulation of the sludge was observed in both the AnASBRs which facilitated the microorganisms to uptake a minimal amount of phosphate and nitrate even under the aerobic condition. The underlying mechanism of DNPAOs and other associated microbes in the consortium were investigated for microbial diversity by 16S rDNA based targeted amplicon sequencing using the Illumina platform and imputed metagenomic analysis. The dominance of Betaproteobacteria, Alphaproteobacteria, Gammaproteobacteria, and Bacteroidia was observed in AnASBRs. At steady-state operation, the identity of the core community members remained largly stable, but their relative abundances changed considerably in both the reactors as a function of varying industrial effluent. However, population of few strains such as Lactobacteriales, Enterobacteriales changed drastically with respect to the influent, as these strains were predominat in AnASBR_DW but not present in AnASBR_PPL. The dominant strains were the vital contributor to the gene pool encoding for denitrification, dephosphatation, TCA cycle, glycolysis, EPS production, and polyhydroxyalkanoate (PHA) storage, etc. Few less abundant but persistent species were also detected as contributors to these functional groups. It unveiled the TCA cycle remains preferable over conventional glycolysis in both the SBR irrespective of carbon source. The new AnASBR was proved to be an efficient alternative system that is energy efficient with higher ease of operation for the treatment of different industrial effluents without fail.

Efficacy of a novel sequential enzymatic hydrolysis of lignocellulosic biomass and inhibition characteristics of monosugars.

Efficient production of sugar monomers from lignocellulose is often hampered by serious bottle-necks in biomass hydrolysis. The present study reveals that ultra-sonication assisted pretreatment following autoclaving, termed as combined pretreatment, can lead to more efficient delignification of lignocellulosic biomass and an open, deformed polysaccharide matrix, found favorable for subsequent enzymatic hydrolysis, is formed. The pattern of inhibition for the enzymatic hydrolysis reaction on combined-pretreated saw dust is identified. Two main inhibition models (competitive and noncompetitive) are proposed and a better fit of experimental values with the theoretical values for the competitive inhibition model validates the proposition that in the present experiment, glucose inhibits the enzymes competitively. Additionally, accuracy of the inhibitory kinetics based models is estimated over a series of enzyme and substrate concentrations.

Simultaneous degumming and production of a natural gum from Crotalaria juncea seeds: Physicochemical and rheological characterization.

The oil extracted from Crotalaria juncea (Sunn-hemp) contains 70% of gum. Several methods of degumming are attempted in order to maximize the yield of gum. During appropriate water induced degumming, about 95-98% of phosphatides are separated. The maximum oil yield for two types of degummimg processes are 0.59% and 0.69% corresponding to hot water and pure O-phosphoric acid (19.88 N) treatment respectively. The % oil yield obtained for TOP degumming is about 0.78%. Physico-chemical characteristics of the isolated gum such as moisture, ash, protein, fat and aqueous solubility along with FTIR and TGA analysis are studied in order to evaluate the effect of extraction process. The behaviour of gum on the molecular scale is evaluated through alcohol treatment. Chromatographic analysis determines the monosaccharide content of the gum with glucose: xylose: arabinose::54: 34:1. Rheological characterization shows that the juncea gum solutions are shear rate dependent and the behaviour is shear-thinning (or pseudoplastic). Results show that the temperature dependent viscosity decreases with increasing shear rate.

Loss of crop yields in India due to surface ozone: an estimation based on a network of observations.

Surface ozone is mainly produced by photochemical reactions involving various anthropogenic pollutants, whose emissions are increasing rapidly in India due to fast-growing anthropogenic activities. This study estimates the losses of wheat and rice crop yields using surface ozone observations from a group of 17 sites, for the first time, covering different parts of India. We used the mean ozone for 7 h during the day (M7) and accumulated ozone over a threshold of 40 ppbv (AOT40) metrics for the calculation of crop losses for the northern, eastern, western and southern regions of India. Our estimates show the highest annual loss of wheat (about 9 million ton) in the northern India, one of the most polluted regions in India, and that of rice (about 2.6 million ton) in the eastern region. The total all India annual loss of 4.0-14.2 million ton (4.2-15.0%) for wheat and 0.3-6.7 million ton (0.3-6.3%) for rice are estimated. The results show lower crop loss for rice than that of wheat mainly due to lower surface ozone levels during the cropping season after the Indian summer monsoon. These estimates based on a network of observation sites show lower losses than earlier estimates based on limited observations and much lower losses compared to global model estimates. However, these losses are slightly higher compared to a regional model estimate. Further, the results show large differences in the loss rates of both the two crops using the M7 and AOT40 metrics. This study also confirms that AOT40 cannot be fit with a linear relation over the Indian region and suggests for the need of new metrics that are based on factors suitable for this region.

Microbial production of succinic acid using crude and purified glycerol from a Crotalaria juncea based biorefinery.

Microbial conversion of crude and purified glycerol obtained in the process of biorefining Crotalaria juncea is carried out to produce succinic acid using Escherichia coli. Batch tests are performed for nine different substrate concentrations of commercial, purified and crude glycerol, in order to observe cell growth and substrate utilization rate. Inhibitory (Halden-Andrew, Aiba-Edward, Tessier type and Andrews) as well as non-inhibitory (Monod, Moser and Tessier) models are fitted to the relationship between specific growth rate and substrate concentration obtained from the growth curves. Considering the inhibition effect, Aiba-Edward model ranked 1 out of 7 in case of two samples and Haldane-Andrew model ranked 1 in case of one sample. Aiba-Edward model gave the best fitment for a large range of concentrations of all the three types of glycerol, crude, purified and laboratory grade. Maximum production of succinic acid is obtained from commercial glycerol at pH 7 and 37.5 °C.

Analysis of ambient formaldehyde in the eastern region of India along Indo-Gangetic Plain.

Ambient levels of formaldehyde (HCHO) were measured in the tropical urban mega city of Kolkata from July 2012 to April 2014, based on USEPA Compendium Method TO-11A using 2,4-dinitrophenylhydrazine (2,4-DNPH). The samples were analyzed by isocratic reverse-phase high-performance liquid chromatography (HPLC) with an ultraviolet detector at a wavelength of 360 nm. High values of HCHO were recorded at our site. The highest and average HCHO mixing ratio measured for the entire study period was 803 and 217 ppbv respectively. Seasonal wind regimes have been found to influence the seasonal pattern of HCHO mixing ratio at this site resulting in relatively higher mixing ratio of HCHO during the pre-monsoon periods as compared to the others. Apart from these, sampling-based measurements of CH4 and continuous measurements of ozone (O3) and CO were also performed with the objective to study the interrelationship of HCHO with these species. The results suggest the presence of highly complex chemistry among them.

Variability of SO2, CO, and light hydrocarbons over a megacity in Eastern India: effects of emissions and transport.

The Indo-Gangetic plain (IGP) has received extensive attention of the global scientific community due to higher levels of trace gases and aerosols over this region. Satellite retrievals and model simulations show that, in particular, the eastern part IGP is highly polluted. Despite this attention, in situ measurements of trace gases are very limited over this region. This paper presents measurements of SO2, CO, CH4, and C2-C5 NMHCs during March 2012-February 2013 over Kolkata, a megacity in the eastern IGP, with a focus on processes impacting their levels. The mean SO2 and C2H6 concentrations during winter and post-monsoon periods were eight and three times higher compared to pre-monsoon and monsoon. Early morning enhancements in SO2 and several NMHCs during winter connote boundary layer effects. Daytime elevations in SO2 during pre-monsoon and monsoon suggest impacts of photo-oxidation. Inter-species correlations and trajectory analysis evince transport of SO2 from regional combustion sources (e.g., coal burning in power plants, industries) along the east of the Indo-Gangetic plain impacting SO2 levels at the site. However, C2H2 to CO ratio over Kolkata, which are comparable to other urban regions in India, show impacts of local biofuel combustions. Further, high levels of C3H8 and C4H10 evince the dominance of LPG/petrochemicals over the study location. The suite of trace gases measured during this study helps to decipher between impacts of local emissions and influence of transport on their levels.

Functionalized granular activated carbon and surface complexation with chromates and bi-chromates in wastewater.

Cr(VI) is present in the aqueous medium as chromate (CrO4(2-)) and bi-chromate (HCrO4(-)). Functionalized granular activated carbons (FACs) are used as adsorbents in the treatment of wastewaters containing hexavalent chromium. The FACs are prepared by chemical modifications of granular activated carbons (GACs) using functionalizing agents like HNO3, HCl and HF. The Brunauer, Emmett and Teller surface areas of FAC-HCl (693.5m(2)/g), FAC-HNO3 (648.8m(2)/g) and FAC-HF (726.2m(2)/g) are comparable to the GAC (777.7m(2)/g). But, the adsorption capacity of each of the FAC-HNO3, FAC-HCl and FAC-HF is found to be higher than the GAC. The functional groups play an important role in the adsorption process and pH has practically no role in this specific case. The FACs have hydrophilic protonated external surfaces in particular, along with the functional surface sites capable to make complexes with the CrO4(2-) and HCrO4(-) present. Surface complex formation is maximized in the order FAC-HNO3>FAC-HF>FAC-HCl, in proportion to the total surface acidity. This is also confirmed by the well-known pseudo second-order kinetic model. Physi-sorption equilibrium isotherms are parameterized by using standard Freundlich and Langmuir models. Langmuir fits better. The formation of surface complexes with the functional groups and hexavalent chromium is also revealed in the images of field emission scanning electron micrograph; energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy analysis after adsorption. The intra-particle diffusion is not the only rate-controlling factor. The Boyd's film diffusion model fits very well with R(2) as high as 98.1% for FAC-HNO3. This result demonstrates that the functionalization of the GAC by acid treatments would increase the diffusion rate, predominantly with a boundary layer diffusion effect.

Community modelling: a tool for correlating estimates of exposure with perception of odour from municipal solid waste (MSW) landfills.

Odours from municipal solid waste landfills have the potential to cause significant annoyance and impact to amenity in the environment surrounding sites. In order to assess the impact of odorous emissions on surrounding communities a quantitative model to predict annoyance was developed. The overall objective of this research was to develop the major components of the model namely, assessment of odorous emissions, dispersion and reception by the surrounding community around the landfill site. This study used community modelling as a tool to find a link between dispersion and perception of odour. The research completed a year-round monitoring program engaging people within the local community as regular odour monitors. Estimates of exposure from dispersion analysis were used to compare incidents causing complaint and intensity-concentration plots were fitted for each monitor whose reports were found to be logically consistent with regard to the intensity scaling. Human responses to the vast range of odour intensities, from highly intense source odours through to less intense dispersed odours at monitors' locations, were found to differ greatly. It was observed that the psychophysical models based on the Weber-Fechner law and Power law fitted the data consistently well for the entire range of the intensity scale used, 1-7. However, the other two models, based on Beidler's law and Laffort's equation showed an inconsistency with the intensity scales >3.

Dispersion of odour: a case study with a municipal solid waste landfill site in North London, United Kingdom.

Municipal solid waste (MSW) landfills are a potential source of offensive odours that can create annoyance within communities. Dispersion modelling was used to quantify the potential odour strength causing an impact on the community around a particular MSW landfill site north of the London area in the United Kingdom. The case studies were completed with the short-term mode of COMPLEX-I, software developed by the US-EPA. The year 1998 was chosen as a source of baseline data. It was observed that by 2004, when the landfill will progress towards the west and a big band of the area towards the north would be partly/fully restored, the maximum contribution of the new sources giving higher odour concentrations would be in the southwesterly regions away from the landfill. Concentrations as high as 25.0 ou(E)/m(3) were observed with 3 min averaging time in the southwesterly areas as compared to concentrations of 20.0 ou(E)/m(3) at 10 min averaging times. However, the percentage frequency of such critical events occurring would be low. All other surrounding farms and small villages would be exposed to the concentration of 3.0 ou(E)/m(3) on certain occasions. In the year 2008, the majority of the filling fronts would be filled with wastes with no contributions from the active and operational cells. The maximum odour concentration around the landfill site for 1 h averaging time would be approximately 3 ou(E)/m(3) about 1.0 km north and 500 m west of the landfill site. For 3 min averaging time, the stretch of 5 ou(E)/m(3) band would be up to 2.5 km towards the north of the landfill site. It is argued that further analysis of the model calculations considering effects of wind direction, frequency of wind direction, stability of the atmosphere, selected odour threshold, integration time of the model, etc. would form a basis for calculating the separation distances of the landfill site from the surrounding community.

Odour from municipal solid waste (MSW) landfills: a study on the analysis of perception.

The objective of this work was to develop a relationship between odour intensity and odour concentration by using data collected from various sensitive areas of the municipal solid waste (MSW) landfill site. A number of well-known psychophysical models (e.g., Weber-Fechner law, Steven's power law, Beidler's and Laffort's models) have been discussed that can successfully relate the perceived intensity with the odour concentration. Respective parameters for each of the models were estimated by the nonlinear Levenburg-Marquardt parameter estimation method. The overall performance of the model was tested statistically against sets of data from the olfactometry analysis. The model based on the Weber-Fechner law was ranked 1 in case of five out of nine samples and it has been found more representative of the less intense odour samples. The model based on Laffort's equation has represented the intensity-concentration relationship better with extremely low uncertainties on both parameters k1 and k2 for comparatively more intense odour samples.