Ujjaini Sarkar

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, Stevens power law, Beidlers and Lafforts 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 Lafforts equation has represented the intensity-concentration relationship better with extremely low uncertainties on both parameters k1 and k2 for comparatively more intense odour samples.

Landfill odour: assessment of emissions by the flux footprint method

This paper will focus on the development of an innovative method for estimating odour fluxes and the contributing source areas from a Municipal Solid Waste (MSW) landfill site. A micrometeorological model has been developed based on the estimation of footprints of scalar odour concentration measurements in the atmospheric surface layer. The model is based on an analytical solution of the Eulerian advection-diffusion equation for vertical diffusion; model parameters include the location of the odour sensor and standard surface layer scaling factors. Lindvall Hoods are commonly used for measuring odour fluxes from ground based fugitive sources. However these cannot replicate the real atmospheric conditions. Common micrometeorological techniques for determining fluxes, such as vertical gradient measurements or eddy correlation methods, yield a flux magnitude but give practically no information about the source location. On the other hand the flux footprint describes the expansion and contraction of the required fetch under varying atmospheric stabilities. Preliminary results from the model are quite encouraging and agree well with those from Lindvall hood measurements. The accuracy of Lindvall hood measurements depends on how tightly the hood is positioned on the uneven landfill surface. It should prevent any air escaping out from the sides of the hood open to the atmosphere. Typical results show an average odour flux of ±25.91 (ou m−2 s−1) from freshly tipped wastes for an upwind fetch of 45.0 m and with the sensor at a height of 1.5 m from the ground. The hood results have a geometric mean of ±29.35 (ou m−2 s−1) based on the inlet air volume and a shade air temperature of 22.5 °C.

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 Boyds 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.

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

Highlights • Crotalaria juncea oil is trans-esterified, waste glycerol is separated and purified.• Crude, purified and commercial glycerol becomes the major carbon source for E.coli.• Succinic acid is produced by batch fermentation of glycerol using Escherichia coli.• Aiba-Edward model ranked 1 out of 7 in case of two samples.• Process parameters for the batch fermentation are optimised.

Analysis of the dynamics of a packed column using semi-empirical models: Case studies with the removal of hexavalent chromium from effluent wastewater

The dynamics of a packed bed, used for handling enormous quantities of effluent wastewater from industrial discharge, is a very important issue from a design point of view. Semi empirical Thomas and BDST Models are applied to analyze the dynamic behavior of packed beds filled in with GAC and PAC. Variations in breakthroughs with respect to exhaustion time, various bed depths, flow rates and influent solute concentrations are studied. The linearized BDST model gives very high values of R2=0.9959 (for 20% breakthrough) and R2=0.9578 (for 85% breakthrough), indicating the validity of the model for the present column system for both 20 and 85% of breakthroughs. For breakthroughs, below the 50% saturation, the BDST model is used to estimate the design of columns with various scale-ups of the process for other flow rates and initial adsorbate concentrations without any additional experiments. BDST coefficients of lower breakthroughs, below 50%, can also be used for evaluating other parameters such as critical bed depth, adsorption capacity and rate constant. The values of BDST constants, N0 and K, are not affected by changing flow rates for a particular adsorbent combination and changing influent concentrations. The validity of the Thomas model is ensured by the high R2 values, ranging from 0.855 to 0.925, while estimating the Thomas kTh and q0.

Modelling the transient behaviour of a fi xed bed considering both intra and inter-pellet diffusion for adsorption of parachloro-meta-xylenol (PCMX)

Abstract Phenols and Phenolics are considered to be potentially hazardous water pollutants. Parachlorometaxylenol (PCMX) is the major component of several disinfectants, produced commercially by well-known pharmaceutical companies. Adsorption of PCMX in various combinations of adsorbents, both natural and artificial, has been studied. Specially, water hyacinth (Eichhornia crassipes [Mart] Solms-Laubach) stems were used as adsorbent in combination with powdered activated carbon (PAC) and granular activated carbon (GAC). Five equilibrium isotherm models, namely, Tempkin Isotherm, Freundlich Isotherm, Langmuir Isotherm, Redlich-Peterson Isotherm and Toth Isotherm were studied and parameterized. The dynamics of fixed-bed adsorption columns for modeling is a demanding task due to the strong nonlinearities in the equilibrium isotherms, interference effects of the competition of solutes for adsorbent sites, mass transfer resistances between fluid phase and solid phase and fluid-dynamic dispersion phenomena. A ma...

Analysis of the photochemical production of ozone using Tropospheric Ultraviolet-Visible (TUV) Radiation Model in an Asian megacity

A study of surface layer ozone (O3) and its primary precursors (NOx = NO + NO2) was carried out at Kolkata (22° 33′ N, 88° 30′ E), an urban site in eastern India from October 2010 to April 2011. A simple NOx cycle-based photochemical model for the net rate of production of tropospheric ozone was studied. Photolytic rate constants for NO2 (jNO2