Rakesh Govind | University of Cincinnati (original) (raw)

Papers by Rakesh Govind

This paper provides an overview of air biofiltration with experimental data on the performance of... more This paper provides an overview of air biofiltration with experimental data on the performance of peat/compost, pelletized packed bed and structured media biofilters. It is shown that use of high surface area per unit volume structured media results in higher contaminant treatment rates per unit biofilter volume. Peat/compost biofilters exhibit lower removal efficiencies at high (> 100 ppmv) inlet contaminant concentrations and require control of media moisture content. Increase of temperature results in increasing biodegradation rates. It is shown that use of structured ceramic media allows effective control of biomass buildup by continuous removal of biomass from the biofilter media and that the biomass removal rate depends on nutrient flowrate. An experimental system is presented which enables biofilm kinetics to be determined and a simple biofilter model is developed in this paper. A group contribution approach has been developed to estimate biokinetic parameter which allows biofiltration effectiveness to be determined for a variety of volatile organic compounds (VOCs). Finally, a procedure is presented, illustrated by an example, which is used to develop an integrated process for effective treatment of air contaminants. 22 refs., 12 figs., 4 tabs.

Proceedings of the Water Environment Federation, 2010

Proceedings of the Water Environment Federation, 2000

Proceedings of the Water Environment Federation, 2000

IEEE Transactions on Automatic Control, 1981

Water Science and Technology, Aug 1, 1992

Biodegradation is an important mechanism determining the fate of chemicals in the aquatic environ... more Biodegradation is an important mechanism determining the fate of chemicals in the aquatic environment. In this paper, experimental data, determined from electrolytic respirometry, for 27 compounds were analyzed using first order and Monod kinetics. Additional data from the literature were also used in our analysis. A method based on group contribution to predict first-order and Monod kinetic rate constants was developed and validated. The group contribution approach gave reasonable results for a variety of compounds. More kinetic data are required to extend the group contribution approach.

Sorption - From Fundamentals to Applications

Sorption in wastewater solids is an important removal mechanism for pollutants in biological trea... more Sorption in wastewater solids is an important removal mechanism for pollutants in biological treatment systems. It is often an overlooked mechanism, since traditionally, excess solids from biological treatment were land filled. However, with the emergence of using wastewater solids as a potential fertilizer, pollutants sorbed into the solids can re-emerge as soil pollutants, with potential uptake by crops, and even transported into groundwater. This is especially applicable for hydrophobic chemicals, like alkyl fluorinated compounds (PFAS, PFOS), which have recently received widespread attention as pollutants in water bodies across the globe. In this chapter, sorption of pollutants in wastewater solids has been presented from both a thermodynamic analysis, involving equilibrium parameters, as well as a kinetic process involving transport to the cell walls and permeation through the cell membranes. Based on experimental data and models it is shown that biodegradation in wastewater sy...

IEEE Transactions on Automatic Control, 1977

Proceedings of the Water Environment Federation, 2010

Circulating Fluidized Bed Technology, 1988

ABSTRACT In this paper, a novel coal combustor termed “Swirling Circulating Fluidized Bed (SCFB)”... more ABSTRACT In this paper, a novel coal combustor termed “Swirling Circulating Fluidized Bed (SCFB)” has been studied. The SCFB is a circulating fluidized bed with tangential injection of the secondary air. Studies on hydrodynamics using cold model and combustion using a pilot plant have been conducted. The system has also been simulated and good agreement has been achieved with the experimental data. The advantages of the swirling action in the bed over the traditional circulating bed have been discussed.

Journal of Chemical Engineering & Process Technology, Oct 24, 2017

Biomass, Biorefineries and Bioeconomy, 2022

The objective of this work was to develop a systematic strategy for generating efficient, alterna... more The objective of this work was to develop a systematic strategy for generating efficient, alternate reaction paths that could be used to manufacture the top 100 industrial chemicals, currently produced from crude oil, using renewable feedstocks. Manufacturing these chemicals from oil, coal, or natural gas results in increasing carbon dioxide levels in the atmosphere, responsible for global climate change. The methodology employed here uses the existing knowledge on the conversion of carbon-neutral feedstocks, such as biomass, wood, etc., to suitable precursor raw materials. Known industrial reaction paths, currently used for manufacturing the top 100 industrial organic chemicals, are then combined with the known conversion of carbon-neutral feedstocks to systematically develop and evaluate alternate carbon-efficient reaction paths. The fractional carbon economy was determined from a comprehensive listing of industrial reactions paths, which also gives the yields and efficiencies of ...

Springer eBooks, 1996

Knowledge of half-lives or biodegradation rate constants in soil is useful for estimating the nat... more Knowledge of half-lives or biodegradation rate constants in soil is useful for estimating the natural attenuation rates of contaminants due to microbial transformations and to make decisions regarding treatment action or no treatment with isolation of the contaminated site to minimize exposure to animal and human life. Half-life is defined as the time required for 50 % of the contaminant to be biodegraded. Soil treatment is time consuming and expensive, and often for large isolated contaminated sites, relying on natural attenuation may be the most cost-effective solution. In this paper, a neural network is trained to estimate the range of half-lives for organic contaminants in soil. Soil half-life data, obtained from the literature for 258 chemicals is correlated with 14 molecular fragments or indicators using a back-propagation neural network with 14 input nodes, 12 nodes in the hidden layer and 2 output nodes. A cross-validation method was used to test the neural network. The converged neural network produced less than 50 % relative error for more than 80 % of the chemicals in the training set. Using a classification scheme of fast (half-life range of 1 to 7 days), moderately fast (half-life range from 7 to 28 days), slow (half-life range from 28 to 180 days) and resistant (half-life range from 180 to 365 days), the neural network was able to correctly classify more than 95 % of the 258 chemicals in the database.

Humana Press eBooks, Nov 14, 2003

Bioremediation of polluted soil requires a fundamental understanding of biodegradation kinetics a... more Bioremediation of polluted soil requires a fundamental understanding of biodegradation kinetics and the physicochemical factors that control the rate of biodegradation. A systematic multi-level protocol based on three types of bioreactor systems, was developed to determine the biokinetic parameters of the suspended and immobilized microbiota and the transport and diffusivity parameters of soil contaminants and oxygen in the soil matrix. In the soil slurry reactor, significant biodegradation occurs in the aqueous phase by the suspended and immobilized microbiota and to some extent by the soil immobilized biofilms. The soil slurry reactor data were used to derive the biokinetic parameters for the suspended and immobilized microorganisms. The wafer reactor data were used to obtain additional information on biokinetic and transport parameters with oxygen limitation. The porous tube reactor data provided quantitative determination of oxygen diffusivity. In the soil tube reactor, oxygen l...

ACS Symposium Series, 1993

... Development of Nonlinear Group Contribution Method for Prediction of Biodegradation Kinetics ... more ... Development of Nonlinear Group Contribution Method for Prediction of Biodegradation Kinetics from Respirometrically Derived Kinetic Data Henry H. Tabak1 and Rakesh Govind2 ... He also attempted correlations using the steric and lipophilic constants but failed. Vaishnav et al. ...

This paper provides an overview of air biofiltration with experimental data on the performance of... more This paper provides an overview of air biofiltration with experimental data on the performance of peat/compost, pelletized packed bed and structured media biofilters. It is shown that use of high surface area per unit volume structured media results in higher contaminant treatment rates per unit biofilter volume. Peat/compost biofilters exhibit lower removal efficiencies at high (> 100 ppmv) inlet contaminant concentrations and require control of media moisture content. Increase of temperature results in increasing biodegradation rates. It is shown that use of structured ceramic media allows effective control of biomass buildup by continuous removal of biomass from the biofilter media and that the biomass removal rate depends on nutrient flowrate. An experimental system is presented which enables biofilm kinetics to be determined and a simple biofilter model is developed in this paper. A group contribution approach has been developed to estimate biokinetic parameter which allows biofiltration effectiveness to be determined for a variety of volatile organic compounds (VOCs). Finally, a procedure is presented, illustrated by an example, which is used to develop an integrated process for effective treatment of air contaminants. 22 refs., 12 figs., 4 tabs.

Proceedings of the Water Environment Federation, 2010

Proceedings of the Water Environment Federation, 2000

Proceedings of the Water Environment Federation, 2000

IEEE Transactions on Automatic Control, 1981

Water Science and Technology, Aug 1, 1992

Biodegradation is an important mechanism determining the fate of chemicals in the aquatic environ... more Biodegradation is an important mechanism determining the fate of chemicals in the aquatic environment. In this paper, experimental data, determined from electrolytic respirometry, for 27 compounds were analyzed using first order and Monod kinetics. Additional data from the literature were also used in our analysis. A method based on group contribution to predict first-order and Monod kinetic rate constants was developed and validated. The group contribution approach gave reasonable results for a variety of compounds. More kinetic data are required to extend the group contribution approach.

Sorption - From Fundamentals to Applications

Sorption in wastewater solids is an important removal mechanism for pollutants in biological trea... more Sorption in wastewater solids is an important removal mechanism for pollutants in biological treatment systems. It is often an overlooked mechanism, since traditionally, excess solids from biological treatment were land filled. However, with the emergence of using wastewater solids as a potential fertilizer, pollutants sorbed into the solids can re-emerge as soil pollutants, with potential uptake by crops, and even transported into groundwater. This is especially applicable for hydrophobic chemicals, like alkyl fluorinated compounds (PFAS, PFOS), which have recently received widespread attention as pollutants in water bodies across the globe. In this chapter, sorption of pollutants in wastewater solids has been presented from both a thermodynamic analysis, involving equilibrium parameters, as well as a kinetic process involving transport to the cell walls and permeation through the cell membranes. Based on experimental data and models it is shown that biodegradation in wastewater sy...

IEEE Transactions on Automatic Control, 1977

Proceedings of the Water Environment Federation, 2010

Circulating Fluidized Bed Technology, 1988

ABSTRACT In this paper, a novel coal combustor termed “Swirling Circulating Fluidized Bed (SCFB)”... more ABSTRACT In this paper, a novel coal combustor termed “Swirling Circulating Fluidized Bed (SCFB)” has been studied. The SCFB is a circulating fluidized bed with tangential injection of the secondary air. Studies on hydrodynamics using cold model and combustion using a pilot plant have been conducted. The system has also been simulated and good agreement has been achieved with the experimental data. The advantages of the swirling action in the bed over the traditional circulating bed have been discussed.

Journal of Chemical Engineering & Process Technology, Oct 24, 2017

Biomass, Biorefineries and Bioeconomy, 2022

The objective of this work was to develop a systematic strategy for generating efficient, alterna... more The objective of this work was to develop a systematic strategy for generating efficient, alternate reaction paths that could be used to manufacture the top 100 industrial chemicals, currently produced from crude oil, using renewable feedstocks. Manufacturing these chemicals from oil, coal, or natural gas results in increasing carbon dioxide levels in the atmosphere, responsible for global climate change. The methodology employed here uses the existing knowledge on the conversion of carbon-neutral feedstocks, such as biomass, wood, etc., to suitable precursor raw materials. Known industrial reaction paths, currently used for manufacturing the top 100 industrial organic chemicals, are then combined with the known conversion of carbon-neutral feedstocks to systematically develop and evaluate alternate carbon-efficient reaction paths. The fractional carbon economy was determined from a comprehensive listing of industrial reactions paths, which also gives the yields and efficiencies of ...

Springer eBooks, 1996

Knowledge of half-lives or biodegradation rate constants in soil is useful for estimating the nat... more Knowledge of half-lives or biodegradation rate constants in soil is useful for estimating the natural attenuation rates of contaminants due to microbial transformations and to make decisions regarding treatment action or no treatment with isolation of the contaminated site to minimize exposure to animal and human life. Half-life is defined as the time required for 50 % of the contaminant to be biodegraded. Soil treatment is time consuming and expensive, and often for large isolated contaminated sites, relying on natural attenuation may be the most cost-effective solution. In this paper, a neural network is trained to estimate the range of half-lives for organic contaminants in soil. Soil half-life data, obtained from the literature for 258 chemicals is correlated with 14 molecular fragments or indicators using a back-propagation neural network with 14 input nodes, 12 nodes in the hidden layer and 2 output nodes. A cross-validation method was used to test the neural network. The converged neural network produced less than 50 % relative error for more than 80 % of the chemicals in the training set. Using a classification scheme of fast (half-life range of 1 to 7 days), moderately fast (half-life range from 7 to 28 days), slow (half-life range from 28 to 180 days) and resistant (half-life range from 180 to 365 days), the neural network was able to correctly classify more than 95 % of the 258 chemicals in the database.

Humana Press eBooks, Nov 14, 2003

Bioremediation of polluted soil requires a fundamental understanding of biodegradation kinetics a... more Bioremediation of polluted soil requires a fundamental understanding of biodegradation kinetics and the physicochemical factors that control the rate of biodegradation. A systematic multi-level protocol based on three types of bioreactor systems, was developed to determine the biokinetic parameters of the suspended and immobilized microbiota and the transport and diffusivity parameters of soil contaminants and oxygen in the soil matrix. In the soil slurry reactor, significant biodegradation occurs in the aqueous phase by the suspended and immobilized microbiota and to some extent by the soil immobilized biofilms. The soil slurry reactor data were used to derive the biokinetic parameters for the suspended and immobilized microorganisms. The wafer reactor data were used to obtain additional information on biokinetic and transport parameters with oxygen limitation. The porous tube reactor data provided quantitative determination of oxygen diffusivity. In the soil tube reactor, oxygen l...

ACS Symposium Series, 1993

... Development of Nonlinear Group Contribution Method for Prediction of Biodegradation Kinetics ... more ... Development of Nonlinear Group Contribution Method for Prediction of Biodegradation Kinetics from Respirometrically Derived Kinetic Data Henry H. Tabak1 and Rakesh Govind2 ... He also attempted correlations using the steric and lipophilic constants but failed. Vaishnav et al. ...