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Papers by Tanush Wadhawan

Research paper thumbnail of A Novel Application of Enricher Reactor - Permeable Reactive Biobarrier for Removing a Mixture of Contaminants with Substrate Interactions

Proceedings of the Water Environment Federation, 2012

Research paper thumbnail of Role of Manure Application on Soil in Preventing Groundwater Contamination by <I>Cryptosporidium</I>

Proceedings of the Water Environment Federation, 2011

Research paper thumbnail of Modeling a Two-Stage Trickling Filter Wastewater Treatment Plant to Simulate the Fate of Dissolved Organic Nitrogen and Its Biodegradability

Proceedings of the Water Environment Federation, 2011

Research paper thumbnail of Urea Responsible for Aggregation in Bacterial Strains Commonly Found in Activated Sludge

Proceedings of the Water Environment Federation, 2013

Research paper thumbnail of Reintroduction of Contaminant in Groundwater Alters Bacterial Community

Proceedings of the Water Environment Federation, 2012

Research paper thumbnail of Dissolved organic nitrogen and its biodegradable portion in a water treatment plant with ozone oxidation

Water Research, 2014

Biodegradable dissolved organic nitrogen (BDON) Dissolved organic nitrogen (DON) Total dissolved ... more Biodegradable dissolved organic nitrogen (BDON) Dissolved organic nitrogen (DON) Total dissolved nitrogen (TDN)

Research paper thumbnail of Assessing tetrazolium and ATP assays for rapid in situ viability quantification of bacterial cells entrapped in hydrogel beads

Entrapped bacteria are used in several applications including food and beverage production, antib... more Entrapped bacteria are used in several applications including food and beverage production, antibiotic production, and wastewater treatment. To date in order to determine the viability of entrapped bacteria, they have to be de-entrapped from the matrix first. However, the cell de-entrapment procedures such as matrix dissolution by acid or heating at high temperatures, may affect the viability of the cells. In this study, the uses of two quantitative approaches for in situ viability estimation of calcium alginate and phosphorylated poly(vinyl) alcohol (PPVA) entrapped Escherichia coli were investigated. Bioreducible tetrazolium salt (XTT) and adenosine triphosphate (ATP) based assays were used to determine microbial viability without the dissolution of the matrices (spherical beads). The data from both assays showed linearity and strong correlations between the viability signals and number of beads in which each bead contained a similar number of live cells. An application of XTT assay on the PPVA entrapped bacterial beads was an exception to these results. Effects of the acid and heat dissolution de-entrapment procedures on cell viability were also evaluated by using both assays and a traditional plate count method. The heating process showed the greatest reduction in bacterial viability when compared to the other de-entrapment procedures. The ATP assay is a more sensitive and less time consuming approach for viability estimation when compared to the XTT assay and traditional plate count method. Both XTT and ATP assays have potential for use in quantifying the viability of entrapped bacteria.

Research paper thumbnail of A new method to determine initial viability of entrapped cells using fluorescent nucleic acid staining

Bioresource technology, 2011

Entrapped bacterial cells are widely used in several biotechnological applications. Cell entrapme... more Entrapped bacterial cells are widely used in several biotechnological applications. Cell entrapment procedures are known to affect the viability of bacterial cells. To determine the effect of entrapment procedures on viability of bacterial cells, dissolution of the entrapment matrices using chelating agents or heat is required immediately after the entrapment is completed. Chelating agents and heat applied in the matrix dissolution reduce cell viability and in turn hinder accurate quantification of viable cells. In this study, a method to determine the effect of entrapment procedure on bacterial cell viability which involves entrapping cells directly onto glass slides was developed. The developed method showed less viability reduction than the methods requiring matrix dissolution. The percentage of live cells in the culture before entrapment ranged from 54% to 74%, while the percent of live cells after entrapment determined by the developed method was 39-62%.

Research paper thumbnail of Fate of dissolved organic nitrogen in two stage trickling filter process

Water Research, 2012

Biodegradable dissolved organic nitrogen (BDON) Dissolved organic nitrogen (DON) Total dissolved ... more Biodegradable dissolved organic nitrogen (BDON) Dissolved organic nitrogen (DON) Total dissolved nitrogen (TDN) Trickling filters Wastewater BioWin modeling a b s t r a c t Dissolved organic nitrogen (DON) represents a significant portion of nitrogen in the final effluent of wastewater treatment plants (WWTPs). Biodegradable portion of DON (BDON) can support algal growth and/or consume dissolved oxygen in the receiving waters. The fate of DON and BDON has not been studied for trickling filter WWTPs. DON and BDON data were collected along the treatment train of a WWTP with a two-stage trickling filter process. DON concentrations in the influent and effluent were 27% and 14% of total dissolved nitrogen (TDN). The plant removed about 62% and 72% of the influent DON and BDON mainly by the trickling filters. The final effluent BDON values averaged 1.8 mg/L. BDON was found to be between 51% and 69% of the DON in raw wastewater and after various treatment units. The fate of DON and BDON through the two-stage trickling filter treatment plant was modeled. The BioWin v3.1 model was successfully applied to simulate ammonia, nitrite, nitrate, TDN, DON and BDON concentrations along the treatment train.

Research paper thumbnail of Assessing tetrazolium and ATP assays for rapid in situ viability quantification of bacterial cells entrapped in hydrogel beads

Enzyme and Microbial Technology, 2010

Entrapped bacteria are used in several applications including food and beverage production, antib... more Entrapped bacteria are used in several applications including food and beverage production, antibiotic production, and wastewater treatment. To date in order to determine the viability of entrapped bacteria, they have to be de-entrapped from the matrix first. However, the cell de-entrapment procedures such as matrix dissolution by acid or heating at high temperatures, may affect the viability of the cells. In this study, the uses of two quantitative approaches for in situ viability estimation of calcium alginate and phosphorylated poly(vinyl) alcohol (PPVA) entrapped Escherichia coli were investigated. Bioreducible tetrazolium salt (XTT) and adenosine triphosphate (ATP) based assays were used to determine microbial viability without the dissolution of the matrices (spherical beads). The data from both assays showed linearity and strong correlations between the viability signals and number of beads in which each bead contained a similar number of live cells. An application of XTT assay on the PPVA entrapped bacterial beads was an exception to these results. Effects of the acid and heat dissolution de-entrapment procedures on cell viability were also evaluated by using both assays and a traditional plate count method. The heating process showed the greatest reduction in bacterial viability when compared to the other de-entrapment procedures. The ATP assay is a more sensitive and less time consuming approach for viability estimation when compared to the XTT assay and traditional plate count method. Both XTT and ATP assays have potential for use in quantifying the viability of entrapped bacteria.

Research paper thumbnail of Overlapping Photodegradable and Biodegradable Organic Nitrogen in Wastewater Effluents

Environmental Science & Technology, 2013

Photochemical degradation of dissolved organic nitrogen (DON) in final effluent of trickling filt... more Photochemical degradation of dissolved organic nitrogen (DON) in final effluent of trickling filter and activated sludge wastewater treatment plants (WWTPs) was studied. Inorganic N, mostly nitrite, was produced from the photodegradation of DON for samples from both WWTPs. Photodegradable DON (PDON), biodegradable DON (BDON), and overlapping photodegradable-biodegradable DON (OPBDON) were determined. BDON was associated with PDON as well as non-PDON. BDON and PDON concentrations in the final effluent samples were 4.71 and 4.62 mg N/L for the trickling filter plant and 3.95 and 3.73 mg N/L for the activated sludge plant, indicating that photodegradation is as important as biodegradation in the mineralization of effluent DON in receiving waters. OPBDON, which is more problematic in the water environment because it can be mineralized by light or bacteria or both, was 3.68 and 2.64 mg N/L (57% and 43% of total DON) in the final effluent samples from the trickling filter and activated sludge plants, respectively. The DON fraction that is resistant to biodegradation and photodegradation was 10% to 20% of total DON.

Research paper thumbnail of Enricher reactor – Permeable reactive biobarrier approach for removing a mixture of contaminants with substrate interactions

Bioresource Technology, 2013

First study to examine effect of absence of BTEX on the performance of biobarrier. Biobarrier los... more First study to examine effect of absence of BTEX on the performance of biobarrier. Biobarrier lost removal ability for benzene and toluene when they reappeared. Benzene biodegradation was inhibited by toluene after an absence period. Bioaugmentation from enricher reactor sped recovery of biobarrier. Toluene was an effective alternative inducer to BTEX in enricher reactor.

Research paper thumbnail of A new method to determine initial viability of entrapped cells using fluorescent nucleic acid staining

Bioresource …, 2010

Entrapped bacterial cells are widely used in several biotechnological applications. Cell entrapme... more Entrapped bacterial cells are widely used in several biotechnological applications. Cell entrapment procedures are known to affect the viability of bacterial cells. To determine the effect of entrapment procedures on viability of bacterial cells, dissolution of the entrapment matrices using chelating agents or heat is required immediately after the entrapment is completed. Chelating agents and heat applied in the matrix dissolution reduce cell viability and in turn hinder accurate quantification of viable cells. In this study, a method to determine the effect of entrapment procedure on bacterial cell viability which involves entrapping cells directly onto glass slides was developed. The developed method showed less viability reduction than the methods requiring matrix dissolution. The percentage of live cells in the culture before entrapment ranged from 54% to 74%, while the percent of live cells after entrapment determined by the developed method was 39-62%.

Research paper thumbnail of Effect of carbon source during enrichment on BTEX degradation by anaerobic mixed bacterial cultures

A comprehensive study on the effects of different carbon sources during the bacterial enrichment ... more A comprehensive study on the effects of different carbon sources during the bacterial enrichment on the removal performances of benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds when present as a mixture was conducted. Batch BTEX removal kinetic experiments were performed using cultures enriched with individual BTEX compounds or BTEX as a mixture or benzoate alone or benzoate-BTEX mixture. An integrated Monod-type non-linear model was developed and a ratio between maximum growth rate (l max ) and half saturation constant (K s ) was used to fit the non-linear model. A higher l max /K s indicates a higher affinity to degrade BTEX compounds. Complete removal of BTEX mixture was observed by all the enriched cultures; however, the removal rates for individual compounds varied. Degradation rate and the type of removal kinetics were found to be dependent on the type of carbon source during the enrichment. Cultures enriched on toluene and those enriched on BTEX mixture were found to have the greatest l max /K s and cultures enriched on benzoate had the least l max /K s . Removal performances of the cultures enriched on all different carbon sources, including the ones enriched on benzoate or benzoate-BTEX mixture were also improved during a second exposure to BTEX. A molecular analysis showed that after each exposure to the BTEX mixture, the cultures enriched on benzoate and those enriched on benzoate-BTEX mixture had increased similarities to the culture enriched on BTEX mixture.

Research paper thumbnail of A Novel Application of Enricher Reactor - Permeable Reactive Biobarrier for Removing a Mixture of Contaminants with Substrate Interactions

Proceedings of the Water Environment Federation, 2012

Research paper thumbnail of Role of Manure Application on Soil in Preventing Groundwater Contamination by <I>Cryptosporidium</I>

Proceedings of the Water Environment Federation, 2011

Research paper thumbnail of Modeling a Two-Stage Trickling Filter Wastewater Treatment Plant to Simulate the Fate of Dissolved Organic Nitrogen and Its Biodegradability

Proceedings of the Water Environment Federation, 2011

Research paper thumbnail of Urea Responsible for Aggregation in Bacterial Strains Commonly Found in Activated Sludge

Proceedings of the Water Environment Federation, 2013

Research paper thumbnail of Reintroduction of Contaminant in Groundwater Alters Bacterial Community

Proceedings of the Water Environment Federation, 2012

Research paper thumbnail of Dissolved organic nitrogen and its biodegradable portion in a water treatment plant with ozone oxidation

Water Research, 2014

Biodegradable dissolved organic nitrogen (BDON) Dissolved organic nitrogen (DON) Total dissolved ... more Biodegradable dissolved organic nitrogen (BDON) Dissolved organic nitrogen (DON) Total dissolved nitrogen (TDN)

Research paper thumbnail of Assessing tetrazolium and ATP assays for rapid in situ viability quantification of bacterial cells entrapped in hydrogel beads

Entrapped bacteria are used in several applications including food and beverage production, antib... more Entrapped bacteria are used in several applications including food and beverage production, antibiotic production, and wastewater treatment. To date in order to determine the viability of entrapped bacteria, they have to be de-entrapped from the matrix first. However, the cell de-entrapment procedures such as matrix dissolution by acid or heating at high temperatures, may affect the viability of the cells. In this study, the uses of two quantitative approaches for in situ viability estimation of calcium alginate and phosphorylated poly(vinyl) alcohol (PPVA) entrapped Escherichia coli were investigated. Bioreducible tetrazolium salt (XTT) and adenosine triphosphate (ATP) based assays were used to determine microbial viability without the dissolution of the matrices (spherical beads). The data from both assays showed linearity and strong correlations between the viability signals and number of beads in which each bead contained a similar number of live cells. An application of XTT assay on the PPVA entrapped bacterial beads was an exception to these results. Effects of the acid and heat dissolution de-entrapment procedures on cell viability were also evaluated by using both assays and a traditional plate count method. The heating process showed the greatest reduction in bacterial viability when compared to the other de-entrapment procedures. The ATP assay is a more sensitive and less time consuming approach for viability estimation when compared to the XTT assay and traditional plate count method. Both XTT and ATP assays have potential for use in quantifying the viability of entrapped bacteria.

Research paper thumbnail of A new method to determine initial viability of entrapped cells using fluorescent nucleic acid staining

Bioresource technology, 2011

Entrapped bacterial cells are widely used in several biotechnological applications. Cell entrapme... more Entrapped bacterial cells are widely used in several biotechnological applications. Cell entrapment procedures are known to affect the viability of bacterial cells. To determine the effect of entrapment procedures on viability of bacterial cells, dissolution of the entrapment matrices using chelating agents or heat is required immediately after the entrapment is completed. Chelating agents and heat applied in the matrix dissolution reduce cell viability and in turn hinder accurate quantification of viable cells. In this study, a method to determine the effect of entrapment procedure on bacterial cell viability which involves entrapping cells directly onto glass slides was developed. The developed method showed less viability reduction than the methods requiring matrix dissolution. The percentage of live cells in the culture before entrapment ranged from 54% to 74%, while the percent of live cells after entrapment determined by the developed method was 39-62%.

Research paper thumbnail of Fate of dissolved organic nitrogen in two stage trickling filter process

Water Research, 2012

Biodegradable dissolved organic nitrogen (BDON) Dissolved organic nitrogen (DON) Total dissolved ... more Biodegradable dissolved organic nitrogen (BDON) Dissolved organic nitrogen (DON) Total dissolved nitrogen (TDN) Trickling filters Wastewater BioWin modeling a b s t r a c t Dissolved organic nitrogen (DON) represents a significant portion of nitrogen in the final effluent of wastewater treatment plants (WWTPs). Biodegradable portion of DON (BDON) can support algal growth and/or consume dissolved oxygen in the receiving waters. The fate of DON and BDON has not been studied for trickling filter WWTPs. DON and BDON data were collected along the treatment train of a WWTP with a two-stage trickling filter process. DON concentrations in the influent and effluent were 27% and 14% of total dissolved nitrogen (TDN). The plant removed about 62% and 72% of the influent DON and BDON mainly by the trickling filters. The final effluent BDON values averaged 1.8 mg/L. BDON was found to be between 51% and 69% of the DON in raw wastewater and after various treatment units. The fate of DON and BDON through the two-stage trickling filter treatment plant was modeled. The BioWin v3.1 model was successfully applied to simulate ammonia, nitrite, nitrate, TDN, DON and BDON concentrations along the treatment train.

Research paper thumbnail of Assessing tetrazolium and ATP assays for rapid in situ viability quantification of bacterial cells entrapped in hydrogel beads

Enzyme and Microbial Technology, 2010

Entrapped bacteria are used in several applications including food and beverage production, antib... more Entrapped bacteria are used in several applications including food and beverage production, antibiotic production, and wastewater treatment. To date in order to determine the viability of entrapped bacteria, they have to be de-entrapped from the matrix first. However, the cell de-entrapment procedures such as matrix dissolution by acid or heating at high temperatures, may affect the viability of the cells. In this study, the uses of two quantitative approaches for in situ viability estimation of calcium alginate and phosphorylated poly(vinyl) alcohol (PPVA) entrapped Escherichia coli were investigated. Bioreducible tetrazolium salt (XTT) and adenosine triphosphate (ATP) based assays were used to determine microbial viability without the dissolution of the matrices (spherical beads). The data from both assays showed linearity and strong correlations between the viability signals and number of beads in which each bead contained a similar number of live cells. An application of XTT assay on the PPVA entrapped bacterial beads was an exception to these results. Effects of the acid and heat dissolution de-entrapment procedures on cell viability were also evaluated by using both assays and a traditional plate count method. The heating process showed the greatest reduction in bacterial viability when compared to the other de-entrapment procedures. The ATP assay is a more sensitive and less time consuming approach for viability estimation when compared to the XTT assay and traditional plate count method. Both XTT and ATP assays have potential for use in quantifying the viability of entrapped bacteria.

Research paper thumbnail of Overlapping Photodegradable and Biodegradable Organic Nitrogen in Wastewater Effluents

Environmental Science & Technology, 2013

Photochemical degradation of dissolved organic nitrogen (DON) in final effluent of trickling filt... more Photochemical degradation of dissolved organic nitrogen (DON) in final effluent of trickling filter and activated sludge wastewater treatment plants (WWTPs) was studied. Inorganic N, mostly nitrite, was produced from the photodegradation of DON for samples from both WWTPs. Photodegradable DON (PDON), biodegradable DON (BDON), and overlapping photodegradable-biodegradable DON (OPBDON) were determined. BDON was associated with PDON as well as non-PDON. BDON and PDON concentrations in the final effluent samples were 4.71 and 4.62 mg N/L for the trickling filter plant and 3.95 and 3.73 mg N/L for the activated sludge plant, indicating that photodegradation is as important as biodegradation in the mineralization of effluent DON in receiving waters. OPBDON, which is more problematic in the water environment because it can be mineralized by light or bacteria or both, was 3.68 and 2.64 mg N/L (57% and 43% of total DON) in the final effluent samples from the trickling filter and activated sludge plants, respectively. The DON fraction that is resistant to biodegradation and photodegradation was 10% to 20% of total DON.

Research paper thumbnail of Enricher reactor – Permeable reactive biobarrier approach for removing a mixture of contaminants with substrate interactions

Bioresource Technology, 2013

First study to examine effect of absence of BTEX on the performance of biobarrier. Biobarrier los... more First study to examine effect of absence of BTEX on the performance of biobarrier. Biobarrier lost removal ability for benzene and toluene when they reappeared. Benzene biodegradation was inhibited by toluene after an absence period. Bioaugmentation from enricher reactor sped recovery of biobarrier. Toluene was an effective alternative inducer to BTEX in enricher reactor.

Research paper thumbnail of A new method to determine initial viability of entrapped cells using fluorescent nucleic acid staining

Bioresource …, 2010

Entrapped bacterial cells are widely used in several biotechnological applications. Cell entrapme... more Entrapped bacterial cells are widely used in several biotechnological applications. Cell entrapment procedures are known to affect the viability of bacterial cells. To determine the effect of entrapment procedures on viability of bacterial cells, dissolution of the entrapment matrices using chelating agents or heat is required immediately after the entrapment is completed. Chelating agents and heat applied in the matrix dissolution reduce cell viability and in turn hinder accurate quantification of viable cells. In this study, a method to determine the effect of entrapment procedure on bacterial cell viability which involves entrapping cells directly onto glass slides was developed. The developed method showed less viability reduction than the methods requiring matrix dissolution. The percentage of live cells in the culture before entrapment ranged from 54% to 74%, while the percent of live cells after entrapment determined by the developed method was 39-62%.

Research paper thumbnail of Effect of carbon source during enrichment on BTEX degradation by anaerobic mixed bacterial cultures

A comprehensive study on the effects of different carbon sources during the bacterial enrichment ... more A comprehensive study on the effects of different carbon sources during the bacterial enrichment on the removal performances of benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds when present as a mixture was conducted. Batch BTEX removal kinetic experiments were performed using cultures enriched with individual BTEX compounds or BTEX as a mixture or benzoate alone or benzoate-BTEX mixture. An integrated Monod-type non-linear model was developed and a ratio between maximum growth rate (l max ) and half saturation constant (K s ) was used to fit the non-linear model. A higher l max /K s indicates a higher affinity to degrade BTEX compounds. Complete removal of BTEX mixture was observed by all the enriched cultures; however, the removal rates for individual compounds varied. Degradation rate and the type of removal kinetics were found to be dependent on the type of carbon source during the enrichment. Cultures enriched on toluene and those enriched on BTEX mixture were found to have the greatest l max /K s and cultures enriched on benzoate had the least l max /K s . Removal performances of the cultures enriched on all different carbon sources, including the ones enriched on benzoate or benzoate-BTEX mixture were also improved during a second exposure to BTEX. A molecular analysis showed that after each exposure to the BTEX mixture, the cultures enriched on benzoate and those enriched on benzoate-BTEX mixture had increased similarities to the culture enriched on BTEX mixture.