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Dr. Roya Pishgar
Department of Civil Engineering, University of Calgary, T2N 1N4 Calgary, AB, Canada

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Research Keywords & Expertise

0 Nitrification
0 biological wastewater treatment
0 Denitrification
0 Water and nutrient (ammonium and phosphate) recovery from wastewater
0 Enhanced biological phosphate removal from wastewater (EBPR)

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Aerobic granulation
Nitrification
Denitrification
Enhanced biological phosphate removal from wastewater (EBPR)

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Journal article
Published: 22 September 2020 in Science of The Total Environment
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This study aimed to investigate the efficacy of private septic systems retrofitted into aerobic bioreactors with ‘SludgeHammer’ technology. In addition, the study attempted to characterize the strength of domestic wastewater released from ‘green’ households practicing water conservation strategies. Ten retrofitted onsite septic systems were studied in the Edmonton area, Alberta (AB) Canada during winter. These systems could remove BOD5 and TSS by 92 ± 5 and 92 ± 6% respectively which, according to Albertan regulatory standards, were characteristic removal efficiencies of the secondary treatment in the subsequent drain field. These removal efficiencies were remarkable given the strength of the influent wastewater. The raw wastewater carried significantly high pollutant concentrations (1171 ± 372 mg BOD5/L, 1653 ± 1174 mg TSS/L, 99 ± 19 mg NH4+-N/L, 100 ± 56 mg TN/L, and 39 ± 28 mg PO43--P/L), characterizing it as high-strength domestic wastewater. Mixing provided by the aerator could only suspend 1/34th (3% m/m) of the solids in the bioreactor and consequently released significantly low solid concentrations (195 ± 206 mg TSS/L) into the final treatment component. As such, this technology did not impair the natural function of septic tanks or did not create any unintended excessive solids loading on drain field as a consequence of the added mixing energies provided by the active aeration. Nitrogen balance suggested the possibility of simultaneous nitrification and denitrification (SND) in the aerobic bioreactors. In some cases, PO43--P removal efficiency was as high as that in enhanced biological phosphate removal (EBPR) process (81 – 97%). Phosphorus balance estimated that non-assimilative pathways (i.e., EBPR + biologically induced phosphate precipitation (BIPP)) contributed 50 – 99% to overall phosphorus removal in the system. Long HRTs, high influent BOD5 and anaerobic/aerobic zoning in the bioreactor most likely provided favorable conditions for SND and high phosphorus removal efficiencies in the retrofitted OWTS.

ACS Style

Roya Pishgar; Dean Morin; Shane J. Young; Jon Schwartz; Angus Chu. Characterization of domestic wastewater released from ‘green’ households and field study of the performance of onsite septic tanks retrofitted into aerobic bioreactors in cold climate. Science of The Total Environment 2020, 755, 142446 .

AMA Style

Roya Pishgar, Dean Morin, Shane J. Young, Jon Schwartz, Angus Chu. Characterization of domestic wastewater released from ‘green’ households and field study of the performance of onsite septic tanks retrofitted into aerobic bioreactors in cold climate. Science of The Total Environment. 2020; 755 ():142446.

Chicago/Turabian Style

Roya Pishgar; Dean Morin; Shane J. Young; Jon Schwartz; Angus Chu. 2020. "Characterization of domestic wastewater released from ‘green’ households and field study of the performance of onsite septic tanks retrofitted into aerobic bioreactors in cold climate." Science of The Total Environment 755, no. : 142446.

Article
Published: 13 March 2020 in Applied Biochemistry and Biotechnology
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This study investigated the treatment performance of lagoon-based municipal wastewater treatment plants (LWWTPs) inoculated by proprietary biogranules. Augmentation process included enhancing the microbial community of lagoon basins by weekly addition of biogranules over the treatment seasons (summer and fall). Effluent qualities before and after the augmentation process were compared, and the results were reported as "enhanced treatment efficiencies, EE". Very low concentrations of 5-day biochemical oxygen demand (BOD5), total nitrogen (TN), total Kjeldahl nitrogen (TKN), ammonium nitrogen (N-NH4), and total phosphorus (TP) were detected at discharge points after the augmentation process, which corresponded to enhanced treatment efficiencies of 86, 74, 72, 92.7, and 71%, respectively. Significant reduction in total coliform and E. coli concentrations in the effluents (91 and 98%, respectively) demonstrated the capability of granule-based lagoons in destroying pathogens. Adding biogranules to lagoons was an efficient remedy for excess sludge buildup in short and long runs. Hence, inoculating lagoon plants using biogranules was suggested as an effective technique to augment rural wastewater treatment facilities.

ACS Style

Roya Pishgar; Jonathan Lee; John Albino Dominic; Sadegh Hosseini; Joo Hwa Tay; Angus Chu. Augmentation of Biogranules for Enhanced Performance of Full-Scale Lagoon-Based Municipal Wastewater Treatment Plants. Applied Biochemistry and Biotechnology 2020, 191, 426 -443.

AMA Style

Roya Pishgar, Jonathan Lee, John Albino Dominic, Sadegh Hosseini, Joo Hwa Tay, Angus Chu. Augmentation of Biogranules for Enhanced Performance of Full-Scale Lagoon-Based Municipal Wastewater Treatment Plants. Applied Biochemistry and Biotechnology. 2020; 191 (1):426-443.

Chicago/Turabian Style

Roya Pishgar; Jonathan Lee; John Albino Dominic; Sadegh Hosseini; Joo Hwa Tay; Angus Chu. 2020. "Augmentation of Biogranules for Enhanced Performance of Full-Scale Lagoon-Based Municipal Wastewater Treatment Plants." Applied Biochemistry and Biotechnology 191, no. 1: 426-443.

Journal article
Published: 01 November 2019 in Science of The Total Environment
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This study investigated the effect of hydraulic retention time (HRT) and chemical oxygen demand (COD) concentration on membrane fouling in aerobic granular membrane bioreactor (AGMBR) in a systematic approach. Changes in HRT (7, 10, and 15 h) and COD (500, 1000 and 1500 mg/L) were applied in five operational phases, to determine the most significant parameters to control membrane fouling for enhanced AGMBR performance. Membrane permeability loss was dramatically intensified with increase in HRT from 7.5 to 15 h and COD from 500 to 1000 mg/L. The highest polysaccharide content of loosely bound EPS (0.41 mg PS/mg VSS) and soluble microbial products (SMPs) (27 mg PS/L) occurred alongside poor AGMBR performance. Variations in membrane fouling were accompanied with considerable changes in Flavobacterium, Thauera and Paracoccus populations. Analysis of variance (ANOVA) demonstrated that HRT and interaction between HRT and COD were the most significant parameters in controlling membrane fouling.

ACS Style

Arezoo Tavana; Roya Pishgar; Joo Hwa Tay. Impact of hydraulic retention time and organic matter concentration on side-stream aerobic granular membrane bioreactor. Science of The Total Environment 2019, 693, 133525 .

AMA Style

Arezoo Tavana, Roya Pishgar, Joo Hwa Tay. Impact of hydraulic retention time and organic matter concentration on side-stream aerobic granular membrane bioreactor. Science of The Total Environment. 2019; 693 ():133525.

Chicago/Turabian Style

Arezoo Tavana; Roya Pishgar; Joo Hwa Tay. 2019. "Impact of hydraulic retention time and organic matter concentration on side-stream aerobic granular membrane bioreactor." Science of The Total Environment 693, no. : 133525.

Journal article
Published: 03 October 2019 in Water Research
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This study investigated nutrient removal characteristics and the related pathways in aerobic granular reactors using three pilot-scale granular sequencing batch reactors (GSBRs) treating wastewaters of diverse carbon and nutrient strength. The GSBRs were operated with alternating (AN/O/AX/O_SBR and AN/O_SBR) and purely-aerobic (O_SBR) operation modes. Mineral-rich aerobic granules with hydroxyapatite (HAp) core were cultivated in all the three GSBRs. The highest nitrogen removal efficiency (75%) was achieved in AN/O/AX/O_SBR and O_SBR and the lowest (22%) in AN/O_SBR, establishing a quasi-linear relationship with organic loading rate (OLR). Phosphorus removal efficiencies of 55–63% were achieved in the GSBRs despite different influent PO4–P concentrations. Heterotrophic nitrification and biologically-induced phosphate precipitation (BIPP) became the dominant nutrient depletion pathways, contributing 61–84% and 39–96% to overall ammonium nitrogen and phosphorus removal, respectively. A direct relation was noted between heterotrophic nitrification efficiency (η Heterotrophic nitrification) and nutrient availability, as nitrification efficiencies of 18 and 64% were observed for COD:Ninf of 5 and 20, respectively. Whereas, BIPP efficiency (η BIPP) established inverse relation with (COD:P)inf and (Ca:P)inf and direct relation with phosphorus concentration beyond microbial growth requirement. Core heterotrophic nitrifiers and bio-calcifying species were identified as {Thauera and Flavobacterium} and {Flavobacterium, Acinetobacter, Pseudomonas, and Corynebacterium}, respectively. Ca–P crystallization was proposed to be via phosphate precipitation on calcite surfaces. Granulation mechanism was proposed as crystallization on bio-aggregates’ periphery and then crystal growth toward the core.

ACS Style

Roya Pishgar; John Albino Dominic; Joo Hwa Tay; Angus Chu. Pilot-scale investigation on nutrient removal characteristics of mineral-rich aerobic granular sludge: Identification of uncommon mechanisms. Water Research 2019, 168, 115151 .

AMA Style

Roya Pishgar, John Albino Dominic, Joo Hwa Tay, Angus Chu. Pilot-scale investigation on nutrient removal characteristics of mineral-rich aerobic granular sludge: Identification of uncommon mechanisms. Water Research. 2019; 168 ():115151.

Chicago/Turabian Style

Roya Pishgar; John Albino Dominic; Joo Hwa Tay; Angus Chu. 2019. "Pilot-scale investigation on nutrient removal characteristics of mineral-rich aerobic granular sludge: Identification of uncommon mechanisms." Water Research 168, no. : 115151.

Journal article
Published: 13 May 2019 in Water Research
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This study attempted to investigate the influence of operation mode and wastewater strength on startup period, aerobic granular sludge (AGS) characteristics, and system effluent quality at pilot scale. Granulation was monitored in three pilot-scale granular sequencing batch reactors (GSBRs). Comparative evaluation of AN/O/AX/O_SBR and O_SBR, fed with wastewater of the same composition but run with completely different SBR reaction phase arrangements (alternating vs. purely aerobic), revealed the effect of SBR operation mode. Comparative study of GSBRs operated with alternating SBR reaction phases (AN/O/AX/O_SBR and AN/O_SBR) and fed with wastewater of different strength (high-vs. medium-strength) determined the effect of wastewater composition. Granulation time and granule size were regulated by wastewater strength and the resulting organic and sludge loading conditions. Whereas, AGS morphology, granule structure, and floccular proportion of AGS were attributed to SBR operation mode. Effluent clarity in terms of suspended solid concentration depended on wastewater strength. Subtle but distinct microbial selection strategies were in effect during granulation which were also imposed by wastewater strength. Due to strong correlation between effluent and AGS microbial structures, demonstrated by biodiversity analysis, differences in the microbial composition of effluent biomass and washout patterns of the GSBRs could be explained by wastewater strength as well. Limited nutrient removal efficiencies, restricted by organic matter concentration, could be due to involvement of unorthodox nutrient removal pathways which warrants further investigation.

ACS Style

Roya Pishgar; John Albino Dominic; Zhiya Sheng; Joo Hwa Tay. Influence of operation mode and wastewater strength on aerobic granulation at pilot scale: Startup period, granular sludge characteristics, and effluent quality. Water Research 2019, 160, 81 -96.

AMA Style

Roya Pishgar, John Albino Dominic, Zhiya Sheng, Joo Hwa Tay. Influence of operation mode and wastewater strength on aerobic granulation at pilot scale: Startup period, granular sludge characteristics, and effluent quality. Water Research. 2019; 160 ():81-96.

Chicago/Turabian Style

Roya Pishgar; John Albino Dominic; Zhiya Sheng; Joo Hwa Tay. 2019. "Influence of operation mode and wastewater strength on aerobic granulation at pilot scale: Startup period, granular sludge characteristics, and effluent quality." Water Research 160, no. : 81-96.

Journal article
Published: 13 February 2019 in Bioresource Technology
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This study investigated functional dynamics of microbial community in response to different selection pressures, with a focus on denitrification. Suspended-biomass experiments demonstrated limited aerobic and relatively high anoxic nitrate and nitrite reduction capabilities; the highest NO2-N and NO3-N removal rates were 1.3 ± 0.1 and 0.74 ± 0.01 in aerobic and 1.4 ± 0.05 and 3.4 ± 0.1 mg/L.h in anoxic media, respectively. Key potential denitrifiers were identified as: (i) complete aerobic denitrifiers: Dokdonella, Flavobacterium, and Ca. Accumulibacter; (ii) complete anoxic denitrifiers: Acinetobacter, Pseudomonas, Arcobacter, and Comamonas; (iii) incomplete nitrite denitrifier: Diaphorobacter (aerobic/anoxic), (iv): incomplete nitrate denitrifiers: Thauera (aerobic/anoxic) and Zoogloea (strictly-aerobic). Granular biomass removed 72 mg/L NH4-N with no NOx− accumulation. Heterotrophic nitrification and aerobic denitrification were proposed as the principal nitrogen removal pathway in granular reactors, potentially performed by two key organisms Thuaera and Flavobacterium. Biodiversity analysis suggested that the selection pressure of nourishment condition was the decisive factor for microbial selection and nitrogen removal mechanism.

ACS Style

Roya Pishgar; John Albino Dominic; Zhiya Sheng; Joo Hwa Tay. Denitrification performance and microbial versatility in response to different selection pressures. Bioresource Technology 2019, 281, 72 -83.

AMA Style

Roya Pishgar, John Albino Dominic, Zhiya Sheng, Joo Hwa Tay. Denitrification performance and microbial versatility in response to different selection pressures. Bioresource Technology. 2019; 281 ():72-83.

Chicago/Turabian Style

Roya Pishgar; John Albino Dominic; Zhiya Sheng; Joo Hwa Tay. 2019. "Denitrification performance and microbial versatility in response to different selection pressures." Bioresource Technology 281, no. : 72-83.

Journal article
Published: 04 October 2018 in Journal of Environmental Chemical Engineering
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This study investigates the influence of aeration pattern and gas bubble distribution on aerobic granulation in pilot bubble columns and advances the understanding on crucial factors to be considered during scale-up. Experiments were conducted in a pilot scale bubble column of 22-L capacity. A laboratory-scale bubble column of 5-L capacity, which could achieve granulation in a short time, was used as the control reactor. The pilot reactor was operated with optimal operational conditions evaluated for the control reactor, but the granulation was initially inhibited; improper aeration pattern was found as the most significant factor in precluding granulation. Aerobic granulation in the pilot-scale reactor was achieved upon modifying the gas distributor design. The effect of gas distributor characteristics (i.e., pore size, free area ϕ, and relative surface area of the gas distributor to the cross-section of the column R) on the aeration pattern has been thoroughly discussed. A scale-up ratio (S) for the gas distributor has been proposed. Reliability of aeration intensity in terms of superficial air velocity usg, which has been commonly used as an indicator of prevailing hydrodynamics and shear stress in lab-scale granular bubble columns, has been discussed; it was demonstrated that usg could not realistically represent the aforementioned conditions in a larger module. Instead, it was suggested that a greater attention should be paid to bubble size and bubble ascending velocity and thus to the subsequent aeration pattern. Gas holdup has been eventually introduced as a crucial and easy-to-measure controlling factor for the scale-up of granular reactors.

ACS Style

R. Pishgar; A. Kanda; G.R. Gress; H. Gong; J.A. Dominic; J.H. Tay. Effect of aeration pattern and gas distribution during scale-up of bubble column reactor for aerobic granulation. Journal of Environmental Chemical Engineering 2018, 6, 6431 -6443.

AMA Style

R. Pishgar, A. Kanda, G.R. Gress, H. Gong, J.A. Dominic, J.H. Tay. Effect of aeration pattern and gas distribution during scale-up of bubble column reactor for aerobic granulation. Journal of Environmental Chemical Engineering. 2018; 6 (5):6431-6443.

Chicago/Turabian Style

R. Pishgar; A. Kanda; G.R. Gress; H. Gong; J.A. Dominic; J.H. Tay. 2018. "Effect of aeration pattern and gas distribution during scale-up of bubble column reactor for aerobic granulation." Journal of Environmental Chemical Engineering 6, no. 5: 6431-6443.

Original articles
Published: 27 April 2018 in Environmental Technology
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Aerobic granulation is a recent technology with high level of complexity and sensitivity to environmental and operational conditions. Artificial neural networks (ANNs), computational tools capable of describing complex non-linear systems, are the best fit to simulate aerobic granular bioreactors. In this study, two feedforward backpropagation ANN models were developed to predict chemical oxygen demand (Model I) and total nitrogen removal efficiencies (Model II) of aerobic granulation technology under steady-state condition. Fundamentals of ANN models and the steps to create them were briefly reviewed. The models were respectively fed with 205 and 136 data points collected from laboratory-, pilot-, and full-scale studies on aerobic granulation technology reported in the literature. Initially, 60%, 20%, and 20%, and 80%, 10%, and 10% of the points in the corresponding datasets were randomly chosen and used for training, testing, and validation of Model I, and Model II, respectively. Overall coefficient of determination (R2) value and mean squared error (MSE) of the two models were initially 0.49 and 15.5, and 0.37 and 408, respectively. To improve the model performance, two data division methods were used. While one method is generic and potentially applicable to other fields, the other can only be applied to modelling the performance of aerobic granular reactors. R2 value and MSE were improved to 0.90 and 2.54, and 0.81 and 121.56, respectively, after applying the new data division methods. The results demonstrated that ANN-based models were capable simulation approach to predict a complicated process like aerobic granulation.

ACS Style

H. Gong; R. Pishgar; J. H. Tay. Artificial neural network modelling for organic and total nitrogen removal of aerobic granulation under steady-state condition. Environmental Technology 2018, 40, 3124 -3139.

AMA Style

H. Gong, R. Pishgar, J. H. Tay. Artificial neural network modelling for organic and total nitrogen removal of aerobic granulation under steady-state condition. Environmental Technology. 2018; 40 (24):3124-3139.

Chicago/Turabian Style

H. Gong; R. Pishgar; J. H. Tay. 2018. "Artificial neural network modelling for organic and total nitrogen removal of aerobic granulation under steady-state condition." Environmental Technology 40, no. 24: 3124-3139.

Conference paper
Published: 05 May 2017 in Proceedings of EECE 2020
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Numerous laboratory-scale studies confirmed the effectiveness of aerobic granulation technology for diverse treatment purposes. However, few pilot scale investigations have been conducted so far, and these studies revealed that a large-scale module could frustrate the microbial granulation process. In this study, the effect of scale-up on granule formation was investigated. Upflow air velocity, a function of the aeration rate, is normally deemed to be the main source of hydrodynamic shear force in bubble column reactors. Shear force is known as one of the important inducers of aerobic granulation. Superficial upflow air velocity (SUAV) is defined as aeration rate per cross-section area of the reactor. However, the findings of this study proved that maintaining SUAV was not sufficient for successful granulation. In addition, the parameter SUAV could not well represent the hydrodynamics of bubble column reactors, especially during the scale-up procedure. This study proved that air bubble distribution was of greater importance, as opposed to the effect of aeration rate. Mean distance between bubbles should be maintained constant regardless of the size of reactor. This provided similar shearing activity in different reactors with different scales, which appeared to be the critical requirement for successful granulation process in a larger module. To ensure similar bubble distances in bioreactors of different sizes, diffusers with the same porosity should be used, and their surface areas and the aeration rate should be increased by the scale-up ratio. Air bubble distribution dictated the gas holdup which was eventually determined to be the crucial factor for the scale-up of aerobic granular bubble column reactors.

ACS Style

R. Pishgar; A. Kanda; G. R. Gress; H. Gong; J. H. Tay. Startup of Aerobic Granulation Technology: Troubleshooting Scale-up Issue. Proceedings of EECE 2020 2017, 691 -700.

AMA Style

R. Pishgar, A. Kanda, G. R. Gress, H. Gong, J. H. Tay. Startup of Aerobic Granulation Technology: Troubleshooting Scale-up Issue. Proceedings of EECE 2020. 2017; ():691-700.

Chicago/Turabian Style

R. Pishgar; A. Kanda; G. R. Gress; H. Gong; J. H. Tay. 2017. "Startup of Aerobic Granulation Technology: Troubleshooting Scale-up Issue." Proceedings of EECE 2020 , no. : 691-700.

Article
Published: 24 February 2017 in Applied Biochemistry and Biotechnology
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This study investigated the feasibility of using freeze-dried biogranules in lagoon basins. The effect of different operational conditions on treatment performance and detention time of granule-based lagoons was examined in a series of laboratory-scale batch studies. Optimal granule dosage was 0.1 g/L under anaerobic condition, resulting in 80–94% removal of 1000 mg/L chemical oxygen demand (COD) in 7–10 days. Under aerobic condition, granule dosage of 0.2 g/L achieved the best result for identical COD concentration. However, adequate amount of nutrients (optimal COD/N/P ratio of 100/13/0.8) should be supplied to encourage the growth of aerobic species. At optimal COD/N/P ratio, aerobic treatment interval significantly reduced to 2–3 days with corresponding COD removal efficiency of 88–92%. Inhibition of high concentrations of COD (5000 mg/L) and ammonia (480 mg/L NH4-N) was observed on microbial activity and treatment capacity of the biogranules. Mixing was a crucial measure to overcome mass transfer limitation. Onetime inoculation of lagoon with fresh granules was the best approach to achieve a satisfactory treatment efficiency. This study suggested that utilization of the biogranules is a feasible and sustainable technique for augmenting lagoon plants in terms of improved effluent quality and reduced retention time. ᅟ

ACS Style

Roya Pishgar; Rania Ahmed Hamza; Joo Hwa Tay. Augmenting Lagoon Process Using Reactivated Freeze-dried Biogranules. Applied Biochemistry and Biotechnology 2017, 183, 137 -154.

AMA Style

Roya Pishgar, Rania Ahmed Hamza, Joo Hwa Tay. Augmenting Lagoon Process Using Reactivated Freeze-dried Biogranules. Applied Biochemistry and Biotechnology. 2017; 183 (1):137-154.

Chicago/Turabian Style

Roya Pishgar; Rania Ahmed Hamza; Joo Hwa Tay. 2017. "Augmenting Lagoon Process Using Reactivated Freeze-dried Biogranules." Applied Biochemistry and Biotechnology 183, no. 1: 137-154.