Zhi-rong Hu - Academia.edu (original) (raw)

Papers by Zhi-rong Hu

Proceedings of the Water Environment Federation, 2008

ABSTRACT

Reviews in Chemical Engineering, 2019

With the rapid growth of economics and nanotechnology, a significant portion of the anthropogenic... more With the rapid growth of economics and nanotechnology, a significant portion of the anthropogenic emissions of heavy metals and nanoparticles (NPs) enters wastewater streams and discharges to wastewater treatment plants, thereby potentially posing a risk to the bacteria that facilitate the successful operation of the enhanced biological phosphorus (P) removal (EBPR) process. Although some efforts have been made to obtain detailed insights into the effects of heavy metals and metal (oxide) nanoparticles [Me(O)NPs], many unanswered questions remain. One question is whether the toxicity of Me(O)NPs originates from the released metal ions. This review aims to holistically evaluate the effects of heavy metals and Me(O)NPs. The interactions among extracellular polymeric substances, P, and heavy metals [Me(O)NPs] are presented and discussed for the first time. The potential mechanisms of the toxicity of heavy metals [Me(O)NPs] are summarized. Additionally, mathematical models of the toxici...

Bioresource Technology, 2016

h i g h l i g h t s P-removal efficiency decreased to 34.6% under the effect of ERY (10 mg/L). P-... more h i g h l i g h t s P-removal efficiency decreased to 34.6% under the effect of ERY (10 mg/L). P-removal efficiency decreased to 0.0% under the effect of OTC (10 mg/L). Aerobic stage in EBPR system was more seriously inhibited than anaerobic stage. OTC showed more serious inhibitory effect on microorganism's oxygen utilization. Neither synergistic effect nor antagonistic effect was detected between ERY and OTC.

Process Biochemistry, 2014

Enhanced biological phosphorus removal (EBPR) technology has been widely considered as a key stra... more Enhanced biological phosphorus removal (EBPR) technology has been widely considered as a key strategy in preventing eutrophication and recognized as the advancing front of research in wastewater treatment. The key to keep its high efficiency in biological phosphorus removal is to optimize the operation and management of the system. Previous research in this field has undoubtedly improved understanding of the factors hindered overall efficiency of EBPR. However, it is obvious that much remains to be learnt. This paper attempts to review the fundamental understanding in factors inhibiting the stability and reliability of the EBPR systems in the state-of-the-art research. In view of modeling the EBPR systems, an appropriate extension of the current mechanistic models with these inhibitory factors is recommended in order to better simulate and predict the behavior of full-scale and lab-scale EBPR plants. From the perspectives of the further mechanistic and multi-factors study, the direction of denitrifying dephosphatation and granules/biofilms are also discussed. This comprehensive overview will not only help us to understand the overall mechanism of the EBPR process, but also benefit the researchers and engineers to consider all the possible factors affecting the process in the urban sewage treatment plants.

Over the past decade, the concept of anaerobic processes for the treatment of low temperature dom... more Over the past decade, the concept of anaerobic processes for the treatment of low temperature domestic wastewater has been introduced. This paper uses a developed wastewater flowsheet model and experimental data from several pilot scale studies to establish the impact of integrating anaerobic process into the wastewater flowsheet. The results demonstrate that, by integrating an expanded granular sludge blanket reactor to treat settled wastewater upstream of the activated sludge process, an immediate reduction in imported electricity of 62.5% may be achieved for a treated flow of c. 10,000 m3 d−1. This proposed modification to the flowsheet offers potential synergies with novel unit processes including physico-chemical ammonia removal and dissolved methane recovery. Incorporating either of these unit operations can potentially further improve the flowsheet net energy balance to between +0.037 and +0.078 kWh m−3 of produced water. The impact of these secondary unit operations is significant as it is this contribution to the net energy balance that facilitates the shift from energy negative to energy positive wastewater treatment.

Proceedings of the Water Environment Federation, 2006

Transient or intermittent releases of specific volatile or semi-volatile organic compounds are no... more Transient or intermittent releases of specific volatile or semi-volatile organic compounds are not managed well by existing predictive fate models such as TOXCHEM+ or Water9 because they are based on steady-state conditions. In this paper, two scenarios for treatment of transient organic compound concentrations are studied using dynamic simulation: 1) Remedial actions (such as nutrient addition biodegradation, and use of off-line storage with slow return pumping to treatment) are compared to passive acceptance of the release in treatment. 2) For covered processes, strategies for managing headspace concentrations which may approach lower explosive limits are examined. Certain remedial strategies prove more effective in minimizing air emissions and effluent releases than others, demonstrating the benefits of the dynamic modeling approach.

Proceedings of the Water Environment Federation, 2006

In this paper the advantages and disadvantages of denitrifying PAOs in conventional BNRAS and ext... more In this paper the advantages and disadvantages of denitrifying PAOs in conventional BNRAS and external nitrification BNRAS (ENBNRAS) systems are evaluated, with experimental data exhibiting a range of anoxic P uptake from low (<10%) to very high (>60%). The results indicate that the specific denitrification rate of the PAOs on internally stored PHB COD is about 1/5th of that of the OHOs on SBCOD, and the PAOs contribute little (maximum 20%) to the denitrification in BNRAS systems even when the anoxic P uptake is high (60 % of the total P uptake). Considering the unpredictable nature of anoxic P uptake and the reduction in BEPR it causes compared with aerobic P uptake BEPR, it is concluded that anoxic P uptake does not add a significant advantage to the BNR system.

Proceedings of the Water Environment Federation, 2006

Proceedings of the Water Environment Federation, 2006

ABSTRACT Transient or intermittent releases of specific volatile or semi-volatile organic compoun... more ABSTRACT Transient or intermittent releases of specific volatile or semi-volatile organic compounds are not managed well by existing predictive fate models such as TOXCHEM+ or Water9 because they are based on steady-state conditions. In this paper, two scenarios for treatment of transient organic compound concentrations are studied using dynamic simulation: Remedial actions (such as nutrient addition biodegradation, and use of off-line storage with slow return pumping to treatment) are compared to passive acceptance of the release in treatment. For covered processes, strategies for managing headspace concentrations which may approach lower explosive limits are examined. Certain remedial strategies prove more effective in minimizing air emissions and effluent releases than others, demonstrating the benefits of the dynamic modeling approach.

Water Science & Technology

A biological nutrient removal (BNR) activated sludge (AS) scheme incorporating external nitrifica... more A biological nutrient removal (BNR) activated sludge (AS) scheme incorporating external nitrification in a fixed media system is evaluated. A laboratory scale investigation of the scheme indicates that it holds considerable potential for BNRAS system intensification through major reduction in sludge age and oxygen demand and significant improvement in sludge settleability. Because the BNRAS system is not required to nitrify, its anoxic mass fraction can be considerably enlarged at the expense of the aerobic mass fraction creating conditions that (i) allow it to achieve high N removals with domestic wastewaters with high TKN/COD ratios and (ii) promote anoxic P uptake polyphosphate accumulating organisms (PAO) to develop in the system. From this, and earlier investigations with conventional BNR systems, it appears that anoxic P uptake biological excess P removal (BEPR) is only about brds of aerobic P uptake BEPR. Inclusion of anoxic P uptake PAOs in, and exclusion of nitrifiers from, the BNRAS system are not essential for the scheme. However, conditions that promote aerobic P uptake to maximize BEPR, are also conducive to nitrifier growth, which, if supported in the BNRAS system, would require virtual complete nitrification in the fixed media system to avoid nitrate interference with BEPR. Before the scheme can be implemented at large scale, an engineering and economic evaluation is required to quantify its potential benefits and savings.

Acta Biotechnologica, 2003

The research was aimed at developing a technology to combine the production of useful microfungi ... more The research was aimed at developing a technology to combine the production of useful microfungi with the treatment of wastewater from food processing. A recycle bioreactor equipped with a microscreen was developed as a wastewater treatment system on a laboratory scale to contain a Rhizopus culture and maintain its dominance under non-aseptic conditions. Competitive growth of bacteria was observed, but this was minimised by manipulation of the solids retention time and the hydraulic retention time. Removal of about 90% of the waste organic material (as BOD) from the wastewater was achieved simultaneously. Since essentially all fungi are retained behind the 100 µm aperture screen, the solids retention time could be controlled by the rate of harvesting. The hydraulic retention time was employed to control the bacterial growth as the bacteria were washed through the screen at a short HRT. A steady state model was developed to determine these two parameters. This model predicts the effluent quality. Experimental work is still needed to determine the growth characteristics of the selected fungal species under optimum conditions (pH and temperature).

Proceedings of the Water Environment Federation, 2002

Abstract A selected microfungal species was cultivated on corn processing wastewater in batch cul... more Abstract A selected microfungal species was cultivated on corn processing wastewater in batch culture and in a continuous system with microscreen separation. Results have demonstrated the feasibility of growing the selected fungal species on this wastewater. The COD ...

Proceedings of the Water Environment Federation, 2006

... The original cycle settings are shown in the center of Table 3. The design objectives for eff... more ... The original cycle settings are shown in the center of Table 3. The design objectives for effluent and maximum MLSS in the reactor for the SBR plant are shown in Table 4. Table 3: Cycle Settings for the Designed and Optimal SBR Process SBR Phases Phase length (minutes ...

Water science and technology : a journal of the International Association on Water Pollution Research, 2002

In this paper the advantages and disadvantages of denitrifying PAOs (polyphosphate accumulating o... more In this paper the advantages and disadvantages of denitrifying PAOs (polyphosphate accumulating organisms) in conventional BNRAS (biological nutrient removal activated sludge) and external nitrification BNRAS (ENBNRAS) systems are evaluated, with experimental data exhibiting a range of anoxic P uptake from low (<10%) to very high (>60%). The results indicate that the specific denitrification rate of the PAOs on internally stored PHB COD is about 1/5th of that of the "ordinary" heterotrophic organisms on SBCOD, and the PAOs contribute little (maximum 20%) to the denitrification in BNRAS systems even when the anoxic P uptake is high (60% of the total P uptake). Considering the unpredictable nature of anoxic P uptake and the reduction in BEPR it causes compared with aerobic P uptake BEPR, it is concluded that anoxic P uptake does not add a significant advantage to the BNR system.

Bioresource technology, Jan 19, 2015

The present study investigated the influences of three metabolic uncouplers (pCP, oCP and oNP) on... more The present study investigated the influences of three metabolic uncouplers (pCP, oCP and oNP) on excess activated sludge reduction and microbial products of extracellular polymeric substances (EPS) and intracellular storage product (polyhydroxybutyrate, PHB) in short-term tests. Results showed sludge was reduced 58.2%, 59.8% and 80.8%, respectively, at pCP, oCP and oNP concentrations of 20mg/L. The dosage of three uncouplers had no obviously influences on COD removal and sludge settleability, but had significant inhibition effect on ammonia removal, especially for oNP. Low concentration of pCP and oNP (5mg/L) dosing resulted in protein and polysaccharide content increased in EPS, however, they were decreased at high pCP and oNP concentrations (>5mg/L). To oCP, the protein content in EPS was increased linearly with oCP concentration. Furthermore, metabolic uncouplers addition stimulated the production of PHB. Among three uncouplers, oCP could be an alternative uncoupler for sludg...

Proceedings of the Water Environment Federation, 2001

A biological nutrient removal (BNR) activatedsludge (AS) scheme incorporating external nitrificat... more A biological nutrient removal (BNR) activatedsludge (AS) scheme incorporating external nitrification in a fixed media system is evaluated. A laboratory scale investigation of the scheme indicates that it holds considerable potentialfor BNRAS system intensification through major reduction in sludge age and oxygen demand and significant improvement in sludge settleability. Because the BNRAS system is not required to nitrtfy, its anoxic mass fraction can be considerably enlarged at the expense of the aerobic mass fraction creating conditions that (i) allow it to achieve high N removals with domestic wastewaters with high TKN/COD ratios and (ii) promote anoxic P uptake polyphosphate accumulating organisms (PAO) to develop in the system. From this, andearlier investigations with conventional BNR systems, it appears that anoxic P uptake biological excess P removal (BEPR) is only about 2/3rds of aerobic P uptake BEPR. Inclusion of anoxic P uptake PAOs in, and exclusion of nitrtfiers from, the BNRAS system are not essentialfor the scheme. However, conditions that promote aerobic P uptake to maximize BEPR, are also conducive to nitrifier growth, which, if supported in the BNRAS system, would require virtual complete nitrification in the fixed media system to avoid nitrate interference with BEPR. Before the scheme can be implemented at large scale, an engineering and economic evaluation is required to quantify its potential benefits and savings.

Proceedings of the Water Environment Federation, 2008

ABSTRACT

Water Science & Technology, 2011

Water Science & Technology, 2011

A pilot study was conducted to test an membrane bioreactor (MBR) process for combined biological ... more A pilot study was conducted to test an membrane bioreactor (MBR) process for combined biological and chemical P removal to achieve a very low effluent total phosphorus (TP) concentration of 0.025 mg P/L. With the data from the pilot test, a simulation study was performed to demonstrate that: (1) the pilot system behaviour (effluent quality, MLSS, etc.) can be modelled accurately with an activated sludge model combined with a chemical precipitation model; and (2) with the calibrated model, simulation scenarios can be performed to further understand the pilot MBR process, and provide information for optimizing design and operation when applied at full-scale. Results from the pilot test indicated that the system could achieve very low effluent TP concentration through biological P removal with a limited chemical addition, and chemical addition to remove P to very low level did not affect other biological processes, i.e., organic and nitrogen removal. Simulation studies indicate that the process behaviour can be modelled accurately with an activated sludge model combined with a chemical precipitation model, and the calibrated model can be used to provide information to optimize system design and operation, e.g., chemical addition control under dynamic loading conditions is important for maintaining biological P removal.

Proceedings of the Water Environment Federation, 2008

ABSTRACT

Reviews in Chemical Engineering, 2019

With the rapid growth of economics and nanotechnology, a significant portion of the anthropogenic... more With the rapid growth of economics and nanotechnology, a significant portion of the anthropogenic emissions of heavy metals and nanoparticles (NPs) enters wastewater streams and discharges to wastewater treatment plants, thereby potentially posing a risk to the bacteria that facilitate the successful operation of the enhanced biological phosphorus (P) removal (EBPR) process. Although some efforts have been made to obtain detailed insights into the effects of heavy metals and metal (oxide) nanoparticles [Me(O)NPs], many unanswered questions remain. One question is whether the toxicity of Me(O)NPs originates from the released metal ions. This review aims to holistically evaluate the effects of heavy metals and Me(O)NPs. The interactions among extracellular polymeric substances, P, and heavy metals [Me(O)NPs] are presented and discussed for the first time. The potential mechanisms of the toxicity of heavy metals [Me(O)NPs] are summarized. Additionally, mathematical models of the toxici...

Bioresource Technology, 2016

h i g h l i g h t s P-removal efficiency decreased to 34.6% under the effect of ERY (10 mg/L). P-... more h i g h l i g h t s P-removal efficiency decreased to 34.6% under the effect of ERY (10 mg/L). P-removal efficiency decreased to 0.0% under the effect of OTC (10 mg/L). Aerobic stage in EBPR system was more seriously inhibited than anaerobic stage. OTC showed more serious inhibitory effect on microorganism's oxygen utilization. Neither synergistic effect nor antagonistic effect was detected between ERY and OTC.

Process Biochemistry, 2014

Enhanced biological phosphorus removal (EBPR) technology has been widely considered as a key stra... more Enhanced biological phosphorus removal (EBPR) technology has been widely considered as a key strategy in preventing eutrophication and recognized as the advancing front of research in wastewater treatment. The key to keep its high efficiency in biological phosphorus removal is to optimize the operation and management of the system. Previous research in this field has undoubtedly improved understanding of the factors hindered overall efficiency of EBPR. However, it is obvious that much remains to be learnt. This paper attempts to review the fundamental understanding in factors inhibiting the stability and reliability of the EBPR systems in the state-of-the-art research. In view of modeling the EBPR systems, an appropriate extension of the current mechanistic models with these inhibitory factors is recommended in order to better simulate and predict the behavior of full-scale and lab-scale EBPR plants. From the perspectives of the further mechanistic and multi-factors study, the direction of denitrifying dephosphatation and granules/biofilms are also discussed. This comprehensive overview will not only help us to understand the overall mechanism of the EBPR process, but also benefit the researchers and engineers to consider all the possible factors affecting the process in the urban sewage treatment plants.

Over the past decade, the concept of anaerobic processes for the treatment of low temperature dom... more Over the past decade, the concept of anaerobic processes for the treatment of low temperature domestic wastewater has been introduced. This paper uses a developed wastewater flowsheet model and experimental data from several pilot scale studies to establish the impact of integrating anaerobic process into the wastewater flowsheet. The results demonstrate that, by integrating an expanded granular sludge blanket reactor to treat settled wastewater upstream of the activated sludge process, an immediate reduction in imported electricity of 62.5% may be achieved for a treated flow of c. 10,000 m3 d−1. This proposed modification to the flowsheet offers potential synergies with novel unit processes including physico-chemical ammonia removal and dissolved methane recovery. Incorporating either of these unit operations can potentially further improve the flowsheet net energy balance to between +0.037 and +0.078 kWh m−3 of produced water. The impact of these secondary unit operations is significant as it is this contribution to the net energy balance that facilitates the shift from energy negative to energy positive wastewater treatment.

Proceedings of the Water Environment Federation, 2006

Transient or intermittent releases of specific volatile or semi-volatile organic compounds are no... more Transient or intermittent releases of specific volatile or semi-volatile organic compounds are not managed well by existing predictive fate models such as TOXCHEM+ or Water9 because they are based on steady-state conditions. In this paper, two scenarios for treatment of transient organic compound concentrations are studied using dynamic simulation: 1) Remedial actions (such as nutrient addition biodegradation, and use of off-line storage with slow return pumping to treatment) are compared to passive acceptance of the release in treatment. 2) For covered processes, strategies for managing headspace concentrations which may approach lower explosive limits are examined. Certain remedial strategies prove more effective in minimizing air emissions and effluent releases than others, demonstrating the benefits of the dynamic modeling approach.

Proceedings of the Water Environment Federation, 2006

In this paper the advantages and disadvantages of denitrifying PAOs in conventional BNRAS and ext... more In this paper the advantages and disadvantages of denitrifying PAOs in conventional BNRAS and external nitrification BNRAS (ENBNRAS) systems are evaluated, with experimental data exhibiting a range of anoxic P uptake from low (<10%) to very high (>60%). The results indicate that the specific denitrification rate of the PAOs on internally stored PHB COD is about 1/5th of that of the OHOs on SBCOD, and the PAOs contribute little (maximum 20%) to the denitrification in BNRAS systems even when the anoxic P uptake is high (60 % of the total P uptake). Considering the unpredictable nature of anoxic P uptake and the reduction in BEPR it causes compared with aerobic P uptake BEPR, it is concluded that anoxic P uptake does not add a significant advantage to the BNR system.

Proceedings of the Water Environment Federation, 2006

Proceedings of the Water Environment Federation, 2006

ABSTRACT Transient or intermittent releases of specific volatile or semi-volatile organic compoun... more ABSTRACT Transient or intermittent releases of specific volatile or semi-volatile organic compounds are not managed well by existing predictive fate models such as TOXCHEM+ or Water9 because they are based on steady-state conditions. In this paper, two scenarios for treatment of transient organic compound concentrations are studied using dynamic simulation: Remedial actions (such as nutrient addition biodegradation, and use of off-line storage with slow return pumping to treatment) are compared to passive acceptance of the release in treatment. For covered processes, strategies for managing headspace concentrations which may approach lower explosive limits are examined. Certain remedial strategies prove more effective in minimizing air emissions and effluent releases than others, demonstrating the benefits of the dynamic modeling approach.

Water Science & Technology

A biological nutrient removal (BNR) activated sludge (AS) scheme incorporating external nitrifica... more A biological nutrient removal (BNR) activated sludge (AS) scheme incorporating external nitrification in a fixed media system is evaluated. A laboratory scale investigation of the scheme indicates that it holds considerable potential for BNRAS system intensification through major reduction in sludge age and oxygen demand and significant improvement in sludge settleability. Because the BNRAS system is not required to nitrify, its anoxic mass fraction can be considerably enlarged at the expense of the aerobic mass fraction creating conditions that (i) allow it to achieve high N removals with domestic wastewaters with high TKN/COD ratios and (ii) promote anoxic P uptake polyphosphate accumulating organisms (PAO) to develop in the system. From this, and earlier investigations with conventional BNR systems, it appears that anoxic P uptake biological excess P removal (BEPR) is only about brds of aerobic P uptake BEPR. Inclusion of anoxic P uptake PAOs in, and exclusion of nitrifiers from, the BNRAS system are not essential for the scheme. However, conditions that promote aerobic P uptake to maximize BEPR, are also conducive to nitrifier growth, which, if supported in the BNRAS system, would require virtual complete nitrification in the fixed media system to avoid nitrate interference with BEPR. Before the scheme can be implemented at large scale, an engineering and economic evaluation is required to quantify its potential benefits and savings.

Acta Biotechnologica, 2003

The research was aimed at developing a technology to combine the production of useful microfungi ... more The research was aimed at developing a technology to combine the production of useful microfungi with the treatment of wastewater from food processing. A recycle bioreactor equipped with a microscreen was developed as a wastewater treatment system on a laboratory scale to contain a Rhizopus culture and maintain its dominance under non-aseptic conditions. Competitive growth of bacteria was observed, but this was minimised by manipulation of the solids retention time and the hydraulic retention time. Removal of about 90% of the waste organic material (as BOD) from the wastewater was achieved simultaneously. Since essentially all fungi are retained behind the 100 µm aperture screen, the solids retention time could be controlled by the rate of harvesting. The hydraulic retention time was employed to control the bacterial growth as the bacteria were washed through the screen at a short HRT. A steady state model was developed to determine these two parameters. This model predicts the effluent quality. Experimental work is still needed to determine the growth characteristics of the selected fungal species under optimum conditions (pH and temperature).

Proceedings of the Water Environment Federation, 2002

Abstract A selected microfungal species was cultivated on corn processing wastewater in batch cul... more Abstract A selected microfungal species was cultivated on corn processing wastewater in batch culture and in a continuous system with microscreen separation. Results have demonstrated the feasibility of growing the selected fungal species on this wastewater. The COD ...

Proceedings of the Water Environment Federation, 2006

... The original cycle settings are shown in the center of Table 3. The design objectives for eff... more ... The original cycle settings are shown in the center of Table 3. The design objectives for effluent and maximum MLSS in the reactor for the SBR plant are shown in Table 4. Table 3: Cycle Settings for the Designed and Optimal SBR Process SBR Phases Phase length (minutes ...

Water science and technology : a journal of the International Association on Water Pollution Research, 2002

In this paper the advantages and disadvantages of denitrifying PAOs (polyphosphate accumulating o... more In this paper the advantages and disadvantages of denitrifying PAOs (polyphosphate accumulating organisms) in conventional BNRAS (biological nutrient removal activated sludge) and external nitrification BNRAS (ENBNRAS) systems are evaluated, with experimental data exhibiting a range of anoxic P uptake from low (<10%) to very high (>60%). The results indicate that the specific denitrification rate of the PAOs on internally stored PHB COD is about 1/5th of that of the "ordinary" heterotrophic organisms on SBCOD, and the PAOs contribute little (maximum 20%) to the denitrification in BNRAS systems even when the anoxic P uptake is high (60% of the total P uptake). Considering the unpredictable nature of anoxic P uptake and the reduction in BEPR it causes compared with aerobic P uptake BEPR, it is concluded that anoxic P uptake does not add a significant advantage to the BNR system.

Bioresource technology, Jan 19, 2015

The present study investigated the influences of three metabolic uncouplers (pCP, oCP and oNP) on... more The present study investigated the influences of three metabolic uncouplers (pCP, oCP and oNP) on excess activated sludge reduction and microbial products of extracellular polymeric substances (EPS) and intracellular storage product (polyhydroxybutyrate, PHB) in short-term tests. Results showed sludge was reduced 58.2%, 59.8% and 80.8%, respectively, at pCP, oCP and oNP concentrations of 20mg/L. The dosage of three uncouplers had no obviously influences on COD removal and sludge settleability, but had significant inhibition effect on ammonia removal, especially for oNP. Low concentration of pCP and oNP (5mg/L) dosing resulted in protein and polysaccharide content increased in EPS, however, they were decreased at high pCP and oNP concentrations (>5mg/L). To oCP, the protein content in EPS was increased linearly with oCP concentration. Furthermore, metabolic uncouplers addition stimulated the production of PHB. Among three uncouplers, oCP could be an alternative uncoupler for sludg...

Proceedings of the Water Environment Federation, 2001

A biological nutrient removal (BNR) activatedsludge (AS) scheme incorporating external nitrificat... more A biological nutrient removal (BNR) activatedsludge (AS) scheme incorporating external nitrification in a fixed media system is evaluated. A laboratory scale investigation of the scheme indicates that it holds considerable potentialfor BNRAS system intensification through major reduction in sludge age and oxygen demand and significant improvement in sludge settleability. Because the BNRAS system is not required to nitrtfy, its anoxic mass fraction can be considerably enlarged at the expense of the aerobic mass fraction creating conditions that (i) allow it to achieve high N removals with domestic wastewaters with high TKN/COD ratios and (ii) promote anoxic P uptake polyphosphate accumulating organisms (PAO) to develop in the system. From this, andearlier investigations with conventional BNR systems, it appears that anoxic P uptake biological excess P removal (BEPR) is only about 2/3rds of aerobic P uptake BEPR. Inclusion of anoxic P uptake PAOs in, and exclusion of nitrtfiers from, the BNRAS system are not essentialfor the scheme. However, conditions that promote aerobic P uptake to maximize BEPR, are also conducive to nitrifier growth, which, if supported in the BNRAS system, would require virtual complete nitrification in the fixed media system to avoid nitrate interference with BEPR. Before the scheme can be implemented at large scale, an engineering and economic evaluation is required to quantify its potential benefits and savings.

Proceedings of the Water Environment Federation, 2008

ABSTRACT

Water Science & Technology, 2011

Water Science & Technology, 2011

A pilot study was conducted to test an membrane bioreactor (MBR) process for combined biological ... more A pilot study was conducted to test an membrane bioreactor (MBR) process for combined biological and chemical P removal to achieve a very low effluent total phosphorus (TP) concentration of 0.025 mg P/L. With the data from the pilot test, a simulation study was performed to demonstrate that: (1) the pilot system behaviour (effluent quality, MLSS, etc.) can be modelled accurately with an activated sludge model combined with a chemical precipitation model; and (2) with the calibrated model, simulation scenarios can be performed to further understand the pilot MBR process, and provide information for optimizing design and operation when applied at full-scale. Results from the pilot test indicated that the system could achieve very low effluent TP concentration through biological P removal with a limited chemical addition, and chemical addition to remove P to very low level did not affect other biological processes, i.e., organic and nitrogen removal. Simulation studies indicate that the process behaviour can be modelled accurately with an activated sludge model combined with a chemical precipitation model, and the calibrated model can be used to provide information to optimize system design and operation, e.g., chemical addition control under dynamic loading conditions is important for maintaining biological P removal.