Biological Nutrient Removal: Minimizing Carbon and Oxygen Requirements

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Biological Nutrient Removal: Minimizing Carbon and Oxygen
Requirements, Is A Well-Researched Topic, It Is To Be Used As A Guide Or Framework For Your Research.

ABSTRACT

With increasing focus on the carbon footprint of wastewater treatment and rapidly emerging paradigm shift towards resource recovery, energy consumption minimization and utilization of readily available organics for biological nutrient removal in municipal wastewater treatment plants is eliciting significant interest. The objective of this PhD work is to investigate non-traditional approach to minimize carbon and energy demand for biological nutrient removal

The feasibility of using thermal alkaline treated municipal wastewater biosolids as an alternative carbon source for biological phosphorus removal was investigated. Two sequencing batch reactors (SBRs) were operated with synthetic volatile fatty acids (acetic acid and propionic acid) and readily biodegradable organics produced from the alkaline hydrolysis of municipal wastewater biosolids (Lystek) as the carbon source, respectively. Municipal wastewaters with different strengths and COD:N:P ratios were tested. The reactors’ performances were found to be comparable with respect to nitrogen and phosphorus removal. It was observed that phosphorus removal efficiencies were between 98% to 99% and 90% to 97% and nitrogen removal efficiencies were 78% to 81%, and 67% for the SynVFA and Lystek, respectively. However, the kinetics for phosphorus release and uptake during the anaerobic and aerobic stages with Lystek were observed to be significantly lower than SynVFA due to the presence of higher order VFAs (C4 and above) and other fermentable organics in the Lystek.

A novel integrated partial nitrification-denitrifying phosphorus removal system enriched with non-conventional phosphorus accumulating organisms (PAOs) was developed for treating carbon limited synthetic wastewater. Atypical operating conditions, such as low DO (0.3±0.05 mg/L) and relatively long solid retention time (SRT) of 15 days, favored the enrichment of a wide variety of denitrifying phosphorus accumulating organisms (DPAOs), such as Rhodocyclus, Dechloromonas, and Cytophaga. In contrast to the Accumulibacter, these microorganisms can sustain in a very low DO environments and simultaneously perform denitrification and enhanced biological phosphorus removal (EBPR) using oxygen, nitrite, and nitrate as electron acceptors. Fermentative microorganisms, such as Bacteroidetes, were also observed. Low DO also favored the washout of nitrite oxidizing bacteria (NOB), leading to simultaneous partial nitrification-denitrifying phosphorus removal (PNDPR). Partial nitrification at low DO also facilitated the washout of glycogen accumulating organisms (GAOs) from the PNDPR system. When operated with synthetic wastewater, stable operating conditions were achieved within 3-4 SRT turnovers and simultaneous nitritation-denitritation (SND), nitrogen, and phosphorus removal efficiencies were maintained above 90%. Of the total P removed by EBPR, P-removal percentages via nitrite, nitrate, and oxygen were 69%, 23%, and 8%, respectively. Utilizing nitrite instead of nitrate and low DO aeration implies a significant reduction in carbon and aeration requirement for simultaneous denitrification and phosphorus removal.

Lastly, the PNDPR system was implemented for treating real municipal wastewater with low COD/N ratio. In addition to low DO (0.3±0.05) mg/L, an extended anaerobic contact time facilitated the efficient utilization of organic carbon in wastewater and nutrient removal without carbon supplementation. Low DO during the aerobic stage was favorable for anoxic P-removal rather than aerobic as evidenced by simultaneous N and P removal in the cyclic test. Most of the rapid initial P uptake during the aerobic phase was attributed to DPAOs utilizing nitrites rather than nitrates, with NOx-N accumulating after almost complete utilization of the stored PHA and associated P uptake.

The ratio of COD utilized to NOx-N reduced was estimated to be 4.2, which also implies efficient utilization of carbon for nutrient removal. Due to the integration of nitrification with denitrifying phosphorus removal, more than 70% N-removal and 90% P-removal was observed even at low COD/N ratio of 5. COD removal was not impacted by low DO as effluent sCOD concentrations were consistently below 25 mg/L. Compared to the conventional EBPR process, the low DO-SNDPR process implies maximum reductions in energy and carbon consumption of 35% and 45%, respectively. This can significantly reduce the overall carbon footprint of municipal wastewater treatment plants.

TABLE OF CONTENT

Abstract ……………………………………………………………………………………………………………………. ii
Summary for Lay Audience ……………………………………………………………………………………….. iv
Acknowledgements ……………………………………………………………………………………………………. v
Co-Authorship Statement…………………………………………………………………………………………… vi
Table of Contents …………………………………………………………………………………………………….. vii
List of Tables ……………………………………………………………………………………………………………. x
List of Figures ………………………………………………………………………………………………………….. xi
List of Appendices …………………………………………………………………………………………………… xii
List of Abbreviations and Symbols……………………………………………………………………………. xiii
Chapter 1 ………………………………………………………………………………………………………………….. 1
Introduction ………………………………………………………………………………………………………………. 1
1. Rationale …………………………………………………………………………………………………………… 2
1.2. Research Objectives …………………………………………………………………………………………. 4
1.3. Thesis Organization …………………………………………………………………………………………. 4
1.4. Thesis Format………………………………………………………………………………………………….. 6
References …………………………………………………………………………………………………………….. 7
Chapter 2 ………………………………………………………………………………………………………………….. 9
Literature Review………………………………………………………………………………………………………. 9
1.Background ………………………………………………………………………………………………………. 10
2 Municipal Wastewater Characteristics …………………………………………………………………. 11
2.1. Organics ……………………………………………………………………………………………………. 11
2.2 Solids…………………………………………………………………………………………………………. 11
2.3 Nitrogen …………………………………………………………………………………………………….. 12
2.4. Phosphorus ………………………………………………………………………………………………… 12
3. Regulations and guidelines ………………………………………………………………………………… 13
4.Fundamentals of biological nitrogen and phosphorus removal ………………………………… 14
4.1. Nitrogen removal ……………………………………………………………………………………….. 14
4.2. Enhanced biological phosphorus removal (EBPR)………………………………………….. 19
4.3. Denitrifying EBPR (DPR) ………………………………………………………………………………. 31
5. Synopsis of the literature …………………………………………………………………………………… 36
6. Knowledge gaps ……………………………………………………………………………………………….. 37
References …………………………………………………………………………………………………………… 39
Chapter 3 ………………………………………………………………………………………………………………… 49
Enhanced Biological Phosphorus Removal Using Thermal Alkaline Hydrolyzed Municipal Wastewater Biosolids……………………………………………………………………………………………….. 49
1.Introduction ………………………………………………………………………………………………………. 50
2.Materials and methods ……………………………………………………………………………………….. 52
2.1 Sludge and wastewater …………………………………………………………………………………. 52
2.2 Analytical methods ……………………………………………………………………………………… 53
2.3 Sequencing Batch Reactors operation ……………………………………………………………. 54
3 Results and discussion ……………………………………………………………………………………….. 55
3.1 Wastewater and Lystek biosolids characteristics ……………………………………………… 55
3.2 Effluent quality and reactors’ operational performance ……………………………………. 56
3.3 Nitrogen and phosphorus mass balance ……………………………………………………………… 60
3.4 Kinetics of phosphorus release and uptake in the SBRs ……………………………………. 65
3.5 Implication of Lystek process in full-scale EBPR plants ………………………………….. 67

3 Conclusions ………………………………………………………………………………………………………. 69
References …………………………………………………………………………………………………………… 70
Chapter 4 ………………………………………………………………………………………………………………… 73
Impact of Dissolved Oxygen Concentration and DPAOs: Nitrifiers Population Ratio on Nutrient Removal in the EBPR Process……………………………………………………………………… 73
1.Introduction ………………………………………………………………………………………………………. 74
2.Materials and Methods ……………………………………………………………………………………….. 74
2.1. Sludge and wastewater ………………………………………………………………………………… 74
2.2. Analytical methods …………………………………………………………………………………….. 75
3.Results and discussions ………………………………………………………………………………………. 75
3.1. DPOAs enrichment in mother SBR reactor ……………………………………………………. 75
3.2. Partial nitrification at low DO………………………………………………………………………. 77
3.3. Batch study on nitrifiers and DPAOs mixed sludge at various nitrifying to DPAO sludge mass ratios …………………………………………………………………………………………….. 77
4. Conclusion ………………………………………………………………………………………………………. 80
References …………………………………………………………………………………………………………… 81
Chapter 5 ………………………………………………………………………………………………………………… 82
Partial Nitrification-Denitrifying Phosphorus Removal (PNDPR) For Energy and Carbon Minimization …………………………………………………………………………………………………………… 82
1. Introduction ……………………………………………………………………………………………………… 83
2. Materials and Methods ………………………………………………………………………………………. 86
2.1. DPAO enrichment sequencing batch reactor ………………………………………………….. 86
2.2. PNDPR sequencing batch reactor …………………………………………………………………. 86
2.3. Wastewater and seeding sludge ……………………………………………………………………. 87
2.4. Analytical Methods …………………………………………………………………………………….. 87
2.5. Simultaneous nitrification-denitrification (SND) efficiency …………………………….. 88
2.6. Inline and batch cyclic studies ……………………………………………………………………… 88
2.7. Microbial Analysis ……………………………………………………………………………………… 90
3. Results and Discussions …………………………………………………………………………………….. 90
3.1 DPAOs enrichment in mother SBR reactor …………………………………………………….. 90
3.2 Start up and operational performance of the PNDPR system …………………………….. 91
3.3 Nitrogen and Phosphorus mass balance at steady state …………………………………….. 94
3.4 Inline cyclic studies in the PNDPR-SBR system ……………………………………………… 95
3.5. Batch studies for evaluation of N and P removal pathways ……………………………… 96
3.6 Contribution of nitrifiers, DPAOs, and various electron acceptors to overall nutrient removal …………………………………………………………………………………………………………. 101
3.7 Microbial Community Analysis …………………………………………………………………… 102
4. Conclusions ……………………………………………………………………………………………………. 104
References …………………………………………………………………………………………………………. 106
Chapter 6 ………………………………………………………………………………………………………………. 111
Simultaneous Nitrification-Denitrifying Phosphorus Removal (SNDPR) at low DO for treating carbon-limited municipal wastewater ……………………………………………………………. 111
1.Introduction …………………………………………………………………………………………………….. 112
2.Materials and Methods ……………………………………………………………………………………… 115
2.1. Wastewater and seed sludge ………………………………………………………………………. 115
2.2. Batch activity tests of DPAO inoculum ……………………………………………………….. 115
2.3. Analytical methods …………………………………………………………………………………… 116
2.4 Simultaneous nitrification-denitrification (SND) efficiency ……………………………. 116

3.Results and Discussions ……………………………………………………………………………………. 118
3.1. DPAOs inoculum and wastewater characteristics …………………………………………. 118
3.2. Effluent quality and operational performance of SNDPR-SBR ……………………… 120
3.3. N-P distribution and mass balances …………………………………………………………….. 130
4. Summary and Conclusions ………………………………………………………………………………. 133
References …………………………………………………………………………………………………………. 134
Chapter 7 ………………………………………………………………………………………………………………. 138
Conclusions and recommendations for future work ……………………………………………………. 138
7.1 Conclusions ………………………………………………………………………………………………….. 139
7.2. Recommendations for future research …………………………………………………………….. 141
Appendices ……………………………………………………………………………………………………………. 142

Additional information

Author

Masuduz Zaman

No of Chapters

7

No of Pages

172

Reference

YES

Format

PDF

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