settling performance in wastewater fed high rate algae ponds

103 Pages·2013·6.23 MB·English

by  Elliott Blake Ripley

SETTLING PERFORMANCE IN WASTEWATER FED HIGH RATE ALGAE PONDS

A Thesis
presented to
the Faculty of California Polytechnic State University,
San Luis Obispo

In Partial Fulfillment
of the Requirements for the Degree
Master of Science in Civil and Environmental Engineering

by
Elliott Blake Ripley
June 2013
© 2013

Elliott Blake Ripley

ALL RIGHTS RESERVED

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COMMITTEE MEMBERSHIP
TITLE: Settling Performance in Wastewater Fed High Rate
Algae Ponds

AUTHOR: Elliott Blake Ripley

DATE SUBMITTED: June 2013

COMMITTEE CHAIR: Dr. Tryg Lundquist
Environmental Engineering Department

COMMITTEE MEMBER: Dr. Yarrow Nelson
Environmental Engineering Department

COMMITTEE MEMBER: Dr. Christopher Kitts
Biology Department

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ABSTRACT
SETTLING PERFORMANCE IN WASTEWATER FED HIGH RATE ALGAE PONDS

ELLIOTT BLAKE RIPLEY

Keywords: Extracellular polymeric substances, bioflocculation, high rate algae ponds,
wastewater treatment, settling

Although high rate algae ponds (HRAPs) are a proven wastewater treatment technology
with numerous environmental, social, and economic benefits, their widespread use has
been hindered by inconsistent and unreliable settling performance. Hence, the goal of
this thesis is to investigate how specific operational parameters affect the settling
performance of HRAPs. Nine HRAPs (30 m2 surface area, 0.3 m depth) were operated as
three triplicate sets, with each set run on either a 2, 3, or 4 day HRT continuously from
January 25, 2012 through April 11, 2013. Settling performance was determined (i) by
measuring the TSS of Imhoff cone supernatant after 2 and 24 hours of settling and (ii) by
measuring the TSS of tube settler effluent. Ponds operating on 2 - 3 day HRTs (loading
rate was 24 - 36 g/m3-day csBOD and food to microorganism (F/M) ratio was 0.13 -
5
0.21 day-1) were able to settle consistently with residual TSS averaging less than 40 mg/L
after 2 hours of settling time. Tube settlers showed potential as effective harvesting
devices; ponds operating on a 2-day HRT averaged 27.9 ± 9.2 mg/L TSS in tube settler
effluent at an overflow rate (OFR) of 9.4 L/min-m2. Microscopy analysis was performed
and relationships were made between settling performance and algae dominance and floc
structure.

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ACKNOWLEDGMENTS
I would like to express my sincere gratitude to those who have helped me during my
research:

To the San Luis Obispo Water Reclamation Facility administration and operations, thank
you for sharing the land to build and operate the Algae Field Station. Especially, thank
you to the water lab staff for your flexibility, advice, and friendship. This project would
not be possible without your support.
To all the undergraduate students that helped with this project, thank you for making lab
work fun. This research could not have been done without you.

To Mike Chang and Max Wallack, your willingness to work and laboratory skills were
invaluable. Thank you for your friendship and dedication.

To Ian Woertz, I admire the knowledge, diligence, and skill you put into your work.
Thank you for always willing to share your expertise.

To Dr. Chris Kitts, your expertise in microbiology brought a unique and valuable
perspective to this research. Thank you for your advice and guidance.

To Dr. Yarrow Nelson, you have inspired me to always be curious. Thank you for your
creative advice and mentorship over the past six years.

To Dr. Tryg Lundquist, you have taught me more this past year than I thought possible.
Thank you for this experience.

To Matt Rodrigues, I have never worked with anyone as well as I work with you. Thank
you for your friendship, insight, and sacrificing your living room and kitchen table so I
can write this thesis.

To my family, who wholeheartedly supports me in everything I do. Thank you for
believing in me regardless of circumstance.

To my girlfriend Laura, you have helped me with this thesis more than you know. Thank
you for reminding me that this is just the beginning.

This project was funded by the California Energy Commission and the U.S. Office of
Naval Research via the Cal Poly California Central Coast Research Partnership.
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Contents
1. Introduction 1 
1.1 Algae as a Resource 1 
1.2 Algae in Wastewater Treatment 2 
2. Background 4 
2.1 Significance and Mechanisms of Bioflocculation 4 
2.2 EPS, Surface Properties, and Bioflocculation 5 
2.3 Retention Times and Bioflocculation 9 
2.4 Algae Recycling, Species Dominance, and Settling 10 
2.5 Activated Sludge Incorporation into Algae Flocs 12 
2.6 Settleability of Diatoms 13 
2.7 Tube Settling of Algae 14 
2.8 Purpose of This Thesis 14 
3. Methods and Materials 15 
3.1 Algae Field Station: Layout 15 
3.2 Algae Field Station: Process Flow and Operation 16 
3.2.1 Nomenclature 16 
3.2.2 Process Flow 16 
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3.2.3 Operation 22 
3.3 Pond Specifications 24 
3.4 Tube Settler Specifications 25 
3.5 Regular Operations and Maintenance 26 
3.6 Water Quality Sampling and Analysis 26 
3.6.1 Sampling and Analysis Procedure 26 
3.6.2 Total and Volatile Suspended Solids 28 
3.6.3 Settling Tests 28 
3.6.4 Biochemical Oxygen Demand 30 
3.6.5 Microscopy Analysis 30 
3.7 Weather Data 31 
3.8 Graphical and Statistical Analysis 31 
3.9 Sludge Accumulation 31 
4. Results and Discussion 33 
4.1 Introduction to Settling Performance Study 33 
4.1.1. Review of Nomenclature and Measurements 33 
4.1.2 Statistical Presentation of Data 34 
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4.1.3 Period of Study for Each Measurement 34 
4. 2 Settling Performance 36 
4.2.1 Settling Performance: Alpha Ponds 37 
4.2.2 Settling Performance: Beta Ponds 39 
4.2.3 Settling Performance: Gamma Ponds 41 
4.2.4 Food to Microorganism Ratio and Settling Performance 44 
4.2.4 Soluble Organic Loading Effect on Settling Performance 49 
4.2.5 Algal Genera, Floc Structure, and Settling Performance 50 
4.2.6 Discussion of Settling Performance 58 
4.3 Relationship Between Imhoff Cone and Tube Settler Performance 59 
4.3.1 Imhoff Cone and Tube Settler Correlations 59 
4.3.2 Comparison to Activated Sludge Overflow Rates 62 
5. Conclusions 64 
5.1 Experimental Conclusions 64 
5.2 Limitations of Study 65 
5.3 Further Research 66 
References 68 
Appendix A. 73 
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Appendix B. 80 
Appendix C. 82 
Appendix D. 87 
Appendix E. 88 
Appendix F. 89 

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List of Tables

Table 3.1: Relevant HRAP sizing and operational specifications. ................................... 24 
Table 3.2: Relevant tube settler sizing and operational specifications. ............................ 25 
Table 3.3: Weekly sample schedule and sample type. ...................................................... 27 
Table 4.1: Average csBOD loading rates for each pond set ............................................ 35 
5 
Table 4.2: Period of study for each measurement. ............................................................ 36 
Table 4.3: Average measurements of 2-hour, 24-hour, and tube settler TSS ................... 36 
Table 4.4: F/M Ratios of Alpha, Beta, and Gamma sets. ................................................. 46 
Table 4.5: HRAP F/M ratios compared to CMAS F/M ratios .......................................... 47 
Table 4.6: Environmental and operational variables for Pond 1 and Pond 9 ................... 57 
Table 4.7: AFS tube settler OFRs compared to typical secondary clarifier OFRs ........... 63 
Table A.1: Pond 8 TSS measurements, December 12, 2012 ............................................ 74 
Table A.2: Comparison of weir and orifice standpipe designs, Jan 27, 2013 ................... 75 
Table A.3: Comparison of weir and orifice standpipes, Feb 27, 2013 ............................. 75 
Table A.4: Pond 1 and Pond 8 TSS balance, Feb 17, 2013. ............................................. 78 
Table C.1: Settling data by season .................................................................................... 87 
Table D.1: Relevant operations and experiments schedule. ............................................. 88 
Table F.1: Average settling data, July 5, 2012 - April 11, 2013. ...................................... 89 

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