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Transcript of Algae Removal from a Facultative Lagoon System Using Dissolved Air Flotation … · Algae Removal...
Algae Removal from a Facultative Lagoon System Using Dissolved Air Flotation
J. Patrick Pierce, P.E. Environmental Treatment Systems, Inc.
• Designed for 1.5 MGD • Discharging 1.15-1.35 MGD • Serving a population of 15,000
Facultative Lagoon System
D) Outfall from the facultative lagoon system to lift station
E) Future location for DAF installation
F) Final discharge magnetic flow meter
G) Lift station pumps
Site Prior to DAF Installation
A) Control Building for Lift Station Pumps
B) Gaseous chlorine and sodium bi-sulfite building
C) Chlorination/de-chlorination contact chamber
Background
• The Plant’s existing wastewater treatment infrastructure consisted of:
• 52 Acre Facultative Lagoon System (1960) • Upgraded with Curtain Baffles in 1980’s • Aerators Added to Lagoons at Same Time to
Increase D.O. Levels • Chlorine Contact Chamber added in 2007 • Plant Still Unable to Meet NPDES Permit • Malcolm-Pirnie (Arcadis, U.S.) Contracted to
Evaluate Additional Treatment Options
Background
• The issue and next step: – Excessive algae growth in the lagoon system is causing
a violation of their TSS and cBOD5 discharge limit per their NPDES permit
– Consulting engineering firm reviewed five (5) different technologies to remove the algae
• Mechanical Filtration • Coagulation – Flocculation • In-Pond Removal Methods • Granular Media Filtration • Dissolved Air Flotation
Background
Final evaluation and testing for solutions • Bench scale Precipitation and Sedimentation • Bench scale Precipitation and Filtration • Bench scale Precipitation and Flotation
Conclusion:
• Bench-scale testing on all technologies showed DAF to be the best overall choice for algae removal • Commission a pilot test with chemical flocculation followed by DAF to remove algae from the lagoon effluent
Evaluate
Determine
Determine
Approximate
Confirm
Develop
Evaluate the treatment performance of a DAF system for the removal of algae from biologically treated wastewater prior to disinfection and final discharge.
Determine a chemical program that would be effective and economical for flocculation prior to flotation.
Determine the approximate chemical consumption requirements using a DAF system.
Approximate the amount of solids generated using a DAF system.
Confirm the initial design parameters of the system.
Aid Consulting Engineer in developing the process design for a full-scale DAF system for algae removal.
DAF Pilot Study Goals
DAF Overview
DAF Process Overview
Contact Chamber Flotation Cell Top Skimmer System
Effluent Discharge Chamber & Weirs
Float/Skimmings Chamber
Rotameter Air Eductor Air Dissolving Pipe (ADP)
Whitewater Injection Ports & Valves
Bottoms Removal
Pilot DAF System Setup on Site
Algae Laden Effluent in Chlorine Contact Chamber
Pilot Study 2009 Methodology
• November 10-12, 2009 • Samples collected twice daily • Total TSS tests run – six (6) • Skid mounted Small DAF with • Two mix tanks & • Chemical feed components
oSingle flocculent used in the study: cationic polymer @ 5 ppm
Test # Flow Flocculent Flocculent Dosage
Influent cBOD5
Effluent cBOD5
Removal Influent TSS
Effluent TSS Removal Total Solids
Produced 1
GPM Charge ppm mg/L mg/L % mg/L mg/L % lbs/hr
1 15 Cationic 5 - 4 - - 8 - -
2 15 Cationic 5 - 3 - - 14 - -
3 15 Cationic 5 21 3 85.7 93 11 88.2 0.62
4 15 Cationic 5 15 3 80.0 62 10 83.9 0.39
5 15 Cationic 5 15 3 80.0 58 6 89.7 0.39
6 15 Cationic 5 13 4 69.2 49 12 75.5 0.28
Study Average 15 N/A 5 16 3 78.7 66 9.8 84.3 0.42
1 Total solids are on a dry matter basis.
DAF Pilot Study Operating Conditions & Results
Tota
l Sus
pend
ed S
olid
s, m
g/L
Pilot Test Number 1 2 3 4 5 6
120
100
80
60
40
20
0
Pilot Study TSS Removal Data Influent TSS Effluent TSS Influent Sample Not Taken
Full-Scale DAF System – Design
Parameter Units Design Notes/References
Forward Flow MGD 1.5 Design flow based on peak flow to lagoon system
Total Suspended Solids
mg/L 300 Design maximum
Solids Mass Loading lbs/hr 156 Calculated
Recycle Pressure psi 90 Typical range is 80-100 per ETS design
Air Solution Rate SCFH 120 By design
Recycle Rate gpm 150 N/A
Recycle % 18 15% to 25% is typical for ETS designs
Flotation Surface Area ft2 240 By design
Hydraulic Loading gal/min/ft2 4.3 Based on pilot DAF Test Typical ETS design range is 2-6 gal/min/ft2
Solids Loading lbs/hr/ft2 0.65
Low based on typical ETS designs; low TSS effluent requirement and hydraulic loading dictated the DAF unit size as well as pilot operating data
Air to Solids Ratio lbs/lbs 0.057 0.006 to 0.070 (WEF MOP-FD-3, 1994)
Process Flow Diagram of the Full-Scale DAF Algae Removal System
Full-Scale Algae Removal DAF Unit Installed on Site
Full-Scale DAF in Operation
Comparison of Pilot-Scale and Full-Scale DAF Performance
Influent TSS Effluent TSS TSS Removal
Influent cBOD5
Effluent cBOD5
cBOD5 Removal
mg/L mg/L % mg/L mg/L % Average Before DAF Unit Installation
97 61 37.1 61 25 59
Average During Pilot Study
66 1 9.8 84.3 2 16 1 3 78.7 2
Average After DAF Unit Installation
147 29 80.3 107 12 88.8
• NPDES Permit requires removal efficiencies of 65% for TSS and 85% for carbonaceous BOD5. 1 Influent sampled at pilot DAF Unit; all others at headworks of lagoon 2 Removal is based solely on pilot DAF Unit performance which is used for TSS removal since no coagulants were used
Operational Data Before and After the DAF Unit Installation
MONTH
2013 2014
INFLUENT EFFLUENT INFLUENT EFFLUENT
TSS (mg/L) cBOD5 (mg/L) TSS (mg/L)
cBOD5 (mg/L) TSS (mg/L)
cBOD5 (mg/L) TSS (mg/L)
cBOD5 (mg/L)
January 72 110 52 17 173 142 17 6
February 67 88 60.5 18.5 76 102 30 15.5
March 76 117 27 16.5 68 74 19 17.5
April 122 108.5 73 28.5 57 47 21 9.5
May 112 128 59 30 100 75.5 43.5 15.5
June 27 73 80 42.5 126.5 62.5 26 9.5
July 151 144.5 71 38.5 223 143 50 23.5
August 85 114 76.5 24.5 68 115.5 40 11.5
September 87 84.5 82 28 N/A N/A N/A N/A
October 83 98.5 40.5 24 335 182 23.5 7.5
November 116 119 55 20.5 N/A N/A N/A N/A
December 165 95.5 56 15.5 242 127.5 20 8.5
AVERAGE 97 107 61 25 147 107 29 12
* TSS and cBOD5 readings are resultant monthly averages from two samples.
** N/A results indicate months of no discharge from the lagoon and therefore no samples were recorded.
Issues After DAF Unit Installation
• Variation in Influent Total Suspended Solids – Seasonal Algal Blooms – Heavy Rain Events
• Variation in Polymer Dosing – Attempts to Reduce Usage = Carryover in Effluent – Changing Polymer Vendors
• DAF Float Pumping – Float Material Too Thick to Flow to Sump – Submersible Grinder Pump Not Positive Displacement
Conclusion
• Full scale system is operating as anticipated • System is allowing the City to meet NPDES
Permit Requirements of 65% and 85% removal
Acknowledgements
Charles H. Starling III, P.E. BCEE – ARCADIS U.S.,Inc. 5 N. Conception St., Suite 200 Mobile, AL 36602 Charles C. Ross, P.E. – Environmental Treatment Systems, Inc. 4310 McEver Industrial Drive, Acworth, GA 30101 G. Edward Valentine – Environmental Treatment Systems, Inc. 4310 McEver Industrial Drive, Acworth, GA 30101