By

Everett Eustance, Joshua Wray and Milton Sommerfeld

Arizona Center for Algae Technology and InnovationArizona State University, Polytechnic Campus, Mesa, AZ 85212

Algae Biomass Organization SummitSeptember 29 – October 2, 2014

San Diego, CA

Effectively Utilizing Concentrated Nutrient Sources from Anaerobic Digesters and Dairy

Lagoons for Algae Cultivation

2

• Why wastewater?

• What makes a good culture medium?

• Challenges of using wastewater as a medium

• Collection sites/sources

• Analysis of wastewaters

-Chemistry

-Turbidity

• Ammonium (pH and aeration)

• Summary

Overview

Why Wastewater?• US:32 BGD (Billion

gallons per day)

• Arizona: 0.6 BGD

– Municipalities:

0.47 BGD

– Industry,

dairies, farm

runoff, etc.

http://ofmpub.epa.gov/cwns2008reports/database/CWNS_2008_DATA_DICT

IONARY.htm#Flow_Data

http://large.stanford.edu/courses/2011/ph240/xie1/

What Makes a Good Algae Culture Medium? Two key components: Nutrients and Water clarity

BG-11Full Bg-11

mg/L¼ BG-11

NaNO3 1500 375.00

K2HPO4 38.3 9.58

MgSO4·7H2O 7.4 1.85

CaCl2·2H2O 10.7 2.68

Citric Acid·H2O 6.3 1.58

Ammonium Ferric

Citrate5.2 1.30

Na2EDTA·2H2O 0.74 0.19

Na2CO3 19.1 4.78

H3BO3 2.8 0.70

MnCl2·4H2O 1.8 0.45

ZnSO4·7H2O 0.22 0.06

Na2MoO4·2H2O 0.39 0.10

CuSO4·5H2O 0.07 0.02

Co(NO3)2·6H2O 0.05 0.01

Media clarity/turbidity OD 450 OD 750

Distilled water 0.049 0.051

BG-11 Medium 0.054 0.053

Wastewater Sources

Greenfield WRPChandler AWRF

Van Rijn Dairy Johnson Utilities

• Sources tested:

– Van Rijin Dairy

– Johnson Utilities (2°)

• Anthem, Village Lane

and Pecan Creek

– Chandler Airport Water

Reclamation Facility

(AWRF) (2°)

– Greenfield Water

Reclamation Plant

(WRP) (2° and

digester)

Challenges of using Wastewater

• Wastewater treatment plants remove nutrients from water efficiently

• Digestion of solids is costly– Aerobic: energetically expensive

– Anaerobic: increased retention time, methane, infrastructure, permitting issues

• pH, alkalinity, contaminating species

• Ammonia is available but can be toxic– volatile

• Turbidity

Wastewater Analysis—Micronutrients

Chandler

AWRFAnoxic Beg Oxic End Oxic Clarifier AWRF

effluent

Anthem

effluent

Village

Lane

effluent

Pecan

Creek

effluent

Digester

CentrateDairy

¼ BG-

11Pretreat Stage 1 Stage 2 Stage 3 Stage 4

B .4588 .3525 .3544 .3477 .3505 .4328 .4220 .4648 .3654 1.0495 1.0475 0.124

Ca 78.67 73.02 72.72 73.91 72.86 73.49 94.74 56.89 59.50 371.55 377.75 2.004

Co .0022 .0015 .0013 .0023 .0022 .0077 .0012 - - 0.0075 0.005 0.003

Cu .0211 .0110 .0098 .0087 .0085 .0258 .0113 .0471 .0135 0.035 0.0895 0.005

Fe .0569 .0208 .0030 - .0361 - 0.2015 0.273 0.279

K 20.99 28.19 24.74 25.30 21.21 21.52 21.71 18.18 18.00 - - 4.301

Mg 26.49 26.24 24.64 24.37 23.39 23.81 19.25 11.33 11.16 - - 0.182

Mn .0137 .0345 .0324 .0286 .0141 .0087 .0239 .0112 .0083 0.1125 0.331 0.124

Mo .0055 .0047 - .0014 .0013 .0066 .0018 .0059 .0028 0.0295 0.009 0.038

Na 377.0 331.8 330.1 332.0 329.6 339.3 252.7 193.1 157.4 - - 102.5

S 193.1 123.4 123.8 124 123.8 121.4 46.65 26.74 25.13 376 378.95 0.240

Si 9.286 8.462 8.440 8.527 8.402 8.438 13.67 12.91 15.11 123.55 140.3 -

Zn .0368 .0525 .0557 .0641 .0475 .0530 .0638 .0695 .0591 0.028 0.074 0.013

From secondary treatment facilities, anaerobic digester and dairy lagoon (mg/L): sufficient

deficient

Wastewater Analysis—Macronutrients

Chandler AWRF

SampleAmmonia Nitrate

Phosp

hate

mg-N/L mg-N/L mg-P/L

Pretreatment 23.80 0.37 4.32

Beginning of Anoxic 2.97 0.34 10.20

End of Anoxic/beginning of

Nitrification0.18 0.92 5.90

End of Nitrification 0.05 0.99 3.12

Clarifier effluent 0.87 3.51 2.90

Plant effluent 1.85 4.15 3.31

San Tan (Village Ln)

SampleAmmonia Nitrate Phosphate

mg-N/L mg-N/L mg-P/L

Pretreatment 21.90 0.20 15.30

Begin oxic 5.73 1.97 7.41

End oxic 1.52 3.16 6.28

End of

anoxic0.00 0.26 10.50

Effluent 2.32 0.56 2.94

Pecan Creek

SampleAmmonia Nitrate Phosphate

mg-N/L mg-N/L mg-P/L

Pretreatment 34.70 0.28 12.40

Begin oxic 8.96 6.06 9.00

End oxic 2.00 8.08 7.96

End of

anoxic2.05 4.88 8.97

Effluent 2.13 3.00 2.71

Anthem

SampleAmmonia Nitrate Phosphate

mg-N/L mg-N/L mg-P/L

Pretreatment 12.00 0.61 5.55

Begin oxic 3.80 2.59 2.76

End oxic 0.45 4.28 2.63

End of

anoxic0.00 2.45 2.87

Effluent 0.00 3.41 0.06

Greenfield WRP & Van Rijn Dairy

Ammonia Nitrate Phosphate

mg-N/L mg-N/L mg-P/L

Centrate 500 0 4.05

Dairy 270 0 3.50

From secondary treatment facilities, anaerobic digester and dairy lagoon:sufficient

deficient

Turbidity of Wastewaters

• Causes– Particulates up to 1 mm in size

– Sand, silt, clay or organic matter

• Problems– Scatters light

– Decreases light penetration into culture

– Decreases DO by:• Increasing water temperature

• Decreasing Photosynthesis

• Measured by– NTU: Nephelometric Turbidity

Unit• Correlation to OD750 (Goodner,

2009.)

10/31/2014

Left to right: Settled dairy lagoon effluent,

anaerobic digester effluent, polymer treated

centrifuged centrate, BG-11 medium.

Reducing Wastewater Turbidity for Algae

Cultivation

• Dilution with less turbid waters

– Greenfield digester centrate diluted with final effluent

– 1:10 was equivalent to ¼ strength BG-11 as a

medium

Dairy Centrate Diluted

Dairy

Diluted

Centrate

Algae Growth in Wastewaters

• Diluted centrate had the highest nitrogen level and

had productivity similar to synthetic media

• Diluted dairy water had less nitrogen than centrate,

which reduced its productivity

• Municipal effluent performed poorly due to lack of

nitrogen

Biomass Composition

Centrate Dairy Effluent ¼ BG-11

Lipids 34.9% 39.4% 39.2% 34.4%

Protein 21.0% 17.4% 16.5% 24.0%

Ash 0.63% 0.75% 1.64% 1.77%

Centrate

Municipal

Effluent

Dairy

¼ BG-11

Another Option - Reduce Light Path (Thinner Reactor)

• Most photobioreactors on

AzCATI field site >4 cm

– New mini panels are 1.3 cm

– New micro panels are 0.7 cm

• Reducing light path:

– Increases cells light exposure

• Increases light-dark cycling

– Enables higher culture density

• >5% solids

– Enables record algal productivities

• +50 g/m2/day (Hu et al., 1998).

– Reduces effects of turbid

wastewater

4 cm light path

1.3 cm light path

• Culture Grown on BG-11 Medium shows growth response to a thinner light

path (preliminary data)

0

1

2

3

4

5

6

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00

Dry

Weig

ht

(g/L

)

Culture Period (days)

1.27 cm pathlength

3.8 cm pathlength

Growth Rate With Different Reactor Path Length

Wastewater Nitrogen

• Main source of nitrogen in dairy lagoon wastewater,

anaerobic digester centrate and municipal treatment

influent is ammonium

• The pKa of ammonia (NH3)/ammonium (NH4+) is

approximately 9.3

• Free ammonia present at higher pH values is toxic to

algae and becomes volatile

• Optimal pH Range 6.5 to 7.5

Optimum Range for

Growth on Ammonium

pH Scale

Algal Growth on Different Alkalinities• High alkalinity increases the pH above 8 with the

absence of excess CO2 at night causing volatility and

toxicity

Effect of Lack of Aeration at Night on pH

Culture prior to aeration in the

morning

Effects of Night Aeration on Growth in Centrate

Effect of Aeration on Biomass Yield/Composition

Culture After 11

Days - February

Aerated

2.5 g/L

~45% Lipid

Not Aerated At Night

2.25 g/L

~35% Lipid

Initial Culture

Aerated

0.4 g/L

Culture After 9

Days - April

Aerated

3.5 g/L

~48% Lipid

Not Aerated At Night

3 g/L

~35% Lipid

Summary

– US produces 32 BGD and AZ 600 MGD wastewater

– Wastewater treatment facilities:

• Are efficient in removal of nutrients from water. Sludge digestion may provide necessary nutrients

– Agricultural waste:

• Dairy effluent, among others, is a largely untapped source of digested nutrients

– Most wastewaters:

• Have micronutrients needed for algae cultivation

• May lack sufficient levels of inorganic carbon, nitrogen or phosphorous

• Have ammonia but volatilization/pH are issues

• Are turbid (dilution and reduced light path length are possible solutions)

– Algal growth on wastewaters is feasible, but depending on the source there are challenges that affect biomass yield and composition

Acknowledgements

• A special thanks to:

– Greenfield WRP

– Van Rijn Dairy

– Chandler AWRF

– Johnson Utilities

– Arizona Board of Regents

(RIF)

_

10/31/2014