impact of wastewater treatment on phosphorus bioavailability pncwa...impact of wastewater treatment...

Impact of wastewater treatment on phosphorus

bioavailability: Spokane lake ecological context

Bo Li, Michael T. BrettDepartment of Civil and Environmental Engineering,

University of Washington, Seattle, Washington 98195, USA;

[email protected]

Eutrophication!!

EutrophicationEutrophicationNuisance cyanobacteria blooms & phytoplankton accumulations

Fish Kills

Toxins

Hypoxia

Operational Categories

Soluble PhosphorusSoluble Phosphorus

Particulate Phosphorus (PP)Particulate Phosphorus (PP)

Soluble Reactive Phosphorus (SRP)

Soluble non-Reactive Phosphorus

Particulate non-Reactive Phosphorus

Particulate Reactive Phosphorus

Operational Categories≠

Bioavailability

SRP = phosphate = 100% bioavailable ?

BAP• Bio-available Phosphorus• phosphorus that can be utilized by plants and

bacteria• %BAP reported from 5%-89%• Site specific

BAP% of TP in different P Source

Secondary

Effluent

Field

Runoff

Lake

bottom

Sediments

BAP%

Forest

Runoff

Tertiary

Effluent

SecondaryWith

Chem.treated

Effluent

?

Source: Petri Ekholm (2003), Determining algal‐available phosphorus of differing origin:routine

phosphorus analyses versus algal assays

Spokane Lake

Average total phosphorus concentrations data (n = 4) ±

standard deviation by RM for Ecology river surveys conducted on August 15-16 and September 26-27, 2000.

City of Spokane AWTP effluent impacts Spokane Lake

Solution?

Coagulation and flocculation• Chemical destabilization of colloidal surface charge • Addition of positively charged ions (eg. Al3+, Fe3+)

acts to neutralize surface charge of colloids • Colloids aggregate and form “flocs” .• “Flocs” will be removed by sedimentation or

filtration

-- --

--

AlAl3+3+

------

--

AlAl3+3+AlAl3+3+

AlAl3+3+

AlAl3+3+AlAl3+3+

Coagulation and flocculation

Effluent Phosphorus concentration Goal is based on Total P.

How does the BAP compare to Total Reactive Phosphorus (TRP)?Can TRP be used as a surrogate measure of BAP?

ObjectivesHow does %BAP vary with the level of P removal?Can TRP be a surrogate measurefor BAP?How does %BAP vary for effluents from other plants with different removal technologies?

• Study area

Spokane Lake

City of Spokane Pilot plant

Conventional SedimentationBallasted Sedimentation

Granular Media FiltrationUpflow sand filter Membrane Filtration

Sampling location• Plant A (Upflow sand filter, menbrane, MBR)

• Plant B (Upflow sand filter)

• Plant C (Biological Treatment)

• Plant D (Biological Treatment)

• Industrial Wastewater

Conventional

Sedimentation

Ballasted

Sedimentation

Conventional

Sedimentation

INF

S1E

C1E

S2E

Granular Media

Filtration

Upflow sand

filter

Membrane

Filtration

F2E

B2E

Z2E

F1E

B1E

Z1E

Pilot plant Sampling location

Granular Media

Filtration

Membrane

Filtration

Upflow sand

filter

Intermediate (INT) Effluent (EFFL)

Sampling (from August 2009 to April 2010)

Winter

• Summer Scenario:• 5 samples• with alum addition in

secondary WWTP

• Winter Scenario:• 3 samples• without alum addition

in secondary WWTPInfluent average TP

Summer

468µg/L

2753

µ g/L

Bioassay Method

Selenastrum capricornutum

125mL flask

Bioassay Method

50mL sample

Bioassay Method

0.2mL P-starved S. Cap (2.5*106cell/mL).

Bioassay Method

Bioassay Method

0.2mL P-starved S. Cap (2.5*106cell/mL).

Initial concentration:10,000 cells/mlIncubate for 14 days.

Bioassay Method

Culturing condition:1.Illumination:4300 lumens2.Temperature: 24 ±

2ºC

3. shake at 110 rpm.

Bioassay MethodTen

standards

containing between 0 and 50 μg P/L

Three

reps for each standard

Four reps for each sample

BAP Standard Curve

Cell density (cell/mL)

R2=0.99

BAP Standard Curve

BAP (µg/L)

Cell density (cell/mL)

Effect of incubation time and cell count - BAP relationship

Why does the bioassay require a 14 day incubation time?Because Standard Methods say so!!

Effect of incubation time and cell count - BAP relationship

Consequence: More work & Less data

QA/QC

TPConcentration Range (µg/L) 0—30 30—100 > 100

Mean Median Mean Median Mean Median

±SD (µg/L) 1.4 1 2.9 2.3 102.2 26.6CV (%) 8 5 6 7 4 3

TRPConcentration Range (µg/L) 0—30 30—100 > 100

Mean Median Mean Median Mean Median±SD (µg/L) 0.6 0.3 1.1 0.8 80 30.8

CV (%) 6 3 2 1 3 2

BAPConcentration Range (µg/L) 0—30 30—100 > 100

Mean Median Mean Median Mean Median±SD (µg/L) 0.8 0.4 10.4 5.6 188.8 119.0

CV (%) 19 13 16 9 11 9

BAP

QA/QC

Results

Ballasted

Sedimentation

Conventional

Sedimentation

Granular Media

Filtration

Upflow sand filter

InfluentSpokane River

Industrial

Wastewater

EffluentIntermediateInfluent

Winter Scenario

INF‐Inffluent INT‐Intermediate EFFL‐Effluent

Summer Scenario

INF‐Inffluent INT‐Intermediate EFFL‐Effluent

46

1

10

100

1,000

10,000

0 50 100 150 200 250 300

Total PTRPBAP

P c

once

ntr

atio

n, u

g/L

Alum Dose, mg/L

SecondaryEffluent

TertiaryFloc/Settling

Filtration

Effect of Chemical Dose and TertiaryTreatment on Effluent P Species

BAP% vs. TP in alum treatment process

0

20

40

60

80

100

Perc

ent B

AP

10100100010000Wastewater TP (µg L-1)

%BAP = -12.19*log (TP)2 + 92.03*log(TP) + 94.17; r2 = 0.98, n = 7, MSE = 10.3

BAP% vs. TP in alum treatment process

0

20

40

60

80

100

Perc

ent B

AP

10100100010000Wastewater TP (µg L-1)

Influent

Intermediate

Final Effluent

Influent

Intermediate

Final Effluent

%BAP = -12.19*log (TP)2 + 92.03*log(TP) + 94.17; r2 = 0.98, n = 7, MSE = 10.3

BAP vs TP and SRP?

Source: Petri Ekholm (2003), Determining algal‐available phosphorus of differing origin:routine

phosphorus analyses versus algal assays

BAP-TRP?BAP/TRP=0.44±0.40

Plant A

• Upflow sand filter, membrane, MBR

A2‐EA2‐E

A1‐IA1‐I

A2‐IA2‐I

A1‐EbA1‐Eb

A1‐EaA1‐Ea

A1-I -- Influent to upflow sand filter and membraneA1-Ea -- Effluent from Upflow filtrationA1-Eb -- Effluent from Membrane FilterA2-I -- Influent to MBR A2-E -- Effluent from MBR

Plant A – P removal performance

P co

ncen

tratio

n (µ

g*L-1

)

Plant B

• Upflow sand filter

B‐EB‐EB‐IB‐I

B-I -- Influent to upflow sand filterB-E -- Effluent from upflow filtration

Plant B – P removal performanceP

conc

entra

tion

(µg*

L-1)

Plant C

• Biological Treatment

C‐EC‐EC‐IC‐I

C-I -- Influent to biological treatmentC-E -- Effluent from biological treatment

Plant C – P removal performanceP

conc

entra

tion

(µg*

L-1)

Plant D

• Biological Treatment

D‐ED‐ED‐ID‐I

D-I -- Influent to biological treatmentD-E -- Effluent from biological treatment

Plant D – P removal performanceP

conc

entra

tion

(µg*

L-1)

Industrial Wastewater

P co

ncen

tratio

n (µ

g*L-1

)

IEP Sep. 10 Dec.3rdChl-a (µg/L) 1.06 1.6

Size (µm)

Cell c

ount

Size (µm)

Expected Industrial Wastewater

Cell c

ount

Industrial Wastewater

BAP vs. TRPBAP/TRP=0.54±0.22

BAP Chemical species

Conclusions

• BAP% is very low in City of Spokane pilot plant and goes down from the Influent (65%) to Intermediate (27%) to Effluent (4%).

• The %BAP vs. TP regression model we derived for the overall alum treatment process will provide an important baseline against which we can compare other processes.

• TRP may be used as a “conservative” measure of BAP.

Acknowledgement

• Washington State Department of Ecology, Spokane County, WA• City of Spokane, WA

• Liberty Lake Sewer and Water District, WA, • City of Post Falls, ID

• City of Coeur d’Alene, ID• Hayden Area Regional Sewer Board, ID

• Kaiser Aluminum• Inland Empire Paper Company

• Water Environment Research Foundation (WERF)

EffluentIntermediateInfluent

Questions?

0

20

40

60

80

100

Perc

ent B

AP

10100100010000

Wastewater TP (µg L -1)

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