plastic medium bioreactors - pennsylvania state university

Penn State University

Pilot-scale Tests of Fixed Bed Reactors for Perchlorate

Degradation:Plastic Medium Bioreactors

Bruce Logan ([email protected]) & Booki MinDepartment of Civil & Environmental Engineering

Penn State UniversityPat Evans, Allyson Chu, CDM

mailto:[email protected]


Study Participants

• Site: Redlands, California, Texas St well field• Engineering Firm: Camp, Dresser and McKee,

Inc.• Research Unit: The Pennsylvania State

University• Funding Agency: American Water Works

Association Research Foundation (AWWARF; via an EPA Grant)


Plastic Medium Bioreactor

• System configuration• Performance during six-month field tests

in Redlands CA• Reactor scale up- effect of dispersion in

a packed bed reactor• Reactor performance compared with

other studies• Stability of the bacterium used for

inoculation


PSU-O4 Process Patent: Perchlorate degradation in a fixed bed bioreactor (U.S. Pat. No. 6214607)

Perchlorate respiringculture (optional)

Supplemental carbon source with(optional) N, P addition

Backwash withchlorate, N, P,acetate

Contaminatedwater source

Perchloratefree water

Sandfilter

ATTRIBUTES:Continuous perchlorate removalClogging avoided by intermittent backwashBiofilm regeneration by side process

Plastic media


Filter inlet controls mounted in storage tank

Ammonium phosphate feed

system

Acetic acid feed system


In line mixers, flow measurement, and flow controller

Flow measurement

Flow Controller

In line mixer


Plastic Media used in Reactor

Tri-Pack Plastic Media

(3.175 cm diameter)


Plastic medium bioreactor

Media is held in place by a perforated metal plate

Media floats in water, producing entrance region


Plastic medium bioreactor

During backwashing, media falls down, creating a mixing zone







inoculation


Groundwater Characteristics

Parameter Value Units

Perchlorate 50 – 120 ug/L

Nitrate 4 - 4.5 mg/L-N

Oxygen 8 – 10 mg/L

TCE 3 – 5 ug/L

1,1-DCE 1 – 2 ug/L


0

20

40

60

80

100

120

140

0 30 60 90 120 150 180Time (days)

Perc

hlor

ate

Con

cent

ratio

n (u

g/L)

0.34 0.68 0.34 0.51 0.68 0.34

Power outage

No AP and AA

No AA MDL = 4 ug/L

Startup

Perchlorate Removal: All Data


0

20

40

60

80

100

120

140

26 46 66 86 106 126 146 166 186

Time (Days)

Perc

hlor

ate

Con

cent

ratio

n (u

g/L)

-10

10

30

50

70

90

110

130

Per

chlo

rate

rem

oval

(%)

0.68 0.34 0.51 0.68 0.34

MDL=4ug/L

0.34

Perchlorate removal: Proper operationComplete removal

Gray circles indicate a backwash cycle


0

2

4

6

8

10

12

26 46 66 86 106 126 146 166 186Time (Days)

Nitr

ate

Con

cent

ratio

n (m

g/L)

0

20

40

60

80

100

120

Nitr

ate

Rem

oval

(%)

0.68 0.34 0.51 0.68 0.340.34

Nitrate Removal


Chemical Profiles in Reactor

0

10

20

30

40

50

60

70

0.1 0.3 0.5 0.7 0.9 1.1 1.3

Distance in Reactor (m)

ClO

4 (ug

/L),

Ace

tate

(mg/

L)

012345678910

DO

(mg/

L), N

O3 (

mg/

L)

PerchlorateAcetateNitrateOxygen

0

10

20

30

40

50

60

70

80

0.1 0.3 0.5 0.7 0.9 1.1 1.3Distance in Reactor (m)

ClO

4 (u

g/L)

, Ace

tate

(mg/

L)012345678910

DO

(mg/

L), N

O3

(mg/

L)

PerchlorateAcetateNitrateOxygen

0.68 L/m2s (day 162)0.34 L/m2s (day 127)

Perchlorate removed by 0.9 m(slightly over half way in the reactor)


Detention Time Measurements

350

370

390

410

430

450

470

490

0 20 40 60 80 100 120 140 160 180 200

Retention Time (min)

Con

duct

ivity

(uS

/cm

)

After Backwash

Before Backwash

0.34 L/m2s (day 172)

350

370

390

410

430

450

470

490

0 10 20 30 40 50 60 70 80 90 100

Retention Time (min)

Con

duct

ivity

(uS

/cm

) After Backwash

Before Backwash

0.68 L/m2s (day 166)

Before backwash: 32 min

After backwash: 37 min

Before backwash: 60 min

After backwash: 70 min


Acetic acid and Nutrients

Measurements Influent Effluent

Acetic acid (mg/L) 51 ±9 21 ±8 pH 6.72 ±0.12 6.80 ±0.19

Phosphate (mg/L) 12.8 ±3.6 12.1 ±2.6

DOC (mg/L)- g.w. 0.28 ----

- reactor 18 ±5 8.3 ±5.6

Turbidity (NTU) ---- 3.39 ± 3.75


Summary of Other Water Parameters

Measurements Influent Effluent

Temperature (ºC) 19.7 ±0.7 19.4 ±0.7

Conductivity (μS/cm) 394 ±9 378 ±36

Dissolved Oxygen (mg/L) 8.7 ±0.4 0.2 ±0.3 ORP (mV) 8 ±52 -85 ±77

Sulfate 33 ±2 ----

1,1-Dichloroethene (μg/L) 1.2 ±0.2* 1.3 ±0.2

Trichloroethene (μg/L) 3.7 ±0.5* 3.5 ±0.6

* Groundwater prior to amendments (data after day 26).







inoculation


Effect of Dispersion on Performance

• Dispersion results in some fraction of the material to be in the reactor less time: result is less treatment

• Importance of dispersion can be evaluated from the magnitude of the Peclet number (Pe)

• To calculate Pe, need to measure dispersion coefficient (E).

Concentration profile


E can be calculated from detention time (θ) measurements

2/1)4( θEw =

Before Backwash

350

370

390

410

430

450

470

490

0 20 40 60 80 100 120 140 160 180 200Retention Time (min)

Con

duct

ivity

(uS/

cm)

Before Backwash

0.34 L/m2s (day 172)

θ w

2/1)2(6 θEw =

The Dispersion coefficient is calculated as:

The Peclet number is calculated as:

θuLPe =

u= water velocity

L= length of column


Results of Peclet Number Calculations

• Dispersion is important when Pe<5.• In plastic medium reactor, Pe ranged from 16

to 44.• In sand reactor, Pe ranged from 22 to 140.• Based on these results, dispersion was not

important for overall rate of reaction (only critical factor was detention time).







inoculation

Sand media reactor Plastic media reactor

Which Fixed Bed Reactor is Better?


Backpressure measurements

0

20

40

60

80

100

120

140

160

180

26 46 66 86 106 126 146 166 186

Time (Days)

Back

pres

sure

(kPa

)

0.68 0.34 0.51 0.68 0.340.34

Average of 25±7 kPa


Backpressure: Plastic vs Sand

0

20

40

60

80

100

120

140

160

180

26 46 66 86 106 126 146 166 186

Time (Days)

Back

pres

sure

(kPa

)

0.68 0.34 0.51 0.68 0.340.34

0

10

20

30

40

50

60

70

80

90

100

20 40 60 80 100 120 140 160Time (Days)

Pre

ssur

e (k

Pa)

0.68 0.34 0.51 0.680.34

Sand mediaPlastic media




• Expect removal rate, R, is 1st-order with respect to perchlorate concentration.

• Rate calculated as:

• For 1st-order kinetics, use log mean perchlorate concentration

Reactor Kinetics: Removal Rates

θ−

=)CoutCin(R

)C/C(lnCCC

outin

outinlm

−=


y = 0.1169x0.8823

R2 = 0.8619

0.0001

0.001

0.01

0.1

1

10

100

1000

0.01 0.1 1 10 100 1000Perchlorate Concentration (mg/L)

Deg

rada

tion

rate

(mg/

L-m

in)

Rates in Plastic and Sand Medium Reactors vs Other studies

Plastic media (0.34 L/m2s)

Sand media (0.34 L/m2s)

Inorganic substrate

Other organic substrates


Recommendation: Plastic Media

• Plastic media has lower back pressure, and therefore lower operation costs

• Plastic media easier to backwash than sand media

• No loss of plastic media from reactor during backwashing

• Sand media has greater removal rate on a reactor-volume basis

• Given the above considerations, the plastic media is recommended for biological perchlorate degradation.







inoculation


Did Dechlorosoma sp. KJ survive?

• Reactor inoculated with a pure culture

• Other bacteria present in groundwater

• Sterile conditions not maintained

• Electron acceptors present in order: oxygen>nitrate>> perchlorate

Epifluorescent micrograph (1000 ×) of KJ stained with acridine orange


T1 T2 T3 M1

M2

M3

Top Middle

KJMW

std

s

1,353bp

1,078bp

872bp

1

42

3

1: uncultured Bacteroidetes2: uncultured bacteria3, 4: Dechloromonas sp. strain HZ

Perchlorate reducing microbial community profile (Preliminary Results)

What are the other prominent members of the microbial community?


Implications of community shift

• Isolate KJ removed perchlorate more efficiently than mixed cultures in laboratory studies

• Laboratory reactor with KJ had a minimum detention time of ~2 minutes (sand)

• Mixed culture required ~10 minutes in the laboratory for complete perchlorate removal

• Found in pilot-scale sand reactor a minimum detention time of ~10 minutes

• Community profiling indicates reactor became a mixed culture. This explains why 10 minutes was necessary for reactor design.


CONCLUSIONS

• Perchlorate (and nitrate) were completely removed in a plastic medium bioreactor at a hydraulic loading rate of 0.34 L/m2-s (0.5 gpm/ft2)

• Backwashing once a week was needed to prevent excessive biofilm buildup

• Perchlorate was removed at the same time as nitrate

• Community analysis indicates that the inoculated microbe was only a part of a diverse biofilm community that developed in the reactor.


ACKNOWLEDGMENTS

REFERENCESLogan, B.E. 2001. J. Environ. Engng. 127(5):469-471.

Logan, B.E., K. Kim and S. Price. 2001. In: Bioremediation of Inorganic Compounds, A. Leeson et al. eds. Battelle Press, Columbus, OH. 6(9):303-308.

Evans, P., A. Chu, S. Liao, S. Price. B. Min and B.E. Logan. 2002. Proc. Third International Conference on Remediation of Chlorinated and Recalcitrant Compounds, May 20-23, Monterey, CA. In press.

Min, B., P. Evans, A. Chu, and B.E. Logan. Perchlorate removal in a pilot plant-scale packed bed bioreactor- 2: Plastic medium bioreactor. Submitted.

City of Redlands Doug Hedricks, Dave Commons, Ken Pang

Camp, Dresser Pat Evans, Allyson Chu, Steven Price, Stephen Liao,

& McKee, Inc. Harold Pepple, Dick Corneille, Mike Zaefer

Students Booki Min, Yanguang Song, Husen Zhang,

Funding AWWARF: Project manager Frank Blaha

plastic medium bioreactors - pennsylvania state university

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