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FOSNRS 2: Passive, 2-Stage BiofilterTreatment Systems for Reduction of Nitrogen from OWS – Pilot Study ResultsApril 7, 2014Josefin Hirst, P.E.

The Florida Onsite Sewage Nitrogen Reduction Strategies (FOSNRS) Project

SSSA Onsite Wastewater ConferenceApril 7-8, 2014

Hazen and Sawyer, P.C.

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Presentation overview

■ FOSNRS Task A: Nitrogen treatment and reduction options for Florida

■ Pilot test results■ Summary■ Questions and answers

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FOSNRS Task A: Nitrogen treatment and reduction options for Florida

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Review of biological nitrogen reduction for onsite wastewater treatment

Primary Treatment

Mineralization of organic Nto

ammonia (NH4)

Nitrification

Ammonia oxidized to nitrate (NO3)

by nitrifying bacteria, requires oxygen

Denitrification

Nitrate converted to N2 gas by denitrifying bacteria in

anoxic environment; requires supply of electron donor

Dispersal

Effluent discharge to thesoil or landscape for final treatment

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What are “Passive” nitrogen reduction systems (PNRS)?

■ Most current N-reducing onsite systems are mechanical treatment units, with pumps, blowers, controls

■ Passive definition for this project: Passive nitrogen reduction systems (PNRS) are OSTDS that reduce effluent N using reactive media for denitrification and a single liquid pump, if necessary.

■ Earlier work showed feasibility of bench-scale “passive” two stage biofiltration concepts (Smith et. al., 2008)

Treatment MediaEffluent TN

(mg/L)TN

Reduction (%)Zeolite & Sulfur Media 2.2 97Expanded Clay & Sulfur 2.6 96.2

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Task A was designed to further the concepts developed in previous work

■ Developed detailed performance data for passive biofiltration designs with various media configurations

■ Produced scalable design criteria from pilot scale biofilters for subsequent full-scale testing

■ Evaluated single pass and recirculating stage 1 biofilters

■ Evaluated twenty-two biofilters consisting of nine unsaturated Stage 1 biofilters, nine saturated Stage 2 biofilters, and four vertically stacked biofilter designs.

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A unique pilot facility was constructed at UF research center

■ University of Florida, Institute for Food & Agricultural Sciences (IFAS)

■ 475 acres of land in SE Hillsborough County

■ Facility conducts agricultural research & trials for vegetables, fruit and ornamental plants

■ Experts in soil and water science onsite

Source: http://gcrec.ifas.ufl.edu/

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Test facility included numerous treatment trains

■ All used two-stage biofilters:● Stage 1 Nitrification● Stage 2 Denitrification

■ Stage 1 unsaturated filters included 2 media layers and evaluated 15” and 30” media depths

■ We also evaluated single pass and recirculating stage 1 biofilters

■ For denitrification, we evaluated both lignocellulosic and sulfur denitrification biofilters

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Various nitrification media were studied

Zeo-Pure clinoptilolite Expanded polystyrene

Examples of Stage 1 Media

Expanded clayTorpedo sand

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Various denitrification media were also studied

Elemental Sulfur

Lignocellulosics

Examples of Stage 2 Media

Oyster shell (alkalinity amendment)

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PNRS test facility construction

Setting up tanks

Mixing Media Batches

Gravel Underdrain

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Placing media in tanks

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Two stage single pass biofilters

Stage 1 HLR 3 gal/d-ft2

Stage 2 HLR 5.6 gal/d-ft2

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We tested five trains of two-stage single pass treatment units

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Two-stage single pass biofilters

Stage 1 Unsaturated Biofilters - Nitrification

Stage 2 Saturated Upflow Biofilters - Denitrification

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Stage 1 recirculating biofilters schematic

Nitrified EffluentHolding Tank

Stage 1 HLR 3 gal/d-ft2

Recycle Ratio 3:1

Stage 1

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Horizontal stage 2 biofilters schematic

Peristaltic Pump

Sample Ports

Nitrified Effluent

Nitrified Effluent

Stage 2 HLR 10 gal/d-ft2

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Four recirculating stage 1 trains were followed by four stage 2 horizontal biofilters

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Stage 1 recirculating biofilters & Stage 2 horizontal saturated biofilters

Stage 2 Saturated Biofilters - Denitrification

Stage 1 Unsaturated Biofilters -Nitrification

Pump Tank

Nitrified Effluent

Pump Tank

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Pilot test results

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PNRS pilot testing influent STE quality

cBOD5 TSS TN TKN NH3‐NTotal 

Alkalinity

Septic ta

nk efflue

nt (STE) n 10 10 9 10 9 9

mean 66.8 90.9 55.5 55.8 46.3 332

std. dev. 27.0 136.1 19.9 18.8 19.1 87

min 22 15 30 30 20 210

max 94 467 80 80 67 430

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Stage 1 nitrification biofilters mean effluent values

Biofilter cBOD5 TSS TN TKN NH3‐N (NO3+NO2)

Single Pass

XCLAY – 15” 2.0 1.2 44.7 3.5 0.510 41.2

XCLAY – 30” 2.0 1.5 42.5 3.4 0.417 39.1

CLINO – 15” 2.0 2.2 41.0 3.1 0.012 37.9

CLINO – 30” 2.0 1.3 44.5 3.3 0.020 41.2

Recirculating

SAND – 30” 2.2 4.0 30.8 2.9 0.255 28.0

XCLAY – 30” 2.0 2.2 34.5 2.4 0.015 32.1

CLINO – 15” 2.2 2.3 35.3 2.6 0.010 32.7

CLINO – 30” 2.0 2.5 33.0 4.0 0.010 29.0

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Stage 1 single pass biofilters nitrogen time series

Single Pass Expanded Clay: 30 inch depth Single Pass Clinoptilolite: 30 inch depth

CLINO – 30”XCLAY – 30”

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Recirculating Expanded Clay: 30 inch depth

Stage 1 recirculating biofilters nitrogen time series

CLINO – 30”XCLAY – 30”

Recirculating Clinoptilolite: 30 inch depth

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UNSAT-EC1

UNSAT-EC3

UNSAT-CL1

UNSAT-CL3

UNSAT-CL5

UNSAT-SA2

UNSAT-EC4

UNSAT-CL2

UNSAT-CL4

Nitr

ate

& N

itrite

Nitr

ogen

, mg/

L

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

Quartiles: shaded boxMedian: solid lineMean: dotted line

_

_

UNSAT-EC1

UNSAT-EC3

UNSAT-CL1

UNSAT-CL3

UNSAT-CL5

UNSAT-SA2

UNSAT-EC4

UNSAT-CL2

UNSAT-CL4

Amm

onia

Nitr

ogen

, mg/

L

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

Quartiles: shaded boxMedian: solid lineMean: dotted line

_

_

Stage 1 nitrification biofilters effluentnitrogen box and whisker plots

Single Pass Recirculating Single Pass Recirculating

Am

mon

ia N

itrog

en, m

g N

/L

Nitr

ate

& N

itrite

Nitr

ogen

, mg

N/L

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Stage 2 denitrification biofilters mean effluent values

Biofilter C‐BOD5 TSS TN TKN NH3‐N (NO3+NO2)

Upflow

SULFUR‐30% 2.0 2.8 1.3 1.2 0.32 0.075

LIGNO‐50% 61.0 1.5 8.3 2.2 0.87 6.18

SULFUR‐80% 6.0 6.2 2.6 2.6 1.14 0.047

LIGNO‐25% 2.0 3.0 17.3 3.1 0.62 14.2

LIGNO‐30% 4.5 7.5 5.9 5.6 4.71 0.22

Horizon

tal

SULFUR‐80% 13.3 1.5 2.5 2.4 1.35 0.11

SULFUR‐30% 8.5 3.5 1.6 1.6 0.58 0.035

LIGNO‐50% 89.5 13.0 10.0 10.0 0.27 0.020

GLYCEROL 10 2.5 3.8 3.8 3.12 0.07

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Stage 2 upflow single pass biofilters nitrogen time series

SULFUR-80%LIGNO-50%

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Stage 2 horizontal biofilters nitrogen time series

SULFUR-80%LIGNO-50%

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DENIT-SU4

DENIT-LS3DENIT-S

U3DENIT-LS2DENIT-LS4DENIT-S

U1DENIT-S

U2DENIT-LS1DENIT-G

L1

Nitr

ate

& N

itrite

Nitr

ogen

, mg/

L

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

DENIT-SU4

DENIT-LS3DENIT-S

U3DENIT-LS2DENIT-LS4DENIT-S

U1DENIT-S

U2DENIT-LS1DENIT-G

L1

Tota

l Nitr

ogen

, mg/

L

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28Quartiles: shaded boxMedian: solid lineMean: dotted line

Stage 2 denitrification biofilters effluentnitrogen box and whisker plots

Mean = 14.2

Upflow HorizontalUpflow Horizontal

Nitr

ate

& N

itrite

Nitr

ogen

, mg

N/L

Tota

l Nitr

ogen

, mg

N/L

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Single pass systemstotal nitrogen removal

SULFURLIGNOCELLULOSIC

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Recirculating systemstotal nitrogen removal

SULFURLIGNOCELLULOSIC

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Vertical sampler profile in Upflow biofilterslignocellulosic issues

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Lignocellulosic biofilters hydraulic retention time issues

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Solute profile in sulfur upflow biofiltersulfate production vs nitrate reduction

0

100

200

300

400

500

600

700

01020304050607080

0 3 6 9 12 15 18 21 24

Sulfa

te, m

g/L

NOX‐N, m

g/L

Distance from Inlet, inches

SULFUR BIOFILTER

NOX‐N, DAY 107 NOX‐N, DAY 242 NOX‐N, DAY 305

SULFATE, DAY 107 SULFATE, DAY 242 SULFATE, DAY 305

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Single pass vs recirculating biofilters: sulfate

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Lessons learned from pilot test

■ Encouraging results from pilot PNRS; several system configurations capable of > 95% N reduction

■ Sulfate production vs nitrate reduction

■ Highly reactive elemental sulfur media

■ Lignocellulosic retention time issues

■ Recommended evaluation of combination lignocellulosic and elemental sulfur denitrification systems for full-scale treatment units

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Questions?Josefin Edeback-Hirst, P.E.Hazen and Sawyer, P.C.10002 Princess Palm Avenue, Suite 200Tampa, FL 33619jhirst@hazenandsawyer.com