“Biofiltration to Optimize Water Treatment”

•  NC AWWA WEA Spring Conference •  April 8, 2014

•  Peter C. D’Adamo, Ph.D., P.E. •  Chance Lauderdale, Ph.D., P.E.

•  HDR Engineering, Inc. of the Carolinas

Agenda  

•  Biofiltra/on  Basics  •  Biofiltra/on  Benefits  •  Biofiltra/on  Challenges  •  Nutrient  Enhanced  Biofiltra/on  •  Peroxide  Enhancement  •  Biofiltra/on  Cost  Benefits  

 

What  is  Biofiltra/on?  Conventional Filtration Biofiltration

What  is  Biofiltra/on?  Conventional Filtration Biofiltration

Biofiltra/on  is  Modified  Conven/onal  Granular  Media  Filtra/on  

Granular  Media  Filter  

Biofilter  

+ =

Chlorine

Enhanced  Organic  Removal  

Biofiltra/on  Improves  Finished  Water  Stability  

• Reduced  re-­‐growth  poten/al  

• Reduced  corrosion  poten/al  

• Reduced  taste  and  odor  

• Reduced  DBPs  • Improved  residual  

• Reduced  CECs  

Disinfec<on  Chlorine/  

Chloramines  

Filter  Influent  

8  

Biofiltra<on  

Chlorine  

Disinfec/on  

Effluent  

Floccula<on/Sedimenta<on   BW  

NaOH,  Ammonia  

Coagulant  

Polymer  

BWW  

Biofiltra/on  Replaces  Filtra/on    in  the  Process  Scheme    

Raw  Water  

Ozona<on  

Current  Biofilter  Opera/onal  Considera/ons  Focus  on  Several  Factors  

•  Temperature    •  Media  selec/on    •  Acclima/on  •  Hydraulic  loading  rate  •  Backwashing  strategy  

Temperature  Has  Minor  Effects  on  Performance  for  Steady  State  Filters    

•  Can  achieve  excellent  organics  removal  at  temperatures  even  <  5oC  

•  Recovery  periods  can  increase  with  decreasing  T  (rate  of  biogrowth)  

•  Impact  is  more  significant  if  chlorine  is  used  in  BW  water  •  Impact  is  less  significant  with  GAC  •  Poten/al  impact  on  trace  contaminant  removal  •  Longer  EBCTs  can  compensate  for  lower  Ts  

An  Acclima/on  Period  will  Always  be  Required  for  New  Biofilters  

•  ~20-­‐40  days  to  reach  steady-­‐state    •  GAC  may  decrease  startup  dura/on    •  Chlorine  increases  startup  dura/on    •  Restart  can  be  significantly  shorter  to  reach  steady  state  

Media  Selec/on  is  an  Important  Considera/on  for  Biofilter  Design  

•  Op/ons:  Sand,  Anthracite,  and  GAC  

•  GAC  maintains  higher  biomass,  provides  more  robust  performance  

 •  Organic/turbidity  removal  rates  similar  among  media  at  steady-­‐state  

•  GAC  benefits  should  be  balanced  against  cost  

The  Backwashing  Strategy  is  the  Most  Important  Opera/onal  Component  of  any  BAF  Process  

 •  Maintains  uniform  hydraulic  flow    •  Removes  par/cles,  excess  biomass    •  Low  chlorine  (<0.5  mg/L)  can  be  used  in  a  BW      •  Length  of  biological  filter  run  is  cri/cal  

 

Ozone  Increases  Biological  Ac/vity  by  Transforming  Complex  Organics  into  Degradable  Substrates      

Ozone

Non-Degradable Organics

Biodegradable Organics

Biofilters  Demonstrate  More  Robust  Aldehyde  Removal  to  Provide  Stability  

20  0  

10  

20  

30  

40  

50  

60  

70  

80  

90  

100  

9/29/2010   11/18/2010   1/7/2011   2/26/2011   4/17/2011   6/6/2011   7/26/2011   9/14/2011   11/3/2011  

Alde

hyde

s  (µg

/L)  

Influent  Abio/c  Filter  (No.  1)  Anthracite  Biofilter  (No.  6)  GAC  Biofilter  (No.  4)  

 

Over  Time,  Biofilter  Void  Space  becomes  Occupied  by  Par/culates  and  Biofilm  

Microbial Aggregates (loose biofilm)

Biofilm

Granular media

Particles

Excess  EPS  May  Cause    Media  Clogging  and  Underdrain  Failures  

Stripped  Anchors   Blown  Mas/c  

Clogged  IMS  Cap   Filter  Floor  Uplih  

Biofilm  is  Predominately  Extracellular  Polymeric  Substances  (EPS)  

Adhesion

Positive Impacts to Bacteria

Granular media

Protection

Negative Impacts to Biofilter

Granular media

Biofilm (EPS)

Biofilm (EPS)

Headloss

Clogging

EPS  Occupies  >1000x  More  Void  Space  than  Bacteria  in  Clogged  Biofilters  

 

Effec/ve  Biofiltra/on  Requires  a  Nutri/onal  Balance  

Nutrients    (P,  NH3)  

Biodegradable  Organic  Carbon  

Oxygen  

Intermediates,  Carbon  Dioxide,  Water  

EPS  

Secondary  Substrates/  Cometabolites                                                                (Mn,  EDCs,  Pes<cides,  T&O)  

Nutri/onal  Limita/ons  Create  Stressed  Biofilter  Condi/ons  

Nutrients    (P,  NH3)  

Biodegradable  Organic  Carbon  

Oxygen  

Intermediates,  Carbon  Dioxide,  Water  

X  EPS  

Implementa/on  of  Nutri/onal  Ra/o  Reduces  Biological  Stress  

Carbon                                                                  Nitrogen                                                            Phosphorus  

100  (1  mg/L)                                      10  (0.1  mg/L)                                              1  (0.03  mg/L)  

At  Arlington,  Nutrient  Enhancement  Decreased  Headloss  and  Increased  Filter  Run  Time  in  a  Pilot  Study  

0 1 2 3 4 5 6 7

0 2 4 6 8 10 12 14 16 18 20 Filter Run Time (hr)

Head-loss (ft) Phosp

horus-­‐Limited    

Biofilter  

Nutrient-­‐Enha

nced  

Biofilter  

15%  increase  in  filter  run  /me    

15%  decrease  in  terminal  headloss  

Loca/on:  Arlington  Filter  Run  Time:  18  hours  Loading  Rate:  4  gpm/h2  

Arlington  Pilot  Data  has  Translated  to  Full-­‐scale  Performance…..  

30  0  

2  

4  

6  

8  

10  

12  

14  

4/12/2012   4/13/2012   4/14/2012   4/15/2012   4/16/2012   4/17/2012  

Head

loss  (V

)  

Date  

Filter  6  -­‐  Phosphorous  Enhancement  

Filter  16  -­‐  Control  (No  Enhancement)  

Filter  20  -­‐  Control  (No  Enhancement)  

 

But we don’t get the benefits of biofiltration if we use chlorine!

What  About  Headloss  and  Clogging  from  EPS?  

32  

Chlorine

Clogged Biofilter

Inactivates (Kills) most Bacteria

Minimizes EPS Production (minimal EPS removal)

Unclogged Biofilter

Bacteria survive

How can we mitigate EPS???

Chlorine ?

Microbial  Enzymes  Mediate  Reduc/on  Of  Peroxide…….  

Granular media

enzyme enzyme enzyme enzyme

enzyme enzyme

H2O2

As  Peroxide  is  Reduced  EPS  and  Other  Organics  are  Oxidized  

Granular media

H2O + O2

Hydrogen  Peroxide  Addi/on  Reduces  Headloss  Significantly  

0  

1  

2  

3  

4  

5  

6  

7  

8  

9  

10  

9/28/2009  9/29/2009  9/30/2009  10/1/2009  10/2/2009  10/3/2009  10/4/2009  10/5/2009  10/6/2009  10/7/2009  

Date  

1 mg/L Supplemental Hydrogen Peroxide (No Phosphorus)

Loading Rate: 4 gpm/sq.ft. Run time: 18 hours Dose: 1 mg/L

Head-loss (ft)

 

37  

Biofiltration

Chlorine

Disinfection/UV

Effluent

Flocculation/Sedimentation BW

NaOH, Ammonia Coagulant

Polymer

BWW

Biofiltra<on  may  yield  cost  savings  and  water  quality  benefits  across  mul<ple  processes    

Raw Water

Ozonation

38  

Biofiltration

Chlorine

Disinfection/UV

Effluent

Flocculation/Sedimentation BW

NaOH, Ammonia Coagulant

Polymer

BWW

Raw Water

Ozonation

Improved  taste  and  odor  removal  may  reduce  ozone  requirements  to  CT  levels  

Savings  of  >$60/mg/MG  Treated  for  Arlington  and  Dallas  

39  

Biofiltration

Chlorine

Disinfection/UV

Effluent

Flocculation/Sedimentation BW

NaOH, Ammonia Coagulant

Polymer

BWW

Raw Water

Ozonation

Improved  organics  removal  may  reduce  coagulant  dosage  requirements  to  meet  TOC  goals  

Savings  of  ~$100/MG  Treated  for  Dallas  (30  mg/L  Ferric  Sulfate  reducCon)  

40  

Biofiltration

Chlorine

Disinfection/UV

Effluent

Flocculation/Sedimentation BW

NaOH, Ammonia Coagulant

Polymer

BWW

Raw Water

Ozonation

Improved  filter  hydraulics  decreases  backwash  cost  

Savings  of  ~$2/MG  Treated  for  Arlington  

41  

Biofiltration

Chlorine

Disinfection/UV

Effluent

Flocculation/Sedimentation BW

NaOH, Ammonia Coagulant

Polymer

BWW

Raw Water

Ozonation

Controlled/Mi<gated  fouling  may  preserve  filter  mechanical  equipment  and  underdrains  

>$100,000  per  replaced  underdrain  

42  

Biofiltration

Chlorine

Disinfection/UV

Effluent

Flocculation/Sedimentation BW

NaOH, Ammonia Coagulant

Polymer

BWW

Raw Water

Ozonation

Improving  water  treatment  performance  may  delay/eliminate  media  change  out  requirements  

>$4,000,000  for  Dallas  Bachman  WTP  >$250,000/yr  for  Peoria  Greenway  WTP  

Questions? •  pdadamo@hdrinc.com  

•  919-­‐232-­‐6610