Acknowledgments:    Lucas  Lyerly,  Michael  Cline,  Steve  Carr,  &  Megan  Miller  (Coastal  Carolina  University,  Conway  SC)  North  Carolina  Department  of  TransportaEon  (NCDOT)      

Jeffrey  D.  Barley  &  Dr.  Susan  Libes  (Coastal  Carolina  University,  Conway  SC)  Ryan  Winston,  Bill  Hunt,  &  Shawn  Kennedy  (North  Carolina  State  University,  Raleigh  NC)  

Bacteria  Removal  Efficiency  of  a  Bioswale  located  in  Lockwood  Folly,  a  Coastal  Watershed  in  North  Carolina.  

0  

5000  

10000  

15000  

20000  

25000  

30000  

1SW   2UD   3OF  

MPN

/100mL  

Site  

Enterococci  faecalis  

Abstract:   Sites  &  Methods:  

Results:  

                 NC  Department  of  TransportaEon  (NCDOT)  has  obtained,   through  partnerships  with  private  sector,  an   engineered   soil   to   enhance   removal   of   fecal  bacteria  when  used  in  conjuncEon  with  stormwater  Best   Management   PracEces,   such   as   bio-­‐retenEon  cells.    The  efficacy  of  this  media  is  being  tested  at  a  site   in   Lockwood  Folly,  NC  where   a   TMDL   for   fecal  coliforms   was   approved   by   the   NC   Department   of  Natural   Resources   in   2010   to   address   shellfish  harvesEng   impairments   in   the   nearby   estuary.    Mechanisms  for  bacterial  removal  are  a\ributed  to:  (1)   retenEon  of  parEcles   to  which  microbes  adsorb  and   (2)   mortality   due   to   grazing   by   protozoans  harbored  by  the  soils.    Funding  is  being  provided  by  NC  DOT  as  part  of  a  program  to  evaluate  pollutant  removal  efficiencies  of  various  BMPs  for  road  runoff  treatment.       NCDOT’s   NPDES   permit   requires   the  retrofit  of  50  stormwater  BMPs  in  each  5  year  cycle;  they   opEmize   their   retrofits   through   results   of  research.  The  results  of  this  assessment  work  are  of  much   interest   to   South   Carolina   due   to   the   large  number   of   monitoring   sites   with   fecal   bacteria  impairments   that   are   located   in   seangs   similar   to  the   Lockwood   Folly   watershed,   the   relaEvely   low  cost   of   the   media,   and   the   opEon   of   retrofiang  exisEng  BMP’s  to  enhance  bacteria  removal.    

The  test  site  at  Lockwood  Folly  was  constructed  in  2012  by  installing  a  200-­‐c  linear  strip  of  media,  3-­‐c  deep  in  a  pre-­‐exisEng  stormwater  swale  that  runs  parallel  to  a  secondary  state  road  (NC  211)  maintained  by  NCDOT.    The  removal  efficiency  of  this  bioswale  is  being  evaluated  by  measuring  bacteria  transport  into  and  out  of  the  media  during  storm  events.    For  each  event,  flow-­‐weighted   samples   are   being   collected   at   the   inlet   and  outlet   of   the   bioswale   using   ISCO   auto-­‐samplers   oufi\ed  with  water   level   sensors.   The   samples   are  being   analyzed   for   two   fecal   indicator  bacteria   (Enterococcus   and   Fecal   coliform),   for  turbidity,  total  &  volaEle  suspended  solids,  and  conducEvity.    Sample  collecEon  and  processing  is  being  performed  by  Coastal  Carolina  University’s  Environmental  Quality  Laboratory.  

Discussion:  The  data  collected   to  date  have   shown   that  the   bio-­‐media   has   been   reducing   the  concentraEons  of  each  parameter  measured  with  the  excepEon  of  ConducEvity.      Enterococcus   faecalis   has   had   an   average  reducEon   of   about   3,000   Most   Probable  Number   per   100   mL   (MPN/100mL).     Fecal  coliform   has   had   an   average   reducEon   of  about    1,000  MPN/100mL.      TSS  has  been  reduced  by  about  30  mg/L,  VSS  by  about  10  mg/L  and  turbidity  by  about  10  NTU.      ConducEvity,   however,   has   shown   a   slight  increase,  averaging  about  5  µS/cm.      As   indicated   by   a   large   event   sampled   on  7/4/14  (Hurricane  Arthur:  Event  4),  high  flow  rates   may   reduce   or   even   reverse   the  effecEveness  of  the  media.    During  this  even,    the  flow  through  the  media  was  high  and  the  Enterococcus   faecalis   values   were   slightly  increased  acer  passage  through  the  media.  A  total  of  18  events  will  be  sampled  over  the  next   year.  Discharge   is   being  measured   and  will   be   used   to   infer   loadings   and   removal  efficiencies  of  the  bacteria  and  turbidity.      

Overall,  to  this  point,  the  bio-­‐media  has  been  performing  the  way  it  was  designed.    Bacteria  levels  and  suspended  solids  have  been  reduced  during  the  past  five  sampling  events.    Flow  rates  will  also  be  reviewed  in  the  future  to  determine  the  media’s  performance  during  different  types  and  strength  of  storm  events  and  strength  of  runoff.  If  the  bio-­‐media  conEnues  to  perform  as  designed  in  Lockwood  Folly  it  could  become  a  desirable  filtering  method  to  reduce  bacteria,  nutrients,  and  suspended  solids  from  storm  water  runoff  out  through  the  country.  

Summary:  

0  5  

10  15  20  25  30  35  

1SW   2UD   3OF  

NTU

 

Site  

Turbidity  

0  

1000  

2000  

3000  

4000  

5000  

6000  

1SW   2UD   3OF  

MPN

/100mL  

Site  

Fecal  coliform  

0  20  40  60  80  100  120  140  160  

1SW   2UD   3OF  

µS/cm  

Site  

Conduc@vity  

0  10  20  30  40  50  60  70  

1SW   2UD   3OF  

mg/L  

site  

Total  Suspended  Solids  

0  

5  

10  

15  

20  

25  

1SW   2UD   3OF  

mg/L  

Site  

Vola@le  Suspended  Solids  

The  Media:  The  Department  of  Biological  and  Agricultural  Engineering  at  NC  State  University  has  developed  a  “bouEque”  media  that  can  be  made  locally  from  easily  accessible  and  low-­‐cost  materials.  This  media,  combined  with  the  local  vegetated  landscape,  is  designed  to  naturally  reduce  and/or  remove  fecal  bacteria  and  parEculate  materials  from  stormwater  runoff.      

The  upstream  sampling  site  (1SW)  collects  stormwater  runoff  before  it  is  treated  by  the  bio-­‐media.  This  site  is  configured  to  pool  the  runoff  allowing  the    auto-­‐sampler  to  collect  water  before  it  moves  into  the  media.      

The  Overflow  (3OF)  sampling  site  is  designed  to  collect  any  water  runoff  that  flows  over  and/or  around  the  media.    CollecEon  is  based  on  a  volumetric  discharge  threshold.    

The  Underdrain  (2UD)  sampling  site  is  located    downstream  of  the  bio-­‐media.    CollecEon  is  based  on  a  volumetric  discharge  threshold.      The  sampling  site  is  covered  to  reduce  contaminaEon  from  direct  rain  or  sheet  flow  running  over  the  media.  

0.71  

1.34  

0.74  

2.73  

1.58  

0  

0.5  

1  

1.5  

2  

2.5  

3  

0  500  

1000  1500  2000  2500  3000  3500  

Event  1  (4/16/14)     Event  2  (6/21/14)   Event  3  (6/24/14)   Event  4  (7/4/14)   Event  5  (7/25/14)  

Inches  

MPN

/100mL  

Sampling  event  

Fecal  coliform  Swale   Under  Drain   Over  Flow   Rain  Fall  (inches)  

0.71  

1.34  

0.74  

2.73  

1.58  

0  

0.5  

1  

1.5  

2  

2.5  

3  

0.0  5.0  

10.0  15.0  20.0  25.0  30.0  35.0  

Event  1  (4/16/14)     Event  2  (6/21/14)   Event  3  (6/24/14)   Event  4  (7/4/14)   Event  5  (7/25/14)  

Inches  

NTU

 

Sampling  event  

Turbidity  Swale   Under  Drain   Over  Flow   Rain  Fall  (inches)  

0.71  

1.34  

0.74  

2.73  

1.58  

0  

0.5  

1  

1.5  

2  

2.5  

3  

0  

5000  

10000  

15000  

20000  

25000  

30000  

Event  1  (4/16/14)     Event  2  (6/21/14)   Event  3  (6/24/14)   Event  4  (7/4/14)   Event  5  (7/25/14)  

Inches  

MPN

/100mL  

Sampling  event  

Enterococcus  faecalis  Swale   Under  Drain   Over  Flow   Rain  Fall  (inches)