Montecito Sanitary District Ocean Outfall Study
Carter Ohlmann1, Trish Holden1, Libe Washburn1, Laurie Van De Werfhorst1,
Bram Sercu1, Cindy Wu2, and Gary Andersen2
1. Institute for Computational Earth System Science, University of California, Santa Barbara
2. Center for Environmental Biology, Lawrence Berkeley National Laboratory, Berkeley, CA
Acknowledgements. Funding for this project has come from the California State Water Resources
Control Board through the California Clean Beaches Initiative. This work would not have been possible
without the support and cooperation of Heal the Ocean and the Montecito Sanitary District.
Outline
• Background and motivation
• Experimental design, what was measured and why
• Data from a few specific days to illustrate the design
• Results:
- buoyant plume modeling
- surface current trajectories
- salinity signal
- microbiology of effluent
- microbiology following plume motion in the ocean
• Conclusions
Background
Historical AB411 beach water quality at
Hammonds Beach.
Does MSD effluent plume contribute to
poor water quality at Hammonds Beach?
Background
UCSB proposed a project with two primary goals:
Goal #1:
Observe pathways of a wastewater plume and plume composition along path.
Goal #2:
Determine if/how effluent plume contributes to poor water quality at shoreline.
Experimental design – monitor plume microbiology
from source to destination following plume motion
0 to 4 m3 sec-1
0 to 18 inches rain
1. Effluent sample and flow rate at source (MSD)
November 2007 through November 2008
Microbiological sampling for:
• FIB using IDEXX (total coliform, E. coli, enterococci; 50 sampling days)
• Nutrients (phosphate, nitrate+nitrite, ammonia; 50 sampling days)
• DNA using TRFLP (10’s of microbes; 26 sampling days)
• DNA using PhyloChip (1000’s of microbes; 8 sampling days)
2. Mooring at diffuser measures current and temperature profiles to
understand plume surfacing.
• mostly down-coast flow
• mostly very weak
offshore flow near
surface
• Temperature
stratification during
summer
• Mostly small short
period wind waves
3. Drifting buoys follow surface waters that emanate from a location above
the diffuser.
Microstar Drifters:
• tags water between ~0.5 and 1.5 m
• 10 minute position sampling w/ GPS
• 1 cm/s slip in 10 m/s wind
• 6 units deployed at diffuser each week
• 6 units deployed further offshore each week
• recovered when reach water depth of ~3 m
• direct measure of horizontal mixing
Ohlmann et al. 2005, and Ohlmann et al. 2007
4. CTD profiles and water samples following drifter motion to monitor
changes in plume salinity and microbiology.
Niskin bottle collects depth
integrated water sample
over top meter of ocean.
Conductivity, Temperature,
Depth (CTD) profiler to
identify fresh plume signal.
Observational Plan:
Weekly (once per week) sampling for 1 year off Santa Barbara (CA) coast.
coast line
shoreline and effluent microbiology
outfall
outfall plume
+
boat sampling
microbiology
and CTD
mooring measures
temp and currents
at diffuser
drifter releases
Observations of total coliform following drifter motion
14.5 in effluent
Diffuser
< 10 at all ocean samples
Total coliform from water samples collected on June 2, 2008
showing a weak signal from source to shoreline.
Observations of total coliform following drifter motion.
22.8 in effluent
87 at shoreline
Diffuser
< 10 for ocean samples except shoreline
Total coliform from water samples collected on April 7, 2008
showing a weak signal and disconnect with shoreline.
Observations of total coliform following drifter motion.
5.2 in effluent
369 at shoreline
Diffuser
following drifter motion
< 21 for ocean samples except shoreline
Total coliform from water samples collected on February 20, 2008
showing drifters do not move to the shoreline, but large shoreline value.
Observations of total coliform following drifter motion.
7.5 in effluent
Disconnect between
effluent (7) and ocean
water sampled above
diffuser (354).
573 at shoreline
Coliform source
presumably upstream of
diffuser as concentration
shows steady decrease
following drifter motion.
Jan 28, 2008 - large rain event
Sampling after large rain
event. These were max
concentrations observed.
Buoyant Plume Model to determine distance and time of
plume to surface.
Inputs: moored stratification and currents, effluent flow rate
• Distance from diffuser where plume reaches the surface is 59.56
ft, with a std of 13.855 ft (left)
• Time for plume to surface is 56.2 sec, with a std of 3.3 sec (right).
• Plume reaches surface in all realizations.
All drifter tracks starting at diffuser location
~3 km
Hammonds Beach
Starting location in green. Ending locations in red.
~300 tracks, hours in length. Few move to Hammonds Beach
Distribution of along coast location where drifters reach surf
zone within 3 hours of release from diffuser location.
-2 km
0
1 km
-2 km
0
1 km
- after 3 hours drifters reach the “surf zone” within ~1500 m alongshore
- after 3 hours there are more “surf zone” encounters upcoast
- bathymetry is relatively coarse for this application
Verify plume tracking with salinity from CTD casts
CTD casts following plume
1. S(offshore1000,1 m) = 33.82 ppt
2. S(diffuser,1 m) = 33.63 ppt
Presumed plume signal
3. S(Lagrangian1,1 m) = 33.70 ppt
Mixing w/ ocean increases S.
4. S(Lagrangian2,1 m) = 33.73 ppt
More mixing further increases S.
5. S(Lagrangian3,1 m) = 33.78 ppt
More mixing, greater S.
drifter tracks
and locations
of salinity data
Salinity Signal at Diffuser and Following Drifters
Salinity increases toward background value with mixing.
Water sampling for plume microbiology/chemistry
Water sampling following plume (w/ CTD casts)
Site 6 = Effluent
Multi-dimensional scaling
(MDS) plot of all samples
grouped by site from the
26 selected sampling
events for DNA-based
TRFLP analysis.
Effluent samples are variable in time and distinct from ocean samples.
E. coli summary statistics by location
Site 6 = Effluent
E. Coli summary statistics (MPN/100ml) by sampling location showing
values at shoreline are much larger than at other sampling locations.
Nutrient summary statistics by location
Phosphate (top) and Nitrate+Nitrite (bottom; μM) summary statistics by
sampling location showing large effluent values compared with ocean.
TRFLP DNA yield summary statistics by location
DNA yield (ng/l) summary statistics by sampling location showing values
at shoreline are larger than at other sampling locations.
PhyloChip Technology - The Berkeley Lab PhyloChip probes samples for the 16S
rRNA gene, which is involved in making proteins and is found in all bacteria. The
microarray quickly and accurately identifies known and unknown organisms. Unknown
organisms are classified based on their similarities to known microbes.
Multi-dimensional scaling (MDS) plot of PhyloChip results (8 days)
some samples are
distinct on rain day
1 = offshore
3 = diffuser
4 = drifters
5 = shoreline
6 = effluent
Effluent samples are variable in time and distinct from ocean samples.
PhyloChip analysis of water samples
collected above the diffuser (8 days)
no consistent ocean tracer
was found using PhyloChip
Number of microbial OTUs, families, and classes found with consistency.
The nearshore community varied considerably from week to week.
Lachnospiraceae OTUs distributions from PhyloChip analysis
offshore
effluent
diffuser
drifter track
drifter track
drifter track
shoreline
OTUs in the family Lachnospiraceae are consistently found in the effluent and
at the shoreline. No Lachnospiraceae OTUs are found at the offshore site.
Table shows Lachnospiraceae is most dominant taxa in human waste.
“sewage contained between 2000 and 3000 unique V6 sequences for the taxonomic
groups Bacteriodes, Lachnospiraceae, and Feacalibacterium (Table 3); however, fewer
than 20 unique V6 sequences accounted for the majority of tags for each of these
taxonomic groups.”
Conclusions
•Novel design for observing dilution and transport of a variety of plume tracers.
•Microbial communities within effluent are highly variable in time.
•Treated effluent reaches the surf zone along ~3 km span of shoreline directly
inshore of the diffuser with a dilution > 250.
•No apparent relationship exists between bacterial concentrations in the effluent
and sampled in ankle-deep water at the shoreline.
•Effluent fertilizes the near shore environment.
•The highly diverse set of OTUs distinguishable through PhyloChip analysis
provide an improved mechanism for identifying effluent.
•Lachnospiraceae OTUs are found in effluent, at the diffuser, following drifters,
and at the shoreline; but not beyond.