Transcript Sherry Labs Tox Testing

Understanding Offshore Toxicity
Testing – Beyond “Pass” or “Fail”
Presented to:
Presented by: Kevin Dischler, Bioassay Lab Director
Topics to be covered….
Drilling fluids – WBM and SBM
Produced water
Subsea-chemicals
What are the limits?
What do they mean?
What makes a test “valid”?
How are results derived?
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Drilling Fluids – Toxicity Testing
 Aquatic Toxicity – LC50 with Mysids (WBM/SBM)
 Tests the affect of the mud on the water column
 LC50 = Lethal Concentration to 50% of the
exposed organisms
 Compliance target is an LC50 ≧ 30,000 ppm SPP.
 SPP = Suspended Particulate Phase of 1 part
mud to 9 parts seawater mixture
Drilling Fluid LC50 Test Set-up
 Control + 5 concentrations, 3 replicates, 20 shrimp
per replicate, randomly loaded
 Temp: 20±2ºC
 Salinity: 20±2 ppt
 14 hours of light, 10 hours of dark
 SPP created by mixing mud and saltwater
 pH is adjusted
 Test validity:
Control must have at least 90% survival @ 96- hours
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Aquatic LC50Toxicity Test
Determining the LC50
% SPP
Survivors (of 60)
Survival %
Control (0%)
59
98.3
20%
58
96.7
40%
54
90
60%
42
70
80%
24
40
100%
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18.3
LC50 of this data set is 72.8% or 728,000 ppm SPP
With the target being ≧30,000 ppm, this would be a Passing test
Why a second drilling fluid tox test?
Sediment Toxicity Test
 Measure the effect of the SBM
coated cuttings on the sea floor
 Uses Leptocheirus plumulosus
as the test organism
 Exposes the Leptos to a mixture of SBM and a
formulated (man-made) sediment
Sediment Toxicity Test Set-up
96-Hour tests are set-up with 5 concentrations and
a Control, 5 replicates, 20 Leptos per replicate
Tests are continuously aerated
Temp: 20±1ºC
Salinity: 20±1 ppt
Light cycle: 14 hours of light, 10 hours of dark
 Test validity:
Check #1- Controls must have at least 90% survival @
96-hours
Check #2 - Controls must have Coefficient of Variation
of <40%
Sediment Toxicity Test Set-up
With organisms from the same batch and
randomly loaded:
 A 96 Hour LC50 performed on the field sample
 A 96 Hour LC50 performed on the appropriate
reference mud:
- SBMs <11.0 ppg test with 9.0 ppg Ref Mud
- SBMs 11.0-14.0 ppg test with 11.5 ppg Ref Mud
- SBMs >14.0 ppg test vs. with 14.5 ppg Ref Mud
A SedTox test with a Ref Mud
- Randomly loaded organisms
- Randomly placed on the test shelves
The Sediment Toxicity Ratio (STR)
 The compliance limit for an STR is ≦ 1.0
LC50 Value for the Reference Drilling Fluid = STR
LC50 Value for the Submitted SBM sample
Ex: Ref MudLC50 =
42.9 ml/Kg
Field Mud LC50 = 197 ml/Kg
42.9 ÷ 197 = 0.2
Sediment Toxicity Ratio is 0.2 and is a Pass
But what if…..?
SedTox can be a difficult test. So much so, that
EPA allows it to be run three times.
 An STR of >1.0 on the first test is an “initial
failure.” Not out of compliance yet.
 Test 2 must be run from same sample, same
bottle.
 Test 3 must be run from a sample caught
within 15 minutes of the first sample
When averaging is needed, the LC50s are
averaged, not the STRs.
Produced Water Toxicity Test
 Chronic static renewal seven
(7) day survival and growth
test
 Measures the effect of
Produced Water on the
survival and growth of the test
organisms.
 The Vertebrate organism is a
Menidia beryllina
 The Invertebrate organism is
Mysidopsis bahia
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Produced Water Toxicity Test Set-up
 Mysid portion:
- 7 day old organisms
- Control + 5 concentrations, 8 replicates of 5 shrimp
- Temperature: 26±1ºC, Salinity: 25±2 ppt
 Menidia (minnow) portion:
- 7 to 11 day old organisms
- Control + 5 concentrations, 5 replicates of 8 fish
- Temperature: 25±1ºC, Salinity: 25±2 ppt
 Both require:
- 16 hours of light, 8 hours of dark
- 0.5 Dilution series – concentrations halve and double
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Produced Water Toxicity Test
 Randomly loaded organisms
 Randomly placed on test shelves
This is a “renewal” test.
Test water carefully
changed out daily,
survivors counted and
recorded daily.
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Looking for a “Passing” NOEC
 NOEC is No Observed Effect Concentration
 A NOEC for survival < Critical Dilution is considered a
lethal effect and requires re-testing
 A NOEC for growth < Critical Dilution is considered a
sub- lethal effect and requires re-testing
 NOEC > Critical Dilution required to pass
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What is a Critical Dilution?
 The Critical Dilution is determined by three factors used
in Table 1 Appendix D from the GMG Permit
- Highest dailly average flow rate for the previous
3 months prior to sampling
- Diameter of the discharge pipe
- Water depth from discharge pipe to seafloor
 What does the Critical Dilution represent?
The Cormix model tells us that at a point 100 m from
the outfall, a random sample pulled from the sea will
contain that same % of effluent from the outfall.
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Produced Water Toxicity Test
At test completion, survival
counts are recorded.
The surviving organisms are
dried overnight, cooled and
then weighed
Produced Water Toxicity Test Validity
Check #1: Controls must have a minimum of 80% survival @ 7 days
Check #2: Mysids in Control must average 0.20 mg
Check #3: Minnows in Control must average 0.50 mg
Check #4: Coefficient of Variation for the Controls must be <40%
Check #5: Unless significant effects are exhibited, the Coefficient of
Variation for Critical Dilutions must be <40%
Check #6: A Percent Minimum Significant Difference range of 11-37
for Mysid growth and 11-28 for Menidia growth shall be applied
accordingly.
 A test failure can not be deemed invalid due to a CV exceedence
DATA TABLE FOR Mysidopsis bahia SURVIVAL
Time of Reading
Control (0%)
0.04%
0.08%
0.16%
0.32%
0.64%
24 hours
97.5
97.5
100
100
97.5
100
48 hours
95
97.5
100
100
95
100
7 days
87.5
95
95
95
82.5
95
CV%
17.6
8.57
8.57
8.57
16.8
8.57
Time of Reading
Control (0%)
0.04%
0.08%
0.16%
0.32%
0.64%
24 hours
97.5
97.5
100
100
97.5
100
48 hours
90
90
100
90
87.5
80
7 days
77.5
85
87.5
72.5
65
55
CV%
17.6
8.57
8.57
16.6
16.8
8.57
DATA TABLE FOR Mysidopsis bahia GROWTH
%
0
0.04
0.08
0.16
0.32
0.64
%
0
0.04
0.08
0.16
0.32
0.64
A
0.770
0.727
0.794
0.808
0.659
0.491
Average dry weight (mg)
B
C
D
0.699
0.753
0.719
0.683
0.794
0.727
0.712
0.723
0.67
0.362
0.225
0.959
0.764
0.668
0.809
0.651
0.916
0.618
A
0.770
0.707
0.711
0.699
0.612
0.491
Average dry weight (mg)
B
C
D
0.699
0.753
0.719
0.683
0.651
0.615
0.715
0.695
0.654
0.689
0.691
0.651
0.595
0.562
0.511
0.412
0.395
0.396
E
0.649
0.716
0.716
0.912
0.651
0.747
Mean Dry
Wt.
0.718
0.729
0.723
0.653
0.710
0.685
CV%
6.6
5.5
6.2
51.5
10.1
24.8
E
0.649
0.695
0.671
0.689
0.503
0.405
Mean Dry
Wt.
0.718
0.670
0.689
0.684
0.557*
0.421*
CV%
6.6
5.5
6.2
15.5
10.1
24.8
Sub-sea Fluid Toxicity testing
 Examples: Sub-sea wellhead preservation fluids,
leak tracer fluids, umbilical storage fluids, riser
tensioner fluids, etc.
 The permit sets the limit or Critical Dilution at 50
mg/l
 Same method as Produced Water Toxicity Test
 Same organisms and test criteria
On December 16th, 2013
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“Partners in Compliance”
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