Understanding Offshore Toxicity Testing – Beyond “Pass” or “Fail”
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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”?

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Understanding Offshore Toxicity Testing – Beyond “Pass” or “Fail”

Presented to:

Presented by: Kevin Dischler, Bioassay Lab Director


Topics to be covered
Topics to be covered…. “Pass” or “Fail”

  • 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?


Drilling fluids toxicity testing
Drilling Fluids – Toxicity Testing “Pass” or “Fail”

  • 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 lc 50 test set up
Drilling Fluid LC “Pass” or “Fail”50 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


Aquatic lc 50 toxicity test
Aquatic LC “Pass” or “Fail”50Toxicity Test


Determining the lc 50
Determining the “Pass” or “Fail”LC50

With the target being ≧30,000 ppm, this would be a Passing test


Why a second drilling fluid tox test
Why a second drilling fluid “Pass” or “Fail”tox test?


Sediment toxicity test
Sediment Toxicity Test “Pass” or “Fail”

  • 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
Sediment Toxicity Test Set-up “Pass” or “Fail”

  • 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 “Pass” or “Fail”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
A SedTox test with a Ref Mud “Pass” or “Fail”

- Randomly loaded organisms

- Randomly placed on the test shelves


The sediment toxicity ratio str
The Sediment Toxicity Ratio (STR) “Pass” or “Fail”

  • 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
But what if…..? “Pass” or “Fail”

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
Produced Water Toxicity Test “Pass” or “Fail”

  • 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 Menidiaberyllina

  • The Invertebrate organism is Mysidopsisbahia


Produced water toxicity test set up
Produced Water Toxicity Test Set-up “Pass” or “Fail”

  • 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


Produced water toxicity test1
Produced Water Toxicity Test “Pass” or “Fail”

  • Randomly loaded organisms

  • Randomly placed on test shelves

This is a “renewal” test. Test water carefully changed out daily, survivors counted and recorded daily.


Looking for a passing noec
Looking for a “Passing” NOEC “Pass” or “Fail”

  • 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


What is a critical dilution
What is a Critical Dilution? “Pass” or “Fail”

  • 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.


Produced water toxicity test2
Produced Water Toxicity Test “Pass” or “Fail”

  • At test completion, survival counts are recorded.

  • The surviving organisms are dried overnight, cooled and then weighed


Produced water toxicity test validity
Produced Water Toxicity Test Validity “Pass” or “Fail”

  • 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 “Pass” or “Fail”Mysidopsis bahia SURVIVAL


Data table for mysidopsis bahia growth
DATA TABLE FOR “Pass” or “Fail”Mysidopsis bahia GROWTH


Sub sea fluid toxicity testing
Sub-sea Fluid Toxicity testing “Pass” or “Fail”

  • 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


Partners in compliance

On December 16 “Pass” or “Fail”th, 2013

“Partners in Compliance”

>>>>>>>>>


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