Mississippi Administrative Code › Title 11 - Mississippi Department of Environmental Quality › Part 6 - Wastewater Pollution Control Regulations › Chapter 1 - Mississippi Commission on Environmental Quality National Pollutant Discharge Elimination System (NPDES) Permits, Underground Injection Control (UIC) Permits, State Permits, Water Quality Based Effluent Limitations and Water Quality Certification › Subchapter 2 - Water Quality Based Effluent Limitations › Exhibit 11-6-1-2-D to Chapter 1, Subchapters 1 and 2 - BIOASSAY REQUIREMENTS

Current through June 25, 2024
I. Chronic Bioassay Requirements
The Water Quality Standards of Mississippi require that
					 waters shall be free from substances attributable to municipal, industrial,
					 agricultural, or other discharges in concentrations or combinations that are
					 toxic or harmful to humans, animals, or aquatic life (State of Mississippi,
					 Water Quality Criteria for Intrastate, and Coastal Waters, Section II.4.,
					 Minimum Conditions Applicable to All Waters (current edition). In accordance
					 with such requirements, an NPDES permit holder is authorized to discharge from
					 outfall(s) only in accordance with the following conditions:
1. The permittee shall submit any existing
				  toxicity data for review by the Mississippi Office of Pollution Control within
				  30 days of the effective date of this permit.
2. The permittee shall perform 7-day chronic,
				  static renewal, definitive (a control and five effluent concentrations) WET
				  tests in accordance with
Short-Term Methods for Estimating the
				  Chronic Toxicity of Effluents and Receiving Waters to Fresh water
				  Organisms
, (EPA/600/489/001) or
Short-Term Methods for
				  Estimating the Chronic Toxicity of Effluents and Receiving Waters to Marine and
				  Estuarine Organisms
, (EPA/600/4-87/028) or the most recent
				  edition.
(a) Dilution water used for these
				  tests shall consist of reagent grade water, defined as distilled or deionized
				  water that does not contain substances which are toxic to the test organisms.
				  For freshwater tests, dilution water shall consist of reagent grade chemicals
				  or mineral water combined to make moderately hard dilution water according to
Short-Term Methods for Estimating the Chronic Toxicity of Effluents
				  and Receiving Waters to Freshwater Organisms
(EPA/600/4-89/001) or
				  most recent edition9. For estuarine testing,
				  dilution water shall consist of synthetic seawater or hyper-saline brine
				  combined to achieve a salinity of 20 parts per thousand according to Short-Term
				  Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters
				  to Marine and Estuarine Organisms (EPA/600/4-87/028) or most recent edition.
				  These dilution waters will be deemed acceptable if the control organisms in the
				  toxicity tests meet the minimum EPA criteria for chronic tests.
(b) If the Mississippi Office of Pollution
				  Control determines the receiving waters are freshwater, the permittee shall
				  conduct a
Ceriodaphnia dubia
Survival and Reproduction Test,
				  and a
Pimephales promelas
Larval Survival and Growth Test on
				  serial dilutions of effluent to determine if the discharge from outfall(s) is
				  chronically toxic. Such testing will determine if the water affects the
				  survival, growth, and reproduction of the test organisms. Static renewal tests
				  will be conducted on three 24- hour composite samples of effluent. The first of
				  these composite samples will be used to set up the tests and for the day 1 and
				  day 2 renewals, the second of these composite samples will be used to renew the
				  tests on days 3 and 4, and the third composite sample will be used to renew the
				  tests on days 5 and 6. Not more than 36 hours will elapse between sampling and
				  the first use of any of the composite samples. The chronic test(s) shall be
				  considered valid only if the acceptability criteria referenced in Short-Term
				  Methods for 
				  9 Contact MDEQ Office of Pollution
				  Control Laboratory for information on most recent editions(s) of methods manual
				  Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater
				  Organisms, (EPA/600/4-89/001), or the most recent edition, are met. All data
				  shall be statistically analyzed according to the referenced manual.
(c) If the Mississippi Office of Pollution
				  Control determines that the receiving water is estuarine, the permittee shall
				  conduct a
Menidia beryllina
Larval Survival and Growth Test
				  and a
Americamysis
Survival, Growth, and Fecundity Test on
				  serial dilutions of effluent to determine if the discharge from outfall(s) is
				  chronically toxic. Such testing will determine if the water affects the
				  survival, growth, and fecundity of the test organisms. Static renewal tests
				  will be conducted on three 24-hour composite samples of effluent. The first of
				  these composite samples will be used to set up the tests and for the day 1 and
				  day 2 renewals, the second of these composite samples will be used to renew the
				  tests on days 3 and 4, and the third composite sample will be used to renew the
				  tests on days 5 and 6. Not more than 36 hours will elapse between sampling and
				  the first use of any of the composite samples. The chronic test(s) shall be
				  considered valid only if the acceptability criteria referenced in
Short-Term Methods for Estimating the Chronic Toxicity of Effluents
				  and Receiving Waters to Marine and Estuarine Organisms
,
				  (EPA/600/487/028) or most recent edition are met. All test data shall be
				  statistically analyzed according to the referenced manual.
(d) A standard reference toxicant quality
				  assurance test (chronic) shall be conducted concurrently with the effluent
				  tests using both species used in the toxicity tests. Alternatively, if a lab
				  conducts monthly QA/QC reference toxicant tests with both species as part of
				  their SOP, these results may be submitted in lieu of the above mentioned
				  concurrent tests results. In either case, the reference toxicant test results
				  must be submitted with the final report as well as on the Mississippi Office of
				  Pollution Control NPDES Whole Effluent Toxicity Testing Report Form.
3. These chronic toxicity tests
				  shall be initiated within 90 days of the date of issuance of the permit to
				  evaluate wastewater toxicity. Such chronic toxicity tests shall be conducted
				  once per quarter for a period of one year following the effective date of the
				  permit. After the first year of monitoring, provided the
				  IC25 is greater than or equal to the IWC% the frequency
				  of monitoring will be reduced to once per six months for the life of the
				  permit. Sampling shall be timed to cover the seasonal extremes of the year
				  (hot-dry and cold-wet).
4. If any
				  one chronic toxicity test indicates the IC25 is less
				  than the IWC%, the provisions in Section 6 below shall apply, and the permittee
				  shall conduct another chronic toxicity test(s) with the organism(s) that
				  failed. This follow-up test must be completed within 30 days following
				  completion of the failed test. Final chronic toxicity test results shall be in
				  report form as outlined in Methods for Measuring the Acute Toxicity of
				  Effluents to Freshwater and Marine Organisms, Fourth Edition,
				  (EPA-600/4-90/027) or most recent edition. The permittee must also submit a
				  completed Mississippi Office of Pollution Control NPDES Whole Effluent Toxicity
				  Testing Report Form.
5. In the
				  event the permittee passes the additional WET test, the permittee shall resume
				  testing in accordance with the testing schedule set forth in the permit. In the
				  event the permittee fails the second WET test, the permittee shall submit a
				  Toxicity Reduction Evaluation Plan (TREP) within 45 days following completion
				  of the follow-up test in order to reduce the toxicity of the effluent to safe 
				  10
				  levels11. The first phase of the TREP will include
				  increased monitoring to characterize the toxicity of the effluent.
6. If the IC25 of any
				  test is less than the IWC%, then the effluent will be considered unacceptably
				  chronically toxic, and this will constitute a violation of Part I of this
				  permit.
7. In addition to the
				  specific conditions of this permit, the permittee shall comply with all
				  applicable conditions of
				  40 CFR
				  122.7 and
				  40
				  CFR 122.61 (06-03-93).