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00333: Impact Differentiation of Environmentally Friendly ... · PDF fileImpact Differentiation of Environmentally Friendly versus ... that determines plume dispersion ... work for

Aug 31, 2018

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  • Impact Differentiation of Environmentally Friendly versus Standard

    Corrosion Inhibitor Discharged into a Tropical Marine Environment

    James P Smith and Ian H Gilbert Dyno Oil Field Chemicals Asia Pacific

    43 Shipyard Road Singapore

    Jan Erik Solbakken Dyno Oil Field Chemicals Norway

    Edv. Griegvei 3A N-5037 Solheimvik

    Norway

    ABSTRACT

    A comparative ecotoxicology investigation has been conducted using field specific parameters to assess the impact of residual corrosion inhibitor, standard versus "green ", discharged from offshore facilities. Presented is a modeled estimate of ecological impact and risk associated with produced water / corrosion inhibitor mixtures from a low salinity-high temperature discharge of 142 million L/day into an open sea environment. Impact is assessed by extrapolation of steady state indicator test species LCso critical body residue (CBR) results applied to an accurate characterization of resident organism non steady state exposure and contaminant load. This extrapolation determines the acute and chronic impact of produced water / corrosion inhibitor mixture with time.

    These extrapolations are possible using an empirically justified predictive computer simulation of toxicant effluent mixture discharged into an open sea environment that determines plume dispersion, degradation, dilution, and bioaccumulation. The modeled simulation furnishes non steady state CBR bioaccumulation concentrations that provide an accurate representation of acute and chronic mortality with resultant PEC/NEC risk at any given geographical location adjacent to effluent discharge location.

    Key words; bioaccumulation, biodegradation, inhibitor, half life, risk assessment.

    Introduction

    E and P operations and specialty chemical suppliers spend a significant amount of money and energy complying with biodegradation testing requirements or regulatory specified toxicity tests. Once completed the test results are often applied to open sea dynamics or inland estuaries. Unfortunately, the results of these testing regimes are very seldom applicable to real world bio-dynamics occurring in either biosphere. This is substantiated

    Copyright @2000 by NACE International.Requests for permission to publish this manuscript in any form, in part or in whole must be in writing to NACE International, Conferences Division, P.O. Box 218340, Houston, Texas 77218-8340. The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association. Printed in U.S.A.

  • by the fact that in very few cases are surrogate species found in a sheltered environment or in continuous contact with representative toxicant materials for extended contact times, particularly, as biodegradation, sediment absorption and dispersion are not investigated in the specified test procedures.

    The premise of this document is to provide a verified alternative environmental assessment method with subsequent application to real world dynamics that considers all the factors of environmental availability that leads to biosphere disruption and impact brought about by specialty production chemicals. The process starts by determining the base toxicity of effluent water prior to the addition of chemicals. The comparative assessment of different specialty chemicals may then be conducted to provide predictive resultant impact, acute and chronic, and biosphere risk

    Discharged effluent water reviewed here are processed at one production and three satellite platforms and discharged from subsea outfalls at each platform at a combined rate of 242 million L/day, with the largest single discharge at 82 million liters per day. These effluent waters exhibit high temperature (90 C), brackish salinity (11 ppt), and contain residual hydrocarbon and man made chemical moieties including corrosion inhibitors.

    Studies have been conducted (1) on the fate and possible impact of production waters in an open sea environment by determining the physical dispersion of the effluent and its geochemical behavior. The geochemical dispersion model developed successfully simulates the chemical behavior of the produced water components by considering sediment-water partitioning, volatilization, biodegradation, and photodegradation. Laboratory experiments and field validation work for this outfall indicate that the majority of produced water components are rapidly volatilized, biodegraded, and mineralized (2). The molecularly large components are typically unaffected by the microorganisms, but often partition on to suspended solids resident in the receiving water.

    An important finding of simulation modeling is concentration "ponding" at sea [2] [3]. The "ponding" effect is thought to have important implications for chronic bio-impact because it represents a region of increased exposure concentration for extended periods.

    Finally, biodispersion modeling may then be applied to proven toxicology models that determine adverse effect and risk associated with mixed produced water~corrosion inhibitor discharge on adjacent biota. Where this site- specific modeling is complicated by marine diversity and species specific uptake mechanisms these factors have been investigated and field validated.

    Predictive Modeling Approach

    The CBR (critical body residue) approach applied in this study determines toxic response by exploiting concentration and uptake information to determine bioconcentration and toxic response. The most difficult task is relating body residue levels to concentrations known or suspected to cause an adverse response.

    The magnitude of biological response caused by toxicity in response to the quantity of exposure results in two basic assumptions;

    1). The concentration of a chemical at toxic response sites is proportional to exposure and concentration availability, and

    2). Once a threshold magnitude is exceeded the biological response elicited is proportional to the chemical concentration at the toxic response site.

    It is practically impossible to measure toxicant concentration at a response site, so surrogate measurements are applied, such as the concentration of the exposure medium. For example LCso water concentrations are often a surrogate for the toxicant at the response site of a given organism, [4]. There are limitations or short-comings to this approach. These include metabolic breakdown or activation, lipid content, temperature, and general biological factors such as species, sex, life stage, and season.

  • The comparison of LCso values with CBR does have several advantages. Those include: 1. Determination of explicit bio-availability, 2. Determination of accumulation kinetics versus exposure requirements, 3. Multiple chemical mixture assessment is easily conducted, and 4. Experimental verification is possible in the lab or field.

    Based on the data for CBR estimates for fish is] different modes of toxic action generally appear to be associated with differing ranges of body residues. This phenomenon is explained by noting when chemicals that act by specific modes of toxic action (i.e. non-narcotic) are present in a mixture below their threshold for toxic action they do not express a specific toxic action. They merely contribute to the narcotic activity of the mixture. In these circumstances, simple addition of the narcotic toxicity of the components of the mixture, rather than any interaction between specific modes of toxic action, produce biological response tel.

    Toxicity determination

    To ascertain toxicity of an effluent discharge regulatory bodies depend upon the use of surrogate indicator species toxicity tests, LCso or LD5o. These results are then extrapolated to field conditions and predictive impact imposed.

    The surrogate toxicity results determined for the discharge locations and applied to CBR modeling, reviewed here, are based on acute toxicity tests (ASTM Designation: E 1192-88) applied to mysid shrimp, Mysidopsis bahia and the silverside, Menidi beryllina using samples of fresh and the biodegraded produced water.

    The results of produced water toxicity presented in Table 1 indicate that acute toxicity effect appears to be consistent for both species. The degradation of the effluent water with resultant shift in chemical analyte concentration resulted in a shift in acute toxicity for effluent water tested.

    Important is the fact that degradation of chemical isomers often aid in the removal of toxic contaminants, but may result in the formation of metabolites which in themselves are often more toxic than the precursor compound' (7).

    Chemistry

    Connate water

    The fresh and biodegraded effluent water was tested for the presence of 113 EPA defined contaminants to correlate toxicity observed to chemical residual. The contaminants were categorized as monoaromatic hydrocarbons (VOC), Phenols, or Polycyclic Aromatic Hydrocarbons (PAH). A total of 76 compounds were identified. Of those 76 compounds, 24 comprise approximately 85 percent of the total concentration of contaminants identified, (Table 2)

    Specialty Chemicals

    In the work reported here corrosion inhibitors and other additives are added to the connate oil-water stream to solve problems encountered in the production process. Although many of these chemicals are oil soluble/water dispersible and remain with the oil following oil-water separation, some are sufficiently water-soluble that a fraction not partitioned in oil and water treatment remains with the produced water, is discharged, and becomes bioavailable.

    Only a few of the chemical additives applied in the system studied here are considered sufficiently water- soluble or dispersible to be discharged in produced water (Table 3). The percent d

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