2011 Excellence in Environmental Engineering and Science™ Competition Winner

E3S Grand Prize

2011 Grand Prize - Research

Patented & Innovative Cost-Saving Control Device for Facility-Generated Volatile Organic Compound (VOC) Emissions, Marathon Refinery

Entrant: ENVIRON International Corporation
Engineer in Charge: Dr. Carl E. Adams, Jr., P.E., BCEE
Location: Garyville, Louisiana
Media Contact: Brent M. Jones, P.E., BCEE, 713.470.6651

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Figure 1. MPC-Garyville Original BWON Plan (Activated Carbon) and Revised Implementation of Alternative Control Device

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Figure 2a. AIS Bioreactor Rendering

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Figure 2b. Schematic of AIS Flowpath

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Figure 3. Full-Scale AIS System at MPC-Garyville

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Figure 4. Benzene Mass Design Mass Balance

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Figure 5. Preliminary Modeling Results using Assumed Benzene Biodegradation Rates and Toxichem+


Entrant Profile

ENVIRON International Corporation (ENVIRON) was selected by the Marathon-Garyville Refinery (MPC) to develop protocols for certification of an innovative Alternative Control Device for benzene biodestruction, using the existing refinery activated sludge system (Figure 1) with features that qualify it as an Enhanced Biodegradation Unit (EBU). The project was part of the major facility expansion completed in 2009 increasing refining capacity from 185,000 to 370,000 bpd. The refinery's Wastewater Treatment Plant (WTP) capacity was increased from 2,100 to 3,300 gpm. This refinery complies with the 6 MG/yr Treat-to-Target Option under BWON (§342(e) (2)(i), which requires:

  • total benzene mass in all uncontrolled aqueous wastes less than 6 megagrams/year (MG/yr) benzene.
  • all organic emissions from wastewaters are controlled.
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MPC's NSR also requires less than 4.8 MG/yr uncontrolled benzene. ENVIRON's AIS (integrated bioreactor and clarifier--Figures 2A and 2B) was installed in 2005 to supplement existing external clarifier activated sludge trains. ENVIRON provided planning and design for the innovative BOX studies and field testing apparatuses successfully used in this project.

ENVIRON is an environmental consulting firm with more than 1,200 professionals in 71 offices across The Americas, Europe, Australia and the Asia-Pacific Region.

Other contributing author: Lial F. Tischler, Partner, Tischler/Kocurek.

Project Description

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MPC had already installed an activated carbon system for control of benzene and VOC emissions from the initial separation steps in the WTP. ENVIRON's wastewater engineers recommended a cost-effective alternative control scheme: biodestruction of these emissions in MPC's existing activated sludge system that will eliminate use of activated carbon for these WTP emission sources. Figure 1 illustrates MPC's carbon system and the proposed rerouting of the same emissions to ENVIRON's AIS (Figures 2A/2B) activated sludge system as the Alternative Control Device.

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The USEPA National Emission Standards for Hazardous Air Pollutants (NESHAP), specifically the BWON (Benzene Waste Operations NESHAP) regulations for refineries, require 98 percent benzene removal or 95 percent total VOC emissions reductions. Previous to this project, the only Control Technologies routinely acceptable to USEPA were Vapor Phase Adsorption (activated carbon) and thermal oxidation (incineration). Both of these technologies are capital and operationally expensive and generate significant carbon footprints. However, the BWON regulation allows for implementation of an Alternative Control Device, subject to 98 percent benzene (95 percent VOC) removal and specified operating and monitoring conditions.

ENVIRON reviewed the typical apparatus and procedures used to confirm acceptable biological destruction of VOCs, and decided to develop a more realistic and reliable procedure for the bench-scale BOX Test and field-scale simulation test. These innovative devices and procedures produced biodestruction rates more representative of full-scale conditions than the typical approach. This study resulted in modifying USEPA's published protocols and successfully obtaining their approval of data collection, testing methodology, and modeling techniques. The typically used and new ENVIRON-recommended BOX Test apparatus are shown in Figures 3A and 3B, respectively. ENVIRON's innovative protocols qualified MPC's existing activated sludge system as an Alternative Control Device for treatment of benzene emissions under the BWON rule.

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Integrated Approach

ENVIRON's innovative approach is an integrated solution that treats air emissions in an existing activated sludge aeration tank. This solution removes VOC vapor phase emissions from the air media by diffusing them directly into the existing aqueous phase activated sludge system, which is already acclimated to the organic compounds requiring treatment.

For this project, the use of existing ENVIRON-AIS to treat VOC emissions conserves energy by eliminating either fuel for thermal oxidizers or fuel to transport and regenerate spent carbon at an offsite carbon regeneration facility, depending on which technology is replaced. The solution also reduces land and space requirements for new equipment installations. Most significantly, an air pollution problem is integrated into a wastewater solution.

Quality

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After successful BOX testing, full-scale field testing is typically desired to verify performance before regulatory permitting and capital improvements like those recommended in this project are approved. ENVIRON designed an innovative External Core Column representing a "core sample" of the full-scale bioreactor approach in lieu of the Flux Chamber commonly used to evaluate VOC emissions from a full-scale, operating biosystem. ENVIRON's External Core Colum is the same operating depth and retention time as the full-scale bioreactor and is supplied with proper pumps, compressors, benzene calibration cylinders, etc. (See Figure 4.) The major advantage of the Core Column is that it is possible to control all operating parameters so that performance under maximum stress conditions can be evaluated. In contrast, the Flux chamber test can only assess biodegradation occurring under the operating conditions at the time of the test, and relies on the assumption that the emissions from the aeration tank are uniform across its entire surface area. The Core Column was developed and received acceptance from both USEPA and the State of Louisiana.

Originality and Innovation

This project represents the innovative approach of qualifying an existing activated sludge system both to treat aqueous-phase organic compounds and to serve as an Alternative Control Device for VOC vapor-phase emissions. Many attempts at implementing such an application have been reported, but never successfully demonstrated to regulatory agencies due to projected low VOC biodegradation rates. The protocols presented herein provide defensible biodegradation rates measured in tests that more closely simulate actual WTP operating conditions than the typical methods.

Complexity

In order to develop a site-specific Henry's Law coefficient and benzene biodegradation rate, the following conditions were met in the procedures specified by 40 CFR 63, Appendix C:

  • Biomass-free (filtered through 0.45 micron filter paper) AIS effluent was collected
  • Bioreactor MLVSS ⟩ 4 hours removed
  • Temperature maintained within 1 oC
  • Dissolved Oxygen ⟨ 2.0 mg/L

An enhanced BOX test apparatus was developed that simulated complete mixing of the biomass and an air-tobiomass sparging rate that is much closer to actual conditions than what is achieved in the aerator tube typically used. ENVIRON's enhanced BOX test study confirmed that benzene is stripped in 350 to 400 minutes in the absence of biomass and completely removed in 30 minutes with site-specific MLVSS.

In order to verify and implement the new protocols, several efforts must be precisely implemented and correlated with expert Toxchem+ modeling:

  1. Accurate benzene mass balance (Figure 5)
  2. Innovative assembly and utilization of BOX Test (Figures 3B and 6)
  3. On-line continuous benzene monitoring of BOX test off-gas (Figure 7A)
  4. Modeling of impact of significant operational parameters at determined benzene biodegradation rate (Figure 7B)
  5. Verification of accurate data fit to EPA criteria (Figure 8)
  6. Full-scale confirmation with Core Column Simulation (Figure 9 and Table 1)
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Social and Economic Advancement

The combined Social and Economic Advancement can be summarized in Tables 2 and 3. These are related to sustainability aspects and major reduction in the carbon footprint as a result of ENVIRON's alternative technology. ENVIRON's Core Column Testing solution can demonstrate that a facility's activated sludge system meets the regulatory definition of an EBU and Alternative Control Device and thus receive regulatory approval. Environmental and economic impacts can be proven each time any eligible WTP is converted to this new and innovative solution through significant reductions in both energy consumption and greenhouse gas emissions.

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Figure 6. Alternative Experimental Methods for Determining Fraction of Organic Biodegraded (Fbio) in a Biological Treatment Unit

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Figure 7. USEPA Recommended Box Test Apparatus (2-L Volume)

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Figure 8. Recommended Box Test Apparatus (57-L Volume)

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Figure 9. On-Line Photovac Voyager Gc

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Figure 10. Box Test Setup Recommended in Figure 8

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Figure 11. Combined Stripping and Biodegradation Benzene Emissions

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Figure 12. Smoothed Data Fit as per USEPA Criteria for Fbio Calculation

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Figure 13. Benzene Removal as Function of Biomass (Biodegradation Site-Specific Rate is Upper Curve - 22.6 L/G-Hr @ 20°C)

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Figure 14. Full-Scale Performance Test-Flux Chamber: Less Desirable Option

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Figure 15. Core Column Simulation Recommended by ENVIRON

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Figure 16. Photo of Core Column Simulation Setup in Field

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Figure 17. Benzene Analytical Results of Full-Scale Confirmation


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