Approved Alternative Control Device: VOC Biotreatment Technology

Approved Alternative Control Device: VOC Biotreatment Technology

 (As Required by NESHAPs [BWON, HON, MON, MACT]

 and Other Regulations) 

Dr. Carl E. Adams, Jr., PE, Senior Author/Presenter

Global Practice Area Leader: Industrial Wastewater Management,

ENVIRON International Corporation

Lial F. Tischler, Partner, Tischler/Kocurek, and

Andrew W. Edwards, PE, Principal, ENVIRON International Corporation

Need for Investigation

The USEPA National Emission Standards for Hazardous Air Pollutants (NESHAP) compliance regulations require 95 percent or greater removal of regulated Hazardous Air Pollutants (HAPs) in off-gas from storage vessels, process vents, and wastewater equipment. The BWON (Benzene Waste Operations NESHAP) regulations for refineries require 98 percent benzene removal or 95 percent total VOC removal.  Previous to the effort discussed herein, the only Control Technologies, typically acceptable to the USEPA, were Vapor Phase Adsorption and Thermal Incineration, including Flares.  Both control devices are capital and operationally expensive and generate high carbon footprints. 

However, the rule allows implementation of an Alternative Control Device, subject to 98 percent benzene (95 percent VOC) removal and specified operating and monitoring conditions.  This paper describes innovative protocols, developed by the authors and Marathon Petroleum Company (MPC) in Garyville, Louisiana, to certify that the activated sludge system was an Alternative Control Device that is cost-effective and has a minimal carbon footprint (Table 1).

Significance and Objectives of the Investigation

The major objective of the investigation was to develop bench-scale BOX Test and Core Column Simulation full-scale confirmation protocols and parameters, which delineate more realistic and reliable benzene biodegradation rates (f_bio) than the typical EPA methodology and default rates.  This effort has required modifying the recommended protocols and approach by the USEPA and obtaining their approval of data collection, testing methodology, and appropriate modeling techniques.  Modification of typical, conventional protocols for both the BOX Test and the full-scale confirmation negated the required use of VOC biodegradation rate default values.

This benzene-biodegradation system was approved in writing by the State of Louisiana and accepted by the USEPA - Research Triangle, North Carolina.  It is premised that any properly designed and operated activated sludge system can be qualified as an Alternative Control Device when developed with the protocols herein.  The new Alternative Control Device at MPC will be fully operational in February 2011.

Modeling Techniques

The development of site-specific predictive models for wastewater processes involves a choice of two models, i.e., USEPA's WATER 9 or Toxchem+™.  Toxchem+ is approved in 40 CFR Part 63 Appendix C and is preferred in the case of biodegradable VOC gaseous emissions for several reasons:

µ  The Toxchem+ model allows introduction of target pollutants in gas streams as well as in aqueous wastewaters.

µ  Toxchem+ assumes non-equilibrium conditions for vapor phase-liquid phase transfer.

µ  Benzene biodegradation rate is the most important element of model.

µ  Toxchem+ is very sensitive to modelers' expertise.

Findings of Investigation

The information provided herein summarizes the BOX Test and Full-Scale Confirmation testing objectives and achievement of benzene removal goals under maximum stress conditions.   The following information confirms compliance with 40 CFR µ 61.340:

• ENVIRON has developed bench-scale BOX Test batch and Core Column Simulation full-scale confirmation protocols and parameters, which delineate more realistic and reliable benzene biodegradation rates (f_bio) than the EPA default rates (Figures 1, 2, 3 & 4).
• The biorates, thus determined, are more representative of full-scale conditions than the typical USEPA approach.
• This effort has required modifying the typically recommended protocols and approach by the USEPA and obtaining their approval of data collection, testing methodology, and appropriate modeling techniques. 
• The approach, presented herein, is an environmental-friendly, sustainable VOC Control Device

–        Negligible additional energy usage

–        Minimal carbon footprint

• The site-specific benzene biodegradation rate is 29.3 L / g VSS-hr @ 26 ^oC (22.6 L/gm-hr, @ 20 ^oC). See Figure 4 for modeling results using developed f_bio.
• The activated sludge system configured herein provides excellent configuration and flexibility to achieve benzene removals >99+% even under benzene loadings >16 times projected operating design loadings(Table 2).

Table 1.  Comparative Costs  for Major VOC Control Devices at MPC-Garyville Refinery
Process Technology	Cost-Effective Impact
	Capital cost ($)	Annual Operating Cost ($)
Thermal Oxidizer	$800,000	$300,000
Granular Activated Carbon (6 carbon canisters on each of two API separators,22 change-outs/yr per API)	$240,000	$500,000
Biological (piping, fans and connection to blowers)	$400,000	Minimal

Figure 1.  Recommended Box Test Apparatus (57-L Volume)

                           

Figure 2.  Combined Stripping and Biodegradation Benzene Emissions

Figure 3.  Benzene Removal as Function of Biomass (Biodegradation

Site-Specific Rate is Upper Curve = 22.6 L / G-Hr @ 20 ^OC)

Figure 4.  Core Column Full-Scale Confirmation Evaluation

Table 2.  Benzene Analytical Results Of Full-Scale Confirmation
Parameter	Units		Run 1	Run 3		Run 4		Run 5
				A	B	A	B	A	B
Inlet Benzene Gas Concentration (Design = 14 ppbv)	ppbv		21	121	153	153	482	182	226
Outlet Off-Gas Benzene Concentration	ppbv		<2	<2	<2	<2	13.3	<2	<2
Percent Gaseous Benzene Removal	%		NA	>98.35	>98.69	>98.72	97.24	>98.80	>99.11
Influent Aqueous Benzene	μg/L		109	129	129	137	137	245	245
Effluent Aqueous Benzene	μg/L		<1	<1	<1	<1	<1	<1	<1
Percent Aqueous Benzene Removal	%		>99.09	>99.22	>99.22	>99.27	>99.27	>99.59	>99.59
Inlet Raw Wastewater Flow		gpm	0.21	0.21	0.21	0.21	0.21	0.35	0.35
Biomass Recycle from Clarifier		gpm	0.35	0.35	0.35	0.35	0.35	0.35	0.35
Internal Anoxic Recycle		gpm	0	0	0	1.1	1.1	1.1	1.1