(7a) 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).

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