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<u>'''Large-scale trickle filters for wastewater treatment'''</u>
[[Image:AirPollutionSource.jpg|thumb|right|155px|An air pollution source]]
The '''AP 42 Compilation of Air Pollutant Emission Factors''', was first published by the U.S. Public Health Service in 1968. In 1972, it was revised and issued as the second edition by the U.S. Environmental Protection Agency (EPA). In 1985, the subsequent fourth edition was split into two volumes. Volume I includes stationary [[Air pollution dispersion terminology|point and area source]] [[emission factor]]s, and Volume II includes [[Air pollution dispersion terminology|mobile source]] emission factors. Volume I is currently in its fifth edition and is available on the Internet.<ref>[http://www.epa.gov/ttn/chief/ap42/index.html AP 42, Volume I]
</ref> Volume II is no longer maintained as such, but [[roadway air dispersion model]]s for estimating emissions from onroad vehicles and from non-road vehicles and mobile equipment are also available on the Internet.<ref>[http://www.epa.gov/otaq/models.htm Mobile source emission models]</ref>


[[Image:Christchurch Trickling Filters.jpg|right|thumb|250px|{{#ifexist:Template:Christchurch Trickling Filters.jpg/credit|{{Christchurch Trickling Filters.jpg/credit}}<br/>|}}Figure 1: Trickle filters in water and waste treatment unit, Christchurch City Council, New Zealand]]
In routine common usage, Volume I of the emission factor compilation is very often referred to as simply AP 42.


A '''trickle filter''' consists of a fixed bed of [[Rock (geology)|rock]]s, [[gravel]], [[slag]], [[polyurethane|polyurethane foam]] or plastic media over which [[sewage]] or other [[biodegradable]] [[wastewater]] percolates downward and is contacted with a layer or film of [[Microbe|microbial]] slime covering the bed media. [[Aerobic]] conditions are maintained by air flowing through the bed.<ref name=Mara>{{cite book|author=Duncan Mara and Nigel J. Horan (Editors)|title=Handbook of Water and Wastewater Microbiology|edition=1st Edition|publisher=Academic Press|year=2003|id=ISBN 0-12-470100-0}}</ref><ref name=Sperling>{{cite book|author=Marcos Von Sperling| title=Activated Sludge and Aerobic Biofilm Reactors|edition=1st Edition|publisher=IWA Publishing|year=2007|id=ISBN 1-84339-165-1}}</ref><ref name=Bishop>{{cite book|author=Paul L. Bishop|title=Pollution Prevention: Fundamentals and Practice|edition=|publisher=Waveland Press|year=2004|id=ISBN 1-57766-348-9}} [http://www.eng.uc.edu/~pbishop/pollution.htm Lecture on Chapter 11: Residuals Management]</ref><ref name=Beychok>{{cite book|author=Milton R. Beychok|title=[[Aqueous Wastes from Petroleum and Petrochemical Plants]]|edition=1st Edition|publisher=John Wiley and Sons|year=1967|id=[[Library of Congress Control Number|LCCN]] 67019834}}</ref><ref name=Primer>[http://www.epa.gov/owm/primer.pdf Primer for Municipal Wastewater Treatment Systems]</ref>
==Introduction==


The terms ''trickling biofilter'', ''biofilter'', ''biofilm reactor'', ''biological filter'', ''biological trickling filter'' and ''biotower'' are often used to refer to a trickle filter. These systems have also been described as an attached growth process
Air [[pollutant]] emission factors are representative values that attempts to relate the quantity of a pollutant released to the ambient air with an activity associated with the release of that pollutant. These factors are usually expressed as the weight of pollutant divided by a unit weight, volume, distance, or duration of the activity emitting the pollutant (e.g., kilograms of particulate emitted per megagram of coal burned). Such factors facilitate estimation of emissions from various sources of [[air pollution]]. In most cases, these factors are simply averages of all available data of acceptable quality, and are generally assumed to be representative of long-term averages.  
, a fixed film process, packed media bed filters and percolating filters.


==Process mechanism==
The equation for the estimation of emissions before [[Air pollution#Control Devices|emission reduction controls]] are applied is:


Referring to Figure 2, the process mechanism involves [[adsorption]] of any [[Organic chemistry|organic compounds]] in the sewage or other wastewater by the layer of microbial slime followed by the diffusion of air into the slime layer to furnish the [[oxygen]] (O<sub>2</sub>) required for the [[Biochemistry|biochemical]] [[oxidation]] of the organic compounds that results in releasing gaseous [[carbon dioxide]] (CO<sub>2</sub>), water (H<sub>2</sub>O) and other oxidized by-products.<ref name=Mara/><ref name=Bishop/><ref name=Beychok/> The air may be provided by [[Flue gas stack#flue gas stack draft (draught)|natural draft]] or by forced aeration using large fans or blowers.
:'''E = A × EF'''


The aerobic biochemical oxidation occurring in a trickle filter may be expressed as:
and for emissions after reduction controls are applied:


:'''Organic compounds + microbes + nutrient + O<sub>2</sub> → oxidized organics + CO<sub>2</sub> gas + H<sub>2</sub>O'''
:'''E = A × EF × (1-ER/100)'''


[[Image:Trickle Filter Cross-section.png|right|thumb|250px|{{#ifexist:Template:Trickle Filter Cross-section.png/credit|{{Trickle Filter Cross-section.png/credit}}<br/>|}}Figure 2: A schematic cross-section of the contact face of the bed media in a trickle filter.]]  
{| border="0" cellpadding="2"
|-
|align=right|where:
|&nbsp;
|-
!align=right| ''E''
|align=left|= emissions, in units of pollutant per unit of time
|-
!align=right| ''A''
|align=left|= activity rate, in units of weight, volume, distance or duration per unit of time
|-
!align=right| ''EF ''
|align=left|= emission factor, in units of pollutant per unit of weight, volume, distance or duration)
|-
!align=right| ''ER''
|align=left|= overall emission reduction efficiency, in %
|}
Emission factors are used by [[atmospheric dispersion modeling|atmospheric dispersion modelers]] and others to determine the amount of air pollutants being emitted from sources within industrial facilities.


As the slime layer thickens, it becomes more difficult for air to penetrate the layer and an inner [[anaerobic]] layer is formed. For some plastic media , this inner layer will build up and eventually slough off the smooth plastic into the treated [[effluent]] water as a sludge that requires subsequent removal and disposal. The sludge consists of dead microbes, non-gaseous oxidized materials, [[Inorganic chemistry|inorganic minerals]] which are not biodegradable and other substances.
==Chapters in AP 42, Volume I, Fifth Edition==


Other than the primary carbon dioxide, water and sludge by-products of the biochemical processes occurring in a trickle filter, there may also be some by-product [[nitrogen]] (N<sub>2</sub>) and [[methane]] (CH<sub>4</sub>) gases.
{| border="0" cellpadding="2"
|-
|align=left|Chapter 1
!align=left| &nbsp; &nbsp; &nbsp;External Combustion Sources
|-
|align=left|Chapter 2
!align=left| &nbsp; &nbsp; &nbsp;Solid Waste Disposal
|-
|align=left|Chapter 3
!align=left| &nbsp; &nbsp; &nbsp;Stationary Internal Combustion Sources
|-
|align=left|Chapter 4
!align=left| &nbsp; &nbsp; &nbsp;Evaporation Loss Sources
|-
|align=left|Chapter 5
!align=left| &nbsp; &nbsp; &nbsp;Petroleum Industry
|-
|align=left|Chapter 6
!align=left| &nbsp; &nbsp; &nbsp;Organic Chemical Process Industry
|-
|align=left|Chapter 7
!align=left| &nbsp; &nbsp; &nbsp;Liquid Storage Tanks
|-
|align=left|Chapter 8
!align=left| &nbsp; &nbsp; &nbsp;Inorganic Chemical Industry
|-
|align=left|Chapter 9
!align=left| &nbsp; &nbsp; &nbsp;Food and Agricultural Industries
|-
|align=left|Chapter 10
!align=left| &nbsp; &nbsp; &nbsp;Wood Products Industry
|-
|align=left|Chapter 11
!align=left| &nbsp; &nbsp; &nbsp;Mineral Products Industry
|-
|align=left|Chapter 12
!align=left| &nbsp; &nbsp; &nbsp;Metallurgical Industry
|-
|align=left|Chapter 13
!align=left| &nbsp; &nbsp; &nbsp;Miscellaneous Sources
|-
|align=left|Chapter 14
!align=left| &nbsp; &nbsp; &nbsp;Greenhouse Gas Biogenic Sources
|-
|align=left|Chapter 15
!align=left| &nbsp; &nbsp; &nbsp;Ordnance Detonation
|-
|align=left|Appendix A
!align=left| &nbsp; &nbsp; &nbsp;Miscellaneous Data & Conversion Factors
|-
|align=left|Appendix B.1<br>&nbsp;
!align=left| &nbsp; &nbsp; &nbsp;Particle Size Distribution Data and Sized Emission Factors <br> &nbsp; &nbsp; &nbsp;for Selected Sources
|-
|align=left|Appendix B.2
!align=left| &nbsp; &nbsp; &nbsp;Generalized Particle Size Distributions
|-
|align=left|Appendix C.1
!align=left| &nbsp; &nbsp; &nbsp;Procedures for Sampling Surface/Bulk Dust Loading
|-
|align=left|Appendix C.2<br>&nbsp;
!align=left| &nbsp; &nbsp; &nbsp;Procedures for Laboratory Analysis of Surface/Bulk Dust<br> &nbsp; &nbsp; &nbsp;Loading Samples
|}


The following conditions result in the sloughing off of part of the microbial slime layer (referred to as the ''biofilm'') and are  intentionally or unintentionally used for control of the biofilm:<ref name=Mara/>
Chapter 5, Section 5.1 "Petroleum Refining" discusses the air pollutant emissions from the equipment in the various refinery processing units as well as from the auxiliary steam-generating boilers, furnaces and engines, and Table 5.1.1 includes the pertinent emission factors. Table 5.1.2 includes the emission factors for the fugitive air pollutant emissions from the large wet [[cooling tower]]s in [[Oil refinery|refineries]] and from the oil/water separators used in treating refinery [[wastewater]].


*Hydraulic erosion by the continuous flow of water across the surface of the biofilm
The fugitive air pollutant emission factors from [[safety valve|relief valves]], piping [[valves]], open-ended piping lines or drains, piping [[flange]]s,  sample connections, and [[mechanical seal|seals]] on [[pump]] and [[Gas compressor|compressor]] shafts are discussed and included the report EPA-458/R-95-017, "Protocol for Equipment Leak Emission Estimates" which is included in the Chapter 5 section of AP 42. That report includes the emission factors developed by the EPA for petroleum refineries and for the synthetic organic chemical industry (SOCMI).
*Degradation of the microbes at the interface of the biofilm and surface of the plastic media resulting in a loss of adhesion
*Formation of gases in the biofilm such as carbon dioxide, nitrogen  and methane 


An ideal filter media is a media that optimizes the [[surface area]] for microbial attachment and wastewater retention time, has a high [[Permeability (engineering)|permeability]] that maximizes air flow, resists plugging and does not degrade.
In most cases, the emission factors in Chapter 5 are included for both ''uncontrolled'' conditions before emission reduction controls are implemented and ''controlled'' conditions after specified emission reduction methods are implemented.


==Configuration of large-scale trickle filters==
Chapter 7 "Liquid Storage Tanks" is devoted to the methodology for calculating the emissions losses from the six basic tank designs used for organic liquid storage: fixed roof (vertical and
horizontal), external floating roof, domed external (or covered) floating roof, internal floating roof, variable vapor space, and pressure (low and high). The methodology in Chapter 7 was developed by the [[American Petroleum Institute]] in collaboration with the EPA.


[[Image:Trickle Filter.png|right|thumb|264px|{{#ifexist:Template:Trickle Filter.png/credit|{{Trickle Filter.png/credit}}<br/>|}}Figure 3: Schematic diagram of a complete trickle filter system.]]
The EPA has developed a software program named "TANKS" which performs the Chapter 7 methodology for calculating emission losses from storage tanks.  The program's installer file along with a user manual, and the source code are available on the Internet.<ref> [http://www.epa.gov/ttn/chief/software/tanks/index.html#order TANK download site]</ref>
 
Figure 3 schematically depicts a typical large-scale trickle filter such as in the photograph shown in Figure 1.  Most large-scale trickle filter systems share the same fundamental components:<ref name=Primer/>
 
* A large containment tank or structure which houses the bed of filter medium
* A filter medium upon which beneficial a beneficial microbial film is promoted and developed
* A distribution method for applying the influent wastewater to the  filter medium
* A system, such as a [[clarifier]], for removing the sludge from the treated effluent.
* A pumping system for recycling a portion of the clarified, treated effluent
 
Each of the arms of the rotating influent water distributor has nozzles that discharge the water in opposite directions, so that the reaction forces of the discharged jets of water cause the distributor to rotate.   
 
Systems can be configured for single-pass use where the influent wastewater is treated in a trickle filter once before being disposed of, or for multi-pass use where a portion of the treated effluent is recycled back to the trickle filter and re-treated. Multi-pass systems result in better effluent quality and assist in reducing the amount of nitrogen-containing compounds by promoting [[denitrification]] in the overall system. Nitrogen is one of the principal nutrients found in wastewater and nitrogen-containing discharges into a water resource can severely the resource and it’s
associated ecosystem.<ref name=Primer/>
 
Most large-scale trickle filters are used in:
 
* In municipal wastewater treatment facilities, also referred to as [[Publicly Owned Treatment Works]] (PTOW's).
 
* Onsite within industrial facilities that produce large amounts of biodegradable wastewaters, such as [[Petroleum refining processes|petroleum refineries]], [[petrochemical]] plants, paper mills and large food processing plants.
 
==Types of large-scale trickle filters==
 
There are a number of different designs for large wastewater trickling filters. Four of the more commonly used designs are:
 
[[Image:Shallow Ground-level Trickle Filters.jpg|right|thumb|274px|{{#ifexist:Template:Shallow Ground-level Trickle Filters.jpg/credit|{{Shallow Ground-level Trickle Filters.jpg/credit}}<br/>|}}Figure 4: Large, shallow ground-level trickle filters in a municipal wastewater treatment plant<ref name=Primer/>]]
 
*Above-ground enclosed structures (often called ''biotowers'') as in the photograph shown in Figure 1 and in the diagram (Figure 3) discussed above:&nbsp; These are used in a good many modern municipal wastewater treatment facilities.
*Shallow, ground-level versions, as in the photograph shown in Figure 4:&nbsp; These are used in many older municipal wastewater treatment plants.
*Vertical packed towers filled with plastic packing<ref>[http://www.google.com/patents?hl=en&lr=&vid=USPAT4351729&id=U3c8AAAAEBAJ&oi=fnd&dq=trickle+filter+%22packed+tower%22+wastewater Biological filter and process] U.S. patent 4,351,729, September 28, 1982, Assigned to Celanese Corporation</ref><ref>[http://www.ag.auburn.edu/~davisda/classes/facilities/presentations/Recirc_overview.pdf Lecture] by Dr. Allen Davis, [[Auburn University]], page 6 of 8 pdf pages including schematic of packed tower trickling filter)</ref> or other media:&nbsp; As early as the 1960s, such packed towers with plastic media were in use treating industrial wastewaters at: the Pine Bend Petroleum Refinery in [[Minnesota]], U.S.A.; the Trafalgar Refinery in [[Oakville, Ontario]] and at a large kraft paper mill.<ref name=Bryan>E.H. Bryan and D.H. Moeller, ''Aerobic Biological Oxidation Using Dowpac'', Conference on Biological Waste Treatment, Manhattan College, April 1960. [http://cobweb.ecn.purdue.edu/~alleman Professor Alleman's list of historical papers] ([[Purdue University]], Environmental Engineering Department).</ref> The Pine Bend Refinery tower had a bed consisting of 375 m<sup>3</sup> of plastic media, the Trafalgar Refinery had two towers with plastic media beds in each tower that were 6.5 m deep, and the kraft paper mill had 2,750 m<sup>3</sup> of plastic media in a 9.5 m deep bed.<ref name=Bryan/>
 
[[Image:Rotating Biological Contactor.png|right|thumb|350px|{{#ifexist:Template:Rotating Biological Contactor.png/credit|{{Rotating Biological Contactor.png/credit}}<br/>|}}Figure 5: Schematic diagram of a rotating biological contactor]]
 
* Rotating biological contactors referred to as RBC units:&nbsp; An RBC unit, as depicted in Figure 5, consists of a series of closely spaced, parallel discs mounted on a rotating shaft which is supported just above the surface of the waste water. Microbes grow on the surface of the discs where biological degradation of the wastewater pollutants takes place. The rotating packs of disks (comprised of plastic media) are contained in a trough. The shaft is aligned with the flow of wastewater so that the discs rotate at right angles to the flow with several packs usually combined to make up a treatment train. About 40% of the disc area is immersed in the wastewater. Aeration is provided by the rotating action, which exposes the media to the air after contacting them with the wastewater. Optionally, forced air flow may be introduced via a distribution pipe in the bottom of the trough.<ref name=Grady>{{cite book|author=C.P.  Leslie Grady, Glenn T. Daigger and Henry C. Lim|title=Biological wastewater Treatment|edition=2nd Edition|publisher=CRC Press|year=1998|id=ISBN 0-8247-8919-9}}</ref><ref name=Lee>{{cite book|author=C.C. Lee and Shun Dar Lin|title=Handbook of Environmental Engineering Calculations|edition=1st Edition|publisher=McGraw Hill|year=2000|id=ISBN 0-07-038183-6}}</ref><ref name=Metcalf>{{cite book|author=Tchobanoglous, G., Burton, F.L., and Stensel, H.D.|title=Wastewater Engineering (Treatment Disposal Reuse) / Metcalf & Eddy, Inc.|edition=4th Edition|publisher=McGraw-Hill Book Company|year=2003|id=ISBN 0-07-041878-0}}</ref>


Chapters 5 and 7 discussed above are illustrative of the type of information contained in the other chapters of AP 42. It should also be noted that many of the fugitive emission factors in Chapter 5 and the emissions calculation methodology in Chapter 7 and the TANKS program also apply to many other industrial categories besides the petroleum industry.


==Other sources of emission factors==
*[http://www.naei.org.uk/emissions/index.php United Kingdom's emission factor database].
*[http://reports.eea.eu.int/EMEPCORINAIR4/en European Environment Agency's 2005 Emission Inventory Guidebook].
*[http://www.ipcc-nggip.iges.or.jp/public/gl/invs6.htm Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories (reference manual)].
*[http://files.harc.edu/Projects/AirQuality/Projects/H005.2002/H5FinalReport.pdf Fugitive emissions leaks from ethylene and other chemical plants].
*[http://www.npi.gov.au/handbooks/approved_handbooks/sector-manuals.html Australian National Pollutant Inventory Emissions Estimation Technique Manuals].
*[http://www.ec.gc.ca/pdb/ghg/guidance/calcu_pro_e.cfm Canadian GHG Inventory Methodologies].
*[http://ghg.api.org Sangea - American Petroleum Institute Greenhouse Gas Emission Estimation Methodologies].
*[http://www.mining.ca/english/publications/Mining%20Strat_Guide_Pt_B1/index.html Mining Association Of Canada Greenhouse Gas Emission Estimation Methodologies].


==References==
==References==
{{reflist}}
==External links==
*[http://www.nmenv.state.nm.us/SWQB/FOT/WastewaterStudyManual/07.pdf New Mexico Wastewater Systems Operator Certification Study Manual, Chapter 7]
*[http://web.deu.edu.tr/atiksu/ana52/ani404.html Biological Treatment Methods] (An excellent presentation by Professor Dr.Hikmet Toprak, Dokuz Eylül University, Turkey)
==Bibliography==


*{{cite book|author=Joseph S. Devinny, Marc A. Deshusses and Todd S. Webster|title=Biofiltration for Air Pollution Control|edition= |publisher=Lewis Publishers|year=1999|id=ISBN 1-56670-289-5}}
<references/>

Revision as of 15:09, 18 April 2008

An air pollution source

The AP 42 Compilation of Air Pollutant Emission Factors, was first published by the U.S. Public Health Service in 1968. In 1972, it was revised and issued as the second edition by the U.S. Environmental Protection Agency (EPA). In 1985, the subsequent fourth edition was split into two volumes. Volume I includes stationary point and area source emission factors, and Volume II includes mobile source emission factors. Volume I is currently in its fifth edition and is available on the Internet.[1] Volume II is no longer maintained as such, but roadway air dispersion models for estimating emissions from onroad vehicles and from non-road vehicles and mobile equipment are also available on the Internet.[2]

In routine common usage, Volume I of the emission factor compilation is very often referred to as simply AP 42.

Introduction

Air pollutant emission factors are representative values that attempts to relate the quantity of a pollutant released to the ambient air with an activity associated with the release of that pollutant. These factors are usually expressed as the weight of pollutant divided by a unit weight, volume, distance, or duration of the activity emitting the pollutant (e.g., kilograms of particulate emitted per megagram of coal burned). Such factors facilitate estimation of emissions from various sources of air pollution. In most cases, these factors are simply averages of all available data of acceptable quality, and are generally assumed to be representative of long-term averages.

The equation for the estimation of emissions before emission reduction controls are applied is:

E = A × EF

and for emissions after reduction controls are applied:

E = A × EF × (1-ER/100)
where:  
E = emissions, in units of pollutant per unit of time
A = activity rate, in units of weight, volume, distance or duration per unit of time
EF = emission factor, in units of pollutant per unit of weight, volume, distance or duration)
ER = overall emission reduction efficiency, in %

Emission factors are used by atmospheric dispersion modelers and others to determine the amount of air pollutants being emitted from sources within industrial facilities.

Chapters in AP 42, Volume I, Fifth Edition

Chapter 1      External Combustion Sources
Chapter 2      Solid Waste Disposal
Chapter 3      Stationary Internal Combustion Sources
Chapter 4      Evaporation Loss Sources
Chapter 5      Petroleum Industry
Chapter 6      Organic Chemical Process Industry
Chapter 7      Liquid Storage Tanks
Chapter 8      Inorganic Chemical Industry
Chapter 9      Food and Agricultural Industries
Chapter 10      Wood Products Industry
Chapter 11      Mineral Products Industry
Chapter 12      Metallurgical Industry
Chapter 13      Miscellaneous Sources
Chapter 14      Greenhouse Gas Biogenic Sources
Chapter 15      Ordnance Detonation
Appendix A      Miscellaneous Data & Conversion Factors
Appendix B.1
  		     Particle Size Distribution Data and Sized Emission Factors
     for Selected Sources
Appendix B.2      Generalized Particle Size Distributions
Appendix C.1      Procedures for Sampling Surface/Bulk Dust Loading
Appendix C.2
  		     Procedures for Laboratory Analysis of Surface/Bulk Dust
     Loading Samples

Chapter 5, Section 5.1 "Petroleum Refining" discusses the air pollutant emissions from the equipment in the various refinery processing units as well as from the auxiliary steam-generating boilers, furnaces and engines, and Table 5.1.1 includes the pertinent emission factors. Table 5.1.2 includes the emission factors for the fugitive air pollutant emissions from the large wet cooling towers in refineries and from the oil/water separators used in treating refinery wastewater.

The fugitive air pollutant emission factors from relief valves, piping valves, open-ended piping lines or drains, piping flanges, sample connections, and seals on pump and compressor shafts are discussed and included the report EPA-458/R-95-017, "Protocol for Equipment Leak Emission Estimates" which is included in the Chapter 5 section of AP 42. That report includes the emission factors developed by the EPA for petroleum refineries and for the synthetic organic chemical industry (SOCMI).

In most cases, the emission factors in Chapter 5 are included for both uncontrolled conditions before emission reduction controls are implemented and controlled conditions after specified emission reduction methods are implemented.

Chapter 7 "Liquid Storage Tanks" is devoted to the methodology for calculating the emissions losses from the six basic tank designs used for organic liquid storage: fixed roof (vertical and horizontal), external floating roof, domed external (or covered) floating roof, internal floating roof, variable vapor space, and pressure (low and high). The methodology in Chapter 7 was developed by the American Petroleum Institute in collaboration with the EPA.

The EPA has developed a software program named "TANKS" which performs the Chapter 7 methodology for calculating emission losses from storage tanks. The program's installer file along with a user manual, and the source code are available on the Internet.[3]

Chapters 5 and 7 discussed above are illustrative of the type of information contained in the other chapters of AP 42. It should also be noted that many of the fugitive emission factors in Chapter 5 and the emissions calculation methodology in Chapter 7 and the TANKS program also apply to many other industrial categories besides the petroleum industry.

Other sources of emission factors

References

  1. ↑ AP 42, Volume I
  2. ↑ Mobile source emission models
  3. ↑ TANK download site
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