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ERDC/CERL
TR-00-40
Designing Coalescing Oil/Water Separators
for Use at Army Washracks
Constructi
on
Engineerin
g
ResearchL
aboratory
by Gary L. Gerdes, Angelo DeGuzman,
and Jeffrey GrubichDecember 200
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2 ERDC/CERL TR-00-40
Foreword
This study was conducted for the U.S. Army Corps of Engineers under project
40162720A896, Base Facilities Environmental Quality, Work Unit TB0, Oil/
Wa ter S epar a tor Technology. The technical monitor wa s Gr egory W. Hugh es
(CECW-EW).
The w ork wa s performed by the E nvironmenta l P rocesses B ra nch (CN-E) of th e
Installations Division (CN), Construction Engineering Research Laboratory(CE RL). The CE RL P rincipal Investiga tor w a s G a ry L. G erdes, CN-E. The
technical editor w a s Linda L. Whea tley, In forma tion Techn ology La bora tory. Dr.
Ilker R. Adiguzel is Chief, CN-E, a nd D r. J ohn T. B a ndy is Chief, CN. The asso-
ciat ed Techn ica l Director w a s G a ry W. Scha nche, CVT. The Acting D irector of
CE RL is William D . G oran.
CE RL is an element of the U.S . Army En gineer Research a nd D evelopment Cen-
ter (ERDC ), U .S. Army C orps of En gineers. The Director of ER DC is D r. J a mes
R. Houston a nd t he Comman der is COL J a mes S. Weller.
DISCLAIMERDISCLAIMERDISCLAIMERDISCLAIMER
The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names
does not constitute an official endorsement or approval of the use of such commercial products. All product names and
trademarks cited are the property of their respective owners.
The findings of this report are not to be construed as an official Department of the Army position unless so designated by
other authorized documents.
DESTROY THIS REPORT WHEN IT IS NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.DESTROY THIS REPORT WHEN IT IS NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.DESTROY THIS REPORT WHEN IT IS NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.DESTROY THIS REPORT WHEN IT IS NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.
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ERDC/CERL TR-00-40 3
Contents
Foreword............................................................................................................................................... 2
List of Figures and Tables.................................................................................................................. 5
1 Introduction................................................................................................................................... 7
Background ......................................................................................................................... 7
Objectives .........................................................................................................................10
Approach........................................................................................................................... 10Mode of Technology Transfer............................................................................................ 11
Units of Weight and Measure............................................................................................ 11
2 Wash Water Characterization................................................................................................... 12
U.S. Army Reserve Study .................................................................................................12
Influent Characterization: All Facilities ........................................................................................12
Aviation Support Facilities............................................................................................................13
Area Maintenance Support Activities ...........................................................................................14
Equipment Concentration Sites ...................................................................................................14
Organizational Maintenance Shops .............................................................................................14Other Sites...................................................................................................................................15
Summary...........................................................................................................................16
3 Treatability Study........................................................................................................................ 17
Experiment Design............................................................................................................17
Contaminants...............................................................................................................................18
Coalescer Material.......................................................................................................................18
Coalescing Plate Angle of Incline.................................................................................................19
Water Temperature ......................................................................................................................19
Configurations..............................................................................................................................19
Duration .......................................................................................................................................20
Surface Loading Rate ..................................................................................................................20
Sampling and Analysis.................................................................................................................21
Test Start-up.................................................................................................................................21
Results ..............................................................................................................................21
Oil and Grease Removal..............................................................................................................21
Sediment Accumulation ...............................................................................................................22
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4 Conclusions and Recommendations..................................................................................... 23
Conclusions.......................................................................................................................23
Recommendations ............................................................................................................ 23
References.......................................................................................................................................... 24
Appendix: Results of Test Cell Sampling..................................................................................... 25
CERL Distribution.............................................................................................................................. 42
Report Documentation Page........................................................................................................... 43
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ERDC/CERL TR-00-40 5
List of Figures and Tables
Figures
1 Oil and soil particle movement between parallel coalescer plates .......................8
2 Eight test cells operating in parallel .................................................................... 17
3 Coalescer configurations ....................................................................................20
A1 Polypropylene 45 degrees downward flow: TSS at surface loading rate of
0.37 gpm/ft2.........................................................................................................25
A2 Polypropylene 45 degrees downward flow: O&G at surface loading rate of
0.37 gpm/ft2.........................................................................................................26
A3 Polypropylene 60 degrees downward flow: TSS at surface loading rate of
0.37 gpm/ft2.........................................................................................................26
A4 Polypropylene 60 degrees downward flow: O&G at surface loading rate of
0.37 gpm/ft2.........................................................................................................27
A5 Polypropylene 90 degrees horizontal flow: TSS at surface loading rate of
0.37 gpm/ft2.........................................................................................................27
A6 Polypropylene 90 degrees horizontal flow: O&G at surface loading rate of
0.37 gpm/ft2.........................................................................................................28
A7 Polypropylene 45 degrees horizontal flow: TSS at surface loading rate of
0.37 gpm/ft2.........................................................................................................28
A8 Polypropylene 45 degrees horizontal flow: O&G at surface loading rate of
0.37 gpm/ft2.........................................................................................................29
A9 Polyethylene 45 degrees downward flow: TSS at surface loading rate of
0.37 gpm/ft2.........................................................................................................29
A10 Polyethylene 45 degrees downward flow: O&G at surface loading rate of
0.37 gpm/ft2.........................................................................................................30
A11 Polyethylene 60 degrees downward flow: TSS at surface loading rate of
0.37 gpm/ft2.........................................................................................................30
A12 Polyethylene 60 degrees downward flow: O&G at surface loading rate of0.37 gpm/ft
2.........................................................................................................31
A13 Polyethylene 90 degrees horizontal flow: TSS at surface loading rate of
0.37 gpm/ft2.........................................................................................................31
A14 Polyethylene 90 degrees horizontal flow: O&G at surface loading rate of
0.37 gpm/ft2.........................................................................................................32
A15 Polyethylene 45 degrees horizontal flow: TSS at surface loading rate of
0.37 gpm/ft2.........................................................................................................32
A16 Polyethylene 45 degrees horizontal flow: O&G at surface loading rate of
0.37 gpm/ft2.........................................................................................................33
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A17 Corrugated angled ribs slanted away from flow: TSS at surface loading
rate of 0.37 gpm/ft2..............................................................................................33
A18 Corrugated angled ribs slanted away from flow: O&G at surface loading
rate of 0.37 gpm/ft2..............................................................................................34
A19 Corrugated angled ribs slanted toward flow: TSS at surface loading rateof 0.37 gpm/ft
2.....................................................................................................34
A20 Corrugated angled ribs slanted toward flow: O&G at surface loading rate
of 0.37 gpm/ft2.....................................................................................................35
A21 Corrugated angled ribs slanted away from flow: TSS at surface loading
rate of 0.25 gpm/ft2..............................................................................................35
A22 Corrugated angled ribs slanted away from flow: O&G at surface loading
rate of 0.25 gpm/ft2..............................................................................................36
A23 Corrugated angled ribs slanted toward flow: TSS at surface loading rate
of 0.25 gpm/ft2.....................................................................................................36
A24 Corrugated angled ribs slanted toward flow: O&G at surface loading rateof 0.25 gpm/ft
2.....................................................................................................37
A25 Corrugated angled ribs slanted away from flow: TSS at surface loading
rate of 0.49 gpm/ft2..............................................................................................37
A26 Corrugated angled ribs slanted away from flow: O&G at surface loading
rate of 0.49 gpm/ft2..............................................................................................38
A27 Corrugated angled ribs slanted toward flow: TSS at surface loading rate
of 0.49 gpm/ft2.....................................................................................................38
A28 Corrugated angled ribs slanted toward flow: O&G at surface loading rate
of 0.49 gpm/ft2.....................................................................................................39
A29 Polypropylene 45 degrees downward flow: TSS at surface loading rate of0.25 gpm/ft2.........................................................................................................39
A30 Polypropylene 45 degrees downward flow: O&G at surface loading rate of
0.25 gpm/ft2.........................................................................................................40
A31 Polypropylene 60 degrees downward flow: TSS at surface loading rate of
0.25 gpm/ft2.........................................................................................................40
A32 Polypropylene 60 degrees downward flow: O&G at surface loading rate of
0.25 gpm/ft2.........................................................................................................41
Tables
1 Summary of sampling data from 10 facilities ...................................................... 13
2 Summary of ASF wash water characterization data ........................................... 13
3 Summary of AMSA wash water characterization data ........................................14
4 Summary of ECS wash water characterization data ..........................................14
5 Summary of OMS wash water characterization data.......................................... 15
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ERDC/CERL TR-00-40 7
1 Introduction
Background
The U.S . Army h a s thousa nds of oil/wa ter separa tors to trea t w a stewa ter from
tactical vehicle washracks at active Army, Army Reserve, and Army National
G ua rd facilities. The va st ma jority of these sepa ra tors are used as pretreat ment
prior to discharge of wa ste wa sh wa ter into a sa nitar y or industrial sewer. Exist-
ing Army separators are typically below ground, cast-in-place concrete, simplegra vity-ty pe sepa ra tors. Simple gra vity separ a tors consist of a chamber or
chambers w here the velocity of wa stewa ter slows enough to a llow free oil to rise
to th e sur fa ce. Ca st-in-place concrete sepa ra tors, however, a re seldom con-
st ruct ed a nym ore, an d designer s now specify/inst a ll off-th e-shelf oil/w a ter sepa-
ra tors. Most off-the-shelf separa tors being insta lled currently a re coalescing-
type gra vity separa tors. Fa cility designers choose coalescing separ a tors beca use
they are smaller, less expensive, and require less site work than the equivalent
simple gravity separa tors. Many ma nufacturers now offer a boveground separ a-
tors th a t a re significant ly less expensive to inst a ll .
Oil/wa ter sepa ra tor ma nufa cturers a lso incorporat e coalescers in t heir designs to
improve th e performa nce. B eca use coalescing devices short en the dist a nce oil
par ticles must r ise, oil remova l is quicker a nd ma y occur in a sma ller separa tion
cha mber. Sm a ll oil par ticles rise to collect on th e surfa ces of th e coalescer, com-
bine to form la rger globules (coa lesce), a nd migra te to th e wa ter sur face. The
heavier soil part icles sink to th e lower coa lescer sur fa ce, a nd eventua lly slide to
th e bott om of the separa tor. Figure 1 shows th e schema tic of part icle movement
in a simple par a llel-plat e coalescer.
Coalescers have many configurations, from simple arrays of parallel plates to
honeycomb meshes. Recent tr ends in coalescer design ar e to ca use many
cha nges in th e direction of flow a s wa stewa ter winds i ts w ay through the separa -
tor. The intent is to ca use non-lamina r flow, thus increasing th e probability tha t
oil droplets w ill collide a nd coa lesce.
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Figure 1. Oil and soil particle movement between parallel coalescer plates.
The Corps of E ngin eers E ngin eering Technica l L ett er (E TL) 1110-3-466, Selec-
tion an d Design of Oil Wa ter S epa ra tors a t Army F a cilities, August 1994, con-
ta ins some discussion of coalescing sepa ra tors, but little or no da ta wa s a vaila ble
to support specific design guida nce. The la ck of specific design guida nce ha s led
to the purcha se of incorrectly sized separa tors at Army insta llations. This wa s
report ed in P ublic Works Technica l B ullet in (P WTB ) 200-1-05, Oil/Wa t er S epa -
ra tor Selection, Inst a llation, a nd Ma intena nce: Lessons Lear ned, 5 December
1997. The P WTB a lso discusses how vendor litera tu re ca n be mislead ing, fur-
ther reinforcing th e need for design guida nce.
ETL 1110-3-466 raises concerns that solids in Army wash water will collect in
th e ga ps betw een coa lescer surfa ces an d plug the separ a tor. To minimize plug-
ging, it recommends a t least 0.75-in. gaps between surfa ces. B eca use of the
plugging problem, the ETL also raises concerns regarding the maintenance re-
quirements for coa lescing separa tors. These concerns a re demonstr a ted a t every
Army installation by the need for periodic separator cleaning, not for the accu-mula tion of oil but for t he a ccumula tion of sediment.
The ETL recommend s th a t a ny Arm y oil/w a ter sepa ra tor mu st be easily a ccessi-
ble for periodic ma int ena nce. This a ccessibility is especia lly crit ical for coalesc-
ing sepa ra tors. The coa lescer pa ck must be ea sy to remove and ea sy to clean.
G enerally, only t he pa ra llel-plat e coa lescers a re ea sy t o clea n wit hout completely
disma nt ling the coa lescer pack. This genera lization wa s confirmed by CERL
Oleophi l ic m aterial
surface
Flow
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ERDC/CERL TR-00-40 9
personnel who inspected separators with mesh or vertical mesh tube-type coa-
lescers. These coalescers seem to eas ily plug w ith vegeta tion debris commonly
found in Army wa sh wa ter. Only coalescing separa tors with the fla t para llel
plates ca n be r ecommended for Army use; therefore, they w ere the prima ry focus
of this st udy.
Dirt washed off Army vehicles becomes suspended solid particles in the waste
wa sh wa ter. These par ticles a tt a ch to the oil droplets, thus interfering w ith the
oil removal ca pa city of the separ a tor. This process is described in th e Corps ETL
on sepa ra tor design (U SACE 1994) a nd B rincks (1996). It is a lso supported by
observations of significant amounts of oil in the sediment of Army separators.
Oil-soil agglomerations have a wide range of specific gravities, but always are
more dense th a n oil droplets. St okes La w is t ypica lly used to model the sepa ra -
tion of oil an d w a ter.
Stokes Law : Vp= 54.48 (
p-
w)d
p
2 Velocit y (V
p) is positive if pa rt icle is
falling; negat ive if rising.
Stokes La w generally sa ys th a t t he velocity of rise (or fall) of a par ticle in wa ter
is proport iona l to: the specific gra vity of the par ticle minus 1; the diam eter of
th e pa rt icle; an d the temperat ure of the wa ter. As the specific gra vity of th e par -
ticle approaches that of water (usually 1.0), the velocity of the particle ap-
proaches zero. Therefore, w hen a pa rt icle of oil a tt a ches to a soil pa rt icle, th e
velocity of rise decreases. If t he soil pa rt icle is la rge enough, th e oil-soil a gglom-erat ion w ill sink.
For St okes law to be a pplica ble wh en modeling th e oil separa tion from wa stewa -
ter laden w ith suspended solids, the distr ibution of oil par ticle a nd oil-soil par ti-
cle diameters a nd specific gra vities must be known. P rior to this stu dy, this dis-
tr ibution w a s never char a cterized. Therefore, separ a tor performa nce could not
be predicted for Army w a sh w a ter using St okes Law.
Ma ny v endors of off-th e-shelf oil/w a ter separ a tors u se St okes law to predict the
performa nce of their equ ipment for removing free oil. This can only be applica -
ble for simple mixtu res of free oil droplets in wa ter. Thus , vendor litera tu re ca n
be mislea ding t o persons responsible for pur chasing sepa ra tors for Army a pplica -
tions. B eca use Army gu idan ce did not exist, an d vendor guida nce is not a pplica -
ble, this study wa s conducted so tha t insta l lat ion personnel , as w ell as w ashr ack
designers, have specific guidance for the selection of off-the-shelf coalescing
oil/w a ter separ a tors.
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Objectives
It w a s th e objective of th is study to develop design guida nce tha t ca n be used by
Army planners a nd designers w hen inst a lling coalescing-ty pe oil/wa ter sepa ra -
tors to pretrea t vehicle ma intena nce wa sh wa ter. It w a s also a n objective to
characterize the oil-soil agglomerations that obviously form during the washing
process.
Approach
The approa ch for this study ha d tw o thr usts: (1) char a cterize Army w a shra ck
wastewater, and (2) conduct bench-scale treatability studies to match coalescer
design wit h Army w a sh wa ter. The char a cterizat ion study ha d to be completedbefore ini t iat ing the treat abil ity study. Army w ash w at er wa s recreated in the
laboratory based on the contaminant loading measured at actual Army wash-
ra cks. It w a s most import a nt t o know the concentra tions of suspended solids
a nd gr ease/oil in t he wa ter, since it is t hese conta mina nts tha t a re removed from
th e w a stew a ter in the oil/w a ter separa tor.
Wa sh w at er wa s sa mpled a nd a na lyzed from severa l Army w ashr acks, represent-
ing a va riety of vehicle w a shing scena rios. Cha pter 2 of th is report presents t he
results of this portion of the study.
The challenge to chara cterizing t he oil-soil agglomerat ions t ha t form during the
washing process was that the wash water is a non-homogeneous mixture of oil
droplets, soil pa rt icles, a nd oil-soil a gglomera tions. A meth od to different ia te
these components during a par ticle size ana lysis could not be found. In pa rt icu-
lar, a method t o distinguish oil-soil agglomerat ions of va rious constituent ra tios
seemed impossible to devise. Furt her, there wa s no gua ra nt ee th a t pa rt icle iden-
tification techniques would not alter the character of fragile oil-soil agglomera-
tions during the ana lysis. It w a s concluded tha t cha ra cterizing the par ticle dis-
tribution of Army w ash wa ter w as n ot pra ctica l , and t ha t t he cha ra cterization ofthe wash water would rely entirely on measuring the concentrations of oil and
solids. Note: Without par ticle size distr ibution a nd a gglomera tion cha ra cteriza-
tion dat a, St okes La w cannot be used to predict oil/wa ter sepa ra tor performa nce
for Army w ash wa ter.
An a rra y of test cells wa s constructed to conduct t he trea ta bility st udy. The test
cells were constructed so that several coalescer configurations could be evaluated
a t t he same time, using a common source of wa stew a ter influent. The concentra -
tions of oil and solids in the wastewater were set according to the results of the
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ERDC/CERL TR-00-40 11
wa sh wa ter sa mpling stud y. Cha pter 3 of th is report discusses the experimenta l
para meters and test results .
A performa nce goa l of 100 ppm oil a nd g rea se (O&G ) in t he test cell effluent w a s
set. This goa l represents a commonly used pretreat ment requirement set by
ma ny P ublicly Ow ned Trea tm ent Works (P OTW). The success of a given test ing
scena rio is based on t his performa nce goa l.
The presence of solids in the wash water affects performance in ways besides
th eir becoming tied up with th e oil droplets. It w a s also suspected tha t solids
w ould a ccumu la te on the surfa ce of th e coa lescer. This accumula tion would
negatively affect performance by narrowing the gap between the coalescer sur-
faces, thus increasing t he velocity of wa ter t hrough th e coalescer a nd decreasing
droplet removal. Solids could a lso negat ively a ffect performa nce if they coa tedthe oliophilic coalescer ma teria l, thus diminishing the a va ilable surface on w hich
th e oil droplets could coa lesce. Ev idence of th ese effects w ould ha ve a bea ring on
both recommended design an d ma intena nce requirements for coa lescing separa -
tors.
Mode of Technology Transfer
Information in this technical report will be provided to the U.S. Army Engineer
Distr ict a t Mobile, AL, for inclusion in t he new Corps of EngineersG uide S peci-
fica tion for P refabr ica ted Oil-Wa ter Separ a tors for Militar y Applicat ions. I t wil l
a lso be provided t o the D OD Clean Wa ter Act Services S teering Committ ee
Oil/Wa ter S epar a tor Work G roup for fut ure upda te t o in t he Oil/Wa t er Sepa ra -
tor Guidance Manual , which is currently under review prior to initial publica-
tion.
Units of Weight and Measure
U .S. sta nda rd unit s of measure a re used in th is report . A ta ble of conversion fac-
tors for S ta nda rd In terna tional (SI ) units is provided below.
SI conversion factors
1 gal = 3.78 L
1 ft2
= 0.093 m2
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2 Wash Water Characterization
The information in this chapter summarizes the data obtained during studies
conducted by C ERL during w hich sa mpling of oil/w a ter separ a tor influent wa s
necessary. Hea dqua rt ers, U.S. Army Reserve Comma nd co-sponsored a CE RL
study to characterize wash water at various Reserve maintenance faci l i t ies.
Results from the unpublished report of that study (Gerdes 1997) are included
below. Da ta from two studies sponsored by the U.S . Army E nvironmenta l Center
a re a lso included, as w ell as da ta from a q uick-relea se detergent st udy conducted
by CERL for the (former) U.S. Army Corps of Engineers Center for Public Works
(1997).
U.S. Army Reserve Study
Onsite sampling efforts generated da ta chara cterizing w a stewa ter from severa l
Army Reserve sources. CE RL sampling tea ms visited 11 w a stew a ter genera tors
during th e stud y. An avera ge of eight sa mples were taken during a t ypica l wa sh-
ing event at each generat or. Cha ra cteristics measur ed w ere: O&G , chemicaloxygen demand (COD), total suspended solids (TSS), volatile suspended solids
(VSS ), a nd flow. Sa mples represent ed low -pressur e clea ning, high-pressur e
cleaning, a nd cleaning w ith detergents. Sit es for these stud ies included:
Tw o Avia t ion Su pport F a cilities (ASFs )
Thr ee Area Ma int ena nce Su pport Activities (AMS As)
Tw o Equ ipment Concentra tion Sit es (EC Ss)
Three Reserve Center Orga nizat iona l Ma intena nce Shops (OMSs)
Inf luent Characterizat ion: All Faci l i t ies
Ta ble 1 summa rizes the wa sh wa ter an a lysis da ta from 10 sites visited. Flow a t
the 10 wa shra cks summa rized in the ta ble ra nged from 1.5 gpm to 19 gpm. Av-
erage flow at those washracks is about 7 gpm.
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ERDC/CERL TR-00-40 13
Table 1. Summary of sampling data from 10 facilities.
Parameter Average (mg/L) Peak (mg/L)
O&G 316 1584
TSS 1061 6502
VSS 277 1584
COD 2232 40,175
G enerally, as flow increases, the concentra tion of conta mina nts decreases. Or,
more a ccura tely, w hen high-pressure/low-flow w a shers a re used, conta mina nt
concentr a tion tend s to be much higher t ha n w hen low-pressur e/high-flow hoses
ar e used. Wa shrack wa stewa ter would never have the maximum conta minant
concentr a tions (listed in Ta ble 1) th roughout a w a shing event. Flow a nd con-
taminant levels vary significantly.
Aviat ion Suppo rt Faci l i t ies
CE RL personnel visited t w o of the t hree ASF s rema ining under th e command of
th e Army Reserve. Ta ble 2 summa rizes the ana lysis dat a from sa mples obta ined
during t hose visits.
Table 2. Summary of ASF wash water characterization data.
Parameter Average (mg/L) Peak (mg/L)
O&G 594 1584
TSS 625 1386
VSS 408 1042
COD 8478 40,175
Helicopter wa shing is u sua lly done with modera te t o low -pressure wa shing (300
psi or less) a t low flows (less th a n 5 gpm per hose). A va riety of surfa ce clea ning
a gents a re used, all of which add considerable COD to th e wa stew a ter. At both
locations, the surface cleaner was applied to the oily parts of the aircraft and al-
lowed to soa k. Exceptionally high COD occurs in the wa sh wa ter wh en these
par ts a re rinsed (see P eak COD ).
About two-thirds of the suspended solids in the aircraft wash water are volatile.
The sources of these volatile solids in the wash water are believed to be (1) the
accumulation of vegetation particles that collect in the aircraft during takeoffs
and landings, (2) the O&Gs that attach to the vegetation and inorganic soil par-
ticles, and (3) traces of concentrated surface cleaner that remain attached to the
soil part icles. The designer of pretreat ment for aircra ft w a shing should ta ke into
considerat ion t he light d ensity solids. These solids will ha ve nea r neutr a l buoy-
a ncy an d will pa ss over and un der baffles. It is recommended tha t some type of
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screening be used to remove these solids from th e wa ste strea m. Such a screen
could help protect coa lescer sur fa ces in upst rea m oil/w a ter sepa ra tors fr om clog-
ging. Screens would a lso benefit pretrea tment a t ground vehicle w a shra cks
wh ere vehicle exteriors ar e wa shed.
Area Maintenance Support A ctiv i t ies
The AMSA shops perform a higher level of maint enan ce th a n t ha t performed in
an OMS. It is simila r to tha t performed at D irect S upport ma intenance shops at
lar ge U.S. Forces Comman d an d U.S . Army Tra ining and D octr ine Comma nd
(FORS COM/TRADOC) inst a llat ions. With in the Reserves a re severa l hun dred
AMSA shops. CE RL sam pling tea ms visited three of them. Ta ble 3 summa rizes
the a na lysis da ta from sa mples obta ined during t hose visi ts .
Table 3. Summary of AMSA wash water characterization data.
Parameter Average (mg/L) Peak (mg/L)
O&G 478 1419
TSS 1272 6502
VSS 416 1584
COD 1841 10316
Equipm ent Concentrat ion Sites
Maintena nce shops at the E CSs ar e used to perform ma intenance similar t o that
performed at AMSAs a nd OMSs. However, the avera ge chara cteristics of the
wa sh wa ter were more simila r to tha t of OMS wa sh wa ter. This may be because
one of th e EC S s visited used a low -pressur e/high-flow hose for w a shing, w hich
tends to lower the concentr a tion of cont a mina nt s due to dilution. CE RL sam-
pling team s visited two ECS s. Ta ble 4 summa rizes the an a lysis da ta from sa m-
ples obta ined during th ose visits.
Table 4. Summary of ECS wash water characterization data.
Parameter Average (mg/L) Peak (mg/L)
O&G 183 484
TSS 1856 6015
VSS 239 1359
COD 692 3024
Organizational Maintenance Shop s
Maintenance performed at the organizational level is normally routine and does
not require highly specia lized repair equipment. Wa shra cks a re used to clean
vehicles returning from local (nontactical) usage and for cleaning vehicles before
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ERDC/CERL TR-00-40 15
they are sent to an AMSA or Depot for more intensive repair or rebuilding.
There are more than 1000 Army Reserve Centers (ARCs), most of which have an
OMS. CE RL sa mpling tea ms visited th ree OMSs. Ta ble 5 summa rizes the
analysis data from samples obtained during those visits.
The vehicles washed at the OMSs visited were not very dirty, but this seems to
be typica l of the soiling on vehicles wa shed at OMSs. Soaps a nd surfa ce cleaners
a re seldom used a nd should not be used.
Table 5. Summary of OMS wash water characterization data.
Parameter Average (mg/L) Peak (mg/L)
O&G 58 209
TSS 611 3882
VSS 77 182
COD 99 262
Other Sites
For t L ee, VA Transpor tat i on M otorpool . Wash wa ter from the tra nsporta t ion
motorpool (TMP) washrack was sampled during an evaluation of a simple grav-
ity sepa ra tor retr ofitted w ith coa lescing tubes (G erdes 1998). The results of the
analysis of the separator influent samples are as follow:
TSS -- 210 mg/L O&G -- 241 mg/L
Army N ati onal Guar d Or ganizati onal M ain tenance Shops. Wa sh w a ter from
tw o OMS wa shra cks were an alyzed during a study sponsored by the Army E nvi-
ronmenta l Center (AEC ) (Hu dson and G erdes 1998). The results of wa sh w a ter
an alysis a re a s follow:
Tota l P et roleu m H yd roca rb ons (TP H ) -- 406 mg/L pea k -- 1380 mg /L
Fort L ewi s M ain tenance Support B atal l i on. Wa sh wa ter from a vehicle ma in-
tenance wa sh a rea inside a Fort Lewis motorpool wa s a na lyzed during a study toevalua te a quick-relea se detergent (U SACE P WTB ). The results of the w a sh w a -
ter a nalysis ar e as follow:
O&G -- 250 mg/L TSS -- 700 mg/L
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16 ERDC/CERL TR-00-40
Summary
All of t he va lues report ed in t his chapt er (except peak va lues) a re a verages of the
a na lyses of several sa mples t a ken over the course of one or more vehicle wa shing
events. It is obvious tha t Army w a sh wa ter conta ins a wide ran ge in the concen-
tr a tions of O&G a nd TSS . The avera ge concentra tion of O&G a t t he different
ty pes of w a shr a cks ra nged fr om 58 mg/L to 594 mg/L. The peak concent ra tions
mea sur ed ra ng ed from 209 mg/L to 1584 mg/L. Avera ge TSS concent ra tions
ra nged fr om 210 mg/L to 1272 mg/L. P ea k TSS concentr a tions r a nged fr om 1386
mg/L t o 6502 mg/L.
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ERDC/CERL TR-00-40 17
3 Treatability Study
Experiment Design
The overall purpose of the experiment was to determine how well various con-
figurations of coalescers could treat fabricated Army wash water, and more spe-
cifically, to determine if buildup of solids within the coalescer structure would
negat ively affect performa nce. Such a st udy ha s numerous par a meters (i .e., con-
centration of O&G, concentration of TSS, coalescer material, incline angle of coa-lescer sur fa ces, coalescer surfa ce spacing, surfa ce loa ding ra te of th e wa sh w a ter,
wa ter temperat ure, and dura tion of the test runs). The resources a va ilable to
the project limited th e number of experiment a l configura tions. Configurat ions
were selected that would most efficiently achieve the goals of the project.
To conduct t he experiment , pilot-sca le P lexigla s test cells were constr ucted. Tw o
sets of test cells were used, each with four parallel cells fed by one source of
w a stew a ter. A uniq ue coa lescer configura tion wa s pla ced in each cell. The cells
were constructed with overflow influent weirs set to equalize flow to all four
cells. U nderflow effluent ba ffles were used to cont a in the separ a ted O&G .
Wa stewa ter w a s mixed in tw o 55-ga l drums, each of which fed wa stew a ter by
gra vity t o one of th e sets of four t est cells. Figure 2 show s th e test cells.
Figure 2. Eight test cells operating in parallel.
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18 ERDC/CERL TR-00-40
Contaminants
The concentrations of O&G and TSS were not variable parameters during the
study, a nd were kept as consta nt a s possible. Inst ead, conta mina nt levels w ere
used tha t r epresented the upper ran ge of the levels measured during t he cha ra c-
ter iza tion stu dy. The concentr a tion of oil in th e test cell influent w a s kept close
to th e ra nge of 450 to 500 mg/L. No at tempt w a s ma de to keep th e concentr a tion
of oil in t he test cell influent consta nt, a s a va ria ble concent ra tion wa s more rep-
resenta tive of Army wa shra ck wa stew a ter. U sed oil from Army ma intena nce
shops, primar ily a mixture of motor oil an d hyd ra ulic oil , wa s used wh en mixing
the fabrica ted wa stewa ter.
The concent ra tion of TSS w a s kept close to a r a ng e of 150 to 250 mg/L. Tha t con-
centration is lower than what was measured during the characterization study.More tha n ha lf of the sol ids in wa sh wa ter a re larger pa rticles tha t t end to sett le
out in a gri t basin or a t t he head end of a separ at or, a nd do not pa ss through the
coa lescer. Only fine silt and clay par ticles were mixed in the fabr ica ted
wa stewa ter influent. Sediment from the effluent end of a centra l ized wa sh
facility sedimenta tion basin w a s used as th e source.
Clean tap water, oil , and a sediment slurry were fed into a mixing barrel to cre-
a te th e wa stew a ter for the test cell experiments. As the components w ere fed
into the bar rel, they w ere consta nt ly mixed with a motorized propeller. The
wastewater overflowed by gravity into a trough, from which the wastewater
passed over w eirs into the individua l test cells. Ta p wa ter flow into the mixing
drum w a s consta ntly measured with a flow meter. Flow from each test cel l wa s
periodically measur ed man ua lly. The oil and sediment w ere fed using pa ra sta llic
metering pumps.
Coalescer Material
Two ma teria ls w ere used for t he par a llel plat e coa lescers polypropylene and
high densit y polyeth ylene. P olypropylene is th e more oleophilic of th e tw o plas-tics, a nd seems t o be th e most commonly u sed ma ter ia l in off-th e-shelf oil/w a ter
separ a tors. Some people in the indust ry believe th a t polypropylene is too oleo-
philic a nd does not a llow oil to migrat e to th e wa ter surfa ce. P olyethylene, a n-
other commonly used material, was chosen as an alternative material for com-
parison.
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ERDC/CERL TR-00-40 19
Coalescing Plate Angle of Incl ine
Separ a tor ma nufa cturers commonly use two a ngles of incline to the horizont a l
45 a nd 60 degrees. These tw o angles w ere used for most of th e test cell configu-
ra tions. The 45-degree a ngle w a s used in tw o configur a tions one with the
plates at a 45-degree angle to the horizontal inlet-to-outlet axis; and the other
with the plates parallel to the horizontal inlet-to-outlet axis (looking like an in-
verted V). Dur ing the first t est period, one test cell had vertical plat es pa ra llel to
th e horizonta l flow. Dur ing the second test period, tw o cells purchased for test-
ing were configured with a waffle-shaped polyethylene coalescer, a proprietary
design of La nda Wa ter Cleaning Sy stems (Ca ma s, WA).
Water Temperature
Due to resource restraints , wa ter temperatur e was not used as a va riable. Be-
cause of the design of the wa stewa ter mixing a ppar at us, the tempera ture of the
test cell influent w a s consistent for a ll cells. The temperat ure in th e test cells
wa s close to tha t of th e cold ta p wa ter source, a nd w a s assum ed to be represent a -
tive of the w a ter tempera ture a t most outdoor Army w ashr acks.
Conf igurat ions
Figure 3 show s th e six basic configura tions used during this st udy. The pla te
positioning a nd flow direction of the individual test cells were a s follows:
Polypropylene 45oDownwa rd f low
Polyethylene 45oDownwa rd f low
Polypropylene 60oDownwa rd f low
Polyethylene 60oDownwa rd f low
Polypropylene 45
o
Horizonta l flow
Polyethylene 45oHorizont a l flow
Polypropylene 90oHorizonta l flow
Polyethylene 90oHorizont a l flow
Landa wa ffle a ngled ribs slanted t owa rd t he horizonta l flow
Landa wa ffle a ngled ribs slanted a wa y from the horizonta l flow
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20 ERDC/CERL TR-00-40
Top View
(plates perpendicular to page)
Flow
(corrugated plates
parallel to page)
Flow
(corrugated plates
parallel to page)
Flow
(plates perpendicular to page)
Flow
45
(plates perpendicular to page)
Flow
60
(flow and plates
perpendicular to page)
45
Figure 3. Coalescer configurations.
Duration
The fabricated wash water was allowed to run through the test cells for periods
of 2 hr. Resear chers ra n one 2-hr test per da y. This schedule wa s to a pproxi-
ma te a t ypical 1-day use at a n Army w ashr ack. Ini t ial ly ea ch test cel l wa s oper-
ated for at total of at least 100 hr, to represent approximately 1 year s usage a t
an average Army w a shrack.
The polypropylene coa lescer t est cells w ere opera ted for a n extend ed period. The
intent was to determine if performance would eventually drop significantly due
to an excessive buildup of oil a nd solids on th e coa lescer surfa ces. E ssent ia lly
th e extended test w a s to determine if the coa lescer w a s a ctua lly performing more
as a f il ter a nd thus breakthrough could occur.
Surface Loading Rate
The surface loading rate for the initial test period was set according to the sur-
face loading ra te equa tion in AP I s oil/w a ter sepa ra tor design m a nua l (AP I 1992,p 26) for removing 60-micron oil particles.
Surfa ce loa ding rate = Qm/A
H= 0.00386(S
w- S
o)/
Qm= design flow (ft
3/min )
AH= projected horizonta l ar ea (ft
2) for a ll coa lescing su rfa ces (one side for
each pla te)
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ERDC/CERL TR-00-40 21
Sw= specific gra vity of w a ter
So= specific gra vity of oil
= wa stewa ter viscosi ty in poise
Design flow w a s set a t 1.5 gpm (0.20 cfm) for ea ch test cell. The projected h ori-
zonta l ar ea for th e coa lescer ma teria l in each test cell wa s a pproximat ely 4.08 ft2.
The sur fa ce loa ding r a te for th e first t est period wa s 0.37 gpm/ft2 (0.05 cfm/ft
2).
Su rfa ce loadin g r a tes of 0.25 gpm/ft2a nd 0.49 gpm/ft
2were used for a few of the
configura tions in a la ter t est period.
Sampling and Analysis
Influent and effluent composite samples were taken after every fifth 2-hr test
cell opera tion run (i.e., a fter 10 hr of opera tion). Sa mples w ere ta ken more fre-
quently at the beginning of each test cell experiment to adjust the contaminant
feed pumps and establish the desired contaminant levels in the fabricated wash
w a ter. TSS a na lysis w a s done a ccording to St a nda rd Methods. Ana lysis for
O&G was done according to a variation of EPA Method 1664, Revision A, devel-
oped by 3M Company and sanctioned by the U.S. Environmental Protection
Agency (U SE PA). An independent study ha s shown t ha t this test ha s equiva lent
or great er a ccura cy tha n t he original Method 1664.
Test Start-up
At t he beginning of each experiment, th e coalescer ma teria l in each t est cell wa s
coa ted wit h oil . The int ent wa s to season th e surfa ces in order to eliminat e the
initial period of oil accumula tion, a nd thu s a llow oil remova l in th e test cells to
a chieve a st eady sta te more quickly.
Results
Graphs showing all results of the test cell sampling analysis are shown in the
a ppendix. The following pa ra gra phs describe CE RL s interpretat ion of tha t da ta .
Oil and Grease Removal
During the first 100 hr of operation, the down-flow, 45 degree, polypropylene
platesprovided the best effluent qu a lity a t t he overflow r a te of 0.37 gpm/ft2.
H owever, the oil concentr a tion in t he test cell influent w a s over 50 mg/L less
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22 ERDC/CERL TR-00-40
th a n for th e polyeth ylene test cells. Du ring th e second 100 hr of opera tion, the
concentration of oil in the influent to the polypropylene plate cells was closer to
the level going to the polyethylene plate test cells, and performance dropped be-
low th a t of t he dow n-flow, 60-degree, polyet hylene.
Only the 60-degree down-flow configuration of the polyethylene plates provided
consistent treatment performance in achieving the target effluent level of 100
mg/L oil at t he su rf a ce loa din g r a te of 0.37 gpm/ft2. However, a t a surface loa d-
ing ra t e of 0.25 gpm/ft2, both the 45- and 60-degree, down-flow, polypropylene
configura tions provided consistent, a cceptable tr eat ment.
P olyethylene appear ed to be the better of the tw o coa lescer ma teria ls. There ar e
other ma teria ls tha t could not be tested, however, due to limited resources, a nd it
is possible tha t some of those perform a s w ell or better t ha n polyethy lene.
Sediment Accum ulat ion
There was no visual evidence that sediment accumulation on the surface of the
coa lescer pla tes w ould ha ve ca used interference with the performa nce of th e test
cells. Sediment coa ted th e top surfa ce of each of the coa lescer plat es, but ap-
peared to migrate to the bottom of the separation chamber before reaching a
th ickness of 0.1 in. The concentr a tion of TSS in th e effluent r ema ined fa irly con-
sta nt for a ll configura tions, and seemed to decrease slightly over t ime for a few of
the configura tions during t he test period.
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ERDC/CERL TR-00-40 23
4 Conclusions and Recommendations
Conclusions
1. The test cell configur a tion wit h polyeth ylene pla tes insta lled a t a 60-degree
an gle an d ha ving a downw ar d flow seemed to provide the best t reatment at
th e loa din g ra t e of 0.37 gpm/ft2.
2. There wa s no evidence th a t, dur ing th e norma l opera tion of an oil/w a tersepa ra tor, a lay er of sediment w ould collect on coa lescer pla tes a t a th ickness
that would interfere with flow through the coalescer, assuming the plate
spacing wa s a t least 0.75 in.
Recommendations
1. When s pecifying off-th e-shelf, coa lescing, oil/w a ter separ a tors, recommend
the following:
Coalescer plate material: Polyethylene
Ma ximum surf a ce loa ding ra te: 0.37 gpm/ft2
Coa lescer plat e a ngle: 60 degrees
Direction of flow: Downw a rd a t 60 degrees to the horizonta l
2. Coalescing sepa ra tor designs must provide stora ge for solids removed withinthe coalescer.
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24 ERDC/CERL TR-00-40
References
American P etroleum I nstit ute (AP I), Monographs on Refinery E nvi ronm ental Control - M anage-
ment of Water Di schar ges; Design and Operati on of Oil / Water Separators, AP I P ublica tion 421,
Firs t E d., Februa ry 1990 (revised November 1992).
Brincks, Richard, Oil/Wa ter Sepa ra tors-Design & Selection, Envi ronm ental Techn ology,
Ma y/J un e 1996, pp 44-46.
G erdes, G a ry, Trip Report for Fort Lee, VA, 31 Ma rch 1998.
Gerdes, Ga ry L. , Cha ra cterization of Oil/Wa ter Separa tor Influent at U.S . Army Reserve Fa cili-
ties , U.S. Army C onstruction Engineering Resear ch Labora tory (USACERL) Letter Report
(unpublis hed), November 1997.
Hudson, Kenneth L. a nd G ary L. Gerdes, A D ecision Tree for I mpr ovin g Washrack Oil / Water Sepa-
rator Operat i ons, U SAEC Report No. SF IM-AEC -ET-R-98003, J a nua ry 1998.
U. S. Army Center for Public Works, Oil/Wat er Separa tor Selection, Inst alla tion, a nd Ma inte-
na nce: Lessons Learned, Techni cal B ullet in N o. 200-1-05, 5 December 1997.
U.S . Army Corps of Engineers (USACE), Selection an d Design of Oil/Wa ter Sepa ra tors a t Arm yFacilities, Techni cal Let ter No. 1110-3-466, 26 Augu st 1994.
USACE, Effect of Quick Release Detergen t on Oil/Wa ter S epara tors, P ublic Works Technical B ul-
letin 420-49-28 (pendin g).
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ERDC/CERL TR-00-40 25
Appendix: Results of Test Cell Sampling
Polypropylene-45 degrees- Downward Flow: Total Suspended Solids vs Time ( overflow rate: 0.37 gpm/sq ft )
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120 140 160 180 200
time (hrs)
TSS(ppm)
Influent Effluent
Figure A1. Polypropylene 45 degrees downward flow: TSS at surface loading rate of 0.37
gpm/ft2.
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26 ERDC/CERL TR-00-40
Polypropylene-45 degrees- Downward Flow: Grease and Oil vs Time (ove rflow rate: 0.37 gpm/sq ft)
0
100
200
300
400
500
600
700
800
0 20 40 60 80 100 120 140 160 180 200
time (hrs)
G&O
(ppm)
Influent Effluent
Figure A2. Polypropylene 45 degrees downward flow: O&G at surface loading rate of 0.37
gpm/ft2.
Polypropylene-60 degrees- Downward Flow: Total Suspended Solids vs Time (overflow rate: 0.37 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120 140 160 180 200
time (hrs)
TSS(ppm)
I nfluent E ffluent
Figure A3. Polypropylene 60 degrees downward flow: TSS at surface loading rate of 0.37
gpm/ft2.
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ERDC/CERL TR-00-40 27
Polypropylene-60 degrees- Downward Flow: Grease and Oil vs Time (overflow rate: 0.37 gpm/sq f t)
0
100
200
300
400
500
600
700
800
0 20 40 60 80 100 120 140 160 180 200
time (hrs)
G&O
(ppm)
Influent Effluent
Figure A4. Polypropylene 60 degrees downward flow: O&G at surface loading rate of 0.37
gpm/ft2.
Polypropylene-90 degrees- Horizontal Flow: Total Suspended Solids vs Time (overflow rate: 0.37 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
time (hrs)
TSS(ppm)
Influent Effluent
Figure A5. Polypropylene 90 degrees horizontal flow: TSS at surface loading rate of 0.37
gpm/ft2.
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28 ERDC/CERL TR-00-40
Polypropylene-90 degrees- Horizontal Flow: Grease and Oil vs Time (overflow rate: 0.37 gpm/sq ft)
0
100
200
300
400
500
600
700
800
0 20 40 60 80 100 120
time (hrs)
G&O
(ppm)
Influent Effluent
Figure A6. Polypropylene 90 degrees horizontal flow: O&G at surface loading rate of 0.37
gpm/ft2.
Polypropylene-45 degrees- Horizontal Flow: Total Suspended Solids vs Time (overflow rate: 0.37 gpm/sq f t)
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
time (hrs)
TSS(ppm)
Inf luent Ef fluen t
Figure A7. Polypropylene 45 degrees horizontal flow: TSS at surface loading rate of 0.37
gpm/ft2.
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ERDC/CERL TR-00-40 29
Polypropylene-45 degrees- Horizontal Flow: Grease and Oil vs Time (overflow rate: 0.37 gpm/sq ft)
0
100
200
300
400
500
600
700
800
0 20 40 60 80 100 120
time (hrs)
G&O
(ppm)
Influent Effluent
Figure A8. Polypropylene 45 degrees horizontal flow: O&G at surface loading rate of 0.37
gpm/ft2.
Polyethylene-45 degrees- Downward Flow: Total Suspended Solids vs T ime (overflow rate: 0.37 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
time (hrs)
TSS(ppm)
Influent Effluent
Figure A9. Polyethylene 45 degrees downward flow: TSS at surface loading rate of 0.37 gpm/ft2.
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30 ERDC/CERL TR-00-40
Polyethylene-45 degrees- Downward Flow: Grease and Oil vs Time (overflow rate: 0.37 gpm/sq ft)
0
100
200
300
400
500
600
700
800
0 20 40 60 80 100 120
time (hrs)
G&O
(ppm)
Influent Effluent
Figure A10. Polyethylene 45 degrees downward flow: O&G at surface loading rate of 0.37
gpm/ft2.
Polyethylene-60 degrees- Downward Flow: Total Suspended Solids vs Time (overflow rate: 0.37 gpm/sq ft )
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
time (hrs)
TSS(ppm)
I nfluent Effluent
Figure A11. Polyethylene 60 degrees downward flow: TSS at surface loading rate of 0.37
gpm/ft2.
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ERDC/CERL TR-00-40 31
Polyethylene-60 degrees- Downward Flow: Grease and Oil vs Time (overflow rate: 0.37 gpm/sq ft)
0
100
200
300
400
500
600
700
800
0 20 40 60 80 100 120
time (hrs)
TSS(ppm)
Influent Effluent
Figure A12. Polyethylene 60 degrees downward flow: O&G at surface loading rate of 0.37
gpm/ft2.
Polyethylene-90 degrees- Horizontal Flow: Total Suspended Solids vs Time (overflow rate: 0.37 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
time (hrs)
TSS(ppm)
Influent Ef fluent
Figure A13. Polyethylene 90 degrees horizontal flow: TSS at surface loading rate of 0.37
gpm/ft2.
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32 ERDC/CERL TR-00-40
Polyethylene-90 degrees- Horizontal Flow: Grease and Oil vs Time (overfl ow rate: 0.37 gpm/sq ft)
0
100
200
300
400
500
600
700
800
0 20 40 60 80 100 120
time (hrs)
TSS(ppm)
I nfluent Effluent
Figure A14. Polyethylene 90 degrees horizontal flow: O&G at surface loading rate of 0.37
gpm/ft2.
Polyethylene-45 degrees- Horizontal Flow: Total Suspended Solids vs Time (overflow rate: 0.37 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
time (hrs)
TSS(ppm)
Influent Effluent
Figure A15. Polyethylene 45 degrees horizontal flow: TSS at surface loading rate of 0.37
gpm/ft2.
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ERDC/CERL TR-00-40 33
Polyethylene-45 degrees- Horizontal Flow: Grease and Oil vs Time (overfl ow rate: 0.37 gpm/sq ft)
0
100
200
300
400
500
600
700
800
0 20 40 60 80 100 120
time (hrs)
TSS(ppm)
In fluent Effluent
Figure A16. Polyethylene 45 degrees horizontal flow: O&G at surface loading rate of 0.37
gpm/ft2.
Corrugated-angled ribs slanted away from f low: Total Suspended Solid vs Time (overflow rate: 0.37 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
time (hrs)
TSS(ppm)
Influent Effluent
Figure A17. Corrugated angled ribs slanted away from flow: TSS at surface loading rate of 0.37
gpm/ft2.
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34 ERDC/CERL TR-00-40
Corrugated-angled ribs slanted away from flow: Grease and Oil vs Time (overflow rate: 0.37 gpm/sq ft )
0
100
200
300
400
500
600
700
800
0 20 40 60 80 100 120
time (hrs)
G&O
(ppm)
Influent Effluent
Figure A18. Corrugated angled ribs slanted away from flow: O&G at surface loading rate of 0.37
gpm/ft2.
Corrugated-angled ribs slanted toward flow: Total Suspended Solids vs Time (overflow rate: 0.37 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
time (hrs)
TSS(ppm)
Influent E ffluent
Figure A19. Corrugated angled ribs slanted toward flow: TSS at surface loading rate of 0.37
gpm/ft2.
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ERDC/CERL TR-00-40 35
Corrugated-angled ribs slanted toward flow: Grease and Oil vs Time (overflow rate: 0.37 gpm/sq ft)
0
100
200
300
400
500
600
700
800
0 20 40 60 80 100 120
time (hrs)
G&O
(ppm)
Influent Effluent
Figure A20. Corrugated angled ribs slanted toward flow: O&G at surface loading rate of 0.37
gpm/ft2.
Corrugated-angled ribs slanted away from f low: Total Suspended Solids vs Time (overflow rate: 0.25 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 10 20 30 40 50 60 70
time (hrs)
TSS(ppm)
Influent Effluent
Figure A21. Corrugated angled ribs slanted away from flow: TSS at surface loading rate of 0.25
gpm/ft2.
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36 ERDC/CERL TR-00-40
Corrugated-angled ribs slanted away from flow: Grease and Oil vs Time (overflow rate: 0.25 gpm/sq ft )
0
100
200
300
400
500
600
700
800
0 10 20 30 40 50 60 70
time (hrs)
G&O
(ppm)
I nf luent Effluent
Figure A22. Corrugated angled ribs slanted away from flow: O&G at surface loading rate of 0.25
gpm/ft2.
Corrugated-angled ribs slanted toward flow: Total Suspended Solids vs Time (overflow rate: 0.25 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 10 20 30 40 50 60 70
time (hrs)
TSS(ppm)
I nf luent E ffluent
Figure A23. Corrugated angled ribs slanted toward flow: TSS at surface loading rate of 0.25
gpm/ft2.
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ERDC/CERL TR-00-40 37
Corrugated-angled ribs slanted toward flow: Grease and Oil vs Time (overflow rate: 0.25 gpm/sq ft)
0
100
200
300
400
500
600
700
800
0 10 20 30 40 50 60 70
time (hrs)
G&O
(ppm)
Influent Effluent
Figure A24. Corrugated angled ribs slanted toward flow: O&G at surface loading rate of 0.25
gpm/ft2.
Corrugated-angled ribs slanted away from flow: Total Suspended Solids vs Time (overflow rate: 0.49 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 5 10 15 20 25 30 35 40
time (hrs)
TSS(ppm)
In fluent E ffluen t
Figure A25. Corrugated angled ribs slanted away from flow: TSS at surface loading rate of 0.49
gpm/ft2.
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38 ERDC/CERL TR-00-40
Corrugated-angled ribs slanted away from flow: Grease and Oil vs Time (overflow rate: 0.49 gpm/sq ft )
0
100
200
300
400
500
600
700
800
0 5 10 15 20 25 30 35 40
time (hrs)
G&O(ppm)
Influent Effluent
Figure A26. Corrugated angled ribs slanted away from flow: O&G at surface loading rate of 0.49
gpm/ft2.
Corrugated-angled ribs slanted toward flow: Total Suspended Solids vs Time (overflow rate: 0.49 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 5 10 15 20 25 30 35 40
time (hrs)
TSS(ppm)
Influent Effluent
Figure A27. Corrugated angled ribs slanted toward flow: TSS at surface loading rate of 0.49
gpm/ft2.
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ERDC/CERL TR-00-40 39
Corrugated-angled ribs slanted toward flow: Grease and Oil vs Time (overflow rate: 0.49 gpm/sq ft)
0
100
200
300
400
500
600
700
800
0 5 10 15 20 25 30 35 40
time (hrs)
G&O
(ppm)
Influent Effluent
Figure A28. Corrugated angled ribs slanted toward flow: O&G at surface loading rate of 0.49
gpm/ft2.
Polypropylene-45 degrees- Downward Flow: Total Suspended Solids vs Time (overflow rate: 0.25 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 5 10 15 20 25 30 35 40
time (hrs)
TSS(ppm)
Influent Effluent
Figure A29. Polypropylene 45 degrees downward flow: TSS at surface loading rate of 0.25
gpm/ft2.
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40 ERDC/CERL TR-00-40
Polypropylene-45 degrees- Downward Flow: Grease and Oil vs Time (overflow rate: 0.25 gpm/sq ft)
0
100
200
300
400
500
600
700
800
0 5 10 15 20 25 30 35 40
time (hrs)
G&O
(ppm)
Influent Ef fluent
Figure A30. Polypropylene 45 degrees downward flow: O&G at surface loading rate of 0.25
gpm/ft2.
Polypropylene-60 degrees- Downward Flow: Total Suspended Solids vs Time (overflow rate: 0.25 gpm/sq ft)
0
50
100
150
200
250
300
350
400
450
500
0 5 10 15 20 25 30 35 40
time (hrs)
TSS(ppm)
Inf luent Ef fluent"
Figure A31. Polypropylene 60 degrees downward flow: TSS at surface loading rate of 0.25
gpm/ft2.
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42 ERDC/CERL TR-00-40
CERL Distribution
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Engineer Research and Development Center (Libraries)ATTN: ERDC, Vicksburg, MSATTN: Cold Regions Research, Hanover, NHATTN: Topographic Engineering Center, Alexandria, VA
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REPORT DOCUMENTATION PAGEForm Approved
OMB No. 0704-0188Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintainingdata needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reduthis burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22204302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of i nformation if it does not display a curvalid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.
1. REPORT DATE (DD-MM-YYYY)
12-20002. REPORT TYPE
Final3. DATES COVERED (From - To)
5a. CONTRACT NUMBER
5b. GRANT NUMBER
4. TITLE AND SUBTITLE
Designing Coalescing Oil/Water Separators for Use at Army Washracks
5c. PROGRAM ELEMENT NUMBER
5d. PROJECT NUMBER
62720A896
5e. TASK NUMBER
6. AUTHOR(S)
Gary L. Gerdes, Angelo DeGuzman, and Jeffrey Grubich
5f. WORK UNIT NUMBER
TB0
8. PERFORMING ORGANIZATION REPORNUMBER
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
U.S. Army Engineer Research and Development Center (ERDC)
Construction Engineering Research Laboratory (CERL)
P.O. Box 9005
Champaign, IL 61826-9005
ERDC/CERL TR-00-40
9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITORS ACRONYM(S)
CECW-EWU.S. Army Corps of Engineers
20 Massachusetts Avenue, NW.
Washington, DC 20314-1000 11. SPONSOR/MONITORS REPORTNUMBER(S)
12. DISTRIBUTION / AVAILABILITY STATEMENT
Approved for public release; distribution is unlimited.
13. SUPPLEMENTARY NOTESCopies are available from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161.
14. ABSTRACT
The U.S. Army has thousands of oil/water separators to treat wastewater from tactical vehicle washracks at active Army, Army Re-
serve, and Army National Guard facilities. The Army continues to purchase and install new separators when existing separators mus
be replaced, and when new vehicle maintenance facilities are being constructed. Most off-the-shelf separators being installed curren
are coalescing-type gravity separators.
No Army guidance exists, however, to help environmental and Directorate of Public Works personnel purchase coalescing separator
that are applicable to the high solids wash water at a typical Army washrack. Because Army guidance did not exist, and vendor guid
ance is not applicable, this study was conducted so that installation personnel, as well as washrack designers, have specific guidance
for the selection of off-the-shelf coalescing oil/water separators.
This research concluded in the following specifications for off-the-shelf, coalescing, oil/water separators: coalescer plate material polyethylene; maximum surface loading rate 0.37 gpm/ft2; coalescer plate angle 60 degrees; direction of flow downward at 60
degrees to the horizontal.
15. SUBJECT TERMS
oil/water separators, washrack, vehicle maintenance, tactical equipment maintenance, coalescers, waste water
16 SECURITY CLASSIFICATION OF: 17 LIMITATION 18 NUMBER 19a NAME OF RESPONSIBLE PERS