ows designing

8/13/2019 Ows Designing

1/43

Approved for public release; distribution is unlimited.

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


2/43

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.


3/43

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


4/43


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


5/43


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


0.37 gpm/ft2.........................................................................................................26


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


6/43


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


rate of 0.25 gpm/ft2..............................................................................................35


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


rate of 0.49 gpm/ft2..............................................................................................37


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


0.25 gpm/ft2.........................................................................................................40


0.25 gpm/ft2.........................................................................................................40


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


7/43


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.


8/43


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


9/43


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.


10/43


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


11/43


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


12/43


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.


13/43


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.


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


14/43


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.


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.


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


15/43


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.


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


16/43


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.


17/43


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.


18/43


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.


19/43


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


20/43


Top View

(plates perpendicular to page)

Flow

(corrugated plates

parallel to page)

Flow

(corrugated plates

parallel to page)

Flow


Flow

45


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)


21/43


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


22/43


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.


23/43


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.


24/43


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).


25/43


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.


26/43


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


gpm/ft2.


27/43


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


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.


28/43


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.


29/43


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.


30/43


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.


31/43


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.


32/43


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.


33/43


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.


34/43


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.


35/43


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


gpm/ft2.


36/43



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


gpm/ft2.


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


gpm/ft2.


37/43



0

100

200

300

400

500

600

700

800

0 10 20 30 40 50 60 70

time (hrs)

G&O

(ppm)

Influent Effluent


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


gpm/ft2.


38/43



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


gpm/ft2.


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


gpm/ft2.


39/43



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


gpm/ft2.


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


gpm/ft2.


40/43


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


gpm/ft2.


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"


gpm/ft2.


41/43


42/43


CERL Distribution

Chief of EngineersATTN: CEHEC-IM-LH (2)

ATTN: HECSA Mailroom (2)ATTN: CECC-RATTN: CECW-EW

Engineer Research and Development Center (Libraries)ATTN: ERDC, Vicksburg, MSATTN: Cold Regions Research, Hanover, NHATTN: Topographic Engineering Center, Alexandria, VA

Defense Tech Info Center 22304ATTN: DTIC-O

106/00


43/43

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

ows designing

Documents