J UH 1
Kin K. Kox ami Vartor. fr. Lytic
Drinking Watet Kesearch Oiviston
United States Knvi. oiunuittal Protection Agency
Cincinnati, Ohio 45268
The Surface Wo'ei Tieat men t Halts { SWTR t1 uii
Mandated on June it, 1989 by the U.S. tnw lorunental
Protection Agency (USEI'A). This Hulw requires all
water utilities that use surface w^ers for their
source water for dniikmq w«tei to filter the water
before sending it out into the distribution systea.
Filtration is required to both remove pathogenic
Microorganisms that might be prevent and to reaove
particulates that could interfere with disinfection.
The rule lists the approved filtration techniques that
ha»e been denonettated in the past to be efficient
(conventional coagulation/filtration, direct
filtration, slow sand filtration and diatomaceous earth
filtration). Allowances in the SWTR are Made for
alternative techniques such as Membrane filtration and
cartridge filtration. The alternate technologies Must
demonstrate that they are capable of removing 99
percent of particles in th«s 5-15 pat range and meet a
0.5 MTU turbidity limit. The stringent requirements of
the SWTR are to provide a pnsiary barrier (filtration)
and a secondary barrier (disinfection) to protect the
public frost pathogenic surface water source. Recant
events "lave reinforced the need to Maintain and operate
filtration system:* (itopuily for tte&ting rti jinking
In April of 1993, Milwaukee, Wisconsin Mcame .he
Major focus of the drinking water industry. The focus
of attention centered on the large increase in reported
cases of diarrheal patients throughout the city.
Shortages of ovei-the-countei medications for diarrhea
control were also seen at local phaiir.acies. Although
other organises may have been involv-rt, the major
increase in diarrhea was determined to be caused by the
otganisn Cryptosporidium. Ensuing investigations were
conducted by City, State, and Federal officials. These
investigations suggested that drinking water may have
been partially respond ; l>ie to r disti ihutmg the

—,va« a am m Milwaukee and ~ !>«• suriounding area. Random
digit phone dialing surveys wen? conducted. These
sutveys indicated that 403,000' p«ople were affected
Ehad tii*trhea> during the incident, The Milwaukee
Watrat Utility pumps water for Approximately 800,000
pcn|l|p. *
i.'KY I'TO^l'OR ID K'.*? J S.i>yTn«KAK
On April h, a local Milwaukee doctoi ordered a
parasitic analysis on a feeaI specimen from one ol his
j.«tienti». Crvptosporidiuw was detected in the fecal
smear. At that tine, local and state officials were
notified of th« Cryptosporidium detection. A concurrent
survey of diarrhea cases in loc.il nursing hones was
conducted. Tins study indicated that thf* residents in
nursing homes in the southern part of the city were
fourteen times wore likely to have had diarrhea than
those in the northern part of the city. Nursing home
populations were used in this study because nursing
home populations were thought to bo less likely to have
travelled around the city. Thus, they would have
«.-*posed only to the environment within the nursing
iobw. The City of Milwaukee is servml by two water
t Hutment plants.' The Linwood Plant sexves basically
ihe northern part of the city, while the Howard Ave->u«»
Plant serves the southern pait. Concurrent data on
tieatment efficiency at the Kowaid Avanue Plant and the
Nut sing Home study suggested that the Howard Avenue
Plant was suspect in the disease outbreak.
The Howard Avenue Water Treatment Plant (HWTP; was
ordetod closed dui ing the ensuing investigation and
1,.ji I water ui'lor was i»su«nt foi tlx- community. "fh«-
l.i(iwood Plant is capable of tr»»at iti«i enough water to
serve the community during the i*t<- winter and early
spring months. Both plants art needed during high
water usage periods such .is in the stw\»t.
As a result of the boil watei order, drink?ng
water fountains, ice machines and other devices that
used drinking water were shut down. There was a run on
bottled water supplies at local markets. Local
restaurants served canned soft drinks and juices
without ice. Bottled or on-site processed water
(boiling or filtration} was used for washing salad
ingredients and made available to customers. Thf»
tollow up surveys indicated that ,»s many as 403,00uj
individuals experienced diarrhr»a.
Cryptosporidium is a piotoroan that if ingest«»d by
a healthy adult human may cause some discomfort such as
that felt with stonach flu. However, it can be lif>»
threatening to others such as infants, AIDS patients
and th*. elderly. Research has shvwn that most sur I •»<-«?
waters are contaminated with this parasite.*
at<* vet3f lesistant to
chlormatjon and, therefore, t lie it effective removal
from surface waters is highly dependent on the
operation of a filtration facility.
Cltv	thZ initial ¦ *¦» t*' piUvide
Mate?"" * ' " fr"" ' h *«»"*« With filtration
hv	,e re,r:,val o1 Cryptosporidia
oocysts by filtration vent to Milwaukee, The teas
concentrated its efforts on evaluating the operational
available from the southern Howard
h£ ?fr£ In	'MBt' Th" ',OJl wa* to *«•••
¦ay nave passed through the water trrdtseni facility.
As part of the KPA Assistance, the team called
Qpon research previously sponsored o*- conducted by the
££? ™^Kin9	f*»* dr.nkmg water.
This research included botU extramural ar.d in-house
laboratory and pilot plant filtration studies. Both
the in-house studios „nd th*» field studies have
indicated that good ~urbidity an1 particulate r«*oval
drinking'wjtter f°*
fLAirr msprcTTftM
fauJLc® w"*r ^r Milwaukee, Wisconsin, is take
city's water is treated at two water
treatment facilities: the northern situated Lmwood
treatment plant and th« »onttwin n< iw.ii n».
plant. Both treatment facriliti.es t i«»at Lake Michigan
water by conventional water treatment processes
(coagulation, sedimentation, f sItiation, and
disinfect ton). The Linwood facility has a water
treatment capacity of 275 million gallons per day (HGD1
and the Howard treatment facility has a filtration
fffl *v ? 100 MGD- Du«"i"g typical operation, the
Liswood plant supplies the northern 2/3 of the water
district. The Howard plant supplies the reMiiting 1/3.
A large mixing zone exists in the distribution system
between the two treatment facilities, but the general
f ,mt of water is northern or southern. The initial
investigation linked the cryptosporidiosis outbreak to
drinking water treated at the Howard treatswnt
facility, resulting in temporary shutdown of the
facility. The EPA team focused its efforts on
understanding the operation ol the Howard treatswnt
The Howard Plant is a conventional coagulation,
sedimentation, filtration facility (Figure I). A
complete description can be found in the literature *

!*•*». i ... i I.,.. iv.,1 »uUnl usotl until
a 1 ura : .1 i ii11 '»m ; u I 1.11 } *h:i* «	* .t ,u i »»¦ v. *
Auqusl «>1 1°»2. 1'' Au<|i.st of 1. * •'»> IaJ;1 y. , .
Swm-hed to H,lyal..ThJoti.i-	The sw, c o
l«ACt was d<>n.» with th'> 1*1»«t 'hat .» benefit of high
r'inishwd wat.-i pit toi coriosion rem? ioI would>*>« "f* »•
woll as »Ptlur <*ti s lmly** volume an,i impioved ci i' .iniitioiis. Detore
iltchlm, to W... ,h~ n„	with
Mnuf-'-'-ir-., wi-..-n„K„, nun, ..vt '•< <,.-» cejw«iti"<«
M.r-«»ivui.| I >»' Ml 'H'imi v.H-'i Hit nsistent ly
t.io.1u.-Hiy a J<>' «>f fluent i. n I wlu y vate: (daily
Sw,of 0., iriu or	UUM..-I the period o
*«'•!. !H ifi» '<•"> "M>1 !ih,,v <,OW° P *'
! i' ,,w:.n -in,		 «•"»T?
i.iulilv v.i«i-i»il"	1 ! """	°-1 n,ld '*? .
Til- i-.n w.s .. >-.i "• '•><>'¦ wl.at_r«us.-.l
1-V..IS To .	At all times
Juri,. I » I,IS I..1 K.'l, "IflU'l.t	*«««.
wg,,i '• - fi.1 Hi: W-. .-.ml 1W«1 tl»- V;\sconsln UNR
: fqulrilicnr- toi * u idi'y.
Th»» SIWTF	"« highly	quality of
influx.I ««- ---- rs ,«
thtouqh '»•" .i;1-'":. ,	U'. ; mIiuy l*volS ram,...I
T/1«VV T<.tf.. in		 <«»•»« iy
I. < • 1 n/ 10) m>. to „ —« v»0 CFU/100 ml. in
r I I •»! I lii-it"	s..«plos were
,^tivn J-'i oc i ili.imr,. Av.«au«« 1 ,l'' wa\"t	•
lev.»^ f- I pi t?vi. 'U^ months	•ui.ui.d i ot 4 tlTU
,nf X,„ ,:t coliu-^ ».-vMs -JO .-V.rtH,
I.lHlli'l 'In- I »«.'• I" l"'l ' ' 1 ' '' '' I"',,nt
t.i.i I»• *,' 		 i «•« | ¦* ¦»•• !•** i «¦>	.-Jiflwr" «y
,1(1 just Hl'I .•«*.)« I.tl.t I.,<•«.:. • "¦
„,1 )usr.M>nls wor- alr.n m.,U- to .-..n.,-.%.¦»*« lo.
.•oaquUtion .!.h,.i.'N	U	 '	and m0.2 NT",
h t -re achieved in previous months (Figure 2)-
sn. ,Pp.^«i -i." "¦"«,?* "f"""
* .. , , « • > i j»r *' aw W'tt oi enrtd ltiOliS i
1"9a^9	t , tuibidit i was when t ,i«	l	> •
set,ou >	.	-#	lii" i improvements JR
..uiy	"»
la fully capable of producinq low turbidity watar (<0.1
MTU) «ind«r aptinal ciimical coagulation conditions
(i.«. do*aq«a applied). The low effluent turbidity
value* can even be aet when the plant ia challenged
with high turbidity raw water.
There are several factors that nay have increased
the tiaw to reach the optimum coagulant doaagea for low
filter effluent turbidities during thin tiaw. One of
theae factors nay include a lack of historical use
recorda foe PACL. The previous coagulant had been used
for alaost thirty years. The new coagulant had only
been used for & short time and the Historical records
were not fully developed. The optiaum cheetical doaaoea
were sought through laboratory testing and consultation
with DHR and cher.ical supplier to ac hieve the lowest
turbidity possible. The coagulant adjuatamnts were
aede based on all available data.
Another important factor ia the tiae required to
see a result, in the treat*.* water quality after
chemical adjustment, witn a short residence tiae for
the water in the plant and a rapidly changing influent
water quality, dosage optiaixation was difficult.
During i.h« higher effluent turbidity episodes,
greater nuabers of particulates passed through the BUT*
as evidenced by tna higher turbidity values exiting the
plant clearwell. Although a greater i.uci^i of
particulates passed through the plant, thi* does not
secessarily aean that Cryptosporidium •	< <
counting of these organisms is difficult since membrane
filtration, elutiun and then a microscopic counting is
inquired. To detect low concentrations of these
organisms, large volumes of water must be filtered
through membrane filters with very small pores. With
waters that contain other particulate matter, the
membrane filters are slow and iray clog to a point where
no more water will pass. Tfius, men;, o: 1 nu directly for
Ci.itdia or ?typtosporidiuw is difficult and eona type
of sulfonate is preferred.
Radioactive labelled aciylic beads wet e on®
sui loqate that was used in the pat-t for some Ciardia
filtration studies. Th«-- • »r of beads could be
quantified by counting the adiation. Another nor«
rommon surrogate is particle counting. In particle
counting, influent and affluei.t water samples can be
analyzed for both number and siz* of particles. The
percentage of particles removed in specific size ranges
ran then be compared to actual organism counts taken
The Drinking Wato Research Division (DWRD) of the
USFPA has conducted, ana is conducti.vj, laboratory a.id
pilot plant studies oa removing microorganisms from
drinking water. Current efforts are focused on
removing Cryptosporidium oocysts. Although current
et torts are rente;ed on Crvptospo;idiu« removal,
coincidental removal of other 01catisms (total
coliforma| is also being evaluated. Concentration and
microscopic counting is being use-;, but particle
counting is being used more intensely to gather as much
information as possible. In addition to the filtration
studies, charqe/attachment studies are also being
conducted to look at the leta Potential of the
ojq.inisms as they ar«» subjected to the rigors of a
water lieatment plant.
The DWRD has pi lot-scale wat«»i treatment
facilities located at ti.e Cincinnati labo"-- _ot y. The
pilot plant contains a 2 gpm conventional
coagulation/settling filtrati"-. system that has
capabilities of bypass>r;; a«ctions to do direct
filtration, a slov sand filter (2,25 ft-' surface area),
and diatomacaous earth filter (1.0 ft1 septum).
Various waters can be brought to the treatment facility
>,o challenge the filter units with varying water
qualities. To increase the microbiological content of
the source waters, raw municipal sewage (1 gallon per
5,000 gallons of raw water) is occasionally added to
the water prior to treatment. Specific organisms of
choice are also spiked into the water to achieve levels
desired. The specific organisms are cultivated inhouse
and aie grown in broths, on agar, or in aniflMls (if
required). Cryptosporidium oocysts (for example) are
harvested from the fecal material of infected mice (for
C« mil) or infected calves (for c. parvuml.
The pilot plants are operated in both continuous
and Intermittent modes to evaluate removals during
tonal operation and und^i stress conditions to the
¦fete*. All systems ar« ^ested at high and low
concentration of the de„tred organism and evaluated for
¦any parasMters. These parameters include medi.« type,
water filtration rata, temperature, chemical
concentrations, chemical type, and more. Water samples
are collected frosi various points within each
filtration system and analyzed for desired parameters.
*i—s of the specific paraaieters include monitoring
particulate counts and sizes.
Chemical addition is used in many filtraf.ic**
•Titan to alter the charge on the particles (. anqing
•he attachment efficiency) and allowing the particles
to be more readily removed. The zmtm potential of the
microorganism of choice was measured using a LazerSee
Hater. The zeta potential will relate to the amount
and type of chemical to be used.
In early studies Cryptosporidium parvus cocysts
(stored in dichromaLe)	used in jar test studies.
The initial jars were spiked with 10,000 ooeysts/liter
and the water subjected «-o coagulation, floccnlation
and settling. The supernatant f.ost th« settling
process contained 1,000 oocysts'liter (90% reduction).
Tests with fresh oocysts at > ho dame coagulation doses
only exhibited 50* , .auction in oocysts. Although
these tests preliminary, there does appear to be
subs'-s.-.nal differences between fresh and stored
One of the conventional coagulation/filtration
pilot plant systems was challenged w.th a source water
containing 100,000 oocysts/liter. The filter effluent
was monitored for oocysts and 99 percent resnval of
preserved oocysts were routinely seen. The pilot slow
*aad filter was also challenged with water containing
100,900 oocysts/1 iter. Effluent concentrations were
consistently below 1,000 oocysts/liter and in s»st
cases less than 200. The filter was ponitored two
weeks after the spiking stopped and no cysts were found
ia a fifty gallon sample of the effluent. Particle
i Mint showed a removal of around 961 of particles in
the 2.S to S|ia range. In all these tests, the percent
total particulate removal measured by particle
counters, was less than the percent removal of oocysts.
Slow sand filter tests were conducted with

Cryptosporidium by Ghosh* at Pennsylvania State
University. These tests showed thro® log removal
through the filter during ripening and wore than four
log reduction on a fully ripened filter. Ghosh
conducted several experiments using various grades 01
diatomaceous earth on a precoat filter. Observed
removals exceeded three log removal for all runs but
removal %#a» dtpend*ant on DE grade. The *arg«r the
grade, the ssore oocysts found in the effluent. All 01
these studies were conducted with seeded oocysts that
were inactivated with formalin before seeding.
Zstm potential measurements were wade in DWRD labs
using clean suspension# of gryptpspyrjdoocysts
(both muris and parvumj. The oocysts suspensions were
diluted into a river water that had been filtered
through l»m sentorane filters. Tests were conducted to
evaluate variables such as age of oocysts, storage
solution, and pH of suspension fluid on oocysts. Huns
oocysts were highly variable in regard to leta
t>otentjal as the charge increased from -21 mv to
mv as the pK was lowered from 10.0 to *.i i«utis
oocysts were not stored in 'ii :.;>tum«ite). Maris oocysts
stored in dichron-atc nad a considei ,ible greater charg»
magnitude than t,o,. in clean suasions (-31.1 versus
-20.1 mv, respectively). The parvum oocysts displayea
a change from -17.8 mv C»n clean suspensions) to -2S..'
spw in suspensions stored in dichromate. in one study,
the fecal suiterial from a call wis stored in dichromate
tor twei*e hours until the material could be processed
the next day. The oocysts were harvested and stored
without dichrornate. Twenty-four hours after
preparation, the measured charge was -i mv. The
suspension was monitored for eight days and the charge
gradually changed to -14.1 mv. There weie not enough
oocysts to continue the study to determine if the
charae would recover to -17,8 mv seen with soit irein
oocysts. Zeta potential studies by Ghosh showed values
5 sr.v more negative than the results in the EPA tests
with preserved oocysts.
The preliminary tests have indicated that most
filtration systems are effective in removing 3 logs of
oocysts under ideal operating conditions. These tests
for the most part have been done with oocysts
in dichromate or with foraalin fixed oocysts. Both the
preservation solution and the fixation fluid have shown
an effect on the measured leta potential end may jj*v"
an effect on the rigidity of t.ie oigatiism. The few
studies completed with fresh oocysts have shown less
effective removal but more work iB Plan^d*	t_
surveys* in the literature have indicated that «^V*1
are passing through some filter plants. The p.as <1
oocysts may indicate that fresh (or untreated) oocyst.
«y bo "ore difficult to remove than those that are
pretrested by iom manner. The preservation processes
¦•y affect the physical characteristics of the oocysts
and say make them more susceptible to filtration
processes than those in the natural environment. The
0MN> has future studies planned looking at oocyst
rsaoval taking all the preliminary information into
The team from EPA's Drinking Water Research
Division presented information that suggested that the
passage of Cryptosporidium through the Howard Water
Treatment Plant may have happened with the passage of
other particulate matter (increase in turbidity),
teteal passage of oocysts diring this time frame will
aerver be able to b* proven analytically. Samples were
sot teken during that time. The available data does
Stt99«»t that oocysts passage could have occurred. In
0NN>*s earlier research, good turbidity restoval was
essential to achieve good Cryptosporidium oocysts
removal. The recommendation made to the City of
Milwaukee by the research team emphasized the
iaportance to strive for optimal turbidity reduction at
all times.
In order to achieve good reduction in turbidity at
all times, stringent controls on coagulant/flocculant
dosages are required. This control could be automated
or done by operator attention and that determination
would be at the discretion of the water utility.
Subtle changes in effluent turbidity from a filtration
pleat may result in large changes in particulates
passing through the filters that may or may not be
associated with pathogens. The goal therefore, should
be to remove these particulates and not. h«ve to worry
about whether or not they are of concer ».
The suggestions made to the Milwaukee Water
Treatment Plants are simple ones, but are ones that can
bees significant impact if they are not acted upon.
The authors want to acknowledge the cooperation
Md assistance provided by all individuals involved
witH the investigation of the disease outbreak. Vhesw
iadi vidua Is include the many City of Milwaukee
employees that were available to answer any question*
we poeed and provided all data we requested.
Assistance wes also provided by representatives f rosi
CDC, IDA, and Wisconsin State Agencies. The
investigation could not have been cosqpleted without the
fsauiite cooperation of these groups.
M (

1.	OS EPA, Hational Primary Blinking Mater
Regulations; Filtration and Disinfection. Federal
Register 54(121): 274B6-27541, 1989.
2.	Edwards, Diane P., "Troubled Waters in Milwaukee",
ASM News, Vol 59, number 1, 1993.
I. City of Milwaukee, "1991 Amiii.il Report", Watri
Knqineerinq Division, 1 9. Fox, Kin R. ar.u !.ytle, Darren A. {1993b) "The
Milwaukee Cryptosporidiosis Outbreak*
investigation and Recommendations", Proceedings
AWWA Water Technology '.onferenc* , Miam, Florida.
chosh, M.M., et al. ( 1989). "Field Study of
Ciardia and Ctvotospor idiuw Removal from
Pennsylvania Surface Waters by Slow Sand and
Diatomaceous Earth Filtration*. Environmentai
Resources Research Institute.

(Please read instructions on the reverte before completim
3. ri
«. title and subtitle Cryptosporidium! The Milwaukee
Experience and Relevant Research
S. tWO*- ->ATE
6. PER
7 autmobui KiK R. Fox and Darren A. Lytle
U.S. Environmental Protection Agency
Drinking Water Research Division
Risk Reduction Engineering laboratory
Cincinnati, OH 45268	
11 6ontract/g*ant NO
Risk Reduction Engineering Laboratory—Cincinnati,
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati^ OH 45268	

Kim Pox (513) 569-7820 Anwrican Water Works Association
Proceedings of the 1994 Annual Conference on Water Quality, 6/19-23/94,
New York, NY, d;505-514
i6. abstract -p.,* Surface Water Treatment Rule (SWTR) was mandated on June 29# 1989 by the
U.S. Environmental Protection Agency (USEPA). "This Rule requires all water
utilities that use surface waters for their source water for drinking water to
filter the water before sending it out into the distribution systom. Filtration is
required to both remove pathogenic microorganisms that might be present and to
remove particulates that could interfere with disinfection^ The rule lists the
approved filtration techniques that have been demonstrated in the past to be
efficient (conventional coagulation/filtration, direct filtration, slow sand
filtration and diatomaceous earth filtration). Allowances in the SWTR are made for
alternative techniques such as membrane filtration and cartridge filtration. The
alternate technologies must demonstrate that they are capable of removing 99 percent
of particles in the 5-15 pm range and meet a 0.5 NTC turbidity limit. "Hie
stringent requirements of the SWTR are to provide a primary barrier (filtration)
and a secondary barrier (disinfection) to protect the public from pathogenic
surface water source. Recent events have reinforced the need to maintain and
operate filtration systems properly for treating drinking water.
e. COS ATI Field/Group
surface waters, drinking water

20, SECURITY CLASS (This pig*I
CPA Pan* 1220-1 (Rev. 4-77) previous coition t« omoliti