The Bacteriological Aspects of Stormwater PollutionAuthor(s): E. E. Geldreich, L. C. Best, B. A. Kenner, D. J. Van DonselSource: Journal (Water Pollution Control Federation), Vol. 40, No. 11, Part I (Nov., 1968), pp.1861-1872Published by: Water Environment FederationStable URL: http://www.jstor.org/stable/25036149Accessed: 01/07/2010 11:50

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THE BACTERIOLOGICAL ASPECTS OF STORMWATER POLLUTION

E. E. Geldreich, L C. Best, B. A. Kenner, and D. J. Van Donsel

There has been a growing concern

in recent years with the pollution con

tributed to streams from stormwater

drainage. Earlier bacteriological an

alysis of separate and combined sewer

systems measured only the total coli form population present in this pol lutional source (1) (2) (3) (4). Re cent studies on the origins of fecal coliforms and fecal streptococci have

generated renewed interest in these

groups as better indicators of pollu tion by warm-blooded animals than

the total coliform group traditionally used in stream pollution investigations

(5). Using additional bacteriological pro

cedures, Weibel et al. (6) determined that 90 percent of all stormwater sam

ples from a separately sewered urban area had counts of total coliform, fecal coliforms, and fecal streptococci exceeding 2,900, 500, and 4,900/100

ml, respectively. Burm and Vaughn

(7), in a bacteriological comparison study of combined and separate sewer

discharges also used these three bac

teriological parameters. They found

the total coliform densities in the sep arate storm sewers to be approxi

mately one-tenth of those in combined sewers where median monthly values

were as high as 37,000,000 coliform

E. E. Geldreich and D. J. Van Donsel are

Research Microbiologists, National Water

Supply Research Laboratory, U. S. Public

Health Service, Cincinnati, Ohio. L. C. Best

is Microbiologist, Technical and Advisory

Investigations Activities, FWPCA, Depart ment of the Interior, Cincinnati, Ohio. B.

A. Kenner is 'Research Microbiologist, Waste

Identification and Analysis, Cincinnati Water

Research Laboratory, FWPCA, Department

of the Interior y Cincinnati, Ohio.

organisms per 100 ml. Fecal coli form densities were approximately 20

percent of the total coliform in com

bined sewage. Analysis of their data indicated the fecal coliform content of separate systems to be 7.6 percent of the total coliform population. They also reported that discharges from the combined sewer system have fecal

streptococcus densities about twice as

great as those from the separate storm

system (508,000 vs. 208,000/100 ml).

Although there now is available ex

cellent quantitative data to demon strate the magnitude of stormwater bacterial pollution densities, the sur

vival and persistence of these orga nisms in stormwater as related to sea

sonal temperatures and nutrients avail

able, the probable sources of the fecal and nonfecal pollution, and the fur ther evaluation of the potential health hazard by quantitative pathogen de tection have not been reported. These areas were selected for the develop

ment of this research project.

Methods

Stormwater w7as collected at selected locations along suburban street gut ters and from a storm sewTer outfall

that drained a small portion of a

wooded hillside bordering a city park. Standard manual sampling procedures

were used. At two other locations where drainage from a suburban busi ness district and agricultural land was studied, sampling was pro

grammed by automatic equipment pre

viously described by Weibel et al.

(6). All samples were examined for total

1861

1862 JOURNAL WPCF November 1968

coliforms, fecal coliforms, and fecal

streptococci by the membrane filter

(MF) technique with the use of M

Endo MF (8), M-FC (9), and KF

Streptococcus (10) media, respectively. For quantitative recovery of Salmo nella in stormwater, a 48-hr selective

growth procedure involving 41 ?C in

cubation and the MF technique was

used. Following sample filtration, the MF was first cultured for 18 to 24 hr on double-strength selenite bril

liant green sulfa medium for pre

liminary selective enrichment, then

transferred for final incubation and

differentiation on double-strength

xylose lysine brilliant green medium

(11). All suspected Salmonella colo nies were checked further for cultural

purity, for biochemical reactions to

selected tubed media to identify Salmonella, and finally, by serologi cal procedures, to verify Salmonella

species.

As background data to the study of bacteria present in stormwater run

off, samples of rainfall were taken from a location atop an eight-floor

building in a residential and light in

dustrial area. These samples were

collected in sterile stainless steel pans

placed in position at the start of rain

fall occurring during normal working hours. Volumes analyzed varied from 100 to 500 ml per test depending entirely on the amount of rainfall col

lected in a given storm.

Survival studies of pollution indi

cator strains and Salmonella typhi murium were made with the storm

water and rainwater samples collected in the four seasonal periods. Such

samples were sterilized by MF filtra

tion and split into four equal portions. Individual portions were inoculated

with different strains of organisms consisting of a coliform (-h + IMViC type), a fecal coliform

( + + -- IMViC type), a Strepto

coccus faecalis var. liquifaciens strain, and a S. typhimurium culture. Incu

bation temperature of 10? and 20? C, which represented the ones nearest to

the original water temperature re

corded at time of sample collection were used. All inoculated water sam

ples were examined at 1-, 2-, 3-, 7-,

and 14-day periods for the bacterial

density remaining. In the investigation of the fecal

material from cats, dogs, and various

rodents, procedures previously em

ployed (12) were used for quanti tative measurement of the pollution indicators present. In addition, pure culture studies were conducted on the various coliform and fecal strepto coccus strains isolated to determine the

percentage distribution of types.

Results and Discussion

Seasonal Variations in Stormwater Pollution

Stormwater examined from city streets, a suburban business district storm drain, and a wooded hillside

adjacent to a city park all had a

bacteriological composition similar to

stormwater runoff collected from cul tivated farm fields. In a study of

median values, seasonal differences in the bacterial densities for total coli

forms, fecal coliforms, and fecal

streptococci were noted for the data from the four stormwater sources

(Table I). Total coliform peak densi ties for urban locations (wooded hill

side, street gutters, and suburban busi ness district) occurred in autumn.

This also was noted for fecal coliform

and fecal streptococcus densities in

urban street gutters and business dis trict stormwater runoff. These latter

two indicator systems, however, reached an earlier peak (summer pe

riod) for stormwater runoff collected from the wooded hillside.

In drainage from rural stormwater

runoff, the possible existence of sum mer and winter peaks in bacterial indicator densities was demonstrated.

These peaks may be related, in part, to more lateral drainage during the summer growing season and the win ter period of frozen ground condi

Vol. 40, No. 11, Part 1 STORMWATER POLLUTION 1863

TABLE I.?Seasonal Variations (Median Values) for Bacterial Discharges in

Stormwater and Rainwater from Suburban Areas, Cincinnati, Ohio, and in

Agricultural Land Drainage, Coshocton, Ohio

Date Total Samples

Season Total Coliform

Fecal Coliform

Fecal Strep

tococcus

Ratio FC/FS

Feb. 62 to

Dec. 64

Jan. 62 to

Jan. 64

Apr. 62 to

Jul. 66

Jan. 63 to

Aug. 64

Jun.65 to

Feb. 67

278

177

294

94

49

Spring Summer

Autumn

Winter

Spring Summer

Autumn

Winter

Spring Summer

Autumn

Winter

Spring Summer

Autumn

Winter

Spring Summer

Autumn

Winter

2,400 79,000

180,000 260

1,400

90,000 290,000

1,600

22,000 172,000 190,000 46,000

4,400 29,000 18,000 58,000

<1.0

<1.0

<0.4

<0.8

190 1,900

430 20

230 6,400

47,000 50

2,500 13,000 40,000

4,300

55 2,700

210 9,000

<0.3

<0.7

<0.4

<0.5

940 27,000 13,000

950

3,100 150,000 140,000

2,200

13,000 51,000 56,000 28,000

3,600 58,000

2,100 790,000

<1.0

<1.0

<0.4

<0.5

0.20

0.70

0.03

0.02

0.07

0.04

0.34

0.02

0.19

0.26

0.71

0.15

0.02

0.05

0.10

0.01

tions. In the spring and autumn,

however, land cultivation results in

greater downward migration of wa

ter, with its associated bacteria, into the soil and groundwater table.

Fecal streptococcus densities were

consistently higher than fecal coliform levels in all four different sources of stormwater runoff. The highest me

dian value for fecal streptococci

(790,000/100 ml) occurred in the rural runoff during winter. A me

dian value of 47,000/100 ml repre sented the highest fecal coliform

density and this occurred in storm

water discharges from street gutters

during autumn. Fecal coliform to

fecal streptococci ratios were less than 0.71 in the four separate storm sewer

systems.

The fecal coliform segment of the

total coliform population in all 843

stormwater samples averaged 8.6 per

cent; a 21.1-percent maximum value was reached for those samples col

lected in autumn from the suburban

business district. Fecal coliform per

centages for all other seasons from

that source and the other stormwater sources were less than 16.5 percent,

with rural spring and autumn sam

ples containing only 1.3 and 1.2 per cent fecal coliforms. The autumn

samples from the wooded hillside con

1864 JOURNAL WPCF November 1968

tained the least amount of fecal coli

forms, only 0.2 percent of the 180,000 total coliforms per 100 ml.

Rainwater Contamination

Infrequently rain or snow falling to the earth is contaminated with traces of matter and occasional bac

teria acquired via air-borne particu lates. Pollution indicator counts for

rainfall were generally less than 1 per 100 ml as demonstrated by the median

values in Table I. There were 7 indi

vidual storms during the two summers,

however, that had total coliform densi

ties between 1 and 92/100 ml. One of these rain samples had 1 fecal

coliform per 100 ml and two samples contained 1 and 2 fecal streptococci per 100 ml, respectively. These orga nisms may have been associated with

soil particles or insect or vegetation

fragments found on microscopic ex

amination of debris trapped by the

membrane filtration method used in

the bacteriological examination of

these rainwater samples.

To demonstrate further the low bac

terial nutrient levels characteristic of

rainwater, the distilled water suitabil

ity test (13) was used to compare the

relative magnitude of nutrients avail

able in rainwater with those available

in triple-distilled water. These data

presented in Table II, representing an

average of 34 individual determina tions for the four seasons, were com

pared with a similar examination of 15 triple-distilled water samples. Ke sults indicate a detectable increase of the nitrogen content in rainwater dur

ing the spring and summer months.

The detectable carbon content de

rived from possible organic contami nation was minimal during all sea sons. As a reference point, significant bacterial nutrients in distilled water that will support growth would have a nutrient ratio above 3.0, as detected

by the distilled-water suitability test. The highest nutrient ratio for rain water examined in this study was 2.6 ; this occurred during the spring

months and was associated with the increased incidence of combined dust and rain showers.

Soil Contribution

Because rain falling to the earth contains insignificant bacterial con

tamination, the major contamination of this basic water source then must occur on contact with the polluted land environment. Soil in areas re

mote from man and his culture re

ceives insignificant levels of occasional contamination from wild animals and,

therefore, generally does not contain

TABLE IL?Relative Magnitude of Bacterial Nutrients in Rainwater

Compared with Similar Values for Triple-Distilled Water

Rainwater

Number of Samples

Sample pH

Nutrient Ratios

Relative Values

Nitrogen

7

10

9

Median

4.5

5.6

5.6

5.6

2.6

1.6

1.1

1.6

5.3 1.7

0.93

0.83

0.59

0.49

0.71

Triple-Distilled Water

15 6.8 0.8 0.21

Vol. 40, No. 11, Part 1 STORMWATER POLLUTION 1865

TABLE III.?Occurrence of Nonfecal Coliform IMViC Types in Soils, Stormwater, and Streams

Soil Samples

Total Strains

Percent Occurrence

Urban Stormwater

Total Strains

Percent Occurrence

Untreated Surface Water

Total Strains

390 75

7 1,109

80 181 157 61

4 1

53 6 0 0

0.4

18.3

3.5

0.3

52.0

3.8

8.5

7.4

2.9

0.2

0.1

2.5

0.3

10

106 7 0

156 45

203 26 34

2 2 2 0 0 0

1.7

17.9

1.2

26.3

7.6

34.2

4.4

5.7

0.3

0.3

0.3

86

1,507 136

18 971 373 469 443 229

6 49 23 0 0 0

2,132 593 4,310

Order of

Frequency

- +

- +

--+ + - + + +

-+ + + - +

- +

- + +

-- + +

- +

- +

-+ + +

any fecal coliforms (14). In con

trast, soil in areas populated by man, either on farms or in cities, receives

varying levels of warm-blooded-ani mal pollution from humans, pets, farm

animals, and rodents. As a result, soil contributes fluctuating densities of fecal contamination to drainage wa

ter, the amount being related to the

intensity and frequency of soil pollu tion. Survival of pollution indicators and any associated intestinal patho gens in soil and their possible transfer to stormwater is related to many fac tors (15). Some of these factors in clude sunlight exposure of the soil, temperature, frequency of rainfall, soil moisture, soil pH, organic matter,

frequency of recontamination of a soil

site, and the presence of competing or

antagonistic organisms in the soil en

vironment.

Analysis of the data presented in Table I indicates that fecal pollution accounts for an average of 8.6 percent of the median total coliform bacteria

present in stormwater examined.

Logically, the remaining non-fecal coliforms are assumed to be con

tributed to stormwater and the re

ceiving stream from the soil environ ment. To test this hypothesis, all

non-fecal coliform IMViC types from 251 soils widely distributed geographi cally (14) were compared with simi lar coliforms from untreated surface

water supplies for 14 major cities

(16) and from urban stormwater run

off collected from the same locations

reported in Table I. The results of this comparison, presented in Table

III, demonstrate the distribution simi

larity for non-fecal coliform types found in soil, stormwater runoff, and untreated surface water supplies. The three most common IMViC types in soil (- + -+,-++, and - + + + )

were also the most common in storm water and untreated surface waters. These three coliform IMViC types accounted for 78.8 percent soil strains, 78.4 percent stormwater strains, and 68.4 percent untreated surface water strains.

1866 JOURNAL WPCF November 1968

Bacterial Survival in Stormwater

Stormwater occurs at irregular pe

riods, and the resulting volume may exceed the normal loading capacity of

the usual treatment facility. If storm

water from separate systems is to be

treated before discharge into a re

ceiving stream, large holding reser

voirs will be necessary. During this

holding period, which might last a

few hours or a few days, the status

of the bacterial population becomes a

primary concern. For this reason, bac

terial survival studies w7ere performed on samples collected over a two-year

period in an effort to establish guide lines on stormwater natural self-puri

fication rates. Analysis of data col lected on 52 samples indicated no

significant differences related to pos sible effects from widely varying con

centrations of chemical contaminants

in stormwater runoff. There was, how

ever, a positive correlation for water

temperature and bacterial survival.

The survival data presented in Fig

'SjK^i?i?i?i?i?i?i?i?i?i?i i rq

50 f|\ ^? J

*\ \. if

? ?h ^V . "

'-*.?3 0.8 |?

X. -^ m?*Q

0 5L ?- FECAL COLIFORM >v

0.4L y-x AEROBACTER AEROGENES ^S. -H

? -* STREPTOCOCCUS FAECAL IS ^V^ I

I O.o SALMONELLA TYPHIMURIUM

]^

o,l_L_J_I_I_I_I_I_I_I_I_I_I_I_I 1 2 3 4 5 6 7 8 9 10 M 12 13 M

LENGTH OF TIME, days

FIGURE 1.?Persistence of selected enteric bacteria in stormwater stored

at 20?C

Vol. 40, No. 11, Part 1 STORMWATER POLLUTION 1867

ures 1 and 2 were divided into those

studies made on winter stormwaters

with temperatures ranging from 0? to

12 ?C and for spring, summer, and autumn samples with recorded tem

peratures ranging from 18? to 25?C. For these experiments 10? and 20 ?C incubation temperatures were chosen to represent the average winter and summer stormwater temperatures, re

spectively. The resulting data indi

cate organism persistence remained at

higher levels for winter studies

(10?C) during the 14 days of storage as compared with data from the sum

mer (20?C) studies. S. faecalis per sisted longer at both temperatures and at higher levels than either the Aero bacter aerogenes, fecal coliform, or S.

typhimurium strains used. S. typhi murium persistence at 10 ?C was

slightly higher than that of A. aero

genes but less than that of the fecal

coliform for the first 11 days of stor

age. These data indicate a closer

die-away pattern between fecal eoli

0.7 0.6

-* FECAL COLIFORM

*-X AEROBACTER AEROGENES - STREPTOCOCCUS FAECALIS

o.O SALMONELLA TYPHIMURIUM

J_L J__J_L 6 7 8 9

LENGTH OF TIME, days

10 11 12 13

FIGURE 2.?Persistence of selected enteric bacteria in stormwater stored

at 10? C.

1868 JOURNAL WPCF November 1968

forms and S. typhimurium than be tween fecal streptococci and the

Salmonella strain.

Cats, Dogs, and Rodent Contribution

The fecal coliform to fecal strepto coccus ratios for stormwater were al

ways below 0.7, indicating that pollu tion by warm-blooded animals other than man was probably responsible (17). In the urban community such

animals would likely be animal pets, particularly cats and dogs, plus a sub stantial rodent population. Data col lected on the percentile distribution of

five-tube Most Probable Number

(MPN) values for total coliform, fecal

coliform, and fecal streptococcus pro cedures used to examine rat, chip

munk, rabbit, cat, and dog feces are

summarized in Table IV. These data are based on the bacterial densities found in feces per gram of wet weight for individual values at the 25, 50, and 75 percent quartile points. The

relatively low coliform densities re

ported here for both rabbits and chip munks was observed similarly by Drake et al. (18) in their study of the incidence of coliforms in the feces of common wild animals. With the use of the 50-percent quartile points or median values, a fecal coliform to fecal streptococcus ratio was calcu

lated for each species. These ratio values ranged from a low of 0.0004 for rabbit feces to 0.29 for cat fecal ma

terial. Such ratios are, in general, smaller than those reported for farm animals (19). By contrast, the fecal coliform to fecal streptococcus ratio for man is 4.4 and above 4.0 for various domestic sewages.

The biochemical reactions of 2,635 coliform strains isolated from feces of rats, chipmunks, rabbits, cats, dogs, and a raccoon are reported in Table V. Pour coliform IMViC types ( + +-, ?

H-,-r-+, and + + + -) rep

resenting 98.7 percent of this animal coliform population plus three "oc casional" types were recovered. No

single type in the "occasional'' group constituted more than one percent of the coliform content. There was a

high correlation (95.3 percent) be tween the fecal coliform test and the fecal origin of these 2,635 strains iso lated from 57 different animals.

These data again demonstrate that the fecal coliform test is not specific for

any one coliform type or group of IMViC types, but instead has an ex

cellent positive correlation for coli forms derived from the intestinal tract of warm-blooded animals.

Possible similarities of fecal strepto coccus type distribution in feces of rodents and pets and in stormwater

samples are compared in Table VI. Both in the feces of these animals and in the various storm waters, the entero coccus segment of the fecal strepto coccus group predominates. There

TABLE IV.?Percentile Distribution by Quartile of MPN Values per Gram for Rodent, Cat, and Dog Fecal Material

Animal Feces

Number of Samples

Rat Chipmunk Rabbit Cat

19

Total Coliform 25% Level 50% Level 75% Level

Fecal Coliform 25% Level 50% Level 75% Level

Fecal Streptococcus 25% Level 50% Level 75% Level

FC/FS RATIO

13,000 330,000

14,000,000

13,000 330,000

14,000,000

490,000 7,700,000

11,500,000

80 148,000

130,000,000

80 148,000

130,000,000

94,000 6,000,000

410,000,000

90 4,100

2 20

2,000

2,700 47,000

270,000

630,000 7,900,000

92,000,000

630,000 7,900,000

92,000,000

220,000 27,000,000

2,760,000,000

0.04 0.03 0.0004 0.29

Vol. 40, No. 11, Part 1 STORMWATER POLLUTION 1869

TABLE V.?Occurrence of Coliform Types in Animal Fecal Samples

Animal No. of Strains Examined

Total Fecal Coli form

Strains

+ + -- -

+ -- --

+ + + + + -

+ + -

+ -

+ -

+

Rodentia

Rat

Chipmunk Lagomorpha

Rabbit Carn?vora

Cat Dog Raccoon

317 100

251

600 1,317

50

316 50

201

600 1,295

50

282 0

196

586 1,253

49

0 50

7 41

0

30 0

49

0 8 1

0 50

6 11 0

Total strains 2,635 Percent fecal coliforms

Percent strain occurrence 95.3%

89.8 3.7 3.3 1.9 1.0 0.2 0.1

were no significant differences in the fecal streptococcus distribution among either the three stormwater sources or

for any stormwater source for differ ent seasons of the year.

The atypical fecal streptococcus grouping consists of a S. faecalis strain that can hydrolyze starch and S. faecalis var. liquefaciens that is

capable of peptonization of milk. Both types are of limited sanitary significance since they are the pre dominant feoal streptococcus group isolated from vegetation, insects, or

soil (19). The only discrepancy in the fecal

streptococcus type distribution in

rodents, pets, and stormwater was to be found in the percentage of the S. bovis and S. equinas group. In this

case, S. bovis and S. equinus were at

a significant level in rodents (17.1

percent) and dogs (32.0 percent). Little or none of these two members of the fecal streptococci was found in the 3,079 stormwater strains exam

ined. Laboratory data on the survival of S. bovis and S. equinus indicate these two fecal streptococcus strains are the most sensitive pollution indi

cators, with rapid die-away once they have been removed from the warm

blooded animal intestinal tract. For

example, S. bovis and S. equinus sur

vivais in various stormwater samples were always less than 30 percent in 24 hr with less than 1 percent viable after 1-day storage. Thus, recovery of these fecal streptococcus strains in stormwater reflects very recent soil

contamination with prompt transfer to the water environment through con

current stormwater runoff.

Salmonella in Stormwater

With demonstration of significant fecal pollution in stormwater, there is

always an opportunity for the chance occurrence of Salmonella in this source

of water pollution. With the use of

experimental media previously de scribed for the quantitative recovery of Salmonella, positive results were

obtained for a stormwater sample from the business district separate storm sewer system (20). This storm

water sample contained 4,500 S.

thompson per 100 ml. The bacterial

pollution indicator densities were

3,800,000 total coliforms, 450,000 fecal

coliforms, and 370,000 fecal strepto cocci per 100 ml. These limited data indicate that one Salmonella was de tected for every 100 fecal coliforms in the stormwater sample analyzed.

Although Salmonella could not be found in other stormwater samples examined by current experimental pro

1870 JOURNAL WPCF November 1968

TABLE VI.?Fecal Streptococcus Distribution in Rodents, Cats, and

Dogs and Three Types of Stormwater

Source No. of Strains Examined

Percentage Distribution of Fecal Streptococci

Season Enterococcus *S. bovis S. equinus

Animals

Rodents

Cats

Dogs

539 268 585

47.3

89.9

44.0

Total 1,392 Average 54.2

17.1

1.5

32.0

20.3

Stormwater

Residential streets 745 180 40

193

Spring Summer

Autumn

Winter

81.6

66.6

85.0

85.0

Total 1,158

Average 80.0

Business district 417 439 296 324

Spring Summer

Autumn

Winter

82.3

71.1

75.7

86.1

Total 1,476

Average 78.5

Rural 227 90 96 32

Spring Summer

Autumn

Winter

90.8

86.7

77.1

96.9

Total 445 Average 87.4

0.4

0.0

0.0

1.6

0.5

1.7

0.0

1.7

3.4

1.6

0.9

0.0

0.0

0.0

0.5

cedures, its presence in this one in

stance is significant. Agricultural animals are frequent

sources of Salmonella. Miner et al.

(21) reported isolation of Salmonella in the litter and runoff from two

cattle feedlots holding apparently nor

mal animals. Entry of such material into stormwater runoff may be a sig

nificant source of pathogens in rural areas.

Summary and Conclusions

Stormwater examined from city streets, a suburban business district storm drain, and a wooded hillside

adjacent to a city park all had a bac

teriological composition similar to

stormwater runoff collected from cul

tivated farm fields. Seasonal differ ences in the bacterial densities for total coliforms, fecal coliforms, and fecal streptococci were noted in a

study of median values. The fecal coliform segment of the total coliform

population for all stormwater samples averaged 8.6 percent. For stormwater

samples collected in autumn from the suburban business district, however, 21.1 percent fecal coliforms were ob served.

Data collected on 49 rainwater sam

ples indicated pollution indicator counts generally were less than 1/100

ml, but individual storms occasionally

may contain a few coliforms. The

Vol. 40, No. 11, Part 1 STORMWATER POLLUTION 1871

origin of these positive samples was

associated with material acquired in

dust storms or from insect and vegeta tion fragments. The major contamina tion of rainwater occurs from contact

with the polluted land environment. Data showed the similarity of the non fecal coliform distribution patterns for strains examined in soil, stormwater

runoff, and untreated surface waters.

Differences in the fecal coliform con tent for a particular soil, stormwater, or untreated surface water were re

lated to varying levels of fecal con

tamination present.

In the urban community fecal con tamination in separate stormwater sys tems is derived initially from the fecal

material deposited on soil by cats, dogs, and rodents. Both in the storm water and in fecal material from the

animals, the enterococcus segment of the fecal streptococcus group showed similar percentage patterns and the ratios of fecal coliforms to fecal

streptococci were generally less than 0.7. By contrast, the fecal coliform to fecal streptococcus ratio for man is 4.4 and above 4.0 for various domestic

sewages.

Studies of bacterial survival in stormwater indicated organisms per sisted at higher levels for winter stud ies (10?C) than they did in the sum

mer (20? C) studies. Comparison survival studies for S. typhimurium,

A. aerogenes, S. faecalis, and a fecal coliform strain demonstrated that the

die-away pattern of S. typhimurium resembled that of the fecal coliform strain more closely than it did for that of fecal streptococcus strain, S.

faecalis. S. thompson was isolated in one

storm sample at a level of 4,500/100 ml. The bacterial pollution indicator densities for this sample from the business district separate storm sewer

system were 3,800,000 total coliforms, 450,000 fecal coliforms, and 370,000 fecal streptococci per 100 ml.

Stormwater can be a major source

of intermittent pollution to bathing beaches and to water supply reservoirs

opened to limited public recreational uses. Eegulations to prohibit cats and

dogs on public beach areas and an

adequate garbage control plan to dis

courage increased rodent habitation will be of benefit. Diverting storm drains and land drainage away from beaches and reservoirs are also im

portant engineering considerations.

Finally, in areas where such storm

drainage cannot be diverted economi

cally to prevent deterioration of water

quality, treatment methods must be

developed to handle the large volumes of irregular discharges that character ize stormwater.

Acknowledgments

The authors wish to express their

appreciation to Messrs. G. G. Robeck, S. R. Weibel, R. J. Anderson, and R. B. Weidner, Engineering Research

Section, for their engineering assist ance in locating separate stormwater

systems in suburban, agricultural, and industrial areas. Special recognition also is given to Mr. Martin P. Milet of Williamsdale Kennels for a source of fecal samples from healthy cats and

dogs fed a normal diet free from antibiotic additives.

References

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1872 JOURNAL WPCF November 1968

6. Weibel, S. R., Anderson, R. J., and

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