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Microbiological studies on the quality of urban stormwater runoff in Southern Ontario, Canada
Water Research Vol. 13, pp. 977 to 985 Pergamon Press Ltd 1979. Printed in Great Britain.
MICROBIOLOGICAL STUDIES ON THE QUALITY OF URBAN STORMWATER RUNOFF IN SOUTHERN ONTARIO, CANADA A. A. QURESHI Microbiology Section, Laboratory Services Branch, Ministry of the Environment, Rexdale, Ontario M9W 5Ll, Canada and B. J. DUTKA Microbiology Laboratories Section, National Water Research Institute, Canada Centre for Inland Waters, Burlington, Ontario L7R 4A6, Canada (Received 2 April 1979) Abstract--The microbiological quality of urban stormwater runoffs was investigated at three different locations in Southern Ontario, Canada. Microbial densities in these waters were similar to those found in dilute raw wastewaters and, therefore, represent a potential health hazard. The recovery of pathogenic bacteria (Pseudomonas aeruginosa and salmonellae) further substantiated the existence of health hazards. There appeared to be little relationship between the duration, intensity and amount of rainfall and the occurrence of peak microbial populations. As a result, no typical pattern of time-related distribution of indicator and pathogenic bacteria could be established in this investigation. This suggests that "initial flushing has minimal effect on the microbiological quality of an individual storm event. Furthermore, the results indicate the seriousness of urban stormwater runoffs as a major factor in nonpoint source pollution of receiving waters and that it would be illogical to disinfect specific portions of these runoffs for removing health hazards as there was no predictable pattern of pathogen occurrence.
INTRODUCTION
During recent years many studies have been conducted in the United States to determine the quantitatire and qualitative characteristics of stormwater discharges and their impact on receiving waters (Bradford, 1977; Burro & Vaughan, 1966; G-eldreich et al., 1968; Kothandaraman, 1972; Olivieri et al., 1977; Weibel et al., 1966). The emphasis of these studies has been on the similarity between stormwater runoffs and sewage and their inherent potential health hazards. Using calculations based on a hypothetical city, Sartor et al. (1974) showed that the runoff from the first hour of a moderate to heavy storm (1.27 cm h - 1) would contribute a substantially greater pollution load than would the same city's sanitary waste during the storm period. Since "rainwater" contaius insignificant levels of bacteria, its major contamination occurs on contact with the land environment, creating a potential pollution problem in the resulting runoff (Geldreich et al., 1968). A variety of surface materials, from diverse sources, contaminate rainwater and find their way into stormwater discharges (Geldreich et al., 1968; Sartor et al., 1974; van Donsel et al., 1967~ In addition to fecal pollution indicator bacteria, the presence of pathogenic bacteria in stormwater has frequently been reported. Evans et al. (1968) demonstrated the existence of a potential health hazard by isolating Salmonella thompson (at a level of w.lt, 13/10---D
977
4500/100 ml) from a stormwater sample in an urban business district separate storm sewer. This same stormwater sample contained 3,800,000 total coliforms, 450000 fecal coliforms and 370,000 fecal streptococci per 100mL Studies on the sources of bacteria found in stormwater runoff from residential and light commercial areas indicated that the bacteria were predominantly of non-human origin (Benzie & Courchaine, 1966; Geldreich et ai., 1968; Weibel et al., 1964). However, in several instances (Dutka, 1977; Evans et al., 1968; Sartor et al., 1974) pathogenic bacteria were also isolated in runoff waters, demonstrating the existence of a potential health hazard. Although little conclusive data are available on the time-related distribution of indicator and pathogenic bacteria in stormwater runoffs, it has generally been assumed that the majority of micro-organisms, both indicator and pathogenic, are found in the first portion or initial flushing of stormwater. Based on the above, it has been suggested that, by containing and treating a speofic portion of the initial runoff, the majority of bacterial health hazards would be eliminated from receiving waters. These assumptions and suggestions crystallized into a joint Canadian federal/ provincial Government project to investigate their vafidity and usefulness. Since little reported data are available on the microbiological characteristics of urban stormwater runoffs in Canada, it was necessary to obtain these data from
A.A. QURESHIand B. J. DUTKA
978
typically u r b a n drainage areas to support or refute the potential a n d practicality of the c o n t a i n m e n t and disinfection hypothesis. The results reported here are based on studies which were conducted over a twoyear period at two residential and one commercial area. MATERIALS AND METHODS
Description of the .study sites (a) A storm sewer outfall into a small Burlington creek near Malvern Road in Burlington, Ontario (population 104,000) was one of the study sites. The Malvem Road drainage area is approximately 2.3.3 ha, and is situated in central Burlington. The entire area is zoned for single family residences and there are no vacant lots within the area. Most of the houses were built in the early 1960's with virtually all development completed b y 1964. The majority of houses in this area have their eaves troughs connected to storm sewers which are 100~ separated, (b) The Aldershot catchment area is a 6.88 ha commercial plaza in the western section of Burlington. The imperviousness of the catchment area is I 0 0 ~ with roofs, sidewalks and a paved parking lot making up 100~ of the area. The plaza contains one large department store, a Canadian Tire workshop and gasoline pumping station, one large chain grocery store and 15-20 small boutiquetype stores. The area has 100% separate storm sewers. (c) The third site (Barrington Avenue) was located in the Borough of East York (population 103;000), part of which is in the City of Toronto. With the exception of five or six corner stores, the area is composed entirely of single family residential housing ranging from 50 to 70 years in age. The site has 100% separate storm sewers with a total drainage area of 22.7 ha. The area containing buildings not connected to the storm sewer system is approximately 5.3 ha.
Sample collection Various types of sample collection procedures were used in this study. At the Malvern Road site, bacteriological samples were hand-collected at the weir outfall in sterile glass bottles. At the first indication of a rainfall, a technician would arrive at the sample collection site and wait for the first drops of rain. When the rain started, the first sample would be collected as soon as there was a noticeable change in the flow rate and this sample was labelled "'0" minute. Samples were then collected 10, 20, 30, 45, 60. 75, 90, 105, 180 and 240min after the "0" minute sample. Since Aldershot Plaza sampling site was at the bottom ofa manbgle, samples were collected by means of a North Hants automatic sampler using sterile collection bottles, This sampler was triggered by a 5 cm rise in water level and would automatically collect samples at 20 rain intervals as long as the water level rise was equal to, or greater than, 5 cm. At the East York site, water samples were collected manually, in sterile glass bottles, every 5 rain for a period of approximately one hour after the onset of a rainfall event. For these samples, a technician was dispatched to the sample site soon after the rainfall began. Unless otherwise specified, the first sample was collected within 15 rain of the initiation of a storm event, On two occasions when no rainfall occurred, sediment samples were collected by hand in sterilized Nalgene widemouth jars from the East York site for Salmonella analysis. For qualitative detection of salmonellae, mOdified Moore swabs (Dutka & Bell, 1973) were used. These were exposed to stormwater for varying periods during each rainfall event,
At the Aldershot site, eight infiltration samples were collected during dry periods from June to September, 1975. In" addition, during May to November, 1976, ten infiltration samples were collected from the storm sewer at the Malvern site.
Microbiological analyses All stormwater and infiltration samples were tested for total coliform, fecal coliform, fecal streptococcus and Pseudomonas aeruvinosa densities using the membrane filtration technique. Populations of heterotrophic bacteria and fungi were enumerated by using the spread plate technique. The details of the media and procedures used for the~e analyses are outlined by Dutka (1975) and Qureshi (1977). For qualitative detection of salmonellae, modified Moore swabs were processed following the .procedure of Dutka & Bell (1973). Storm water samples in variable allquots (ranging from 10 to 400ml) were filtered through 47 mm sterilized fiberglass prefilters (Sartorius SM 13400). The filters were aseptically placed in selective enrichment broths for the isolation and identifications of salmonellae following the procedures described by Dutka & Bell (1973) and Qureshi (1977). For determining the relative distribution of coliform and fecal coliform biotypes, isolates were collected from selected infiltration and stormwater samples and identified using procedure described by Dutka & Tobin (1976). RESULTS Twelve storm events were monitored at the Malvern site during April 21 to October 24, 1976. The concentrations of indicator organisms in the runoff water varied considerably during these events which were of different intensities and duration, Examples of two of the events monitored are shown in Figs. 1 and 2. Figure 1 displays the microbiological data obtained from a very heavy rainfall (101 ram) which lasted for 240 rain. During this event, the m a x i m u m populations occurred 75 rain (fecal coliforms, fecal streptococci), 90 min (fungi), 105 min (eoliforms) a n d 150 min (heterotrophs) after the storm began. Salmonellae were isolated from a 100 ml water sample collected at the 90 rain mark. The event depicted in Fig. 2 was also of 240rain duration, but only 9 m m rain fell during this storm with m a x i m u m populations occurring between 75rain
(P. aeruginosa) and 150 rain (heterotrophs) period. N o salmonellae were isolated from water samples collected during this event. This event was of intermittent nature a n d provides a typical example of a slow a n d gentle rain which results in a gradual increase in the microbial population as the main flow hits the weir. At the Malvern site, salmonellae were only isolated during four of the 12 events from the 10, 90 and 240 rain samples through filtration of 100 ml runoff water, and from the modified M o o r e swabs exposed to stormwater for 30 rain. Salmonella thompson and S. typhimurium var. copenhagen were the two species isolated a n d identified. The results of ten infiltration samples collected at this site between M a y 10 a n d N o v e m b e r 30, 1976, are presented in Table 1. The data indicate that low levels of indicator bacteria and pathogens (P: aeru-
Microbiological
979
studies
o
Coliforms/IOOml Fungi/IOOmL [] Heterotrophs/m( - ' ~ Salmonellae isolation
• • •
Fecal coliforms/IOOmL Fecal streptococci/IOOmL P. aeruginosa/IOOmL
io 5 =--
E .~
104
103
o¢) 103
10
0 15 30456075 90105120 150 Time of collection,
180 min
240
0 IS 3045 60 7~ 901051~0 150 180 Time of collection, min
240
Fig. 1. Distribution and concentrations of micro-organisms in stormwater runoffs, June 24 1976,
Malvern Road (Burlington) site.
,oinosa) are being continuously discharged from the storm sewer into the receiving creek waters Table 2 summarizes the coliform and fecal coliform genera/ species distribution in stormwater and infiltration samples collected from the Malvern site. It is interesting to note that the distribution was similar throughout various periods of the storm and that, among coliforms in runoff waters, approximately 45~o of the isolates were E. coil and the rest belonged to Klebsiella (23-31~o), Enterobacter (16-22~) and Citrobacter (6-10%). Furthermore, a greater percentage of E. coil were found in infiltration samples as compared
I
o ~ r~
tO6~_
~,~
with runoff waters In both the infiltration and runoff samples, all fecal coliforms belonged to E. coil Microbiological data from one of the five rainfall events, monitored during June 19 to September 9, 1975, at the Aldershot Plaza, are shown in Fig. 3. Sample collection problems plagued this sampling site. Because of the imperviousness of the drainage area, the runoff was very quickly channeled into the storm sewers where this fast moving and developing water mass, upon reaching the sampling site, frequently demolished and swept away the sampling equipment. Thus at this site only slow and intermit-
Coliforms/IOOmL Fungi/IOOml. Heterotrophs/mL
• • •
IO5
i04
IO4
I0 3
io
io 2
I-.)~d=
I
u I
t I
a
0 15 3 0 4 5 6 0 7 " 5 9 0 1 0 5 1 2 0
l
I
I
I
150
180
240
Time of collection, Fig. 2. Distribution
min
ko~/-k J- J
I
I
Fecal collforms/lO0 mL Fecal streptococci/100 mL P. oeruginoso/lOOmL
I
I
0 15 3 0 4 5 6 0 7 ' 5 90105120
I
1
I
150
180
240
Time of collection,
and concentrations of micro-organisms in stormwater MaJvern Road (Burlington) site.
rain
runoffs, October 19 1976,
980
A. A, QURESHI and B. J. DUTKA Table 1. Densities of micro-organisms in infiltration samples from Malvern Road (Burlington) site, 1976 Microbial parameters per 100 ml Fecal Fecal Pseudomonas coliforms streptococci aeruoinosa
Date
Total coliforms
May 10 May 30 June 14 July 20 Aug. 17 Aug. 30 Sept. 29 Oct. 12 Nov. 2 NOV. 30
3.0 1 9.0 3.0 5.8 x 102 17.0 4.4 x 102 1.2 × l0 s 5.3 x 103 1.3 x 102 4.0 × 10 3 1.4 x 10a 5.6 x 103 1.8 x I03 6.0 x l02 2.0 x 102 4.5 x 102 . 83.0 1.2 x 102 ll.0
13.0 16.0 3.4 × 10z 1,4 x 102 9.0 x 102 3.4 x 102 1.2 × l02 40.0 1.1 x 102 21.0
tent rainfall events were monitored; microbiological data from one such event (7.9 mm rainfall) are presented in Fig. 3. The rainfall began at 12:30p.m. and the first sample was collected at 12:45 p.m. Maximum fecal streptococcus and fungal densities occurred within 15 min of rainfall initiation, while the highest concentrations of total coliform and P. aeruginosa occurred 40 min after the commencement of the storm, At the Aldershot site, salmonellae (S. senftenberO and S. newport) were isolated from the modified Moore swabs left in the manhole for the duration of two separate events. Infiltration data from this site are presented in Table 3. The densities of total coliform (2.9 x 10a-2.2 x 10~/100ml) and P. aeruginosa (14-3.0 x 10a/100ml) in these waters were equivalent to those usually found in dilute sewage. Coliform isolates from one of these infiltration samples showed the following distribution pattern: Aeromonas sp. 50%, Klebsiella sp. 45~./~ and E. coli 5% (Table 2). Stormwater runoffs from four events were monitored at the Barrington Avenue (East York) site, the results from two of these events are illustrated in Figs. 4 and 5. A small m o u n t (2.3 mm) of rain fell during the October 1 1975 event which lasted for only 30 min. Sample collection started within 15 min of the onset of the rainfall and continued for 40 min after the end of the storm. As shown in Fig. 4, all popula-
t 3.0 3.9 × 102 10.0 7.0 × 102 7.4 x 104 10.0 9.0 I 33.0
Total fungi
Heterotrophs per ml
13.0 9.0 80.0 60.0 1.0 x 102 43.0 1.2 × 102 4.0 x 102 80.0 13.0
4.0 1.2 1.7 3.3 6.6 8.1 9.0 1.6 1.1 5.9
x × x x x x x x x x
10a l0 s l0 s 104 10" 103 103 l0 ~ 10'* 103
tions enumerated showed a sharp increase within the first I0 rain of collection with coliform populations fluctuating to a final peak at the 35 min mark, 50 rain after the rainfall began. Salmonellae were isolated from 10ml stormwater samples collected at the 15 min (S. saint-paul~ 20 and 25 rain periods (S, typhimurium var. copenhagen). S. typhimurium var. copenhagen was also isolated from a 50 ml aliquot of the runoff sample collected at the 30 rain mark, No salmonellae were isolated from the modified M o o r e swab during this storm event. The event shown in Fig. 5 was unusual in the 8¢nt~ that the ground was frozen and thus rather impcrvious so that the runoff was compoaed mainly of rainwater and melting snow. A total of 10.9ram rainfall occurred during this storm which lasted for 735 rain. The rainfall began at 3.15a.m. with the first sample being collected at 9.45 a.m., arid the most intensive period of rainfall (2.5 mm) occurred during the 55 rain sampling period. The maximum concentrations of total coliform, fecal coliform, fecal streptocoeus and fungi were observed in samples collected at 45-55 minute marks. P. aeruainosa populations were unusually high during the collection period espedally as P. aeruginosa are not noted for their ability to survive at freezing temperatures. N o salmonellae were isolated from either the modified Moore swab or stormwater samples during this event.
Table 2. Coliform and fecal coliform distribution in stormwater and infiltration samples from Malvem Road and Aldershot Plaza Stormwater runoffs (Malvern Road) 0-30 min 60-90 min 120--240 min
Genus/species
E, coli Klebsiella Emerobacter Cttrobacter Aeromonas
Infiltration Malvcm Road Aldershot Plaza
Fecal Fecal Fecal Fecal Coliforms coliforms Coliforms coliforms Coliforms coliforms Coliforms coliforms (%) (%) (%) (%) (~o) (%) (%) (%) 45 23 22
l0
98 2
44 31 16
9
100
46 29. 19
6
100
60 29 10
100
Coliforms (%) 5 45
1 50
Microbiological studies
981
1.8 x I 0T/e\ / i°7-
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I
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IOE Z---
-
\\
/~
_ _
/
/ /
Total coliforms " Fecal stroptococci P. oeruginosa Fecal coliforms Fungi .
\
I
b.,. ~
",. ~
~,,,,e,~
"e~
"'--..
-~ ,o;
io21 12t45
I 12:55
I 13:15
I3:05
I 13:25
I 13:35,
13:45
I 13:55
I 14:05
Time of collection
Fig. 3. Distribution and concentrations of micro.organisms in stormwater runoffs, August 21 1975, Aldershot Plaza (Burlington) site.
Two s e d i m e n t samples collected from the East York weir under dry weather conditions were examined for Salmonella incidence. Whereas, the September 29 1975 sample yielded no salmonellae, S. typhtmurium v~r. copenhagen was found in a 25 g (wet weight) aliquot of the November 4 1975 sample. It is interesting to note that, at this site, the same Salmonella serotype had previously been isolated from
the October 1 1975 runoff and later from the January 26 1976 storm events. DISCUSSION In the present study, the most reliable data on the distribution of indicator organisms and pathogens in stormwater runoffs was obtained only at the Malvern
Table 3. Densities of micro-organisms ifi infiltration samples from Aidershot Plaza (Burlington) site, 1976 Total coliforms
Date June 19 June 23 July 2 July 7 July 16 July 29 Aug. 18 Sept. 9
>1.5 > 1.0 6.7 5.6 2'2 9.0 2.9 2.6
* -- Not analyzed.
x × × x x x x x
l0 s 105 10a 106 l0 T 103 103 106
Microbial parameters per 100 ml Fecal Fecal Pseudomonas coliforms streptococci aeruginosa 7.5 4.1 1.0 2.8 3.1 3.1 1.4 2.1
x x x x x x x x
103 103 102 102 102 102 102 103
1.8 1.2 7.1 5.1 6.7 2.1 5.5 1.6
× × × x x x x ×
103 102 10z 103 102 102 103 102
2.6 x 2.6 x 3.Ix 1.7 x 2.7 x 1.4 x 3.0 x 1.4 x
103 103 102 103 103 10t 103 102
Total fungi NA* NA NA NA NA 2.0 x 106 2.0 x 104 NA
982
A.A. QURESH[ and B. J. DUTKA
o
Coli forms Fungi •--...,-- Sal monelloe isolation
• •
10 7
107
105
105
Fecal coliforms Fecal streptococci
0 0
c:
0
I0 ,5 20 25 30 35 40 45 50 55 Time of collection,
0
.5 ,0 15 20 25 30 35 40 45 5 0 5 5
rain
Time of collection,
rain
Fig. 4. Distribution and levels of micro-organisms in stormwater runoffs, October 1 1975, Barrington Avenue (East York, Toronto) site.
o ,~
0
0
Coliforms Fungi
• •
Fecal coliforms Fecal streptococci aeruginosa
• F)
106~
106
)05
105
104
t04
,o1,
E
~
102 0
I I I I t 1 I I i 1 I 5 10 15 20 25 30 35 40 45 ~)0 55 Time of c o l l e c t i o n ,
Fig.
5. D i s t r i b u t i o n
and
102 0
rain
levels o f ~ o - o r M a f i s m s
I 5
,,.-4
I Y l I I I, I ~ t IO 15 20 2~ 30 35 40 45 ~ ) 55 T i m e of colle©tton,
in
stormwa~r
runoffs,
Barrinston Avenue (East York, Toronto) site.
rain
De~mlx~
30 1975,
Microbiological studies
983
Road site. This reliability was due to the sampling populations during the short 55 min sampling period. procedure followed as the sampler, upon hearing No relationships or trends were evident as the peak storm forecasts, actually waited at the site until it microbial populations occurred either in the initial rained and then collected the samples, At the Malvern stages, middle or tail-end of the sampling period of site, maximum microbial populations generally a variety of storms monitored. Furthermore, though occurred 60-135 rain after the normal infiltration flow some variations were observed, generally the initial in the weir was observed to change. This change counts(in 0-10rain samples)of indicator bacteria and usually occurred within 5-15 rain of a rainfall com- fungi were either at about the same level or slightly mencing, depending on the initial intensity of the rain. higher than the counts from 15-55 rain samples. LikeSalmonellae, which were infrequently detected at this wise, salmonellae were isolated at different times site, exhibited no consistent distribution pattern as throughout the sampling period. These data indicate the isolations were made throughout the 240 rain that any effect of initial flushing on the microbial quasampling period. These observations lend support to lity of the discharges was minimal during an indivithe assumption that all portions of stormwater dual storm. These findings also indicate that short runoffs may contain potential health hazards, interval/period sampling scheme is probably not suitThe Malvern Road coliform and fecal coliform iso- able for determining the incidence and distribution late data indicate that similar proportions of Entero- of peak populations of different micro-organisms in bacteriaceae are being discharged throughout the stormwater runoffs. 240min sampling periods. These data are supportive The December 30 1975 event is unique in that, we of the belief that, although there may be an initial believe, it provided the first microbiological runoff flush of animal and bird feces when a runoff first de- data representing the effects of a mid-winter, rainfall velops, the Enterobacteriaceae stormwater distribu- on frozen snow-covered ground. Although the first tion pattern is indicative of the Enterobacteriaceae sample was collected 390 min after the rainfall begun, distribution on surfaces and in soils, substantially high (103-105/100 ml) levels of indicator Aldershot Plaza data are unique in that they rep- bacteria and fungi were present in all runoff samples resent a totally impervious drainage area. Stormwater collected during this event. This further substantiates samples were difficult to collect due to the rapid earlier observations that initial flushing has little effect runoff and the necessity of the water to rise to a on the microbiological quality of stormwater runoffs. specific level to trigger the automatic sampling mech- In addition, there are several questions which arise anism. At this site, maximum microbial populations from these data. Are snowfalls in urban areas an unalways occurred within the first hour of a rainfall suspected reservoir of pathogenic organisms and indiprobably due to the impervious nature of the cator bacteria? Where do substantially high concertdrainage area which allowed the collection of samples trations (10s/100 ml) of fungi come from? What are only from small intermittent rainfalls, the sources of the observed high levels of coliforms, Aldershot Plaza infiltration data (Table 3) showed fecal coliforms and fecal streptococci in these runoff very high background densities of coliform samples? During this event, the ground was frozen (2.2 x 107), fecal coliform (7.5 x l03) and fungi and relatively impervious to the rain, therefore, the (2.0 x 106). These elevated populations, possibly due rainfaU-melting snow mixtures were probably responto sewage line leaks or regrowth within the lines, are sible for the strikingly high populations of these being consistently inoculated into receiving waters, organisms. This suggests that snowfall/slush in urban Thus it is probable that such uncontrolled inputs help areas may harbor and preserve micro-organisms (esto maintain elevated population levels and potential pecially of animal fecal origin) which eventually reach health hazards in inshore receiving waters all year storm sewers and receiving waters. High concenround, trations of indicator bacteria encountered in sediDifferences were observed in the distribution pat- ments and the findings of a Salmonella serotype in tern of coliforms in infiltration samples from the two one sediment sample suggests that the sediments are monitored sites (Table 2). While Aeromonas was not yet another source and contributor of these organisms isolated from the Malvern Road, at the Aldershot site to the recipient waters. approximately 50% of the coliform isolates were AerAt all sites and during each event monitored, the omonas sp. Furthermore, at the Aldershot Plaza, only densities of traditional indicators (total coliform, fecal 5~o of the coliform isolates were E. coli as compared coliform and fecal streptococcus) approached concento 50% at the Malvern site. These differences may trations found in dilute raw sewage, thus ro-emphasizbe attributed to different land uses and drainage ing the health hazards due to pathogenic bacteria and characteristics at these two site~ .viruses (Olivieri et al., 1977) which are contained In the East York study, no "zero" minute sample within stormwater runoff waters. One of the indicator was collected during any of the storms monitored organisms used in this study, P. aeruginosa, is also since considerable time elapsed between the start of . a pathogen. This organism has been implicated in eye. rainfall and technician's arrival at the site. However, ear, skin and upper respiratory tract infections and is stormwater samples were collected at regular (5 rain) regarded as a major etiological agent of otitis externa intervals to ascertain distribution trends of microbial among swimmers (Young & Armstrong, 1972: Hoad-
A, A. QURESHIand B. J. DUTKA
984
ley, 1968). Thus the increased P. aeruginosa populations discharged into our receiving waters, many of which are used for recreational purposes, constitute an elevated risk not previously suspected and investigated, The mycological procedures used during this study did not differentiate between saprophytic and invasive pathogenic fungi (including yeasts). It is known that both types will grow on the media used. Therefore, the striking increase seen in fungal populations during most rainfalls should be cause for concern especially as many of the invasive fungi do so through skin contact. Thus these storm runoff waters are contributing another heretofore unsuspected group of potential pathogens into receiving and recreational waters. The results of this study corroborates findings reported by previous investigators (Evans et al., 1968; Geldreich et al., 1968; Olivieri et al., 1977) and demonstrated the existence of potential health hazards in stormwater discharges. Moreover, the results also show the seriousness of urban stormwater runoffs as a major factor in "nonpoint" source pollution of receiving surface waters,
Salmonella serotypes found in this study have also
been isolated from humans in Canada during the past several years. 5. This study shows that discharges from separate storm sewers could be a major source of microbial pollution to receiving waters and reservoirs, and that it is not possible to realistically decrease public health risks by containing and disinfecting some portions of these discharges. Acknowledgements--This research was financially supported, in part, by the Government of Canada and the Government of the Province of Ontario under CanadaOntario Agreement Projects 74-8-25, 75-3-24 and 76-8-41.
REFERENCES BenzieW. J. & Courchainc R. J. (1966) Discharges from separate storm sewers and combined sewers, d. Wat. Pollut. Control Fed. 38, 410-421. Bradford W. L. (1977) Urban stormwater pollutant loadings: a statistical summary through 1972. J. War. Pollut. Control Fed. 49, 613-622. Burro R. J. & Vaughan R. D. (1966) Bacteriological comparison between combined and separate sewer discharges in Southeastern Michigan. J. War. Pollut. Control Fed. 38, 400--409.
CONCLUSIONS
Dukta B. J. (ed.)(1975) Methods for microbiological analysis of waters, wastewaters and sedimenta IWD, SOD. 1. Discharges from all three storm sewer systems Canada Centre for Inland Waters, Burlington, Ontario. contained significant quantities of pollution indicator Dutka B. J. (1977} Microbiological study of storm runoff bacteria. Among the pathogenic micro-organism, P. watersfrom a 100% residential area in Canada. Can. Res. 10, 50-53. aeruainosa were the most numerous and frequently Dutka B. J. & Bell J. B. (1973) Isolation for salmonellae isolated. Salmonellae were detected frequently in from moderat~lypolluted waters. J. Wat. Pollut. Control stormwater runoffs and, in several instances, were Fed. 45, 316-324. readily isolated from as little as 10 ml aliquots of Dutka B. J. & Tobin S. E. (1976) Study on the efficiency of four procedures for enumerating coliforms in water. stormwater. There was no predictable pattern of SalCan. J. Microbiol. 22, 630-635. monella isolation; they were found throughout the Evans F. L. GeldreichE. E., Weibel S. R. & Robeck G. G. various sampling periods. (1968) Treatment of urban stormwater runoff. J. War 2. Infiltration waters appear to be a source of low Pollut. Control Fed. 40, 162-170. level but continuous microbial pollution. Similarly, Geldreich E. E., Best L. C., Keaner B. A. & van Donsel D. J. (1968) The bacteriological aspects of stormwater sedimentsandsnowmayennstitutereservoirsofmicropollution. J. Wat. Pollut. Control Fed. 40, 1861-1872. organisms which ultimately find their way into storm- Hoadley A. W. (1968) On the significanceof Pseudomanas water runoffs and receiving waters, aeruoinosa in surface waters. J. New Enol. Water Wks 3. Little relationship was observed between the inAss. 82, 99-111. Kothandaraman V. (1972) Water quality characteristics of tensity and amount of rainfall and the in,,idence of storm sewer discharges and combined sewer overflows. indicator bacteria and pathogenic micro-organisms. Circular 109. Illinois State Water Survey, Urbana. pp. As a result, no predictable maximum microbial den1-18. sity pattern could be established during this study. Olivieri V. P., Kruse C. W., Kawata K. & Smith J. E. The unpredictable and intermittent appearance of (1977)Microorgamsms in urban stormwater. EPA, Cincinnati, Ohio, EPA-600/2-77-087. micro-organisms in stormwaters suggest that any Qureshi A. A. (1977) Microbiolo$ical characteristics of effect of initial flushing on microbiological quality of stormwater runoffs at East York (Toronto) and Guelph the discharges was minimal during an individual storm sewers. Ministry of the Environment, Ontario. storm. Canada, p. 57. 4. At all three sites, the levels of microbial poputa- Sartor J. D., Boyd G. B. & Agardy F. J. (1974) Water pollution aspects of street surface contaminants. J. Wat. tions in stormwater runoff were strikingly high Pollut. Control Fed. 46, 458-467. throughout the entire sampling period and many van Donsel D. J., Geldreich E. E. & Clarke N. A. (1967) times approached densities found in dilute raw wasteSeasonal variations in survival of indicator bacteria in waters and, therefore, constitute a health hazard. The soil and their contribution to stormwater pollution. Appl. Microbtol. 1~, 1362-1370. implied public health risk is substantiated by the re- Weibel S, R., Anderson J. R. & Woodward R. L, (1964) covery of pathogenic and potentially patho$mtic bacUrban land runoff as a factor in stream pollution. J. teria in discharges from the sites studied. Moreover, War. Pollut. Control Fed. 36, 914-924.
Microbiological studies Weibel S. R., Weidner R. B., Christianson A. G. & Anderson R. J. (1966) Characterization, treatment and disposal of urban stormwater. In Advances in Water Pollution Research. Proc. 3rd. International Conf War. Pollut. Res.
985
Vol. 1, pp. 329-359. Port City Press, Baltimore, Maryland, U.S.A. Young L. S. & Armstrong D. (1972) Pseudomonas aeruginosa infections. Crit. Rev. Clin. Lab. Sci. 3, 291-347.
MICROBIOLOGICAL STUDIES ON THE QUALITY OF URBAN STORMWATER RUNOFF IN SOUTHERN ONTARIO, CANADA A. A. QURESHI Microbiology Section, Laboratory Services Branch, Ministry of the Environment, Rexdale, Ontario M9W 5Ll, Canada and B. J. DUTKA Microbiology Laboratories Section, National Water Research Institute, Canada Centre for Inland Waters, Burlington, Ontario L7R 4A6, Canada (Received 2 April 1979) Abstract--The microbiological quality of urban stormwater runoffs was investigated at three different locations in Southern Ontario, Canada. Microbial densities in these waters were similar to those found in dilute raw wastewaters and, therefore, represent a potential health hazard. The recovery of pathogenic bacteria (Pseudomonas aeruginosa and salmonellae) further substantiated the existence of health hazards. There appeared to be little relationship between the duration, intensity and amount of rainfall and the occurrence of peak microbial populations. As a result, no typical pattern of time-related distribution of indicator and pathogenic bacteria could be established in this investigation. This suggests that "initial flushing has minimal effect on the microbiological quality of an individual storm event. Furthermore, the results indicate the seriousness of urban stormwater runoffs as a major factor in nonpoint source pollution of receiving waters and that it would be illogical to disinfect specific portions of these runoffs for removing health hazards as there was no predictable pattern of pathogen occurrence.
INTRODUCTION
During recent years many studies have been conducted in the United States to determine the quantitatire and qualitative characteristics of stormwater discharges and their impact on receiving waters (Bradford, 1977; Burro & Vaughan, 1966; G-eldreich et al., 1968; Kothandaraman, 1972; Olivieri et al., 1977; Weibel et al., 1966). The emphasis of these studies has been on the similarity between stormwater runoffs and sewage and their inherent potential health hazards. Using calculations based on a hypothetical city, Sartor et al. (1974) showed that the runoff from the first hour of a moderate to heavy storm (1.27 cm h - 1) would contribute a substantially greater pollution load than would the same city's sanitary waste during the storm period. Since "rainwater" contaius insignificant levels of bacteria, its major contamination occurs on contact with the land environment, creating a potential pollution problem in the resulting runoff (Geldreich et al., 1968). A variety of surface materials, from diverse sources, contaminate rainwater and find their way into stormwater discharges (Geldreich et al., 1968; Sartor et al., 1974; van Donsel et al., 1967~ In addition to fecal pollution indicator bacteria, the presence of pathogenic bacteria in stormwater has frequently been reported. Evans et al. (1968) demonstrated the existence of a potential health hazard by isolating Salmonella thompson (at a level of w.lt, 13/10---D
977
4500/100 ml) from a stormwater sample in an urban business district separate storm sewer. This same stormwater sample contained 3,800,000 total coliforms, 450000 fecal coliforms and 370,000 fecal streptococci per 100mL Studies on the sources of bacteria found in stormwater runoff from residential and light commercial areas indicated that the bacteria were predominantly of non-human origin (Benzie & Courchaine, 1966; Geldreich et ai., 1968; Weibel et al., 1964). However, in several instances (Dutka, 1977; Evans et al., 1968; Sartor et al., 1974) pathogenic bacteria were also isolated in runoff waters, demonstrating the existence of a potential health hazard. Although little conclusive data are available on the time-related distribution of indicator and pathogenic bacteria in stormwater runoffs, it has generally been assumed that the majority of micro-organisms, both indicator and pathogenic, are found in the first portion or initial flushing of stormwater. Based on the above, it has been suggested that, by containing and treating a speofic portion of the initial runoff, the majority of bacterial health hazards would be eliminated from receiving waters. These assumptions and suggestions crystallized into a joint Canadian federal/ provincial Government project to investigate their vafidity and usefulness. Since little reported data are available on the microbiological characteristics of urban stormwater runoffs in Canada, it was necessary to obtain these data from
A.A. QURESHIand B. J. DUTKA
978
typically u r b a n drainage areas to support or refute the potential a n d practicality of the c o n t a i n m e n t and disinfection hypothesis. The results reported here are based on studies which were conducted over a twoyear period at two residential and one commercial area. MATERIALS AND METHODS
Description of the .study sites (a) A storm sewer outfall into a small Burlington creek near Malvern Road in Burlington, Ontario (population 104,000) was one of the study sites. The Malvem Road drainage area is approximately 2.3.3 ha, and is situated in central Burlington. The entire area is zoned for single family residences and there are no vacant lots within the area. Most of the houses were built in the early 1960's with virtually all development completed b y 1964. The majority of houses in this area have their eaves troughs connected to storm sewers which are 100~ separated, (b) The Aldershot catchment area is a 6.88 ha commercial plaza in the western section of Burlington. The imperviousness of the catchment area is I 0 0 ~ with roofs, sidewalks and a paved parking lot making up 100~ of the area. The plaza contains one large department store, a Canadian Tire workshop and gasoline pumping station, one large chain grocery store and 15-20 small boutiquetype stores. The area has 100% separate storm sewers. (c) The third site (Barrington Avenue) was located in the Borough of East York (population 103;000), part of which is in the City of Toronto. With the exception of five or six corner stores, the area is composed entirely of single family residential housing ranging from 50 to 70 years in age. The site has 100% separate storm sewers with a total drainage area of 22.7 ha. The area containing buildings not connected to the storm sewer system is approximately 5.3 ha.
Sample collection Various types of sample collection procedures were used in this study. At the Malvern Road site, bacteriological samples were hand-collected at the weir outfall in sterile glass bottles. At the first indication of a rainfall, a technician would arrive at the sample collection site and wait for the first drops of rain. When the rain started, the first sample would be collected as soon as there was a noticeable change in the flow rate and this sample was labelled "'0" minute. Samples were then collected 10, 20, 30, 45, 60. 75, 90, 105, 180 and 240min after the "0" minute sample. Since Aldershot Plaza sampling site was at the bottom ofa manbgle, samples were collected by means of a North Hants automatic sampler using sterile collection bottles, This sampler was triggered by a 5 cm rise in water level and would automatically collect samples at 20 rain intervals as long as the water level rise was equal to, or greater than, 5 cm. At the East York site, water samples were collected manually, in sterile glass bottles, every 5 rain for a period of approximately one hour after the onset of a rainfall event. For these samples, a technician was dispatched to the sample site soon after the rainfall began. Unless otherwise specified, the first sample was collected within 15 rain of the initiation of a storm event, On two occasions when no rainfall occurred, sediment samples were collected by hand in sterilized Nalgene widemouth jars from the East York site for Salmonella analysis. For qualitative detection of salmonellae, mOdified Moore swabs (Dutka & Bell, 1973) were used. These were exposed to stormwater for varying periods during each rainfall event,
At the Aldershot site, eight infiltration samples were collected during dry periods from June to September, 1975. In" addition, during May to November, 1976, ten infiltration samples were collected from the storm sewer at the Malvern site.
Microbiological analyses All stormwater and infiltration samples were tested for total coliform, fecal coliform, fecal streptococcus and Pseudomonas aeruvinosa densities using the membrane filtration technique. Populations of heterotrophic bacteria and fungi were enumerated by using the spread plate technique. The details of the media and procedures used for the~e analyses are outlined by Dutka (1975) and Qureshi (1977). For qualitative detection of salmonellae, modified Moore swabs were processed following the .procedure of Dutka & Bell (1973). Storm water samples in variable allquots (ranging from 10 to 400ml) were filtered through 47 mm sterilized fiberglass prefilters (Sartorius SM 13400). The filters were aseptically placed in selective enrichment broths for the isolation and identifications of salmonellae following the procedures described by Dutka & Bell (1973) and Qureshi (1977). For determining the relative distribution of coliform and fecal coliform biotypes, isolates were collected from selected infiltration and stormwater samples and identified using procedure described by Dutka & Tobin (1976). RESULTS Twelve storm events were monitored at the Malvern site during April 21 to October 24, 1976. The concentrations of indicator organisms in the runoff water varied considerably during these events which were of different intensities and duration, Examples of two of the events monitored are shown in Figs. 1 and 2. Figure 1 displays the microbiological data obtained from a very heavy rainfall (101 ram) which lasted for 240 rain. During this event, the m a x i m u m populations occurred 75 rain (fecal coliforms, fecal streptococci), 90 min (fungi), 105 min (eoliforms) a n d 150 min (heterotrophs) after the storm began. Salmonellae were isolated from a 100 ml water sample collected at the 90 rain mark. The event depicted in Fig. 2 was also of 240rain duration, but only 9 m m rain fell during this storm with m a x i m u m populations occurring between 75rain
(P. aeruginosa) and 150 rain (heterotrophs) period. N o salmonellae were isolated from water samples collected during this event. This event was of intermittent nature a n d provides a typical example of a slow a n d gentle rain which results in a gradual increase in the microbial population as the main flow hits the weir. At the Malvern site, salmonellae were only isolated during four of the 12 events from the 10, 90 and 240 rain samples through filtration of 100 ml runoff water, and from the modified M o o r e swabs exposed to stormwater for 30 rain. Salmonella thompson and S. typhimurium var. copenhagen were the two species isolated a n d identified. The results of ten infiltration samples collected at this site between M a y 10 a n d N o v e m b e r 30, 1976, are presented in Table 1. The data indicate that low levels of indicator bacteria and pathogens (P: aeru-
Microbiological
979
studies
o
Coliforms/IOOml Fungi/IOOmL [] Heterotrophs/m( - ' ~ Salmonellae isolation
• • •
Fecal coliforms/IOOmL Fecal streptococci/IOOmL P. aeruginosa/IOOmL
io 5 =--
E .~
104
103
o¢) 103
10
0 15 30456075 90105120 150 Time of collection,
180 min
240
0 IS 3045 60 7~ 901051~0 150 180 Time of collection, min
240
Fig. 1. Distribution and concentrations of micro-organisms in stormwater runoffs, June 24 1976,
Malvern Road (Burlington) site.
,oinosa) are being continuously discharged from the storm sewer into the receiving creek waters Table 2 summarizes the coliform and fecal coliform genera/ species distribution in stormwater and infiltration samples collected from the Malvern site. It is interesting to note that the distribution was similar throughout various periods of the storm and that, among coliforms in runoff waters, approximately 45~o of the isolates were E. coil and the rest belonged to Klebsiella (23-31~o), Enterobacter (16-22~) and Citrobacter (6-10%). Furthermore, a greater percentage of E. coil were found in infiltration samples as compared
I
o ~ r~
tO6~_
~,~
with runoff waters In both the infiltration and runoff samples, all fecal coliforms belonged to E. coil Microbiological data from one of the five rainfall events, monitored during June 19 to September 9, 1975, at the Aldershot Plaza, are shown in Fig. 3. Sample collection problems plagued this sampling site. Because of the imperviousness of the drainage area, the runoff was very quickly channeled into the storm sewers where this fast moving and developing water mass, upon reaching the sampling site, frequently demolished and swept away the sampling equipment. Thus at this site only slow and intermit-
Coliforms/IOOmL Fungi/IOOml. Heterotrophs/mL
• • •
IO5
i04
IO4
I0 3
io
io 2
I-.)~d=
I
u I
t I
a
0 15 3 0 4 5 6 0 7 " 5 9 0 1 0 5 1 2 0
l
I
I
I
150
180
240
Time of collection, Fig. 2. Distribution
min
ko~/-k J- J
I
I
Fecal collforms/lO0 mL Fecal streptococci/100 mL P. oeruginoso/lOOmL
I
I
0 15 3 0 4 5 6 0 7 ' 5 90105120
I
1
I
150
180
240
Time of collection,
and concentrations of micro-organisms in stormwater MaJvern Road (Burlington) site.
rain
runoffs, October 19 1976,
980
A. A, QURESHI and B. J. DUTKA Table 1. Densities of micro-organisms in infiltration samples from Malvern Road (Burlington) site, 1976 Microbial parameters per 100 ml Fecal Fecal Pseudomonas coliforms streptococci aeruoinosa
Date
Total coliforms
May 10 May 30 June 14 July 20 Aug. 17 Aug. 30 Sept. 29 Oct. 12 Nov. 2 NOV. 30
3.0 1 9.0 3.0 5.8 x 102 17.0 4.4 x 102 1.2 × l0 s 5.3 x 103 1.3 x 102 4.0 × 10 3 1.4 x 10a 5.6 x 103 1.8 x I03 6.0 x l02 2.0 x 102 4.5 x 102 . 83.0 1.2 x 102 ll.0
13.0 16.0 3.4 × 10z 1,4 x 102 9.0 x 102 3.4 x 102 1.2 × l02 40.0 1.1 x 102 21.0
tent rainfall events were monitored; microbiological data from one such event (7.9 mm rainfall) are presented in Fig. 3. The rainfall began at 12:30p.m. and the first sample was collected at 12:45 p.m. Maximum fecal streptococcus and fungal densities occurred within 15 min of rainfall initiation, while the highest concentrations of total coliform and P. aeruginosa occurred 40 min after the commencement of the storm, At the Aldershot site, salmonellae (S. senftenberO and S. newport) were isolated from the modified Moore swabs left in the manhole for the duration of two separate events. Infiltration data from this site are presented in Table 3. The densities of total coliform (2.9 x 10a-2.2 x 10~/100ml) and P. aeruginosa (14-3.0 x 10a/100ml) in these waters were equivalent to those usually found in dilute sewage. Coliform isolates from one of these infiltration samples showed the following distribution pattern: Aeromonas sp. 50%, Klebsiella sp. 45~./~ and E. coli 5% (Table 2). Stormwater runoffs from four events were monitored at the Barrington Avenue (East York) site, the results from two of these events are illustrated in Figs. 4 and 5. A small m o u n t (2.3 mm) of rain fell during the October 1 1975 event which lasted for only 30 min. Sample collection started within 15 min of the onset of the rainfall and continued for 40 min after the end of the storm. As shown in Fig. 4, all popula-
t 3.0 3.9 × 102 10.0 7.0 × 102 7.4 x 104 10.0 9.0 I 33.0
Total fungi
Heterotrophs per ml
13.0 9.0 80.0 60.0 1.0 x 102 43.0 1.2 × 102 4.0 x 102 80.0 13.0
4.0 1.2 1.7 3.3 6.6 8.1 9.0 1.6 1.1 5.9
x × x x x x x x x x
10a l0 s l0 s 104 10" 103 103 l0 ~ 10'* 103
tions enumerated showed a sharp increase within the first I0 rain of collection with coliform populations fluctuating to a final peak at the 35 min mark, 50 rain after the rainfall began. Salmonellae were isolated from 10ml stormwater samples collected at the 15 min (S. saint-paul~ 20 and 25 rain periods (S, typhimurium var. copenhagen). S. typhimurium var. copenhagen was also isolated from a 50 ml aliquot of the runoff sample collected at the 30 rain mark, No salmonellae were isolated from the modified M o o r e swab during this storm event. The event shown in Fig. 5 was unusual in the 8¢nt~ that the ground was frozen and thus rather impcrvious so that the runoff was compoaed mainly of rainwater and melting snow. A total of 10.9ram rainfall occurred during this storm which lasted for 735 rain. The rainfall began at 3.15a.m. with the first sample being collected at 9.45 a.m., arid the most intensive period of rainfall (2.5 mm) occurred during the 55 rain sampling period. The maximum concentrations of total coliform, fecal coliform, fecal streptocoeus and fungi were observed in samples collected at 45-55 minute marks. P. aeruainosa populations were unusually high during the collection period espedally as P. aeruginosa are not noted for their ability to survive at freezing temperatures. N o salmonellae were isolated from either the modified Moore swab or stormwater samples during this event.
Table 2. Coliform and fecal coliform distribution in stormwater and infiltration samples from Malvem Road and Aldershot Plaza Stormwater runoffs (Malvern Road) 0-30 min 60-90 min 120--240 min
Genus/species
E, coli Klebsiella Emerobacter Cttrobacter Aeromonas
Infiltration Malvcm Road Aldershot Plaza
Fecal Fecal Fecal Fecal Coliforms coliforms Coliforms coliforms Coliforms coliforms Coliforms coliforms (%) (%) (%) (%) (~o) (%) (%) (%) 45 23 22
l0
98 2
44 31 16
9
100
46 29. 19
6
100
60 29 10
100
Coliforms (%) 5 45
1 50
Microbiological studies
981
1.8 x I 0T/e\ / i°7-
\
I
\
/
.....
//
\
/
\
\\\
//
IOE Z---
-
\\
/~
_ _
/
/ /
Total coliforms " Fecal stroptococci P. oeruginosa Fecal coliforms Fungi .
\
I
b.,. ~
",. ~
~,,,,e,~
"e~
"'--..
-~ ,o;
io21 12t45
I 12:55
I 13:15
I3:05
I 13:25
I 13:35,
13:45
I 13:55
I 14:05
Time of collection
Fig. 3. Distribution and concentrations of micro.organisms in stormwater runoffs, August 21 1975, Aldershot Plaza (Burlington) site.
Two s e d i m e n t samples collected from the East York weir under dry weather conditions were examined for Salmonella incidence. Whereas, the September 29 1975 sample yielded no salmonellae, S. typhtmurium v~r. copenhagen was found in a 25 g (wet weight) aliquot of the November 4 1975 sample. It is interesting to note that, at this site, the same Salmonella serotype had previously been isolated from
the October 1 1975 runoff and later from the January 26 1976 storm events. DISCUSSION In the present study, the most reliable data on the distribution of indicator organisms and pathogens in stormwater runoffs was obtained only at the Malvern
Table 3. Densities of micro-organisms ifi infiltration samples from Aidershot Plaza (Burlington) site, 1976 Total coliforms
Date June 19 June 23 July 2 July 7 July 16 July 29 Aug. 18 Sept. 9
>1.5 > 1.0 6.7 5.6 2'2 9.0 2.9 2.6
* -- Not analyzed.
x × × x x x x x
l0 s 105 10a 106 l0 T 103 103 106
Microbial parameters per 100 ml Fecal Fecal Pseudomonas coliforms streptococci aeruginosa 7.5 4.1 1.0 2.8 3.1 3.1 1.4 2.1
x x x x x x x x
103 103 102 102 102 102 102 103
1.8 1.2 7.1 5.1 6.7 2.1 5.5 1.6
× × × x x x x ×
103 102 10z 103 102 102 103 102
2.6 x 2.6 x 3.Ix 1.7 x 2.7 x 1.4 x 3.0 x 1.4 x
103 103 102 103 103 10t 103 102
Total fungi NA* NA NA NA NA 2.0 x 106 2.0 x 104 NA
982
A.A. QURESH[ and B. J. DUTKA
o
Coli forms Fungi •--...,-- Sal monelloe isolation
• •
10 7
107
105
105
Fecal coliforms Fecal streptococci
0 0
c:
0
I0 ,5 20 25 30 35 40 45 50 55 Time of collection,
0
.5 ,0 15 20 25 30 35 40 45 5 0 5 5
rain
Time of collection,
rain
Fig. 4. Distribution and levels of micro-organisms in stormwater runoffs, October 1 1975, Barrington Avenue (East York, Toronto) site.
o ,~
0
0
Coliforms Fungi
• •
Fecal coliforms Fecal streptococci aeruginosa
• F)
106~
106
)05
105
104
t04
,o1,
E
~
102 0
I I I I t 1 I I i 1 I 5 10 15 20 25 30 35 40 45 ~)0 55 Time of c o l l e c t i o n ,
Fig.
5. D i s t r i b u t i o n
and
102 0
rain
levels o f ~ o - o r M a f i s m s
I 5
,,.-4
I Y l I I I, I ~ t IO 15 20 2~ 30 35 40 45 ~ ) 55 T i m e of colle©tton,
in
stormwa~r
runoffs,
Barrinston Avenue (East York, Toronto) site.
rain
De~mlx~
30 1975,
Microbiological studies
983
Road site. This reliability was due to the sampling populations during the short 55 min sampling period. procedure followed as the sampler, upon hearing No relationships or trends were evident as the peak storm forecasts, actually waited at the site until it microbial populations occurred either in the initial rained and then collected the samples, At the Malvern stages, middle or tail-end of the sampling period of site, maximum microbial populations generally a variety of storms monitored. Furthermore, though occurred 60-135 rain after the normal infiltration flow some variations were observed, generally the initial in the weir was observed to change. This change counts(in 0-10rain samples)of indicator bacteria and usually occurred within 5-15 rain of a rainfall com- fungi were either at about the same level or slightly mencing, depending on the initial intensity of the rain. higher than the counts from 15-55 rain samples. LikeSalmonellae, which were infrequently detected at this wise, salmonellae were isolated at different times site, exhibited no consistent distribution pattern as throughout the sampling period. These data indicate the isolations were made throughout the 240 rain that any effect of initial flushing on the microbial quasampling period. These observations lend support to lity of the discharges was minimal during an indivithe assumption that all portions of stormwater dual storm. These findings also indicate that short runoffs may contain potential health hazards, interval/period sampling scheme is probably not suitThe Malvern Road coliform and fecal coliform iso- able for determining the incidence and distribution late data indicate that similar proportions of Entero- of peak populations of different micro-organisms in bacteriaceae are being discharged throughout the stormwater runoffs. 240min sampling periods. These data are supportive The December 30 1975 event is unique in that, we of the belief that, although there may be an initial believe, it provided the first microbiological runoff flush of animal and bird feces when a runoff first de- data representing the effects of a mid-winter, rainfall velops, the Enterobacteriaceae stormwater distribu- on frozen snow-covered ground. Although the first tion pattern is indicative of the Enterobacteriaceae sample was collected 390 min after the rainfall begun, distribution on surfaces and in soils, substantially high (103-105/100 ml) levels of indicator Aldershot Plaza data are unique in that they rep- bacteria and fungi were present in all runoff samples resent a totally impervious drainage area. Stormwater collected during this event. This further substantiates samples were difficult to collect due to the rapid earlier observations that initial flushing has little effect runoff and the necessity of the water to rise to a on the microbiological quality of stormwater runoffs. specific level to trigger the automatic sampling mech- In addition, there are several questions which arise anism. At this site, maximum microbial populations from these data. Are snowfalls in urban areas an unalways occurred within the first hour of a rainfall suspected reservoir of pathogenic organisms and indiprobably due to the impervious nature of the cator bacteria? Where do substantially high concertdrainage area which allowed the collection of samples trations (10s/100 ml) of fungi come from? What are only from small intermittent rainfalls, the sources of the observed high levels of coliforms, Aldershot Plaza infiltration data (Table 3) showed fecal coliforms and fecal streptococci in these runoff very high background densities of coliform samples? During this event, the ground was frozen (2.2 x 107), fecal coliform (7.5 x l03) and fungi and relatively impervious to the rain, therefore, the (2.0 x 106). These elevated populations, possibly due rainfaU-melting snow mixtures were probably responto sewage line leaks or regrowth within the lines, are sible for the strikingly high populations of these being consistently inoculated into receiving waters, organisms. This suggests that snowfall/slush in urban Thus it is probable that such uncontrolled inputs help areas may harbor and preserve micro-organisms (esto maintain elevated population levels and potential pecially of animal fecal origin) which eventually reach health hazards in inshore receiving waters all year storm sewers and receiving waters. High concenround, trations of indicator bacteria encountered in sediDifferences were observed in the distribution pat- ments and the findings of a Salmonella serotype in tern of coliforms in infiltration samples from the two one sediment sample suggests that the sediments are monitored sites (Table 2). While Aeromonas was not yet another source and contributor of these organisms isolated from the Malvern Road, at the Aldershot site to the recipient waters. approximately 50% of the coliform isolates were AerAt all sites and during each event monitored, the omonas sp. Furthermore, at the Aldershot Plaza, only densities of traditional indicators (total coliform, fecal 5~o of the coliform isolates were E. coli as compared coliform and fecal streptococcus) approached concento 50% at the Malvern site. These differences may trations found in dilute raw sewage, thus ro-emphasizbe attributed to different land uses and drainage ing the health hazards due to pathogenic bacteria and characteristics at these two site~ .viruses (Olivieri et al., 1977) which are contained In the East York study, no "zero" minute sample within stormwater runoff waters. One of the indicator was collected during any of the storms monitored organisms used in this study, P. aeruginosa, is also since considerable time elapsed between the start of . a pathogen. This organism has been implicated in eye. rainfall and technician's arrival at the site. However, ear, skin and upper respiratory tract infections and is stormwater samples were collected at regular (5 rain) regarded as a major etiological agent of otitis externa intervals to ascertain distribution trends of microbial among swimmers (Young & Armstrong, 1972: Hoad-
A, A. QURESHIand B. J. DUTKA
984
ley, 1968). Thus the increased P. aeruginosa populations discharged into our receiving waters, many of which are used for recreational purposes, constitute an elevated risk not previously suspected and investigated, The mycological procedures used during this study did not differentiate between saprophytic and invasive pathogenic fungi (including yeasts). It is known that both types will grow on the media used. Therefore, the striking increase seen in fungal populations during most rainfalls should be cause for concern especially as many of the invasive fungi do so through skin contact. Thus these storm runoff waters are contributing another heretofore unsuspected group of potential pathogens into receiving and recreational waters. The results of this study corroborates findings reported by previous investigators (Evans et al., 1968; Geldreich et al., 1968; Olivieri et al., 1977) and demonstrated the existence of potential health hazards in stormwater discharges. Moreover, the results also show the seriousness of urban stormwater runoffs as a major factor in "nonpoint" source pollution of receiving surface waters,
Salmonella serotypes found in this study have also
been isolated from humans in Canada during the past several years. 5. This study shows that discharges from separate storm sewers could be a major source of microbial pollution to receiving waters and reservoirs, and that it is not possible to realistically decrease public health risks by containing and disinfecting some portions of these discharges. Acknowledgements--This research was financially supported, in part, by the Government of Canada and the Government of the Province of Ontario under CanadaOntario Agreement Projects 74-8-25, 75-3-24 and 76-8-41.
REFERENCES BenzieW. J. & Courchainc R. J. (1966) Discharges from separate storm sewers and combined sewers, d. Wat. Pollut. Control Fed. 38, 410-421. Bradford W. L. (1977) Urban stormwater pollutant loadings: a statistical summary through 1972. J. War. Pollut. Control Fed. 49, 613-622. Burro R. J. & Vaughan R. D. (1966) Bacteriological comparison between combined and separate sewer discharges in Southeastern Michigan. J. War. Pollut. Control Fed. 38, 400--409.
CONCLUSIONS
Dukta B. J. (ed.)(1975) Methods for microbiological analysis of waters, wastewaters and sedimenta IWD, SOD. 1. Discharges from all three storm sewer systems Canada Centre for Inland Waters, Burlington, Ontario. contained significant quantities of pollution indicator Dutka B. J. (1977} Microbiological study of storm runoff bacteria. Among the pathogenic micro-organism, P. watersfrom a 100% residential area in Canada. Can. Res. 10, 50-53. aeruainosa were the most numerous and frequently Dutka B. J. & Bell J. B. (1973) Isolation for salmonellae isolated. Salmonellae were detected frequently in from moderat~lypolluted waters. J. Wat. Pollut. Control stormwater runoffs and, in several instances, were Fed. 45, 316-324. readily isolated from as little as 10 ml aliquots of Dutka B. J. & Tobin S. E. (1976) Study on the efficiency of four procedures for enumerating coliforms in water. stormwater. There was no predictable pattern of SalCan. J. Microbiol. 22, 630-635. monella isolation; they were found throughout the Evans F. L. GeldreichE. E., Weibel S. R. & Robeck G. G. various sampling periods. (1968) Treatment of urban stormwater runoff. J. War 2. Infiltration waters appear to be a source of low Pollut. Control Fed. 40, 162-170. level but continuous microbial pollution. Similarly, Geldreich E. E., Best L. C., Keaner B. A. & van Donsel D. J. (1968) The bacteriological aspects of stormwater sedimentsandsnowmayennstitutereservoirsofmicropollution. J. Wat. Pollut. Control Fed. 40, 1861-1872. organisms which ultimately find their way into storm- Hoadley A. W. (1968) On the significanceof Pseudomanas water runoffs and receiving waters, aeruoinosa in surface waters. J. New Enol. Water Wks 3. Little relationship was observed between the inAss. 82, 99-111. Kothandaraman V. (1972) Water quality characteristics of tensity and amount of rainfall and the in,,idence of storm sewer discharges and combined sewer overflows. indicator bacteria and pathogenic micro-organisms. Circular 109. Illinois State Water Survey, Urbana. pp. As a result, no predictable maximum microbial den1-18. sity pattern could be established during this study. Olivieri V. P., Kruse C. W., Kawata K. & Smith J. E. The unpredictable and intermittent appearance of (1977)Microorgamsms in urban stormwater. EPA, Cincinnati, Ohio, EPA-600/2-77-087. micro-organisms in stormwaters suggest that any Qureshi A. A. (1977) Microbiolo$ical characteristics of effect of initial flushing on microbiological quality of stormwater runoffs at East York (Toronto) and Guelph the discharges was minimal during an individual storm sewers. Ministry of the Environment, Ontario. storm. Canada, p. 57. 4. At all three sites, the levels of microbial poputa- Sartor J. D., Boyd G. B. & Agardy F. J. (1974) Water pollution aspects of street surface contaminants. J. Wat. tions in stormwater runoff were strikingly high Pollut. Control Fed. 46, 458-467. throughout the entire sampling period and many van Donsel D. J., Geldreich E. E. & Clarke N. A. (1967) times approached densities found in dilute raw wasteSeasonal variations in survival of indicator bacteria in waters and, therefore, constitute a health hazard. The soil and their contribution to stormwater pollution. Appl. Microbtol. 1~, 1362-1370. implied public health risk is substantiated by the re- Weibel S, R., Anderson J. R. & Woodward R. L, (1964) covery of pathogenic and potentially patho$mtic bacUrban land runoff as a factor in stream pollution. J. teria in discharges from the sites studied. Moreover, War. Pollut. Control Fed. 36, 914-924.
Microbiological studies Weibel S. R., Weidner R. B., Christianson A. G. & Anderson R. J. (1966) Characterization, treatment and disposal of urban stormwater. In Advances in Water Pollution Research. Proc. 3rd. International Conf War. Pollut. Res.
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Vol. 1, pp. 329-359. Port City Press, Baltimore, Maryland, U.S.A. Young L. S. & Armstrong D. (1972) Pseudomonas aeruginosa infections. Crit. Rev. Clin. Lab. Sci. 3, 291-347.