Quantification of human-associated fecal indicators ...

Water Research 100 (2016) 556e567

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Quantification of human-associated fecal indicators reveal sewage from urban watersheds as a source of pollution to Lake Michigan Hayley A. Templar a, Deborah K. Dila a, Melinda J. Bootsma a, Steven R. Corsi b, Sandra L. McLellan a, * a b

School of Freshwater Sciences, UW-Milwaukee, 600 E. Greenfield Ave, Milwaukee, WI 53204, USA U.S. Geological Survey, 8505 Research Way, Middleton, WI 53562, USA

a r t i c l e i n f o

a b s t r a c t

Article history: Received 25 January 2016 Received in revised form 6 May 2016 Accepted 17 May 2016 Available online 19 May 2016

Sewage contamination of urban waterways from sewer overflows and failing infrastructure is a major environmental and public health concern. Fecal coliforms (FC) are commonly employed as fecal indicator bacteria, but do not distinguish between human and non-human sources of fecal contamination. Human Bacteroides and human Lachnospiraceae, two genetic markers for human-associated indicator bacteria, were used to identify sewage signals in two urban rivers and the estuary that drains to Lake Michigan. Grab samples were collected from the rivers throughout 2012 and 2013 and hourly samples were collected in the estuary across the hydrograph during summer 2013. Human Bacteroides and human Lachnospiraceae were highly correlated with each other in river samples (Pearson’s r ¼ 0.86), with average concentrations at most sites elevated during wet weather. These human indicators were found during baseflow, indicating that sewage contamination is chronic in these waterways. FC are used for determining total maximum daily loads (TMDLs) in management plans; however, FC concentrations alone failed to prioritize river reaches with potential health risks. While 84% of samples with >1000 CFU/ 100 ml FC had sewage contamination, 52% of samples with moderate (200e1000 CFU/100 ml) and 46% of samples with low (200, ≤ 1,000 CFU/100ml)

(≤ 200 CFU/100ml)

84% Sewage Positive

52% Sewage Positive

46% Sewage Positive

38 samples / 73 total



12

12

10

10

10

8 6 4 2

Number of Samples

12

Number of Samples

Number of Samples

3.5. Event loading of human-associated indicators in the Milwaukee estuary

8 6

4 2 0

0 MKE MN MN MN MN MN KK KK KK KK RI-15 RI-36 RI-22 RI-32 RI-09 RI-20 RI-33 RI-34 RI-35 RI-13

Sewage Positive

Sewage Negative

8 6

4 2 0

MKE MN MN MN MN MN KK KK KK KK RI-15 RI-36 RI-22 RI-32 RI-09 RI-20 RI-33 RI-34 RI-35 RI-13

Sewage Positive

Sewage Negative

MKE MN MN MN MN MN KK KK KK KK RI-15 RI-36 RI-22 RI-32 RI-09 RI-20 RI-33 RI-34 RI-35 RI-13

Sewage Positive

Sewage Negative

Fig. 3. Distribution of samples which exceeded the threshold for a positive sewage detection under three fecal coliform concentration levels, across sampling locations in the Milwaukee (MKE), Menomonee (MN), and Kinnickinnic (KK) Rivers in metropolitan Milwaukee, Wisconsin in 2012 and 2013. Sites are listed from upstream to downstream in each river.

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Fig. 4. Human Lachnospiraceae concentrations from river samples collected in metropolitan Milwaukee, Wisconsin in 2012 and 2013, plotted in order of high to low human Bacteroides concentrations with corresponding fecal coliform concentrations.

Table 3 Spearman’s rank correlations (rho) between human Bacteroides (HB), human Lachnospiraceae (Lachno2), ammonia (NH3), turbidity, and chloride (Cl) under various weather conditions in river samples collected in Milwaukee, Wisconsin in 2012 and 2013. Asterisks indicate tests that were significant at p 0.05. Spearman’s rank correlations (rho)

Baseflow (n ¼ 51)

Wet weather

CSO

Combined sewer area (n ¼ 36)

HB Lachno2 a b

Separated sewer area (n ¼ 82)

Combined sewer area (n ¼ 5)

NH3

Turbidity

Cl

NH3

Turbiditya

Cl

NH3

Turbidityb

Cl

NH3

Turbidity

Cl

0.11 0.10

0.07 0.11

0.14 0.10

0.34* 0.50*

0.21 0.15

0.37* 0.50*

0.28* 0.25*

0.37* 0.40*

0.37* 0.43*

0.60 0.50

0.60 0.40

0.10 0.10

Wet weather turbidity correlations in the combined sewer area consist of 33 samples. Wet weather turbidity correlations in the separated sewer area consist of 75 samples.

Table 4 Maximum 24-h mean event concentrations and loads of human-associated indicators, human Bacteroides (HB) and human Lachnospiraceae (Lachno2), for seven wet and dry weather events sampled in the Milwaukee estuary at Jones Island water reclamation facility in Milwaukee, Wisconsin in 2013. Event number

1 2 3 4 5 6 7

Dates

5/21-5/23/2013 5/28e6/2/2013 6/12e6/14/2013 7/19e7/20/2013 8/8e8/9/2013 8/11e8/12/2013 8/22e8/23/2013

Number of samples

17 48 17 6 6 10 14

Duration (hours)

37 122 34 24 24 24 29

Total rainfall depth (mm)

22.6 33.3 32.0 0.0 0.0 4.1 13.5

Maximum 24-h mean concentration (CN/100 ml)a

Maximum 24-h mean load (CN)a

HB

HB

2100 15,000 105,000