A mixed-method examination of risk factors in the truck-to-cistern drinking water system on the Beardy’s and Okemasis First Nation Reserve, Saskatchewan

Figures & data

Figure 1. Truck-to-cistern drinking water supply chain.

Table 1. Sampling and handling requirements revised from Standard Methods for the Examination of Water & Wastewater 2005.

Parameter	Suitablecontainer	Minimum sample size	Sample type	Preservation	Sample-holding times
					Recommended	Regulatory
General chemical/water quality – on-site analysis Equipment – YSI multi-parameter probe, portable colorimeter
Chlorine: total, free, residual	Plastic, glass	500 mL	Grab	Analyze immediately	0.25 h	0.25 h
pH	Plastic, glass	50 mL	Grab	Analyze immediately	0.25 h	0.25 h
Temperature	Plastic, glass	-	Grab	Analyze immediately	0.25 h	0.25 h
Turbidity	Plastic, glass	100 mL	Grab	Analyze same day: store in dark up to 24 h, refrigerate	24 h	48 h
Bacteriological parameters – Saskatchewan Disease Control Laboratory, Environmental Services, Regina, SK
Total coliform	*Sterile plastic	250 mL	Grab	Refrigerated conditions	48 h	48 h
E. coli	*Sterile plastic	250 mL	Grab	Refrigerated conditions	48 h	48 h

^* The 250-mL bacteriological bottles are sterilized and are obtained directly from the Saskatchewan Disease Control Laboratory (5 Research Drive, Regina, SK, Canada, S4S 0A4).

Grab samples are single samples collected at a specific spot, over a short period of time (seconds or minutes).

Sample-holding time is the time period from sample collection to sample analysis.

Table 2. Water sampling timeline – all water quality parameters.

Water sampling timeline^*	Sampling site
2014 sampling period	(i) Source: water treatment facility	(ii) Water holding truck delivery	(iii) Cistern	(iv) Consumers’ taps, cold	Sample totals
June	2	2 trucks × 10 days = 20	60	60	142
July	2	2 trucks × 10 days = 20	60	60	142
August	2	2 trucks × 10 days = 20	60	60	142
September (or October)	2	2 trucks × 10 days = 20	60	60	142
Total samples:	8	80	240	240	568

^* Timeline and sampling analysis were confirmed following consultation with Saskatchewan Disease Control Laboratory Supervisor (5 Research Drive, Regina, SK, Canada, S4S 0A4).

Table 3. Descriptive summary of water culture statistics, July–October 2014.

		Frequency
Variable	N	Positive samples	%	5th percentile	Median	95th percentile	Maximum
WATER PLANT
Total coliforms	8	0*	0.0	0.0	0.0	0	0
E. coli	8	0*	0.0	0.0	0.0	0	0
TRUCKS
Total coliforms	81	21	25.9	0.0	0.0	17	> 100
E. coli	81	0	0.0	0.0	0.0	0	< 1
CISTERNS
Total coliforms	232	90	38.8	0.0	0.0	44	> 100
E. coli	232	3	1.3	0.0	0.0	0	1
TAPS
Total coliforms	228	70	30.7	0.0	0.0	32	> 100
E. coli	228	2	0.9	0.0	0.0	0	9

^* No detectable coliforms or E. coli.

Table 4. Descriptive statistics for water quality parameters, July–October 2014.

Variable	Average	Standard deviation	N	5th percentile	Median	95th percentile
TRUCKS
Total chlorine (mg/L)	1.41	0.23	82	1.12	1.41	1.81
Free chlorine (mg/L)	1.29	0.25	82	0.79	1.33	1.68
Turbidity (NTU)	0.11	0.13	82	0.01	0.07	0.36
Temperature (°C)	9.2	1.2	81	7.6	9	11.4
CISTERNS
Total chlorine (mg/L)	0.92	0.33	235	0.32	0.94	1.39
Free chlorine (mg/L)	0.81	0.32	235	0.17	0.84	1.29
Turbidity (NTU)	0.46	1.64	235	0.03	0.13	1.39
Temperature (°C)	10.8	1.4	235	8.8	10.7	13.2
TAPS
Total chlorine (mg/L)	0.92	0.73	231	0.19	0.91	1.39
Free chlorine (mg/L)	0.77	0.35	231	0.09	0.81	1.25
Turbidity (NTU)	0.71	3.45	231	0.02	0.12	2.14
Temperature (°C)	11.6	1.6	231	9.1	11.6	14.6

Table 5. Unadjusted associations between potential risk factors and presence of total coliforms.

Risk factor	Odds ratio	95% CI		p
		Lower	Upper
Location: hruck
Sample month:				0.03
July to October	0.20	0.01	2.72	0.21
August to October	5.84	0.99	34.4	0.05
September to October	1.38	0.25	7.53	0.69
Temperature (°C)	1.44	0.94	2.21	0.09
Turbidity (NTU)	0.34	0.004	29.7	0.63
Total chlorine (0.1 mg/L)	1.77	1.26	2.50	0.001
Free chlorine (0.1 mg/L)	1.48	1.10	1.99	0.01
Location: house
cistern vs tap	1.42	1.02	1.97	0.04
Sample month:				< 0.001
July to October	1.07	0.54	2.14	0.85
August to October	4.42	2.24	8.70	< 0.001
September to October	0.63	0.32	1.21	0.16
Temperature (°C)	1.06	0.94	1.21	0.34
Turbidity (NTU)	1.00	0.93	1.08	0.95
Total chlorine (mg/L)	0.68	0.38	1.22	0.19
Free chlorine (mg/L)	0.86	0.45	1.63	0.64

CI: confidence interval.

Table 6. Final multivariable model for factors associated with total coliforms (count/mL).

Risk factor	Odds ratio	95% CI		p
		Lower	Upper
Location: truck
Sample month:				0.13
July to October	0.66	0.03	13.6	0.77
August to October	7.18	0.99	51.8	0.05
September to October	2.29	0.33	15.9	0.38
Total chlorine (0.1 mg/L)	1.68	1.14	2.46	0.01
Location: house
Cistern vs tap	1.51	1.07	2.13	0.02
Sample month:				< 0.001
July to October	1.17	0.58	2.38	0.66
August to October	4.69	2.35	9.38	< 0.001
September to October	0.63	0.33	1.23	0.18

CI: confidence interval.

Table 7. Unadjusted associations between potential risk factors, chlorine concentrations and turbidity.

	Difference	95% CI		p
		Lower	Upper
Total Cl (mg/L)
Location: truck
Sample month:				< 0.001
July to October	−0.319	−0.475	−0.164	0.001
August to October	0.012	−0.150	0.175	0.88
September to October	−0.099	−0.243	0.044	0.16
Turbidity (NTU)	−0.120	−0.538	0.298	0.57
Temperature (°C)	0.030	−0.014	0.075	0.18
Location: house
Cistern vs tap	0.005	−0.083	0.092	0.92
Sample month:				< 0.001
July to October	−0.020	−0.168	0.129	0.80
August to October	−0.158	−0.308	−0.009	0.04
September to October	−0.252	−0.395	−0.109	0.001
Turbidity (NTU)	0.008	−0.014	0.029	0.48
Free Cl (mg/L)
Location: truck
Sample month:				< 0.001
July to October	−0.382	−0.531	−0.233	< 0.001
August to October	−0.062	−0.220	0.095	0.41
September to October	−0.124	−0.266	0.018	0.08
Turbidity (NTU)	−0.420	−0.857	0.017	0.06
Temperature (°C)	0.019	−0.028	0.067	0.42
Location: house
Cistern vs tap	0.052	0.025	0.079	< 0.001
Sample month:				< 0.001
July to October	−0.103	−0.182	−0.023	0.01
August to October	−0.246	−0.321	−0.171	< 0.001
September to October	−0.248	−0.311	−0.184	< 0.001
Turbidity (NTU)	0.011	0.001	0.020	0.03
Turbidity (NTU)
Location: truck
Sample month:				< 0.001
July to October	0.158	0.079	0.236	0.001
August to October	0.007	−0.076	0.089	0.87
September to October	−0.006	−0.080	0.069	0.87
Location: house
Cistern vs tap	−0.256	−0.559	0.047	0.10
Sample month:				0.27
July to October	0.115	−0.562	0.792	0.74
August to October	−0.332	−1.004	0.340	0.33
September to October	−0.365	−0.985	0.255	0.25

CI: confidence interval.x

Table 8. Final multivariable model for factors associated with chlorine concentrations and turbidity.

Risk factor	Difference	95% CI		p
		Lower	Upper
Total Cl (mg/L)
Location: trucks
Sample month:				< 0.001
July to October	−0.319	−0.475	−0.164	0.001
August to October	0.012	−0.150	0.175	0.88
September to October	−0.099	−0.243	0.044	0.16
Location: house
Cistern vs tap	0.008	−0.079	0.094	0.86
Sample month:				< 0.001
July to October	−0.019	−0.168	0.130	0.80
August to October	−0.158	−0.307	−0.008	0.04
September to October	−0.252	−0.395	−0.109	0.001
Free Cl (mg/L)
Location: trucks
Sample month:				< 0.001
July to October	−0.382	−0.531	−0.233	< 0.001
August to October	−0.062	−0.220	0.095	0.41
September to October	−0.124	−0.266	0.018	0.08
Location: house
Sample month:				< 0.001
Sample type:				< 0.001
Type*sample month:				0.03
Cistern vs tap: July	0.009	−0.048	0.066	0.75
Cistern vs tap: August	0.064	0.008	0.121	0.02
Cistern vs tap: September	0.111	0.063	0.160	< 0.001
Cistern vs tap: October	0.012	−0.054	0.077	0.73
Cisterns: July to October	−0.036	−0.128	0.056	0.44
Cisterns: August to October	−0.153	−0.241	−0.065	0.001
Cisterns: September to October	−0.173	−0.248	−0.099	< 0.001
Taps: July to October	−0.034	−0.129	0.062	0.49
Taps: August to October	−0.206	−0.297	−0.114	< 0.001
Taps: September to October	−0.273	−0.353	−0.193	< 0.001
Turbidity (NTU)	0.010	0.001	0.018	0.03
Turbidity (NTU)
Location: trucks
Sample month:				< 0.001
July to October	0.157	0.079	0.236	0.001
August to October	0.001	−0.076	0.089	0.87
September to October	−0.006	−0.080	0.069	0.87
Location: house
Cistern vs tap	−0.244	−0.55	0.062	0.12
Sample month:				0.31
July to October	0.052	−0.630	0.733	0.88
August to October	−0.370	−1.043	0.304	0.28
September to October	−0.383	−1.003	0.237	0.22

CI: confidence interval.

Standard Methods for the Examination of Water and Wastewater. 2005. 21st Edition, Centennial Edition. American Public Health Association, American Water Works Association, Water Environment Federation. ISSN 55-1979. https://www.mwa.co.th/download/file_upload/SMWW_1000-3000.pdf (accessed December 2017).

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