[Report of the Medical Officer of Health for Enfield] page 84

Enfield 1971

[Report of the Medical Officer of Health for Enfield]

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ENVIRONMENTAL HEALTH

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Table 41 Water supplyMetropolitan Water Board Average Bacteriological Results

	Results before Treatment
	Thames Derived	New River Derived	Hoe Lane Well Derived	Hadley Road Well Derived	Waltham Abbey Well Derived
Number of Samples	8,154	1,504	249	250	251
Agar Plate Count per ml. 20-24 hrs. at 37°C	53.9	82.8	0.1	0.4	0.2
3 days at 22°C	-	-	14	64	9
Coliform Count Percentage of samples neg. in 100 ml.	40.37	40.69	100.0	84.00	99.20
Count per 100 ml.	12.2	14.2	-	3.1	0.1
Escherichia coli Count Percentage of samples neg. in 100 ml.	54.91	60.31	100.0	86.00	100.0
Count per 100 ml.	5.1	2.5	-	2.2	-
	Results after Treatment
Number of Samples	3,901	515	253	249	254
Agar Plate Count per ml. 20-24 hrs. at 37°C	8.4	14.7	0.1	0.1	0.8
3 days at 22°C	-	-	8	11	17
Coliform Count Percentage of samples neg. in 100 ml.	99.51	100.0	100.0	100.0	99.61
Escherichia coli Count Percentage of samples neg. in 100 ml.	99.97	100.0	100.0	100.0	100.0

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Table 42 Water SupplyLee Valley Water Company Representative Sample

Chemical Results Expressed in Milligrammes per Litre
Appearance	Clear and Bright		Ammoniacal Nitrogen			0.02
Colour (Burgess)	Less than 5		Albuminoid Nitrogen			0.00
Odour/Taste	Nil/Nil		Nitrate Nitrogen			8.0
Turbidity	0		Nitrite Nitrogen			0.00
Conductivity	600		Oxygen Absorbed			0.30
Total Solids	445		Fluoride less than			0.2
pH	7.2		Silica			15
Free CO₂	30		Iron less than			0.02
Alkalinity (CaCo₃)	210		Other metals: Copper/Zinc/Lead			absent
Carbonate Hardness	210		Phosphate			0.11
Non-Carbonate Hardness	120		Residual Chlorine			Nil
Total Hardness	330		Temperature (°C)			8.5
Bacteriological Examination
No. of Colonies developing on Agar		1 day at 37°C		2 days at 37°C	3 days at 20°C
No. of Colonies developing on Agar		0 per ml.		1 per ml.	4 per ml.
		Present in		Absent from	Probable No.
Presumptive Coli-Aerogenes..		— ml.		100 ml.	0 per 100 ml.
E. Coli		— ml.		100 ml.	0 per 100 ml.
CI. Welchii		— ml.		— ml.