[Report of the Medical Officer of Health for London, City of ] page 10

City of London 1970

[Report of the Medical Officer of Health for London, City of ]

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METROPOLITAN WATER BOARD - WATER EXAMINATION DEPARTMENT

AVERAGE RESULTS OF THE CHEMICAL EXAMINATION OF WATER SUPPLIED TO THE CITY OF LONDON FOR 1970. Milligrammes per litre (unless otherwise stated)

Description ot the Sample	Number of Samples Day of the month	Ammoniacal Nitrogen	Albuminoid Nitrogen	Nitrate Nitrogen	Oxygen abs. from KMn04 4 hrs at 2 7° C.	B.O.D. 5 days at 20° C.	Hardness (total) CaC03	Hardness (non-carbonate) CaC03	Magnesium as Mg	Sodium as Na	Potassium as K	Chloride as CI	Phosphate as P04	Silicate as Si02	Sulphate as S04	Natural Fluoride as F	Surface-active material as Manoxol OT		Turbidity units	C olour (Burgess units)	PH value	Electrical Conductivity (micromhos)
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)	(13)	(14)	(15)	(16)	(17)	(18)	(19)	(20)	(21)	(22)	(23)
River Thames — Derived	363	0.026	0.083	4.8	1.02		274	79	5	27.7	5.6	40	2.7	9	70	0.20	0.03		0.1	11	7.9	570
Stoke Newington	52	0.008	0.061	5.2	0.61		305	78	5	30.9	4.9	45	1.9	9	71	0.20	0.02		0.0	8	7.9	620

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BACTERIOLOGICAL RESULTS - YEARLY AVERAGES. 1970.

WATER SUPPLIED TO THE CITY OF LONDON

Source of Supply	BEFORE TREATMENT							AFTER TREATMENT
		Agar plate count per ml.		Col iforrn count		Escherichia coli count		Number of samples	Agar plate count per ml.		Col iform count	E. coli count
	Number of samples	20-24 hours at 37°C.	3 days at 22° C.	Per cent, samples negative in 100 ml.	Count per 1 00 ml.	Per cent, samples negative in 100 ml.	Count per 100 ml.	Number of samples	20-24 hours at 37° C.	3 days at 22° C.	Per cent, samples negative in 100 ml.	Per cent, samples negative in 100 ml.
River Thames — derived	8,259	31.9		37.91	17.3	53.58	4.7	3,710	8.0		99.92	99.97
Stoke Newington	754	39.1		56.76	6.9	75.46	1.7	258	15.3		100.0	100.0