[Report of the Medical Officer of Health for Chigwell] page 24

Chigwell 1969

[Report of the Medical Officer of Health for Chigwell]

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	Lee Bridge	Copper-mills	Chingford Mill	Ferry Lane	Waltham Abbey
Surface-active material as Manoxol OT	0.03	0.03	-	-	-
Turbidity units	0.1	0.1	0.1	0.1	0.4
Colour (Burgess units)	12	10	6	2	7
pH value	8.1	8c2	7.5	7.7	7.5
Electrical Conductivity (micromhos)	660	650	530	850	550
(b) Results of Bacteriological Examination:-
BEFORE TREATMENT-
No. of samples	2,675	308	250	77	249
Agar plate count per ml,:-
20-24 hours at 37°C	203.5	130.8	0.4	0.3	0.1
3 days at 22°C	-	-	8	-	9
Coliform count:-
Per cent, samples negative in 100 ml	40.67	45.13	100.0	98.70	99.60
Count per 100 ml	9.3	14.7	-	-	-
Escherichia coli count:-
Per cent samples negative in 100 ml	60.34	68.51	100.0	100.0	100.0
Count per 100 ml	2.3	1.6	-	-	-
AFTER TREATMENT -
No. of samples	495	127	250	*79	253
Agar plate count pgr ml.:-
20-24 hours at 37°C	52.0	43.5	0.3	7.1	0.2
3 days at 22°C	-	-	4	-	6
Coliform count:-
Per cent, samples negative in 100 ml	99.60	100.0	100.0	100.0	99.60
E. c oil count:-
Per cent. samples negative in 100 ml	99.80	100.0	100.0	l00.0	100.0
* Mixed with filtered River Lee - derived water before chlorination." /2.