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(A) Chemical Examination in parts per million
Total solid residue (dried at 180°C.) 190
Chlorine present as chloride 18.3
Ammonia, free 0.06
Ammonia, Albuminoid 0.00
Nitrate nitrogen 9.9
Nitrite nitrogen 0.05
Oxygen absorbed from (a) in 4 hours 0.14
permanganate solution (b) in 15 mins. —
Hardness, as CaC03—Temporary 72
Permanent 50
Total 122
Alkalinity, as CaC03 72
Free carbon dioxide, as C02 —
Iron absent
Other metals absent
Residual chlorine 0.08
Electric Conductivity at 20 °C. 275 units
pH 7.8
(c) Bacteriological Examination
Number of colonies developing per millilitre of water:—
on agar in 2 days at 37°C. 0
on agar in 3 days at 22 °C. 0
Bacteria of indication enumeration :—
Organisms of the coliform group 0 per 100 ml.
Streptococci 0 do.
CI. welchii 0 do.
Remarks
This water is of good organic purity and moderate hardness and salinity.
The chemical composition is similar to that of part of the Sutton and District
Water Company's supply and corresponds to a partly softened deep well water
from the chalk. There is a slight sediment of calcium carbonate which rapidly
settles and leaves a clear and attractive water. The residual chlorine present
indicates continuing precautionary treatment.
The bacteriological condition of the sample is excellent.
As judged by these samples the water is wholesome and suitable for the
public supply.
The average hardness of the samples taken by the local authorities was
8.8° compared with 9.18° in the year before. Four exceeded 9° of hardness
and seven were below.
Drainage and Sewerage
Under an arrangement made with the Croydon Corporation sewage is
pumped to the disposal works of that authority in Beddington, except at a
few points on the fringes of the district, where it is more conveniently
drained to the sewerage systems of neighbouring authorities.
Surface drainage in the south is mainly by soakaways in the chalk;
elsewhere it is by surface sewers to the River Wandle.
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