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66
grain instead of two grains. In another case an emulsion of cod-liver oil and
hypophosphites contained an artifical dye which should not have been present.
Several calamine samples were rejected as containing large quantities of calcium
and magnesium carbonates.
Fertilisers
and feeding
stuffs.
in connection with the provisions of the Fertilisers and Feeding Stuns Act,
1926, 255 samples have been examined during the year under the supervision of
the chemist, who is the official agricultural analyst for those parts of the county
which do not come within the purview of the City Corporation or Port Sanitary
Authority. The results of the analyses were :
Samples of feeding stuffs.
Complied with guarantee 102
Deficient 26
Constituents in excess of guarantee 36
Guarantee incorrect in form or no guarantee 12
Contained deleterious substances 22
Total 198
Samples of fertilisers.
Complied with guarantee 22
Deficient 4
Constituents in excess of guarantee 25
Guarantee incorrect in form or no guarantee 6
Total 57
Included in the number of samples of feeding stuffs containing deleterious
substances were 17 taken from different bags of one consignment of linseed cake,
composite samples of which had previously been found to contain castor seed.
Examination proved this harmful constituent to be present in all the bags of cake,
though the distribution, as was to be expected, was shown to be very uneven, fully
justifying the contention that in any case in which even an extremely small amount
of castor seed is found, the whole batch should be considered unfit for use as a feeding
stuff. A sample of ground nut cake was reported against as containing an excessive
amount of sand and silicious matter, which consisted largely of coarse sharp particles
some of which were identified as being glass. The need for continued inspection
and examination under the powers of the Act is clearly exemplified by the results
of the past year.
Drinking
water
supply.
A regular chemical and bacteriological examination has been made ot the drinking
water at those institutions of the Council which derive their supplies from private
wells, and water from other sources has been tested when required. During the
year 200 samples have been examined chemically and 387 bacteriologically from
38 institutions, in 10 of which chlorinating plants are in operation. In six cases
a thorough cleaning of the tanks was recommended and after this treatment the
quality of the water again became satisfactory.
Outfalls.
The long continued dry weather led to a strong septic sewage, which it was
difficult to treat satisfactorily by sedimentation, being received at the outfalls.
Although chemical treatment was begun earlier in the year than usual and
continued for a longer period, the inadequacy of sedimentation alone to produce
an effluent suitable for discharge into a river of greatly reduced flow was apparent.
At the northern outfall about 10 million gallons daily were treated in the activated
sludge plant with continued success, and the construction of five similar units will
improve greatly the character of the total effluent discharged from this outfall.
Much experimental work has been done in the hope of reaching more satisfactory
additional chemical treatment in periods of very low river flow than has
hitherto been used and found sufficient in ordinary summers.
The dry matter in individual cargoes of sludge sent to sea from the northern
outfall varied from 4 per cent, to 17 per cent., the average being 8.4 per cent., rather
less than last year. At the southern outfall the average dry matter was 7.1 per
cent., with variations from 3 per cent, to 13 per cent. In both cases the dry matter
in the greater number of cargoes did not diverge greatly from the average.