THE WATER WE DRINK.

Evening Star, Issue 3477, 15 April 1874, Page 3

THE WATER WE DRINK.

The following report and analysis of the Water Company’s water, made by Professor Black, has been forwarded to the City Council, and will be read at the meeting of that body this evening In accordance with your instructions to pie, dated 6th inst,, I have the honor to report on the quality of the Dunedin Water Company’s water. Three of the samples examined, marked A, B, C, in the subjoined table, weie delivered at the laboratory by one of your officers. The sample marked D, I collected at the laboratory tap here. As my report to you, dated 30th June of last year, exhibits the resuta of a careful and exhaustive analysis of the water supplied to Dunedin at that time, 1 have not considered it necessary to do more at present than determine the proportion of total solid residue left on evaporation, and the proportion of organic matter in the several samples. The table subjoined shows the results I obtained under these two headings on the 9th of the present month, also the results obtained on the 25th of June of last year ; and for comparison I have transferred from Watt’s dictionary of chemistry corresponding results similarly obtained from river and lake Waters supplied to London and other communities in various parts of Europe.' It will he seen from these results that the water taken from the Corporation Office’s tap last week contains 36 per cent, more organic matter than water taken from the same tap in last June, i hia increase of organic matter is probably to be accounted for by the circumstance that the present analysis was made at an earlier period of tha year, before the cold weather has set in. and before the heavy rains of winter have swept away the loose vegetable growths. Under the microscope ( sachet’s 400 dram) the water taken from the Corporation and laboratory taps does not show organisms in greater variety nor in much greater proportion than I observed in June last. The sample submitted from the upper reservoir, however, shows low cellular growth—confervas, desmids, diatoms, &c m such abundance as to render that water, In its present condition, in my opinion, quite pnfit for domestic use. In view of these results, showing so large an increase of organic matter, the water will not quite maintain the good character I was able to give it in my last report. Though still within the limits of water extensively used for do mestie purposes, it is, I. think, desirable that sojnething were done to improve its quality. A great improvement could be easily effected by causing the water to undergo, before entering the main, a process pf filtration either through a bed of sand or gravel, or these mixed with clay or powdered charcoal. By this means th- suspended impurities—vegetable growth, particles of clay, and the debris of plants—would be removed; and if charcoal were * used the dissolved organic impurities also to some extent. If, in addition to some such process of filtration, the water were caused to flow for a few miles in the open air over a sandy oi pebbly channel, so as to he expos d to the action of light and the oxidizing influence of the atmosphere, it would rank for domestic purposes among the best waters supplied to any community. Total Solid Residue akd Organic Hatter in Grains per Gallon. total SOURCE. solid orgakic RESIDUE. MATTER -

April 9,1874. A—Dunedin small upper Reservoir 8-7 4-06 B—Dunedin large lower Reservoir 618 2-10 C —Dunedin Corporation Offices 6-37 190 D—Dunedin TJniv. Lab. tap 6-30 1-92 Thames at Kew, Gr. Junct. Company 21*7 3-07 Thames at Barnes, "West Middlesex Company 22-67 2-75 Do. at Battersea, Southwark fcnd Vauxhall Company... 21-07 1-49 Do. at Chelsea, Chelsea Corapany Do. at Lambeth, Lambeth 21-08 2-38 Company 20-39 2-59 Do. at London Bridge 28-58 7-00 Do. at Greenwich 27-98 4-07 Ravensbourne, Kent. Kent Co., 1851 29-7 2 61 Mew River, New River Co. 19-4 275 River Lea, E. London Co. 23-5 4.13 Loch Katrine, Glasgow supClyJe, few miles above Glasgow 1.98 0-79 813 1-12 Lake of Geneva 10-64 0-42 Rhone at Lvons 11-86 0-23 Manchester Water Supply. 1864 5-35 0-7H Dunedin — R6ss?a Creek, above Reservoir (Juno 1863) Dunedin—Small upper Re-6-9 1-36 ’ Her voir (Juno 25.1863) ... 714 1-33 Dunedin—Large lower Reservoir (June 25, 1863) ... 670 1-25 Dunedin — Com. Offices (June 25, 1863) Dunedin—Tap at Salutation 6-11 1-40 Hotel (1863) Dunedin—Last House In St 6.60 1-42 Andrewstreet (June, 1862) 6-80 1-28