WATER FILTRATION.

Stratford Evening Post, Volume XXXII, Issue 97, 24 April 1912, Page 2

WATER FILTRATION.

MR. CLIQUE’S REPORT. Folio wing is a copy of Mr Climic’s report on water filtration presented to the lioroiiish Council in 1910 ; Tlu> Source of your supply is liable to contamination before reaching the intake, by (a) the drainage from swampy land, which gives the water a mossy and peaty taste; (b) by draining from land now lining brought under cultivation ; (c) by silt held in suspension during Hoods. When the scheme of water supply was originally installed provision war made to overcome this contamination by filtering the water through the shingle-bed of the river. For 11}is purpose a tunnel was driven along the bank and below the level of the bed of the river on the upstream side of the road bridge. From this tunnel numerous earthenware pipes were laid under the bed of the river at a depth of from three to four feet. For a con-

siderable time this filter answered admirably as regards clearing the watei from all suspended matter, but it did not free the water from the mossy or peaty taste, especially during the summer months. As the consumption

of the water increased and these filter pipes became silted up, tiie water was drawn directly off the river through a valve that was supposed to he used only in emergency. Through drawing the water directh off the river in this manner without Hit-ration of any kind, dead leaves and other vegetable matter lodged in the main intake, tunnel, thus giving rise to an unpleasant taste and odour. This is overcome to a great extent by scouring out the tunnel occasionally, which scouring out was attended to until the last rear or two.

After each scouring out there was a decided improvement in the quality of the water, and f am of opinion that the plan proposed hy your foreman to drive a small tunnel from the river with necessary catch-pit, sluice valve, etc., to facilitate this work, will he well worth the expense.

Jf tin’s tunnel was scoured out say every three months, the improvement in the quality of the water would ho very noticeable; and this periodical scouring would bo a grout saving in the labour required to cleanse the filtering medium of a filter should one he installed.

in regard to the question of filter-ing-the water, I am of opinion that the time has arrived when this should be carried out in view of the fact that this treatment would free the water of all unpleasantness and would ensure its perfect wholcsomeness, though ) am given to understand that the analysis made hy Dr. Makgill some short time since did not reveal anything seriously wrong with the water, that is anything injurious to health.

The first consideration is the question of the quantity of water required daily. For purely domestic and sanitary purposes this is not difficult to arrive at, as it is usual to allow a definite quantity per head per day, which is generally an allowance of CO gallons. This for a population of say 3000 means 180,000 gallons in the 21 hours; hut as the maximum demand for a few hours during the day is two and one half times the average, the capacity of the filter must ho large enough to meet that demand, or n reservoir must he provided. Estimating from the reading of the pressure gauge in your town, the quantity of water drawn off at maximum demand at the present time is nearly twice as much as the maximum domestic demand for 3000 consumers; therefore I conclude that this extra quantity is used hy the water motors. I might here remark that this quantity is about 10,000 gallons per hour more than is being paid for by the users of the water motors; in other words, the Council is losing Is 3d per hour on the water supplied to those motors, which in a very short time would pay for the installation of a water meter.

Tho next f|ncstion is tlie class of filter that should ho installed. After going thoroughly into the matter ! am of opinion that the cheapest, hoth in first cost and the cost of maintenance, is a mechanical pressure filter installed on the main, without a reservoir; and the site for the filter is at the junction of Page Street and I}recon Hoad, say in the corner of the domain. The filters require very” little space, as they are only eight feet

iii diameter iuui about fifteen feet in height. They also do not require housing, ;1 'id arc not at all unsijj;litly. The site proposed is very accessible and most .suitable in every way. The filter mini res very little attention, which can he given hy one of the borough men, and will take only, say, half an hour on alternate days.

1 have considered the question of installing a sand and shingle filter of a I’nech-Chahal type; this filter is largely used on the Continent for the filtration of very polluted river water. This filter would require a small reservoir, and would have to he placed at the head of the pipe-line on Mr -Viareliant’s property. As the cost of construction and also the maintenance of it is very much more than that of the initial cost and maintenance of the mechanical filter, and the superiority of this class of filter I temp; doubtful, I have no hesitation in recommending the mechanical pressure filter of such a capacity as to meet tin 1 maximum demand both for motors and for purely domestic supply. The amount earned by your Council from the sale of water for the motors is far more than the interest on the cost of the extra filter. As before mentioned, these filters wil he directly on the main; therefore, to provide for an extraordinary demand for water, such as in the ease of a conflagration breaking out, the valve on the by-pass can he opened; if considered advisable, this valve can work automatically. In regard to the cost of the in-

stallation of a filtration system, the following js my estimate:— No. I method,—Mechanical pressure filter, each Bft. diameter, landed in Wellington duty (20 per cent) and charges paid, £521); w-naHuge and railage to Stratford, say £l4; necessary valves, fittings, etc., £lll ; cost of erection of filter, £57 ; total cost of one filter, £O-41 ; total cost of two filters, which are required to deliver 30,000 gallons per hour, £1262. No. 2 method.—Sand and shingle filter, including excavating site, supplying and grading filtering medium, necessary valves, by-passes, etc., £1100; concrete storage reservoir to hold million gallons, including necessary valves, connections, etc., to existing mains, overflow, etc., £787; total cost, £IBB7.

No allowance has been made for obtaining from Mr Marchant the freehold of the land (at least one acre) required in No. 2 method.

The estimate for the mechanical pressure filter is only approximate, as the quotation 1 have based my estimate on is about three years old. Since receiving your instructions there has not been sufficient time to obtain fresh quotations.

The cost of attention and maintenance of these two types of filters, gained from experience of larger installations, is as below:— No. 1 method (mechanical filter).— From 2s to 3s per million gallons filtered.

No 2 method (Tuech-Chabal filter) _From IDs to 12s per million gallon: filtered.

Trusting that the foregoing information will meet the requirements of your Council, and that in tlie event of your Council deciding to adopt a thoroughly efficient filtration' system such as outlined above, 1 shall be favoured with instructions to prepare detail plans, -specifications, etc., for the carrying out of the work. If any further information is desired I shall he happy to wait upon von and discuss the matter.