LAKE PUPUKE.

Auckland Star, Volume LXV, Issue 13, 16 January 1934, Page 3

LAKE PUPUKE.

" WATER QUITE PURE."

COPPER SULPHATE TREATMENT. BOARD'S SATISFACTION. Complete satisfaction with the results of treating Lake Pupuko with copper sulphate was expressed by members of the North Shore Water Board, who paid a visit of inspection to the hike this morning. The Devonport borough engineer, Mr. A. T. Griffiths, and Mr. H. F. W. Meikle, Mayor, explained the method of treating the lake, and also outlined the working of the filtration plant installed by the Devonport Borough Council.

Messrs. Meikle, chairman of the water board, E. H. JJttle, deputy-Mayor of Devonport, and R. Martin, Mayor of Xorthcote, all members of the board, wore present. They were taken out on to the lake in a launch.

Mr. Meikle said that the object of treating the lake was to rid if of the protozoa which had been defiling the water. In that, the treatment had completely succeeded. The experiment | was begun on January S, and was finished on January 12. On completion tests taken at varying depths from the very bottom, lliiit, to the surface, had revealed 100 per cent of deaths of organisms. Members of tho board who drank water which had been so treated, and had also been through the filtration plant stated that the water was as good as any they had tasted. There was a complete absence of the taste and smell which had constituted tho source of complaint of residents on the North. Shore. Lake Normal in Colour. "We were surprised, rather, to find after we had finished the sulphating that there was no sniell or taste," said Mr. Meikle, "because"we had thought that after the sulphate had killed the organisms, tho smell would be > more intense even than formerly, for a little. However, the organisms seem to have vanished, which is a cause for gratification." Ho added that before the treatment the surface had been a reddish brown in colour, and had smelt badly. To-day he \ pointed out to those who were in the launch that the water was quite normal in colour, and only onco was there even a whiff of the bad sniell. Dr. E. H. Hughes, medical oflficor of health, had visited the lake last week, he said, and had stated that the water was now c^uite ! PU Mr. Meiklv said lie had heard rumours that decaying and putrid matter liad collected round the. lake edge. He ! wished the members to notice that the hike edge was free from such matter, and that nothing there could affect the water Ml the rocks round the edge had boon sprayed with the .solution, as |an added precaution. Altogether, seven tons of copper sulphate had been used, makinjr a solution of 0000 gallons. As the content of the lake was 5043 million gallons, the solution would not harm anyone. Method of Treating. In the cockpit of the launch were a number of large drums, similar to those used for transporting benzine. By mean? of tt feeder pipe projecting out over the lake they were filled with the solution. To all'intents and purposes a hydrographic survey, had boon made of the lake to ensure the accuracy of the treatment. Then, as the launch followed the plan made, the mixture was pumped out in a spray. In all, the launch covered precisely 100 miles. It had been revealed that as the result of the survey the bed of the- lake was parabolic in shape and not cone-shaped. ■Some difficulty had been experienced in taking samples, Mr. Meikle said. At the point of greatest depth, 175 feet, they had fir.«t used an ordinary glass bottle. That had been broken to pieces by the pressure. Thereupon a lead tube with n valve had been used. The filtration plant was also explained by Mr. Griffiths.