Working on water woes

Ruapehu Bulletin, Volume 11, Issue 514, 30 November 1993, Page 2

Working on water woes

• The article in the Bulletin of 23 November 1993 entitled "Ohakune water still on the boil" was not entirely correct. It was correct to the extent that the council had not issued consumers of the Ohakune Water Supply an all clear with regard to boiling water, and the statement that the diatomaceous earth filters were not working was factually correct. However, this is not the reason that an all clear had not been issued as stated in the item. The reason why we had not issued an all clear was because we first wished to

take tests to ensure that all of the untreated water was out of the reticulation system. It will be appreciated that untreated water can take several days to be totally expelled from the system. A bacteriological sample was taken on 25 November 1993 from both the reticulation at Railway Row and the Council Office in Miro Street. Theresults show that the supply at Railway Row is clear of contamination. However, the supply at the Council Office showed a

very low level of contamination. Over the weekend of 27 November 1993 the council chlorinated the supply to speed up the all clear and will issue this as soon as possible. The DE filters have been periodically out of action over the past year and this has been no secret. However the main filters, called depth filters and the ultra violet sterilisation has been

working continuously until the break in the reservoir and pipe work, and every single weekly test from the reticulation had been completely clear of coliform contamination. The DE filters can be regarded as polishing filters which ensure the aesthetic quality of the water and ensure that the water is clear

enough for effective UV sterilisation in the event of very turbid river conditions. If such conditions do occur, and the DE filters are not working, the alarm on the U V unit alerts the operators and as an alternative course of action the backup chlorinator can be brought into operation to sterilise the supply. Turn to Page 4

LETTERS

From Page 2 The DE filters also give added protection against giardia. However, once again this is a polishing action as the majority of the giardia cysts are removed by the depth filters. There is no filtration system in general use in the world that has been shown to remove 1 00 per cent of giardia cysts. However this is not a concern as the concentration of giardia in the water has to reach a certain level before humans are likely to be infected. With only the depth filters working, the level of protection from the giardia would be equal to that of most filtration systems in New Zealand and with the DE filters working as well it would probably be the best. While the problems with the DE filters have been a disappointment and a source of embarrassment, it is pointed out that some teething problems were to be expected with the new plant and the specification

provided for a 12-month maintenance period to ensure that money was withheld from the supplier until all items of plant were shown to be working satisfactorily. The maintenance period has not yet expired for the DE filters. The period of maintenance for the reservoir and the fractured pipework has expired but these items have been repaired by the contractor. The legal position with regard to the financial responsibilities has not yet been resolved.

Cliff

Houston

Chief Executive Editor's Note: We relied upon a council officer's comments for last week's story. Te Kuiti reunion A reunion is planned for people who have worked at the Te Kuiti Hospital, for Queen's Brithday weekend 1994. If this is you enquiriesmay bemadeto 13Colin Brook Place, Te Kuiti or by phoning 07-878-7420

Pauline

Meads