UV - chlorine debate on again

Ruapehu Bulletin, Volume 7, Issue 365, 4 December 1990, Page 3

UV - chlorine debate on again

The Waimarino Community Board is to make its final choice between chlorination and ultra violet treatment of the Ohakune water supply this Thursday.

A report from the technical services directorate recommends the council choose chlorination as the system. This follows their concerns that if the UV system does not work the council would have to eventually install a chlorination system. "If after a period of say two years the UV system proves to be unsatisfactory, gas chlorination will have to be installed and will cost an additional amount of about $72,000 (1990 dollars) including a chlorine contact tank," states the report. "Because of this concern... the management of the council is unable to recommend the installation of the ultra violet system." Other reservations include the age of the reticulation system and the possibility of some bacteria surviving the process. According to the report the cost of the UV system would be $480,660 and the chlorination system $434,360. Running costs for the two options are put at $64,880 for UV and $59,840 for chlorination. The UV running costs include $25,800 for sampling and testing and the report indicates that if the UV system was proved to be operating satisfactorily the testing would be reduced, making UV cheaper to operate. UV guarantee Ohakune's water man Ben Goddard still believes UV is the way to go. He said there should be no concern about the age of the pipes, citing a system which has been installed in a town in Germany with 100 year old pipes. He said as for the concerns over a UV system operating satisfactorily, that one of the UV system suppliers has told him they will guarantee

its success. Mr Goddard is also sceptical of the installation costs quoted in the report, saying the figure of $33,050 for engineering and administration may be too high and the $80,110 for contingencies won't be necessary. Both systems include a filtration system, which is necessary to combat giardia. Neither chlorine nor UV can be guarantied to kill giardia cysts and research has shown that filtration to a fine degree is the best way to combat the bug. Reservoir The report looks at Stage Two of the project which involves relocating the equipment and installing a reservoir on a site with sufficient elevation to gravity feed

the town system. The most economic solution would be a reservoir and treatment plant near the current supply line at sufficient elevation within the Tongariro National Park. The report recommends that negotiations with the Department of Conservation proceed on this option. The report states that strong case could be made on the grounds that: the system would be of low noise; would use timber tanks and buildings of natural colours; would mean less work inside the park by avoiding the pipeline extension via the old bush track and constructing the incoming main adjacent to the Ohakune Mountain Road; that National Park's supply line was allowed inside the park because special care was taken to protect the environment.