Proceedings of the 7th New Zealand Geothermal Workshop 1985. Alternatives to reinjection in Wairakei. New Zealand Geothermal Workshop [7, 6-8 Nov. 1985, New Zealand].

Rothbaum, H. Peter.

1985

1067
CIENA

0-86869-065-1

The high cost of re-injection of geothermal discharge waters is largely due to their silica deposition potential. One should ask if reinjection of Wairakei discharge waters is really necessary to solve any environmental problems due to arsenic, boron, lithium, mercury or waste heat. Alternative strategies are: Doing nothing, and continuing discharging the geothermal waters from Wairakei into the Waikato River; Chemical treatment to remove arsenic together with prevention of silica scaling and removal of waste heat. A successful pilot plant will be described which achieves these aims by a method particularly suitable to Wairakei waters. Alas-boron and lithium remain; A more controversial suggestion involves chemical treatment of Warakei waters as in n. 2, which might then allow direct discharge from a second geothermal station into the Waikato River without exceeding the WHO (World Helth Authority) arsenic limit for drinking water. The economics and our present state of knowledge of the environmental consequences of these options will be discussed. It is believed that present or projected levels of boron and lithium in the Waikato are unlikely to cause any harmful effects, however, more work is required to allow the public to be convinced of this. Nearly all of the mercury evolved is in the geothermal steam, and therefore neither treatment nor reinjection of discharge waters will have any effect on the mercury level of the Waikato River. In other geothermal stations (e.g. Ohaaki and Mokai) partial removal of silica, by a method being tested on pilot plants by Industrial Processing Division and Chemistry Division, would allow reinjection to be carried out at lower temperatures. ABSTRACT. INTRODUCTION. ARSENIC REMOVAL AND SILICA STABILISATION. BORON AND LITHIUM. PARTIAL REMOVAL OF SILICA. ALTERNATIVE STRATEGIES TO REINJECTION. Doing nothing. Removal of arsenic with prevention of silica. Removal of arsenic from Wairakei waters and direct discharge of Ohaaki or Mokai waters into the Waikato river. RECOMMENDATIONS. ACKNOWLEDGEMENTS. REFERENCES.

Presenta ilus.

NUEVA ZELANDIA; ENERGIA GEOTERMICA; GEOTERMIA; REINYECCION; COSTOS; IMPACTO AMBIENTAL; AGUAS RESIDUALES; CONTAMINACION DE RIOS;