| Title | Biological Hydrogen Sulfide Abatement in Geysers Geothermal Cooling Towers |
|---|---|
| Authors | Sonneville, Allen; Benn, Brian |
| Year | 2010 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Hydrogen sulfide; Secondary abatement; Natural biological abatement; Sulfur oxidizing bateria |
| Abstract | Since the early 1980’s The Geysers cooling tower hydrogen sulfide (H2S) emissions control (secondary abatement) has been implemented by the addition of chelated iron to the circulating water. This chelated iron reacts with the H2S(aq) that has been transported to the cooling tower in the condensate stream. The H2S is converted to non-volatile sulfur compounds. Over the years this process has been improved by finding ways to reduce condensate H2S loading to the tower and by increasing the reaction time for H2S to be oxidized prior to distributing the condensate on the cooling tower deck where “air stripping” occurs as the water falls from the deck to the basin. Another improvement to H2S abatement efficiency has recently been applied at The Geysers, wherein the naturally occurring sulfur oxidizing bacteria existing in the cooling towers are promoted to oxidize H2S in the cooling tower. At The Geysers, cooling tower H2S abatement efficiency was found to unexpectedly improve during the spring months. Coincidentally, air-borne pollen counts in the forested region around the Geysers increase tremendously. Improved H2S abatement efficiency also occurs when tertiary treated waste water (containing phosphate) is added to supplement cooling tower makeup. The addition of tertiary treated waste water has the effect of adding nutrients to a system that typically does not have the full complement of nutrients for sustaining bacteriological growth. The additional nutrients promote natural biological H2S abatement. |