PHYSICOCHEMICAL CHARACTERISTICS AND LEACHABILITY OF SCALE AND SLUDGE FROM BULALO GEOTHERMAL SYSTEM, PHILIPPINES

Scale and sludge from Bulalo geothermal field, Philippines. have been characterized by whole rock analysis, radioactivity counting, size ana lysis, light microscopy, scanning electron microscopy, and X-ray diffr action. Their leachability was assessed by regulatory leaching procedu res and by sequential extraction. Both scale and sludge consisted most ly Of oxides of Si, Al, and Fe with no radionuclides detected. The sca le had 10% S content. Sulfides and silicates were important phases in both samples having size ranges from submicron to 2 mm. Geothermal soi ls at Bulalo have higher than normal soil levels of As, S, Cu, Cr, Zn, and Pb but regulatory leaching tests indicated that these elements ar e not released. However, the sequential extraction showed that As, Cu, and Zn were leachable under extreme conditions.