Abstract

Within two years in operation, a pilot-scale High Rate Algal Pond (HRAP) of 5 m3/day flow rate showed its ability in eliminating the evaporation of hydrrogen sulphide during its treatment of anaerobically treated natural rubber processing waste water. Chlorella sp. was the alga used in the HRAP. The waste water was having a dissolved sulphide concentration of about 5.00 mg/L. At the centre of this HRAP, about 55% dissolved sulphide still remained, but the concentration of hydrogen sulphide in the air above the HRAP was less than 1 ppm. The dissociation of hydrogen sulphide in the basic medium caused by photosynthesis by Chlorella sp. in the HRAP was believed to have suppressed the emission of gaseous hydrogen sulphide during the treatment.