Since their founding in years 1994 and 1995 by the central government of Thailand, many of these small cooperative rubber sheet factories (CRSFs) are still functioning throughout Thailand [1]. One serious problem arising from the treatment of their wastewater is the associated noxious smell of rotten-egg gas (hydrogen sulfide, H2S). Open lagoons or natural oxidation ponds used for this treatment now are standard in these factories [1,2].