Duangporn Kantachote*, Nastee Kornochalert and Sumate Chaiprapat
A central composite design using two variables (concentrations of isolate P1 and Fermented Pineapple Extract (FPE) each at three levels was used to study their effects on the treatment efficiency of latex rubber sheet wastewater under microaerobic-light conditions. The optimum combination over a 72 h period consisted of 3% P1 and 0.13% FPE and resulted in the removal of 80% Chemical Oxygen Demand (COD), 82% Suspended Solids (SS) and 85% Un-ionized Hydrogen Sulfide: H2S in wastewater (UHS). The selected experimental condition was then verified by varying the retention times. A 96 h retention time gave the highest treatment efficiency with a 92% reduction of COD, 87% SS and 83% UHS and the effluent met both standards for industrial effluent discharge and crop irrigation. This effluent in its undiluted and diluted between 1: 25-1: 200 showed no phytotoxicity and also stimulated rice seed germination based on a germination index when compared with distilled water. Addition of 3% P1 into the raw wastewater either alone or in combination with 0.13% FPE yielded an effluent that passed the standard guidelines within 72 h, while with FPE alone a 96 h retention time was required. Based on morphological, physiological and biochemical properties, the isolate P1 was identified as Rhodopseudomonas palustris.
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