To degrade organic matters in wastewater generated during the process of fish-meal production (FMW), seven thermophilic microorganisms were newly isolated. In experiments of 100 ml- syringes, the degradation by the screened microorganisms showed more active mineralization of the organic matter under an aerobic condition. Faster biodegradation occurred with more diluted FMW, which resulted in faster removal rates of COD_{Cr} and TN. The best maximum gas production rate and the best maximum cell number during biodegradation were obtained when 8 -folds diluted FMW was used as a substrate. The amino-acid composition in the final broth of the biodegradation in a 51-bioreactor starting with 8 -folds diluted FMW clearly showed that it was almost twice that of non-biodegraded FMW, and the levels of amino acids in the end product of biodegraded FMW were comparable to those in a commercial fertilizer. In phytotoxicity assays for final broth of biodegradation using 32-folds diluted FMW, a strong unpleasant smell noticeably disappeared in the end. According to the GI criterion, the final broth required only 2 -folds dilution to reach the stabilization. The addition of photosynthetic-bacterial culture broth or milk wastewater to FMW was not prominent effect on liquid-fertilization. From all results, reutilization of wastewater generated during the process of fish-meal production was feasible without the environmental problem of an offensive odor and is expected to yield high economic value.
Thermophilic microorganisms
Aerobic biodegradation
Fish-meal wastewater treatment
Fertilizer