Formation and characteristics of microbial granules containing photosynthetic bacteria using palm oil mill effluent (POME)

Abstract

The aim of this study was to investigate the possibility of applying bacterial photosynthesis using granulation technology method in minimizing carbon dioxide (CO2) gas emitted within a treatment system. By using a sequencing batch reactor (SBR) system with palm oil mill effluent (POME) as feeding, the photosynthetic microbial granules were developed after 100 days at an organic loading rate (OLR) of 1.53 kg COD/m3. day and hydraulic retention time (HRT) of 8 hours (cycle time = 4 h). In terms of the morphological structure, the sludge evolved from dispersed loose shaped into a more stable and smoother compact granular form with good settling properties. The sludge settleability also improved from 0.50 to 2.88 cm/s periodically due to the increased of biomass concentrations (6.90 - 8.25 g/L) with a maximum granule size of 3.2 mm obtained. Other than that, the physical characteristics of the granules displayed great strength and stability as they attained low integrity coefficient at 2.22%. Based on the pigment analysis result using the UV-Vis spectrophotometer, the bacteriochlorophyll and carotenoids were found to correspond to that of purple non sulphur bacteria within the ranges of 801nm to 865nm (the existence of bacteriochlorophyll b) and 400nm to 500nm respectively.