Photosynthetic microbial granules developed from palm oil mill effluent (POME)

Abstract

In the 1980s, carbon dioxide (CO2) gas was proven to be one of the most hazardous greenhouse gases (GHG) as it increases from 57 to 80% of the current GHG contribution to global warming. In Malaysia, one of the major sources of GHG is from industrial wastewater treatment such as the ponding system to treat palm oil mill effluent (POME). Alternatively, this study looks into the possibility of applying biogranulation technology by growing photosynthetic bacteria to consume CO2 gas within a treatment system. The photosynthetic microbial granule was cultivated for 100 days in a sequencing batch reactor (SBR) system by applying an organic loading rate (OLR) of 1.53 kg COD/m3. day, hydraulic retention time (HRT) at 8 hours and superficial air velocity of 0.58 cm/s. The results showed the morphological structure of sludge evolved from dispersed loose shaped into a more stable and smoother compact granular form with good settling properties. The settleability of the sludge improved from 18.0 to 103 m/h periodically due to the increased of biomass concentrations (6.90 - 8.25 g/L) as well as achieving maximum granule size of 2.8 mm. The granules also displayed great physical characteristics in strength and stability, which attained low integrity coefficient (2.22%). Based on the pigment analysis using the UV-Vis spectrophotometer (380-1100 nm), the presence of purple non-sulfur photosynthetic bacteria were detected in the sludge. The average wavelength adsorption obtained was within 976 to 1050 nm which implied the existence of bacteriochlorophyll.