Removal of phosphorus from oyster farm mud sediment using a photosynthetic bacterium, Rhodobacter sphaeroides IL106.

Removal of phosphorous compounds from the mud sediment of an oyster farm was carried out by a series of bio-processes under anaerobic conditions. Anaerobic acidogenic fermentation of a mud sediment suspension (200 g wet wt/l artificial sea water) was initially carried out. With the addition of vitamins such as thiamine, nicotinic acid and biotin, acidogenic fermentation was enhanced to yield acetic acid of approximately 2 g/l. Furthermore, approximately 20 mg/l of PO4(3-) (10% of total phosphorus on mud weight) and 5300 mg/l of COD(Cr) (82% of organic matter on mud weight) were released into the culture broth after fermentation for 7 d. The supernatant of this culture broth was used to cultivate Rhodobacter sphaeroides IL106, a denitrifying photosynthetic bacterium. After 4 d, 3.32 g/l of biomass containing carotenoid and ubiquinone was obtained, and COD(Cr) and acetic acid were reduced by 58% and 72%, respectively. In addition, PO4(3-) was reduced by 97%, suggesting that the removal of PO4(3-) from the mud sediment might be possible by combining anaerobic acidogenic fermentation with R. sphaeroides cultivation.