Abstract:
This research investigated the usage of three kinds of bioplastic beads which were Polylactic acid (PLA), Polybutylene succinate (PBS) and Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as organic carbon sources and media in anoxic moving bed bioreactor (anoxic MBBR). The purposes of this research can be divided in to three parts. First was to study the physical characteristics of bioplastic beads. The study suggested that PBS was hydrophilic while PLA and PHBV were hydrophobic. The solubility results showed the level of dissolved organic carbon in tap water and deionized water of PBS was higher than the ones in PHBV and PLA. The Nitrate adsorption of three kinds of bioplastic beads showed that , with pH higher 4, the surface area was a negative charge. It did not appear any nitrate adsorption on the surface area of bioplastic. The second experiment investigated the nitrate removal efficiency with anoxic MBBR batch operation. The result showed that the nitrate removal efficiency of PHBV and PBS were more than 90%, in contrast to PLA of bioplastic at 48% .The kinetics of the denitrification process with PHBV and PHB as organic carbon sources were zero order because the nitrate concentration decreased to 0 mg/L at 12 and 15 hrs. The last experiment was to continue the operation in anoxic MBBR. It indicated that the nitrate removal efficiency of PHBV at steady-state conditions were 12.87±4.92%, 8.11±5.31%, 12.33±8.37%, and 84.83±4.58%, at 12, 16, 20, and 24 hrs., respectively. The denitrification kinetics was the first order as the limitation of organic carbon led to a longer period of denitrification process. While using PBS as an organic carbon source showed that 99.47±0.52%, 99.34±1.83%, 100%, and 98.91±0.95% of the nitrate removals efficiencies at HRT were 12, 8, 4, and 2 hrs., respectively as the organic carbon sources were sufficient to completely denitrification process.