Improvement of biofilm activities in sequencing batch reactor via polyvinyl alcohol (PVA) granules addition

Polyvinyl alcohol (PVA) (C2H4O)n is a synthetic polymer material commercially available on an industrial scale. In this study, two formulas were tested for preparing biofilm carriers in spherical shape from PVA/H3BO3 (formula 1) and PVA/NaNO3 (formula 2) crosslink bonds without activated sludge entrapment. Formula 2 gave better results with white, round, gel-textured, flexible, and firm carriers. The PVA/NaNO3 granules continued to be used as moving-bed biofilm carriers at a ratio of 10% of the working volume to evaluate the wastewater treatment capacity in the sequencing batch reactor (SBR). After five weeks of operation, the results showed that the PVA/NaNO3 granules turned light yellow due to the presence and development of aerobic biomass. The surface of PVA/NaNO3 granules was plump, elastic, not cracked, and settled well. The amount of biomass attached to the PVA/NaNO3 granules was 0.4 gTSS/g granules. The hydraulic settling velocity of the PVA/NaNO3 granules was 56 mm/s. The wastewater treatment efficiency of the SBR system using moving-bed biofilm activity developed on the PVA/NaNO3 granular carriers was evaluated according to the TSS, COD, and NH4+– N parameters at 88%, 90%, and 92%, respectively. The experimental results have demonstrated the potential of developing a new type of biofilm carriers from PVA polymer materials that offer good settling ability and resistance to hydraulic shear force during aeration. Therefore, PVA granules can be easily applied in the column SBR configuration.