Nitrogen and carbon removal efficiency of a polyvinyl alcohol gel based moving bed biofilm reactor system

In this study, the effectiveness of polyvinyl alcohol (PVA) gel beads in treating domestic wastewater was investigated: a moving bed biofilm reactor (MBBR) configuration (oxic-anoxic and oxic) with 10% filling fraction of biomass carriers was operated in a continuously fed regime at temperatures of 25, 20, 15 and 6 °C with hydraulic retention times (HRTs) of 32 h, 18 h, 12 h and 9 h, respectively. Influent loadings were in the range of 0.22–1.22 kg N m⁻³ d⁻¹ (total nitrogen (TN)), 1.48–7.82 kg chemical oxygen demand (COD) m⁻³ d⁻¹ (organic) and 0.12–0.89 kg NH₄⁺-N m⁻³d⁻¹ (ammonia nitrogen). MBBR performance resulted in the maximum TN removal rate of 1.22 kg N m⁻³ d⁻¹ when the temperature and HRT were 6 °C and 9 h, respectively. The carbon removal rate at this temperature and HRT was 6.82 kg COD m⁻³ d⁻¹. Ammonium removal rates ranged from 0.13 to 0.75 kg NH₄⁺-N m⁻³ d⁻¹ during the study. Total phosphorus and suspended solid removal efficiency ranged from 84 to 98% and 85 to 94% at an influent concentration of 3.3–7.1 mg/L and 74–356 mg/L, respectively. The sludge wasted from the MBBR exhibited light weight features characterized by sludge volume index value of 185 mL/g. Experimental data obtained can be useful in further developing the concept of PVA gel based wastewater treatment systems.