ABSTRACT
Partial sulfide autotrophic denitrification (PSAD) has been proposed as a promising process to achieve elemental sulfur recovery and nitrite accumulation, which is required for anaerobic ammonium oxidation reaction. This study investigated the effect of seeding sludge on the start-up performance of PSAD process, with different sludge taken from the oxidation zone (S-o) of wastewater treatment plants, partial denitrification reactor (S-PD), and anoxic/oxic reactor (S-A/O). The results showed that the PSAD process could be achieved rapidly in three systems on day 22, 29 and 26, respectively. In particular, the S-O system completed the start-up in the shortest time of 22 d, with NO3--N and S2- removal efficiency of 85.3% and 99.3%, respectively. Selected the S-O system to operate long term, the nitrite (NO2--N) and biological elemental sulfur (S0) accumulation efficiencies were systematically investigated under different S/N ratios (in a range of 0.71-1.2). The maximum NO2--N and S0 accumulation efficiencies were 85.2% and 73.5%, respectively, at the S/N ratio of 1.1. In addition, the separation and recovery of S0 in effluent was achieved by employing polyaluminum chloride (PAC) as a flocculant. Using 2D Gaussian function as quadratic model for the maximizing of S0 flocculant efficiency (SFR), an optimal condition of PAC dosage 7.92 mL/L and pH 5.14 was obtained, and the SFR reached 94.1%, under such conditions. The findings offered useful information to facilitate the application of the PSAD process.
