Sulfur autotrophic denitrification (SAD) driven by homogeneous composite particles containing CaCO3-type kitchen waste for groundwater remediation

This study first developed homogeneous sulfur/buffer composite particles to obtain an alkalinity-uniform and cost-effective sulfur autotrophic denitrification (SAD) technology. As single solid-phase material, the composites performed better in enrichment of microorganisms and stabilization of S/C ratio throughout the reaction. Natural CaCO3-type kitchen waste, used as a buffer in the developed composites, was conducive to providing rich metal nutrients (K, Na, Mg, Al, and Ca) for the metabolism of microorganisms. Maximum denitrification efficiency of 96.4%, 96.8% and 96.8% were obtained by the 1.25:1 PSL, 1.72:1 PSE and 1.25:1 PSS composites, respectively, and nitrate removal rates of >0.6 mg-N/L-h and stable pH between 6.20 and 8.00 were achieved. The S0-eggshell microcosms showed more significant accumulations of ammonium-N and sulfate, reaching ∼1.2 mg-N/L and 405.99 ± 9.47 mg/L, respectively. When dealing with nitrate in real groundwater, the composites showed a great advantage over the dispersed materials at a denitrification efficiency of more than 99.7% and rate of 0.40 mg-N/L-h. No ammonium was observed by PSE and PSS throughout the batch. This study confirmed the potential of waste composites to enhance SAD performance in nitrate-contaminated groundwater remediation.