The real-time monitoring system strategy for stable long-term operation of pilot-scale single-stage deammonification (SSD) process treating moderate-strength NH4+

Single-stage deammonification (SSD) processes have been successfully operated to treat high-strength NH4+-N, but often fail to treat moderate-strength NH4+-N (100-300 mg/L). Moderate-strength NH4+-N causes deterioration of process efficiency to occur NO2--N oxidizing bacteria (NOB) due to free ammonia (FA) reduction and maintenance limits. The optimal FA (> 0.1 mg/L) control focusing on real-time monitoring pH and NH4+-N under controlling low DO was integrated to enhance the SSD process stability operational treating moderate-strength NH4+-N wastewater. The average NRE and NRR were still high as 82 & PLUSMN; 1% and 0.22 & PLUSMN; 0.01 kg/m3/d. A real-time monitoring system strategy that directly uses DO, NH4+-N and pH was effective in stably providing optimal DO (< 0.1 mg/L) and sufficient FA (> 0.1 mg/L) that capable in inhibiting selective NOB activity. Microbial community characterization revealed that denitrifying bacteria indicate their important role in the improved nitrogen removal performance using in organic matter of reject-water without another anoxic period under longterm low DO with optimal FA conditions. The research results are expected to prevent the problem of unstable due to the substrate competition of major microorganisms and to reduce the deterioration within the SSD process due to excessive NOB activity.