Dynamics of the nitrification and sulfide‐driven autotrophic denitrification processes in a single reactor using oxidation–reduction potential as an indicator of the process effectiveness

Abstract

BACKGROUND: This paper evaluates the nitrification and sulfide-driven autotrophic denitrification processes in a structured-bed reactor subjected to recirculation and intermittent aeration (SBRRIA) applied to the post-treatment of an anaerobic effluent. The SBRRIA reactor was operated during 130 days in which influent sulfide concentrations varied between 220.1 and 231.0 mg TDS L −1 (TDS, total dissolved solids). Temporal tests were performed to elucidate the dynamics and sulfide impacts on combined processes. RESULTS: Sulfide partially inhibited the nitrifying activity, resulting in low NH 4+ -N oxidation. This fact affected the overall nitrogen removal performance as total-N removal efficiencies of 50 and 55% were attained in Conditions III and IV, respectively. On the one hand, under continuous aeration and in the absence of sulfide, the oxidation-reduction potential (ORP) reached 50 mV (versus Ag/AgCl) after 250 min of experiment. On the other, when sulfide was continuously provided in the feeding, the ORP was maintained lower than zero. Under anoxic conditions, the effective use of sulfide as an electron donor by autotrophic denitrification was verified by ORP monitoring. However, a concentration of 260 mg TDS L −1 associated with high pH proved inhibitory for NO 3 − reduction.CONCLUSIONS: Based on the results obtained, new strategies of adding sulfide to the SBRRIA should be tested to minimize its inhibitory effect on nitrification and improve nitrogen removal in this unit.

Nitrification in the presence of sulfide and organic matter in a sequencing moving bed biofilm reactor (SMBBR) with zeolite as biomass carrier

“…The presence of biofilm also can help to maintain the AOB and NOB activity in the system with the presence of inhibitors. For instance, dos Santos et al using a biofilm system (structured‐bed reactors subjected to recirculation and intermittent aeration), could keep the nitrifying activity in the presence of total dissolved sulfide (TDS) at concentrations as high as 230 mg S 2− L −1 , and COD concentrations ≈50 mg L −1 . According to Parkin and Speece, attached growth systems are more resistant to sulfide toxicity than suspended ones because of the higher SRT at relatively low HRT and the production of extracellular polymeric substances (EPS), which act as a diffusion barrier between cells and improper environments …”

Pilot-scale study of a structured bed reactor for nitrogen and organic matter removal from sanitary sewage: advances and design challenges

“…Bench-scale investigations have shown the potential of applying the structured bed reactors subjected to recirculation and intermittent aeration (SBRRIA) to remove organic matter and nitrogen compounds from different wastewaters (Almeida et al, 2018;Barana et al, 2013;Correa et al, 2018;Moura et al, 2012Moura et al, , 2018Santos et al, 2016Santos et al, , 2018Silva et al, 2018;Wosiack et al, 2015). In the structured bed reactor, the biofilm grows adhered to a polyurethane (PU) foam that serves as a support material.…”

Modeling of the effect of zeolite concentration on the biological nitrification process in the presence of sulfide and organic matter

“…[5,6] On the other hand, the kinetics of nitrification in the simultaneous presence of sulfide and organic has not been proposed up to date. There are studies which reported the single effect of sulfide on nitrification [7][8][9] and also several studies about nitrification in the presence of organic matter. [10,11] However, the evaluation of a kinetic model involving the simultaneous effects of sulfide and organic matter has not been proposed and has never been reported in the literature.…”