Simultaneous nitrification and denitrification in the activated sludge systems of continuous flow

Abstract

This study has investigated the biological nitrogen removal by simultaneous nitrification and denitrification (SND) processes in a system of continuous flow activated sludge (AS) process. The investigation had four stages and evaluated the system behavior under different solid retention times (SRT), food-to-mass (F/M) ratios and dissolved oxygen (DO) concentrations. The data showed that the concentration of DO 0.5±0.2 mgO/L did not affect the growth of heterotrophic bacteria (2.2-3.1 d at 20°C) and autotrophic nitrifying bacteria (0.16-1.94 d at 20°C), resulting in values very close to those obtained in conventional AS processes. The chemical oxygen demand (COD) removal was over 90% in all stages. The decrease in SRT from 37.2 to 27.8, 19.0 and 10.0 days had no significant influence on the development of SND. In the stage where the carbon/nitrogen (C/N) ratio was 4.3 mgCOD/mgN L, SND efficiency was of 55%. In the following stages, the C/N ratio was increased and it was possible to achieve efficiencies higher than 98% SND. Overall, the data showed that appropriate controls of carbon and nitrogen input are required to achieve an efficient SND. An established SND technology can save operation time and energy, and might replace the traditional two stages: biological nitrification and denitrification process.

Nutrient metabolism, mass balance, and microbial structure community in a novel denitrifying phosphorus removal system based on the utilizing rules of acetate and propionate

“…3B) and promoted the deep-level nutrient removal. Even so, MSND,N function was indistinctive and much lower than other aerobic sludge systems (Bueno et al, 2018;He et al, 2017a) for the following reasons. Firstly, it cannot satisfy the energy requirement owing to the limited carbon residual proved by MMBBR,C in the MBBR (Seifi & Fazaelipoor, 2012).…”

Effect of Amoxicillin on Nitrogen Oxidation Bacteria Present in Activated Sludge: Respirometry Investigation

“…To determine the half-saturation constant (K n ), Monod kinetics was limited. Through the analysis of respirograms, when µ = ½ µ max or OUR n = ½ OUR n.max , the ratio between the area equivalent to the concentration of the residual substrate (ammonia or nitrite) was calculated by the respective stoichiometric oxygen coefficient − 4.57 for NH 4 + -N and 1.14 for NO 2 − -N [26].…”

Role of heterotrophic nitrifiers and aerobic denitrifiers in simultaneous nitrification and denitrification process: a nonconventional nitrogen removal pathway in wastewater treatment

“…In the SND process, nitrification and denitrification reactions take place concurrently in a single reactor for which three mechanisms have been proposed: (i) physical mechanism (micro‐environmental theory), (ii) mechanisms based on environmental and operational control (macro‐environmental theory), and (iii) biological mechanism (micro‐biological theory) (Bueno et al . 2018). Figure 2 gives a comparison of the conventional two‐step theory for nitrification and denitrification in two different reactors with the different theories describing the mechanisms of single‐step SND in one reactor.…”

“…The anoxic micro‐environment creates a diffusion limitation in the centre of the activated sludge flocs or biofilms on account of the nitrifiers surviving in the aerobic regions characterized by high DO (above 1–2 mg l −1 ), and the denitrifiers surviving in the anoxic zones (DO <0·5 mg l −1 ) (Bueno et al . 2018). It has been reported that, the enzyme activity of the conventional denitrifying bacteria was significantly inhibited at high DO levels (>5·0 mg l −1 ) in aquaculture systems (Nootong et al .…”