High nitrite concentration accelerates nitrite oxidising organism's death

Abstract

High nitrite is a known operation parameter to inhibit the biological oxidation of nitrite to nitrate. The phenomenon is traditionally expressed using a Monod-type equation with non-competitive inhibition, in which the reaction associated with the biomass growth is reduced when high nitrite is present. On the other hand, very high nitrite is also known to slay nitrifiers. To clarify the difference between the growth inhibition and the poisoning, cell counting for living microorganisms in the nitrite oxidiser-enriched activated sludge was conducted in batch conditions under various nitrite concentrations together with measurements of biomass chemical oxygen demand (COD) concentration and oxygen uptake rate. The experiments demonstrated that these measureable parameters were all decayed when nitrite concentration exceeded 100-500 mgN/L at pH 7.0 in the system, indicating that nitrite poisoning took place. Biomass growth was recognised in lower range of nitrite which was expressed with growth inhibition only. Based on the response, a kinetic model for the biological nitrite oxidation was developed with a modification of IWA ASM1. The model was further utilised to calculate a possibility to wash out nitrite oxidiser in the aeration tank where a part of the return activated sludge was exposed to high nitrite liquor in a side-stream partial nitritation reactor.

Ammonium-derived nitrous oxide is a global source in streams

“…The NO 3 − and NO 2 − produced by nitrifying bacteria can be directly used in the ND pathway as substrates 38 , whereas denitrifying bacteria in the HD process need to consume adenosine triphosphate (ATP) to absorb NO 3 − from the environment 36 . Additionally, the nir KS gene is significantly more abundant in nitrifying microorganisms than in denitrifying microorganisms ( p = 0.003); hence, in the consumption of NO 2 − for detoxification 39 – 41 , the ND pathway has greater potential to alleviate the toxic effects of nitrite on microorganisms 39 – 41 than does the HD pathway. Furthermore, nitrifiers have the potential to produce large amounts of N 2 O because, based on reports to date, nitrifying bacteria do not contain N 2 O reductase 42 .…”

Kinetics for the Methanogen’s Death in the Acidic Environments

“…On the other hand, the biocidal inhibition is correlated with the biomass loss leading to irreversible activity loss. Hence the biocidal inhibitions could be expressed as a stochastic summation of the inactivation probabilities given from the biocidal substances that occur on the microorganism over time [11] (i.e., a summation of the first-order coefficients for the inherent biomass decay, decay by the inhibitory substance A and decay by the inhibitory substance B…). Using the proposed approach, the VFA (and proton) inhibition could be theoretically applied to biostatic, biocidal or both type of the inhibitions.…”

The effect of sludge retention time (SRT) on the Nitrifier typical kinetics at ambient temperature under the low ammonia density

“…As an essential function in the biological N-removal process, Nitrifier activity is focused which was affected by various environmental factors such as dissolved oxygen (DO) (Tocchi et al 2012), temperature (Liu et al 2018a(Liu et al , 2018bLi et al 2019), pH (Hall 1974;Metcalf 2003;Liu et al 2015), substrate concentrations (Peng et al 2012) and sludge retention time (SRT) (Wu et al 2011;Qiu et al 2019) in activated sludge system operation.…”

“…The measurement results of b are shown in Figure 2(d) with the standard error line. It is obtained that when the SRTs was 40 d, 20 d, 10 d, and 5 d, b is 0.1750, 0.1810, 0.1850, 0.1940 d -1 respectively, and the linear correlation was above 96%, by using Equation (2)(Liu et al 2018a(Liu et al , 2018b to matching the experimental data. As shown in Figure5, b had the upward trend with the index is 0.0331, and the correlation is 0.9789 with the decrease of SRTs.…”