Abstract
The interaction of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) is of considerable importance in nitrification process. Ecophysiological interactions between the communities of AOB and NOB were investigated by monitoring NO2− as the intermediate compound in an organic carbon-depleted nitrifying activated sludge fed only NH4+ as a nitrogen source (40 mg/L). The presence of boom and bust (feast and famine) cycle successfully indicates the activity cycles of AOB and NOB through cultivation-dependent method. The maximum growth rate and yield for AOB in nitritation-dominant period were (0.67 day−1, 0.17 gVSS gN−1) and for NOB in nitratation-dominant period were (0.71 day−1, 0.072 gVSS gN−1). Soluble microbial products (SMP) and extracellular polymeric substances (EPS) generated by AOB were 1.2 and 1.8 mg/L, respectively, while NOB produced 0.6 mg/L of SMP and 1 mg/L of EPS. While NOB were low in utilization-associated products (UAP) (0.07 mg/L) and biomass-associated products (BAP) (0.12 mg/L), AOB were higher in UAP (0.15 mg/L) and BAP (0.3 mg/L). The continuation presence of zero C/N ratio, in either inlet ratio or net available ratio for the microbial community, can prolong and enhance nitratation process. NOB enrichment and nitratation intensification strategy through zero C/N ratio are able to reduce remarkably microbial metabolites 50% lower than conventional process and enhance nitrification efficiency in activated sludge-involved processes.
Highlights
Biological treatment is widely used for municipal and industrial wastewaters (Massot et al 2012)
A reasonable explanation for the periodical cycle could be based on the first step in nitrification
The trend of nitrite accumulation correlates favorably with Kim et al (2008) and further supports the idea that nitrifiers were activated and dominated in nitrifier-enriched activated sludge (NAS) and making the results to be interpretable based on nitrite-dependent point of view
Summary
Biological treatment is widely used for municipal and industrial wastewaters (Massot et al 2012). Applied Water Science (2019) 9:131 polymeric substances (EPS) are mainly composed of proteins, carbohydrates, and humic substances (Kunacheva et al 2017). These metabolites create a residual organic matter in secondary effluent (Zhang et al 2017). Due to their impacts on the physio-chemical properties of microbial aggregates in the sludge, SMP are considered as major sludge floc component leading to keep the floc in a matrix. These major components are viewed as the key foulant causing irreversible biofouling of membrane bioreactors. Microbial metabolites are undergoing a revolution in terms of research focus in the field of environmental biotechnology
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