Metabolic properties of a mixed culture of aerobic ammonia oxidizers and its optimal reaction conditions.

The aerobic ammonia oxidation is an important process for nitrogen removal from wastewater with high ammonia concentration. Here, we investigated the metabolic properties of a mixed culture of aerobic ammonia oxidizers and determined its optimal reaction conditions. The maximum specific rate of NO(2)(-)-N formation of the culture was 14.9 mg N mg(protein)(-1) d(-1). The ammonia oxidation capacity was positively correlated with the microbial biomass concentration. Haldane model showed that the half-saturation constant (K(s)) for NH(4)(+)-N of the culture was 78.5 mg L(-1), and the inhibition constant (K(i)) for NH(4)(+)-N was 393.4 mg L(-1). The acetic acid and beef extract had significant inhibitory effects on ammonia oxidation, while there was little effect of methanol and glucose on ammonia oxidation. Orthogonal experiments with range analysis, variance analysis, factor contribution analysis and response surface analysis confirmed the optimal reaction conditions for ammonia oxidation to be 30-32 °C, pH 7.8-8.0, and 150-200 mg L(-1) NH(4)(+)-N concentration.

Distribution and diversity of anaerobic ammonium-oxidizing bacteria in the sediments of the Qiantang River.

Anaerobic ammonium oxidation (anammox) is an important process in the marine nitrogen cycle. However, little is known about the distribution, diversity and abundance of anammox bacteria in inland river ecosystems. Here, we found the presence of diverse anammox bacteria in a freshwater river - the Qiantang River, Zhejiang Province (China). The phylogenetic analysis of 16S rRNA genes showed that Brocadia genus, Kuenenia genus, Scalindua genus and three new anammox bacterial clusters could be detected together in Qiantang River sediments, suggesting a higher anammox bacterial diversity in the Qiantang River ecosystem than in open ocean environments where only Scalindua genus was detected. Brocadia and Kuenenia appeared to be the most common anammox bacterial genera in the Qiantang River. Redundancy analysis showed that the sediment organic carbon (OrgC) content had significant influence on the distribution of anammox bacteria in Qiantang River sediments. Pearson correlation analyses showed that OrgC content significantly influenced the anammox bacterial diversity. The results of real-time quantitative PCR showed spatial variations of anammox bacterial abundances which were highly correlated with the sediment total inorganic nitrogen content. These results demonstrated the distribution of diverse anammox bacteria and the influences of environmental factors on anammox bacterial communities in Qiantang River sediments.

Quantitative comparison of stability of ANAMMOX process in different reactor configurations.

A new stability evaluating system for ANAMMOX comprising three instability indices i.e. coefficient of variation ratio, coefficient of range ratio and coefficient of regression function derivative was established. Three lab-scale ANAMMOX reactors viz upflow anaerobic sludge blanket (UASB) reactor, upflow stationary fixed film (USFF) reactor and anaerobic sequencing batch reactor (ASBR) were compared for their stability based on the established criterion against the hydraulic and substrate concentration shocks. The results showed that all ANAMMOX reactors under investigation were more tolerant to the hydraulic shock than substrate concentration shock. The UASB reactor was the most stable reactor configuration towards substrate concentration shock, followed by the USFF reactor and ASBR. However, the ASBR proved the most tolerant to hydraulic shock, followed by the UASB reactor and USFF reactor. In terms of stability, UASB reactor was more suitable configuration compared with USFF reactor. The instability indices proved to be effective and explicit for the evaluation of ANAMMOX systems.