The effect of different nitrogen sources on denitrification with PHB under aerobic condition

Comparative study of activated sludge with different individual nitrogen sources at a low temperature: Effluent dissolved organic nitrogen compositions, metagenomic and microbial community

The objective of this study was to explore nitrogen removal, especially effluent dissolved organic nitrogen (DON) composition, relative genes and microbial community structures with four individual nitrogen sources at 5°C. Results show that effluent DON did not have dependent relationship with the TN removal rate (urea>ammonia chloride>L-Alanine>D-Alanine). With the same influent TN, the highest effluent DON was formed with urea; the lowest DON was fed with ammonia chloride. The main DON composition was the product of cell metabolism excluding urea, rather than the original substrate. Glutamic acid synthesizing process was of great importance to DON accumulation at 5°C. The nitrogen source type was important to the diversity and heterogeneity of the nitrogen removal genes. Bacterial population structure using redundancy analysis (RDA) showed Simplicispira occupied a higher abundance remarkably in the reactors feeding with urea, and Dyadobacter occupied higher feeding with l-Alanine.

Impact resistance of different factors on ammonia removal by heterotrophic nitrification-aerobic denitrification bacterium Aeromonas sp. HN-02

To give reference for the application of heterotrophic nitrification-aerobic denitrification bacteria in actual wastewater treatment, the impact resistance of extreme pH, low temperature, heavy metals and high salinity on ammonia removal by a typical heterotrophic nitrifying-aerobic denitrifying bacterium Aeromonas sp. HN-02 was investigated. The results showed that HN-02 demonstrated strong acid- and alkali-resistance. In addition, it remained active at 5°C, and the removal rates of ammonia and COD were 0.90 mg L(-1)h(-1) and 22.34 mg L(-1)h(-1), respectively. Under the same extent of immediate temperature drop, the temperature correction coefficients of ammonia, COD removal rates and cell growth rate were close. Moreover, HN-02 could survive in the solution containing 0.5 mg L(-1) Cu(2+) or 8 mg L(-1) Zn(2+), or 0.5 mg L(-1) of equivalent Cu(2+)-Zn(2+). Furthermore, efficient ammonia removal was retained at salinity below 20 g L(-1), thus it could be identified as a halotolerant bacterium. At last, stronger stress resulted in higher ΔCOD/ΔTN ratio.