Peiyu Zhang

Performance and microbial community of simultaneous anammox and denitrification (SAD) process in a sequencing batch reactor.

A sequencing batch reactor (SBR) was used to test the simultaneous anammox and denitrification process. Optimal nitrogen removal was achieved with chemical oxygen demand (COD) of 150mg/L, during which almost all of ammonia, nitrite and nitrate could be removed. Organic matter was a key factor to regulate the synergy of anammox and denitrification. Both experimental ΔNO2(-)-N/ΔNH4(+)-N and ΔNO3(-)-N/ΔNH4(+)-N values deviated from their theoretical values with increasing COD. Denitrifying bacteria exhibited good diversity and abundance, but the diversity of anammox bacteria was less abundant. Brocadia sinica was able to grow in the presence of organic matter and tolerate high nitrite concentration. Anammox bacteria were predominant at low COD contents, while denitrifying bacteria dominated the microbial community at high COD contents. Anammox and denitrifying bacteria could coexist in one reactor to achieve the simultaneous carbon and nitrogen removal through the synergy of anammox and denitrification.

Comparison between MBR and A/O processes treating saline wastewater

Abstract Membrane bioreactor MBR and A/O processes are employed to treat saline wastewater. The mixed liquid suspended solids in the MBR and A/O were 7,000 and 3,500 mg/L, respectively. With the same influents, MBR process was more suitable for the treatment of high-salinity wastewater. The chemical oxygen demand and ammonia removal efficiencies were 75 and 82%, respectively, with the salinity of 24.5 g/L. Both were higher than that through the A/O process. Autotrophic nitrifying bacteria could be enriched and had sufficient time to accommodate to the saline environment. Both sludge volume index (SVI) decreased with salinity increment. However, the SVI of MBR dropped more than that of A/O, which indicated a better sludge-settling property in the MBR process. Filamentous bacteria existed in the A/O reactor and made the sludge-settling property worse than that in the MBR process. Membrane fouling occurred inevitably during the MBR process. Microbes and organics could be removed by combined physical and chem...

Performance and sludge characteristics of anammox process at moderate and low temperatures

A sequencing batch reactor (SBR) was used to investigate the performance and sludge characteristics of anammox process at moderate and low temperatures. The initial pH was 7.5 and hydraulic retention time (HRT) was 3 h. When temperature was 25-35 °C, nitrogen removal rate (NRR) fluctuated from 1.67 to 1.82 kg/m3·d. However, when temperature dropped to 15 °C, NRR suddenly decreased by 0.48 kg/m3·d. Larger activation energy was acquired at lower temperature, and it was difficult to achieve efficient nitrogen removal under low temperature. When temperature declined to 10 °C, ΔNO2−-N/ΔNH4+-N and ΔNO3−-N/ΔNH4+-N reached 1.02 and 0.27, respectively. Inhibition resulting from low temperature on anammox activity was recoverable, and the modified Boltzmann model was appropriate to analyze recovery feature of anammox process. Low temperature not only led to poor nitrogen removal, but also affected sludge size and feature.