Sitong Liu

The development of simultaneous partial nitrification, ANAMMOX and denitrification (SNAD) process in a single reactor for nitrogen removal.

The simultaneous partial nitrification, ANAMMOX and denitrification (SNAD) process was validated to potentially remove ammonium and COD from wastewater in a single, oxygen-limited, non-woven rotating biological contactor (NRBC) reactor. An ammonium conversion efficiency of 79%, TN removal efficiency of 70% and COD removal efficiency of 94% were obtained with the nitrogen and COD loading rate of 0.69 kgN/m(3)d and 0.34 kg/m(3)d, respectively. Scanning electron microscopy (SEM) observation and fluorescence in situ hybridizations (FISH) analysis revealed the existence of the dominant groups of bacteria. As a result, the aerobic ammonia-oxidizing bacteria (AOB), with a spot of aerobic heterotrophic bacteria were mainly distributed in the aerobic outer part of the biofilm. However, ANAMMOX bacteria with denitrifying bacteria were present and active in the anaerobic inner part of the SNAD biofilm. These bacteria were found to exist in a dynamic equilibrium to achieve simultaneous nitrogen and COD removal in NRBC system.

Start-up of the Anammox process from the conventional activated sludge in a membrane bioreactor

A lab-scale membrane bioreactor (MBR) was used to start-up the anaerobic ammonium oxidation (Anammox) process from the conventional activated sludge for 2 months. Results indicated the MBR could be a novel and suitable system for start-up of the Anammox process. The Anammox activity appeared after 16 days operation, and the average removal efficiencies of ammonia and nitrite were both over 90% in the end. A final specific Anammox activity of 0.35 g NH(4)(+)-N+NO(2)(-)-N (gVSS *d)(-1) was obtained. Fluorescence in situ hybridization (FISH) analysis confirmed the existence of Anammox bacteria and aerobic ammonia oxidizing bacteria. On the basis of results on MBR performance and FISH analysis, it was proposed that the start-up process was essentially a microbial community succession under man-made disturbance, and a climax community with Anammox bacteria as the dominant population was finally established.

The influence of controlling factors on the start-up and operation for partial nitrification in membrane bioreactor.

In this study, the partial nitrification process was started-up successfully in a membrane bioreactor (MBR). The influence of temperature and DO was investigated by sequencing operation of membrane bioreactor. The preferred values were proved as 35 degrees C and 0.3-0.5mg/L, respectively, and were indicated as indispensable controlling factors. In order to increase the sludge concentration, new seed sludge was added into the reactor, which caused the absolute destruction of the reactor performance. The results of reactor experiments showed that the free ammonia (FA) concentration of 74 mg NH(3)/L, as the influent ammonium concentration of 600 mg N/L, was a useful and effective factor to recover the partial nitrification performance. Fluorescence in situ hybridization analysis indicated that nitrifiers hybridizing with NIT3 and NSR1156 were present and active in MBR, which were then eliminated under high FA concentration. The microbiological community analysis further provided the necessary biological information for the realization of partial nitrification.

Evaluation of oxygen adaptation and identification of functional bacteria composition for anammox consortium in non-woven biological rotating contactor

In this study, the anammox consortium was found to adapt to the wastewater containing dissolved oxygen (DO), as the DO was gradually increased. Batch tests indicated the maximum aerobic ammonium oxidizing activity of the consortium was 1.38mmolNH4+-N(gVSS)(-1)day(-1), which played key roles in the oxygen consumption process; the maximum anaerobic ammonium oxidizing activity was slightly decreased after long-term oxygen exposure, but only from 21.23mmolNH4+-N(gVSS)(-1)day(-1) to 20.23mmolNH4+-N(gVSS)(-1)day(-1). Microbiological community analysis identified two strains similar to Nitrosomonas eutropha were responsible for oxygen consumption, which were able to exist in the autotrophic anaerobic condition for long periods and protect anammox bacteria Planctomycetales from the influence of oxygen. Microbiological composition analysis showed Nitrosomonas and Planctomycetales approximately accounted for 10% and 70% of the bacteria, respectively. The possibility of cultivation anammox consortium in presence of DO will lead to substantial savings of energy and resource in the industrial application.

Application of anaerobic ammonium-oxidizing consortium to achieve completely autotrophic ammonium and sulfate removal

The simultaneous ammonium and sulfate removal was detected in an anammox reactor, consisted of ammonium oxidization with sulfate deoxidization, and subsequently traditional anammox process, in via of middle medium nitrite with solid sulfur and N2 as the terminal products. The pure anammox bacteria offered a great biotechnological potential for the completely autotrophic reaction indicated by batch tests. Denaturing gradient gel electrophoresis (DGGE) analysis further revealed that a new organism belonging to Planctomycetales was strongly enriched in the defined niche: the redox of ammonium and sulfate. The new species Anammoxoglobussulfate was so considered as holding a critical role in the ammonium oxidization with sulfate deoxidization to nitrite. Afterwards, the Planctomyces existing in the bacteria community performed the anammox process together to achieve the complete nitrogen and sulfate removal. The potential use of sulfate as electron acceptor for ammonium oxidizing widens the usage of anammox bacteria.

Enhancement of anaerobic methanogenesis at a short hydraulic retention time via bioelectrochemical enrichment of hydrogenotrophic methanogens

Anaerobic digestion (AD) is an important energy strategy for converting organic waste to CH4. A major factor limiting the practical applicability of AD is the relatively long hydraulic retention time (HRT) which declines the treatment efficiency of digesters. A coupling process of anaerobic digestion and electromethanogenesis was proposed to enhance anaerobic digestion at a short HRT in this study. Microorganisms analysis indicated that the electric-biological reactor enriched hydrogenotrophic methanogens in both cathodic biofilm and suspended sludge, helping achieve the high organic removal (71.0% vs 42.3% [control reactor]) and CH4 production (248.5mL/h vs 51.3mL/h), while the additional electric input was only accounted for 25.6% of the energy income from the increased CH4 production. This study demonstrated that a bioelectrochemical enhanced anaerobic reactor could improve the CH4 production and organic removal at a short HRT, providing an economically feasible scheme to treat wastewater.

The Enrichment of Anammox Bacteria in Non-Woven Rotating Biological Contactor Reactor

A novel non-woven rotating biological contactor reactor (NRBC) was started up to enrich anammox bacteria. Research results showed that after 100 days operation, the nitrogen removal rate was arrived as high as 3.4 kgNm-3d-1 in the condition of HRT 4 h, influent ammonium and nitrite concentration 350 mg L-1. Scanning electron micrograph (SEM) showed that the typical cauliflower aggregates were tightly attached on the support material. It has been proved that NRBC reactor is a very suitable experimental set-up for the enrichment of anammox bacteria.