One-step start-up and subsequent operation of CANON process in a fixed-bed reactor by inoculating mixture of partial nitrification and Anammox sludge.

The feasibility of one-step start-up of CANON process in a FBR by inoculating mixture of partial nitrification and Anammox sludge as well as its subsequent operation performances were investigated in the present study. The FBR was operated for around 3 months. The CANON process was quickly started up within 21 days. The max total nitrogen (TN) removal rate reached 183.61 g m-3 d-1 with the TN removal efficiency of 91.81% on day 95. The CANON process exhibited a good capability for resistance to loading shock and restoration from the unstable state. The mature CANON biofilms displayed a morphology of aggregates and had porous and microporous structure. The structural characteristics of the biofilms were conducive to improve the transferring of substrates and products. AOB and Anammox bacteria absolutely predominated in the mature biofilms and furthermore established a balanced interaction relationship. The microbial community structure contributed to the relatively stable operation performances.

Enhancement of Anammox performances in an ABR at normal temperature by the low-intensity ultrasonic irradiation.

A lab-scale ultrasound enhancing Anammox reactor (ABRU) was established and irradiated once a week by ultrasound with the optimal parameter (frequency of 25.0 kHz, intensity of 1.00 W cm-2 and exposure time of 36.0 s) obtained by response surface methodology (RSM). ABRU and the controlled Anammox reactor (ABRC) without ultrasonic treatment were operated in parallel. The start-up time of Anammox process in ABRU (59 d) was shorter than that in ABRC (69 d). At the end of the nitrogen load-enhancing period, NLR (0.500 kg N m-3 d-1) and NRR (0.430 kg N m-3 d-1) in ABRU were both higher than NLR (0.400 kg N m-3 d-1) and NRR (0.333 kg N m-3 d-1) in ABRC. The results of RTQ-PCR demonstrated that the specific low-intensity ultrasound irradiation improved the enrichment levels of AnAOB in mature sludge. SEM images and the observation of the macroscopic morphology of mature sludge showed that the ultrasound irradiation strengthened the formation of Anammox granular sludge, thereby improved the interception capacity and impact load resistance of the reactor, and enhanced the nitrogen removal performance in ABRU. The ultrasonic enhanced Anammox reactor based on an ABR with the optimal parameters can promote the rapid start-up and efficient and stable operation of the Anammox process at normal temperature (around 25.0 °C).

Start-up and operational performance of Anammox process in an anaerobic baffled biofilm reactor (ABBR) at a moderate temperature.

A lab-scale anaerobic baffled biofilm reactor (ABBR) was used as a novel reactor to start up Anammox process at a moderate temperature around 20 °C and an innovative filling module was adopted as support material. Quick start-up of Anammox process from the aerobic activated sludge was achieved after 47 days operation. The max nitrogen loading rate and nitrogen removing rate attained 1.00 kg N m-3 d-1 and 0.90 kg N m-3 d-1 after 161 days operation. Scanning electron microscope photographs showed that the structure as well as the states of the micro-aggregates (micro-aggregates sticking on a non-woven fiber, entangling non-woven fibers and enwrapped by non-woven fibers) enhanced biomass retention for Anammox bacteria. Microbial community analysis showed that Anammox bacteria were effectively enriched with Candidatus Brocadia, Candidatus Jettenia and Candidatus Kuenenia being the main Anammox species in the mature biofilms. This contributed to the excellent Anammox operation performance at the moderate temperature.