[Analysis of Precipitation Formation in Biofilm CANUN Reactor and its effect on Nitrogen Removal].

A CANON reactor with polymeric sponge as carrier was started by incubating sludge from another CANON reactor using synthetic inorganic ammonia-rich wastewater as raw water, and was operated at 30 degrees C +/- 1 degree C, pH 6.92-8.52. The precipitation on the surface of carriers was studied in this paper, including influence on nitrogen removal efficiency, causes for formation and composition. The results showed that: (1) the precipitation could influence the distribution of substrate to undermine the performance of CANON reactors; (2) the precipitation was calcium carbohydrate; (3) the production of precipitation may be a common result of four effects that were the regulatory effect of microorganisms on pH value, stripping effect, the role of extracellular polymers, adsorption of sponge and simultaneous chemical, biological reactions; (4) once the precipitation formed, it was difficult to recover to normal. Therefore, some measures are necessary to avoid precipitation, including: (1) raw water pretreatment to reduce the concentrations of Ca2 and Mg2. (2) ensuring short-cut nitrification stable, which could avoid increase of pH because of reduction of DO; (3) we can choose other carriers to reduce precipitation, which must ensure the optimal total nitrogen removal performance and stable short-cut nitrification.

[Effects of Hydraulic Retention Time and Dissolved Oxygen on a CANON Reactor with Haydite as Carrier].

One Completely Autotrophic Nitrogen Removal Over Nitrite ( CANON) reactor with haydite as carrier was investigated to study the effects of different hydraulic retention time ( HRT) and dissolved oxygen (DO) on CANON reactors by seeding sludge from another mature CANON reactor and using synthetic inorganic ammonia-rich waste water as influent. During the experiment, the concentration of influent ammonia nitrogen was basically unchanged, the HRT of the reactor were 9, 7, 5 h in turn and the range of DO was 1.16-3.20 mg x L(-1). The results showed that: (1) When DO was 1.20-1.75 mg x L(-1), despite the increase of DO can improve AOB's activity and matrix mass transfer in the system, NH4(+) -N and TN removal efficiency were still fell with the shortening of HRT for the CANON reactor, especially when DO was higher than 2.50 mg x L(-1), TN removal efficiency dropped sharply; (2) Under the condition that DO was 1.20-1.75 mg x L(-1), with the shortening of HRT, partial nitritation tended to be stable in the CANON process, and when DO was higher than 1.75 mg x L(-1), even if HRT was shorter, partial nitritation was still severely damaged; (3) Under the condition that DO was 1.20-1.75 mg x L(-1) and HRT was 7 h, for the CANON reactor, partial nitritation and total nitrogen removal efficiency kept well. Hydraulic retention time and dissolved oxygen both are important operational parameters for biological wastewater treatment process, which could directly affect the effect of biological treatment and effluent quality, so to choose appropriate hydraulic retention time and dissolved oxygen coordinately is very important to improve the effect of treatment of ammonium-rich wastewater by CANON process.

[Start-up by inoculation and operation of a CANON reactor with haydite as the carrier].

A CANON reactor with haydite as the carrier was started by incubating sludge from another CANON reactor and using synthetic inorganic ammonia rich wastewater as the raw water. Both start-up and operation were studied. The result showed that haydite can be a suitable carrier for CANON reactor. With this carrier, start-up of CANON reactor can be completed in 60 days with total nitrogen removal load up to 0.79 kg x (m3 x d)(-1), when the reactor was equipped with a water jacket to maintain the water temperature at 30 degrees C +/- 1 degrees C, and pH at 7.00-8.08, hydraulic retention time of 9 hours. The critical range of dissolve oxygen for CANON reactor was 1.12-1.69 mg x L(-1), and both characteristics of short-cut nitrification and ANAMMOX were stable. However, the CANON reactor can be instable if dissolve oxygen concentration increased above this range. Although the ratio of nitrate variation to total nitrogen variation (deltaNO3(-) -N/deltaTN) was 0.150-0.204, which deviated a little from its theoretical value, 0.127. The performance of CANON reactor kept relatively stable. The total nitrogen removal efficiency was up to 75.56% while total nitrogen removal load was 0.97 kg x (m3 x d)(-1), which means the temperature for CANON reactor can be decreased to 25 degrees C at least.