[Start-up of Combined Floc-granule CANON Process and the Effects of SRT on Reactor Performance].

To shorten the start-up time of CANON process and guide the sludge dischargement in the practical project, the start-up of CANNON process and influence of different flocs SRT were studied by inoculation ANAMMOX granules of different proportions in two same specifications of SBR reactor. During the experiment, the temperature was controlled at 30℃±1℃ and pH was 7-8. The results showed that it was not good for CANON process rapid start-up when the two reactors were inoculated with 5% and 10% ANAMMOX granules respectively and the initial FA concentration exceeded 44 mg·L-1. When the two reactors were inoculated with 5% and 10% ANAMMOX granular sludge, the reactors were started-up successfully on Day 46 and Day 35, respectively. When the flocs SRT was maintained at 30 d, 90 d and un-initiative discharge respectively, the average total nitrogen removal rate could reach 0.35 kg·(m3·d)-1 stably. The quantitative PCR results of the three different flocs SRT showed that with increasing flocs SRT, the abundance of AOB was relatively stable, the abundance of ANAMMOX increased slightly, while the abundance of NOB significant increased. Therefore, it is necessary to elutriate flocs from reactor for decreasing the quantity of NOB and long-term stable operation of the CANON process.

[Start-up of Granule CANON Process and the Strategy for Enhancing Total Nitrogen Removal Rate].

To shorten the start-up time of the CANON granular sludge process and improve the total nitrogen removal rate in the engineering, the start-up method of CANON granular sludge process and the strategy for enhancing the total nitrogen removal rate were studied in an SBR reactor. During the experiment, the temperature was controlled at 30℃±1℃ and the pH was 7-8, the aeration rate and settling time were operated according to the sludge properties and effect of nitrogen removal. The results showed that the transition of the sludge properties from combined floc-granule to granule was realized after 55 d. The total nitrogen removal rate reached 0.32 kg·(m3·d)-1 and remained stable after 117 d, thus the reactor was started up successfully. With constant improvement of the aeration rate, the average NRR was maintained at 1.35 kg·(m3·d)-1 after 77 d and improvement of the process load was achieved. The results showed that there was good correlation between the NRR and DO, therefore, the NRR can be determined by observing the DO and the process can be maintained stably.

[Stability of the CANON Process Based on Real-Time Control Technologies].

In order to achieve the optimization of the CANON process, ensuring the stability of water quality and increasing the removal rate of ammonia nitrogen, the stability of CANON process water quality under real-time control was studied in the SBR reactor. During the experiment, the temperature was controlled at 30℃±1℃ and the pH was 7-8, based on the corresponding relationship between indirect parameters and nitrogen pollutants, the real-time control strategy was formulated. The results showed that when the influent ammonia nitrogen concentration was 917-1540 mg·L-1, the residual ammonia nitrogen concentration of 6 mg·L-1 can be used as the control parameter to meet the requirements of process stability but the ammonia nitrogen sensor had many problems such as high costs and large errors. The characteristic points and platforms of pH, DO, and ORP value can be the automatic control parameters, which can maintain the long-term stable operation of the CANON process and ensure that the average ammonia nitrogen removal rate is above 99% and the effluent quality is stable.

[Performance stability of CANON reactor and temperature impact].

In order to study long-term effect of completely autotrophic nitrogen removal over nitrite (CANON) reactor, performance stability was investigated by using synthetic inorganic ammonia-rich wastewater as raw water with a continuous flow CANON reactor. Both performances of short-cut nitrification and ANAMMOX were stable for more than one year. Under the condition that inner temperature at 35 degrees C +/- 1 degrees C, pH 7.39 and 8.01, and hydraulic retention time 3.7-5.1 h, the average total nitrogen removal load was 1.8 kg x (m3 x d)(-1), and the average and maximum total nitrogen removal efficiency were 65.09% and 81.65% respectively. Under sudden low temperature conditions, both ANAMMOX bacteria and AOB were inhibited, however, the ANAMMOX bacteria were inhibited more, which caused highly accumulated nitrite. When temperature increased to 35 degrees C as normal, the performance of CANON reactor recovered soon, which means low temperature impact will have no significant influence on stability. When the temperature reached more than 50 degrees C, the activity of ANAMMOX bacteria was completely destroyed, so high temperature must be avoided, though AOB can recovered to normal in one week.

[Autotrophic nitrogen removal and enhanced biological phosphorus removal from municipal wastewater in a three-sludge system].

Using a three-sludge system consisted of anaerobic/oxic (A/O) process, partial nitritation and anaerobic ammonium oxidation (ANAMMOX) reactors, cost-effective removal of nitrogen and phosphate from municipal wastewater was achieved. The experimental results showed that effluent total phosphorus (TP) of the A/O system was less than 0.5 mg/L under hydraulic retention time (HRT) of 3.6 h. Partial nitritation with nitrite accumulation efficiency of 75% -96% was realized in the partial nitritation system under room temperature, DO < 0.2 mg/L and HRT of 4.6 h. Under temperature of 27-30 degrees C and HRT of 1.4 h, effluent total nitrogen (TN) and TN removal rate of ANAMMOX reactor were less than 8 mg/L with the minimum value of 1.6 mg/L and 0.57 kg/(m3 x d), respectively. In the three-sludge system, phosphate accumulating organisms, ammonia-oxidizing bacteria and Anammox bacteria existed under suitably environmental condition to optimize the microbial community structure and improve treatment efficiency of various units. Autotrophic nitrogen removal can reduce 62.5% of the oxygen supply, save 100% of denitrification carbon sources theoretically, lower the sludge production, and greatly decrease carbon dioxide emission. As compared to traditional biological nutrient removal process, the three-sludge system has great advantages and potential in energy saving and carbon dioxide emission reduction to realize sustainable development of water resources.

[Study of CANON process start-up under aerobic conditions].

The start-up of CANON process was studied to reveal adaptability and how to condense time of start-up with a lab-scale experiment. During start-up stage, temperature was controlled at 35 degrees C +/- 1 degrees C, pH was 7.39-8.01 and free ammonium was 2.89-12.37 mg x L(-1). Partial nitritation was first built up in 60th day and kept steady, nitrite accumulation rate (NO2(-) -N/NO(x) (-) -N) was up to 98%. In the 160th day, the reactor started to show effects of anaerobic ammonium oxidation, and in the 210th day, CANON process was started-up under aerobic conditions successfully, and total nitrogen removal load was 1.22 kg/(m3 x d) and 70% removal rate on average was attained. When using ammonium wastewater without organic carbon sources as influent, there are two signs to indicate the CANON start-up: first, nitrogen gas was produced in carriers; the other one was the ratio of total nitrogen loss and increased nitrate keep steady, and in this study average ratio was 8.61 compared to theoretical value 8.

[Partial nitrification of digested sludge liquor with low C/N and high-concentration ammonia].

The experimental system consisted of anoxic filter and aerobic suspended carrier biofilm reactor. The partial nitrification was achieved and maintained stably in the aerobic reactor under normal temperature (15-29 degrees C) and high DO (6-9 mg/L). The nitritation with 70%-80% nitrite accumulation efficiency was obtained when FA concentration was in the range of 1.0-10.3 mg/L by controlling influent ammonia loading rate (ALR), ratio of alkalinity and ammonia and HRT in the aerobic reactor. The effluent nitrite/ammonia ratio was about 1.25 when the average influent ammonia, influent ALR and influent ratio of alkalinity and ammonia were 315.80 mg/L, 0.43 kg/(m3 x d) and 5.25, respectively. So the effluent of partial nitrification process provided the influent substrate demand for the following ANAMMOX process. The integrative analysis indicated that the proper FA concentration was the main factor achieving the partial nitrification. The study developed a novel partial nitrification technology adapt to water characteristics of digested sludge liquor.

[Partial nitrification in SBR under normal temperature and limited oxygen condition].

Partial nitrification was researched in a SBR reactor under the limited oxygen condition (DO 0.3-0.4 mg/L) and the normal temperature of 14.1-24.2 degrees C to produce the correct influent for ANAMMOX process from secondary wastewater (NH4+ -N 30-100 mg/L). The influent for the ANAMMOX process must be composed of NH4+ and NO2- in a ratio of 1/1.31 and therefore only a partial nitrification of ammonium into nitrite was required. The control of alkalinity and the indication of monitoring profile of DO allowed to achieve this partial nitrification with a final effluent only composed of NH4+ -N and NO2(-) -N at the right stoichiometric ratio. The equal consumption of HCO3- /NH4+ in secondary wastewater resulted in a natural pH decrease when approximately 57% of NH4+ -N was oxidized. When the pH dropped to a certain level, the lowering of the metabolic rate of the ammonium oxidizer would lead to rapid decline of the oxygen uptake rate (OUR) in reactor, and the jump characteristic point (it was distinguished by the jump over 1.0 mg/L of DO value) in the DO profile would emerge, which signalled the end-point of the partial nitrifying. The optimum alkalinity of partial nitrification was studied under 4 concentrations in the range of NH4+ -N 30-100 mg/L of secondary wastewater. The result indicated that the bicarbonate/ammonium ratio was the key factor influencing the nitrification ratio (NO2-/NH4+), and it was absolutely possible to successfully achieve partial nitrification that provided right substrate for ANAMMOX reactor through the control of the alkalinity.

[Effects of Mn2+, Mo6+ and Zn2+ on the components change of extracellular polymeric substances in activated sludge].

By specific oxygen uptake rate, (SOUR) measurements of activated sludge with different metal ion concentration, the optimal stimulation concentrations of Mn2+, Mo6+ and Zn2+ were determined. Then within each metal ion stimulation concentration range, extracellular polymeric substances (EPS) were extracted from activated sludge and its components (protein, polysaccharide and nucleic acid) contents changes were investigated. The results showed that the optimal stimulation concentration of each metal ion is 1mg x L(-1). EPS components of activated sludge vary obviously with Mn2+ and Zn2+ concentration change but not with Mo6+. After storage at low temperature, EPS quantities in activated sludge are reduced with polysaccharide reduction is the most.