| Comparing to complete nitrification and denitrification processes, shortcut nitrification and denitrification has some obvious advantages on energy consumption, HRT and sludge production, thus it has been a research concern in biological nitrogen removal in wastewater treatment. However, the reaction condition of shortcut nitrification and denitrification is so harsh that municipal sewage can hardly achieve it, and the process needs a long start-up time, also the system of shortcut nitrification is unstable and it would transfer to complete nitrification when influenced by external conditions. So it is of great significance to achieve quick start-up of shortcut nitrification of municipal wastewater and find the critical condition to maintain stable and lasting shortcut nitrification denitrification process. This paper studied the effects of sodium chlorate(Na Cl O3)on quick start-up, the stability and recovery performance of the shortcut nitrification system.This paper investigated the effects of Na Cl O3 concentration, influent p H values and the concentration of dissolved oxygen(DO) on partial nitrification process in a sequencing batch reactor(SBR) by adding Na Cl O3 to the sludge and artificial municipal wastewater, and the following conclusions have been made: a certain concentration range of Na Cl O3 could inhibit the ammonia oxidizing bacteria(AOB) and nitrification bacteria(NOB), and AOB could gradually adapt to the inhibition whereas NOB could not. Na Cl O3 would seriously inhibit the activity of NOB and AOB when n(Na Cl O3)> 1.8 mmol /(g MLSS · L). The increase of DO concentration could weaken the inhibition Na Cl O3 to NOB, and the Na Cl O3 could not achieve effective suppression of NOB when DO=2.0 ~ 2.5mg / L. The ammonia oxidizing would be influenced when influent p H <7.0~7.5, and nitrite accumulation rate would increase with the p H increasing, the highest nitrite accumulation rate could reach 98% when p H = 8.0 ~ 8.5 and 8.5 ~ 8.7. The shortcut nitrification process could quick start-up in 12 days under the optimal operating condition: n(Na Cl O3) = 1.2 mmol /(g MLSS · L), DO =0.5 ~ 1.0mg / L, influent p H =8.0 ~ 8.5.Based on the successful shortcut nitrification process using Na Cl O3, the stability of partial nitrification was analyzed, and the following conclusions had been made: DO concentration, influent p H value and temperature had an impact on the stability of shortcut nitrification system. When DO = 0.5mg / L ~ 2.0mg / L, the nitrite accumulation rate was more than 50% and the shortcut nitrification could be maintained. If the DO increased to 2.0mg / L ~ 2.5mg / L, the shortcut nitrification system was completely collapsed after 30 days, and the damaged system could not recover shortcut nitrification when decrease the DO back to 0.5mg / L ~ 1.0mg / L. When influent p H = 7.5 ~ 8.7, the variation of p H would not cause significant effect on partial nitrification; when p H=7.0 ~ 7.5, shortcut nitrification would be damaged to some extent and it still was shortcut nitrification; when p H = 6.5 ~ 7.5, the shortcut nitrification system completely collapsed, and the damaged system could achieve good shortcut nitrification again when recovered the p H to 8.0 ~ 8.5. When the temperature was 25 ℃ to 15 ℃, the shortcut nitrification system would not be damaged, and the removal rate of ammonia and accumulation rate of nitrite would be gradually reduced with the temperature decreasing. When the temperature was less than 10 ℃, shortcut nitrification system would be affected by low temperature, and nitrite accumulation rate was less than 50%, but the system could restore good nitrification effect when the temperature increased. |
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