| CRI has the advantages of simple operation,convenient management and low operating cost.However,its disadvantage is the low total nitrogen removal rate.Short-cut nitrification and denitrification has the advantages of high total nitrogen removal efficiency,and it has the advantages of saving aeration and saving organic carbon sources.Both are economically and technically feasible.This experiment tries to combine the two treatment methods to achieve complementary advantages.The key to short-cut nitrification and denitrification is short-cut nitrification of the system.If short-cut nitrification is achieved,short-cut nitrification and denitrification process will achieve 80%.Therefore,this experiment focuses onthe short-cut nitrification of the system.In this experiment,we triedto control and stabilize the reaction in the nitrite stage by controlling the DO,adding a certain concentration of inhibitors,and supplementing with other parameters in the CRI system,achieving the short-cut nitrification in the system.By studying the effects of different DO concentrations and different concentrations of sodium chlorate on the nitrite accumulation rate,we systematically studied the realization and the maintenance of short-cut nitrification in the CRI system and the stability of short-cut nitrification under real-time oxygen control conditions.The following findings were found throughout the experiment:(1)In the experiment that explores the nitrite accumulation in the system using dissolved oxygen as the main control parameter,it is found that at room temperature,pH = 8.0,the initial influent ammonia nitrogen is 110.11-120mg/L,COD is 310-560mg/L,the system intake air volume was adjusted,and there was no significant accumulation of nitrite nitrogen;the subsequent experimental wastewater concentration was reduced by 2/3,the ammonia nitrogen was 36-42 mg/L,and the COD was 100-165 mg/L,the amount ofair intake in the system was adjusted,and the effluent nitrite nitrogen was significantly accumulated,reaching a maximum of about 83 mg/L,and the nitrite nitrogen accumulation rate was close to 50%.It also shows that with the system containing high concentration of ammonia nitrogen as start-up system,and lowering the influent ammonia nitrogen concentration in the later stage,and through the oxygen control and subsequent adjustments,short-cut nitrification within the CRI system is expected.(2)In exploring the experiment of achieving nitrite nitrogen accumulation in the system with sodium chlorate as the maincontrol parameter,a certain range of sodium chlorate concentration(n<1.5 mmol)is favorable for the nitrosation reaction in the system,and the higher concentration of the chlorine sodium,the better the effect.However,when the sodiumchlorate concentration exceeds a certain limit(>1.5 mmol/L),the nitrification reaction in the system will be suppressed more,and the suppression to AOB and NOB in the system becomes more pronounced.At the same time,the nitrous acid accumulation rate can reach 50% under the condition of n=1.0 mmol·L-1,pH=8.0-8.5,normal temperature infour seasons,and non-controlled oxygen concentration,and it is stable in a short time.(3)In the experiment to explore the nitrite nitrogen accumulation in the system using dissolved oxygen and sodium chlorate as the main control parameters,we obtained: at normal temperature in the four seasons,the pH was 8.0-8.5,the oxygen in the system was 10.8% and a sodium chlorate concentration of 1.0 mmol/L.The CRI system achieved short-run nitrification with a stabilization time of more than 30 days.The ammonia nitrogen conversion rate and nitrous acid accumulation rate were all above 80%.The highest nitrite nitrogen accumulation rate was 92%.CRI system achieved short-cut nitrification with a maximum nitrite accumulation rate of 92%. |
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