Research On Cultivation And Immobilization Of Nitrifying Activated Sludge In Low Temperature

Temperature is one of the important factors on nitrification.At ordinary temperature20℃to30℃, through treating by municipal wastewater treatment plant, the removal rate of ammonia can reach80%-90%.However, when winter comes, the temperature drops rapidly.Then the aeration tank can not keep a high temperature for nitrification.Most wastewater treatment plants solve this problem by steam heating.But this method can expend a lot of energy, which is not reasonable in economics and accepted by most wastewater treatment plants.According to statistics of most wastewater treatment plants in central regions of Shanxi Province, the temperature of wastewater remains at13℃to14℃, at which temperature the nitrifying rate is very slow and the removal efficiency of ammonia nitrogen is very poor.For wastewater treatment plants which have a bad ammonia removal effect or just start up in the winter, ifinoculating low temperature-resistant nitrobacteria to aeration tank, the problem can be alleviated efficiently.In order to get low temperature-resistant nitrobacteria, the experiment cultivated activated sludge through three stages: temperature25℃, temperature16～17℃and temperature13～14℃and the proper acclimation conditions were researched. And then the mature nitrifying sludge was made into embedded immobilized microorganisms gel pellets by three immobilized methods and the best immobilized method was sodium adding diatomite method. At last, the gel pellets were applied in SBR process and the reinforcement effect of gel pellets was discussed. The results showed that:1、Through acclimating for about two months, the removal rate of activated sludge could reach89%at13℃to14℃.The proper conditions of activated sludge acclimation was DO (2mg/L), pH (6.7～7.2), ammonia concentration (300mg/L) and mixed liquid chemical oxygen demand (80mg/L)2、Through comparing three immobilized methods:sodium alginate adding activated carbon, sodium adding Poli Vingl Alcohol (PVA) and sodium adding diatomite. The results showed that gel pellets madefrom sodium adding diatomites method could get a better ammonia removal effect.And the experiments found thatthrough immobilization, the ammonia removal effect could get improved and the removal rate of ammonia wasabout10%higher than that of suspended sludge.3、Applying immobilized gel pellets to treat municipal wastewater, When immobilized gel pellets were thrown into SBR reactor simply, the removel rate of ammonia could reach over80%. And when immobilized gel pellets were thrown into the SBR reactor with activated sludge, the ammonia removal effect of SBR process could get strengthened and the removal rate of ammonia could raise12%～20%with the increase of gel pelletsdosage.