Treatment Of High Ammonia Nitrogen Domestic Sewage By Three Step Series Of Constructed Rapid Infiltration System

Constructed Rapid Infiltration (CRI) system is applied to treating the conventional domestic sewage and micro-polluted river water etc. nowadays. However, there are few studies on high ammonia wastewater. This study researched the removal of pollutant,efficient of oxygen recovery,the problem of clog and effect of removing nitrogen by adding carbon resource by using CRI on high ammonia wastewater of students' living area in a university, the main achievements were as follows:The concentration COD and ammonia nitrogen could meet the standardⅠ—A of"Discharge standard of pollutants for municipal wastewater treatment plant(GB 18918-2002)", during the operation of three step series of constructed rapid infiltration system. The removal rates of COD, ammonia nitrogen and total nitrogen were 79.65%, 94.47% and 47.38% respectively. These rates were increased by 6%, 3% and 21%, compared with conventional CRI system respectively. The effect of removing total nitrogen results was improved significantly. COD and ammonia nitrogen were removed mainly in the first step, and total nitrogen was removed mainly in the third step. The total numbers of aerobic bacteria, nitrate oxidizing bacteria, nitrite oxidizing bacteria and denitrifying bacteria in three step series of constructed rapid infiltration system were higher than in conventional constructed rapid infiltration system significantly. The coefficient of the removal rate of COD and aerobic bacteria and the active biomass was high. The removal rate of ammonia nitrogen and ammonium oxidizing bacteria, nitrate oxidizing bacteria and nitrite oxidizing bacteria correlated significantly. The removal rate of total nitrogen and denitrifying bacteria, fungi and actinomycetes correlated significantly. The main reason for increase of removal rate of total nitrogen in this three step series of system was the increase of number of denitrifying bacteria. The constraint on the increase of the removal rate of total nitrogen was the low ratio of C / N. Concentration of DO increased gradually from first step to second step and then decreased in this three step series of system. It reached maximum at the end of the second step. The effect of oxygen recovery is remarkable. The interval of effluent in this three step series of system was reduced compared with conventional system. Infiltration speed of this three step series of system was 2 to 5 times than the conventional system. Moreover, the infiltration speed of this three step series was almost 10 times than the conventional system when the conventional CRI was clogged. The main reason for deferring of being clogged was the increase of speed of infiltration. The biofilm thickness is between 60 and 150μm calculated by geometric model.The results of additional carbon sources experiment showed that the effect was better when corncob was used. The effect of removal of nitrate nitrogen was the best when the temperature was around 25-33℃and pH was 7.5. The average removal rate of TN was 76.3% after adding corncob. The rate was increased by 30% compared with the system to which no carbon source was added. The effect of removal of TN was much better. The result of experiment on corncob with SEM showed that the surface was degraded by microorganism, some denitrifying bacterium, such as bacillus and coccus were found, and the main structure of corncob was not loose, which played a important role of a carrier.The best operating parameters under the experimental conditions in this three step series of system showed that hydraulic loading was 1.0m / d, ratio of flooding and drying was 1:5, and hydraulic loading cycle was 4h.