Study On Removal Effect And Related Parameters Of Nitrate Nitrogen Based On Rice Husk Sawdust Bioreactor

Pollutants such as fertilizers and pesticides produced through drainage from agricultural production activities,can enter water bodies like rivers and lakes,which is one of the important reasons for water pollution..It is of great significance to seek economical and effective measures for environmental protection and watershed management.The denitrification bioreactor is an ecological treatment measure with relative small size and good denitrification effect.In this paper,we through the laboratory test,the rice husk and wood chips were used as the filler to study the effect of bioreactor on the reduction of nitrate nitrogen in several mass ratios of 1:0,1:1,0:1,3:1,1:3.And then analyzed the factors affecting the performance of the reactor.According to the experimental results,A two-parameter prediction model is derived.The main research results obtained are as follows:(1)First,the reduction rate of nitrate in the non-flow state of the bioreactor was studied.The results showed that when the influent nitrate concentration is 10mg/L,the nitrate reduction rate of each reaction column reaches 80%or more under the 8h hydraulic retention time,while the nitrate reduction rate of each reaction column is between 70%and 80%under the 24h hydraulic retention time.The results show that denitrification is the main way to change nitrate-nitrogen in bioreactors.(2)Second,the pollutant reduction effects of five kinds of filler bioreactors under different influent concentrations(lmg/L,3.6mg/L,15mg/L)at different hydraulic retention times(4h,8h,12h)were studied.The study found that different fillers have significant effects on the reduction of nitrate nitrogen.The low-inflow concentration of the reaction column with high rice hull content has a good reduction effect while the high inflow concentration has a higher reduction of wood chips than the high content of rice husk.Moreover,the hydraulic retention time has a significant effect on the bioreactor reduction effect.When the influent concentration is 3.6mg/L,the 4h hydraulic retention time can reach a reduction rate of 80%or more;when the influent concentration is 15mg/L,it takes 8 hours.(3)In addition,both values of the pH and DO of the outflow were observed to be lower than the inflow value.The average pH of the outflow was 6.86,and the outflow DO value was lower than 0.55 mg/L.The T test found that the pH reduction was not significantly related to the filler,indicating that the decrease in pH may be related to the denitrifying flora.(4)Through data analysis and research,it was found that there was a release process of ammonia nitrogen and total phosphorus in rice husk and packing at the beginning of the experiment,and the effluent concentration was much higher than the inflow concentration;with the increase of the reactor operation time,the effluent concentration decreased exponentially,indicating that the initial release process was limited,and it would gradually disappear;(5)The hydraulic parameters of the reaction columns of the hydrodynamic test were measured.The results show that the packing density directly affects the porosity of the filling medium,and the actual porosity is highly correlated with the effective porosity.In the study of saturated hydraulic conductivity,it is found that the saturated hydraulic conductivity between the reaction columns at the proximal end of the inlet in the uniformly packed reaction column is increased compared with the saturated hydraulic conductivity at the distal end of the inlet.This indicates that the filling medium will change the hydraulic conductivity due to the flow of fine particles.It has also been observed that biological growth in the bioreactor affects the conductivity of the reactor.(6)The study also investigated the effect of dry-wet alternation on the bioreactor reduction effect.The results show that dry-wet alternating can increase the decomposition of organic matter and strengthen denitrification.The performance of the denitrification bioreactor can be enhanced by reasonable dry and wet alternation.In addition,the two parameter prediction model is obtained through statistical analysis,which provides a certain reliable theoretical basis for the popularization and application of bioreactor in China.