Preparation Of Corncob Carbon Composite Substrate And Its Application In Constructed Wetland

Crops are rich in a large amout of organic matter and carbon sources,but with the increasing output of agricultural waste,a large number of crop straws cannot be effectively disposed of,causing serious pollution to the environment.Adhering to the concept of waste-to curb-waste,this study considered using blochar prepared from comcob as main component to make wetland substrate and applied its rich carbon source properties to wastewater treatment in constructed wetland.With this regard,in this study,comcob charcoal-kaolin-white cement(CBKC)composite constructed werland was designed,set up and tested by compounding resultant CBKC as main substrate,which is hoped to provide sufficient earbon source for constructed wetlands The filler was used to explore its adsorption effect on P and its removal effect on pollutants in internittent flow constructed wetland.The main research results are as follows:(1)Experiments were carried out on the basis of using kaolin and white cement as separate binders.It was found that adding two binders at the same thime was more conducive to the mechanical strength of the new composite filler.Under the help of respouse surface methodology(RSM)trial,the formula ratio of corncob carbon:kaolin:white cement:water=3:7:4:7.5(unit:g)was finally selected to prepare the CBKC.This filler has better anti-dissolution degree,degree of molding,and compressive strength of 9.2 Kgf.(2)The P dynamic adsorption experiment under shaking apparatus was designed The Langmuir and Freundich equations were used for fitting the experimental results It shows that the saturated adsorption capacity of CBKC for P was 1.3941 mg/g under the solutions of the same pH and different initial P concentrations.While under the solutions of different pH and the fixed initial P concentration,the maximum P adsorption capacity of CBKC was 2.7943 mg/g.Weak acid conditions are more favorable for P adsorption by Biochar filler,and alkaline conditions are more favorable for P adsorption by CBKC.(3)An intermittent flow constructed wetland was built with CBKC as the substrate,and the influent and effluent concentrations of various pollutants were monitored during long-term operation.The results show that the removal rate of NH4+-N can be above 70%,while the removal rate of NO3--N can be maintained at about 99%.The removal rate of TN is above 90%,and the removal rate of COD can be maintained over 80%after 63 days operation.The effluent COD concentration in the whole operation stage is below 50 mg/L,which is in line with the "urban sewage treatment plant pollutant discharge standard(GB18918-2002)" level A standard.(4)The concentration of pollutants was monitored during the influent being introduced into the wetland.The results showed that the five pollutants were greatly degraded in a short period of time after entering the wetland.The concentration of NH4+-N,NO3--N,TN tends to be stable after being degraded in a large amount in a short time,and the COD concentration cannot reach the stability after being introduced in a short time.The fitting results of the Michaelis-Menten model equation showed that the maximum degradation rates of NH4+-N,NO3--N,TN,and COD increased with the increase of the experimental time,while the maximum degradation rates were 26.78 mg/(L·h),23.79 mg/(L·h),55.21 mg/(L·h),229.15 mg/(L·h),respectively.The maximum degradation rate of TP reached the maximum at the beginning of the experiment,which was 34.3461 mg/(L·h).