Research On Ecological And Biological Treatment Of Trimethoprim In Water

In this paper,the removal of trimethoprim（TMP）in waste-water by Alligator weed activated carbon（AWAC）and activated sludge were studied.The physical properties of AWAC were determined by scanning electron microscope（SEM）,BET method,Fourier Transform Infrared（FTIR）.The effects of the initial concentration of solution,the addition amount of activated carbon,the shock time,pH and temperature on the removal effect of TMP were investigated in the single-factor test,and the adsorption kinetics,adsorption isotherm and adsorption thermodynamics were analyzed.In the SBR degradation TMP test,the overall operating performance of TMP on SBR reactor was investigated,such as average chemical oxygen demand（COD）,ammonia nitrogen（NH₄⁺-N）,total phosphorus（TP）and TMP removal effect,the change of extracellular polymer（EPS）production and microbial community structure change.The specific research results are as follows:（1）the SEM results showed that the AWAC had a rough surface and pore structure is developed.The specific surface area of activated carbon measured by BET method was relatively high,reaching 752.6m2/g,which was conducive to improving the adsorption capacity of AWAC and the average pore diameter was 5.80 nm.What’s more,AWAC was a combination of micropore and mesoporous.The FTIR results showed that some functional groups are present,such as phenolic hydroxyl groups,carboxyl groups,ester groups,etc.,which are closely related to the adsorption properties and the catalytic ability of the AWAC surface.（2）in the adsorption test,the maximum adsorption of the AWAC to TMP was reached 125 mg/g,and the removal rate was up to 99%when the concentration of TMP was 60mg/L,and the addition amount of activated carbon was 2.0 g/L.Taking the removal rate and adsorption amount of TMP into consideration,the concentration of TMP=60mg/L,the shock time=1.0g/L,the AWAC dosage=1.0g/L,the temperature=298K,and the pH was the initial value of TMP solution were selected in the subsequent test.Studies on adsorption kinetics and isotherm showed that the adsorption process conforms to pseudo-second-order kinetics（R²=1）and Freundlich model（R²=0.9950）,indicating that the adsorption process was a chemical adsorption and multi-layer adsorption process.Thermodynamic study showed that the reaction process was spontaneous and exothermic.（3）in SBR process,the removal efficiency of COD,NH₄⁺-N and TP was 88.6%+0.56%,90.47%+0.29%and 64.25%+/0.29%,respectively.The removal rate of TMP finally stabilized at about 70%.With the increase of TMP concentration,the content of protein（PN）and polysaccharide（PS）increased,which can be explained as that microorganisms protect themselves by secreting EPS under stimulated conditions.Three-dimensional fluorescence spectroscopy（EEM）showed that EPS contained PN and soluble microbial by-products and humus organic matter.（4）In the Alpha diversity analysis,the abundance level curve indicates that the number of OTU in the initial sample is the highest and the evenness of community composition is the highest.In the Beta diversity analysis,the contribution rate of PC1and PC2 principal components to the difference in bacterial community was 65.69%and 31.39%,respectively.In other words,the community structure of early stage and late stage was significantly different,indicating that TMP acclimation could effectively distinguish microbial community.Dynamic change of the microbial community of Zoogloea,Paracoccus and Pseudomonas were advantages,including Paracoccus was can carry on the denitrification through denitrification,Pseudomonas genus had a strong ability to break down organic matter.Gordonia was a biodegradable bacterium.Methylobacillus was a strict aerobic bacterium.The abundance of these genera was low in the early stage and high in the late stage,indicating that TMP was conducive to the enrichment of these genera.