Research On The Removal Of Chloroacetanilide Herbicides In Water By Biological Activated Carbon Process

In recent years, the pollution of water source has gone from bad to worse, and the conventional treatment technologies are difficult to meet the high requirement of the new water quality standards. Since its significant advantages, activated carbon adsorption technology has become one of the most common and effective treatment techniques in the world. After long time operation, the saturated activited carbon should be regenerated or changed, which will increase cost. However, the biological activated carbon (BAC)can improve the removal of pollutants by using both the absorbility of carbon absorption and biodegradation ability of microorganism which adhere on the surface of activited carbon.This removal of chloroacetanilides herbicides by BAC was researched in this study. Chloroacetanilides herbicides were absorped by columnar actiyited carbon, coconut shell actiyited carbon and fiber actiyited carbon respectively. Then the adsorption isotherms were analysized by using Langmuir model and Freundrich model. The experiments were also conducted to plot the adsorption rate curves and break curves of these activated carbon; Start-up of activated carbon in a dynamic flow was discussed. Several water indexes includes CODMn, UV254, ammonia nitrogen, nitrite nitrogen, DOC and AOC were monitored during the start-up process. The effect of current rate, temperature and pH value on the removal of chloroacetanilides herbicides were also discussed which based on the BAC technologies, and the optimization parameters were given.According to the results of the research. All the adsorption isotherms of chloroacetanilides herbicides adsorbed by the activated carbon were well described by Freundlish model. The results shows that fiber actiyited carbon has best adsorbility on chloroacetanilides herbicides, the adsorbility of columnar activited carbon is lower, while the adsorbility of coconut shell activited carbon is the lowest. But all these three activated carbon reached the adsorption equilibrium at 100min, 130min and 150min respectively, While the break through time of these three activated carbon are 20h, 26h and 34h.The BAC treament technology achieves stability after operation for 53 days. After long time operation. All monitored water quality indexes became stable. The removal of CODMn, UV254, ammonia nitrogen, nitrite nitrogen and DOC were 30.2%, 25.2%, 37.2%, 35.8% and 22.7% respectively. By then, some brown biofilm was obsearvied on the surface of activated carbon. Therefore the biofilm culturing was sucessful which was proved by the SEM experiments. The results show that dense zoogloea adhered on the surface of activated carbon.Optimized parameters of BAC treatment process for the removal of chloroacetanilides herbicides were observed: velocity ranged form 50 to 67mL/min, temperature ranged form 25 to 29℃, pH current rate ranged form 5.5 to 7.5, the removal ratio of the common index of water standard is above 20%, while the average removal ratios of chloroacetanilides herbicides are higher than 40%.