Effect of hydraulic retention time and aeration on performance of horizontal subsurface flow constructed wetland in phenol removal

Constructed wetlands and conventional treatment methods have a same duty in wastewater treatment، but they have different methods and mechanisms. The aim of this study was to investigate the removal of phenol from synthetic wastewater using horizontal sub-surface flow constructed wetland and the aeration and hydraulic retention time effects on phenol removal efficiency. This study was an interventional study that was carried out on a laboratory scale in horizontal sub-surface flow constructed wetland. In order to determine the effect of aeration on the efficiency of phenol removal, ، one reactor was aerated and another one was non-aerated. Pumice was used as a media. The wetlands were planted by Phragmatis australis. The results showed that phenol degradation in both aerated and non-aerated wetland was influenced by organic loading rate and hydraulic retention time. It was also found that the removal of phenol was completely accomplished in both aerated and non-aerated wetlands. This is while the phenol removal rate is higher in aerated wetland, ، and in order to achieve the same results, ، the hydraulic retention time in non-aerated reactor should be about twice as high as the aerated one.  Horizontal sub-surface flow constructed wetland has a high efficiency in phenol removal. Therefore, if the conditions of operation especially hydraulic retention time are optimized، it can be applied as an effective system for phenol removal from wastewater.