Integrated constructed wetland systems employing alum sludge and oyster shells as filter media for P removal

This research aimed to investigate the technical feasibility of integrated constructed wetland system consisting of a pre-filter unit and a constructed wetland (CW), in series; packed with alum sludge (AS) and oyster shells (OS) as the filter media, respectively, for nitrogen and phosphorus removal from domestic wastewater. Based on the 240 days of operation from January to August 2007, this integrated system was highly effective in removing BOD, N, P and TSS compounds which were found to be 89.5%, 68.8%, 99.4% and 89.9%, respectively. After this period, the integrated system was modified as the CW and post-filter unit, in series. The post-filter of this modified integrated system was operated during 60 days with cover for light shield and during another 60 days with no cover from September to December 2007. The treatment performance of modified integrated system was effective in removing BOD5, N, P and TSS compounds which were found to be 91.4%, 86.8%, 99.7% and 73%, respectively, during which the post-filter had operated with no cover. To simulate high rainfall conditions, the integrated system was tested under hydraulic shock loading at the overall hydraulic retention time of 0.7 day during one day. This hydraulic shock loading conditions made BOD5, TN, TSS concentration increase, but made no effect on P concentration. Integrated system combined a pre-filter and a CW unit or a CW unit followed by a post-filter is recommended for use in domestic wastewater which should result in high treatment performance, especially on P removal.