Two-step system consisting of novel vertical flow and free water surface constructed wetland for effective sewage treatment and reuse

[Display omitted] •A two-step constructed wetland system for sewage treatment and reuse was studied.•Excellent removal efficiencies of TSS (76%), BOD5 (74%), and NH4-N (90%) were achieved.•Hydraulic loading significantly affected the removal of NH4-N, TSS, and BOD5.•Optimal HLR of 0.04–0.06 m/d were suitable and practical for water recycling. This study developed a unique system by combining the novel vertical flow (NVF) using expanded clay (ExC) and free flow surface constructed wetland (FWS) for dormitory sewage purification and reuse. The NVF tank consisted of filter layers of ExC, sandy soil, sand, and gravel. The FWS consisted of sandy soil substrate and was installed after the NVF. Colocasia esculenta and Dracaena sanderiana was planted in NVF and FWS, respectively. The treatment system was operated and tested for more than 21 weeks by increasing the hydraulic loading rate (HLR) from 0.02 m/d to 0.12 m/d. The results demonstrated that effluents in the system changed proportionally to the HLRs, except for nitrate nitrogen. Furthermore, the maximum removal efficiencies for TSS, BOD5, NH4-N, and Tcol were 76 ± 13%, 74 ± 11%, 90 ± 3%, and 59 ± 18% (0.37 ± 0.19 log10MPN/100 mL), respectively. At HLRs of 0.04–0.06 m/d, the treatment system satisfied the limits of agriculture irrigation.