Developing horizontal subsurface flow constructed wetland using pumice and Chrysopogon zizanioides for tannery wastewater treatment

Abstract Background High-strength wastewater defined by elevated levels of hazardous pollutants measured in BOD, heavy metals, nutrients and other toxic substances. This kind discharged to water body without treatment from different industrial sectors that adversely affects aquatic environment downstream consumers. The general objective this study is investigate efficient substrate with selected plant type for constructed wetland remove tannery wastewater. was conducted at Modjo town, PLC. Plug flow experimental design carried out. (Pumice) collected around the area chemical characteristics were determined. Chrysopogon zizanioides planted grown 5 months before running treatment. composite introduced leather industry, Ethiopia. physicochemical analysis sample done after four hydraulic retention time. Results Characterization untreated revealed mean concentration BOD 5, COD, TSS, PO 4 -P, TP, NO 3 -N, TN total chromium 1641 ± 373.6, 6953.33 339.4, 1868 863.1, 88.06 40.8, 144.53 20.8, 116.66 26.6, 650.33 93.6 18.33 6.7 mg/l respectively beyond permissible limits. maximum removal efficiency pumice bed HRT 7and 9 days (96.42%, 96.30%), COD 7 (96.76%, 96.91%), -N (99.99%, 99.68%), (98.67%, 99.00%), -P (96.97%,100%), TP (94.79%, 96.17%) Chromium (98.36%, 98.91%) respectively. Whereas, gravel used as a control subject similar condition showed lower performance. result between tested their significance difference using two t-test statistics. Based on test statistics, perform better than significantly 95% confidence interval, p-value = 0.01. Conclusion Pumice have potential ability horizontal subsurface wetlands.