Industrial Wastewater Treatment Efficiency of Mixed Substrate (Pumice and Scoria) in Horizontal Subsurface Flow Constructed Wetland: Comparative Experimental Study Design

The discharge of untreated wastewater causes serious public and environmental health problems. Hence, the present study aimed to evaluate the combined adsorption potential of the two substrates (Pumice and Scoria) in a horizontal subsurface flow constructed wetland. The substrates were collected from the Ethiopian rift belt. Composite samples from tannery wastewater before and after treatment of four different retention times (RT) were collected and analyzed. Chrysopogon zizanioides was planted in one of the mixed substrate beds and grown for 5 months before running wastewater for the treatment. The maximum removal efficiency of the planted bed revealed that BOD 5 at RT 7 days effluent concentration of 59.33 mg/L (96.38% removal), COD at RT 7 days 129.33 mg/L (98.14% removal), NO 3 -N at RT 7 days 0.28 mg/L (99.76% removal), TN 27.33 mg/L (95.80% removal), PO 4 -P RT 9 days 0.01 mg/L (99.9% removal), TP at RT 7 days 6 mg/L (95% removal), Sulfide at RT 7 days 0.27 mg/L (99.9% removal), sulfate at RT 9 days 87.9 mg/L (91.8% removal), and total Chromium at RT 7 days 0.1 mg/L (99.45% removal) respectively. The efficiency of the study and control beds was tested by a Two-Sample t-Test. The result showed that there was a significant difference at a 95% confidence interval, p-value = .002. Hence, the mixed substrate with plants performs better than the unplanted one, which means it can be effective for the treatment of high-strength industrial wastewater using horizontal subsurface flow constructed wetland.