Performance of Decentralized Vertical Flow Constructed Wetlands for Reuse in Agricultural Irrigation in Jordan: Enhancing Nitrogen Removal

Abstract

AbstractThis study shows the performance of two vertical flow constructed wetlands (VFCW) at the Fuhais research facility for decentralized wastewater treatment in Jordan, considering category-A in the Jordanian Standards for reuse in irrigation (JS 893/2006). Recirculating and two-stage VFCW designs were monitored for 3 years. The recirculating VFCW has shown high removal efficiency of COD, TSS, and BOD5 over the study period, conforming to the JS (Category A). Whereas, the Total Nitrogen (TN) and Nitrate (NO3−) removals were limited (55 and 44 mg/L) over the baseline monitoring, conforming to the JS category-B (TN: 70 mg/L and NO3-N: 45 mg/L). Therefore, the system was modified into attached growth recirculation tank (installing electric conduit pipes as plastic media). TN concentration was effectively reduced to 40 mg/L, conforming to the JS category-A (TN: 45 mg/L), and NO3−-N concentration to 37 mg/L, conforming to the JS category-B. The two-stage VFCW has shown high removal efficiency of COD, TSS, and BOD5, conforming to the JS (Category-A). TN and NO3−-N concentrations were limited (55 and 44 mg/L), conforming to the JS Category-B, due to insufficiency of carbon source to promote denitrification (high BOD5 removal by the first filter). Thus, the system was modified with raw wastewater step-feeding application to the intermediate pump shaft before the second stage filter. The results of operational modification showed a small significant improvement in TN removal (p = 0.005); TN and NO3−-N concentrations were reduced to 52 and 50 mg/L, respectively, conforming to the JS (Category-B).KeywordsArid climateVertical flow constructed wetlandRecirculatingNitrogenNitrificationDenitrificationReuseJordan