Development of a Novel Multi-soil Layer Constructed Wetland Treating Septic Tank Effluent with Emphasis on Organic and Ammonia Removals

摘要

A multi-soil layer vertical flow constructed wetland (MSL-VFCW) was developed as an innovative soil-based system for wastewater treatment. The goal of this research was to employ the MSL-VFCW, as a novel technique for treating septic tank effluent. These experimental units were operated for 3 months by continuous feeding with the septic tank effluent at the hydraulic retention time (HRT) of 10 h (MSL-VFCW1), 20 h (MSL-VFCW2), and 36 h (MSL-VFCW3), while a control unit was operated at on HRT of 20 h (VFCW4). The experimental results revealed that the highest treatment performance the MSL-VFCW units was found when operated at the HRT of 36 h which could obtain total chemical oxygen demand (TCOD), 5-day biological oxygen demand (BOD5), and NH3-N removal efficiencies greater than 94% (p 0.05). The multi-soil layers used in the MSL-VFCW unit were found to support microbial growth responsible for organic and NH3-N removals. The abundance and dominance of microbial clusters in the MSL-VFCW analyzed by using Miseq sequencing revealed that the percent abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in MSL layers were higher than the CW layer, resulting in higher in NH3-N removal efficiency. TCOD, BOD5, and NH3-N removals in the MSL-VFCW unit could be explained by first-order completely mixed model with k (20) values of 1.42, 1.54, and 10.33 day(-1), respectively, higher than the values reported for other constructed wetland system which suggested the applicability of the developed techniques for wastewater treatment.