Addition of Corn Cob in the Free Drainage Zone of Partially Saturated Vertical Wetlands Planted with I. sibirica for Total Nitrogen Removal—A Pilot-Scale Study

Abstract

The aim of this 15-month study was to evaluate and compare two partially saturated (PS) vertical flow (VF) wetlands for total nitrogen (TN) removal. The PS VF wetlands, evaluated in duplicate, were added with corncob (CC) in two different heights of the free-drainage zone (FDZ). The FDZ had a height of 40 cm and the saturated zone (SZ) had a height of 30 cm. The configuration of the system I (SI) was a 20 cm-corncob bed above the SZ followed by a 20 cm-tezontle bed; in system II (SII) the order of the beds were inverted. The SZ was added with tezontle with a size of 1−2 cm. Weekly measurements of water quality parameters including oxygen demand (BOD 5 ), chemical oxygen demand (COD), color, total suspended solids (TSS), organic nitrogen (Org-N), ammonium (NH 4 + ), nitrate (NO 3 − ) and nitrite (NO 2 − ), were taken in the influent and effluents, and interfaces (nitrate and nitrite). Measurements of pH, dissolved oxygen (DO) and oxidation-reduction potential (ORP) were taken in the SZ. The addition of CC in the FDZ did not interfere with the capacity of the PS VF wetlands for BOD 5 , COD, TSS and true color removal, reaching mass removal efficiencies of 91.9% and 92.2%, 66.6% and 75%, 89.8% and 92%, 63.3% and 66.0%, for SI and SII, respectively; without significant difference between the systems (p > 0.05). The CC in the FDZ neither interfered with the PS VF wetlands nitrification capacity. The removal of TN was similar in SI and SII (p > 0.05), attaining average mass removal efficiencies of 68.2% and 66.0%, respectively. These efficiencies were not sufficiently high due to the limited denitrification process in the SZ as a result of the absence of biodegradable carbon, generated and consumed in the FDZ.

Effects of Partial Saturation on Nitrogen Removal and Bacterial Community in Vertical-Flow Constructed Wetlands

“…In fact, vertical ow constructed wetlands with saturated layer (SVF-CW) had higher NTK removal than unsaturated bed (UVF-CW) (Table 4). This higher removal e ciency resulted from the development of denitri cation process in saturated layer (Pelissari et al 2017;Del Toro et al 2019).…”

Treatment Wetlands in Mexico for Control of Wastewater Contaminants: A Review of Experiences during the Last Twenty-Two Years

“…According to the data reviewed, 67 published studies on CWs performance were found and grouped according to their size (Figure 3a), 18% were studies in microcosms or laboratory level [33][34][35][36][37][38][39][40][41][42][43][44], 30% were CWs in mesocosms size [5,[45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63] and, 25% were CWs in Pilot models [64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80], while 27% were CWs operating in ful...…”

“…Such removals of BOD and COD comply with the established limits by Mexican Norms (NOM-001-SEMARNAT-2021), but compounds of N of P perhaps need coupling of new strategies to improve their elimination. Some studies have reported better nitrogen eliminations adding internal solid source of organic carbon in order to distinguish the role of nitrification-denitrification and Anammox in the nitrogen removal process [38,44,81].…”

“…Generally, the higher use of subsurface CW versus FWS is related with most optimum performance in pollutant removals in organic compounds, with benefit given by the filter material media. Between vertical and horizontal flow of CWs, the first has been the least used as the water needs to be pumped intermittently to program the discharge (electric cost) [37][38][39][40].…”