Influence of Substrate and Species Arrangement of Cultivated Grasses on the Efficiency of Horizontal Subsurface Flow Constructed Wetlands

Abstract

We aimed to evaluate the efficiency of six different horizontal subsurface flow constructed wetlands (HSSF-CWs), with different substrates (gravel and crushed PET bottles), which also varied in relation to the presence and arrangement of plant species (elephant grass and Tifton 85 bermudagrass) in the removal of pollutants from a bulk milk cooling tank (MTWW). Each bed was fed at a flow rate of 0.18 m 3 d -1 and average organic load rate (OLR) of 318 kg ha -1 d -1 of BOD5, with hydraulic detention time (HRT) of 1.84 days in the gravel-filled HSSF-CWs (CWS-G) and 2.97 days in the PET-filled HSSF-CWs (CWs-P). The CWs-P were as efficient as the CWs-G in the removal of BOD5, COD, Total-P, and K-Total, being in some cases even more effective (turbidity, TS, TSS and Na). The gravel, on the other hand, provided greater removals of Total-N from the MTWW. In the non-cultivated CWs and those cultivated with elephant grass, in its first half and Tifton 85 grass in its second half, there were higher average efficiencies in COD and TSS removal sand, in the latter, the highest average removal of Total-N.

Efficiency of horizontal subsurface flow-constructed wetlands considering different support materials and the cultivation positions of plant species

“…In order to investigate possible efficiency loss of pollutants' removal from the system, the operation was divided into periods: Period I (data generated from April to December 2015 in the experiment conducted by Saraiva et al (2018)) and Period II (monitoring of the system from March 11, 2016 until December 15, 2016), with the application of WWMT. Each of these phases was performed by a different researcher, with different research objectives.…”

“…To compare the removal efficiencies between Period I and Period II, the "t" test was used for independent data at 5% significance. Table 1 shows the mean values of the surface application rates during experimental monitoring of the systems, Period I (April to December 2015) (Saraiva et al, 2018) and Period II, the period of this study (April to December 2016). As observed, only the surface loading rate of TP differed significantly according to the t-test.…”

“…On the other hand, traditional filter media often clog quickly due to either the size of their pores or by wear during the operational period (Pedescoll et al, 2009). Thus, the use of materials that are inert and easy to acquire may be an interesting solution in terms of the associated costs (purchase and replacement) (Saraiva et al, 2018). In this context, alternative Rev.…”

“…Furthermore, this material is less subject to wear resulting from acid attack in the HSSF-CWs, which permits for longer system operational times without indication of clogging problems in the porous media. Saraiva et al (2018) observed BOD5 removal efficiencies ranging from 82 to 87% and from 67 to 70% for total solids removal when using crushed PET bottles for the treatment of wastewater from a milk cooling tank (WWMT).…”

Extraction Capacity of Grasses Grown in Constructed Wetland Systems Using Different Arrangements and Substrates

“…Button et al (2016) observed an influence of the cultivation of Engenharia Agrícola, Jaboticabal, v.39, n.5, p.668-675, sep./oct. 2019 intercropping species (two by two) on the microbial community in CWs, and thus there could be an effect on the unit performance, which was demonstrated by Saraiva et al (2018). Consequently, there may be a higher extraction capacity for species cultivated under this condition.…”