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 m3 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.
Highlights
The bulk milk cooling tank, known as the expansion tank, is an equipment that receives and stores milk in bulk and provides its direct cooling (Melo & Reis, 2007), as required by law.These tanks, located mostly in rural areas, are subject to the same sanitation operations that occur in the dairy industry, consuming large volumes of water, chemicals and, generating an effluent with polluting potential
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
In the light of the above, the objective of this study was to evaluate the extractive capacity of elephant grass, Napier cv. (Pennisetum purpureum Schum) and Tifton 85 grass (Cynodon spp), when treated in different ways in HSSF-CWs filled with different types of substrates, in the treatment of a community bulk milk cooling tank (MTWW)
Summary
The bulk milk cooling tank, known as the expansion tank, is an equipment that receives and stores milk in bulk (without the use of brass) and provides its direct cooling (Melo & Reis, 2007), as required by law These tanks, located mostly in rural areas, are subject to the same sanitation operations that occur in the dairy industry, consuming large volumes of water, chemicals and, generating an effluent with polluting potential. In order to treat wastewater generated in a rural area that is difficult to access and does not have operators, it is necessary to use low cost installation and operation techniques and among these constructed wetlands systems stand out. The Constructed Wetlands Systems (CW S) can be a promising technical alternative, since it is a simple, low cost and easy operation and maintenance technology for the treatment of a wide variety of wastewater, such as domestic (Avelar et al, 2015), of dairy products (Matos et al, 2012; Mendonça et al, 2015), of swine farming (Sarmento et al, 2012; Fia et al, 2015), of textile industry (Saeed & Sun, 2013) and drugs industry (Zhang et al., 2014)
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