Abstract
In this study, the physicochemical and biological contributions of different macrophytes in horizontal sub-surface flow constructed wetlands (HSSF-CWs) to treat low-strength municipal wastewater operated at high hydraulic loads under a sub-tropical climatic region is investigated. Out of the four identical beds, three were planted with locally available macrophytes (P. australis, Sagittaria, and Iris), whereas one bed was kept as a control. The beds were filled with media and operated in parallel continuously for eight months, with increasing the surface loading rate (SLR) from 0.19 to 2.78 m day−1. The results indicate that the planted beds performed significantly (p < 0.01) better to remove TSS (70% to 78%), BOD5 (66% to 77%), COD (59% to 75%), NO3-N (56% to 64%), NH4-N (41% to 69%), TN (36% to 41%), and TP (44% to 61%) as compared to the unplanted bed for the same parameters (48%, 39%, 40%, 33%, 18%, 20%, and 29%, respectively). The presence of macrophytes in HSSF-CWs was found to be highly significant. The average relative growth rate (RGR) was observed in the order of P. australis (0.0086 day−1) > Sagittaria (0.0061 day−1) > Iris (0.0059 day−1). When compared to the performances of the species used, Sagittaria and P. australis produced better results than Iris. The investigations on biomass showed that Sagittaria yielded higher production, followed by P. australis and Iris. The proportions of uptake by the macrophytes were found to be 9.3%, 6.3%, and 3.9% of mass N removal, and 7.6%, 5.1%, and 4.4% of mass p removal in Sagittaria, P. australis, and Iris, respectively. This study contributes to the effective response to the environment, which validates a major role of macrophytes and their disparate response to pollutant removal processes by different species from municipal wastewater through HSSF-CWs.
Highlights
Natural processes have always been recognized as one of the best methods to clean the water flow through rivers, lakes, streams, and wetlands in a more cost-effective and sustainable way
The loading rate to the beds ranged to 28.5–910.9 g total suspended solids (TSS) m−2 day−1, 7.2–190.6 g BOD5 m−2 day−1, 18.5–438.2 g chemical oxygen demand (COD) m−2 day−1, 0.2–7.1 g NO3 -N m−2 day−1, 1.5–65.6 g NH4 -N m−2 day−1, 3.3–100.0 g total nitrogen (TN) m−2 day−1, and 0.4–7.1 g total phosphorus (TP) m−2 day−1
The comparison among the species demonstrated a significant difference (p < 0.05), where P. australis and Sagittaria exhibited better removal compared to Iris, which may be due to the large number of adventitious rooted biomass
Summary
Natural processes have always been recognized as one of the best methods to clean the water flow through rivers, lakes, streams, and wetlands in a more cost-effective and sustainable way. The HSSF-CWs system is one of the most common types of SSF wetland systems used in many parts of the world In this system, wastewater is maintained at a constant depth and flows horizontally below the surface along the length through granular medium, macrophyte roots, and rhizomes [11]. Iris in HSSF-CWs to treat low-strength municipal wastewater operated at high loading rates in sub-tropical climatic conditions, which prevail in the northern plains of India. Recycling 2022, 7, 8 and Iris in HSSF-CWs to treat low-strength municipal wastewater operated at high load of 16 ing rates in sub-tropical climatic conditions, which prevail in the northern plains of India
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