A Comparative Study of Five Horizontal Subsurface Flow Constructed Wetlands using Different Plant Species for Domestic Wastewater Treatment

Abstract

This project studied domestic wastewater treatment by horizontal subsurface flow (HSSF) constructed wetlands (CW) and compared the effect of four different plant species on the operating conditions, dissolved oxygen (DO), and redox potential (ORP), and their efficiency on pollutants removal. Five HSSF CWs were fed for 10 months with low loaded synthetic domestic wastewater, using theoretical hydraulic residence time of 7.6 days. The plant species under study were the following: Phragmites australis (CW1), Lythrum salicaria (CW3), Cladium mariscus (CW4) and Iris pseudacorus (CW5). CW2 was not planted and this was used as control. Qualitative measurements determined a greater growth of Lythrum salicaria and Iris pseudacorus than the others. Dissolved oxygen concentrations were very low in the entire bulk liquid of all the CWs. Also ORP values were very similar in all wetlands, dealing with facultative anaerobic environments. All planted wetlands improved pollutants removal compared with the unplanted control wetland. The performances in terms of COD, TN, TP and SO4(2-) removal obtained by the different CWs were in the ranges 80-90%, 35-55%, 15-40% and 45-60% respectively. Lythrum salicaria and Iris pseudacorus, which exhibited greater growth, were always the most efficient species that improved not only nutrients plant uptake but also other microbial removal processes probably due to a higher aeration potential, such as nitrification or aerobic respiration. Sulphate reduction was the most important mechanism for COD removal. Cladium mariscus, an autochthonous plant that grows in the south-central Iberian Peninsula, was less efficient than Lythrum salicaria and Iris pseudacorus, but improved the unplanted wetland wastewater efficiency.

Influence of polyphenols on low-loaded synthetic winery wastewater constructed wetland treatment with different plant speciesA paper submitted to the Journal of Environmental Engineering and Science.

“…Figure 2a shows that ORP increase was favoured by the presence of plants (HSSF-CWs 2, 4, and 5), and the level of increase could be related to the aeration potential of these species. This hypothesis was also supported by previous work (De Lucas et al 2007), which used the same plants but treated domestic wastewater, where a higher aeration potential of these plants was apparently also detected. Figure 2b shows ORP values using ww2 (with the polyphenol addition), and the ORP profiles were similar to those observed for ww1, however, in the case of ww2, no differences between plants were detected.…”

“…The experimental pilot plant had been previously treating domestic wastewater for one year (Villaseñor 2007). All the wetlands were continuously fed using ww1 from August to November 2004, and using ww2 from December to June 2005, with a constant flow of 50 L d -1 to maintain a theoret- 1.…”

“…Only a qualitative analysis of the different species' growths was performed. The vegetation at the beginning of the experiment was already developed because the wetlands were treating simulated domestic wastewater for more than one year as part of a previous research project (De Lucas et al 2007). It was observed during the whole experimental period (August through June) that the species with higher growth were, in this order, Iris pseudacorus, Lithrum salicaria, Phragmites australis, and Cladium mariscus.…”

Comparison of vertical-flow constructed wetlands with and without supplementary aeration treating decentralized domestic wastewater

“…Emails: zliand@uwasa.fi, liandongzhu@gmail.com, zli@hubu.edu.cn Constructed wetland (CW) technologies are natural treatment systems filled with substrate materials like sands or gravels, and planted with vegetation [11]. They are proven to be cost-effective, low maintenance and ecofriendly systems [12], especially for the treatment of urban sewages from small communities and several kinds of industrial wastewaters [13,14]. It is well known that the treatment mechanisms in CWs are complex processes that may happen sequentially or simultaneously [15], involving microbial degradation, plant uptake, sorption, sedimentation, filtration and precipitation [16,17].…”

Comparison of the Treatment Performances of High-strength Wastewater in Vertical Subsurface Flow Constructed Wetlands Planted with Acorus calamus and Lythrum salicaria

“…Other studies also show that this species had good capacity for remove P compared to other wetland plant. 19) Chemical adsorption is usually considered the main mechanism for P removal in CWs. 20) We did not quantify the amount of P removed by plant uptake in this study, but we assume that a large fraction of the P that was removed was through binding to the bed substrate.…”