Treatment of municipal wastewater by vertical subsurface flow constructed wetland: Data collection on removal efficiency using Phragmites Australis and Cyperus Papyrus

Abstract The data of this document highlights a comparative analysis between the Phragmites Australis and Cyperus Papyrus planted in vertical subsurface flow constructed wetland (VSSFCW) independently implemented at pilot scale for the treatment of domestic wastewater. At the exit of the primary lagoon a pipe was installed to feed a constant flow of 0.6 m3/day to each of the two constructed wetlands. Each unit had a retention time of 1.12 days and a hydraulic load rate of 0.2 m/day. To evaluate the efficiency of the treatment, physical, chemical and biological parameters were monitored for three consecutive months. Water samples in the influent and effluent of each experimental wetland were analyzed. At the end of the monitoring, Cyperus Papyrus had a better removal of total phosphorus (50%), ammoniacal nitrogen (69.69%), biochemical oxygen demand (69.87%), chemical oxygen demand (80.69%), total coliforms (98.08%) and fecal coliforms (95.61%). Meanwhile, Phragmites Australis eliminated total solids better (62.85%). These data may be useful for comparative purposes on domestic wastewater treatment using Phragmites Australis and Cyperus Papyrus planted in VSSFCW.


a b s t r a c t
The data of this document highlights a comparative analysis between the Phragmites Australis and Cyperus Papyrus planted in vertical subsurface flow constructed wetland (VSS-FCW) independently implemented at pilot scale for the treatment of domestic wastewater. At the exit of the primary lagoon a pipe was installed to feed a constant flow of 0.6 m 3 /day to each of the two constructed wetlands. Each unit had a retention time of 1.12 days and a hydraulic load rate of 0.2 m/day. To evaluate the efficiency of the treatment, physical, chemical and biological parameters were monitored for three consecutive months. Water samples in the influent and effluent of each experimental wetland were analyzed. At the end of the monitoring, Cyperus Papyrus had a better removal of total phosphorus (50%), ammoniacal nitrogen (69.69%), biochemical oxygen demand (69.87%), chemical oxygen demand (80.69%), total coliforms (98.08%) and fecal coliforms (95.61%). Meanwhile, Phragmites Australis eliminated total solids better (62.85%). These data may be useful for comparative purposes on domestic wastewater treatment using Phragmites Australis and Cyperus Papyrus planted in VSSFCW.  Value of the data • The data presented are used to analyze the treatment capacity of domestic wastewater using two species of vegetation (Phragmites Australis and Cyperus Papyrus) in vertical subsurface flow constructed wetland (VSSFCW). • The physical-chemical and microbiological parameters data serve to provide a clear picture of the water quality that could be obtained when using Phragmites Australis and Cyperus Papyrus in VSSFCW, therefore, these data could be useful for communities or cities that have domestic wastewater with characteristics similar to this research. • To make known that unconventional treatments in small population centers or in rural areas, is possible using VSSFCW. • To run new experiments using these data as initial information, researchers can recognize the efficiency of Phragmites Australis and Cyperus Papyrus to develop a new set of experiments using other vegetation species and compare them with these. • These data allow choosing a suitable vegetation for a VSSFCW that you want to implement in the treatment of domestic wastewater.

Data description
The data presented in this article refers to the quality of the treated water in two vertical subsurface flow constructed wetland (VSSFCW). Phragmites Australis was planted in a first wetland and Cyperus Papyrus was planted in a second wetland. The data obtained during the tests included parameters such as: pH, total suspended solids (TSS), electrical conductivity (CE), alkalinity (Alk), ammoniacal nitrogen (NH 3 -N), nitrate (NO 3 -N), total phosphorus (TP), biochemical oxygen demand (BOD 5 ), chemical oxygen demand (COD), total coliforms (TC) and fecal coliforms (FC). The data obtained for the physicochemical and microbiological parameters of the wastewater (influent) and treated water in the VSSFCW (effluent) are shown in Table 1 (Supplemental File 1). Constructed wetlands are an emerging treatment technique that can improve the treatment of domestic wastewater [1] . The removal of contaminants is better in the presence of vegetation [2] , which improves the removal efficiency of COD, BOD, TSS, NH 3 -N, TP, FC [3 , 4] . Based on the aforementioned, this research compared the efficiency between Phragmites Australis and Cyperus Papyrus planted in artificial underground vertical flow wetlands (VSSFCW) on a pilot scale. Summary data on water quality efficiency obtained for Phragmites Australis and Cyperus Papyrus are provided in Table 2 (Supplemental File 2).
Data presented in Table 2 refer to the average removal efficiency of TSS, BOD 5 , COD, NH 3 -N, TP, TC, FC obtained during the seven tests.

Location
The VSSFCWs were implemented together with the Wastewater Treatment Plant in the city of Santa Isabel, Ecuador (Longitude 79.313732 °W and Latitude 3.298460 °S). This plant has a primary treatment through a lagoon. The effluent from this lagoon was conducted to the two VSSFCW, one for each species, Phragmites Australis and Cyperus Papyrus. Each wetland operated independently but with a continuous water flow of 0.6 m 3 day −1 .

Design and constructed of the VSSFWCs
To determine the size of the VSSFWCs, the methodology cited by García [7] was used. An initial BOD 5 concentration of 100 mg L −1 (influent) and the desired BOD 5 concentration of 10 mg L −1 (effluent) was considered; a water residence time of 1.12 days was determined for the system to operate continuously [5 , 6] .
A substrate depth of 0.7 m was considered, the deeper the substrate, the greater the load that the system can process, but if the substrate is too deep, the bottom conditions become anaerobic and can reduce the removal of BOD 5 [7] . An effective porosity of the substrate of 0.346 for sand and gravel was considered, finally obtaining an area for each VSSFWC of 3 m 2 , necessary for the reduction of BOD 5 . In Table 3 , the design parameters of the pilot-scale experimental wetlands are presented. The VSSFWCs operated with an HLR of 0.2 m day −1 . The granulometry of the material recommended by [7] was considered. The design data is described in Table 3 , this table presents the design parameters of the VSSFCW, which include: HLR, Flow, Residence time, Depth, Area, Long, Width, Slope, Vegetation density (Supplemental File 5).

Construction of the pilot-scale VSSFWCs
For the construction of the VSSFWCs, excavation work was carried out, until two pits of 3 m long, 1 m wide and 0.7 m deep each were obtained, then they were covered with high-density polyethylene (HDPE) to avoid infiltrations. The treated water drainage and conduction system were built with a 50 mm PVC pipelines and fittings. For the continuous supply of water (influent) to the VSSFWCs, 16 mm diameter polyethylene hoses were used. These hoses were drilled lengthwise to regulate flow at each point in the wetland, forming a closed-loop that allowed the influent to be distributed equally over the entire surface of the wetland. Six vertical aeration pipes connected to the drainage collection system were installed [6] . For the filter medium, gravel and silicon sand were used. Twelve plants of each investigated species (Phragmites Australis and Cyperus Papyrus) were planted for each wetland, with a density of 4 plants m 2 ( Fig. 3 ).

Collection of samples and analysis
After the Phragmites Australis and Cyperus Papyrus were planted, the wetlands were filled for a week. From the second week on, the wetland was fed water at a flow rate of 0.6 m day −1 . During two months the development of the plants and the purified effluent were observed. After four months of planting, the plants reached a suitable height. The experiment started in January and ended in July. The sampling was carried out from April to July.
The performance efficiency of the Phragmites Australis and Cyperus Papyrus in VSSFCW was evaluated, for which water samples were collected biweekly for three months to measure: pH, total suspended solids (TSS), electrical conductivity (EC), alkalinity (Alk), ammoniacal nitrogen (NH 3 -N), nitrate (NO 3 -N), total phosphorus (TP), biochemical oxygen demand (BOD 5 ), chemical oxygen demand (COD), total coliforms (TC) and fecal coliforms (FC) according to the standard methods for the examination of water and wastewater.
The data presented in this article are related to the research article entitled "Performance of Phragmites Australis and Cyperus Papyrus in the treatment of municipal wastewater by vertical flow subsurface constructed wetlands" [7] .
As it can be observed in Fig. 2   ideal for wetlands built on a large scale, due to its high effect of eliminating pollutants present in wastewater domestic. These data allow choosing a suitable vegetation for a VSSFCW that you want to implement in the treatment of domestic wastewater.