Oilfield wastewater contaminants removal efficiencies of three indigenous plants species in a free water surface flow constructed wetland

Figures & data

Figure 1. Schematic diagram of free surface flow constructed wetland cells with 3 different native plants.

Table 1. Characteristics of effluent after conventional treatment and discharge limit

Parameter	Minimum	Maximum	Mean Effluent concentration± SD	Discharge limit
Oil and Grease (mg/L)	33.80	102.70	70.83 ± 21.41	20.00
BOD (mg/L)	405.00	9600.00	5866.57 ± 3570.75	200.00
COD (mg/L)	784.00	15,100.00	10,809.60 ± 5263.65	1000.00
EC (μS/cm)	860.00	81,400.00	29,432.00 ± 23,526.04	1500.00
TDS (mg/L)	7480.00	49,460.00	20,087.63 ± 13,707.21	1000.00
TP(mg/L)	0.69	102.60	31.73 ± 39.24	10.00
Nitrate (mg/L)	3.90	7.89	6.44 ± 1.29	100.00

Table 2. Characteristics of media (soil) in the free surface flow constructed wetlands

Parameter/ unit	Minimum	Maximum	Mean and std dev
pH	6.25	6.27	6.26 ± 0.01
EC (µS/cm)	229.10	233.10	231.00 ± 2.01
%N	0.19	0.21	0.20 ± 0.01
P(µg/g)	4.19	7.38	5.46 ± 1.69
K(cmol/kg)	0.49	2.52	0.50 ± 0.02
Ca(cmol/kg)	7.33	7.48	7.41 ± 0.08
Mg(cmol/kg)	2.28	2.52	2.42 ± 0.12
Na(cmol/kg)	0.52	0.52	0.52 ± 0.00
%Organic Carbon	2.04	3.73	2.10 ± 0.07
%Organic Matter	3.50	3.72	3.62 ± 0.11

Table 3. Descriptive statistics for plant growth (height), biomass and water content of the three plant species

Plant type	Minimum (cm)	Maximum (cm)	Mean and std dev	Water content (kg)	Biomass of standing plant (kg/m^2)
Typha latifolia	56.39	177.99	111.346756 ± 30.88	4.75	0.0009552
Ruellia simplex	27.94	74.12	55.294500 ± 10.92	1.55	0.0908000
Alternanthera philoxeroides	22.86	67.44	42.1741 ± 11.11	2.15	0.0496000

Table 4. Contaminants removal efficiency of the native plants in a free water surface flow constructed wetland

Parameter	Mean removal efficiency (%) in wetlands planted with:
	Typha latifolia	Ruellia simplex	Alternanthera philoxeroides	Control	F	P-value
Oil and Grease (mg/L)	54.55	49.23	57.23	40.93	28.20	0.000
BOD (mg/L)	47.62	39.92	50.02	30.51	11.55	0.000
COD (mg/L)	39.67	32.93	39.81	26.27	4.67	0.001
Conductivity (μS/cm)	47.13	32.56	52.51	24.99	4.58	0.001
TDS (mg/L)	37.30	28.19	43.21	28.20	5.47	0.000
Tot Phosphorus (mg/L)	44.41	40.83	41.22	31.70	20.00	0.960
Nitrate (mg/L)	41.87	38.67	36.40	27.33	51.17	0.000
Total Coliform (MPN100/ml)	46.39	49.62	48.47	43.71	3.97	0.004