Constructed wetlands (CWs) are man-made systems designed to treat a range of residential, commercial, and industrial wastewaters. The objective of the study was to evaluate the efficiency of wastewater treatment systems using constructed wetlands. The effectiveness of removing chemical and physical pollutants was also evaluated. The setup consisted of a hybrid flow system composed of upflow constructed wetland and a horizontal flow constructed wetland connected in series that is used for primary treatment of the influent of domestic wastewater. Two systems were analyzed: one cultivated with the ornamental species Canna Indica, and one cultivated with the cattail Cymbopogon flexuosus. It consisted of two treatment sections consisting of two plant species Cymbopogon citratus (lemon grass – first CW) and Canna xalapensis Horan (Canna Indica – second CW). The water quality parameters i.e., BOD, COD, TSS were analyzed according to APHA (American Public Health Association) by daily sampling. The CW was monitored for the quality of wastewater inflows and outflows and nutrient accumulation in plants. Results showed that the maximum COD removal for Lemon Grass and Canna Indica beds were 75% and 70% respectively at 200mg/L COD loading in the CW setup over a six-month period respectively. The maximum BOD removal found in Lemon Grass and Canna Indica beds were 73% and 64% respectively at a feed concentration of 200mg/L COD. Both the CWs together as one unit showed similar rates of TSS removal irrespective of the type of wetland plant species and were more efficient in treating wastewater.

Constructed wetland (CWs) systems offer an economical alternative to wastewater (WW) treatment in developing countries. So this study investigated lab-scale hybrid constructed wetlands (HCWs) with plant species Canna indica and Typha latifolia in mono and mixed culture for removing organic matter and nutrients from municipal wastewater (MWW) under arid climatic conditions. A HCW system consists of a storage tank feeding four series of vertical flow constructed wetlands (VFCWs) followed by horizontal flow-constructed wetlands (HFCWs). The results indicate that the planted beds performed better in removing suspended solids (TSS) (89.93% by Typha latifolia), biochemical oxygen demand (BOD5) (95.01% by mixed-culture), chemical oxygen demand (COD) (90.77 by Typha latifolia), nitrite (NO2-) (89.99% by mixed-culture), ammonium nitrogen (NH4+) (99.98 % by mixed-culture), and orthophosphate (PO43-) (87.22% by Typha latifolia) as compared to the unplanted bed for the same parameters (87.85%, 92.87%, 77.35%, 85.30%, 99.75%,  and 80.95%), respectively. The nitrate (NO3−) concentration in the effluent recorded the highest increase in the VFCW unit planted with mixed culture from 0.44 to 0.999 mg/l and decreased in the second stage to 0.588 mg/l at the HCW outlet. The mean values of the testing parameters in different HCW systems were not significant between the mono and mixed culture (P > 0.05), with a significant difference (P <0.05) between the VFCWs and HFCWs. The finding of this study demonstrated that Canna indica and Typha latifolia have been effective in WW treatment by HCW systems.

The use of constructed wetland (CW) is a natural way of treating wastewater sustainably and economically. However, the implementation of these systems in freezing conditions is still a matter of research and development. The treatment capacity of CWs relies largely on the biological and biochemical processes which further depends on physical conditions such as temperature, solar radiations, etc. Application of wetland systems for treating wastewater faces many challenges in regions with cold climates, resolving which this review has been made. This paper presents a thorough understanding of the components of CWs and their role in contaminant removal. A comprehensive review of the different types of CWs has been done describing the treatment efficiency achieved by its implementation in the cold climate. Furthermore, various technologies which can be clubbed with CWs have also been listed along with the treatment efficiencies obtained. Literature survey indicates that the extent of removing organics (COD and BOD5) and total phosphorous (TP) are not likely to be affected, but total nitrogen (TN) removal appears to slow down at low temperatures. Despite several advantages of CW technology, further research is required to select suitable macrophytes and optimum design parameters to compensate for frigid conditions.