Effectiveness of Floating Treatment Wetlands with Cyperus papyrus Used in Sub-Humid Climate to Treat Urban Wastewater: A Case Study

The wastewater from small communities and rural areas, usually discharged in an unsuitable manner, requires an appropriate treatment. The floating treatment wetland has revealed a great potential due to good performance, low cost and low maintenance means of improving water quality over a broad range of applications. The aim of this article was to present the results of the adaptation period (57 days) of a macrophyte plant “Cyperus papyrus” and its potential for treating wastewater generated by the campus of the National Office of Electricity and Drinking Water (ONEE) of Rabat. Two hydraulic retention times were applied: 2 and 4 days. Pilot experimental setups (two tanks) were installed: one tank where the macrophyte, being the subject of the study, was installed and the other served as a control. The macrophyte plants were suspended in floating mat, keeping the plant roots permanently in contact with the water and removing pollutants via several processes. During the adaptation of the plant which concerned four parameters: the evolution of the density, the height of the stems, the number of shoots as well as the state of health of the plants, a period of adaptation to the medium of implantation of fifty-seven days was observed. Along this adaptation phase, the results showed that: plant density increased from 9 to 29 units; the heights of the four identified stems of Cyperus papyrus increased from 15, 6, 11 and 8 cm to 73, 43, 30 and 24 cm, respectively; the appearance of 72 shoots and the plant has completed the adaptation phase in good health (absence of disease Symptoms). The treated water obtained from outlet and wastewaters were analyzed for various water quality parameters, such as Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), and Suspended Solids (SS). The floating treatment wetlands system is able to remove 37.8% of COD; 47.6% of BOD5and 74.4% of SS for HRT of 2 days and 63.7% of COD; 78.4% of BOD5 and 89.1% of SS for HRT of 4 days. Moreover, it was found that the purification efficiency in terms of these three pollution parameters is all the more important as the hydraulic retention time is high.