Wastewater purification and recycling using plants in an arid environment for agricultural purposes: case of the Algerian Sahara

Abstract

The aim of this study is to apply a water treatment technique (phyto-purification) in the Algerian Sahara, an arid region, to resolve the scarcity of irrigation, recycled wastewater and preserve Saharian ecosystems composed of sand and two species of aquatic plants: Typha latifolia and Imperata cylindrica. The choice of these plants was determined based on the natural vegetation, soil and climatic characteristics of the study area. To this end, we developed an experimental pilot composed of three tanks measuring 30 cm × 35 cm × 45 cm, arranged with a filter bed of sand and gravel. Two of these tanks are sown with the above-mentioned plants, while the third tank, serving as a control, is not. The values of the main wastewater pollution parameters, namely total nitrogen compounds, ammonium (NH4+), chemical oxygen demand (COD) and suspended solids measured at the outlet of the device, substantiate the performance of this treatment system. Indeed, the nitrogen reduction rate increased from 63% in the unplanted control filters to around 80% in the planted filters, and from 81 to 88% for NO3−. Regarding chemical oxygen demand (COD), the reduction rate exceeds 88.37% for the three tanks. The study of the analytical approach to modeling the purification kinetics reveals that the kinetics of COD and NH4+ are well correlated with the first-order model, with an explained variance varying between 68.1 and 81.6% for COD and 83.5 and 92.3% for ammonium. The Riverside diagram highlights that all treated water samples fall into the low sodium risk and high salinity risk class. Build on the Na% values; all purified waters have characteristics suitable for water use for irrigation.