Treatment, at real scale, of a Mediterranean running water with Acid Mining Drainage (AMD) characteristics using floating beds

Abstract

Context/Purpose: In the Southern of Alentejo region (Portugal), the surrounding area of Roxo stream features sections completely sterile, putting in question the productivity of agricultural activities there lo-cated. This may be due to the affluence of the Água Forte stream, which has Acid Mining Drainage (AMD) characteristics. In view of this situation, it is considered relevant to solve this problem, using ef-fective solutions for the removal of pollutants and environmentally sustainable. • The use of Floating Beds (FB) is an Eco-rehabilitation strategy of pol-luted waters. They have the ability to degrade pollutants by taking ad-vantage of the benefits that ecosystems have, so they can be used to improve the quality of surface water bodies. In this study, the FB sys-tem is applied for treatment of running water (stream), which use has never been investigated. The aim of this work was to test, at real scale, the possibility of using the technique of Floating Beds in order to treat, the water of Água Forte stream, with the propose to improve their quality. • Methods: Three floating beds (3.3 m2/unit; density 40.5 plants/m2) were placed, on real scale, on Água Forte stream and water quality and macrophyte (Vetiveria Zizanioides) performance were monitored and evaluated monthly during May 2020 to November 2021 on two places; after FB location and 100m before them. • Results: The characterization of water quality of Água Forte stream has shown, among others: i) acid pH, ii) high Electrical Conductivity (EC), iii) high COD, iv) low Oxygen Dissolved (OD) levels, v) high levels of Fe, Zn, Cu and Mn, vi) low concentrations of Nitrogen and Phosphorous nutrients, vii) high levels of Chlorides and Sulphates, • The main removal rates obtained with treatment were i) SO42-= 8,0±12,0%, ii) EC=3,0%, iii) COD= 13,5±12,0%, iv) Cl-=9,0±8,0, v) Pt= 19,5±16,0%, vi)NH4+= 17,0± 15,0; vii) Cu = 29,6±20,0 %, viii) Zn = 21,5±15,0 %, ix) Fe = 49,8±29,0 % and x) Mn = 37,3±20,5 %. The pH remained acid. • Conclusion: Treatment by LFs seemed to be more effective in remov-ing metals compared to other parameters, although there has been a decrease in almost all physical-chemical parameters analyzed.