Hybrid wastewater treatment system based in a combination of high rate algae pond and vertical constructed wetland system at large scale

This study aims to compare a conventional wastewater treatment plant and a hybrid alternative treatment plant for the treatment of real urban wastewater from the city of Almeria, Spain. The hybrid treatment plant combines a semi-extensive wastewater treatment systems such as a high rate algae pond (HRAP), a dissolved air flotation unit to separate algae biomass from treated wastewater and an extensive wastewater treatment systems such as vertical flow constructed wetlands. The conventional wastewater treatment plant has a treatment capacity of 4000 m(3) d(-1). The experimental demo plant with a 3000 m(2) HRAP and 200 m(2) of wetlands surface has been operated throughout one year in parallel with a conventional activated sludge full-scale plant, obtaining a complete comparison of both systems. Regarding removal efficiencies, the new hybrid system achieved values of 96.6%, 76.6% 89.8% and 99.9% for COD, TN, TP and TSS, respectively. The hybrid systems reach disinfection rates of 4 and 5 log units for total coliforms and E.Coli, respectively. Energy demand required in the hybrid system was five times lower than a conventional activated sludge (0.1 kWh m(-3)). The results here obtained demonstrated the capacity of using hybrid alternative treatment plant as an efficient way of treating wastewater in small populations.