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.

Automated summary

The study compared a conventional wastewater treatment plant and a hybrid alternative treatment plant for real urban wastewater from the city of Almeria, Spain. The hybrid system showed higher removal efficiencies for COD, TN, TP, and TSS, as well as high disinfection rates for total coliforms and E.Coli. Additionally, the energy demand of the hybrid system was significantly lower than that of a conventional activated sludge plant.