Vertical Constructed Wetland System Research Articles

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 Almería, 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 m3 d−1. The experimental demo plant with a 3000 m2 HRAP and 200 m2 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.

TREATMENT OF SEPTIC TANK SLUDGE IN A VERTICAL FLOW CONSTRUCTED WETLAND SYSTEM

ABSTRACT: The study consisted of the evaluation of the treatment of septic tank sludge in a vertical constructed wetland system (CW), built according to the first stage of the French system. The system operated also for sewage treatment and one of the beds (area of 29.1 m2, height of the support medium of 0.7 m and planted with Tifton 85 grass, Cynodon dactylon Pers), began to receive the application of sludge from clean-pit trucks once a week. The percolated liquid was directed to post-treatment in the other two beds of the French system. The application of the raw sludge had average hydraulic loading rate of 13.1 m3/m2.year and solids loading rate of 81 kgTS/m2.year. The system improved the quality of percolated liquid in terms of carbonaceous and nitrogenous matter (average COD removal efficiencies of 82% and TKN of 63%), but the percolate post-treatment strategy did not result in substantial improvements. The dewatering of the accumulated sludge on top of the bed occurred satisfactorily (55% of dry solids), the Tifton 85 grass was resistant to the operational conditions and the system proved to be a compact technology (sludge treatment capacity of an equivalent population between 1140 and 3799 inhabitants in the unit of 29.1 m2, corresponding to 39 to 131 inhabitants per m2 of surface area).