Grey water treated by an hybrid constructed wetland pilot plant under several stress conditions

Abstract

The aim of the present study was to design, realize and analyze a functional hybrid phytoremediation pilot platform. With the purpose of evaluating the feasibility and the treatment efficiency under variable and stress conditions, the pilot plant was tested with and without vegetation at the design specifications and different organic and hydraulic load of grey water were performed. The Chemical Oxygen Demand (COD), electrical conductivity (EC), pH and total dissolved solids (TDS) were analyzed in the different treatment stages of the system. The results of the tests conducted with an inlet flow ten times higher than design ones (500L/d) showed that the pilot plant is able to work until contaminants elements are three times higher of the design quantity. When the tests with vegetation presence were started inside the pilot platform, the results obtained were always positive (in terms of COD reduction). Using design inlet flow of 50L/d with two times and four times higher grey water pollutant quantity, the COD values drop to zero after the initial stage (that has a retention time measurable in minutes). The vegetated system is able to handle the COD reduction of an OLR that at the beginning of the treatment stage had a value of about 31 gCOD/m2/d, equal to a triple charge of pollutants, and a flow four times greater than the design one with triple charge of pollutants and conducting the tests at increasing inlet flow.