This paper presents a case study describing a full-scale membrane bioreactor (MBR) for the pretreatment of landfill leachates. The treatment train includes an aerated equalization tank, a denitrification tank, an oxidation/nitrification tank, and two ultrafiltration units. The plant has worked continuously since 2008 treating landfill leachates at a flux of 2–11 L·h⁻¹·m⁻². The old train of membranes worked in these conditions for more than seven years prior to being damaged and replaced. The permeability (K) of the membrane varied between 30 and 80 L·h⁻¹·m⁻²·bar⁻¹ during the years of operation. In 2010, after two years of operation, the oxidation/nitrification tank was changed to work in alternate cycles of aerated and anoxic conditions, in order to improve the denitrification process. The MBR, working at a mean sludge retention time of 144 days and with mixed liquor suspended solids of 17 g/L, achieved high removal rates of conventional contaminants, with more than 98% for Biochemical Oxygen Demand, 96% for ammonium, and 75% for Chemical Oxygen Demand (COD). From the COD balance, half the COD entering was determined to be biologically oxidized into carbon dioxide, while another 24% remains in the sludge. In order to obtain these results, the company used 5.2 KWh·m⁻³, while spending 0.79 €·m⁻³.

In this paper the design and start-up of a constructed wetland (CW) for the tertiary treatment of landfill leachates is presented. The flux is characterized by high salinity, high concentration of nitrogen (almost completely in the form of nitrate) and a BOD/COD ratio close to zero. The CW pilot plant suffered from mechanical and hydraulic malfunctions which led to an uneven growth of plants inside the tanks. Despite this, COD has been reduced in the range of 0–30%, reduced forms of N (ammonia and nitrite) are also oxidized and removed by 50–80% and 20–26% on average. Considering the low number of plants and the loading rate, CW pilot plant allowed to remove more than 16 kg of COD, leading to a specific removal of 10 gCOD/d · m². Moreover, bacterial communities associated to plants were isolated and analyzed in order to evaluate the influence of such communities on phytoremediation. Bulk soil registered the lowest bacterial titers, while plant compartments and rhizospheric soil showed to be more suitable for bacterial colonization. 25 different bacterial genera were observed among the analyzed isolates, with the predominance of Pseudomonas genus.