Treatment of leachate
Leachate from municipal solid waste contains high quantities of pollutants as COD, heavy metals (aluminium, copper, iron), boron, oils, ammonium, chlorides and other organic substances, which removal needs of a concentration process that usually requires different technologies.
VENZA has designed a section of a leachate depuration plant installed in a Northern Italian platform for urban waste disposal and treatment.
The process, able to treat 40.000 tons of leachate per year, is composed of different sections. Wastewater, collected in accumulation tanks, is sent to a double stage reverse osmosis filtration plant. The machine receives 120 m3 of effluent per day, producing 90 m3 of osmotized water and 30 m3 of retentate.
This last one is furtherly concentrated in an evaporator powered only with electrical energy, able to lower its volume until to 6 m3, equivalent to 5% of leachate coming in treatment system.
Considered the high fees for leachate disposal because of nature of pollutants contained in it, the inclusion of another evaporation plant, that would reduce it until to 2 m3, is under evaluation.
Distillate coming out from evaporator, mixed with osmotized water, is discharged into soil in respect of strict parameters established by environmental laws for this destination of treated water.
The operating costs of the plant are considerably reduced thanks to recovery of biogas produced by natural anaerobic fermentation of waste, employed for feeding of a cogeneration system that supply the power required for working of whole process.
The operator has not sustained investment costs, having opted for the BOT (Build Own and Transfer) formula, that is the operating rental through an ESCo (Energy Service Company), with possible final redemption. In case of direct buying, facilitated finance instruments for capital goods purchase – in Italy, 4.0 Transition plan and Sabatini law – allow anyway a recovery of more than 60% of investment; the return on investment is moreover facilitated by the choice of vapor compression evaporation technology, that can benefit of white certificates as established by European Directive.
