Study of the reuse of treated wastewater on waste container washing vehicles

The wheelie bins for the collection of municipal solid waste (MSW) shall be periodically washed. This operation is usually carried out by specific vehicles which consume about 5000 L of water per day. Wastewater derived from bins washing is usually stored on the same vehicle and then discharged and treated in a municipal WWTP. This paper presents a study performed to evaluate the reuse of the wastewater collected from bins washing after it has been treated in a small plant mounted on the vehicle; the advantage of such a system would be the reduction of both vehicle dimension and water consumption. The main results obtained by coagulation-flocculation tests performed on two wastewater samples are presented. The addition of 2 mL/L of an aqueous solution of aluminum polychloride (18% w/w), about 35 mL/L of an aqueous solution of CaO (4% w/w) and 25 mL/L of an aqueous solution of an anionic polyelectrolyte (1 ‰ w/w) can significantly reduce turbidity and COD in treated water (to about 99% and 42%, respectively); the concomitant increase of UV transmittance at 254 nm (up to 15%) enables UV disinfection application by a series of two ordinary UV lamps. Much higher UV transmittance values (even higher than 80%) can be obtained by dosing powdered activated carbon, which also results in a greater removal of COD.