Treatment of mixed leachate type I and type III by filtration and chemical oxidation

Resumen

In Riobamba city from Ecuador, for more than thirty years solid urban waste was placed in an open dump, without gas and leachate control. In 2016, the landfill was technically closed and an emerging cell with the characteristics of a sanitary landfill was built nearby. The Environmental Health and Hygiene Management Department of the Riobamba Municipal Decentralized Autonomous Government monitors leachate generation, recording 19.24 m3/day of young leachate (Type I) from the emerging cell and 5.78 m3/day of mature leachate (Type III) from the old landfill. The two types of leachates are mixed in the main collection pipe that reaches a storage pool that receives 25.02 m3/day. The results of the physical-chemical analysis determine that the values of the parameters are outside the permissible limits. Turbidity is >1000 NTU (Nephelometric Turbidity Unit), and the concentration of suspended solids is 1200 mg. L^-1 and iron 135.85 mg. L^-1. Calcium (1223 mg. L^-1) and manganese (356.15 mg. L^-1) were also evaluated, as these minerals are related to the 16,000 mg. L^-1 of hardness. For the treatment of the mixed leachate, two phases are proposed: a) physical treatment by downward filtration in a granular bed to reduce the concentrations of suspended solids, and b) chemical treatment by oxidation using sodium hypochlorite. Laboratory results showed a 96.40% decrease in the concentration of suspended solids. Turbidity stabilized at 65 UTN. Iron, calcium, and manganese concentrations decreased by 95.60%, 96.28%, and 50.60%, respectively.