Pilot-scale models of treatment of landfill leachates combined with urban wastewaters in a facultative lagoon

Abstract

This study set out to determ ine the potential for treating leachates in combination withwastewater at Facultative Lagoons, a device normally used for treating raw wastewaters.Pi lot-scale models were used to simulate leachate treatment and disposal in a FacultativeLagoon (FL), combining 2.4 L/hr of raw wastewater with a leachate m ixture (comprising bothyoung and old leachates), in concentrations of 4%, 6%, and 1 0% (v/v). The solution ofleachate mixture in raw wastewater was then fed into the two pilot-scale models (MI andM2). The fol lowing parameters : concentration of algae; chlorophyll a, b and c; faecalcoliforms (FC); and heavy metals, were analyzed in all the three component stages: theunmixed wastewater; the old and young leachate mixture; and the combined wastewaterleachate mixture.As a 1 0% di lution was found not to impede correct functioning of the Model FacultativeLagoon, the same concentration was tried out using urban wastewaters from the UniversityWastewater Treatment Plant (UWTP).Interval values of BODs and COD in the wastewater and in the leachate mixture were 45-875mg/L and 307-5,763 mg/L respectively, and results showed that a I 0% concentration ofleachates combined with wastewater does not upset the system of biological treatment. Noneof the m ixtures affected the population of algae. Maximum removal efficiency of BOD5 was75%, and 35% for COD, therefore leav ing a BOD5 level of less than 25 mg/L in the efflouentfrom the FL. The removal of BOD5 and COD from the U WTP was greater still, 86% and64%, respectively. FC and heavy metal concentrationso: As (0.007 mg/L), Cd (0.02 mg/L), Cu(<0.0 l mg/L), Cr ( 0.04 mg/L), Hg (o<0.00027 mg/L), Ni ( 0.15 mg/L), Pb (0.098 mg/L), CN(0.02 13 mg/L) and Zn (0.05 mg/L), were all below the maximums establ ished by the MexicanFederal Regulation for Re-use of Wastewater in Agricultural Irrigation (NOM-ECOL-00 1 -1 996).