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 with
wastewater 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 Facultative
Lagoon (FL), combining 2.4 L/hr of raw wastewater with a leachate m ixture (comprising both
young and old leachates), in concentrations of 4%, 6%, and 1 0% (v/v). The solution of
leachate mixture in raw wastewater was then fed into the two pilot-scale models (MI and
M2). The fol lowing parameters : concentration of algae; chlorophyll a, b and c; faecal
coliforms (FC); and heavy metals, were analyzed in all the three component stages: the
unmixed 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 Facultative
Lagoon, the same concentration was tried out using urban wastewaters from the University
Wastewater Treatment Plant (UWTP).
Interval values of BODs and COD in the wastewater and in the leachate mixture were 45-875
mg/L and 307-5,763 mg/L respectively, and results showed that a I 0% concentration of
leachates combined with wastewater does not upset the system of biological treatment. None
of the m ixtures affected the population of algae. Maximum removal efficiency of BOD5 was
75%, and 35% for COD, therefore leav ing a BOD5 level of less than 25 mg/L in the efflouent
from the FL. The removal of BOD5 and COD from the U WTP was greater still, 86% and
64%, 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 Mexican
Federal Regulation for Re-use of Wastewater in Agricultural Irrigation (NOM-ECOL-00 1 -
1 996).