Granulometric composition of the upflow filter for post-treatment of landfill leachate

ABSTRACT

Landfill leachate presents variable and complex composition and may have high concentrations of ammoniacal nitrogen and biodegradable and recalcitrant organic matter. Due to the high polluting potential of stabilized leachate, in addition to conventional biological treatment, it is necessary in some cases to perform post-treatment to remove recalcitrant organic matter to meet the current legislation. In this context, the coagulation followed by upflow gravel filtration experiments were carried out with the objective of establishing the granulometric composition that resulted in the best efficiency condition in relation to the removal of recalcitrant organic matter and operation, aiming at the system’s application in real scale. For all the tests, a constant filtration rate of 15 m³ m^-2 day^-1 and an iron dosage of 400 mg L^-1 at pH 4.0 were applied. The duration of filtration cycles, as well as the quality of the effluent were strongly influenced by the filter’s particle size, and it is possible to verify the need of using fine sand in its composition to guarantee the treatment’s efficiency. The technical design of post-treatment by coagulation followed by upflow gravel filtration with the granulometric composition defined in this study (type 4) was efficient in removing recalcitrant organic matter, with removals of 82.4% for COD (residual value of 194 mg L^-1), 98.8% for true color (with residual value of 49 uH), and 94.3% for TOC (residual value of 52 mg L^-1), resulting in a filtration cycle duration of 22.6 h, with no loss of filtered solids.

Keywords:
landfill leachate; physical-chemical post-treatment; upflow gravel filtration; granulometric composition