Analysis of the Anaerobic Digestion Process Performed by Upflow Anaerobic Filters in Two and Three Separated Stages Treating Sanitary Landfill Leachates

ABSTRACT This paper deals with the analysis of the anaerobic digestion process performed by Upflow Anaerobic Filters in Two and Three Separated Stages (UAF‐2SS and UAF‐3SS), treating sanitary landfill leachates (SLLs). SLLs were fed to UAF‐2SS and UAF‐3SS at three temperatures (20°C, 27°C, and 34°C), three volumetric organic loads (VOLs) (2.25, 3.45, 4.64 kgCOD (Chemical Oxygen Demand)/m 3 /d)), total depth (D) fractionation in two‐stages (D1/D2: 20%/80%, 50%/50%, and 80%/20%), and three‐stages (D1/D2/D3: 4%/16%/80%, 10%/10%/80%, and 16%/4%/80%). The microbiological sampling demonstrated that the total depth fractionation produced the prevalence of species associated with each of the stages of anaerobic digestion. In UAF‐3SS was identified the presence of hydrolytic and acidogenic bacteria in Stage 1, acidogenic and acetogenic bacteria in Stage 2, as well as acetogenic and methanogenic bacteria in Stage 3. In general, the experimental factor causing the most significant effect on the COD removal efficiency was the temperature (T), followed by the d 1 / d 2 ratio and the least influence was produced by the VOL. The effect models for orders from first to third included coefficients of the variables associated to the principal and interaction effects, that were mainly representing to the biosorption process in the residual liquid‐biofilm interface within UAF‐2SS and UAF‐3SS reactors, whose values are similar to those reported for trickling filters and tropical rivers. These results are suggesting that the first stages in the anaerobic digestion associated with hydrolysis and acidogenic reactions constitute the fundamental processes in the UAF‐2SS and UAF‐3SS perform by treating organic mass composing SLLs. The novelty of the research consists of providing mathematical structures whose coefficients allow to estimate with greater depth the rates at which the substrate transport processes are performed in the SLLs‐biofilm interface within UAF‐2SS and UAF‐3SS.