Design, Construction and Modeling of Upflow Anaerobic Filters Separated in Two and Three Phases

Abstract

In this study, the models for the design of upflow anerobic filters separated into two and three
phases at laboratory scale are statistically adjusted, DI-FAFS and TRI-FAFS, respectively.
Both reactors have been evaluated in the COD elimination performance by applying a
factorial design 33, for a total of 54 tests. The experimental factors are three: the volumetric
organic load has been set at 2.25, 3.45 and 4.64 kg COD m-3 d-1, the temperature at 20, 27
and 34 ° C, the depth relationships D1 / D2: 20% / 80%, 50% / 50% and 80% / 20% in the
DI-FAFS and D1 / D2 / D3: 4% / 16% / 80%, 10% / 10% / 80% and 16% / 4% / 80% in the
TRI-FAFS. The surface hydraulic load was equal to 1.82 m3 m-2d-1. The filter total depth was
equal to 1.2 m. The packing medium consisted of a plastic material with a surface area equal
to 476.35 m2 m-3. The hydraulic retention time varied between 16 and 18 h. The flow rates
between 3.5 and 4 ml min-1. The efficiencies in organic matter elimination in the DI-FAFS
varied between 27 and 72.86%; in the TRI-FAFS between 84 and 92%. The maximum
efficiencies were achieved in the DI-FAFS with relation D1 / D2: 20% / 80%, and in the TRIFAFS
with relation D1 / D2 / D3: 10% / 10% / 80% for temperatures ≥ 27 ° C and VOL ≥ 3.45
kg COD m-3 d-1. The conceptual model is based on Equations deduced from a mass balance
under stationary conditions dS / dt = 0 and advective dS / dZ 0; formulating eight equations
applicable to the DI-FAFS and TRI-FAFS reactors; four Equations for each reactor; as
follows: 1) Equations 12 and 16 are based on the Velz Equations, (1948); Germain, (1966)
and Albertson, (1984); 2) Equations 13 and 14; 17 and 18 are based on the Equations of
Van't Hoff-Arrhenius, (1884); Velz, (1948); Schultze (1960); Germain (1966); Albertson
(1984), and 3) Equations 15 and 19 are based on the Equations of Van't Hoff-Arrhenius,
(1884); Velz, (1948); Germain, (1966) and Albertson, (1984); Schultze, (1960). These
equations were compared with the equation of Phelps, (1944) to obtain the parameters of
degradation of organic matter. Equations (14) and (18) resulted in an R2 adjusted greater
than 0.7; the standard error of estimation and the absolute average error resulted in the
minimum value in Equations (14) and (18) with respect to the rest of the Equations.