Desempenho de reatores anaeróbios com meio suporte de bambu sob diferentes cargas orgânicas em duas relações comprimento:diâmetro no tratamento de efluentes de fecularia

Abstract

The liquid waste from the cassava starch has a high organic load mainly due to high concentration of carbohydrates, which provides an ideal medium for the development of fermentative bacteria. The use of anaerobic reactors with media support provides increased contact area of microorganisms in the reactor and better fixation of these, resulting in the possibility of applying higher daily organic loads and a considerable reduction of detention time required for the treatment of tributary. In this context, the objective of this paper is to conduct a study of the process of digestion in two anaerobic biofilter with bamboo in the treatment of effluent of cassava starch, by evaluating the performance of systems and determining the kinetic constants of the degradation of organic matter along the reactors. The anaerobic reactors used were made of PVC tubes showing relations diameter:length 1:3 and 1:6. Along the profile of the reactors were installed five sampling points of effluent spread halfway, through which the samples were collected for determination of rate constant of consumption of organic matter and the kinetic model which best represents the consumption of organic matter along the profile of the systems. The two reactors were filled with a support medium consisting of rings of bamboo and useful volume calculated for the reactors was 6.8 and 6.0 L for the diameter: length ratio of 1:3 and 1:6, respectively. To measure the amount of biogas produced, each reactor was connected to a gas tank partially filled with a solution of 3% H2SO4 and 25% NaCl. The organic loading applied to the system were 0.519, 1.156, 1.471, 3.049, 3.813, 4.347, 4.708 and 5.601 g.L-1d-1 and the process was evaluated daily for two weeks throughout the analysis of COD removal, TS and VS, for VA/TA and volume of biogas as a function of COD consumed. At the end of the fifteen days of evaluation system, samples were collected along the profile of the reactors and analyzed to verify the COD consumption of organic matter along the reactors. The results showed that the various diameter lengths of the reactors did not influence their efficiency with respect to removals of COD, TS and VS for organic loads applied. The systems also showed a stable behavior in relation to the ratio VA/TA for all charges assessed, suggesting withstand higher organic loads. The first order kinetic model was best represented the kinetic consumption of organic matter with respect to the reactor diameter to length is 1:6 and a rate constant k 3,4.10-2 h-1. For the reactor with diameter ratio: 1:3 length to second-order kinetic model was best represented the behavior of the system for this variable, the rate constant k obtained from 1,96.10-4 h-1.