&lt;b&gt;Effect of hydraulic retention time on hydrodynamic behavior of anaerobic-aerobic fixed bed reactor treating cattle slaughterhouse effluent

Daiane Cristina De Freitas,Fernando Hermes Passig,Cristiane Kreutz,Eudes José Arantes,Simone Damasceno Gomes,Karina Querne De Carvalho

doi:10.4025/actascitechnol.v39i4.30995

Abstract

The study of the hydrodynamic behavior in reactors provides characteristics of the flow regime and its anomalies that can reduce biological processes efficiency due to the decrease of the useful volume and the hydraulic retention time required for the performance of microbial activity. In this study, the hydrodynamic behavior of an anaerobic-aerobic fixed bed reactor, operated with HRT (hydraulic retention time) of 24, 18 and 12 hours, was evaluated in the treatment of raw cattle slaughterhouse wastewater. Polyurethane foam and expanded clay were used as support media for biomass immobilization. Experimental data of pulse type stimulus-response assays were performed with eosin Y and bromophenol blue, and adjusted to the single-parameter theoretical models of dispersion and N-continuous stirred tank reactors in series (N-CSTR). N-CSTR model presented the best adjustment for the HRT and tracers evaluated. RDT (residence time distribution) curves obtained with N-CSTR model in the assays with bromophenol blue resulted in better adjustment compared to the eosin Y. The predominant flow regime in AAFBR (anaerobic aerobic fixed bed reactor) is the N-CSTR in series, as well as the existence of preferential paths and hydraulic short-circuiting.

Highlights

The challenge of current society, related to sanitation, is to project wastewater treatment systems that are functionally simple, aiming good cost/benefit relation beyond efficiency, to attend the standards established in the current environmental legislation.Acta Scientiarum
These anomalies may reduce the efficiency of the reactors caused by the decrease of useful volume and hydraulic retention time required to the performance of the microbial activity (Persson, Somes, & Wong, 1999, Carvalho, Salgado, Passig, & Pires, 2008)
residence time distribution (RTD) curves and the single-parameter models adjustment indicate that the perfect mixing represents satisfactorily the flow regime in the AARFB reactor

Summary

Introduction

The challenge of current society, related to sanitation, is to project wastewater treatment systems that are functionally simple, aiming good cost/benefit relation beyond efficiency, to attend the standards established in the current environmental legislation. Most part of the biological reactors operating for effluent treatment does not present an ideal hydrodynamic behavior, but can be considered, inside a range of acceptable error, plug flow or complete mixture reactors (Bewtra & Biswas, 2006). RTD curves indicate the long tailing phenomenon that probably occur with the tracer due to its diffusion in the dead zones, adsorption in the biomass or presence of hydraulic short-circuiting in the reactor These anomalies may reduce the efficiency of the reactors caused by the decrease of useful volume and hydraulic retention time required to the performance of the microbial activity (Persson, Somes, & Wong, 1999, Carvalho, Salgado, Passig, & Pires, 2008). This study sought to evaluate the hydrodynamic behavior of an anaerobic-aerobic fixed bed reactor, operated in bench scale, treating raw agro-industrial effluent from cattle slaughterhouse, located at the city of Campo Mourão, in the State of Paraná, Brazil

Material and methods

Results and discussion

Conclusion