Hydrolysis evolution in a codigestion reactor at various hydraulic residence times

The aim of this research is to study the influence of two different hydraulic residence times (HRT's), 5 and 10 days, on the process of hydrolysis-solubilization in a codigestion reactor. Tap water was used to simulate recirculation of a treated leachate. Organic solid waste (OSW) from urban solid waste (USW) and excess sludge from an urban wastewater treatment plant were first characterized and then treated together by anaerobic codigestion. This was done using a 27.2-L total volume pilot scale bioreactor, which was loaded with equal amounts (w/w) of OSW and sludge to a total useful volume of 13-L. The bioreactor was filled with tap water to ensure high humidity. In order to assure suitable mixing and good microbial-substrate contact in the reactor, recirculation of treated effluent was maintained by continuous water flow. The influence of HRT on the process performance was determined through physicochemical characterization of the effluent. Results indicate that HRT is a determinant factor in the efficiency of the system. Reducing HRT increases hydrodynamics and solubilization kinetic rate of organic matter in the bioreactor. Stabilization time of solids is reduced from 20 to 10 days when HRT is shortened from 10 to 5 days