Posttreatment of UASB Effluents of Tapioca Starch Wastewater Using Downflow Hanging Sponge System

Abstract

This study is aimed at a performance evaluation of downflow hanging sponge (DHS) systems using mixed fungal and bacterial cultures for posttreatment of upflow anaerobic sludge blanket (UASB) effluents of tapioca starch wastewater. The effects of sludge composition on the microbial activity and effluent organic matter were also investigated. The whole experiment consisted of RUN I and RUN II with hydraulic retention times (HRTs) of 7 and 1 h, respectively, and the organic loading rates (OLR) ranged from 2.0 to 6:0 kg COD/m 3 day -1 . The organic removal efficiencies were higher in RUN II, in the 94-96% range for both DHS systems. Under steady-state conditions, the volatile suspended solids (VSS) concentration in the sludge retained in the fungal downflow hanging sponge (FDHS) system showed little change, indicating a balance between the degradation of old biomass and the accumulation of the fresh biomass. Also, there was no significant removal of nitrogen in the FDHS system. However, the nitrogen was reduced in the bacterial downflow hanging sponge (BDHS) system, possibly through nitrification and denitrification processes. Both DHS systems exhibited marked stability with regard to the fluctuations in hydraulic loading. The results of this study showed that the proposed DHS systems could be promising for posttreatment of UASB effluents. © 2012 American Society of Civil Engineers.