Combined UASB-MBR system for the treatment of low-strength wastewater at ambient temperatures

Abstract

The application of anaerobic processes for the treatment of diluted wastewaters has received high attention in recent years. However, there exist some crucial disadvantages: the necessity of post-treatment due to the presence of residual biodegradable organic matter, diminution of activity of anaerobic biomass, especially in cold/mild regions, and, consequently, possible wash-out of biomass. Therefore, the combination of membrane filtration process with anaerobic digestion systems seems a promising alternative. The main goals of this research are going to be: 1.- Research of the capacity and characteristics of a newly designed combined UASB-MBR process at the USC. The system has a first methanogenic UASB (Up-flow Anaerobic Sludge Bed Reactor) stage, and a second MBR stage with an aerobic chamber with biofilms, where biomass is growing both in suspension and onto a plastic support maintained in suspension, and a membrane filtration chamber. The first objectives should be to study the COD removal capacity, fouling, and the interactions between the different stages of this system. The reactor should be tested at temperatures in between 15 and 25 °C, using a synthetic urban and/or industrial wastewater. Microbial ecology of each system stage will be described using microbiological techniques such as Fluorescent in-situ Hybridization (FISH) and Denaturing Gradient Gel Electrophoresis (DGGE). Furthermore, the activity of particular biomass populations will be measured, in order to estimate the maximum capacity of the system at various environmental and operational conditions. Finally, the combined UASB-MBR system is going to be compared with reference to other aerobic and anaerobic MBRs. 2.- Research at the TU Delft (The Netherlands) will focus on anaerobic MBR (AnMBR) system for the treatment of synthetic domestic wastewater under ambient conditions. The potential influence of aerobic sludge introduction on AnMBR performance will be assessed in terms of fouling potential, taking into account parameters such as specific cake resistance (SCR) and filterability. The impact of colloidal fraction of biopolymeric cluster (cBPC), soluble microbial products (SMP) and extracellular polymeric substances (EPS), generated as a result of hydrolysis of introduced aerobic sludge, will be evaluated. Moreover, the impact of aerobic sludge on the specific methanogenic activity (SMA) will be studied. This research will help to understand the impact of internal sludge recirculation in combined UASB-MBR (studied in USC) system on membrane performance. The studies will be carried out in the frame of a collaborative project (Novedar_Consolider) between the laboratories of the University of Santiago de Compostela and the Technical University of Delft and supervised by ass. prof. Juan M. Garrido and prof. Jules van Lier, respectively.