ABSTRACT
Prevention and removal of fouling is often the most energy intensive process in Membrane Bioreactors (MBRs), responsible for 40% to 50% of the total specific energy consumed in submerged MBRs. In the past decade, methods were developed to quantify and qualify fouling, aiming to support optimization in MBR operation. Therefore, there is a need for an evaluation of the lessons learned and how to proceed. In this article, five different methods for measuring MBR activated sludge filterability and critical flux are described, commented and evaluated. Both parameters characterize the fouling potential in full-scale MBRs. The article focuses on the Delft Filtration Characterization method (DFCm) as a convenient tool to characterize sludge properties, namely on data processing, accuracy, reproducibility, reliability, and applicability, defining the boundaries of the DFCm. Significant progress was made concerning fouling measurements in particular by using straight forward approaches focusing on the applicability of the obtained results. Nevertheless, a fouling measurement method is still to be defined which is capable of being unequivocal, concerning the fouling parameters definitions; practical and simple, in terms of set-up and operation; broad and useful, in terms of obtained results. A step forward would be the standardization of the aforementioned method to assess the sludge filtration quality.
ABSTRACT
This paper provides an overview of current electric energy consumption of full-scale municipal MBR installations based on literature review and case studies. Energy requirements of several MBRs were linked to operational parameters and reactor performance. Total and specific energy consumption data were analysed on a long-term basis with special attention given to treated flow, design capacity, membrane area and effluent quality. The specific energy consumption of an MBR system is dependent on many factors, such as system design and layout, volume of treated flow, membrane utilization and operational strategy. Operation at optimal flow conditions results in a low specific energy consumption and energy efficient process. Energy consumption of membrane related modules was in the range of 0.5-0.7 kWh/m(3) and specific energy consumption for membrane aeration in flat sheet (FS) was 33-37% higher than in a hollow fibre (HF) system. Aeration is a major energy consumer, often exceeding 50% share of total energy consumption. In consequence, coarse bubble aeration applied for continuous membrane cleaning remains the main target for energy saving actions. Also, a certain potential for energy optimization without immediate danger of affecting the quality of the produced effluent was observed.
