Specific energy consumption of membrane bioreactor
(MBR) for sewage treatment
Pawel Krzeminski, Jaap H. J. M. van der Graaf and Jules B. van Lier
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.
Pawel Krzeminski (corresponding author)
Jules B. van Lier
Department of Water Management,
Section Sanitary Engineering,
Delft University of Technology,
Stevinweg 1,
PO Box 5048,
2600 GA Delft,
The Netherlands
E-mail: p.krzeminski@tudelft.nl
Jaap H. J. M. van der Graaf
Witteveen þ Bos,
van Twickelostraat 2,
PO Box 233,
7400 AE Deventer,
The Netherlands
Key words | energy consumption, energy efficiency, full-scale, membrane bioreactor (MBR), operation,
performance
INTRODUCTION
A membrane bioreactor (MBR) combines biological waste-
water treatment with a membrane separation step. MBR
technology is rapidly developing with an increasing
number of applications and increasing capacity. At present
the number of MBR installations exceeds 800 installations
in Europe alone. The MBR technology is now regarded as
mature and various authors denominate MBR as the best
available technology for industrial but also municipal waste-
water treatment (Kraume & Drews ; Lesjean et al. ).
However, despite these developments, energy demand and
related costs issues are, together with the membrane fouling
issues, major drawbacks that restrict further expansion.
High aeration rates for frequent membrane cleaning
remain a challenge in terms of energy consumption and
optimization of MBRs ( Judd ; Verrecht et al. ).
To research the specific energy requirements of MBRs
and elucidate where possible future energy consumption
reduction can be achieved, extensive research on the
specific energy consumption in several full-scale MBR
plants was performed. This paper provides an overview of
current electric energy consumption of full-scale municipal
MBR installations based on literature review and four case
studies. Moreover, operational processes associated with
aspects of energy are also investigated in this study.
Literature review
In the past 50 years, developments in MBR technology
resulted in an energy demand reduction from about
5.0 kWh/m
3
, needed for the first side-stream MBRs,
to 1.0 kWh/m
3
in 2001–2005 and very recently to about
0.5 kWh/m
3
for the present Zenon submerged MBRs (Buer &
Cumin ). The energy requirement of the first tubular
side-stream MBR installations was reported to be typically
6.0–8.0 kWh/m
3
(Van Dijk & Roncken ), mainly due to
energy intensive cross-flow pumping of the liquid. The intro-
duction of the submerged membranes concept reduces the
pumping energy requirement to 0.007 kWh/m
3
of permeate
380 © IWA Publishing 2012 Water Science & Technology | 65.2 | 2012
doi: 10.2166/wst.2012.861
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