The biological process known as activated sludge (AS) in conjunction with
membrane separation technology for the treatment of wastewater has been
employed for over four decades. While, membrane biological reactors (MBR) are
now widely employed, the phenomenon of membrane fouling is still the most
significant factor leading to performance decline of MBRs. Although much research
has been done on the subject of MBR fouling over the past two decades, many
questions remain unanswered, and consensus within the scientific community is
rare. However, research has led to one system parameter generally being regarded
as a contributor to membrane fouling, extracellular polymeric compounds (EPS).
EPS, and more specifically, the soluble fraction of EPS known as soluble microbial
products (SMP), must be further investigated in order to better understand
membrane fouling. The biological activity and performance of the MBR is affected
by myriad operational parameters, which in turn affects the SMP generated. A
commonly varied operational parameter is, depending on the specific treatment
needs of a MBR, the sludge retention time (SRT). This study aims to characterize the
SMP in three bench-scale MBRs as the SRT is gradually lowered. By studying how the SMP change as the operation of the system is altered, greater understanding of
how SMP are related to fouling can be achieved. At the onset of the study, a steady
state was established in the system with a SRT of 20 days. Upon stabilization of a 20
day SRT, the system was gradually transitioned to a five and a half day SRT, in stepwise
adjustments. Initially, both the trans-membrane pressure (TMP) and the SMP
concentrations were at relatively low values, indicating the presence of minimal
amounts of biofilm on the membrane surfaces. As the system was altered and more
activated sludge was wasted from the reactors, the SRT inherently decreased. As
the lower SRT was transitioned and established, the data from TMP measurements,
as well as the results from SMP determination, confirmed the development of
increased amounts of biofilm formed. An apparent relationship was observed
between the operational condition of a lower SRT and the SMP found in the system.
| Date of Award | Dec 2012 |
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| Original language | English (US) |
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| Awarding Institution | - Biological, Environmental Sciences and Engineering
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| Supervisor | Gary Amy (Supervisor) |
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