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Nitrification performance and microbial community dynamics in a submerged membrane bioreactor with complete sludge retention

Paper ID Volume ID Publish Year Pages File Format Full-Text
25779 43599 2006 11 PDF Available
Title
Nitrification performance and microbial community dynamics in a submerged membrane bioreactor with complete sludge retention
Abstract

A submerged membrane bioreactor (MBR) supplied with inorganic ammonium-bearing wastewater (NH4+-N, 500 mg l−1) was operated for 260 days without sludge purge under decreased hydraulic retention times (HRT) through six steps (from 30 to 5 h). Almost complete nitrification was obtained at a volumetric loading rate (VLR) ⩽ 1.2 g NH4+-N l−1 day−1. The sludge nitrification activities were evaluated at each stage. The specific ammonium oxidizing rate (SAOR) decreased from the initial 0.45 to 0.15 kg NH4+-N kg−1 MLSS day−1 in the last four stages, while the specific nitrate forming rate (SNFR) increased from 0.17 to 0.39 kg NO3−-N kg−1 MLSS day−1 at the third stage, and then decreased to below 0.1 kg NO3−-N kg−1 MLSS day−1 from the fourth stage.Microbial population dynamics was investigated by a combination of the MPN method, fluorescence in situ hybridization (FISH) and quinone profiles. During the experiment, although the MLSS increased gradually from 4.5 to 11.5 g l−1, the number of ammonia-oxidizing bacteria (AOB) decreased from 109 l−1 at the third stage to 107 l−1 in the last two stages, and that of nitrite-oxidizing bacteria (NOB) decreased gradually from 108 l−1 at the second stage (HRT of 20 h) to the final 105 l−1. FISH results showed that the active cells decreased gradually with time from about 60 to 20% in the last two stages, and most of sludge was inert cells. The sum of nitrifiers occupied only about 10% of the total bacteria number in the last stage even though only ammonium-bearing inorganic wastewater was fed in. Nitrosomonas sp. and Nitrospira sp. were confirmed by FISH as the dominant nitrifying genera responsible for ammonia and nitrite oxidation, respectively. In the mean time, a small ratio of Nitrobacter sp. also existed in the system. FISH analysis matched better with the batch activity test results than did the MPN techniques. Quinone profiles revealed that the dominant ubiquinone was ubiquinone-8 (UQ-8), ranging from 84 to 66%, followed by UQ-10 of 7–13%, UQ-7 of 3–5% and UQ-9 of 1.6–2.6%. The dominant menaquinone in the MBR was menaquinone-7 (MK-7) followed by MK-6, MK-8 and MK-8 (H2). With the prolongation of operation, the percentage of menaquinones increased from 8 to 14%. The use of the polyphasic approach gave some new insight on variations of microbial community structures.

Keywords
Microbial community structure; Quinone; Fluorescence in situ hybridization (FISH); Nitrifying activities; MBR
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Nitrification performance and microbial community dynamics in a submerged membrane bioreactor with complete sludge retention
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Biotechnology - Volume 123, Issue 1, 3 May 2006, Pages 60–70
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us