High throughput 16S rRNA gene amplicon sequencing: A fast and cheap method to study the influence of microbial community composition on activated sludge floc properties

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Abstract

A reliable and reproducible method for identification and quantification of microorganisms is important for the studies of microbial communities in activated sludge and for the demonstration of their significance for plant operation and stability. DNA based identification of microorganisms using 16S rRNA gene amplicon sequencing has been developed over the past few years and is now ready to use for more comprehensive studies related to plant operation and optimization thanks to short analysis time, low cost, high throughput, and high taxonomic resolution.
In this study we show how 16S rRNA gene amplicon sequencing can be used to reveal factors of importance for the operation of full-scale nutrient removal plants related to settling problems and floc properties. Using optimized DNA extraction protocols, indexed primers and our in-house Illumina platform, we prepared multiple samples in a reproducible manner that makes amplicon sequencing together with multivariate statistics a tool that provides a fast link between microbial community structure and function.
Example 1 concerns the control of bulking sludge. A full-scale wastewater treatment plant (WWTP) with severe bulking problems due to the presence of filamentous microorganisms was monitored weekly over 4 months. Microthrix was identified as a causative filament and suitable control measures were introduced. The level of Microthrix was reduced after 1-2 months but a number of other filamentous species were still present, with most of them belonging to the phylum Chloroflexi. Based on knowledge about their ecophysiology, other control measures were introduced and the bulking problem was reduced after 2 months. Besides changes in the filament abundance and composition also other changes in the microbial community were observed that likely contributed to the improved floc structure.
Example 2 concerns activated sludge floc structure and properties. It was investigated whether the floc properties could be correlated to the presence of particular bacterial species. A number of properties related to activated sludge flocs and sludge settling was correlated with the bacterial species composition in 25 Danish full-scale WWTPs with nutrient removal. Examples of properties were SVI, filament index, floc size, floc strength, content of cations and amount of extracellular polymeric substances. Multivariate statistics provided several important insights such as 1) A large core community consisting of the same (approximately 100) species was present in all the plants, although in different relative abundances; 2) Settling properties could be correlated to the presence of both filamentous and non-filamentous bacteria; 3) Floc size and floc strength could be correlated to the presence of the species that are regarded as “strong” and “weak” floc formers.
In conclusion, 16S rRNA gene amplicon sequencing provides a high throughput approach for a rapid and cheap community profiling of activated sludge that in combination with multivariate statistics can be used to reveal important correlations that provide solutions for plant operation problems and can contribute to process performance optimization.
Original languageEnglish
Publication dateJun 2014
Publication statusPublished - Jun 2014
EventActivated sludge - 100 years and counting - Essen, Germany
Duration: 12 Jun 201414 Jun 2014

Conference

ConferenceActivated sludge - 100 years and counting
Country/TerritoryGermany
CityEssen
Period12/06/201414/06/2014

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