Page 31 - March 2020 - WT Site

presence of 36 phyla, 293 families, and 579 genera in four WWTP
activated sludge samples.

In case of wastewater, microbes can be either in suspension or
in attached form. However, in both cases there are billions of
organisms and thousands of species contributing to community
structure. These communities are built according to the
environmental conditions and substrate available.

Figure 1: Illustration for understanding microbial community structure. The relative abundances of Saprospiraceae, Flavobacterium
and Tetrasphaera with the respective averages of 12.0%, 8.3%,
When microbial community present in wastewater comprises and 5.2% in bulking sludge samples were higher than those in
single or only two types of microbial population, they are referred normal samples. Presence and high percentage of Filamentous
to as less diverse population. The population present are called Saprospiraceae, Flavobacterium and Tetrasphaera was the main
“Dominant population” of the community. Such features, types cause for the sludge bulking (Xu et. al., 2018; Volume 2018, Article
of population and their numbers are called as structural features ID 8278970, 8 pages https://doi.org/10.1155/2018/8278970).
of microbial community. Wastewater treatment plants with such
dominant species will not be able to utilize variety of substrate The composition of a microbial community and the abundance
coming in treatment plant. Thus, even if they are detected in of its members also indicate functional capacity of treatment
the range of 1011 to 1012cfu/ml will not contribute to effective plant community. When we can identify the abundant bacteria
treatment of incoming waste. present in the wastewater over all seasons, it can be then
augmented to take care of difficult pollutant (Zaveri et al, 2015).
According to one of the researches carried out for 12 municipal In that study, 9 CETPs were studied for long period of time
wastewater treatment plants having different treatment and the functional community diversity analysis was conducted.
processes, using 454-pyrosequencing technology they found Highly even community structure and rich diversity of microbes
nearly 202,968 effective sequences of the 16S rRNA gene. were found to contribute to efficient treatment of the plants.
This indicates that all the samples investigated represented the
vast diversity of the microbial communities. The major parameters which influence microbial community
compositions are pH, dissolved oxygen, concentration of
Proteobacteria was found to be the dominant phylum in some contaminant and various nutrients. As we all know it is
samples, in other samples it was Bacteroidetes (Hu et. al., difficult to take care of influent quality due to practical field
2012; https://doi.org/10.1016/j.biortech.2012.04.061). Such conditions.
kind of details, will give insight to professionals to redirect
community structure to get more diverse and efficient. In such conditions, if microbial community is supplemented
with additional nutrient which has suppressive effect (but not
At times, using simple techniques like microscopy even gross killing effect as antibiotic) will lead to immediate response
idea of microbial community can be achieved. However, the of species survival. For example, at times higher levels of
correlation of such microscopic images with treatment plant phosphate can divert microbial metabolism to other direction,
health is under study by our research group. which can be compensated by addition of additional ammonical
nitrogen.
The microbial community structure if studied in detail can lead
to meaningful insights. Sludge bulking is one of the major issues The microbial community doesn’t form on the day of
encountered in winters by treatment plants. When a research commencement of plant. That is why we see the lag phase in
group focused on the microbial community analysis, they found achieving treatment efficiency. Also, once formed it is not

Water Today - The Magazine l March 2020 33