Outcomes From Microbiome Research

Microbiome research in wastewater can involve some of the following processes:

• Laboratory scale wastewater treatment plants run with experimental conditions
• Sampling full-scale wastewater treatment plants
• Identifying microbial genera and species involved in key wastewater treatment processes
• Identifying reaction pathways of key microbes via methods including, but not limited to, metagenomics, transcriptomics, metabolomics, FISH, staining methods and high throughput sequencing
• Culture based studies, when possible

As we do not currently have a holistic understanding of the microbiome of wastewater treatment, it is important to make a continuous effort to understand it through various combinations of research methods. Usually the knowledge gained from research is applied in order to increase the efficiency of wastewater treatment processes. Often, new knowledge of microbial processes must be trialled and further experimented upon in order to apply it.

Earlier research regarding the identification of polyphosphate accumulating organisms (PAOs) using culture independent methods has been more successful and accurate than culture dependent methods. The study run by Crocetti et al. (1999) was able to identify PAO organisms through FISH with PAO and beta-2 proteobacteria probes and determine that they were beta-2 proteobacteria closely related to Rhodocyclus and Propionibacter. This knowledge and these methods can be applied to further research regarding the identification of PAOs. Furthermore, experimentation with the identified bacteria lead to a correlation between the presence of the probed PAOs and removal of phosphorus, i.e. increasing abundance of identified PAOs lead to increased removal of phosphorus (Crocetti et al., (1999). These findings and the findings of many other studies in this area have worked towards understanding the process of phosphorus removal, the interactions of PAOs with their environment, and how to manipulate environmental conditions to increase efficiency of phosphorus removal.

More current research has been conducted into the process of partial nitrification with in combination of anaerobic ammonium oxidation (Anammox) to utilise the process in wastewater treatment as a more efficient reaction pathway that nitrification and subsequent denitrification. Many techniques have been used to identify and detect ammonium oxidising bacteria (AOB) and nitrite oxidising bacteria (NOB). Polymerase chain reaction (PCR) can be used to amplify the 16S rRNA and amoA genes to identify AOB (Ge et al., 2015). Denaturing gradient gel electrophoresis (DGGE) separates amplified gene fragments by length and was used in municipal activated sludge systems to demonstrate which bacteria were dominant at low-strength ammonium and which would recover under high ammonium and chloride conditions (Ge et al., 2015). Further experimental research has uncovered the effects of changing carbon and nitrogen substrate levels. For optimal operation of partial nitrification, it is recommended that the C/N ratio is lower than 6, organic carbon loading rates are less than 2kh TOC m^3 d^-1, high strength ammonia concentration (Ge et al., 2015). These conditions were found to accumulate the most nitrite from AOB, inhibit NOB and decrease the competition between heterotrophs and autotrophs. This research increases the chances of using partial nitrification in wastewater treatment as a more energy efficient and environmentally friendly alternative.

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References

Crocetti, G., Hugenholtz, P., Bond, P., Schuler, A., Keller, J., Jenkins, D., Blackall, L. (1999). Identification of Polyphosphate-Accumulating Organisms and Design of 16S rRNA-Directed Probes for Their Detection and Quantitation. American Society for Microbiology, 66 (3), 1175-1182. doi: 10.1128/AEM.66.3.1175-1182.2000

Ge, S., Wang, S., Yang, X., Qiu, S., Li, B., Peng, Y. (2015). Detection of nitrifiers and evaluation of partial nitrification for wastewater treatment: A review. Chemosphere, 140, 85-98. doi: 10.1016/j.chemosphere.2015.02.004