Using proteomics for an insight into the performance of activated sludge in a lab-scale WWTP

The performance of a lab-scale wastewater treatment plant during the start-up phase was investigated. A period of varying pH resulted in the loss of ammonium removal efficiency together with a decrease in the specific autotrophic oxygen uptake rate (OUR) of the ammonium oxidizing bacteria (AOB). To understand how the AOB were affected at the molecular level, we used shotgun proteomics to quantify the relative protein levels in the system. Label-free quantification (LFQ) showed that during the time of poor ammonium removal, the marker enzyme hydroxylamine oxidase from Nitrosomonas sp. was massively reduced in intensity. The result of this study shows that quantitative proteomics has the potential to be used as a monitoring tool. Nevertheless, there are still some restrictions when measuring activated sludge using proteomic methods such as the availability of a suitable proteomic database. In this paper, we describe our experience of using publicly available databases for identification of activated sludge proteins.