Context
Higher pressure on water sources, combined with more frequent droughts, potentially calls for a different view on wastewater, and for increased reuse. To achieve a reusable water, a safe removal of pathogens is needed.
Gap
Granular activated carbon (GAC) is commonly used for drinking water treatment, and increasingly used in advanced wastewater treatment. The development of a biofilm on the granules potentially affects the bacterial community in the effluent and the reuse potential (Kantor et al., 2019; Miller et al., 2020; Vignola et al., 2018). To safely and efficiently use GAC filters for reuse purposes, more knowledge is needed on how the biofilm develops and affects the microbial and chemical water quality.
Aim
The aim of this study is to understand how the bacterial community in a wastewater GAC filter develops and affects the effluent overall water quality.
Methods
E.coli, total coliforms and flow cytometry tracked changes in bacteria across a full scale wastewater treatment plant consisting of pretreatment with disc filters (40 µm), a membrane bioreactor (MBR, 0.038 µm), followed by two parallel GAC filters, has been studied since start-up (December 2020).
Findings
Total cell and intact cell concentrations decrease after both the disc filters and MBR, but increase after the GAC filters. E.coli and total coliforms decrease after the disc filters, after the MBR, and after the GAC filters. Thus while there is bacterial growth in the GAC filters, it does not seem to consist of E.coli or other coliforms. Bacterial composition, in the GAC filter and the effluents, also changes over time (Figure 1).
Utilization
That GAC filters increase the total cell count without increasing the number of E.coli or total coliforms, suggests a selection of bacteria that are not necessarily harmful. An established biofilm could potentially stabilize variations in the incoming water, and remove harmful substances.
Figure 1.
