Influence of operative conditions in a hybrid activated sludge/biofilm process for the treatment of municipal wastewater in a cold climate region: a case study

In the last years the idea to combine suspended and attached bomass by introducing suspended carriers into the aeration tank for biofilm attachment and growth was proposed. The increase of the overall sludge age in the system leads to a favourable environment for the growth of nitrifying bacteria, so that nitrification may be maintained throughout the winter. The main aim of the study was to investigate a hybrid MBBR process, mostly in terms of nitrification, when operating with different values of the sludge retention time (SRT), and highlighting the influence of temperature on the process. Based on experience in practice it was hypothesized that nitrification could be maintained at far lo…