WASTEWATER TREATMENT PROCESS
In order to understand how SINISENS would function in practice, it is important to understand the steps performed in the wastewater treatment plants. As an example, we are going to use Helsinki Region Environmental Services Authority (HSY) facilities (Figure 1).
The influent water has to go through screens and grit removal to separate sand and larger objects. In addition to that ferrous sulphate is added for precipitating phosphorus into the sludge. The next step is pre-aeration, which can help sustain aerobic conditions in the tank, remove oil from water as well as aid in sedimentation process. During primary sedimentation, the number of solids present in water is decreased. The next step in the wastewater treatment process is aeration, which is necessary for aerobic degradation of pollutants by bacteria. Here, most of the nitrogen is released back into the atmosphere. However, it is worth noting that a portion of nitrogen remains in the water flow. The next step includes secondary sedimentation and a biological filter, which ensure that the cells from the previous step will be removed. It is planned to introduce ozonation and activated carbon treatment, where substances such as pharmaceuticals would be removed before the water is released into the sea. SINISENS would be used before and after this step in order to optimize it and make it more energy- and resource-efficient.
SINISENS IN ACTION
We envision our biosensor to be used in wastewater plants as a tabletop device. A small sample of wastewater would be taken out and brought to the device. We decided it is safer to have the sensor outside of the WWTP flow, since our sensor is a genetically modified organism and, in addition to that, carries an antibiotic resistance gene. Since our biosensor would be used for removal process optimization, the sample would be taken out after biological filters, where ozonation and activated carbon-based removal begins, and right before the efflux into the sea. Ideally the device would be reusable, however right now we are aiming for single-use biosensor.
ELECTROCHEMICAL BIOSENSOR: A MORE PROMISING OUTPUT?
When it comes to the output signal, the most sensitive solution and an easier output may involve an electrochemical biosensor. This signal would be generated by Mtr pathway (Fig. 2), which we described in more detailed here.
1. Viikinmäki wastewater treatment plant. (2020). Retrieved 2 September 2020, from http://vara.hsy.fi/hsy/en/experts/water-services/wastewater-treatment-plants/viikinmaki/pages/default.html
2. Yi, H., Li, M., Huo, X., Zeng, G., Lai, C., & Huang, D. et al. (2019). Recent development of advanced biotechnology for wastewater treatment. Critical Reviews In Biotechnology, 40(1), 99-118. doi: 10.1080/07388551.2019.1682964