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Characterization of Coliform Bacteria in Drinking Water Treatment Plant

Master thesis project, spring 202

Stockholm Vatten och Avfall (SVOA) is Sweden's largest water and waste management company. Our business affects 1.5 million residents and businesses in and around Stockholm. We provide drinking water and treat the waste water in the city of Stockholm and in the municipality of Huddinge. We are also responsible for the waste disposal in the city of Stockholm.
Our raw water source is Lake Mälaren and every day we are producing 360,000 m³ of drinking water in the two water treatment works of Lovö and Norsborg. It is our responsibility to meet both current and future residents' needs, which we do by making long-term decisions that comply with environmental requirements and with a sustainable cycle in focus.
As the population grows, the production capacity must be increased within the coming decade. One water treatment technique that is being considered for this expansion is based on hollow fiber nanomembranes. These membranes have a pore size that is small enough to retain particulate matter, microorganisms and to some extent dissolved organic matter. To investigate this technique SVOA has been running pilot scale tests with a nanomembrane module and confirmed the technique to be interesting with regards to the water quality that can be achieved.
One risk with using surface water from a busy lake like Mälaren with much frequented waterways is the risk of contamination from petroleum products such as gasoline, diesel and other propulsion oils. In the existing treatment process, this can be mitigated by adding powdered activated carbon, which adsorbs the oil and then sediments in large sedimentation basins.

Project
A potential upside with a nanomembrane treatment step is that it may remove these petroleum products without any use of activated carbon. This project aim at answering the following questions:
• Removal rate of different types of hydrocarbons dissolved in water?
• Are there any negative irreversible effects on the polymeric membrane?
• In order to avoid releasing any separated oils into the recipient lake, what are the possibilities for further treatment of the waste stream?

For testing different petroleum products there is a bench top membrane unit available to compare different oil products with at least one type of hollow fiber nanomembrane module.
One of the interesting analyses would be to look at which kinds of hydrocarbons that are being removed and relate these compounds to odour disturbance in the treated water. After the quantitative analysis of oil concentration being separated, there should be one or more proposals on how the waste stream could be treated before being let back into the recipient lake. Additionally, a manufacturer (Pentair) has proposed to check the membrane surface with EDX and/or SEM to look for residual fouling or other irregularities after the lab tests have been performed.
Due to the ongoing pandemic, none of the work will be conducted at the water works and all meetings are likely to be online. The filtration equipment is quite small and is possible to set up at any suitable location. The project should be performed in a scientific manner and with scientific methods, the results presented in a report and oral presentation.

Application
If you are interested in this project, you should send an application , no later than December 13. Applications will be reviewed on a continuous basis. Do not forget to write why you are interested in this project and what makes you a good candidate.

Questions to Lars-Erik Hägglund (lars-erik.hagglund@svoa.se, 08 522 136 73)