One of the major challenges mankind faces nowadays is combating climate change. A substantial fraction of greenhouse gases are released by industrial processes, as steelmaking, (oil)refinery and waste processing. Emissions from these processes can partly be prevented with a recently developed technology called gas fermentation. Within this process, synthesis gas – amixture containing CO, CO2 and H2 – is converted into ethanol and acetic acid by bacteria such as Clostridium autoethanogenum. These products could be used in a wide range of applications, like fuels, plastics and cosmetics. Whilst gas fermentation is already applied at commercial-scale, challenges in scale-up persists due to complex multi-scale interactions among the bioreactor, gas bubbles, and bacteria. The poor solubility of CO and H2 alongside gas bubble coalescence, leads to low gas-to-liquid mass transfer rates (typically denoted via kLa). Slow mixing in industrial bioreactors (500m3), and high gas conversion rates, result in large spatial variations in dissolved gas concentrations. Bacteria experiencing concentration fluctuations have often been related to decreased process performance...

Global freshwater demand has significantly increased over the past century and continued growth is expected in the coming century. Since more than 97 percent of the water in the world is seawater, desalination technologies have the potential to solve the fresh water crisis. Currently, the most used desalination technology is reverse osmosis, where a semipermeable membrane is used to separate the salt from the water. The driving force of reverse osmosis desalination is hydraulic pressure, which has to be greater than the osmotic pressure of the seawater. Due to the high hydraulic pressure reverse osmosis has a high energy demand. Lately, hybrid desalination systems, e.g. indirect desalination with forward osmosis combined with low pressure reverse osmosis are getting more importance. Forward osmosis is also a membrane based process that uses the osmotic pressure difference as driving force. One of the main advantages of forward osmosis is the limited amount of external energy requirement compared to reverse osmosis. The major problem of membrane desalination process is fouling, the accumulation of unwanted material on the membrane surface, causing performance decline and increase of costs. Several types of fouling can occur in membrane processes, biofouling (microbial biofilm formation), scaling (mineral salt precipitation), organic fouling (deposition of organic macromolecules) and colloidal fouling (deposition of particulate matter). In practice biofouling is considered as the major problem in membrane systems.