Facilities and Capabilities

Facilities and Capabilities

Continuous Stirred Tank Reactor

The research team use a small scale compact laboratory mixer, also known as a ‘jar tester’ which has four built in stir paddles, which rotate up to an RPM of 250, to accommodate four 1 liter clear plastic rectangular vessels. These 1 liter containers have stopcocks to allow for sample taking at ease. It has a range of functions including coagulation, flocculation and crystallization. In this PolySep Research Laboratory, one of our main goals is to efficiently desalinate brackish water, which involves reducing energy consumption and increasing water recovery. Brackish water typically has compounds like calcium carbonate (calcite) and calcium sulfate (gypsum), which can scale membranes at high concentrations. Membrane scaling typically occurs when they’re beyond the saturation point, and at this point, the brine produced from the RO process can no longer be recycled back into the system for more water production. Our objective is to de-supersaturate the concentrated brackish water from the RO system by precipitating calcite and gypsum through the addition of nucleation sources, also referred to as ‘seeds’. These seeds will collect the supersaturated calcite and gypsum, and can then be filtered out, leaving de-supersaturated brine that can be recycled back into the RO system. The CSTR is used for continuous mixing. First, the antiscalant, a compound that prevents scaling and allows for supersaturation of brine, needs to be deactivated through increasing the pH or adding limestone or soda ash. Seeds are then added to the solution and the CSTR runs continuously for a total of 75 minutes. Measurements are taken through samples taken from the stopcock every 5 minutes. It is expected to see that a larger surface area produces more precipitation given the literature, and the team is currently working towards experimenting with how the amount of lime added, the type of antiscalant and the surface chemistry of the seeds impacts precipitation.

Continuous Stirred Tank Reactor