choosing a topic for dissertation in MSC?(DISTILLATION OR DISALINATION)

How about Membrane Bio-Reactors? Untreated sewage to potable water in one, energy intensive and low footprint step...

Unless you live in the tropics or have money to burn neither is a good way to purify water. Reverse osmosis used huge amounts of energy (pumps) and does not remove things like bacteria/viruses. You need active UV and or Chlorine ozone for that.

The idea of distilation only works if you have plenty of waste heat to use.

Nuclear power? Solar still? It also depends on where you source your water from and how much salt content it has. There are far too many factors to answer your question in any more detail.

MBRs are widely used in Japan, are beginning to make inroads into the USA and are not unknown in European countries. The head needed to drive one is in the order of 1-2 metres, as compared to 10-65 Bar for a "traditional" RO, depending on water source. The principal driver for MBR technology is to intensify wastewater treatment so as to radically increase the capacity of a works without significant additional land-take - an attractive possibility for districts with an expanding population and high values/constraints on land. A mathematical model of the benefits would form an interesting basis for a dissertation, and may attract the support of potential sponsors looking to commercialise the technology in their localities. This is the domain of the MSc.

RO and evaporation are widely used offshore and on ocean-going vessels, where the needs drive the process. There is little call for MBRs there.

UPW.. Ultra Pure Water used by the semi-conductor industry would be a good and useful topic . Si and other contaminates can kill wafer yields and drive production costs up plus limit how small chips can be made. The process of purifying the water is constantly being improved and the technology to detect low level contaminates is rapidly moving forward as well. Right now TOC is measured in the lower ppt levels, 0.05 micron particle levels are kept below 200 counts per liter and the lasers and detector (used to detect particles) are improving.

While one may take a quick overlook of a UPW plant and only see RO's and Mixed ion exchange beds, there is a great deal more.

I happen to have an interest in the treatment of waste hydrofluoric acid. the system I work with is capable of treating a 10,000 ppm solution at a constant flow rate of 150 gpm thought it normally runs with concentrations of 500ppm at a rate of 60gpm. The treatment process includes pH adjusting, addition of calcium chloride and a long chain molecule polymer to form Calcium fluoride that is precipitated from solution. the calcium fluoride is decanted then put into a filter press for further de-watering. the resultant filter cake is recycled as a component of cement. The water is discharged to the city basically as salt water.

BrainWave hits on a good point as well. Energy efficiency, RO's do consume huge amounts of power as does distillation. What energy efficient methods exist, how can they be applied, what are there limits. All good topics.

I hope this gives you at least a couple ideas.

While UPW is no doubt a very interesting topic (an UPW plant in East Kilbride built 1994, for example, uses 17 stages of processing to get from Town Mains to UPW) it could be recognised as established technology that responds well to design calculation.

MBRs are probably still on the ascent, with technology still under-evaluated and commercialisation still to be fully realised. As such it is possibly a more attractive candidate for an MSc dissertation?