Comparative studies of different membrane distillation configurations and membranes for potential use on board cruise vessels

Abstract

Cruise tourism industry is expanding worldwide. An average cruise ship produces over 1000 m3 per day of fresh water. To date, multi-stage flash distillation (MSF) and seawater reverse osmosis (SWRO) are the most used desalination technologies on board. However, their application has some drawbacks: a great volume needed on board (MSF), increases of fuel consumptions (SWRO), carbon dioxide emissions and total costs. In this way, membrane distillation (MD) is proposed to overcome limitations of existing conventional technologies. Different configurations (DCMD, AGMD and WGMD) and two membranes (0.45 and 0.20 μm) were tested and compared with each other in order to study potential use of MD on board cruise ships, taking advantage of waste heat generated in the engine cooling system. Operational conditions were established based on an approximation of real conditions encountered in a cruise vessel. Results obtained for simulated and real seawater tests showed advantages for WGMD configuration using PTFE 0.45 μm pore size membrane, reaching a high permeate quality (99.99% of salt rejection) and average fluxes around 13 L m− 2 h− 1, being these similar to those produced by SWRO. In conclusion, use of MD, in the cruise industry, can be a sustainable water production choice that should be considered.