Studies on membrane distillation towards mitigating thermal pollution

Abstract

Thermal energy is lost in many industries including thermal power stations through the return cooling water requiring additional costs and efforts to ensure compliance with environmental regulations. Membrane distillation (MD) utilises the waste heat, available in the discharge streams, to produce purified water and reduce of temperature of the feed stream. Several studies on membrane distillation have focussed their investigations on improving desalination performance utilising different types of membranes and process conditions. However, considering its potential to reduce the temperature of the hot streams, an opportunity can be sensed to attain the twin objectives of reducing the discharge temperature and producing purified water. Experimental investigations have been undertaken in this context, to assess the potential of membrane distillation to achieve the objectives of environmental compliance through temperature reduction and production of desalinated water. Polyvinylidene fluoride–polytetrafluoroethylene (PVDF–PTFE) blend membranes have provided permeate flux in the range of 0.0043–0.0194 kg/m2s on par with the results reported in literature with substantial reduction in temperature in a range of experimental conditions with respect to feed concentration and entry temperature. Integrity of the membrane was assessed based on structural and morphological studies using SEM, XRD and FTIR, before and after the use of membranes. The studies bring out the latent benefits of the membrane distillation as an eco-friendly value addition process.