Abstract:
Pakistan is currently experiencing water shortage as population is growing. The problem associated with the reverse osmosis is its brine disposal. Experimental salinity gradient solar pond (SGSP) with surface area 4.65m2 was established to pre-heat the reverse osmosis (RO) concentrated brine. Laboratory scale direct contact membrane distillation (DCMD) setup was used to investigate the temperatures gained from (SGSP). In this study, effort has been made to evaluate the performance of the SGSP and DCMD under Pakistan's climatic condition at NUST, Islamabad. The heat extraction was carried out using internal heat exchanger by passing fresh water through it at different flow rates in summer and winter. Maximum of 37°C of heat extracted temperature in summer and 28.5°C in winter was achieved. Least drop in lower convective zone (LCZ) temperature was observed at flow rate of 7.5L/min. In DCMD, four different temperatures (28.5,
37, 50 and 60) oC at feed side were maintained to observe flux and total dissolve solids (TDS). Flux was increased as temperature difference between feed and permeate increased. As salt concentration was increased in feed side, scaling and decrease in flux was observed. Experiment showed that 28.5°C in terms of SGSP temperature is also feasible for membrane distillation process as flux was increasing with passage of time.
