The development of small to medium size, autonomous and robust desalination units is needed to establish an independent water supply in remote areas. This is the motivation for research on alternative desalination processes. Membrane distillation (MD) seems to meet the specific requirements very well. This work is focused on experimental studies on full scale demonstration systems, utilizing a parallel multi MD-module setup. Three different plant concepts are introduced, one of them is waste heat driven and two of them are powered by solar thermal collectors. Design parameters and system design are presented. After the analysis of plant operation a comparison among the plants as well as a comparison with laboratory experiments is carried out and discussed. Impact of different feed flow rates, salinities, operating hours and process temperatures are taken into consideration and put into relation. GOR values and specific thermal heat demand are derived and compared. Energy balances of all three plants are given, uncovering heat losses and identifying room for improvement.

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Membrane distillation is getting increasing attention thanks to its advantages in terms of energy consumption and final permeate quality in addition to its resistance against highly corrosive media which forms an appealing solution for industrial wastewater treatment. Despite its advantages, one of the most challenging issues in direct contact membrane distillation (DCMD) is membrane fouling and wetting. In the present research work, saline dairy effluent discharged from hard cheese industry was pretreated by macrofiltration (MAF) and ultrafiltration (UF) and processed by DCMD to investigate the extent of the aforementioned issues. Effluents pretreated by UF have led the best process performance with stable flux values at different operating conditions. Fouling has occurred in all the experiments, though their effect on the flux behavior and membrane wetting was different from one feed to the other. Changing the flow rate and the temperature difference have affected slightly the membrane wettability for all feed qualities. In all experiments, the permeate has maintained a good quality with low electrical conductivity that did not exceed 70 μS/cm and low total organic carbon < 2 mg/L.

In 2030, 47% of the world population will be living in areas of high water stress (UN World Water Development Report 3, 2009). The global water shortage results in an emerging need for novel, more efficient and cost saving water purification methods. Membrane technology with its very low use of chemical substances and secure retention of contaminants represents a promising water cleaning method. The approach presented focuses on the application of nanocoating procedures to membrane processes which aims at reducing the fouling potential of membranes and destroying water contaminants. Photocatalytic titanium dioxide nanoparticles are applied. Novel suitable microsieves including a homogeneous pore size distribution and high robustness were developed from metallic material. An appropriate multilayer coating system was developed and applied on a new nanocomposite filter resulting in high photocatalytic activities with maximum photon efficiencies of 0.0733. The coating layer do not have a negative influence on the permeate flux. The effectiveness of the nanocomposite filter was proven in a 12 days biofouling experiment with activated sludge suspensions.