1.1 billion People do not have access to clean water. Ground water is increasingly used as source to clean water. The problem is that the ground water resources are decreasing. The world’s water consumptions are increasing because of economic growth, increasing population, climate changes and expansion of agriculture. In some areas the water consumptions are larger than the ground water resources, which result in drying out the ground water. Because of this global water problem, there is a focus on how to save and maintain the water resources. Treatment of waste water and reuse of water has become an important issue in saving the water resources.
Denmark has today 1000 treatment plants to handle all types of waste waters. One of the most difficult types to handle is industrial waste water, which varies a lot depending on industry. Many industries have their own plant, where the wastewater is treated before discharged into sewers, the pump company Grundfos is one of them. Grundfos wish to decrease their water consumptions and reduce the discharged waste water by reusing the waste water.
The purpose of this project is to investigate Forward Osmosis as a method to treat oily waste water from Grundfos´ treatment plan to a quality useful for reuse of the water and also to test different methods to control membrane fouling. Forward Osmosis is a membrane technology with the advantaged in low energy consumptions. The driving force for the process is a difference in osmotic pressure between two solutions. A so called draw solution is used to “draw” water through the membrane. A disadvantaged of this method is in order to reuse the water, an extraction of the permeate from the draw solution is necessary.
Experimental treatment of oily waste water with Forward Osmosis is tested on at small setup, with a flat sheet membrane. Methods to control fouling; increased crossflow, osmotic back wash and chemical cleaning of membrane is tested and compared to a standard experiment. Afterwards the permeate-diluted draw solution is analyses to evaluate the quality of the treated waste water. Flux data are compared with theory by modelling.
Results show that the Forward Osmosis membrane used is very effective in terms of high rejection of impurities and salt and very low tendency of fouling. Fouling is minimal in all experiments and therefore is the effect of the methods to control fouling minimal or not present. The high rejection makes Forward osmosis a promising method for treatment of oily waste water for reuse. With a further extraction of the water from the draw solution with Reverse Osmosis the water quality will be even higher and it is possible to reconcentrate the draw solution for reuse.