Forward osmosis (FO) is a well-established process that has been used for different applications like desalination of water, concentration of foods or drugs, and energy harvesting. We exploited this process in a fully automatic system to adjust osmolality of environmental water samples that are to be tested by cell-based biosensors. In cell-based biosensors, samples are brought into contact with living cells. Therefore, the samples osmolality and should be in a range that is tolerable for the cells. Controlling these parameters has been a significant challenge especially in environmental monitoring, where the biosensors are required to work on-site. In this paper, we introduce a low-cost portable fluidic system that works automatically, and adjusts the osmolality and pH of environmental samples without diluting or denaturizing the ingredients of the samples. We report the performance of this system in adjusting the osmolality and pH of Swiss environmental waters with a natural osmolality of 4 1 mmol/kg and a pH of 7.84 +/- 0.02. (c) 2013 Elsevier B.V. All rights reserved.