Geotube® Hanging Bag Trials Depending upon the nature of the raw sludge it is preconditioned with anionic or cationic polymers and/or coagulants and then pumped into a hanging bag to ascertain it’s dewatering rate. Measurements from the top of the bag are taken over a period of time to indicate the ease with which the sludge dewaters. Filtrate samples from the bag can also be taken and analysed. Hanging bags are designed to closely represent the same static head pressure as a mid sized Geotube® container, so results can be extrapolated quite closely. The data gained from the hanging bag trials enables CRS engineers to design a system to suit the application exactly. The hanging bag test is generally undertaken on site so as to ensure a representative sludge sample as well as allowing the opportunity to assess site suitability for full scale implementation of a Geotube® dewatering system.  Hanging bag trials are established to determine the correct chemical pre-treatment of a sludge and to evaluate it’s subsequent dewaterability within a Geotube® dewatering container.