After settling for approximately 2–5 min while preparing for pumping, the mixture was pumped to the filter press by a diaphragm pump and the content in the holding tank was periodically stirred gently without breaking the flocs to avoid excessive settling. At the initial stage the pumping rate was controlled by adjusting the air pressure to the diaphragm pump. As the pressure built up inside the filter chambers, the pumping rate reduced over time. The pressure profiles during the dewatering process are shown in Fig. 2. The filtrate forced through the weave in the filter cloth was collected and weighed periodically during the process. For the tests with high dewatering rate (optimum flocculation with lignite conditioning), the filtration process was terminated when the mass of the filtrate collected over a period of 10 min was 0.1–0.5 kg. When the dewatering rate was low for the tests without lignite conditioning or under-flocculated, the runs were stopped after 3–4 h. After the pressure was released, the solid cakes inside each chamber were removed from the filter cloth and weighed. The solids were homogenised prior to sampling for moisture content measurements.