Coagulation of protein in surimi wastewater using a continuous ohmic heater

A continuous ohmic heating system has been developed to coagulate protein from surimi wastewater to reduce the biological oxygen demand of the wastewater. A simple model, based on the energy conservation equation, was used to predict the temperature profiles of the wastewater. Samples were diluted and NaCl solution (10% by wt.) was added to make them suitable for testing in the developed device. All samples were heated under different conditions (electric field strength of 20, 25, and 30 V/cm: flow rates of 100, 200, and 300 cc/min). After heating the samples were centrifuged and the remaining protein in supernatants was measured and compared with the results from the previous batch experiments. Heating under higher electric field strength and lower flow rate values resulted in higher temperatures of samples. The predicted temperature values agreed well with the experimental results. The amount of the remaining protein was also in agreement with that of the previous work. The lab-scale ohmic heating system possessed good performance to coagulate protein (similar to 60%) from surimi wastewater. (C) 2008 Elsevier Ltd. All rights reserved.