Dewatering of sewage sludge with the help of electric field

Parallel to the increase in water pollution in recent years, studies on the methods of wastewater treatment have increased. To ultimately eliminate the sewage sludge, which is produced as a result of treatment processes of wastewater in great volumes, the water content of the sludge should be decreased significantly. In order to decrease the water content that is present inside the sludge in different forms (free water, interstitial water, capillary water, chemically bonded water), sludge dewatering techniques have been developed. Because, with the method known as mechanical dewatering, which involves pressing the sludge, only the free water is removed from the sludge. For the other forms of water, development of various methods was required. Besides, studies on the methods that would lead to decreased water content in sludge with a lower cost have intensified. One of the methods developed in recent years is the electro-dewatering method. This method is based on the exposition of the sludge that is to be dewatered to an electric field. Electro-dewatering method can be used successfully for various types of sludge that cannot be dewatered by mechanical dewatering such as sludge of fine-particles, and gelatinous sludge. The sustainability of sample electro-dewatering reactor for improving dewaterability properties of sewage sludge was evaluated in this thesis. Capillary Suction Times (CST), Specific Resistances to Filtration (SRF) parameters, Time to Filter (TTF) and viscosity were monitored to determine the effect of electric field. The performance analysis of the system to be placed within a horizontal electric field formed by vertical electrodes was be studied. The assessment of the experimental analysis results by using Box-Behnken Design will be carried out using MINITAB 17.0 computer program. Effect of three independent variables (pH, process time and the applied voltage) on dewatering parameters and chemical changes on sample sludge was evaluated according to statistical design. Additionally, copper electrode, stainless steel electrode and graphite electrodes were used to see the effect of different electrode types. As a result, significant effect on system performance was observed by applying acidic pH, high voltage, and long process time for the all electrode types. It was determined that graphite and copper electrode are more effective than stainless steel electrode. Finally, reducing of distances between the anode and cathode electrodes increased dewatering capacity and the optimum distance of 2.3 cm was identified.