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Dewatering of Biological Sludges by an Electrokinetics-Assisted Filter Press System

The objective of this research was to evaluate the technical and economic feasibility of employing an electric field to enhance the dewatering performance of two types of biological sludge by a pilot-scale plate and frame filter press. In this work a biological industrial sludge and biological municipal sludge were collected and tested, respectively. Through the jar testing, it was found that a low molecular weight cationic polymer or medium molecular weight cationic polymer with a dose of 0.008 wt% would yield a satisfactory flocculation for the biological industrial sludge, whereas an iron-based coagulant with a dose of 0.08 wt% would meet the conditioning need of the biological municipal sludge.
To find out the optimal dewatering conditions for the concerned sludges, experimental designs based on the Taguchi method were adopted. More specifically, L8(27) and L18(21¡Ñ37) orthogonal arrays were selected for the biological industrial sludge and biological municipal sludge, respectively. Among others, applied mechanical pressure and time, electrode array, and electrodewatering time were operating parameters of concern. Test results showed that a 10-15% increase of dewatering efficiency for both sludges was obtained for the parallel circuit and parallel series circuit. However, the filtrate quality deteriorated, particularly in pH, turbidity, and chemical oxygen demand. In addition, due to ohmic heating the temperature of filtrate might raise to 80 ¢Jor even higher depending on the operating conditions employed. Thus, the filtrate should be recirculated back to the wastewater treatment system for proper treatment. To find out the significant controlling factors and optimal operating conditions for electrodewatering in a more scientific manner, the final sludge cake moisture and energy consumption for each test was subjected to formal analysis and analysis of variance. For biological industrial sludge, the flocculant type and applied filtration pressure were found to be the most significant controlling factors for the final sludge cake moisture, whereas the applied electric field strength for the power consumption. In the case of biological municipal sludge, however, the electrode array was the most significant controlling factor for both final sludge cake moisture and power consumption. At last, the optimal operating conditions theoretically obtained for electrodewatering were subjected to the respective verification tests for both biological industrial sludge and biological municipal sludge. Test results showed that a final sludge cake moisture of 67.1¡Ó3.9% and energy consumption of 72.6 kWh/ton dry solids were obtained for the former sludge, whereas 68.1¡Ó3.4% and 18.6 kWh/ton dry solids for the latter sludge. These results validated the predictions made by the Taguchi method. Therefore, it may conclude that electrodewatering is technically and economically feasible for treating both biological industrial sludge and biological municipal through the electrokinetics-assisted filter press system employed in this work.

Identiferoai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0303112-173129
Date03 March 2012
CreatorsChen, Min-Cong
ContributorsHsuan-Hsien Yeh, Gordon C. C. Yang, Ching-Jung Chuang
PublisherNSYSU
Source SetsNSYSU Electronic Thesis and Dissertation Archive
LanguageCholon
Detected LanguageEnglish
Typetext
Formatapplication/pdf
Sourcehttp://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0303112-173129
Rightsuser_define, Copyright information available at source archive

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