Pham Anh Tuan, Master of Science in Environmental Sciences, will defend his doctoral dissertation at Lappeenranta University of Technology on December 9th at 12.00 noon, in the Mikkeli University Consortium auditorium, Lönnrotinkatu 5, 50100 Mikkeli. His dissertation is entitled “Sewage sludge electro-dewatering”. Professor Claudio Cameselle, University of Vigo, Spain, will act as the opponent. Professor Mika Sillanpää of Lappeenranta University of Technology will act as custos.
According to the study, the electro-osmotic dewatering of sewage sludge improved the dewatering performance and reduced the water content in the final sludge cake. However, the improvement of dewatering strongly depended on the sludge characteristics, sludge conditioning, and electro-dewatering properties such as the voltage, pressure and application time. The migration of organic compounds, substrates and metals was observed during the electro-dewatering of sewage sludge.
The original sludge from wastewater treatment plants (WWTPs) usually has poor dewaterability. Conventionally, mechanical dewatering methods such as a centrifuge, belt filter press and pressure filter have been used to remove water from the sludge. However, sludge dewatering is an important economic factor in the operation of WWTPs because high water content in the final sludge cake is commonly related to an increase in transport and disposal costs. Usually, sludge treatment and disposal requires over 50% of the operation budget for WWTPs. Electric field application through the sludge segment causes electro-osmotic flow which has been reported to reduce the water, thus resulting in a dryer sludge cake.
In this research, non-pressure and pressure-driven experiments were set up to investigate the effect of various parameters and experimental strategies on electro-dewatering. The migration behavior of organic compounds and metals was also studied.
In all of the experiments, electrical electro-dewatering obviously reduced the water content of the sludge cake in comparison to blank experiments without the application of an electrical field. The applied voltage was one of the major parameters affecting the dewatering time, water removal rate and DS content of the sludge cake. However, higher voltage application consumes more energy.
Other factors affecting the dewatering performance were associated with the original sludge characteristics and sludge conditioning. The anaerobic digestion of the sludge with a high pH buffering capacity, polymer addition and freeze/thaw conditioning had a positive impact on dewatering. In this study, naturally freezing sludge treatment in Finland’s winter showed great improvement in sludge dewaterability by resulting in low water content in the final sludge cake after electro-dewatering.
One of the differences between electro-dewatering and mechanical dewatering technologies is that electro-dewatering actively removes ionic compounds from the sludge. In this study, the dissolution and migration of metals, and organic and inorganic compounds were observed, which depended on the fractionation and electrical field strength. The migration of these compounds may have both negative and positive impacts on the reuse the sludge. A decrease in the Na/K salts concentration after electro-dewatering is considered as an advantage when the sludge is reused for land application.
This study was carried out at the Laboratory of Green Chemistry, Mikkeli, Finland, with financial support from the European Union, the City of Mikkeli, and the Maa- ja vesitekniikan tuki foundation.
Personal information:
Pham Anh Tuan
Year and place of birth: 1975 in Hanoi, Vietnam
Domicile: Ho Chi Minh City, Vietnam
Education:
1995-1999: B.Sc. in Environmental Sciences at University Hanoi National University - Vietnam
2003-2005: M.Sc. in Environmental Sciences at Wageningen University – Netherlands
2006-present: Ph.D. research at the Laboratory of Green Chemistry, Mikkeli, Finland
Career history:
1999-2003: Consultant in Environmental Center
Biological wastewater treatment from landfill leachate and the food processing industry
- Chemical wastewater treatment from the textile industry
- Feasibility study for an industrial zone’s central wastewater treatment plant
- Environmental Quality Monitoring for Industrial Zones
2005-2006: Consultant in Environmental Center
- Environmental impact assessment (EIA) report for factorys and industrial zones
- Nitrogen removal from wastewater in the food processing industry
- Wastewater treatment and heavy metal recovery of electroplating industrial wastewater
Further information:
Pham Anh Tuan, anh.pham(at)lut.fi or patuanetm(at)yahoo.com
Professor Mika Sillanpää, mika.sillanpaa(at)lut.fi, tel. 0400-205 215
http://urn.fi/URN:ISBN:978-952-265-169-3
Lappeenranta University of Technology ( LUT) has already since 1969 brought together two complementary fields of science – technology and economics. LUT's top strategic sectors are energy efficiency and energy markets, strategic-level business and technology management, scientific computing and modelling of industrial processes, as well as expertise in Russian affairs in the sectors above. LUT has approximately 5 500 degree students and 1 000 employees.