The Electrodewatering of Sewage Sludges

Barton, Wesley A.; Miller, Sandra L.; Veal, Christopher J.

doi:10.1080/07373939908917548

Cited by 92 publications

(39 citation statements)

References 13 publications

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“…Seeking new and efficient methods for dewatering, many authors (Yoshida, 1993;Barton et al, 1999;Gingerich et al, 1999) exploited electro-osmosis in order to improve water removal from sludge, being the resulting process usually defined as electro-dewatering (EDW). The application of an electric field, sometimes in combination with pressure, seems capable to increase the DS content in sludge up to 45%, much higher than the values commonly achievable by mechanical methods (Mahmoud et al, 2010;Weng et al, 2013;Feng et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Performance of electro-osmotic dewatering on different types of sewage sludge

Visigalli

Turolla

Gronchi

et al. 2017

Environmental Research

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A B S T R A C TThe feasibility of pressure-driven electro-dewatering (EDW) on sludge samples taken after different biological processes, stabilisation methods or mechanical dewatering techniques was assessed. First, the influence of potential values on EDW of anaerobically and aerobically stabilised, mechanically dewatered, sludge samples was investigated. Preliminary tests carried out by applying a constant potential (10, 15 and 20 V) in a lab-scale device confirmed the possibility to reach a dry solid (DS) content of up to 42.9%, which corresponds to an increase of 15% of the dry content in dewatered sludge without the application of the electrical field. Dewatering increased with the applied potential but at the expense of a higher energy consumption. A potential equal to 15 V was chosen as the best compromise for EDW performance, in terms of DS content and energy consumption. Then, the influence of the mechanical dewatering was studied on aerobically stabilised sludge samples with a lower initial DS content: the higher initial water content led to a lower final DS content but with a considerable reduction of energy consumption. Finally, the biological process, studied by comparing sludge samples from conventional activated sludge and membrane bioreactor processes, didn't evidence any influence on EDW. Experimental results shown that DS obtained after mechanical dewatering, volatile solids and conductivity are the main factors influencing EDW. Anaerobically digested sludge reached the highest DS content, thanks to lower organic fraction.

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Section: Introductionmentioning

confidence: 99%

“…Although chemical-physical phenomena involved in pressure-driven EDW are not fully understood yet, many authors suggest that water is removed from sludge according to the following processes (Barton et al, 1999;Mahmoud et al, 2010;Mok, 2006):…”

Section: Introductionmentioning

confidence: 99%

Performance of electro-osmotic dewatering on different types of sewage sludge

Visigalli

Turolla

Gronchi

et al. 2017

Environmental Research

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“…Seeking new and efficient methods for dewatering, Yoshida [ 1] , Barton et al [ 2 ] , Gingerich et al [3] exploited electro-osmosis in order to remove water from sludge: the application of an electric field, sometimes in combination with pressure, seems capable to increase the DS content well beyond the values that can be achieved by mechanical means [4]. Among electrokinetic phenomena, electro-osmosis rules this process and leads to a transport of water molecules to the negative electrode (cathode), increasing the dry matter significantly and lowering the energy consumption with respect to conventional techniques.…”

Section: Introductionmentioning

confidence: 99%

Electrode surface treatments in sludge electro-osmosis dewatering

Gronchi

Canziani

Brenna

et al. 2017

Materials and Manufacturing Processes

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The sewage sludge dewatering produced by Wastewater Treatment Plants is a multifaceted process due to the presence of colloid fractions. Electro-osmosis could be a suitable technique to reduce the water content of the final sludge. Electric fields of 10 V/cm, 15 V/cm and 20 V/cm have been studied for electro-osmosis tests under the pressure of a static or rotating piston, obtaining a dry solids content up to 40-45%, with respect to 25-30% obtained by mechanical methods. In order to optimise the process, the corrosion behaviour and the wear of the anodic material appear the main critical aspects, due to the high circulating current density and the use of a rotating electrode. We compared the efficiency and the corrosion resistance of dimensionally stable anodes (DSA) with respect to bare stainless steel (AISI 304) and stainless steel coated by PVD technique with TiN, AlTiN and DLC. Characterization of the anode surfaces by SEM and potentiodynamic tests, show that DSA is the most suitable material for our application. However, efficiencies of the electro-osmosis processes have been found comparable, in terms of developed current densities and total energy consumptions, for short-test duration.Keywords: electro-osmosis; dewatering; sludge; DSA; anode; corrosion. IntroductionThe so-called "activated sludge process" is adopted by almost the totality of urban and industrial wastewater treatment plants to achieve the concentration limits of biodegradable pollutants stated by the law to allow the discharge of treated effluents to natural water bodies (rivers, lakes and the sea).About half of the organic pollution load treated by the activated sludge process is oxidised and converted into water and carbon dioxide, while the remaining is converted into biomass, called "excess biological sludge" or "waste sludge". After reducing both the content of biodegradable matter and the water content through mechanical dewatering or thermal drying, the sludge becomes a product suitable for its final disposal.When compared with thermal (evaporative) processes for water reduction, mechanical dewatering is often selected due to its low energy requirement. The processes of mechanical dewatering are largely developed on the industrial scale and can produce sludge with 20-25% of dry solid (DS) content and, in some cases, up to 30%. However, the high DS values demanded for thermal valorisation of sludge cannot be achieved by mechanical dewatering techniques. , and Tuan et al. [10] reported that the pH drop relates to the reduction of the absolute value of the zeta potential, thus the decrease in pH (specifically at the anode) reduced the electro-osmotic flow during direct current application [1, 5,8,11].The oxidation of the anode material, due to oxygen evolution, ohmic heating and pH decrease, reduces the process efficiency [12] and can cause in some applications the contamination of the filter cake or filtrate, increasing the operating cost. Anodes such as stainless steel will be subject to

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“…Although only slight increases in the kinetics of washing have been reported 2 , the situation can be quite different when the removal of specific ions is measured 3 . Electro-osmotic flow of ions in porous systems under the action of an electrical field is of practical interest for soil stabilisation 4 , contaminated soil remediation [5][6][7][8][9] the dewatering of tailings ponds 10,11 and the dewatering of sewage sludge [12][13][14][15][16][17][18] .…”

Section: Introductionmentioning

confidence: 99%

Transport processes during electrowashing of filter cakes

Kilchherr

Koenders

Wakeman

et al. 2004

Chemical Engineering Science

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Applications of electric fields during washing of filter cakes increases the removal rate of ions from the cake mother liquor, and under appropriate conditions the field also increases the wash flow rate by electroosmosis. Experimental data that show the key effects of the fields on the rates of ion mass transfer are presented: with the downstream electrode acting as a cathode, cation removal rates are increased whilst the removal rate of the anions is decreased. The concentration profile of the cations with washing time shows an increase in concentration to a value above that of the mother liquor, before it decreases due to displacement by the fresh wash liquor. A model is formulated that describes the advection, dispersion, ion migration and electroosmosis transport processes in the cake. Numerical solution of the model gives cation concentration profiles at the exit of the cake that are in qualitative agreement with the experimental observations. Experimentally measured wash liquor flow rates tend to be lower than what traditional colloid science principles predict by a factor of 5 to 10: reasons for this difference, supported by experimental work from other researchers, are discussed.

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The Electrodewatering of Sewage Sludges

Cited by 92 publications

References 13 publications

Performance of electro-osmotic dewatering on different types of sewage sludge

Performance of electro-osmotic dewatering on different types of sewage sludge

Electrode surface treatments in sludge electro-osmosis dewatering

Transport processes during electrowashing of filter cakes

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