Gravity Thickening

Intestinal pathogens and parasites are a problem associated with the disposal of sewage sludge to pasture. Those of major importance are ova of the beef tapeworm (Taenia saginata) and Salmonella bacteria. Techniques for routine monitoring of pathogens and intestinal parasite levels in sludge together with design of simple methods for their removal have intensified, because disposal of sewage sludge to pasture is coming under increasing international surveillance. The performance during field trials of a proprietary peracetic acid compound (containing 36 to 40% w/w peracetic acid), hereafter referred to as PAA (100%), is described. These trials under operational conditions showed it to be a suitable bacterial and ovicidal agent for the disinfection of raw, digested and activated sludges. Concentrations ranging from 250 to 1000 mg PAA/l have achieved up to 99% inhibition of hatching and up to 100% destruction in viability of tapeworm embryos suspended in raw and digested sludges. Similarly these concentrations resulted in 5 log reductions in salmonellae seeded in raw sludge. A dose of 250 mg PAA/1 reduced salmonellae levels from 4600 organism/100cm3 to <30/100cm3 during gravity thickening of surplus activated sludge. Results from 46 tanker loads of consolidated surplus activated sludge revealed that salmonellae levels were reduced from 2400 organisms/100 cm3 to <30/100 cm3 at doses of 500, 400 and 300 mg PAA/1. At a lower dose of 150 mg PAA/1 levels were reduced to within a range of <30 to 430 organisms/100 cm3. At optimum disinfection concentrations for the destruction of both bacteria and parasites, PAA was rapidly utilised resulting in safe, readily biodegradable, non-toxic residuals. The technical and practical benefits, principals of disinfecting sludge and ecological safeguards are highlighted in this paper. Use is made of case histories to describe practical operating techniques.

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Studies on the design data of gravity thickening

Water Research ◽

10.1016/0043-1354(72)90139-x ◽

1972 ◽

Vol 6 (4-5) ◽

pp. 499-502 ◽

Cited By ~ 1

Author(s):

K.-H. Kalbskopf

Keyword(s):

Design Data ◽

Gravity Thickening

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Influence d'un préconditionnement chimique sur l'épaississement gravitaire et la déshydratation de boues d'étangs aérés facultatifs

Canadian Journal of Civil Engineering ◽

10.1139/l95-138 ◽

1995 ◽

Vol 22 (6) ◽

pp. 1198-1216

Author(s):

Marc-André Desjardins ◽

Charles Bussières ◽

François G. Brière ◽

Danielle Dagenais

Keyword(s):

Key Words ◽

Capture Rate ◽

Great Difficulty ◽

Solid Content ◽

Cationic Polymers ◽

Dual Effect ◽

Biological Sludge ◽

Gravity Thickening ◽

Chemical Sludge

This article presents the results of a study on the influence of chemical preconditioning on gravity thickening and dewatering of biological and chemical sludge (alum dephosphatation sludge) from facultative aerated lagoons. Four reagents have been studied: two cationic polymers and two inorganic reagents. Inorganic reagents have not improved gravity thickening of sludge while polymers were more efficient. Polymers have a dual effect: they increase capture rate and accelerate solids settling. Biological sludge from lagoons thickens easily and may reach 10 to 12% dry solid contents, with or without the addition of polymers. On the contrary, chemical sludge thickens with great difficulty. Even with the addition of polymers, the maximum dry solid content did not reach more than 3.8% for sludge with initial dry solid content of 1.25% approximately. However, higher dry solid content can be obtained if the initial dry solid content of sludge is higher. Therefore, it is important to minimize dilution during the extraction of sludge from lagoons. Finally, the addition of polymers to sludge to help thickening does not affect the reconditioning of sludge to be dewatered except possibly in the case of mechanically dewatered chemical sludge treated with chemical conditioning. Key words: chemical preconditioning, gravity thickening, dewatering, sludge, facultative aerated lagoons.

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A modified oxic-settling-anaerobic activated sludge process using gravity thickening for excess sludge reduction

Scientific Reports ◽

10.1038/srep13972 ◽

2015 ◽

Vol 5 (1) ◽

Cited By ~ 8

Author(s):

Jun Wang ◽

Shi-Yu Li ◽

Feng Jiang ◽

Ke Wu ◽

Guang-Li Liu ◽

...

Keyword(s):

Activated Sludge ◽

Sludge Reduction ◽

Activated Sludge Process ◽

Excess Sludge ◽

Gravity Thickening ◽

Excess Sludge Reduction

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Aerobic treatment of gravity thickening tank supernatant

Aquacultural Engineering ◽

10.1016/j.aquaeng.2005.06.001 ◽

2006 ◽

Vol 34 (2) ◽

pp. 92-102 ◽

Cited By ~ 12

Author(s):

Brian L. Brazil ◽

Steven T. Summerfelt

Keyword(s):

Aerobic Treatment ◽

Gravity Thickening

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Experimental investigation of Microcystis aeruginosa cyanobacteria thickening to obtain a biomass for the energy production

Journal of Water and Land Development ◽

10.2478/jwld-2019-0069 ◽

2019 ◽

Vol 43 (1) ◽

pp. 113-119

Author(s):

Myroslav Malovanyy ◽

Volodymyr Zhuk ◽

Volodymyr Nykyforov ◽

Igor Bordun ◽

Iurii Balandiukh ◽

...

Keyword(s):

Microcystis Aeruginosa ◽

High Efficiency ◽

Hydrodynamic Cavitation ◽

Concentrated Suspensions ◽

Energy Carriers ◽

Maximum Extraction ◽

Negative Effect ◽

Gravity Thickening ◽

Positive Results ◽

Potential Efficiency

AbstractThe purpose of the presented research is to analyse possible methods of thickening of the Microcystis aeruginosa (Kützing) Kützing cyanobacteria using the obtained concentrate as a biomass for the production of energy carriers and biologically valuable substances. Method of cyanobacteria thickening under the action of electric current and in the electric field, as well as the method of coagulation–flocculation and gravity thickening, was experimentally investigated in labscale conditions. Electrical methods didn't show positive results for the Microcystis aeruginosa thickening, despite the reports of their potential efficiency in a number of previous studies. The high efficiency of the method of coagulation– flocculation and gravity thickening of Microcystis aeruginosa suspensions was obtained. The optimum concentrations of industrial polymeric coagulants and flocculants for the thickening of Microcystis aeruginosa suspensions were defined in the range of about 10 ppm for the coagulants and about 1 ppm for the flocculants. Negative effect of the previous cavitational treatment of the diluted suspensions of Microcystis aeruginosa on the effectiveness of the coagulation–flocculation and gravitational thickening was confirmed experimentally. Hydrodynamic cavitation should be recommended to use after the thickening as the next step of processing of concentrated suspensions of Microcystis aeruginosa to achieve maximum extraction of energy carriers and biologically valuable substances.

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