SLUDGE TREATMENT AND GAS LINE

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Prof. Dr. D. A. Aznar JimProf. Dr. D. A. Aznar JimééneznezProf. Dr. D. JC Cabanelas ValcarcelProf. Dr. D. JC Cabanelas ValcarcelProf. Dra. Berta Herrero Prof. Dra. Berta Herrero AyestarAyestaráánnDpto. C. e I. Materiales e I.QuDpto. C. e I. Materiales e I.Quíímicamica

UNIVERSIDAD CARLOS III DE MADRIDUNIVERSIDAD CARLOS III DE MADRID

SLUDGE TREATMENT AND

GAS LINE

Sludge is removed from the primary and secondary treatments. After removal, sludge is dehydrated and must be disposed of by an authorised company. The final used of sludge depends on the chemical and biological contents, as happens with waste in general.

Waste produced is classified as:

-Toxic and Dangerous Hazardous Waste (corresponding to ResiduosTóxicos y Peligrosos – RPTs).

-Municipal Solid Waste and Non-Hazardous Waste (corresponding to Residuos Sólidos Urbanos - RSUs).

Usually sludge is classified as Hazardous Waste.

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Water line

Sludge line

Gas line

Pretreatment

Primary treatment

Secondary treatment

TREATMENT PLANT OVERVIEW

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TREATMENT PLANT

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Sludge treatment

Thickening

Stabilization/ digestion

Dehydration

Final disposal

Thickener (10-15%)

Aerobic

Anaerobic

Drying beds (40-45%)

Band filters (35-40%)

Vacuum filter (20-30%)

Press filter (60-70%)

Centrifuge (20-30%)

Driers (80-90%)

Landfill

Incineration

Controlled dumping

Sea discharge

Compost and vitrification

SLUDGE TREATMENT

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SLUDGE THICKENER (FLOTATION)

Sludge from the secondary treatment is also thickened after removal. The mechanism is flotation.

Thickening by sedimentation was performed for sludge produced in the primary treatment (note the different design).

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SLUDGE THICKENER:

REMOVAL

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SLUDGE THICKENER:

BAFFLE

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SLUDGE PUMPS

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GAS LINE: ANAEROBIC DIGESTERS

Anaerobic digesters at the bottom of the image, gasholder in front.

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CnHmOpNrCO2

H2O

NH+4

S=

R-COOH

ACIDOGENESIS(FERMENTATION)

R-COOHCO2

H2O

CH3-COOH

ACETOGENESIS

CH3 -COOHCO2

H2O

CH4

METHANOGENESIS

Symbiosis

ANAEROBIC METABOLIC PROCESS

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reliefvalve

The relief valve on top of the digester prevents an increase of pressure exceeding design values. Some space for the gas is allowed at the top of the dome.

ANAEROBIC DIGESTER:

RELIEF VALVE

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Affluent Effluent

• Closed systems (No O2)

• τr (anaerobic) > τr (aerobic)

• Cm (anaerobic) > Cm (aerobic)

• Te (anaerobic) ≥ Te (aerobic)

• Sludge production ↓

• Biogas production

Gases

HIGH LOAD ANAEROBIC DIGESTERS

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Qsludge (m3/h) =sludge

QSS

SS sludgedigester

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SSvsludge (kg/d) = 100][· inputvsludgev SSSSSS =

CSSv (kg/m3d) =digester

input

SSv V

SSSSC 100

][·sludger

=

φinner (m)= ( ) ( )12·4· backgfree

digesterinner HH

Vππ

φ+

=

Vdigester (m3) = sludgeresidencedigester QtV ·=

tresidence = 10-30 h Hfree (m) Hbackg (m)

[SSV]input= 40 – 70 % SSV Reduction = 30-60 %

Qsludge (m3/h) SSsludge(kg/d)

DESIGN PARAMETERS OF

A HIGH LOAD ANAEROBIC DIGESTER

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Effluent

Gases

Digested sludge Sludge digestion

Clarified liquid

Affluent

tRH ≈ tRS (30-60 days)

Mass load (Kg COD/m3/d): 0,4-1,6

There are no mixing devices. Small turbulence created by the gas bubbles produced.

Raw liquid enters through the digestion area.

Feeding influent must include anaerobic bacteria (manure).

A foam layer is formed at the surface favored by the ascending gas that carries sludge and floating mat.

Digested sludge and supernatant is periodically purged.

57-85 l/hab sludge 1ry 113-170 l/habsludge 1ry+ active sludge.

Free reactor volume = approx 50% total digester volume.

LOW LOAD DISCONTINUOUS

REACTOR

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GASHOLDER

Gasholder sometimes called gasmeter.

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10-20%

2-5%

30-70%

10-50%

1-3%

1-3%

1-2%

•Pumping

•Primary sedimentation

•Active sludge

•Sludge processing

•Electricity, monitoring, controls

•Disinfection

•Odor control

ENERGETIC CONSUMPTION

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TORCH

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THICKENER: FLOCCULANT

ADDITION

• Flocculants may be

needed to enhance

thickening

• The image shows the

proportioner

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DEHYDRATION: BELT FILTER

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DEHYDRATION: BELT FILTER

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DEHYDRATION: BELT FILTER

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DRY SLUDGE

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SLUDGE STORAGE

• Sludge is stored

temporarily.

• Disposal must be

performed by an

authorized company

• Sludge may be

hazardous waste!