SANITARY ENGINEERING PRESENTATION

THE GROUP MEMBERS ARE,

TESSY S ALEX (UR12CE115)

ANJALI KUMARI (UR12CE013)

SURENDAR N (UR12CE111)

SUJITH ALEN S (UR12CE110)

JAESON ANTONY A (UR12CE046)

TOPIC :

SLUDGE TREATMENT

UNIT – IV Sewage Disposal and Sludge ManagementMethods of sewage disposal, sewage farming

Sewage sickness and its preventive measures

Final products in Sludge Digester : stagesFactors affecting sludge digestion and controlDesign of sludge digestion tank

Sludge thickening

Sludge conditioning and dewatering

Final disposal of digested sludge

Bioremediation: constructed wetlands, stabilization pond

Self purification and oxygen sag curveAnalysis

INTRODUCTION

Secondary

OrganicInorganic

Wastewater PreTreatment

RockGritPlasticEtc.

PrimarySedimentation Tank

SettleableSuspendedDissolved

SuspendedDissolved

SecondarySedimentation Tank

Effluent

Digester

Sludge

SludgeGas

Digested SludgeRecycled Water(Supernatant)

(Stabilized)

Pre treatment

• Screening-for removal of objects Eg: wood logs ,cloths, chappals etc….

• Grit Chamber For removing high density inorganic particles by discrete settling principle Eg: Removal of sand, silt etc….

• Primary settling tank For removal of low density organic

solids

Post treatment

• Secondary settling tank-for biomass settling.

• Sludge from primary and secondary settling tanks is sent to sludge treatment unit.

WHAT IS SLUDGE ?

SLUDGE IS THICK MUD , SEWAGE OR INDUSTRIAL

WASTE .

SLUDGE

The SETTLEABLE solidsseparated from liquids

During processing.

FROM WHERE THE SLUDGE IS

COLLECTED?

FROM PRIMARY AND SECONDARY SEDIMENTATION

TANK .

WHY DO WE TREAT

SLUDGE WHICH IS IN SEDIMENTATION TANK?

SLUDGE DISPOSED BARELY

DECOMPOSITION OF ORGANIC MATTER

FOUL SMELL

ENVIRONMENTAL POLLUTION

HOW TO STABILIZE SLUDGE?

[ ODOURLESS , DISPOSABLE IN NATURE WITHOUT POLLUTING OR

HARMING ]

SLUDGE IS STABILISED BY DECOMPOSING THE ORGANIC MATTER UNDER CONTROLLED

ANAEROBIC CONDITION.[The decomposition of organic and inorganic matter in the absence of molecular oxygen.]

WHAT IS KNOWN AS

SLUDGE DIGESTION?

THE PROCESS OF STABILISATION OF SLUDGE IS CALLED

THE SLUDGE DIGESTION.

THE MAIN TOPICS TO BE DISCUSSED IN THIS PRESENTATION ARE,

(A) FINAL PRODUCTS IN SLUDGE DIGESTER.

(B) STAGES IN SLUDGE DIGESTION PROCESS.

&(C) FACTORS AFFECTING SLUDGE DIGESTION AND THEIR CONTROL.

(A) FINAL PRODUCTS IN SLUDGE DIGESTOR !

AS DAYS PASS SLUDGE BREAKS INTO 3 COMPONENTS.

STABILISED SLUDGE/ DIGESTED SLUDGE/

RIPENED SLUDGE

SLUDGE BREAKS 2.SUPERNATANT LIQUOR

3. DECOMPOSITION OF GASES

1.

BRIEF EXPLANATION OF FINAL PRODUCTS IN SLUDGE DIGESTER

1. DIGESTED SLUDGE

• HUMUS LIKE SOLID MATTER.

• TARY BLACK IN COLOR.

• REDUCED MOISTURE CONTENT.

• QUALITY IS MUCH BETTER THAN UNDIGESTED SLUDGE.

• FREE OF PATHOGENIC BACTERIA.

2 . SUPERNATANT LIQUOR

• LIQUIFIED AND FINELY DIVIDED SOLID MATTER.

• HIGH BOD (3000 ppm).

3. DECOMPOSITION OF GASES

• METHANE (65 – 75%)

• CARBON DIOXIDE (30%)

• NITROGEN

• HYDROGEN SULPHIDE.

HOW THESE COMPONENTS

CAN BE SEPARATE

FROM SLUDGE DIGESTER?

WHAT ARE THE USES OF THESE COMPONENTS ?

1.DIGESTED SLUDGE

DEWATERED

DRIED UP

FERTILIZER

2.SUPERNATANT LIQUOR

1500 – 3000 ppm OF SUSPENDED SOLIDS

RETREAT ALONG WITH RAW SEWAGE

3.DECOMPOSITION OF GAS

METHANE

FUEL

(B) STAGES IN THE

SLUDGE DIGESTION PROCESS

STAGES

1. ACID FERMENTATION/ACID PRODUCTION STAGE

2.ACID REGRESSION

3. ALKALINE FERMENTATION

STABILISED SLUDGE /DIGESTED SLUDGERIPENED SLUDGE+ SUPERNATANT LIQUOR + METHANE GAS

1 . ACID FERMENTATION / ACID PRODUCTION STAGE

FRESH SEWAGE SLUDGE

ANAEROBIC +

FACULTATIVE BACTERIA HYDROLYSIS

SOLUBLE PRODUCTS FERMENT

VOLATILE ACIDS ORGANIC ALCOHOLS OF LOW MOLECULAR WEIGHT LIKE PROPIONIC

ACID AND ACETIC ACID

ACID FORMERS / ACIDOGENS

GASES LIKE &

• HIGHLY ACIDIC. • PH 6

• HIGHLY PUTREFACTIVE ODOURS ARE EVOLVED FOR 15 DAYS.

• BOD IS INCREASED.

2 . ACID REGRESSION

• INTERMEDIATE STAGE.• VOLATILE ORGANIC ACIDS + NITROGENEOUS COMPOUNDS (ATTACKED BY BACTERIA)

ACID CARBONATES + AMMONIA COMPOUNDS +HYDROGEN SULPHIDE + CARBO DIOXIDE

FIRST STAGE

• HIGHLY OFFENSIVE ODOUR ARE EVOLVED FOR 3MONTHS.

• PH INCREASES TO ABOUT 6.8. HOW?• DECOMPOSED SLUDGE ENTRAPS THE GASES

OF DECOMPOSITION. IT BECOMES FOAMY AND RISES TO THE SURFACE TO FORM SCUM.

• BOD REMAIN HIGH.

3. ALKALINE FERMENTATION

• FINAL STAGE OF SLUDGE DIGESTION.• PROTIENS

+ ORGANIC ACIDS

(ATTACKED BY ANAEROBIC BACTERIA CALLED METHANE FORMERS / STRICT ANAEROBER)

AMMONIA + ORGANIC ACIDS + GASES

HIGH RESISTANT MATERIALS

• THE LIQUID SEPARATES OUT FROM SOLIDS TO FORM DIGESTED SLUDGE.

• THE SLUDGE IS GRANULAR AND STABLE .

• DOES NOT GIVE OFFENSIVE SMELL.

• IT HAS MUSTY EARTHY ODOUR.

• DIGESTED SLUDGE IS COLLECTED AT THE BOTTOM OF THE DIGESTION TANK AND IS CALLED RIPENED SLUDGE.

• IT IS ALKALINE IN NATURE.

• PH ≥ 7

• METHANE (60 % – 75%), (30%),

• THIS STAGE EXTENTS TO A PERIOD OF 1 MONTH.

• BOD IS REDUCED.

CONCLUSION OF STAGES IN THE SLUDGE DIGESTION PROCESS(NATURALLY)

• 4 MONTHS ARE REQUIRED FOR THE COMPLETE PROCESS OF SLUDGE DIGESTION TO TAKE PLACE UNDER NATURAL , UNCONTROLLED CONDITION AT ABOUT .

• DIGESTION DEPENDS ON MANY FACTORS LIKE TEMPERATURE .

• IF THE FACTORS AFFECTING SLUDGE DIGESTION ARE CONTROLLED , QUICKER AND EFFECTIVE DIGESTION CAN BE DONE.

(C) FACTORS AFFECTING

SLUDGE DIGESTION AND

THEIR CONTROL

THE IMPORTANT FACTORS AFFECTING SLUDGE DIGESTION ARE ,

1 . TEMPERATURE

2 . PH VALUE

3 . SEEDING WITH DIGESTED SLUDGE AND

4 . MIXING AND STIRRING OF THE RAW SLUDGE WITH DIGESTED SLUDGE.

THE MINOR FACTORS ARE,

• QUALITY OF WATER SUPPLIED.

• PRESENCE OF – COPPER, FLUORIDES, RADIO ACTIVE SUBSTANCES.

BRIEF EXPLANATION OF MAJOR FACTORS

1. TEMPERATURE

• HIGHER THE TEMPERATURE , HIGHER IS THE RATE OF DIGESTION .

• THE 2 DISTINCT TEMPERATURE ZONES ARE, - (a) ZONE OF THERMOPHILIC DIGESTION. - (b) ZONE OF MESOPHILIC DIGESTION.

(a) ZONE OF THERMOPHILIC DIGESTION

• THERMOPHILIC ORGANISMS MEAN HEAT LOVING ORGANISMS.

• -

• OPTIMUM THERMOPHILIC TEMPERATURE =

• DIGESTION PERIOD – 10 TO 15 DAYS

• IT IS NOT PREFFERED BECAUSE OF ODOUR AND OPERATIONAL DIFFICULTIES.

(b) ZONE OF MESOPHILIC DIGESTION

• OPTIMUM MESOPHILIC TEMPERATURE =

• DIGESTION PERIOD – 30 DAYS

• EXTERNAL HEATING DEVICES IS FIXED IN DIGESTION TANK TO CONTROL TEMPERATURE.

CONTROLLED SLUDGE DIGESTOR

2. PH VALUE

• VOLATILE ACIDS METHANE FORMERS METHANE GAS

• IF METHANE FORMERS WERE NOT PRESENT IN THE SLUDGE DIGESTER ,PH VALUE WILL GO BELOW 5 . IT WILL INCREASE THE ACIDITY, AND THUS SUPPRESS FURTHER BACTERIAL ACTION.

• IN INITIAL STAGE (ACID FERMENTATION/ACID PRODUCTION STAGE) PH VALUE OF 6.5 HAVE TO BE MAINTAINED.

• SO THAT IN FINAL STAGE (ALKALINE FERMENTATION STAGE) PH VALUE OF 7.2 – 7.4 WILL BE MAINTAINED.

• ACIDITY INCREASES DUE TO

- OVERDOSING OF RAW SLUDGE .

- OVERWITHDRAWAL OF DIGESTED SLUDGE.

• REMEDY

- ADD HYDRATED LIME (2.3- 4.5 ) IN RAW SLUDGE.

• FOR THE MAINTENANCE OF OPTIMUM VALUE OF PH

- WEIGHT OF RAW SLUDGE TO BE ADDED SHOULD BE 2 - 3% WEIGHT OF DIGESTED SLUDGE WHICH IS REMOVING FROM

THE SLUDGE DIGESTER.

SEEDING WITH THE SLUDGE DIGESTER

WHAT IS SEEDING ?*A SLUDGE DIGESTION TANK .

*WHEN FIRST PUT IN OPERATION –

*DIGESTED SLUDGE FROM OLD SLUDGE DIGESTER IS KEPT IN IT FOR SOME DAYS .

DIGESTED SLUDGE

• WITHOUT SEEDING , IT MAY TAKE A FEW MONTHS TO GET A TANK TO OPERATE PROPERLY.

• PROPER SEEDING CAN GIVE GOOD RESULTS QUICKLY.

MIXING AND STIRRING OF THE RAW SLUDGE WITH THE DIGESTED SLUDGE• RAW SLUDGE + DIGESTED SLUDGE

(MIX WELL)

HOMOGENEOUS MIXTURE

*HELPS IN DECOMPOSITION OF ORGANIC MATTER QUICKLY.

*MIXING IS DONE IN SLUDGE DIGESTOR USING AGITATOR / OTHER DEVICES.

*THIS REDUCES SCUM AND INCREASES THE PRODUCTION OF GAS.

*EXCESSIVE STIRRING WILL KILL USEFUL BACTERIAS.

CONCLUSION

THANK YOU…