anaerobic sewage treatment

8/2/2019 Anaerobic Sewage Treatment

1/21

ANAEROBIC SEWAGETREATMENT


2/21

HISTORICAL PERSPECTS

1850:Louis H Mourac, France

Automatic scavengers for settled sewage sludge

1895:Donald Cameron

Built first septic tank, collected CH4 and used

it for street lighting

1904:

Travic hydrolytic tank achieving dust function

of sedimentation and digestion installed at

HAMPTON


3/21

INTRODUCTION

DECOMPOSITION OF ORGANIC ANDINORGANIC MATTER WITHOUT MOLECULAR

OXYGEN

PROCESS DONE BY ANEROBIC BACTERIA

THREE TYPES


4/21

PROCESSES INVOLVED

HYDROLYSIS

ACIDOGENESIS

METHANOGENESIS


5/21

MICROBIOLOGY OF PROCESS

HYDROLYSIS:TRANSFORMATION OFCOMPLEX COMPOUNDS TO SIMPLER

COMPOUNDS.

ACIDOGENESIS:ACID FORMATION TAKESPLACE.

METHANOGENESIS:METHANE FORMATIONTAKES PLACE.


6/21

STEPS IN ANAEROBIC DIGESTION

COMPLEX

ORGANICS

HIGHER

ORGANIC

ACIDS

ACETIC ACID

H2

CH4


7/21

Complex organic material(starch, protein fats)

Simple organic material(sugar, amino acids)

Hydrolysis

Volatile fatty acids(propionate, butyrate etc.)

Acidogenesis

Acetogenesis

H2 + CO2 Acetate

CH4 + CO2

MethanogenesisMethanogenesis


8/21

STANDARD RATE ASD

THE CONTENTS OF DIGESTER AREUSUALLY UNHEATED AND UNMIXED.

DETENTION TIME VARY FROM 30 TO

60 DAYS.


9/21

MIXING OF FIRST STAGEDIGESTION CAN BE ACHIEVED BY

FOLLOWING METHODS:

Installing a draft tube mixer (commonlyused in India)


10/21

Gas recirculation (practiced in USA)


11/21

Sludge recirculation(practiced in UK,FRG)


12/21

From maintenance point of view option3 is ideal since a pump can be easily

replaced /repaired without affectingdigester performance

From mixing consideration 1 and 2 are

comparable Option 2 needs an auxiliary storage of

gas for starting up a digester.


13/21

STANDARD RATE SLUDGE DIGESTER

To pipeline


14/21

HIGH RATE ASD

HERE THE SLUDGE IS HEATED AND

MIXED.

DETENTION TIME IS TYPICALLY 15 DAYS

OR LESS.


15/21

HIGH RATE SLUDGE DIGESTER


16/21

TWO STAGE SLUDGE DIGESTIONPROCESS

SCUM


17/21

FACTORS AFFECTING ASD

DISSOLVED OXEGEN

pH (6.6 to 7.6)

NUTRIENTS AVAILABLITY.

OPTIMUM TEMPERATURE(85 TO 100 F)


18/21

ADVANTAGES OF ASD

LOW CONCENTRATION OF BIO-MASS.

METHANE IS VERY USEFUL ENDPRODUCT.

RESULTING ORGANIC MATTER IS WELLSTABILIZED.


19/21

LIMITATIONS OF ASD

SLOW GROWTH RATE(LONG DETENTION

TIME).

HIGH TEMPERATURE.


20/21


21/21

QUESTIONS ?

anaerobic sewage treatment

Documents