Composting of gamma-radiation disinfected sewage sludge

0146-57241811090771--075020010

Radlat Phys Chem Vol 18, No 3--4, pp 771-777, 1981 Pnnted m Great Britain

Pergamon Press Ltd

C O M P O S T I N G OF G A M M A - R A D I A T I O N D I S I N F E C T E D S E W A G E S L U D G E W Kawakaml,

S.Hashlmoto,

H Watanabe,

H.Ito and M.Takehlsa

H.Watanabe,

K.Nlshlmura,

Takasakl Radlatlon Chemlstry Research Establishment, JAERI,

Takasakl,

Gunma

370-12,

Japan

The e x p a n s l o n of s e w a g e s e r v l c e s is o n e of the c u r r e n t m a l n d o m e s t i c p o l l c l e s of J a p a n

The f ~ f t h f l v e - y e a r - p l a n ( t h e M ~ n l s t r y of C o n s t r u c t i o n )

w l l l s t a r t n e x t year.

A c c o r d i n g to the plan, m o r e t h a n 7 m l l l l o n ton c a k e is

p r e s u m e d to be g e n e r a t e d ~n 1985.

M o s t p a r t of s l u d g e h a v e b e e n b u r i e d in the

ground directly or after burning.

But recently,

t h e s e m e t h o d s are u r g e d to be

r e e x a m l n e d f r o m v l e w p o l n t s of e n v l r o n m e n t a l or e n e r g y saving. On the o t h e r hand,

too m u c h d e p e n d l n g on c h e m l c a l

c u l t u r e h a v e led to h u m u s d e f i c i e n c y in sol1. i i z e r to f a r m l a n d h a v e b e e n d e s i r e d .

s l u d g e or r a p i d

fertl-

L a n d a p p l l c a t l o n of s e w a g e s l u d g e usu-

ally beneflts plant growth and crop productlon, t a r y p r o b l e m s to the n e ~ g h b o u r ,

f e r t l l l z e r S in the a g r l -

A p p l l c a t l o n of o r g a n l c

b u t it m a y c a u s e o d o r or sanl-

and p l a n t s m a y be h a r m e d d u e to b l l g h t s

In

f e r m e n t a t l o n of s l u d g e in soll

As the u r b a n l z a t l o n of r u r a l a r e a s h a s b e e n p r o g r e s s e d and the a g r i c u l ture is t r a d i t i o n a l l y ~ n t e n s l v e ~n Japan,

the d l r e c t a p p l l c a t l o n of r a w s l u d g e

m a y n o t be a c c e p t a b l e e v e n a f t e r d l s l n f e c t l o n .

A t r e a t m e n t for s t a b l l z a t l o n

of sludge,

to be e s s e n t i a l l y n e c e s s a r y

for e x a m p l e c o m p o s t l n g ,

is c o n s l d e r e d

as w e l l as d l s l n f e c t l o n for the land a p p l i c a t i o n . R C . C o o p e r and C ° G . G o l u e k e I) m e a s u r e d the c o u n t s of v i r u s e s ,

or c o l l f o r m s ,

fecal c o l l f o r m s and fecal s t r e p t o c o c c i in the c o m p o s t l n g m a s s f r o m w l n d r o w type compostlng,

and sald t h a t c o m p o s t l n g I t s e l f m i g h t not be as e f f e c t l v e a d l s l n as h l t h e r t o b e l i e v e d T . U s u l and A . S h o 3 1 2) e x a m l n e d c h a n g e s of

fectlon method

m l c r o f l o r a w l t h c o m D o s t l n g of s l u d g e u s l n g a p i l o t p l a n t o f e n c l o s e d v e s s e l type,

and r e D o r t e d t h a t c o l x f o r m s in p r o d u c t s w e r e

found to be a b o u t 105 per

g r a m of c o m p o s t In g e n e r a l , by the b a c t e r l a l

the g r o w t h of i n o c u l a t e d m l c r o o r g a n l s m s is a f f e c t e d s e r i o u s l y flora in a m l d l u m .

t h a t the g r o w t h p o t e n t i a l of Eschertch~a J r r a d l a t e d s l u d g e i n c r e a s e d w l t h dose. salmonellas grew rapidly

For e x a m p l e ,

D . N S h a h et al. 3) r e p o r t e d

col~ s t r a i n B w h i c h w a s i n o c u l a t e d in M E . M o r r l s et al. 4) f o u n d t h a t

in i r r a d i a t e d c o m p o s t ,

b u t that the g r o w t h c o u l d be

inhlblted by saturation of collforms bacteria after irradlatlon B a s e d on t h e s e r e s u l t s , h a v e two a d v a n t a g e s :

compostlng process using irradiated sludge may

the f z r s t is the c o m p o s t l n g p e r l o d m a y be s h o r t e n e d b y

seedlnq eefectlve compostlng bacteria flora,

into s l u d g e of c o n t r o l l e d b a c t e r i a l

the s e c o n d is the c o n t a m ~ n a t l o n b y p a t h o g e n s or t h e l r r e g r o w t h c a n be

p r e v e n t e d by i n o c u l a t l o n of s l u d g e w l t h i n n o c u o u s c o m p o s t l n g b a c t e r i a . We h a v e 1978,

s t u d l e d on c o m p o s t l n g of r a d l a t l o n d l s l n f e c t e d s e w a g e s l u d g e slnce

a ~ m l n g to p r e s e n t a n e w p r o c e s s of s l u d g e c o m p o s t x n g for a g r i c u l t u r a l

uses

Th~s process

sludge,

and c o m p o s t l n g step to r e m o v e o d o r and e a s l l y d e c o m p o s a b l e o r g a n i c s in

ls c o m p o s e d of two s t e p s

i r r a d ~ a t l o n s t e p to d l s l n f e c t

sludge In thls paper,

the g a m m a - l r r a d x a t ] o n e f f e c t on s l u d g e cake and c o m p o s t ~ n g

RPCVolIS, No 3/4---Y 771

772

W KAWAKA~liet al

condltlon

of I r r a d l a t e d

informatlons

Radlatlon

Dlslnfectlon

Seasonal sludge

and

sampled klnds

the o t h e r w a s Twenty The

McConkey's

sewage

a g a r was

1 shows

change

sludge

that

the

at

process

homogenlzed

was diluted

seasonal

changes

These

are

the

sludge

of s e w a g e

were

cltles.

Two

process,

and

sludge.

and

inoculated of

in s l u d g e counts

s h o w n to be

to g r o w t h

total

medla.

bacterla,

and

samples. of b a c t e r l a

and

2x10 s to 3x109

p e r g r a m of s l u d g e

of

cake,

and

by s e a s o n s .

survlval

curves

of the y - r a d l a t l o n

exponentially

cake

Sludges

in 200 mR of s t e r 1 1 1 z e d

~n t o t a l

counts

in s e w a g e

and T a k a s a k l

30 °C for e n u m e r a t l o n

37 °C for c o l l f o r m s

300 to 500 k r a d

dewatered means

2 shows

and n e a r l y

of M a e b a s h l

2x10 7 to 2x10 8 of c o l l f o r m s

as a f u n c t l o n

by

at

cake.

and

technological

examlned.

f r o m an a c t l v a t e d

dlgestlon

solutlon

so s l g n l f l c a n t l y

Figure

level

the

In s l u d g e

to o b t a l n

and c o l l f o r m s

on t h e m w e r e

plants

one w a s

cake w e r e

used

agar was used

total bacterla,

rapldly

treatment

sludge

of b a c t e r l a

effect

f r o m an a n a e r o b i c of

in o r d e r

Sludge

counts

examlned,

supernatant

Figure

sludge

in t o t a l

were

grams

D1fco-nutrlent

not

of S e w a g e

changes

f r o m the

collforms

are d l s c u s s e d

of the p r o c e s s .

the g a m m a - l r r a d l a t l o n

of g l u d g e s

water

sludge

on d e v e l o p m e n t

wlth

dose,

It is n o t e d

is close

irradlatlon

for dose

bacterla,

Survlvlng and are

cake

reported leads

and c o l l f o r m s

col~forms

reduced

t h a t an a d e q u a t e

to the v a l u e s

of d e w a t e r e d

total

to u n d e t e c t a b l e

dlslnfectlon

for

in

dlmlnlsh

dose

s l u r r y ~ '5)

to s a v l n g

for

Thls

of r a d l a t l o n

energy. I

l

I

I

I

I

I

1

I

I

I

I

2:

31o

l

J

I

J

winter (Feb) 1

0 Maebash~ A Takasakl

~-, i lO

~-2 g_-3 ~ I

O Maebash, A Takasakt I

107!78

Dec

I

'79

I

I

I

I

I

I

Apn[ June Aug

Feb

% I

I

f

Total

cake

bacterlal Table

and t h e ± r

bacterla usually

were

counts

1 shows

radlatlon shown

radlatlon

also dlmlnlshed

sensltlvlty

to be m a l n l y but

rapldly

isolated

in p h o s p h a t e

composed they

I

IIO 115 Dose (Mrad)

20

Fig. 2 Gamma-radlatlon inactlvatlon of bacterla in sewage sludge

mlcroorganlsms

sensltlve,

05

Oct

Fig. i. Seasonal changes of counts of total bacterla and collforms

0.5 Mrad.

I

-50

wlth

from

dose,

2 Mrad

buffer.

The

of p s e u d o m o n a d s .

are p r o t e c t e d

but

in s e w a g e

slowly

irradlated

after sludge

remalnlng

Most

of t h e m are

sludge

The

Compostmg of gamma-radmUondisinfected sewage sludge

present

work

is t h e r e f o r e

deslgned

to s t u d y

the m e c h a n i s m

773

of p r o t e c t l o n .

T a b l e i. M z c r o o r g a n z s m s isolated from 2 Mrad irradlated sludge c a k e and t h e l r r a d l a t l o n s e n s l t l v l t y in p h o s p h a t e b u f f e r .

GRAM HORPHLOGYCOLOROF SURVIVALFRACTIONAT REACTION COLONIES 50 krad 500 krad HICROOOOOUS SPP(GR l)

+

COCCI

PINK/RED

6 x 10"I

2 x 10"I

HICROOOCCUS SPP(GR 2)

+

"

ORANGE

2 x 10"1

4 x 10-3

PSEUDOMONAS RADIORA

-

RODS

PSEUDOMO~VAS SPP(GR l )

"

YELLOW

6 x lO "S

........

YELLOW

2 x 10-7

........

of I r r a d i a t e d

of

3.

cake(water

4.

Mrad

uslng

ated

sludge

condltzon,

Thzs content

cake,

Co-60

was mzxed

actlvated

5-7

%) w e r e

apparatus

wlth were

has

80 %). whzch the

to r e d u c e

alumlna(30-60

used

ca.

does

not

for z s o t h e r m a l

The

other

In a e r o b l c

sludge

by I0 w t . %

was

fermentatlon.

zs a l a r g e r

One

ca.

wlth

of b a c t e r l a .

several

is s h o w n a dose The

in

of 3

irrada-

agents)

to m a l n t a l n

aeroblc

of s l u d g e

to i n i t i a t e

fermentatlon.

perllte

and the w a t e r

or d r l e d

content

compost(water

of t h e m z x t u r e

was

content 40-50

water bath

pump

zs

i0 g of

one uslng

volume

Irradlated

counts

condztlon,

fermentation.

of 50 mE u s l n g

is 13 £ zn e f f e c t a v e

the t o t a l

meshes),

as a d d l t l v e s ,

even

to i n z t l a t e

a reactor

~ddltzves(bulklng added

start

seed b a c t e r l a

apparatu=

experzments,

source

and s e e d s

The

sludge

the r e a c t o r

In these

Cake

zncludlng

of e x p e r l m e n t a l

in F l g u r e

kg of s l u d g e

Sludge

irradlated

starters

Two klnds

Flgure

1 x lO "8 ........

"

we a d d e d

sludge

I x lO "7

PS~./DOMO~AS SPP(GR 2)

Compostlng

shown

WIIITE

XIL4NTIIOMONAS SPP

Compostlng

hence

PINK/RED 2 x 10"I

"

humidfl=,er

reacter Fig. 3. Experzmental apparatus for zsothermal fermentatlon.

Fig. 4. Reactor system of the larger experlmental apparatus.

774

%.

W KAWAKAMIet al

T h e pH of t h e m z x t u r e w a s m e a s u r e d

water,

and found

humzdzfzed

to b e 7-8.

Fermentatlon

zn t h e e x h a u s t gas.

condltlons

commerczal

analyzers

type

on eompostlng,

in t h e r e a c t o r ,

to k e e p the m z x t u r e

aerobzc and

CO 2 and NH 3 eoncentratzon

865 w e r e used.

t h e e f f e c t s of i r r a d z a t l o n ,

5 s h o w s r a t e s of C O

The

fermenting

lnztlal batch, k z n d s of

was placed

Experzments were

temperature

and other

a n d t h e f e r m e n t l n g a b i l i t y of v a r l o u s

seeds and composts produced.

Figure seeds.

flow rate

was observed by measurlng

Beckman

c a r r l e d o u t to e l u c l d a t e

in s l u r r y b y a d d l n g 5 t l m e s w e z g h t of

the mlxture

azr was blew at a constant

moistened.

reaction

After

seeds.

on

zn c o m p o s t l n g b y v a r l o u s

commerclal

are s h o w n to b e v e r y d l f f e r e n t

in t h e

20

Repeated use as s e e d s w a s

f o u n d to i m p r o v e as d e s c r l b e d

evolutlon

a b z l z t y of s e e d s

dependlng

of t h e p r o d u c t

2

the a b l l l t y

below. m

Flgure

6 shows

of t e m p e r a t u r e uszng

the

the effect

on compostlng

s e e d A.

~ 10

It is n o t e d o~

that the optlmum

temperature

for f e r m e n t a t i o n

is a r o u n d

°C

In o r d l n a r y

compostlng,

u

50

processes

for

it ~s e s s e n t l a l l y

necessary

to m a l n t a l n

the fer-

mentatlon

temperature

hlgher

0

0

10

20

30

I

I

I

i

I

I

40

50

60

70

80

90

Ttme(hr)

than about 65-70 certain period pathogens

in s l u d g e .

process using sludge,

°C for a

Fzg 5. Rates of CO 2 evolutzon zn compostzng by varlous cormnerclal seeds(A,B,C)

to r e d u c e

zrradlated

o n t h e o t h e r hand,

is n o t n e c e s s a r y dlslnfectlon

condltlons,

c a n be o p e r a t e d conditlon

irradiation

at

for f e r -

is e x p e c t e d

s h o r t e n the c o m p o s t l n g Figure

2o

hence

the optlmum

and

it

to c o n s l d e r

the p r o c e s s

mentatlon,

sludge(3 Mrad) i0 g, addltlve i0 g, seed 1 g, azr 50 mZ/mln, temperature 40 °C

In the

PC 15

to

tlme.

7 s h o w s e f f e c t s of and seed addltion

on compostlng.

As unlrradi-

o~

ated sludge contalns various 5 microorganisms, ferment

it s t a r t s to

lmmedlately

by

under aeroblc condltlon

]

itself and at 0

l o w e r t e m p e r a t u r e (curve I) . For hlgher

temperature

t a k e s t l m e to s t a r t tlon(curve

2).

Curves

3 and

4 s h o w t h e r a t e s of C O e v o 2

[

i

i

i

i

i

i

20

30

40

50

60

70

80

T=me(hr)

it

fermenta-

i 10

Fig

6

Effect of temperature on compostlng sludge(3 Mrad) i0 g, addltlve i0 g, seed A 1 g, air 50 m£/mln

90

100

Compostmg of gamma-radmtlond,slnfected sewage sludge

l u t l o n In c o m p o s t l n g

of u n l r r a d l a t e d

sludge ,

uslng

seeds(composts).

hlgher

775

i

,

l

i

i

I

I

30 40 TIME(hr)

50

60

T h e r a t e ~s m u c h

than that uslng

no seed.

3[

Irradl-

ated sludge does not ferment even underaerobic condltlon(curve

5).

seeds,

the fermentation

s t a r t s as s e e n in

curves

6 a n d 7.

there

As

shown by Figure

is n o r e m a r k a b l e

r a t e s of c o m p o s t l n g un~rradlated used.

By addlng

of

sludges,

d~fference

in t h e

irradlated

and

The other mlscellaneous

speclal

bacterla

for compost~ng,

wlth

and m~xlng

, !

thls process for obta~nlng

a small quantlty

a l a r g e a m o u n t of s l u d g e .

mentlng

can be used

experlments, tlme were sludge,

serlously

In o r d l n a r y

processes,

chaff,

increase.

Further,

densltles

c a r r l e d o u t at 50 °C.

affected by fermentatlon

aeroblc condltion

are very

as t h e s e c a n b e o b t a l n e d

small,

8 s h o w s t h e r a t e s of C O

carbon

the amount

are deslrable

so c o u n t s o f b a c t e r i a

5 to 7, a n d t h e r a t e s

in s l u d g e to c a r b o n d i o x i d e

a r e v e r y hlgh.

is c a l c u l a t e d

added are

Repeated

The converslon to be

of

20 to 30 % f r o m

carbon dloxlde.

s h o w n in F i g u r e

5.

f o u n d to b e

seriously

or physical

s l m l l a r as t h e p a t t e r n

~n i s o t h e r m a l

compost-

T h e r a t e of C O 2 e v o l u t l o n

to t h a t of t h e s m a l l e x p e r i m e n t s .

temperature

So compostlng

f r o m p o l n t of s l u d g e t r e a t -

~s s h o w n to i m p r o v e i t s s e e d a c t i v i t y .

the large reactor

evolutlon was

to b e a d d e d f o r

o n l y in s e a s o n a n d t h e b u l k

9 s h o w s t h e r a t e s of C O 2 a n d N H 3 e v o l u t l o n

nearly equal

t h a n 20 h o u r s of

certaln seed actlvlty.

b u t t h e s e m a k e w e l g h t of p r o d u c t

as s l u d g e cake,

In F i g u r e s

of e v o l u t e d

Figure

aeration,

7 3 B 2

e v o l u t l o n In c o m p o s t l n g u s i n g d r i e d 2 to k e e p t h e s l u d g e a e r o b l c . The drled compost

added by the same amount

larger than cases

very

such addltlves

as s e e d s a n d a d d i t i v e s

u s e of t h e p r o d u c t

and more

large area for storage are needed.

ment.

Figure

tlme,

s t r a w or b a r k a r e p r o p o s e d

uslng

• ng u s l n g

70

T h e r a t e of C O 2 e v o l u -

for obtaznlng

in t h e r e a c t o r ,

method wlthout

organlc

sludge I0 g, addltlve i0 g, alr 50 mZ/mln, temperature 50 °C (curve 1 40 °C), curves 1 2 3 4 5 6 dose (Mrad) 0 0 0 0 3 3 seed(compost A,B) A B - A (g) 0 0 2 2 0 2

for varlous

f o u n d to b e n e c e s s a r y

malntalnlng

was

|

a d d e d as s e e d s to t h e i r r a d l a t e d

fermentation was

composts

!

Fag 7. Effects of irradlatlon and seed (compost A or B) addltlon on compostzng

of s e e d s

In t h e s e

and fermentatlon were

tlon was

i

20

those

also exam-

fermented

,'~ 10

O0

the compost pro-

as s e e d s .

sludges

suffers

The fer-

a b 1 1 1 t y of c o m p o s t w a s

I n e d to c l a r l f y w h e t h e r duced

",.

seeds are always re-

serlous dlsadvantages seeds

on compost-

seeds.

If n e w s p e c i a l qulred

~-2C

so l o n g as s e e d s a r e

in s l u d g e h a v e no b a d i n f l u e n c e ing u s l n g

30

7,

In t h e s e e x p e r i m e n t s ,

affected by physlcal

s t a t e of s l u d g e ,

of C O 2 e v o l u t l o n u n d e r

condltlon

is

NH 3

s u c h as

a n d a l s o f o u n d to b e c o m e good condltlons,

differently

hltherto reported. Experlments was

of a d l a b a t l c

s m a l l e r t h a n in i s o t h e r m a l

fermentatlon were fermentation

that both CO 2 and NH 3 evolutlon,

measures

a l s o c a r r l e d out,

at 50

°C.

of degradation

but the rate

Those results mean of e a s i l y d e c o m p o s -

W KAWAKAMI et al

776

able organics

and deodorlzatlon

the o p e r a t l o n

condltion

The perlod

compostlng

of i r r a d l a t e d

and lower temperature

examine

respectlvely,

is k e p t g o o d

the q u a l i t y

sludge

,3o

tst

~ ~

as m e n t i o n e d

for a g r l c u l t u r a l

repeat

2~ ..... 3rd

after about

3 days,

when

compostlng.

c a n be p e r f o r m e d

in t h l s p r o c e s s

of product

cease

in i s o t h e r m a l

in r a t h e r above,

short

p o t t e s t s to

u s e s are p l a n n e d .

t

:

|

,

O4

i

,,

-----

,

I

i

i

03

02z

l8 2o

e,o /

0

0

I

I

i

I

I

i

10

20

30

40

50

60

70

"'"

o,

30 40 50 60 70 TIME(hr) F i g . 9. Rates of CO2 and NH3 e v o l u t i o n i n 10

Fig. 8. Effect of repeated use of drled compost as seed and addlt~ve on compostlng.

20

compost~ng uslng the larger reactor sludge(3 Mrad) 4 kg, addltlve (perl~te) 1 kg, seed(compost) 400 g, alr 4 5 Z/mln, temperature 50 °C

sludge(3 Mrad) i0 g, compost i0 g, alr 50 m£/mln, temperature 50 °C

Conclusions

Sewage is m a i n l y plant

sludge disposal

composed

growth

sludge compatible

is m o s t thls

environmental,

promlslng

study,

condition

of

irradlated

application

to a g r i c u l t u r a l

and sanitary problems.

In o d e r to

a n d to u s e it as a s a f e s o l l c o n d i t i o n e r ,

it b y a e r o b i c c o m p o s t l n g

the g a m m a - r a d l a t l o n

Sludge

of sludge usually benefits

B u t the d l r e c t

agricultural

to p l a n t s

to c o n v e r t

in u r g e n t n e e d o f r e s o l u t i o n .

and appllcatlon

and crop production.

land may cause make

is a p r o b l e m

of organics,

dlslnfectlon

sludge were

of

examined.

into

sludge cake The

it

living humus.

In

and c o m p o s t l n g

following conclusions

were

obtained (I) A n a d e q u a t e d l s l n f e c t l o n value

is c l o s e

leads

to s a v l n g o f t o t a l

(2) W h e n

to t h a t

seeds are

dlfference

is

radlatlon

used

300 to 500 k r a d

for s l u d g e cake,

The irradlatlon

of dewatered

to i n i t i a t e

fermentation,

of unlrradlated

sludge does not ferment by itself,

Compost

produced

c a n a c t as

seed~.

and bulking

(4) T h e o p t i m u m

compostlng evolution

is a b o u t

condltlon

50

°C.

in the p r o c e s s

can be carried out in the i s o t h e r m a l

(5) N H 3 e v o l u t l o n

cake

is no r e m a r k a b l e

and lrradlated

sludges.

as a s t a r t e r

are

Repeated use of the product The drled

compost can be

agents.

temperature

sider dlslnfection

there

and s e e d s

seeds has no bad influence on the seed actlvlty u s e d as s e e d s

and thls

sludge

energy.

in t h e r a t e s o f c o m p o s t l n g

(3) I r r a d i a t e d needed

dose

for s l u r r y .

at t h e o p t i m u m

fermentation

is c o n s l d e r e d

As

it is n o t n e c e s s a r y

uslng irradiated temperature.

Is h i g h e r

to o c c u r at a l m o s t

than the

sludge, The

to c o n the

rate of CO 2

in t h e a d l a b a t l c . s a m e t l m e as C O 2, a n d

as

Compostmg of gamma-radiation disinfected sewage sludge

777

both CO 2 and NH 3 evolutlon cease after about 3 days at the o p t l m u m condtlons. References (i) R.C.Cooper and C.G.Golueke,

Compost S c l e n c e / L a n d Ut111zatlon,

20(2),

29

(1978). (2) T.Usul and A,Sho31 , presented at the 17th annual m e e t l n g of the Japan Sewage Works Assoclatlon, (3) D.N.Shah, Foundatlon,

Tokyo(1980).

A.J.Slnsky and J.G.Trump.

a report to the U.S.Natzonal

Sclence

NSF Grant E N V 77-10199(1979).

(4) M.E.Morrls,

J.S.Slvlnskl,

J.R.Brandon,

K . S . N e u h a u s e r and R.L.Ward,

the

Proceedlngs of the 3rd Internatlonal C o n f e r e n c e of ESNA W o r k l n g Group on "Waste Irradlatlon",

Brno(1978).

(5) A Suess and T.Lessel,

Radlat. Phys. Chem., 2, 357(1977).