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Composition of the “filtrate” from thermally conditioned sludges
Water Research Pergamon Press 1972. Vol. 6, pp. 521-525. Printed in Great Britain COMPOSITION
OF THE "FILTRATE" FROM CONDITIONED SLUDGES
THERMALLY
F. SAm~'RT Berliner Entw~isserungswerke, D-1 Berlin 31, Eisenzalmstrasse 32, FRG
THIS paper gives the results of an investigation on the filtrates obtained by thermally conditioning sludges from predominantly municipal plants. Analyses of such filtrates are given in TABLE 1. Conditioning was carried out at 170--210° C, with reaction times of 30-90 min. Under these conditions no significant difference in the composition of the "filtrate" could be found. However, the filter resistance of the conditioned sludges greatly depends on the temperature and the reaction time. With an increase in temperature and an increase in react.ion time, the filter resistance decreases remarkably, i.e. the sludge can be filtered far better (Fro. 1). 10~2x 3"0 60rain Digested sludge
2"0
90rain 1'0
T-..c._~. 160
170
180
190
200
J
210 °C
60min 10~2× h.O
30rnin
i Raw
r'.,".
t
sludge
3"0
Z.O
-X
".,,\\
iX ~
1.0
]\!
160
170
I
"',.",. "-. \ \
........ . .
180 FiG. 1. 521
190
200
210 *C
ERICKSON a n d KNoPP (1971) H LrRWITZ a n d DUNDAS (1960)
H i g h oxidation 70 ~, oxidation)
(ca.
ERICKSON a n d KNOPP (1971)
15-90 min)
Sludge
Activated
Raw
Raw
MANN (1969) Raw MANN (1969) Raw MANN (1969) Digested BROOKS (1968) Activated HARTMAr,~ (1968) Digested EMSCHERGENOSSENSCHAFT Activated BERLINER ENTW.~gSERLrNGSWERKE R a w ENTW)~SSERUNGSWERKE Digested
Author
L o w oxidation (5-10 % oxidation)
Thermal (180-215°C
Conditions
50 --
5 5
2'5~
?
100
9.
9
100
5
?
20-80 --100 --
OS (%)
Part
3 5"6 4"3 1 7
TS (%)
TABLE I. CoNCENTRATION OF FILTRATE (THERM. CONE).)
8300-11,600
7960
11,500
--
--
--
13,000 13,000
20,000
13,000 12,500 12,000
------
13,380 15,780 16,640 5450 --
4890-71 i 0
4435
5270
I 0,000 5000
! 5,000
6870 8730 5680 2800 80OO
CSB ( m g 1- l) K M n O , , ( m g 1-1) BSBs ( m g I- i)
Filtrate c o n s t i t u t i o n
g,
6500
13,000
650
1000
org. C
KMnO,
NH4-N
org.-N
85
12,500
CSB
PO, (total)
I0,000
Filtrate
BSBs
(mg I- 1)
Raw sludge thermically conditioned
1000
950
500
7500
3000
9000
I000
200
50
500
500
300
1000
250
Filtrate
600
200
500
4000
1650
5000
625
1000
350
500
7500
3000
9000
I000
150
900
650
13,000
5500
12,000
5000
Filtrate
575
625
575
10,250
4250
10,500
3000
Dig. Supernatant -k filtrate (I : 1)
Digestion ÷ chemically conditioned
Dig. supcrnatant Dig. Supernatant + filtrate (! : ! )
Digestion q- chemically conditioned
CONCENTRATION OF FILTRATE AND/OR DIGESTER SUPERNATANT
Dig. Supernatant
TABLE 2.
t~
1
e~
m.
0
O
524
F. SARFERT
The BODs-content of the filtrate of thermally conditioned digested sludges is 50 per cent lower than that from raw sludges. The COD-values are about the same with both types of sludges. Mann obtained higher COD-values for digested sludge (TABLE1). The high values are caused by the high COD-values in the filtrate of the unconditioned sludge; these values are high because of much industrial effluent in the wastewater. We realized, as did other workers, that by conditioning activated sludge a higher amount of organic matter will go into "solution" than when conditioning primary sludge. Where primary and secondary sludges are together conditioned, the influence upon the activated sludge is such that, in our work, a smaller part of the activated sludge will go into "solution" than when it is treated alone. With an increase in the sludge concentration of the sludge to be conditioned, the contents of organic matter in the "filtrate" also increases. We obtained, when conditioning raw sludges, e.g. the following results:
Filtrate Dry matter (%) around 3.5 around 5.0
COD (mg 1-1) 9000 12,500
BOD5 (mg 1-1) 7500 10,000
The same dependence exists when conditioning digested sludges. T~t.E 2 presents data on the filtrate from a sludge with 5 per cent dry matter. This sludge contained 50 per cent primary and 50 per cent excess sludge. The sludge was treated thermally as raw sludge, another part was digested and afterwards it was divided again; one part was chemically conditioned with aluminium-chlorhydrate. The other was thermally conditioned. The data given were obtained with sludges from the treatment plant at Berlin-Ruhleben, which treats domestic sewage. The raw sludge was conditioned for 45-60 min at 190-200°C, and the digested sludge for about 60 min at 200-210°C, respectively. The data given for the digester supernatant (Fw) and the filtrate from digested sludge (Fs ohk)are the mean of numerous results. The digester supernatant contain an average dry matter content of 1 per cent. The filtrate from digested sludge was obtained after chemical conditioning with aluminium chlorhydrate. We assumed that 50 per cent of the mixture was digester supernatant, and the other 50 per cent filtrate was from digested sludge which originated either from chemically or thermally digested sludges. The whole mixture has about the composition given in the rows 4 and 7, respectively. When conditioning raw sludge, there naturally is only the "filtrate". The quantity of strong wastes from sludge handling normally amounts to less than 1 per cent of the total wastewater quantity. Regarding the aerobic biological treatment of "filtrates", extensive investigations have been undertaken by the "Berliner Entw~isserungswerke" and results will be published soon. We can state, however, that the increase in the effluent from our treatment plant (COD, TOC were measured) was proportional to the increase in the load to our plant due to the "filtrate".
Composition of the "Filtrate" from Thermally Conditioned Sludges
525
REFERENCES
BltOOg~ R. B. (1965) Heat treatment of activated sludge. Wat. Pollut. Control 67, 592-601. EMSC~ROENO~ENSCUA~ (Personal communication). ERICKSONA. H. and I~NOPP (1971) Biological treatment of thermally conditoned sludge liquors. In: 5th International Water Pollution Research Cmlference 1970. Per m~mon Press, Oxford. I-IAI~TMAN(1968) Die Scblammbehandlung im Klgrwerk Nfirnberg I. Berichte d. ATV, H. 22 "Niirnberger Tagung", pp. 27--43. Htntwrrz E. and DUNDASW. A. (1960) Wet oxidation of sewage sludge. Wat. Pollut. Control Fed. 32, 918-929. M A n T. (1969) Versuche zur thermischen Aufbereitung von KliLrschlamm. Kommunalwirtsch. 9, 374-378.
OF THE "FILTRATE" FROM CONDITIONED SLUDGES
THERMALLY
F. SAm~'RT Berliner Entw~isserungswerke, D-1 Berlin 31, Eisenzalmstrasse 32, FRG
THIS paper gives the results of an investigation on the filtrates obtained by thermally conditioning sludges from predominantly municipal plants. Analyses of such filtrates are given in TABLE 1. Conditioning was carried out at 170--210° C, with reaction times of 30-90 min. Under these conditions no significant difference in the composition of the "filtrate" could be found. However, the filter resistance of the conditioned sludges greatly depends on the temperature and the reaction time. With an increase in temperature and an increase in react.ion time, the filter resistance decreases remarkably, i.e. the sludge can be filtered far better (Fro. 1). 10~2x 3"0 60rain Digested sludge
2"0
90rain 1'0
T-..c._~. 160
170
180
190
200
J
210 °C
60min 10~2× h.O
30rnin
i Raw
r'.,".
t
sludge
3"0
Z.O
-X
".,,\\
iX ~
1.0
]\!
160
170
I
"',.",. "-. \ \
........ . .
180 FiG. 1. 521
190
200
210 *C
ERICKSON a n d KNoPP (1971) H LrRWITZ a n d DUNDAS (1960)
H i g h oxidation 70 ~, oxidation)
(ca.
ERICKSON a n d KNOPP (1971)
15-90 min)
Sludge
Activated
Raw
Raw
MANN (1969) Raw MANN (1969) Raw MANN (1969) Digested BROOKS (1968) Activated HARTMAr,~ (1968) Digested EMSCHERGENOSSENSCHAFT Activated BERLINER ENTW.~gSERLrNGSWERKE R a w ENTW)~SSERUNGSWERKE Digested
Author
L o w oxidation (5-10 % oxidation)
Thermal (180-215°C
Conditions
50 --
5 5
2'5~
?
100
9.
9
100
5
?
20-80 --100 --
OS (%)
Part
3 5"6 4"3 1 7
TS (%)
TABLE I. CoNCENTRATION OF FILTRATE (THERM. CONE).)
8300-11,600
7960
11,500
--
--
--
13,000 13,000
20,000
13,000 12,500 12,000
------
13,380 15,780 16,640 5450 --
4890-71 i 0
4435
5270
I 0,000 5000
! 5,000
6870 8730 5680 2800 80OO
CSB ( m g 1- l) K M n O , , ( m g 1-1) BSBs ( m g I- i)
Filtrate c o n s t i t u t i o n
g,
6500
13,000
650
1000
org. C
KMnO,
NH4-N
org.-N
85
12,500
CSB
PO, (total)
I0,000
Filtrate
BSBs
(mg I- 1)
Raw sludge thermically conditioned
1000
950
500
7500
3000
9000
I000
200
50
500
500
300
1000
250
Filtrate
600
200
500
4000
1650
5000
625
1000
350
500
7500
3000
9000
I000
150
900
650
13,000
5500
12,000
5000
Filtrate
575
625
575
10,250
4250
10,500
3000
Dig. Supernatant -k filtrate (I : 1)
Digestion ÷ chemically conditioned
Dig. supcrnatant Dig. Supernatant + filtrate (! : ! )
Digestion q- chemically conditioned
CONCENTRATION OF FILTRATE AND/OR DIGESTER SUPERNATANT
Dig. Supernatant
TABLE 2.
t~
1
e~
m.
0
O
524
F. SARFERT
The BODs-content of the filtrate of thermally conditioned digested sludges is 50 per cent lower than that from raw sludges. The COD-values are about the same with both types of sludges. Mann obtained higher COD-values for digested sludge (TABLE1). The high values are caused by the high COD-values in the filtrate of the unconditioned sludge; these values are high because of much industrial effluent in the wastewater. We realized, as did other workers, that by conditioning activated sludge a higher amount of organic matter will go into "solution" than when conditioning primary sludge. Where primary and secondary sludges are together conditioned, the influence upon the activated sludge is such that, in our work, a smaller part of the activated sludge will go into "solution" than when it is treated alone. With an increase in the sludge concentration of the sludge to be conditioned, the contents of organic matter in the "filtrate" also increases. We obtained, when conditioning raw sludges, e.g. the following results:
Filtrate Dry matter (%) around 3.5 around 5.0
COD (mg 1-1) 9000 12,500
BOD5 (mg 1-1) 7500 10,000
The same dependence exists when conditioning digested sludges. T~t.E 2 presents data on the filtrate from a sludge with 5 per cent dry matter. This sludge contained 50 per cent primary and 50 per cent excess sludge. The sludge was treated thermally as raw sludge, another part was digested and afterwards it was divided again; one part was chemically conditioned with aluminium-chlorhydrate. The other was thermally conditioned. The data given were obtained with sludges from the treatment plant at Berlin-Ruhleben, which treats domestic sewage. The raw sludge was conditioned for 45-60 min at 190-200°C, and the digested sludge for about 60 min at 200-210°C, respectively. The data given for the digester supernatant (Fw) and the filtrate from digested sludge (Fs ohk)are the mean of numerous results. The digester supernatant contain an average dry matter content of 1 per cent. The filtrate from digested sludge was obtained after chemical conditioning with aluminium chlorhydrate. We assumed that 50 per cent of the mixture was digester supernatant, and the other 50 per cent filtrate was from digested sludge which originated either from chemically or thermally digested sludges. The whole mixture has about the composition given in the rows 4 and 7, respectively. When conditioning raw sludge, there naturally is only the "filtrate". The quantity of strong wastes from sludge handling normally amounts to less than 1 per cent of the total wastewater quantity. Regarding the aerobic biological treatment of "filtrates", extensive investigations have been undertaken by the "Berliner Entw~isserungswerke" and results will be published soon. We can state, however, that the increase in the effluent from our treatment plant (COD, TOC were measured) was proportional to the increase in the load to our plant due to the "filtrate".
Composition of the "Filtrate" from Thermally Conditioned Sludges
525
REFERENCES
BltOOg~ R. B. (1965) Heat treatment of activated sludge. Wat. Pollut. Control 67, 592-601. EMSC~ROENO~ENSCUA~ (Personal communication). ERICKSONA. H. and I~NOPP (1971) Biological treatment of thermally conditoned sludge liquors. In: 5th International Water Pollution Research Cmlference 1970. Per m~mon Press, Oxford. I-IAI~TMAN(1968) Die Scblammbehandlung im Klgrwerk Nfirnberg I. Berichte d. ATV, H. 22 "Niirnberger Tagung", pp. 27--43. Htntwrrz E. and DUNDASW. A. (1960) Wet oxidation of sewage sludge. Wat. Pollut. Control Fed. 32, 918-929. M A n T. (1969) Versuche zur thermischen Aufbereitung von KliLrschlamm. Kommunalwirtsch. 9, 374-378.