الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
Anaerobic digestion of organic residues (biogas
technology) is one of the renewable energy technologies
to produce a flammable gas as em energy source. The
digested materials left pr-e serrc a good source of organic
manure rich in macro and micro plant nutrients.
In this investigation the evaluation of biogas
and organic manures production from cow dung and sewage
effluent was studied. The resulting organic manures were
compared with traditional orga~ic manures, i.e. farmyard
manure and poUdrette in their effect on the counts of
soil microflora, the microbial enz~~tic activities, and
the soil carbon and nitrogen content.
Two different types of biogas digesters were chosen,
the Chinese and Indian model. The digesters were fed with
200 liters of 8% and 3% total solids from cow dung and
sewage water, respectively. The digestion period was 70
days. Biogas yield was mont tcr-ed daily, while its content
of CH
4
and CO2 were estimated at weekly intervals. The
total and volatile solids, the total nitrogen and organic
carbon content were determined in initial and final stages
while ammoniacal nitrogen was determined every week. When
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the fermentation reached an elld, the residual materials
were dried and crushed to be used as organic manure.
Two types of soil were used, the alluvial clay
loam from Moshtohor village, Kalyubia Governorate and
the aandy soil from south of Jrahreer province, Behera
Governorate. A four replicat19s pot experiment was conducted
where the two biogas ~~d the two traditional organic
manures were added to the soil at the rate of 800 kg organic
matter per feddan. The soil lnoisture was adjusted at 50-
60%of w.h.c. and mentained at; this rate throughout the
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experimental time.
The microbial counts of bacteria, actinomycetes,
fungi, aerobic and anaerobic celLu Lose decomposers, coliform
group and Shigella~. and Salmonella~. were estima:
ted at the periods of 0, 15:t 30, 60, 90, 120 and 160 days.
Also the soil total nitrogen and organic carbon content
were determined at the aformentioned periods.
The microbial acti vi tiE~S represented by dehydrogenase,
phosphatase, urease and nitrogenase were measured at
the periods of 0, 1, 3, 5, 7, 15, 30, 60, 90, 120 and 160
days.
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The obtained results can be summar-i.zedas follows:-
1) The sewage sludge started biogas production
from the first day in both types of d.igesters while cow
dung started after 14 and 18 daysin Chinese and Indian
tJ~es, respectively. The daily biogas production increased
till 16 and 30 days for sewage sludge and cow dung, respectively
then decreased thereafter. The cumulative gas production
was higher in Chinese than Indian type for both
residual materials. In Chinese type cow dung produced
more gas than sewage sludge ~mile in the Indian type sewage
sludge produced more gas than cow dung.
2) The methane content of the gas produced from the
Indian was similar to that produced from the Chinese
digester when using the same organic materials. But the
gas produced from the sewage sludge digestion contained
apparently higher percentage of methane than that produced
from cow dung.
3) The losses in vol~~ile or total solids as a result
of the sewage sludge fermentation were higher than cow
dung. The losses of either residue in the two digesters
were very close to each other.
4) It was found that the total nitrogen content
of the digested materials was lower at the end of digestion
than the respective value in the initial sample.
The loss was higher in Chines(~ than Indian digesters and
in sewage sludge than cow d~~. The ammoniacal nitrogen
reached its maximum. concentration in the period 7-28 days
according to the type of digester an<i the ~ of residue,
then gradually decreased thereafter.
5) It can be concluded that the Chinese type of
digesters was more efficient in the anaerobic digestion
of organic residues, since it produced almost the same
quanti ty of organic manure as the Indian type while it
produced more amounts of bf.ogas than the Indian digester.
6) The application of organic manures to the alluvial
and sandy soils Lncr-eased the total counts of bacteria
and actinomycetes. The digested cow dung was more effective
followed by the digested sewc~e sludge > farmyard manure
> poudrette, except in the case of sandy soil, the actinamycetes
count was more in poudrette than farmyard manure.
Also it was clear that the ef”fect of manuring the sandy soil
in increasing the counts was more apparent than alluvial
soil.
7) The total count of fungi was enhanced by the
application of organic manures, digested biogas manures
was more effective than traditional organic manures in
enhancing the funGal growth. Digested sewage slUdge
gave a peak, higher than cow dung followed by poudrette
then the farmyard manure.
8) The counts of aerobic cellulose decomposers
were apparently stimulated iDy the addition of digested
cow dung followed by digest13d sewage sludge then the farmyard
manure and poudrette. In case of the sandy soil the
two digested organic manures showed nearly the same level
of activation followed by farmyard manure which is more
effective than poudrette.
9) As was expected the digested organic manures
showed higher densities of cmaerobic cellUlose decomposers
than traditional organic marlures and control due to the
anaerobic conditions in the ferment or • In alluvial soil
the digested cow dung was mor-e effective than digested
sewage sludge followed by farmyard manure and poudrette,
while in the sandy soil the order was digested sewage
sludge > digested cow dung ’> poud.rette > FYK.
, .
10) The poudr-etbe and liisested sewage sludge
showed higher increase in cOQnts of coliform group
than farmyard manure and poudrette in both alluvial
and sandy soils. This was attributed to the origin
of both poudrette and digested sewage sludge which
the human excretes. The COUIl,ts of coliform group decreased
gradually from the 60th d~ till they completely disappeared.
11) There was not any Golony of,Salmonella.!!l2.-
and Shigella .£ll2,. in the platE~s of control or soils
treated by biogas manures, while in soils treated by
tradi tional manures there we:re some colonies at the
beginning and then disappeared rapidly.
12) The dehydrogenase activity was increased in the
sandy and alluvial soil treated with organic manures than
control and this was attributed to the growth and proliferation
of soil microorganisms following the moistening
of the soil. Dehydrogenase activity slightly increased
for few days, then graduallJ’ decreased thereafter: The
digested cow dung showed thE! highest activity followed by
farmyard manure, poudrette, while the sewage sludge showed
the lowest figures.
13’) The addition of organic ::..anuresfavoured
the phosphatase activity in a manner related to the
COUll ts of different microbial .i;roups. In alluvial
soil the results showed the superiority of the sewage
sludge followed by digested cow dung > farmyard
manure> poudrette. Phosphatase enzyme in sandy soil
showed lower activity than alluvial soil. The order of
stimulation in sandy soil is as follows: digested cow
dung > farmyard manure :> digested sewage sludge >
poudrette.
14) The most efficient organic manure in enhancing
the proliferation of urea hyc~olyzing microorganisms, and
urease actiVity, as a result, was the digested cow dung
followed by sewage sludge. It was suggested that the
presence of considerable concentration of heavy metals
in sewage sludge may act in the inhibition of urease activi
ty. The least stimulation was observed in farmyard
manure followed by poudrette. This was true for both sandy
and allUvial soils.
15) The application of organic. manures to the soils
increased the efficiency of ni.trogen fixation as expressed
by the nitrogenase activity. Di5ested cow dung showed
highest figures allover the experiment followed by f’arm-
yard mEL~ure then diGested sewage sludge, while poudrette
showed the least activity. Xitrogenase activitjin
sandy soil was apparently less stimulated than alluvial.
In sandy soil the digested cow dung favoured nitrogenase
activity more than digested sewage sludge followed
by farmyard manure and poudrette.
16) The addition of the organic manures increased
the organic matter content of the soil. The increase was
almost the same in all the tested manures. A gradual decrease
in organic matter was observed till the end of the
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experimental period. A positive ~elation between the
rapid decomposition of the organic matter and microbial
activity can be demonstrated in the same period. The same
trend was observed inalluvia.l and sandy soils.
17) The initial samp’l.ee of manured sandy and alluvial
soils contained higher amountis of total nitrogen. This
total nitrogen content decreased early and then gradually
increased thereafter till the end of the experimental
period. The digested cow dung treatment showed the highest
level of total nitrogen allover the experimental period,
while thtl’ othuthree manures exhibited many close levels which
were much less than the forIuer.
18) The C:N ratio of both soils was not affected
by the incorporation of organic manures. However, the
ratio was gradually narrowed till the end of the experiment.
1.9) Manuring the testEld sod.Ls increased their
content of the ammoniacal nitrogen, but it was rapidly
assimilated by soil microorgcwism and decreased after
15 days of manuring, then a gr-adua’l, decrease for 90 days
followed by a slight build U]~. The four applied manures
showed the same level of NH4··-Nalmost a’Tlover’ the experimental
period.
1.0) The nitrate nitrogen content in alluvial soil
showed reverse trend to that of NH4-:n. The maximum stimulation
of nitrifiers was observed in the digested sewage
sludge treatment followed by digested cow dung then poudrette
and farmyard manure, respectively. The same trend IN’a 5
observed in sandy soil, but the initial samples showed
equal amounts of nitrate nitrogen in control and manured
soil.