الفهرس 
CI" ~ "CTERlZATION OF RAW WASTEOnly 14 pages are availabe for public view
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Abstract
The ,Purpose of the present investi.gation was to
~ the performance of a modified activated sludge
process to be used in the treatment of wastes deficient
in phosphorus and nitrogen~ The waste subject of the
present study represents the wash effluent from an onion
drying factory.
Available nutrients in an organic waste should
always satisfy the proportional build up of bacteria to
the optimal requirements· of a given activated sludge~
~ereforef an investigation on the partial removal. of
organic matter fro~ solution by means of a low synthesis-
;
high oxidation process has been adopted.
Contact stabilisation as one of the modifications
.of·activated sludge treatment was selected for experimentation.
In this process, the waste stream flows into a
contact basin witp. a retention period of 30 - 60 minutes;
during which the org~cs are aQsorbed on the sludge floc.
The activated s1udge is then separated from the mixed
liquor in a sedimentation tank and passed into a stabi-
lization basin to allow the adsorbed organics to be ..,
metabolized by available micro-organisms. Aeration is
persued in the stabilization basin for 2 to 8 hours depen-
dant on the strength of a given waste batch~
In order to test the engineering feasibility of
this mode of operation studies have been conducted using
a continuous-flow bench-scale system.
The so formed sludge was recycled within a volumetric
ratio of one part of sludge to one part of onion waste.
The detention time in the contact column has been basically
derived from the total volume or rate of flow in’ relation
to the available size of aerated column.
Adaptation of sludge has been performed along
the·continuous run of tb?t system.
The data obtained may be summarized as fqllows :
1 - When the retention period in the reaeration chamber
was selected at 2 hours, an average BOD removal of 65 %
was reached. However, it may be noted that during such a
period, both tho percentages of BOD and COD removals tend
to fluctuate. This, BOD removal ranges vary between 56 %
and 87 % while the permenganate value ranged from 70 to ,
2 - When the retention period in the re-aeration zone
was raised from 2 to 4 hours, the ratios increased from
65 % to 80 % for BOD removals and from 74.4 % to 85.4 %
for removal of COD.
3 - With a reaeration time of 6 hours and a contact
period of 30 minutes, COD and BOD removals were raised
to the order of 94 % and 93 % respectively.
4 - When the BOD load was changed from 5.35 lrg/m3• d
to 2.72 kg/m3• d by increasing the detention period in
the contact chamber from 30 to 60 minutes and the subsequent
decrease of the hydraulic load from 48 m3/m3• d
to 24 m3/m3• d, BOD removal up to 94.2 % was obtained.
Corresponding pennanganate value removal 95.4 %. It is
important to note that during this period of operation
the syst em oper-at-edin a relatively stable manner with
respect to effluent COD and BOD removals.
Furthermore, studies on a laboratory scale were
carried out to define the properties and characteristics
of excess sludge, that determines its filterablity. An
evaluation of -che effect of aerobic digesion and chemi-’
ca.L conditioning prior to filtration was considered.
Experiments were carried out on thickened sludge from
the stabilization zone without any further treatment.