FIELD OF THE INVENTION
[0001] The present disclosure relates to wastewater treatment. More particularly
the present invention relates to, systems and methods of treating wastewater,
utilizing anaerobic bacteria for sludge digestion.
BACKGROUND OF THE INVENTION
[0002] In India alcohol is produced mostly by the fermentation of molasses using
distiller’s yeast Saccharomyces cerevisiae. The yeast converts the sugars
present in the molasses into ethanol. In the distillery a pure strain of yeast
culture from a slant is inoculated into molasses medium and propagated by
serial transfer technique using generally 10 to 15 percent inoculum.. After
getting sufficient attenuation, the culture is transferred from one vessel to
another and is thus finally taken to prefermenters where very little aeration is
used. The contents of prefermenters are then transferred to main fermenters.
Molasses diluted to about 200 brix is fed to the main fermenters. After
fermentation which takes 30 hours or more, the fermented wash is pumped to
the overhead tank in the distillation house. The yeast sludge that settles at the
bottom of the fermenter, has a high content of inorganic matter (i.e. ash) to be
of any practical use and is discarded as a waste.
[0003] The fermented wash is fed to a set of distillation columns. The wort is
introduced in the Analyser column at the top end and the steam is introduced at
the base of the Analyser column. The wash freed from alcohol is termed as
spentwash, the volume being 15 to 20 times the volume of alcohol. The bulk of
the alcoholic vapours heaving the top of the Analyser column is admitted to the
bottom of Rectifier column. Vapours from the head of rectifier column are
partially condensed and cooled to obtain rectified spirit.
[0004] After the complete recovery of alcohol the wastes consisting of spentwash
and the washings of the fermenters are thrown out from the distillery as a liquid
waste. This is called by different names such as slops, dunder, effluent, stillage
and vinasse. It varies widely in composition depending mainly on the type of

molasses used and partially on the type of yeast employed for fermentation.
Large amounts of sludge that are washed out from the bottom of the fermenter
is often added to this effluent.
[0005] The disposal of the spent wash is a serious problem faced by the
distilleries. Because of low pH of the effluent it is preferable that the method
used for treating the spentwash should be able to increase the pH also. Many
physical, chemical and biological methods have been suggested by various
workers for treating it but none of these has been found to be economical and
suitable for Indian distilleries.
[0006] In the present study, with the help of new isolated strains, detailed
investigations have been carried out to find out optimum conditions for best
reduction in pollution and other parameters with a view to improve the process
further.
[0007] In the present invention relates to overcome the obstacles of the prior art
and emphasizes on the investigations to find out optimum conditions for best
reduction in pollution and other parameters with a view to improve the process
further utilizing new isloted strains of anaerobic microorganisms.
[0008] The information disclosed in this background of the disclosure section is
only for enhancement of understanding of the general background of the
invention and should not be taken as an acknowledgement or any form of
suggestion that this information forms the prior art already known to a person
skilled in the art.
OBJECTS OF THE INVENTION
[0009] The principal object of the present invention is to overcome the
disadvantages of the prior art and provide a systems for treating wastewater,
utilizing anaerobic bacteria for sludge digestion.
[0010] Another object of the present invention relates to the use of ammonifying
bacteria for treating the distillery effluent.
[0011] Still another object of the present invention is to provide a sytem for
treating the distillery effluent that yields about 75 to 80 percent reduction in
COD.
[0012] Yet another object of the present invention is to isolate anaerobic bacterial
strains from sewage waters.
[0013] Still another object of the present invention is to provide a continuous
multistage system for distillery effluent.
[0014] These and other objects and advantages of the present subject matter will
be apparent to a person skilled in the art after consideration of the following
detailed description taken into consideration with accompanying drawings in
which preferred embodiments of the present subject matter are illustrated.
SUMMARY OF THE INVENTION
[0015] In an important embodiment, the present invention relates to the sytem for
treating wastewater, utilizing anaerobic bacteria for sludge digestion.
[0016] In another embodiment the present invention relates to a system for
treating wastewater from distillery effluent for biochemical oxygen demand
(BOD) comprising: a feeding duct for supplying the spentwash; at least
onefermentation vessel having bacteria for the uptake and degradation of
contaminants in the effluent, and; at least one collecting vessel for the
reception of the residual water from the treatment vessel.
[0017] In a preferred embodiment the distillery spentwash is the unwanted
residual liquid waste generated during alcohol production.
[0018] In another embodiment is to provide a method for treating
wastewater from distillery effluent for biochemical oxygen demand (BOD)
comprising: flowing spentwash through a first tank; optimizing
CO2 content of the spentwash by flowing into a second anaerobic reactor; and
allowing the optimized CO2 effluent from the anaerobic reactor into a
collecting tank.

[0019] In another embodiment is to provide a continuous stirred tank reactor
system for treating distillery effluent.
[0020] In yet another embodiment is to provide the anaerobic bacterial strain II
(PLCMA) isolated from sewage waters.
[0021] The foregoing summary is illustrative only and is not intended to be in any
way limiting. In addition to the illustrative aspects, embodiments, and features
described above, further aspects, embodiments, and features will become
apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. Some embodiments of system or methods in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0023] Fig. 1 illustrates a continuous stirred tank reactor, in accordance with an embodiment of the present invention;
[0024] Fig. 2 illustrates the Growth on spentwash media with initial COD loads varying from 5000 to 20000 mg/L, in accordance with an embodiment of the present invention;
[0025] Fig. 3 illustrates the Growth on spentwash media with initial COD loads varying from 25000 to 40000 mg/L, in accordance with an embodiment of the present invention;
[0026] Fig. 4 illustrates the illustrating the studies on a continuously stirred anaerobic reactor, in accordance with an embodiment of the present invention;
[0027] The figure depicts embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.
[0029] The terms “comprises”, “comprising”, or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a device, system, assembly that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such system, or assembly, or device. In other words, one or more elements in a system or device proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or device.
[0030] The present subject matter relates to wastewater treatment. More particularly the present invention relates to, systems and methods of treating wastewater utilizing anaerobic bacteria for sludge digestion.
[0031] Reference may be made to Figure 1 illustrating a continuous stirred tank reactor, in accordance with an embodiment of the present invention;
[0032] Reference may be made to Figure 2 illustrating Growth on spentwash media with initial COD loads varying from 5000 to 20000 mg/L, in accordance with an embodiment of the present invention; ;
[0033] Reference may be made to Figure 3 illustrating Growth on spentwash media with initial COD loads varying from 25000 to 40000 mg/L, in accordance with an embodiment of the present invention; ;
[0034] Reference may be made to Figure 4 illustrating studies on a continuously stirred anaerobic reactor, in accordance with an embodiment of the present invention;
[0035] In accordance with an embodiment of the present invention relates to the , systems and methods of treating wastewater utilizing anaerobic bacteria for sludge digestion
[0036] Disposal of distillery effluent is a serious problem faced by the distilleries. Because of high organic load and low pH its treatment is necessary prior to disposal on land or in river etc. Many physical, chemical and microbiological methods have been suggested for its treatment but they suffer from one or the other drawback. A process was developed at National Sugar Institute Kanpur based on the use of ammonifying bacteria, giving 80 percent reduction in COD and BOD values in 3 to 4 days.
[0037] Example 1: EFFECT OF YEAST SLUDGE AS A REPLACEMENT FOR UREA AND PHOSPHATE IN SPENTWASH MEDIUM : It was evident in the earlier experiments that urea and phosphate are needed as nutrients in spentwash medium for good growth and COD reduction. On a plant scale, due to huge volumes of the effluent, it will not be economical to add these nutrients in the required quantities. Therefore, there was a need for some cheap substitute which can be added to spentwash medium since yeast sludge produced in the distillery as a residue after molasses fermentation, is practically of no use and contains sufficient amounts of nitrogen and phosphate, attempts were made to replace the urea and phosphate with that of yeast sludge.
[0038] Yeast sludge was obtained from a distillery, autoclaved and kept in the cold. The analysis of yeast sludge showed that it had the following gross composition i.e. wet weight 9.6 percent, dry weight 4.18 percent, ash content 0.125 percent, nitrogen 0.125 percent, phosphate as PO4 0.037 percent and COD of 60,000 mg/l. 0.1 percent yeast sludge (V/V) was added into the spentwash medium in place of urea and phosphate. This contributed an additional COD load of 60 mg/l only. The cultures were transferred a few times before being analysed for reduction in COD in tank reactor (Fig 1). Typical data are presented in Table 1.
[0039] Strain I (LA 20), III (HA 600) and V (HB 100) gave a reduction of about 69 to 72 percent in 6 days while strain II (PLCMA), IV (PLCMB), and VI (PLC 600) gave a similar reduction in 2 days only. The final reduction obtained with strains II (PLCMA), IV (PLCMB) and VI (PLC 600) was about 84 to 88 percent in 4 days and 90 percent in 6 days. The data indicate that with yeast sludge the reduction in COD loads is much more than that obtained with urea and phosphate as nutrients (Table 2).It may possible be due to the fact that yeast sludge is a more natural substrate for bacteria as compared to added urea and phosphate. Further yeast sludge contains many growth promoting substance including vitamins which may be responsible for increased growth and good reduction in pollution loads. The data suggest that in place of urea and phosphate yeast sludge can be used as nutrients for getting a good reduction in pollution loads.
[0040] Table 1: Performance of isolated bacterial strains I to VI on spentwash medium containing yeast sludge in place of urea and phosphate.
S. No. Strain COD mg/l
Initial 0 hrs 48 hrs 96 hrs 144 hrs
1 I (LA20) 14900 6400 (57.05) 4600 (69.12) 4100 (72.40)
2 II (PLCMA) 15700 4400 (71.90) 2200 (85.90) 1700 (89.17)
3 III (HA 600) 27000 13000 (51.85) 9300 (65.50) 8200 (69.60)
4 IV (PLCMB) 17000 3800 (77.60) 2600 (84.70) 1800 (89.40)
5 V (HB 100) 25600 14500 (43.30) 7960 (68.90) 7500 (70.70)
6 VI (PLC 600) 14900 3200 (78.50) 1770 (88.50) 1430 (90.40)
Values in brackets denote percent reduction in COD
Table 2: Performance of isolated bacterial strains I to VI on spentwash medium
S. No. Strain COD mg/l
Initial 0 hrs 48 hrs 96 hrs 144 hrs
1 I (LA20) 15200 8270
(45.6) 7000
(53.9) 6300
(58.5)
2 II (PLCMA) 15400 5000
(67.5) 5800
(81.8) 2140
(86.1)
3 III (HA 600) 26500 15000
(56.6) 10600
(60.0) 9300
(64.7)
4 IV (PLCMB) 16300 4970
(69.5) 2950
(81.9) 2000
(87.7)
5 V (HB 100) 26200 16000
(61.1) 9000
(62.5) 9400
(64.1)
6 VI (PLC 600) 15700 4700
(70.1) 2180
(86.1) 1900
(87.0)

[0041] EFFECT OF INITIAL COD LOADS: The growth of bacterial strains on spentwash depends highly on the initial substrate concentration i.e. initial COD load. Bacteria can not grow on spentwash as such either because of a very high content of certain toxic compounds present therein or due to high osmocity. Diluted spentwash medium having different initial Cod loads support different amounts of growth as well as reduction in Cod values. All the six strain were grown on spentwash medium having initial COD ranging from 5000 to 40000 mg/l. growth in terms of turbidity as well as percent reduction in COD were determined. Initial turbidity in all cases was kept at 100 Klett units or more.
[0042] Growth at an initial COD of 5000 mg/l exhibited typical pattern of microbiological growth which was nearly over in 40 to 72 hours in most of the cases. Growth at 10000 mg/l COD, also gave the same pattern in strains III (HA 600), V (HB 100) and VI (PLC 600) but diauxic growth was seen in strains I (LA 20), II (PLCMA) and IV (PLCMB). Higher initial COD loads upto 20000 mg/l also gave a diauxic growth in all the strains and second phase of growth started from 60 to 72 hours (Fig. 2).
[0043] Strains II (PLCMA) and III (HA 600) gave diauxic patter upto an initial COD of 25000 mg/l. further higher values yielded a typical bacterial growth pattern with a single growth phase with all the strains. The final turbidity values tended to increase generally with an increase in initial COD values though the difference observed were not very large. In some cases turbidity exceeded 800 Klett units (Fig. 3).
[0044] The absence of diauxic growth at an initial COD load of 5000 and 10000 mg/l may be due to the low concentrations of the substrates responsible for the second phase of growth. Such low concentration may not be sufficient to induce the necessary enzymes. Disappearance of diauxic growth at initial Cod values higher than 20000 mg/l must be due to the nonutilization of the secondary substrates since easily biodegradable substrates themselves.
[0045] Example 2: CONTINUOUS FERMENTATION FOR WASTE TREATMENT: Most of the studies with isolated strains were done in batch experiments. One set of experiments utilized the continuously stirred tank reactor and the other one was designed as a packed bed upflow anaerobic reactor. Some of the experiments were performed by using three strains of isolated cultures.
[0046] CONTINUOUSLY STIRRED TANK REACTOR: A sample apparatus as described in Materials and Methods was set up. For starting the experiment the supernatant obtained by the centrifugation of 96 hours old culture on spentwash medium were taken in the fermenter and sterilized. 48 hours old cells obtained from growth on spentwash medium were added to this. The process of continuous fermentation was initiated by starting the feed from the reservoir and adjusting the flow rate to the required value. Initial feed chosen was 10 ml/hr corresponding to a retention time of approximately 100 hours. A series of experiments were performed by varying flow rate, initial Cod load and initial cell concentration. Recycling was also attempted. The lowest flow rates used correspond to Cod loading of 3.36, 3.52 and 5.36 kg/day/m3 of reactor volume for strains PLCMA, PLC 600 and HA 600, respectively.
[0047] EFFECT OF DILUTION RATE: The strain used for this study were PLCMA and PLC 600 acclimatized to low COD loads and strain HA 600 acclimatized to high initial COD load. Before starting the experiment, the contents of the reservoir were analyzed for OA, CODm volatile acids and pH. The experiment was run for 7 days at a constant flow rate of 10 ml/hr corresponding to a retention time of 105 to 110 days. COD, OA, volatile acids, pH and turbidity were determined after 3 or 7 days at a constant flow rate of 10 ml/hr corresponding to a retention time of 105 to 110 days. COD, OA, volatile acids, pH and turbidity were determined after 3 or 7 days. Strains PLCMA and PLC 600 gave similar results. pH rose from the initial value of 7.0 to 8.9 strain PLCMA and to 8.6 with Strain PLC 600. turbidity was in the range of 623 to 676 Klett units. OA was reduced by 85 to 88 percent and COD by 88 to 90 percent. Volatile acids increased by 2100 to2500 mg/l (Table 3, Fig. 4). All intervals of about 3 days, the flow rate was increased in gradual steps. Analysis was carried out at 3 days after each change in flow rate. Whenever any abrupt changes were observed in the parameters, data were collected upto 6 days at constant flow rate to ascertain that the performance had stabilized at that flow rate. As the flow rate and hence the dilution rate with increased with a consequent reduction in retention time, cell concentration and volatile acid concentration decreased and OA and COD increased. OA and COD represent the substrates or raw materials for the fermentation and volatile acids, biomass and the change in pH are the products of fermentation. Thus the data are in agreement with theoretical expectations for a continuously stirred tank reactor (170). Data upto a flowrate of 50 ml/hr are plotted in Fig. 4. Therefore, more than 4500 mg/l of volatile acids were formed at the lowest flowrate studied. Reduction in OA and COD was of the order of 85 to 66 percent respectively. Biomass production had a single peak at dilution rates of about 0.012 and 0.025 in strains PLC 600 and HA 600 respectively. Strain PLCMA exhibited two peaks for biomass production at dilution rates of 0.012 to 0.025.

[0048] Table 3: Performance of Strain II (PLCMA) on a continuously stirred tank reactor
Days Flow rate ml/hr Detention period hrs. Turbidity Klett Units OA mg/l COD mg/l Volatile acids mg/l pH
Values in the feed - - - 6142 15400 276.7 7.0
7 10.0 110 623 693 1746 2384.6 8.9
10 11.6 95 586 713 1746 2332.0 8.9
13 13.2 83 530 1115 2400 2276.0 8.6
19 14.4 76 410 1800 3450 1832.0 8.5
22 16.8 65 370 2080 4215 1663.0 8.4
25 20.0 55 290 3172 7015 1113.0 8.3
31 25.6 43 225 4080 9810 795.5 8.0
34 34.3 32 200 5170 11385 512.2 8.0
37 50.0 22 93 5957 14112 310.5 7.2
40 100.0 11 10 6113 15172 292.6 7.2
43 200.0 5.5 5 6140 15300 280.5 7.0

[0049] In full scale treatment plants designed earlier the spentwash was diluted initially by water to a COD load of 2000 mg/l and submitted to bacterial action. With a view to reduce the amount of dilution water, continuous fermentation experiments were carried out with the strain PLCMA at different initial COD loads by altering the flow rates correspondingly to maintain the loading on the fermenter constant. By this means it was possible to increase the COD in the feed upto about 30000 mg/l with a detention period of about 6 days and 90 percent reduction in COD was obtained. At about 60000 mg/l load in the feed, detention period had to be raised to 12 days with 83 percent reduction in COD. COD loads above this did not yield satisfactory results (Table 4). The decrease in Growth and reduction in OA and COD values beyond 60000 mg/l was probably due to the very high osmocity of the medium at this stage and the presence of high content of certain toxic compounds in the spent wash to which strains can not acclimatize.
[0050] Table 4: Effect of decreased flowrate and increased COD load
Days OA mg/l COD mg/l VA mg/l Turbidity Klett units pH
Values in the feed 5242 13746 217.5 Nil 7.1
3 612 2900 2568.3 634 8.9
6 590 2480 2630.2 639 9.0
9 590 2480 2630.0 643 9.0
Initial COD load increased to 31450 mg/l flow rate reduced to 7.5 ml/hr
9 9846 31450 456.3 Nil 7.0
12 1842 6272 5376.1 665 9.3
18 1373 5070 5453.0 683 9.5
23 763 3246 7290 710 9.5
27 750 3200 7310 715 9.5
Initial COD load increased to 57360 mg/l and flowrate reduced to 3.5 ml/hr
27 18547 57360 - 1376.5 7.0
30 11470 19350 590 7042.0 7.8
33 7354 13550 540 8953 7.9
37 5140 10253 510 9457 7.9
41 4283 9863 520 9846 7.9
45 4270 9784 530 10113 8.0
50 4200 9750 530 10146 8.0
55 4200 9750 530 10153 8.0

[0051] EFFECT OF STIRRING ON THE PERFORMANCE IN A CONTINUOUS SYSTEM: Strain II (PLCMA), was run on continuous fermenter as described earlier but without stirring. A close look at the data revealed that stirring did not improve the efficiency probably due to the fact that culture has no tendency to settle. Further only mild stirring was done to ensure proper mixing and no oxygen tension was available though slight variation in the growth was seen the total effect was very little, therefore, it can be concluded that stirring had no stimulating or deleterious effect on the performance of bacterial strain in a continuous system.
[0052] EFFECT OF HIGH INITIAL CELL CONCENTRATION: Within three days of the starting of the continuous fermenter at a flow rate of 10 ml/hr corresponding to a retention time of 110 hrs, cell concentration came down sharply to 876 Klett units from an initial value of 2700 Klett units with a reduction in OA and COD of about 91 to 93 percent, pH increased from 7.0 to 8.9. This was the best reduction obtainable in case of strain II under any condition. This much reduction was expected since the turbidity obtained after 3 days was maximum so far.
[0053] EFFECT OF RECYCLING OF TREATED EFFLUENT: Continuous fermentation was run for about 10 days with a flow rate of 10 ml/hr and feed COD of about 15000 mg/l as in earlier cases. On increasing the COD in feed to about 25000 mg/l and reducing the flow rate to 5 ml/hr, OA and COD were reduced by about 93 and 87 percent respectively and volatile acid content was 6713 mg/l (Table 5). At this point the treated effluent was at the rate of 2.5 ml/hr, maintaining the feed rate from the reservoir at 5 ml/hr. the performance of the system deteriorated over a period of time. After about three weeks, volatile acid content has fallen to about 3000 mg/l and the reduction obtained in OA and COD was only about 71 and 60 percent respectively. Thus recycling was proved to be harmful.
[0054] Table 5: Effect of recycling on the performance of Strain VI (PLC 600) on a continuously stirred tank reactor
Days Flow rate ml/hr Turbidity Klett units OA mg/l COD mg/l Volatile acids mg/l pH
Values in the feed - - 5470 15700 265 7.1
7 10.0 630 670 1600 2140 8.5
10 10.0 630 665 1600 2135 8.5
Increased the COD load to about 25000 mg/l with a flow rate of 5 ml/hr
10 (value in the feed) - - 11450 24150 356 7.0
17 5.0 665 1080 4370 5370 8.9
20 5.0 670 1050 4350 5375 8.9
23 5.0 680 754 3146 6713 8.9
Recycled the effluent at the rate of 2.5 ml/hr along with reservoir feed of 5 ml/hr
27 5.0+2.5 570 1760 4600 5970 9.0
34 5.0+2.5 446 2400 6300 5610 8.9

[0055] PACKED BED ANAEROBIC UPFLOW REACTOR: This study was conducted with strain IV (PLCMB). A simple apparatus as described in Materials and Methods was set up. The total volume of the reactor vessel was 2500 ml and void volume was 1400 ml. a 96 hours old culture of strain IV on spentwash medium was centrifuged and the supernatant was sterilized and filled into the upflow reactor vessel. Fresh spentwash medium was taken into the reservoir and sterilized. 1400 ml of a 48 hours old culture were centrifuged and the cells suspended in a small volume of the above supernatant and added to the upflow reactor. The reactor was activated by starting the flow from the reservoir at a rate of 10.3 ml/hr. the reactor performance stabilized within 3 days only. The flowrate was increased gradually in steps allowing sufficient time after each increase to allow the conditions to stabilize. Initially about three weeks were provided for stabilization, but later, periods varying from one to two weeks were found sufficient.
[0056] Though the performance of the packed bed upflow feactor is superior to a continuous fermentation system based on free suspended cells, the relative merits of the two system for practical treatment plant can be ascertained only after carrying out pilot .
[0057] There was a further decrease in the number of acids present at 72 hours and strain I (LA 20) and III (HA 600) contained formic, acetic and isovaleric acids while strain V (HB100) fave formic, acetic and butyric acid. Strains II (PLCMA), IV (PLCMB) and VI (PLC 600) gave only formic and acetic acid. During 96 hours Strains I (LA 20), III (HA 600) and V (HB 100) gave formic, acetic and butyric acids while strain II (PLCMA) gave only formic and acetic acids. Strain IV (PLCMB) and VI (PLC 600) gave only acetic acid. The data indicated that initially a number of volatile acids are formed as a result of utilization of different types of compounds present in spentwash. However, these acids are broken down further to give short chain acids when the cultures grow old, thereby reducing the number of organic acids present. Probably decanoic, caproic, isovaleric, propionic and to some extent butyric acid are metabolized to give smaller acids. Some of the acids present in earlier stages may possibly have been formed from acetic acid. These decrease later on as a result of utilization for energy when the concentration of other metabolites decreases. The utilization has to be via acetic acid. Therefore, acetic acid was present throughout. As discussed, earlier, during certain periods though the content of volatile acids remained constant, reduction in COD continued possibly due to the fact that higher acids break into smaller fragments of low COD values. However, the presence of formic acid throughout the culture growth indicates that formic acid is not generally metabolized by bacteria. The accumulation of acetic acid till last shows that after a certain limit acetic acid cannot be utilized either for energy production or for biosynthetic purposes may be due to limiting factors involved in acetic acid utilization.
[0058] To summarize, it can be concluded from the present study on distillery effluent treatment that with the help of isolated bacterial strains the spentwash can be treated so as to bring down the pollution load to a sufficiently low level. The cultures acclimatized to high initial COD load and those acclimatized at low COD loads can be made to work in a multistage treatment process by which we can get a very low final BOD in the range of 500 to 700 mg/l starting from an initial BOD of 20000 to 22000 mg/l. however as discussed earlier with sufficiently high COD loads in the range of 60000 mg/l can be fed to this system by reducing flow rate with a reduction of about 85 percent in COD values. The need for dilution water can sufficiently be reduced if the inhibitory substances present in treated effluent can be removed so that recycling can be done. In some of the strains biphasic pattern in growth and COD reduction is found and there is a sufficient lag between the two phases. This lag can be reduced in a multistage system and thus the time for getting good reduction in COD values can be shortened. However, before going on a plant scale these all these possibilities will have to be confirmed on a pilot plant scale. It will then be possible to propose an improved microbiological treatment method for distillery effluent.
[0059] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.

We Claim:

1. A system for treating wastewater from distillery effluent for biochemical oxygen demand (BOD) comprising:
a feeding duct for supplying the spentwash,
at least onefermentation vessel having bacteria for the uptake and
degradation of contaminants in the effluent,
at least one collecting vessel for the reception of the residual
water from the treatment vessel.
2. The system as claimed in claim 1 wherein, distillery spentwash is the unwanted residual liquid waste generated during alcohol production.
3. The system as claimed in claim 1 wherein, the bacteria in fermentation tank is anaerobic bacterial strains isolated from sewage waters.
4. A method of treating wastewater from distillery effluent for biochemical oxygen demand (BOD) comprising:
a. flowing spentwash through a first tank;
b. optimizing CO2 content of the spentwash by flowing into a second anaerobic reactor;
c. flowing the optimized CO2 effluent from the anaerobic reactor into a collecting tank.
5. The method as claimed in claim 4 wherein, the system is a continuous stirred tank reactor.
6. The method as claimed in claim 4 wherein,distillery spentwash is the unwanted residual liquid waste generated during alcohol production.
7. The method as claimed in claim 4 wherein, the anaerobic reactor comprises anaerobic bacterial strain II (PLCMA).

8. The method as claimed in claim 4 wherein, the anaerobic bacteria for sludge digestion yields about 75 to 80 percent reduction in COD.