IMPACT OF DISTILLERY EFFLUENT APPLICATION TO LAND ON SOIL MICROFLORA A S H A J U W A R K A R a n d S.A. D U T T A
National Environmental Engineering Research Institute, Nagpur 440 020, India
(Received January 1989) Abstract. A pot culture experiment was conducted to evaluate the effect of different treatments of distillery wastewater, i.e. raw, treated, diluted and raw distillery wastewater mixed with domestic waste stabilization pond effluent (1:1) on populations of bacteria, fungi, actinomycetes and nitrogen fixing bacteria. The results indicated that raw wastewater decreased the population of bacteria, fungi and actinomycetes. The growth rates of Rhizobium and Azotobacter were also reduced after raw wastewater application. The toxic effect of raw wastewater was minimized when it was mixed with stabilization pond effluent (1:1), this was demonstrated by an increase in the populations of all the microorganisms studied. When a groundnut plant was irrigated with raw distillery wastewater, no fruits were produced and there was also less nodulation. This study indicates that raw distillery wastewater is very toxic to the soil microorganisms which are important in the soil ecosystem.
Introduction Application of wastewater to the land, as an alternative or adjunct to more conventional methods of wastewater management, is receiving increased attention as a result of recent environmental concern and legislation. Although investigations on the toxic effect of distillery wastewater on the growth and productivity of plants have been made by some workers (Mohanrao and Sastry, 1964; Radhakrishnan et al., 1969; Sharma et al., 1973; Singh and Sahai, 1982), there is still insufficient information on its impact on soil microbiological properties. Soil microorganisms are an essential component of the soil ecosystem and are involved in regulating the various processes of nutrient recycling in soil. Any type of interference with their activity may affect soil productivity. TABLE I Range of physico-chemical characteristics of spent wash collected from different distilleries Factors
Range
Colour pH Total solids Total volatile solids COD Total Nitrogen Total Phosphate Total Sulphate
Dark brown 3.6 - 4.4 78025 - 107943 4926 - 5576 72792- 137697 1241 - 1876 2104 - 4840 2635 - 3930
Source: Sharma et al. (1973). Except pH all values are in mg L -~.
Environmental Monitoring and Assessment 15: 201-210, 1990. 9 1990KluwerAcademicPublishers. Printedin theNetherlands.
202
ASHA JUWARKAR
AND S.A. DUTTA
In India, sugarcane is the major crop and there are some 144 distilleries producing 900 million litres of alcohol from molasses and 13500 million litres of spent wash per year. The composition of spent wash is given in Table I. Microbiological examination of soils treated with distillery effluent revealed an absence of nitrogen fudng bacteria (Purushottam, 1986). The enzymatic activity of Vigna mungo was also affected by a higher concentration of distillery wastewater applied to land (Sahai et al., 1985). The present study was conducted to evaluate the effect of distillery effluent application to land on different groups of soil microorganisms and on the nodulation of groundnut plants. Materials and Methods
A pot culture experiment was conducted to evaluate the effect of distillery wastewater effluent on soil biota. Pots of 40 cm diameter were fdled with 12 kg of soil. MATERIALS
Soil Characteristics: The black cotton soil used in the study had 52.5% clay, 18.3% silt, 24.1% sand, 4.3% CaCo3, 0.2% organic carbon and pH 7.2. Treatments The treatments used were: (1) Raw distillery wastewater, (2) Diluted distillery wastewater (1:1), (3) Treated distillery wastewater (after anaerobic digestion), (4) Diluted treated distillery wastewater (1:1), (5) Raw distillery wastewater diluted with domestic waste stabilization pond effluent (1:1), (6) Tap water (control). The tap water was used for the dilution of wastewater. Treated distillery wastewater was obtained from two-staged anaerobic packed bed reactor unit fed with raw distillery wastewater, with four days retention time. For each treatment, three replications were used.
Application Pattern of Wastewater One litre of wastewater was added to each pot at weekly intervals.
Nodulation Study A groundnut crop was raised in the pots to study the effect of different treatments on nodulation of the crop. Five plants were maintained in each pot. The groundnut crop is of 145-150 days duration and the wastewater application was given at weekly intervals for up to three months. Following this, plants were harvested for nodulation and fruit study.
Microorganisms Microbiological examination of soil included total bacterial count, fungal count and counts of actinomycetes and nitrogen fixing bacteria, i.e. Azotobacter and Rhizobium.
IMPACT
OF DISTILLERY
EFFLUENT
APPLICATION
203
Media
Selective media were used for enumeration of different groups of microorganisms. For the total bacterial count, nutrient agar was used, for actinomycetes, Kenknight and Munaeir medium (Subbarao, 1977) was used and for fungi, Rose Bengal agar medium (Martin, 1950) was used. The Azotobacter population was enumerated by using Jensen's medium and for the Rhizobium population was used yeast extract mannitol agar medium containing congo red (Subba Rao, 1977). METHODS
Enumeration of microorganisms was done by a serial dilution method. 10 g of soil were serially diluted to the desired concentrations and 1 ml aliquot was used for pour plate method using the selective medium for each microorganism. The plates were incubated at 30 ~ for five days. The count was expressed as CFU -~ g of soil, where 1 CFU = 1 cell.
8
m Control
'~
~
,, E
0',
0
Raw Waste Water
n,
C]
Diluted Raw Waste Water
c
6
o .J
Treated
5
Raw Waste Water
X-----,X
Diluted T r e a t e d Raw Waste Water
0----0
Raw Waste Water + Stabilization Pond Effluent
I
i
i
I
t
2
3
4
Number of applications
Fig. 1. Effect of distillery waste water on bacterial population.
204
ASHA JUWARKAR
AND S.A. DUTTA
For the nodulation study, plants were uprooted from the pots without disturbing the root system and then washed gently with running water to remove extra mud. Observations were recorded for the numbers of nodules and fruits. The number of nodules and fruits was expressed as per plant. Chemical analysis of raw, treated distillery effluent and stabilization pond effluent was done by using the procedure described in Standard Methods (1985). Results and Discussion
The impact of distillery waste effluent on soil microbiological properties reveals that there are marked differences among the various microbial groups studied. EFFECT ON BACTERIAL, FUNGAL AND ACTINOMYCETE
The soil applied with different treatments of distillery wastewater showed variation in the populations of bacteria, fungi and actinomycetes, both qualitatively and quantitatively (Figures 1, 2, and 3). The irrigation of soil with raw distillery wastewater and diluted raw distillery wastewater resulted in a low overall bacterial count. However, the populations of
5
v
t.
1
2 Number
Fig. 2.
~ of
4
applications
Effect of distillery waste water on fungal population.
5
IMPACT
OF
DISTILLERY
EFFLUENT
205
APPLICATION
I O
t, E 0
c
Cll 0 .I
3
I
J
!
I
I
1
2
3
4
5
Number of
Fig. 3.
applications
Effect of distillery waste water on actinomycetes population.
fungi and actinomycetes showed an increasing trend. This indicates that the physicochemical properties of the wastewater are responsible for such changes. The pH of distillery wastewater is low (4.3) which is detrimental to the soil microflora, particularly bacteria and actinomycetes. Increase in the fungal population may be due to the creation of low pH of the soil which is favourable for the growth of fungi. It should also be noted that the total amount of solids is very high, i.e. 128720 mg 1-1which may create an imbalance for the autochthonus soil microflora. The more serious effects may be due to the dissolved solids, which may indirectly disturb the osmotic regulation, thereby killing the microflora. Low bacterial and actinomycetes populations may be the result of a combination of all these factors. It has been reported (Sharma et al., 1973) that because the application of the distillery wastewater has high COD, BOD, there is oxygen depletion in the soil, and this hampers the activity of soil microflora. Further application of distillery wastewater causes excess accumulation of salts in the soil, vis-vis increase in electrical conductivity of the soil. It has also been reported
206
ASHA J U W A R K A R AND S.A. DUTTA TABLE II Characteristics of different wastewater used in the study Parameters
Raw distillery wastewater
Anaerobically treated distillery wastewater
Stabilization pond effluent
Colour pH Total solids Total volatile solids COD Total Nitrogen Total Phosphate Total Sulphate Alagal concentration
Dark brown 4.3 128720 45000 85000 817 40 2515 -
Straw yellow 6.8 1014 634 12000 28 9.8 2200 -
Yellowish green 8.2 91 30 6.93 150 mg L
Except pH all values are in mg L 1
(Purushottam et al., 1986) that high salinity affects the vegetation grown on distillery wastewater irrigated soils. It can be clearly deduced from these results that the application of distillery wastewater is more harmful to the bacterial and actinomycetes population than it is to the fungal population. Application of treated distillery wastewater after anaerobic digestion also resulted in a reduction of the microbial count, but not to the same extent as that from raw distillery wastewater. The physico-chemical characteristics of anaerobically treated wastewater are presented in Table II, which shows that the pollution load is less than that of raw distillery effluent. This may be the reason for the increase in microbial numbers as compared to raw effluent. Mixing of raw distillery wastewater with the stabilization pond effluent (1:1 ratio) resulted in an increase in the total bacterial count. It can therefore be concluded from the above discussion that microorganisms in the soil are very sensitive to extraneous matter and any addition of such matter should be studied in detail before its use in the field. E F F E C T ON NITROGEN FIXING BACTERIA
Figures 4 and 5 show that the population of nitrogen fixing bacteria, i.e. Rhizobium and Azotobacter decreased considerably after the application of raw distillery wastewater and diluted distillery wastewater. This may be due to the low pH of the distillery wastewater, as it is known that nitrogen fLxing bacteria are very sensitive to pH and their metabolic activity is arrested by low pH. The treatment of soil with anaerobically digested wastewater slightly increased the populations of these microorganisms. The pH of the treated wastewater ranged from 6.8-7.0 and this pH seems to be favourable for their growth. It was also observed that when raw distillery wastewater was diluted with stabilization pond effluent (1:1 ) it did not adversely affect the population of nitrogen fixing bacteria as much as it was affected by raw distillery wastewater alone. In this context, the role of algae
IMPACT
OF
DISTILLERY
EFFLUENT
207
APPLICATION
6fl
,\ \
\
\ \ \ \
5
\
el
;3 E -i l: ol O
..J
b
1
I
I
!
1
2
3
Fig. 4.
a
4
|
5
Number of a p p l l c a t | o n $ Effect of distillery waste water on Rhizobiura population.
present in the stabilization pond effluent seems to be important. In soil, the algae are known to synthesize carbonaceous materials from CO2 and after their death, the organic matter present in their cells supports the growth of bacteria and occasionally fungi (Alexander, 1977). The increase in the populations of bacteria and nitrogen fixing bacteria observed in our study might be due to the availability of extra carbonaceous matter contributed by algal biomass which have entered the soil through the stabilization pond
208
ASHA
JUWARKAR
AND
S.A. DUTTA
g
\\
\x\\
--o,
% \
\
% \
% % N
O to
4
.Q
s:
0 ..J
I 1
I
I
2
3
Number Fig. 5.
of
J
4
applications
Effect of distillery waste water on Azotobacter population.
la
I M P A C T O F DISTILLERY E F F L U E N T A P P L I C A T I O N
209
effluent. SPE also provides nutrients in a more mineralized form, and this may also help to increase their population. E F F E C T ON N O D U L A T I O N
As can be seen in Table III, nodulation of groundnut plants was affected by different treatments of distillery wastewater. Irrigation of groundnut plants with raw distillery wastewater resulted in a reduction of nodulation and an absence of fruit formation on the plants. From these observations, some points are apparent regarding the inhibitory effect of raw distillery wastewater on the symbiotic relationships of the groundnut plant. However, when raw wastewater was diluted to 50% by tap water, the inhibitory effect was somewhat reduced and the percentage variation was also far less i.e, 11.32 in nodulation and 4.76 in fruit formation respectively. It is recognized that high levels of ammonical nitrogen are inhibitory to nodulation and nitrogen fLxation. Ajmal and Khan (1984) also reported that raw distillery wastewater decreased the germination of the pea by 80 to 90%, but when the effluent was diluted to 50% with water, germination was enhanced. It was also noted that dilution of raw distillery wastewater with stabilization pond effluent (1:1 ), increased the nodulation and fruitformation of groundnut plants and it was on a par with the control. A similar trend was observed with the Rhizobium population in soil irrigated with the same combination. Irrigation of groundnut plants with treated distillery effluent and diluted treated distillery effluent did not result in a reduction of nodulation of the formation of fruit. The characteristics of treated distillery wastewater are presented in Table II, which suggests that a suitable pH and low concentrations of ammonical nitrogen may be the reasons for a less inhibitory effect of this effluent on nodulation and fruit formation. Based on these results, it is concluded that studies of this kind are very important in formulating and evaluating the method of land disposal of wastewaters, as soil microorganisms are indices of soil fertility. Their assessment under wastewater application provides information on the possible impact of particular wastewater on the soil TABLE III Effect of distillery wastewater on nodulation and fruit formation Treatments
1. Raw distillery wastewater 2. Raw distillery wastewater diluted with water (1:1) 3. Raw distillery waste water diluted with stabilization pond effl,mnt (1:1) 4. Treated distillery wastewater 5. Treated distillery wastewater diluted with stabilized pond effluent (1:1 ) 6. Tap water (control) 'Average of 3 replications.
Number of nodules' plants
% variation
Number of fruits a plants
% variation
12 57
92.45 64.15
5
76.19
141
11.32
20
4.76
102 119
35.84 25.15
9 14
57.14 33.33
159
21
210
ASHA JUWARKAR AND S.A. DUTTA
ecosystem. Hence, for any type of waste disposal studies on land, due criteria should be reserved for these micro entities. Findings also reveal that there are invariably quantitative changes in the composition of soil microflora due to different wastewater treatments. However, the degree of treatment influences the qualitative and quantitative changes in microbial populations.
Acknowledgements We are grateful to Dr. S. N. Kaul for providing the Distillery Wastewater Effluent and Dr. K. P. Krishnamoorthi, Head, Life Sciences Division for suggestions made during the investigation. We are also grateful to Professor P. Khanna, Director, National Environmental Engineering Research Institute, Nagpur for encouragement during the course of study.
References Ajmal, M. and Khan, A. O.: 1984, 'Effects of Brewery Effluent on Agricultural Soil and Crop Plants',Environ. Pollution (Series B) 33, 341-351. Alexander, M.: 1977, Introduction to SoilMicrobiology, second edition, Pub. John Wiley & Sons, U.S.A., p. 85. Martin, J. P.: 1950, 'Use of Acid, Rose Bengal and Streptomycin in the Plate Method for Estimating Soil Fungi', Soil Science 69, 215. Mohanrao, G. J. and Sastry, C. A.: 1964, 'Treatment and Disposal of Distillery Waste', Chem. Age of India 15, (1). Purushottam, D., Gunasekaran, and Oblisami, G.: 1986, 'Effect of Distillery Effluent on Certain Microbial Qualities of Soil and Plant Growth', Proceedings of the Symposium AMI, held at Nagpur, India, 18-20 December, 41. Radhakrishnan, J. S., De, S. B., and Nath, B.: 1969, 'Evaluation of Loading Parameters for Anaerobic Digestion of Cane Molasses Distillery Waste', J. Water Pollut. Control Federation 41, 431. Sahai, R., Jabeen S., and Saxena, P. K.: 1985, 'Nitrate Reductase Activity of Vigna mungo (L), Hepper as Affected by Distillery Waste', J. Environ. Bio, 116 (3), 205-209. Sharma, K. D., Bhatt, N. M., Kantawala, D., and Iyengar, M. R. S.: 1973, 'Studies on Aerobic Cultivation of Yeast to Reduce Cultivation of Distillery Waste', Ind. J. Env. Hlth 15, 118-126. Singh, S. P. and Sahai, R.: 1985, 'Effect of Distillery Waste on the Distribution Pattern and Growth Behaviour of Aquatic Macrophytes', Current Trends in Life Sciences, L. P. Mall's Commemoration Volume 9, pp. 263-269. Standard Method for Examination of Water and Wastewater: 1985, Published by APHA, AWWA and WPCF, 16th Edition, Washington, D.C. Subbarao, B.: 1971, 'Disposal of Distillery Waste Effluent by Anaerobic Lagoons Part 1, Ind. J. Env. Hlth. 13 (3), 187. Subbarao, N. S.: 1977, SoilMicroorganism andPlant Growth, Pub. Mohan Primlani, Oxford and IBH Public Co., New Delhi.
National Environmental Engineering Research Institute, Nagpur 440 020, India
(Received January 1989) Abstract. A pot culture experiment was conducted to evaluate the effect of different treatments of distillery wastewater, i.e. raw, treated, diluted and raw distillery wastewater mixed with domestic waste stabilization pond effluent (1:1) on populations of bacteria, fungi, actinomycetes and nitrogen fixing bacteria. The results indicated that raw wastewater decreased the population of bacteria, fungi and actinomycetes. The growth rates of Rhizobium and Azotobacter were also reduced after raw wastewater application. The toxic effect of raw wastewater was minimized when it was mixed with stabilization pond effluent (1:1), this was demonstrated by an increase in the populations of all the microorganisms studied. When a groundnut plant was irrigated with raw distillery wastewater, no fruits were produced and there was also less nodulation. This study indicates that raw distillery wastewater is very toxic to the soil microorganisms which are important in the soil ecosystem.
Introduction Application of wastewater to the land, as an alternative or adjunct to more conventional methods of wastewater management, is receiving increased attention as a result of recent environmental concern and legislation. Although investigations on the toxic effect of distillery wastewater on the growth and productivity of plants have been made by some workers (Mohanrao and Sastry, 1964; Radhakrishnan et al., 1969; Sharma et al., 1973; Singh and Sahai, 1982), there is still insufficient information on its impact on soil microbiological properties. Soil microorganisms are an essential component of the soil ecosystem and are involved in regulating the various processes of nutrient recycling in soil. Any type of interference with their activity may affect soil productivity. TABLE I Range of physico-chemical characteristics of spent wash collected from different distilleries Factors
Range
Colour pH Total solids Total volatile solids COD Total Nitrogen Total Phosphate Total Sulphate
Dark brown 3.6 - 4.4 78025 - 107943 4926 - 5576 72792- 137697 1241 - 1876 2104 - 4840 2635 - 3930
Source: Sharma et al. (1973). Except pH all values are in mg L -~.
Environmental Monitoring and Assessment 15: 201-210, 1990. 9 1990KluwerAcademicPublishers. Printedin theNetherlands.
202
ASHA JUWARKAR
AND S.A. DUTTA
In India, sugarcane is the major crop and there are some 144 distilleries producing 900 million litres of alcohol from molasses and 13500 million litres of spent wash per year. The composition of spent wash is given in Table I. Microbiological examination of soils treated with distillery effluent revealed an absence of nitrogen fudng bacteria (Purushottam, 1986). The enzymatic activity of Vigna mungo was also affected by a higher concentration of distillery wastewater applied to land (Sahai et al., 1985). The present study was conducted to evaluate the effect of distillery effluent application to land on different groups of soil microorganisms and on the nodulation of groundnut plants. Materials and Methods
A pot culture experiment was conducted to evaluate the effect of distillery wastewater effluent on soil biota. Pots of 40 cm diameter were fdled with 12 kg of soil. MATERIALS
Soil Characteristics: The black cotton soil used in the study had 52.5% clay, 18.3% silt, 24.1% sand, 4.3% CaCo3, 0.2% organic carbon and pH 7.2. Treatments The treatments used were: (1) Raw distillery wastewater, (2) Diluted distillery wastewater (1:1), (3) Treated distillery wastewater (after anaerobic digestion), (4) Diluted treated distillery wastewater (1:1), (5) Raw distillery wastewater diluted with domestic waste stabilization pond effluent (1:1), (6) Tap water (control). The tap water was used for the dilution of wastewater. Treated distillery wastewater was obtained from two-staged anaerobic packed bed reactor unit fed with raw distillery wastewater, with four days retention time. For each treatment, three replications were used.
Application Pattern of Wastewater One litre of wastewater was added to each pot at weekly intervals.
Nodulation Study A groundnut crop was raised in the pots to study the effect of different treatments on nodulation of the crop. Five plants were maintained in each pot. The groundnut crop is of 145-150 days duration and the wastewater application was given at weekly intervals for up to three months. Following this, plants were harvested for nodulation and fruit study.
Microorganisms Microbiological examination of soil included total bacterial count, fungal count and counts of actinomycetes and nitrogen fixing bacteria, i.e. Azotobacter and Rhizobium.
IMPACT
OF DISTILLERY
EFFLUENT
APPLICATION
203
Media
Selective media were used for enumeration of different groups of microorganisms. For the total bacterial count, nutrient agar was used, for actinomycetes, Kenknight and Munaeir medium (Subbarao, 1977) was used and for fungi, Rose Bengal agar medium (Martin, 1950) was used. The Azotobacter population was enumerated by using Jensen's medium and for the Rhizobium population was used yeast extract mannitol agar medium containing congo red (Subba Rao, 1977). METHODS
Enumeration of microorganisms was done by a serial dilution method. 10 g of soil were serially diluted to the desired concentrations and 1 ml aliquot was used for pour plate method using the selective medium for each microorganism. The plates were incubated at 30 ~ for five days. The count was expressed as CFU -~ g of soil, where 1 CFU = 1 cell.
8
m Control
'~
~
,, E
0',
0
Raw Waste Water
n,
C]
Diluted Raw Waste Water
c
6
o .J
Treated
5
Raw Waste Water
X-----,X
Diluted T r e a t e d Raw Waste Water
0----0
Raw Waste Water + Stabilization Pond Effluent
I
i
i
I
t
2
3
4
Number of applications
Fig. 1. Effect of distillery waste water on bacterial population.
204
ASHA JUWARKAR
AND S.A. DUTTA
For the nodulation study, plants were uprooted from the pots without disturbing the root system and then washed gently with running water to remove extra mud. Observations were recorded for the numbers of nodules and fruits. The number of nodules and fruits was expressed as per plant. Chemical analysis of raw, treated distillery effluent and stabilization pond effluent was done by using the procedure described in Standard Methods (1985). Results and Discussion
The impact of distillery waste effluent on soil microbiological properties reveals that there are marked differences among the various microbial groups studied. EFFECT ON BACTERIAL, FUNGAL AND ACTINOMYCETE
The soil applied with different treatments of distillery wastewater showed variation in the populations of bacteria, fungi and actinomycetes, both qualitatively and quantitatively (Figures 1, 2, and 3). The irrigation of soil with raw distillery wastewater and diluted raw distillery wastewater resulted in a low overall bacterial count. However, the populations of
5
v
t.
1
2 Number
Fig. 2.
~ of
4
applications
Effect of distillery waste water on fungal population.
5
IMPACT
OF
DISTILLERY
EFFLUENT
205
APPLICATION
I O
t, E 0
c
Cll 0 .I
3
I
J
!
I
I
1
2
3
4
5
Number of
Fig. 3.
applications
Effect of distillery waste water on actinomycetes population.
fungi and actinomycetes showed an increasing trend. This indicates that the physicochemical properties of the wastewater are responsible for such changes. The pH of distillery wastewater is low (4.3) which is detrimental to the soil microflora, particularly bacteria and actinomycetes. Increase in the fungal population may be due to the creation of low pH of the soil which is favourable for the growth of fungi. It should also be noted that the total amount of solids is very high, i.e. 128720 mg 1-1which may create an imbalance for the autochthonus soil microflora. The more serious effects may be due to the dissolved solids, which may indirectly disturb the osmotic regulation, thereby killing the microflora. Low bacterial and actinomycetes populations may be the result of a combination of all these factors. It has been reported (Sharma et al., 1973) that because the application of the distillery wastewater has high COD, BOD, there is oxygen depletion in the soil, and this hampers the activity of soil microflora. Further application of distillery wastewater causes excess accumulation of salts in the soil, vis-vis increase in electrical conductivity of the soil. It has also been reported
206
ASHA J U W A R K A R AND S.A. DUTTA TABLE II Characteristics of different wastewater used in the study Parameters
Raw distillery wastewater
Anaerobically treated distillery wastewater
Stabilization pond effluent
Colour pH Total solids Total volatile solids COD Total Nitrogen Total Phosphate Total Sulphate Alagal concentration
Dark brown 4.3 128720 45000 85000 817 40 2515 -
Straw yellow 6.8 1014 634 12000 28 9.8 2200 -
Yellowish green 8.2 91 30 6.93 150 mg L
Except pH all values are in mg L 1
(Purushottam et al., 1986) that high salinity affects the vegetation grown on distillery wastewater irrigated soils. It can be clearly deduced from these results that the application of distillery wastewater is more harmful to the bacterial and actinomycetes population than it is to the fungal population. Application of treated distillery wastewater after anaerobic digestion also resulted in a reduction of the microbial count, but not to the same extent as that from raw distillery wastewater. The physico-chemical characteristics of anaerobically treated wastewater are presented in Table II, which shows that the pollution load is less than that of raw distillery effluent. This may be the reason for the increase in microbial numbers as compared to raw effluent. Mixing of raw distillery wastewater with the stabilization pond effluent (1:1 ratio) resulted in an increase in the total bacterial count. It can therefore be concluded from the above discussion that microorganisms in the soil are very sensitive to extraneous matter and any addition of such matter should be studied in detail before its use in the field. E F F E C T ON NITROGEN FIXING BACTERIA
Figures 4 and 5 show that the population of nitrogen fixing bacteria, i.e. Rhizobium and Azotobacter decreased considerably after the application of raw distillery wastewater and diluted distillery wastewater. This may be due to the low pH of the distillery wastewater, as it is known that nitrogen fLxing bacteria are very sensitive to pH and their metabolic activity is arrested by low pH. The treatment of soil with anaerobically digested wastewater slightly increased the populations of these microorganisms. The pH of the treated wastewater ranged from 6.8-7.0 and this pH seems to be favourable for their growth. It was also observed that when raw distillery wastewater was diluted with stabilization pond effluent (1:1 ) it did not adversely affect the population of nitrogen fixing bacteria as much as it was affected by raw distillery wastewater alone. In this context, the role of algae
IMPACT
OF
DISTILLERY
EFFLUENT
207
APPLICATION
6fl
,\ \
\
\ \ \ \
5
\
el
;3 E -i l: ol O
..J
b
1
I
I
!
1
2
3
Fig. 4.
a
4
|
5
Number of a p p l l c a t | o n $ Effect of distillery waste water on Rhizobiura population.
present in the stabilization pond effluent seems to be important. In soil, the algae are known to synthesize carbonaceous materials from CO2 and after their death, the organic matter present in their cells supports the growth of bacteria and occasionally fungi (Alexander, 1977). The increase in the populations of bacteria and nitrogen fixing bacteria observed in our study might be due to the availability of extra carbonaceous matter contributed by algal biomass which have entered the soil through the stabilization pond
208
ASHA
JUWARKAR
AND
S.A. DUTTA
g
\\
\x\\
--o,
% \
\
% \
% % N
O to
4
.Q
s:
0 ..J
I 1
I
I
2
3
Number Fig. 5.
of
J
4
applications
Effect of distillery waste water on Azotobacter population.
la
I M P A C T O F DISTILLERY E F F L U E N T A P P L I C A T I O N
209
effluent. SPE also provides nutrients in a more mineralized form, and this may also help to increase their population. E F F E C T ON N O D U L A T I O N
As can be seen in Table III, nodulation of groundnut plants was affected by different treatments of distillery wastewater. Irrigation of groundnut plants with raw distillery wastewater resulted in a reduction of nodulation and an absence of fruit formation on the plants. From these observations, some points are apparent regarding the inhibitory effect of raw distillery wastewater on the symbiotic relationships of the groundnut plant. However, when raw wastewater was diluted to 50% by tap water, the inhibitory effect was somewhat reduced and the percentage variation was also far less i.e, 11.32 in nodulation and 4.76 in fruit formation respectively. It is recognized that high levels of ammonical nitrogen are inhibitory to nodulation and nitrogen fLxation. Ajmal and Khan (1984) also reported that raw distillery wastewater decreased the germination of the pea by 80 to 90%, but when the effluent was diluted to 50% with water, germination was enhanced. It was also noted that dilution of raw distillery wastewater with stabilization pond effluent (1:1 ), increased the nodulation and fruitformation of groundnut plants and it was on a par with the control. A similar trend was observed with the Rhizobium population in soil irrigated with the same combination. Irrigation of groundnut plants with treated distillery effluent and diluted treated distillery effluent did not result in a reduction of nodulation of the formation of fruit. The characteristics of treated distillery wastewater are presented in Table II, which suggests that a suitable pH and low concentrations of ammonical nitrogen may be the reasons for a less inhibitory effect of this effluent on nodulation and fruit formation. Based on these results, it is concluded that studies of this kind are very important in formulating and evaluating the method of land disposal of wastewaters, as soil microorganisms are indices of soil fertility. Their assessment under wastewater application provides information on the possible impact of particular wastewater on the soil TABLE III Effect of distillery wastewater on nodulation and fruit formation Treatments
1. Raw distillery wastewater 2. Raw distillery wastewater diluted with water (1:1) 3. Raw distillery waste water diluted with stabilization pond effl,mnt (1:1) 4. Treated distillery wastewater 5. Treated distillery wastewater diluted with stabilized pond effluent (1:1 ) 6. Tap water (control) 'Average of 3 replications.
Number of nodules' plants
% variation
Number of fruits a plants
% variation
12 57
92.45 64.15
5
76.19
141
11.32
20
4.76
102 119
35.84 25.15
9 14
57.14 33.33
159
21
210
ASHA JUWARKAR AND S.A. DUTTA
ecosystem. Hence, for any type of waste disposal studies on land, due criteria should be reserved for these micro entities. Findings also reveal that there are invariably quantitative changes in the composition of soil microflora due to different wastewater treatments. However, the degree of treatment influences the qualitative and quantitative changes in microbial populations.
Acknowledgements We are grateful to Dr. S. N. Kaul for providing the Distillery Wastewater Effluent and Dr. K. P. Krishnamoorthi, Head, Life Sciences Division for suggestions made during the investigation. We are also grateful to Professor P. Khanna, Director, National Environmental Engineering Research Institute, Nagpur for encouragement during the course of study.
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