Potential of EM for Conventional Activated Sludge Upgrade

International Water Technology Journal, IWTJ Vol. 3 - Issue 2, June 2013

87

POTENTIAL OF EFFECTIVE MICROORGANISMS (EM) FOR

CONVENTIONAL ACTIVATED SLUDGE UPGRADE

El Karamany H.M.

1, El Shatoury S.A.

2, Ahmed D.S.

1, and Saleh I.S.

1

1 Environmental Engineering department, Faculty of Engineering, Zagazig University, Egypt

2 Botany department, Faculty of Science, Suez Canal University, Egypt

ABSTRACT

Activated sludge process is widely used for wastewater treatment throughout the world with various

modifications. The aim of this research was to study the effect of using effective microorganisms (EM)

to enhance the activated sludge process. A model has been constructed to simulate activated sludge

process. It consisted of two reactors (EM-dosed and control) operated simultaneously. The results of

the present study showed that the reactor induced with EM achieved removal ratios of 84.5%, 91.5%

and 96.0% in TSS, COD and BOD respectively compared to 63.5%, 66.0% and 74.0% in the control

reactor. Increasing EM dose from (1/7500) to (1/1000), increasing COD and BOD removal ratios

from 71.0%, 75.5% to 91.5%, 96.0% respectively compared to 68.0%, 74.0% in the control reactor .

Also results indicated that the pulse dose addition method achieved higher efficiency in early days (7

days), 90.0% and 94.5% for COD and BOD respectively compared to 78.0%, 82.5% in daily dose

method. However, the daily EM dose method showed higher removal efficiency at the long run

application (one month) 92.0%, 85.7% for COD and BOD respectively compared to 82.5%, 76.0% in

pulse dose method. EM dose (1/1000) showed significant higher removal ratios at lower hydraulic

retention time (HRT=4 hours), where the EM reactor achieved removal efficiency for COD and BOD

were 84.5% and 91.5% respectively compared to 92.0%, 96.5% at the control reactor. Enzymes

evaluation showed that the enzymatic activity of EM have more ability in the oxidation of organic

materials than of bacteria found in the control reactor.

Keywords: Effective microorganisms (EM), Activated sludge upgrade, COD removal, bacterial count, HRT.

1. INTRODUCTION

More than 80% of biological wastewater treatment plants (WWTPs) are based on the principle of

activated sludge process, in which suspended bacteria oxidize the carbonaceous and nitrogenous

compounds to produce an effluent in accordance with legal standards, and that corresponds to a

minimal environmental impact. [Metcalf & Eddy, 2003].

Most large cities in Egypt had already built their wastewater treatment plants as activated sludge

process plants. Some of these plants are suffering from over loading problems. These problems due to

increase in population and standard of living that Led to increase in wastewater discharges. The

increase of organic and hydraulic loads, related to the improvement of wastewater collection, and the

implementation of new national regulations and directives, often leads to discharges which do not

comply with the standards.

The concept of EM was developed by Japanese horticulturist Teuro Higa from the University of

Ryukyus in Japan. He reported in the 1970s that a combination of approximately 80 different

microorganisms is capable of positively influencing decomposing organic matter such that it reverts

into a life promoting process. This selection was done from over two thousand species of microbes

found in all environments. EM is developed using three principal organisms, namely phototrophic


87

bacteria, Lactic acid bacteria and Yeasts. Thus, EM consists of these three principal types, which is

subsequently enriched naturally by other species such as filamentous fungi and Actinomycetes [Higa,

1996].

In the current wastewater treatment process, microorganisms play a significant role in the treatment

of domestic sewage. Many different organisms live within the wastewater itself, assisting in the

breakdown of certain organic pollutants [Taylor, et al 1997]. The basis for using these EM species of

microorganisms is that they contain various organic acids due to the presence of lactic acid bacteria,

which secrete organic acids, enzymes, antioxidants and metallic chelates. The creation of an

antioxidant environment by EM assists in the enhancement of the solid-liquid separation, which is the

foundation for cleaning water. [Higa and Chinen 1998].

Concerning the research in hand, various parameters have been examined to test the effect of EM on

enhancing the quality of the existing conventional activated sludge WWTPs. Those parameters

included the change in EM dosing, method of dose addition, and hydraulic retention times. In addition,

biological tests have been conducted on the enzymes of EM and compared to the enzymes of the

bacteria present in the control reactor

2. MATERIALS AND METHODS

2.1 Wastewater Characteristics

In this study the used wastewater was collected from the effluent channel of primary sedimentation

tanks in "El Aslogy wastewater treatment plant", Zagazig, Egypt. The measured parameters were

COD, BOD, TSS, temperature, DO and pH. All these parameters were measured in Environmental

Engineering Laboratory, Engineering Faculty, Zagazig, Egypt according to the American Standard

Methods for the Examination of Water and Wastewater [APHA, 2005]. The wastewater characteristics

in this study as shown in Table (1).

2.2 Effective Microorganisms (EM)

Effective microorganisms (EM) used in this study was obtained from Egyptian environmental affairs

agency (EEAA). EM solution is a yellowish liquid with a pleasant odor and sweet sour taste with a pH

of 2.8 and stored in area with minimal temperature fluctuations due to don't affect on the survival of

microorganisms. EM culture contained a mixture of lactic acid bacteria, phototrophic bacteria, yeast,

actinomycetes and fermenting fungi.

Table 1: The physical-chemical characteristics of inlet wastewater

Unit Average value Parameter

mg/l

mg/l

mg/l

mg/l

------

Celsius

56550

37035

37545

2.680.92

7.70.25

268

Chemical oxygen demand (COD)

Biochemical oxygen demand (BOD)

Total suspended solids (TSS)

Dissolved oxygen (DO)

PH value

Temperature

2.3 Experimental Model

The used experimental model consisted of a feeding tank ahead of two reactors; one of the two

reactors represented the reference and the other was used for the addition of EM as shown in Figure

(1). Each reactor consisted of an aeration tank and final sedimentation tank with dimensions as

illustrated in table (2).


78

Table 2: Model's dimensions.

Capacity(Liter) Diameter

(mm) height (m) width (m)

length

(m) Units

96

31

25

-----

-----

-----

-----

12.7

0.60

0.31

0.40

-----

0.40

0.25

0.25

-----

0.40

0.40

0.25

-----

Head tank

Aeration tank

Final Sedimentation tank

All pipes

Manhole

R.S.L

Air supply

Head tank

* One reactor for control and another for EM study

EM solution

Adding

Pump

AT

FST

RSL

Aeration Tank

Final Sedimentation Tank

Return Sludge Line

R.S.L

Effluent

Effluent

E.S.L

ESL Excess Sludge Line

E.S.L

Supply pump

Effluent channel

Pump

of primary sedimentation tank

reactor

control

Air supply

Fig. 1: Schematic diagram for the bench scale model.

The model was set at the effluent channel of primary sedimentation tanks in "El Aslogy wastewater

treatment plant", Zagazig, Egypt as shown in figure (1). One horse power pump was used to raise the

wastewater from the channel to the head tank. The head tank was provided with two valves and two

pipes 0.5 inch in diameter to distribute the wastewater on the aeration tanks. The wastewater moved

from the aeration tanks to final sedimentation tanks through pipes 12.7 mm in diameter. The return

sludge is recycled to the aeration tanks by two pumps. Sludge was withdrawn from the sedimentation

tank once a day to keep the SRT at the designated values. This arrangement was adjusted by using an

electronic control system using a timer (24 hr). The supplied air quantity was sufficient to maintain

dissolved oxygen concentration in the range of 2mg/l - 4 mg/l.

2.4 Model Start Up

The conventional way of start-up of wastewater treatment plant is to inoculate a large amount of

fresh activated sludge to the aeration tank and acclimatize the sludge for the high removal of organic

materials. In this the model, approximately 10 liters of activated sludge (based on Qr = 0.5Q) were

added to each aeration tank in the start of each run. The start up period ranged between (10 15) days based on characteristics of both return activated sludge and influent wastewater into model.

2.5 Experimental Procedure

In the present study the two reactors worked together in the same atmospheric conditions, flow rates,

raw wastewater and retention time. The experimental program was established on three stages.

In the first stage the effect of different EM doses was studied. This stage included four runs. Each

run carried out using different dose of EM added daily to the reactor in the same time of each day.

These doses based on the ratio of volume of EM to the volume of aeration tank, were (1/1000),

(1/2500), (1/5000) and (1/7500). The selected major enzyme activities of the EM and the conventional

activated sludge were evaluated in this stage to show the differences in their abilities to degrade

organic matter. These tests were amylase, lipase, protease and cellulose. Enzymatic screening was


78

performed for the whole microbial population by transferring 0.1 ml from the sample directly to a well

in the corresponding medium plate. In parallel, activities of individual cells were investigated by serial

dilution of the samples in phosphate buffer and cultivation, as described above. Enzymatic activities

were measured as activity index (diameter of clear zone / diameter of growth) after incubation at 28C

for 7days (21 days for carboxymethyl cellulase CMCase). Enzymatic activities were investigated as follows:

Amylase activity: Samples were inoculated in Starch Agar medium plates, incubated for 14 days at

28C, then covered by Gram's iodine solution, which allowed the visualization of clear halos around

the colonies that produced amylase (Williams and Wellington, 1982).

Lipase activity: Samples were grown on Tributyrin agar plates. The clear zone around the growth

indicated the lipase production (Janda, 2005).

Protease activity: Samples were grown on Skim milk agar (Williams and Wellington, 1982).

Enzyme production was indicated by clear zones around the growth.

CMCase activity: Samples were grown on cellulose agar medium, supplemented with

carboxymethyl cellulose as a sole carbon source (Wollum, 1982). Enzymes production was indicated

by clear zones around the growth.

In the second stage, two methods of addition of EM dose (1/1000), daily EM dose method and pulse

method. The two methods were compared to achieve long steady state period with high removal

efficiency over one month. (Note; pulse addition method was the total amount of EM over month

added only once at the start of the run).

In the third stage, the effect of hydraulic retention time (2, 4, 6 and 8 hour) at EM dose (1/1000) was

studied and compared the results with control reactor. The boundary operating conditions of three

stages are displayed in Table (3). Working conditions and procedures were rigorously followed during

all experiments.

Table 3: The operational conditions applied through the whole study

stage Runs EM addition method EM dose Qa (L/d) Qr

b (L/d) HRT

c(hr)

1st

1st run

2nd

run

3rd

run

4th run

daily

daily

daily

daily

1/5000

1/7500

1/2500

1/1000

124

124

124

124

62

62

62

62

6

6

6

6

2nd

5

th run

6th run

daily

Pulse

1/1000

1/1000

124

124

62

62

6

6

3rd

7th run daily 1/1000

93, 124,

186 and

372

46.5, 62,

93 and

186

8, 6, 4

and 2

a = inlet wastewater flow rate (liter/day),

b = return activated sludge flow rate (liter/day)

c = hydraulic retention time (hours)

3. RESULTS AND DISCUSSION 3.1. Effect of using EM

The results showed that using EM increased TSS, COD and BOD removal ratios differed

significantly compared to the control (p< 0.05), particularly with higher EM dose. For example figure

(4) illustrated that using EM dose (1/1000) achieved BOD removal ratio 96.0% compared to 74.0% in

control reactor.


78

Increasing the performance of an existing activated sludge system would be necessary by increasing

the amount of biomass inside the reactor. In theory, the higher the MLSS concentration in the aeration

tanks the greater efficiency of the process because the higher biomass can utilize the more available

organic matter. According to figure (5), the bacterial count for EM reactor achieved (1.3*10^8 cfu/ml)

compared to (1.6*10^6 cfu/ml) in the control reactor. This means that EM reactor contain the higher

amount of biomass inside the reactor. In addition to the species contained in EM produce various

organic acids due mainly to the presence of lactic acid bacteria. The EM secretes organic acids and

enzymes which acts on sewage and degrades complex organic matter into simpler ones. The

antioxidant substances produced by EM enhances the breakdown of Solids and reduces the sludge

volume [Higa & Chinen, 1998].

These results comply with Namsivayam, et al (2011), whose experimental model consists of 2l

Erlenmeyer flask with 1 liter of domestic sewage.100 ml of activated EM culture was added into the

sewage sample. The setup was operated continuously for 20 days. EM was added each day at the

dilution rate of 1:10,000 for five days. Their results refer to BOD was reduced from 2.8 to 0.9 mg/l.

3.2. Effect of EM dose

It was found that when the EM dose was (1/7500), the results were 65.0%, 71.0% and 75.5% in

removal efficiency of TSS, COD and BOD respectively compared to 64.0%, 68.5% and 74.0% in

control reactor as shown in figures (2, 3 and 4). While when the EM dose was (1/5000), the removal

efficiency of TSS, COD and BOD were 68.0%, 75.0% and 81.0% respectively compared to 63.0%,

66.0% and 74.0% in control reactor. The EM dose (1/2500) achieved removal efficiency 75.0%,

83.5% and 91.0% of TSS, COD and BOD respectively compared to 62.0%, 67.5% and 75.0% in

control reactor. But the final EM dose (1/1000) achieved removal efficiency 83.5%, 91.5% and 96.0%

of TSS, COD and BOD respectively compared to 63.0%, 66.0% and 74.0% in control reactor.

Results indicated that EM dose higher than (1/1000) would offset small increasing in removal

efficiency for TSS, COD and BOD. Consequently the dose (1/1000) was selected as the highest dose

for the following experiments.

Fig. 2: TSS removal ratio for different EM doses compared to control (Ref.) reactor

40%

50%

60%

70%

80%

90%

0 3 6 9 12 15 18 21 24

Time(days)

TS

S r

em

oval r

atio

EM Reactor Ref. Reactor

40%

50%

60%

70%

80%

90%

0 3 6 9 12 15 18 21 24

Time(days)

TS

S r

em

oval r

atio


40%

50%

60%

70%

80%

90%

0 3 6 9 12 15 18 21 24

Time(days)

TS

S r

em

oval r

atio

Em reactor Ref. reactor

40%

50%

60%

70%

80%

90%

0 3 6 9 12 15 18 21 24

Time(days)

TS

S r

em

oval r

atio


EM dose = 1/7500

EM dose = 1/1000 EM dose = 1/2500

EM dose = 1/5000


78

This results obtained from this study indicate that suspended solids will be reduced. Higa (1993)

supported this statement through the example of the Gushikawa City Library, which when treated with

EM has reduced the need for solids handling and increasing the removal ratios in BOD and COD. Also

these results comply with the results of Monica, et al. (2011), where their results showed that

treatment of sewage using EM with addition of dose (1/300) under aerobic conditions reduced the

BOD from 374.5 to 55.9 mg/l with mean reduction of 85% while the control showed the decrease in

BOD from 374.5 to 248.6 mg/l with mean reduction of 34%. The EM reduced the COD of sewage

from 570.4 to 99.8 mg/l with mean reduction of 82% while the control showed the decrease in COD

from 570.4 to 409.3 mg/l with mean reduction of 28%.

3.3. Effect of EM on bacterial count

Microbiological analysis showed that, the bacterial counts changed significantly from the control

when using the doses (1/1000) and (1/2500) with significant values were (1.3*10^8 cfu/ml) and

(4.7*10^7 cfu/ml) respectively compared to (1.6*10^6 cfu/ml) and (2.2*10^6 cfu/ml) for control

reactor as shown in figure (5). Comparable results were reported by Namsivayam, et al (2011), where

application of dose (1/10000) resulted in a significant increase in bacterial population from 11.2X104

cfu/ml in control reactor to 23.1X105 cfu/ml in EM reactor.

According to figure (3, 4, 5) It is suggested that, the increase in bacterial count in EM dose (1/1000)

compared to (1/7500) was responsible for the recognized difference in removal efficiency. The bigger

population of EM bacteria cells adding to its high ability for degrading organic matter in the

wastewater would increasing the microbiological activity in the environment and the efficiency

treatment. Also, enzymatic investigation of the EM illustrates their Superiority compared to normal

bacteria found in wastewater as shown in Table (4). However, the use of EM does not only enhance

the microbes found in EM in that environment. It acts as a catalyst with a synergistic effect to promote

all the beneficial microbes of that environment. When this happens, the microbes that develop harmful

effects are excluded from that ecosystem, in a manner akin to human activity, where good people

weed out the bad ones (Higa 1998).

Fig. 3: COD removal ratio for different EM doses compared to control (Ref.) reactor

40%

50%

60%

70%

80%

90%

100%

0 3 6 9 12 15 18 21 24

times(day)

CO

D r

em

oval r

atio


40%

50%

60%

70%

80%

90%

100%

0 3 6 9 12 15 18 21 24

times(day)

CO

D r

em

ova

l ra

tio


40%

50%

60%

70%

80%

90%

100%

0 3 6 9 12 15 18 21 24

times(day)

CO

D r

em

oval r

atio


40%

50%

60%

70%

80%

90%

100%

0 3 6 9 12 15 18 21 24

times(day)

CO

D r

em

oval r

atio


EM dose = 1/7500

EM dose = 1/1000

EM dose = 1/5000

EM dose = 1/2500


78

Fig. 4: BOD removal ratio for different EM doses compared to control (Ref.) reactor

Fig. 5: Bacterial count for different EM doses compared to control (Ref.) reactor

3.4. Evaluation of EM Enzymes

The selected enzymes for this part of the study were the common enzymes which may be

found in wastewater, e.g. amylase, protease, lipase and carboxymethyl cellulose (CMCase).

30%

40%

50%

60%

70%

80%

90%

100%

0 3 6 9 12 15 18 21 24

times(day)

BO

D rem

oval r

atio

Em Reactor Ref. Reactor

30%

40%

50%

60%

70%

80%

90%

100%

0 3 6 9 12 15 18 21 24

times(day)

BO

D r

em

oval r

atio


30%

40%

50%

60%

70%

80%

90%

100%

0 3 6 9 12 15 18 21 24times(day)

BO

D r

em

oval r

atio

Em Reactorl Ref. Reactor

30%

40%

50%

60%

70%

80%

90%

100%

0 3 6 9 12 15 18 21 24

times(day)B

OD

rem

oval r

atio


EM dose = 1/7500

EM dose = 1/1000

EM dose = 1/5000

EM dose = 1/2500

5.0

6.0

7.0

8.0

9.0

0 3 6 9 12 15 18 21 24

Time(days)Log10 [

Cell

No.]

(cfu

/ml)


5.0

6.0

7.0

8.0

9.0

0 3 6 9 12 15 18 21 24

Time(days)Log10 [

Cell

No.]

(cfu

/ml)


5.0

6.0

7.0

8.0

9.0

0 3 6 9 12 15 18 21 24

Time(days)Log10 [

Cell

No.]

(cfu

/ml)

Em Reactor Ref.Reactor

5.0

6.0

7.0

8.0

9.0

0 3 6 9 12 15 18 21 24

Time(days)

Log10 [

Cell

No.]

(cfu

/ml)


EM dose = 1/7500

EM dose = 1/1000 EM dose = 1/2500

EM dose = 1/5000


78

Results of individual cells activities showed better representation of enzymatic activities,

compared to evaluation of the whole microbial population. Results indicated that EM

enzymes (amylase, protease and carboxymethyl cellulose) have more abilities than enzymes

of bacteria which found in control reactor and have the same ability almost in lipase enzyme

as shown in Table (4). This because the species contained in EM produce various organic

acids due mainly to the presence of lactic acid bacteria. The EM secretes organic acids and

enzymes which acts on sewage and degrades complex organic matter into simpler ones. The

antioxidant substances produced by EM enhances the breakdown of Solids and reduces the

sludge volume [Higa & Chinen, 1998].

Previous results showed that EM reproduces many survival cells of the EM within the

wastewater at the same hydraulic retention time rather than normal bacteria. Also EM

enzymes have greater abilities in the oxidation of various organic materials found in

wastewater.

Table 4: Average enzymatic activity indices of amylase, protease, lipase and carboxymethyl 85ellulose

(CMCase) for the two reactors.

Enzyme

EM reactor Control reactor

individual microbial

cells

microbial

population

individual microbial

cells

microbial

population

Amylase 7.12 6.6 3.11 3.22

Protease 3.66 3.53 No activity 2.40

Lipase 3.50 No activity 4.3 No activity

CMCase 5.56 No activity 3.0 No activity

3.5. Method of EM Addition

It was deduced that the pulse dose achieved higher efficiency in early days (7 days), were

90.0%, 94.5% for COD and BOD respectively compared to daily dose 78.0% and 82.5% as

shown in figure (6). This could be reasoned to the large amount of EM bacteria which

consumed most organic matter in the reactor. However, the daily EM dose showed higher

removal efficiency at the long run application (30 days), were 90.5%, 95.0% for COD and

BOD respectively compared to pulse dose 76.0 % and 82.5%. This indicates the possible

wash-out of EM cells from the reactor and the importance of continuous fed of the inoculants

to guarantee stable treatment efficiency. Therefore, the application regime could possibly

follow pulse addition method in case of needing rapidly high removal efficiency in short time. While the daily addition could be followed in cases when achieving high removal efficiency on long term is required.

Fig. 6: the effect of daily and pulse EM dose (1/1000) on removal ratio with time.

40%

50%

60%

70%

80%

90%

100%

0 3 6 9 12 15 18 21 24 27 30

times(day)

CO

D r

em

oval ra

tio

Em(Pulse) Reactor Em(daily) Reactor

40%

50%

60%

70%

80%

90%

100%

0 3 6 9 12 15 18 21 24 27 30

times(day)

BO

D r

em

oval ra

tio

EM(Pulse) Reactor EM(daily) Reactor


78

3.6. Effect of HRT on removal ratio with daily EM dose (1/1000)

At HRT equal to 4 hours, the EM reactor gave removal efficiency for TSS, COD, BOD

were 77.5%, 84.5%, and 91.5% respectively compared to 60.5%, 63.0% and 68.5% for the

control reactor as shown in figure (7). So, discharges of wastewater coming to treatment

plants may be doubled while maintaining high removal ratios.

Fig. 7: the effect of HRT on removal ratio with daily EM dose (1/1000).

4. CONCLUSIONS

Based on the experimental program executed in this research, and limited to both the tested materials

and the testing procedures employed, the following conclusions have been reached:

Increase EM dose, increase TSS, BOD and COD removal ratios.

The highest EM dose (1/1000) added to aeration tank by volume has been achieved the highest removal ratios 91.5% and 96.0%for COD and BOD respectively compared to 66.0%

and 74.0% in the control reactor.

The addition of EM dose as daily dose gave high removal ratios on long term compared to pulse addition.

Using EM bacteria in activated sludge system would reproduce many numbers of effective, beneficial activated cells in aeration tank that achieving high removal ratio of organic

materials.

EM enzymes have been appeared a great ability in oxidize of organic materials compared to the bacteria in control reactor.

The application of EM bacteria may be increased the aeration tank capacity by lowering the HRT with maintaining stringent water quality criteria.

The obtained results indicated that old and over loaded plants can be improved by using EM.

EM has the potential to improve the overall effectiveness of the activated sludge process for treatment of domestic sewage.

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

2 4 6 8

HRT(hr)

TS

S r

em

oval r

atio


40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

2 4 6 8

HRT(hr)

CO

D r

em

oval r

atio


40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

2 4 6 8HRT(hr)

BO

D r

em

oval r

atio



78

REFERENCES

[1]. American Public Health Association; American Water Works Association; And Water

Pollution Federation. (2005). Standard Methods for the Examination of Water and Wastewater. 21th Edition.

[2]. Higa, T. (1993). "An Earth Saving Revolution", Sunmark Publishing Tokyo, Japan.

[3]. Higa, T. (1996). "Effective Microorganisms -Their role in Kyusei Nature Farming and sustainable agriculture". In Proceedings of the Third International Conference on Kyusei

Nature Farming. Ed. J.F. Parr et al., USDA, Washington, USA: 20-24.

[4]. Higa, T. and Chinen, N. (1998). "EM Treatments of Odor Waste Water and Environmental Problems", College of Agriculture, University of Ryukyus, Okinawa, Japan.

[5]. Janda, K. (2005). The lipolytic activity of Thermomyces lanuginosus strains isolated from different natural sources. International Biodeterioration and Biodegradation, 55: 149-152.

[6]. Metcalf and Eddy Inc, (2003). "Wastewater Engineering, Treatment and Reuse" McGraw-Hill, New York.

[7]. Monica, S., Karthik, L., Mythili, S. and Sathiavelu, A. (2011). "Formulation of Effective Microbial Consortia and its Application for Sewage Treatment". Microbial Biochem Technol

volume (3): 051-055. doi:10.4172/1948-5948.1000051.

[8]. Namsivayam, S., Narendrakumar, G. and Arvind, K. (2011). " Evaluation of Effective Microorganism (EM) for treatment of domestic sewage" Journal of Experimental Sciences,

ISSN: 2218-1768, Vol. 2, Issue 7, Pages 30-32.

[9]. Taylor, C., Yahner, J., Jones, D. and Dunn, A. (1997)."Wastewater in Pipeline", Ch (8), P4.

[10]. Williams, S.T. and Wellington, E.M.H. (1982). Actinomycetes. In: Page, A. L. (ed), methods of soil analysis. Part 2. Chemical and microbiological properties-Agronomy

monograph no. 9, ASA-SSSA, Madison, USA, pp. 969-987.

[11]. Wollum, A.G. (1982). Cultural methods for soil microorganisms. In: A.L. Page, R.H. Miller and D.R. Keenet, Editors, Methods of Soil Analysis, Part 2, Soil Science Society of America,

Madison, WI, pp. 781801.

Documents

Potential of EM for Conventional Activated Sludge Upgrade