Practical Report JSTP

Waste Water Holding Bhd.

Internship Report

Florian Michael Gehring & Mohd Farhan Ariff

11.02.2011

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Inhalt1. Introduction............................................................................................................3

2. Timetable................................................................................................................4

3. Experimental procedure.........................................................................................6

3.1. Total, Volatile and Fixed Solids.........................................................................6

3.1.1. TS...............................................................................................................6

3.1.2. VS, FS.........................................................................................................6

3.2. Total, Volatile and Fixed Suspended Solids......................................................7

3.2.1. TSS.............................................................................................................7

3.2.2. VSS, FSS......................................................................................................7

3.3. Sludge Volume Index........................................................................................7

3.4. Chemical Oxygen Demand (Preparation of the Stock Solution).......................8

3.5. Alkalinity (Preparation of the Stock Solution)..................................................8

3.6. pH.....................................................................................................................9

3.7. Moisture...........................................................................................................9

4. Results and Discussion..........................................................................................10

4.1. Total, Volatile and Fixed Solids.......................................................................10

4.2. Total, Volatile and Fixed Suspended Solids....................................................11

4.3. Sludge Volume Index......................................................................................11

4.4. Chemical Oxygen Demand..............................................................................12

4.5. Alkalinity.........................................................................................................13

4.6. pH...................................................................................................................15

4.7. Moisture.........................................................................................................16

5. Summary...............................................................................................................16

6. Problems...............................................................................................................17

6.1. Temperature...............................................................................................17

6.2. Oxygen........................................................................................................17

6.3. pH................................................................................................................17

6.4. Retention Time............................................................................................17

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7. Proposal for solution.............................................................................................18

7.1. Tracer..........................................................................................................18

7.2. Is the sludge in the anaerobic digester hermetically sealed?......................18

7.3. Digester is overfilled...................................................................................18

7.4. Sludge is to inconstant................................................................................18

7.5. Problems with the temperature.................................................................18

8. References............................................................................................................18

JSTP

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1. IntroductionThe Jelutong Sewage Treatment Plant is one ofthe biggest waste water treatment plants, based on the SBR technology, all over the world. It was constructed on the reclaimed land (14.7 hectars) and designed to treat 1.2 million Population Equivalent (PE). The maximum capacity is 270 m³/day. The JSTP would be required to generate an effluent quality less than 20 mg/L BOD, 50 mg/L TSS and 10 mg/L of total ammonium nitrogen plus nitrate nitrogen with a limit of 5 mg/L ammonia nitrogen. The plant can reduce phosphorous in the biological step in the future.

Figure 1: Location of Jelutong Sewage Treatment Plant (JSTP)

The JSTP consists of the inlet works, preliminary treatment, biological treatment, prethickening tank, sludge holding tank, sludge thickening process, sludge digester, sludge dewatering process and sludge disposal.

There are two anaerobic sludge digesters on the JSTP and only one is in operating state. The other digester has not been used. The gas which arises in the digester is used to generate electricity in a generator. The anaerobic digesteris equipped with heating and mixing facilities which use the electricity from the generator.

The mixing in the anaerobic digester is performed with compressed biogas. They used a heat exchanger to get a constant temperature in the digester. The temperature depends between 30°C and 38°C.

One problem of the plant is the bad biogas quality. Due the bad methane rate I picked up 7 sludge samples from different places of the JSTP and analyzed it in the laboratory at the UniversitiSains of Malaysia. With my results and my knowledge I want to find a solution for this problem.

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2. TimetableIn cooperation with Dr. Suffian and Mr. Farhan I created a timetable for my work.

The first step was the orientation. In this step I read a lot of books and visited many websites with information about the anaerobic digestion and there microorganism. The books, which I have read, are listed in table 1.

Table1: List of books

Titel ISBN-10Anaerobic Sludge Digestion 0-943-24413-7The Microbiology of Anaerobic Digesters 0-471-20693-8Wastewater Sludge Processing 0-471-70054-1Sludge Management and Disposal 0-135-01248-1Recycling and Reuse of Sewage Sludge 0-727-72992-6Methods of Characterization of Sewage Sludge 9-027-71782-6Taschenatlas der Umweltchemie 3-131-03111-5

After thisstep I discussed with Farhan and Dr. Suffian, which places are the best to pick up our samples and which measurements we have to do. We defined 7 places (figure 1, grease removal, biological treatment (sequencing batch reactors tank), sludge thickening, sludge digester (influent and effluent), sludge dewatering process and also disposal of sludge) and our measurements (TS, VS, FS, TSS, TVS, TFS, COD, Alkalinity, Moisture, pH, and SVI). All samples were stored in refrigerator at UniversitiSainsMalaysia civil engineering lab.

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4

6

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Figure 2: Sewage treatment flow diagram and sample points

The second step was to pick up the sludge and analyze it in the laboratory.

The last step was to discuss the results and make some improvement proposals.

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3. Experimental procedure

3.1. Total, Volatile and Fixed Solids

3.1.1. TSI. Prepare two evaporating dishes by cleaning and ignition at 500°C

for 1 hour in a muffle furnace.II. Cool, desiccate, weigh, and store dish in desiccator until ready

for use.III. Transfer sample to prepared dish, weigh (weight of wet sample

plus dish) and evaporate to dryness on a steam bath or in a drying oven. Choose a sample volume that will yield a residue between 2.5 and 200 mg. If necessary, add successive sample portions to the same dish. When evaporating in a drying oven, lower temperature to approximately 98°C to prevent splattering.

IV. Dry evaporated sample for at least one hour at 103 to 105°C.V. Cool dish in a desiccator to balance temperature and weight

(weight of dry solids).VI. Repeat cycle of drying at 103 to 105°C, cooling, desiccating, and

weighing until a constant weight is obtained, or until weight less than 4% of previous weight.

VII. Calculate: Total Solids , as%by weight= A−CB−C

∗100

A=weight of dried resid ue plus dish [mg ]B=weight of wet residue plus dish [mg ]

C=weight of dish [mg ]

3.1.2. VS, FSI. After total solids have been performed, ignite sample and dish

for 20 minutes at 500°C in muffle furnace. (Perform analysis in triplicate)

II. Let dish cool partially in desiccator with cover off until most of the gas has dissipated (approx. 2 minutes). Close desiccator to complete cooling.

III. Weigh cool dish.

IV. Calculate: Volatile Solids ,as%Total Solids= A−BA−C

∗100

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¿ Solids , as%Total Solids= B−CA−C

∗100

A=weight of residue plus dishbefore burning [mg ]B=weight o f residue plus dish after burning [mg ]

C=weight of dish [mg ]

3.2. Total, Volatile and Fixed Suspended Solids

3.2.1. TSSI. Seat prepared glass-fibre filters in filter manifold with distilled

water.II. Select sample size that will yield between 10 and 200 mg residue.

Keep sample mixed.III. Filter sample to dryness. If pipetting small volumes pipette into

approximately 10 mL of distilled water to ensure sample is well distributed over filter. Do not use 10 mL of distilled water if saving the filtrate if saving the filtrate for analysis of Total Dissolved Solids.

IV. Transfer filter back to its original planchet with forceps and dry filter plus planchet for 1 hour at 103°C.

V. Cool in desiccator and weigh (dry weight of solids plus filter and planchet).

VI. Calculate: TSS , [mgL ]= (A−B )∗1000sample volume [mL ]

A=dry weight of solids plus filter∧planchet [mg ]B=weight of filter plus planchet

3.2.2. VSS, FSSI. After determination of total suspended solids, ignite filter plus

planchet at 500°C for 20 minutes.II. Cool in desiccator and weigh (weight of burned solids plus filter

and planchet).

III. Calculate: VSS ,[mgL ]= (A−B )∗1000sample volume [mL ]

FSS ,[mgL ]= (B−C )∗1000sample volume [mL ]

A=weight of solids plus filter∧¿planchet beforeburning [mg ]

B=weight of solids plus filter∧¿planchet after burning [mg ]

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C=weight of filter plus placnchet [mg ]

3.3. Sludge Volume IndexIV. Take a sample of mixed liquor and determine its SS

concentration (MLSS)V. Add sample of mixed liquor into a measuring cylinder of 1000 mL

capacity.VI. Allow the sludge to settle for 30 minutes.

VII. The volume of settled sludge is read from the markings on the cylinder.

VIII. Calculate SVI ,[mgL ]=V∗1000MLSS

V=volume of settled sludge ,[mLL

]

MLSS=mixed liquor ,[mgL

]

3.4. Chemical Oxygen Demand (Preparation of the Stock Solution)I. Potassium dicromate + mercuric sulphate solution (for 1 liter).

Weight 10.216 gm potassium dichromate and heat it in oven until 2 hours. Then add 500 mL distilled water plus 10.216 gm potassium dichromate (heated) plus 167 mL H2SO4 with concentration 98% pure plus 33.3 gm mercury sulphate.

II. Silver sulphate solution (Acid Reagent ) (for 1 liter)One liter H2SO4 with concentration 98% pure plus 10.12 gm Ag SO4

3.5. Alkalinity(Preparation of the Stock Solution)I. N/50 H2SO4

N = Take 7 mL from H2SO4 with concentration 98% then dilute with distilled water until 250 mL. In order to become N/50, take 20 mL from 250 mL from N, then dilute with distilled water until 1 liter.

II. 2. Methyl orange indicator ( C14H14N3NaO3S)0.05gm methyl orange indicator were dilute in 100 mL distilled water.

III. Phenolphthalein Indicator0.08gm phenolphthalein indicator were dilute with 100 mL methanol (CH3OH)

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IV. To calculate the results of the total alkalinity use this formular.

Total alkalinity (M) = mL H2SO4 (to pH 4.50) x 1000

mL sample

3.6. pHI. The pH meter is calibrated with buffer solutions (pH 4.01 and

7.01). II. The electrode is rinsed with with distilled water and dried with a

piece of tissue paper. III. The pH values of the samples (50 mL) are determined by

immersing the pH meter electrode into them.(Note: The electrode is rinsed with distilled water and dried with tissue paper before measuring each sample’s pH.)

IV. The results are compared with are compared with those obtained with pH paper.

V. Results are recorded.

3.7. MoistureTen milliliter of the sewage sludge sample and the empty clean beaker were weighed with the analytical balance separately. The sample then added into beaker, and oven-dried at temperature 105°C for 24 hours. After that it cooled in the desiccator for balance the temperature. Beaker was weighed after oven-dried and recorded the reading of the weight.

MoistureContent= A−BA

∗100

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4. ResultsandDiscussionIf we picked up the first samples for ouranalysis, the SBR was on.So it was possible to pick up all our samples. At the second time the SBR was off, so it wasn’t possible to pick up sample number 4. We have also a huge difference between some values from the first to the second analysis. Perhaps it is possible, that when the SBR is off, the sludge has different content and that’s the reason, why the values have a so huge difference.

4.1. Total, Volatile and Fixed SolidsThe table 2 shows the results of the TS, VS, and FS measurements.

Table 2: Results of the Total, Volatile and Fixed Solids

Sample15thDecember 2010 17thJanuary 2011

TS [%] VS [%] FS [%] TS [%] VS [%] FS [%]1 0,0575 73,7864 26,2136 0,0700 58,4615 41,53852 0,1050 55,7471 44,2529 0,1398 52,1073 47,89273 2,8333 76,4889 23,5111 2,8570 73,9840 26,01604 0,0711 63,4146 36,5854 - - -5 2,7102 73,5615 26,4385 3,3578 69,7194 30,28066 3,0468 74,5714 25,4286 3,6740 72,7448 27,25527 5,7051 74,8495 25,1505 4,3778 94,2193 5,7807

During the digestion process, volatile solids are degraded to a certain extent and converted into biogas. The sludge volume is hereby reduced and the supernatant is returned to the plant. The degree of stabilization is often expressed as the percent reduction in volatile solids, itself associated with either the SRT or the detention time based on the untreated sludge feed.The following empirical equation allows the estimation of the amount of volatile solids destroyed.

Vd=13,7∗ln (SRTdes )+18.9

Vd=Volatile Solidsdestruction [% ]SRTdes=the time of digestion

In the anaerobic sludge digester of the JSTP we have a retention time of 15 days, so the volatile solids destruction is 56%. In my measurements the volatile solids after the digestion has an average value of 73,6581%. Before the digestion the value is lower than after. This means, that the volatile solids increase in the digester. The

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microorganisms produce normally gas in the digestion process, so the volatile solids decrease.

4.2. Total, Volatile and Fixed Suspended SolidsThe results of the TSS, VSS, and FSS measurements are in table 3.

Table 3: Results of the Total, Volatile and Fixed Suspended Solids


TSS [mg/L]

VSS [mg/L]

FSS [mg/L]

TSS [mg/L]

VSS [mg/L]

FSS [mg/L]

1 152,00 112,00 40,00 194,00 188,00 6,002 114,00 78,00 36,00 1058,00 870,00 188,003 23126,00 17132,00 5994,00 24622,00 18282,00 6340,004 1476,00 1072,00 404,00 - - -5 25780,00 15456,00 10324,00 29696,00 23036,00 6660,006 27190,00 19774,00 7416,00 56926,00 47814,00 9112,007 337873,00 297380,00 40493,00 6426,00 4569,00 1857,00

4.3. Sludge Volume IndexThe table 4 shows the results of the sludge volume index measurements.

Table 4: Results of the SVI


MLSS [mg/L] SVI [mL/g] MLSS [mg/L] SVI [mL/g]1 40,00 130,00 6,00 166,702 36,00 55,56 188,00 531,913 5994,00 166,50 6340,00 149,844 404,00 445,54 - - 5 10324,00 96,86 6666,00 150,156 7416,00 134,89 9112,00 109,747 40493,00 4,89 1857,00 21,54

The results are also very inconstant. You can see a huge fluctuation between all the sample points. For example sample 2, at the 15th December the sludge volume index was 55,56 mL/g and at the 17th January the sludge volume index was 531,91 mL/g

.

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4.4. Chemical Oxygen DemandThe results of the Chemical Oxygen Demand measurement are in table 5.

Table 5: Results of the COD measurement

Sample dilutionratio 15thDecember 2010 17thJanuary 2011COD [mg/L] COD [mg/L]

1 1:5 340 1522 1:120 161 3303 1:10 23250 277204 1:120 1045 -5 1:120 19800 168006 1:10 21240 267607 1:120 1154 1490

The COD Values increase with the time in the plant. Normally they should increase till the digester and after the digestion process they should decrease. But in our measurements, the values increase till after the digester and on the disposal they decrease. That’s not normal and something is going wrong in the digester.

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4.5. AlkalinityThe results of the total alkalinity from the 15th December 2010 are in table 6.

Table 6: Results of the alkalinity measurements from the 15th December 2010

SampleSample Volume

[mL]

Burette readingType of

alkalinityTotal

alkalinityStart [± 0.05 mL]

End[± 0.05 mL]

Volume of N/50 H2SO4

[mL]

1 500 9,7 9,7

Methyl-orange 185,40 8,8 8,8

Average 9,27

2 509,7 14 4,3


Average 3,55

3 5014 19 5


Average 4,1

4 5019 21,3 2,3

Methyl-orange 4514,8 17 2,2

Average 2,25

5 5021,3 24,2 2,9

Methyl-orange 5317 19,4 2,4

Average 2,65

6 5024,2 26,8 2,6


Average 2,45

7 5026,8 31,6 4,8


Average 4,35

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The table 7 shows the values of the Alkanility measurement from the 17 th January 2011

Table 7: Results of the Alkalinity measurements from the 17th January 2011

SampleSample

Volume (mL)

Burette readingType of alkalinit

y

Total alkalinity

Start [± 0.05

mL]

End[± 0.05

mL]

Volume of N/50 H2SO4

[mL]

1 500 9,3 9,3

Methyl orange 1880 9,5 9,5

Average 9,4

2 509,3 16,8 7,5

Methyl orange 6909,5 15,8 6,3

Average 6,9

3 5016,8 18,6 1,8

Methyl orange 420015,8 17,5 1,7

Average 1,75

4 NilNil Nil Nil

Methyl orange NilNil Nil Nil

Average Nil

5 5018,6 21,6 3

Methyl orange 624017,5 19,7 2,2

Average 2,6

6 5021,6 23,1 1,5

Methyl orange 384019,7 21,4 1,7

Average 1,6

7 5023,1 26,5 3,4

Methyl orange 76021,4 25,6 4,2

Average 3,8

Between the sample points there is sometimes a higher fluctuation than 500%. The

results from the first measurements have each time a lower value than the results

from the second measurements. At the first and second sampling we collected the

same sludge, but measured each time different values. Very important for the

digestion is the ratio of volatile acids/alkalinity after the anaerobic digestion. This

ratio should amount less than 0.8. In the measurements from the 15th December, the

total alkalinity is very low and between the digester influent and effluent the

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difference of the total alkalinity is not high enough. In the second series of

measurements the values are much better. Here we have a higher difference

between the influent and effluent.

4.6. pHThe results of the pH measurements are in the table 8.

Table 8: Results of the pH measurement

SamplepH

15th December 2010 17thJanuary 20111 7,54 8,022 7,08 8,373 7,88 8,134 7,22 - 5 7,53 8,086 7,32 7,947 8,05 8,17

The pH values are very high. Normally the pH of sludge before and after the digester depends between 6,5 and 7,5. In the second sampling the pH values are higher than in the first sampling. And each value from the second sampling is higher than 7.5. This has a negative influent of the microorganisms.

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4.7. MoistureTable 9: Results of the Moisture measurement


MLSS [mg/L] SVI [mL/g] MLSS [mg/L] SVI [mL/g]1 40,00 130,00 6,00 166,702 36,00 55,56 188,00 531,913 5994,00 166,50 6340,00 149,844 404,00 445,54 - -5 10324,00 96,86 6666,00 150,156 7416,00 134,89 9112,00 109,747 40493,00 4,89 1857,00 21,54

The values of the moisture content have also a huge difference. For example sample 2 130 mL/mg at 15th December and 532 mL/mg at the 17th January. Maybe the set off of the SBR has a direct influence of sample 2.

5. SummaryOn the basis of the results of my measurements we can see that the sludge is very inconstant. This imbalance has an influence on the anaerobic digestion and therefore also of the gas production. The microorganisms need a constant sludge consistence, a constant temperature and also a constant pH.

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6. ProblemsThe JSTP anaerobic digester produces a bad gas rate. The biogas consistence is normally 55-70% of methane, 30-45% carbon dioxide and a less of sulfur compounds. But in the anaerobic digester the gas consists of 30-40% methane, 25-30% carbon dioxide, 4-10% oxygen and 1% sulfur compounds. The other 20-25% was indefinable.

6.1. TemperatureThe temperature should not depend more than 2°C. At the first time when I visited the plant, the temperature in the digester was 30°C, at the second time it was 36°C and at the third time it was 30 °C again. So the temperature difference is too high for the microorganisms. If this temperature difference to high, the microorganism died.

6.2. OxygenAnother problem is the oxygen in the anaerobic digester, because the oxygen is toxic for the anaerobic microorganisms. I’m not sure if the digester is thick or if the mixing facilities pump oxygen in the tank.

6.3. pHIn my measurements I assert that the pH is very high. The values liebetween 7.5 and 8.5. Normally the sludge has the same pH in the influent and effluent of a continuous, anaerobic sludge digester. These values were also different.

6.4. Retention TimeIn an anaerobic sludge digester the retention time amounts between 15 and 25 days. Mr. Azman told me, that the retention time in the JSTP digester is 15 days. I’m not sure if that is right, because at the effluent the volatile acid /alkalinity ratio is very high. That means that the microorganisms have not enough time to destroy the volatile acids.

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7. Proposalforsolution

7.1. TracerTo determine the real retention time of the sludge in the digester, you can use the tracer method. You inject a tracer in the digester and wait so long, till the tracer is coming out. After that you have the exact retention time of the sludge. So you can see,if the sludge is long enough in the digester.

7.2. Is the sludge in the anaerobic digester hermeticallysealed?There are some solutions in the internet to check the density of the digester. You have to discharge the digester and then you can check, if the digester is thick.

7.3. Digester is overfilledIt should be possible that the anaerobic digester is to full. That could be also a reason for the bad gas rate. In this case, you can use your second digester, to get a better methane gas rate.

7.4. Sludge is to inconstantIn this case, you have to check discharger. Maybe there are industrial companies which discharge intermittent high loaded wastewater into the drain.

7.5. Problems with the temperatureThere are many hints to solute the problems with the temperature. Reasonable is it, to make a new isolation around the digester. The isolation stabilized the temperature. Now it is also easier to control the temperature.

8. References The books in table 1. www.iwk.com.my www.wikipedia.de www.google.de www.ecosia.de

http://www.ecosia.de/

http://www.google.de/

http://www.wikipedia.de/

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