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ISSN 2249-0582 World J of Engineering and Pure and Applied Sci. 2012;2(2(2(2(5555):):):):161161161161

Anyakora Anyakora Anyakora Anyakora et alet alet alet al. Strategy For Processing Water Works Sludge

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OriginalOriginalOriginalOriginal Article

Applied Science

Sustainable Technology-Based Strategy for Processing Water Works Sludge for

Resource Utilization

Nkolika V ANYAKORA 1, Collin S AJINOMOH 1, Abdulkarin S AHMED 1,

Ibrahim A MOHAMMED-DABO 1, Jibrin IBRAHIM 2, Jiniya B ANTO 2

ABSTRACT [ENGLISH/ABSTRACT [ENGLISH/ABSTRACT [ENGLISH/ABSTRACT [ENGLISH/ANGLAISANGLAISANGLAISANGLAIS]]]] Affiliations:

1 Department of Chemical Engineering, Ahmadu Bello University, Zaria, NIGERIA

2 Federal Capital Territory Water Board, Abuja, NIGERIA

Address for Correspondence/ Adresse pour la Correspondance: [email protected]

Accepted/Accepté: September, 2012

Citation: Anyakora NV, Ajinomoh CS, Ahmed AS, Mohammed-Dabo IA, Ibrahim J, Anto JB. Sustainable Technology-Based Strategy for Processing Water Works Sludge for Resource Utilization. World Journal of Engineering and Pure and Applied Science 2012;2(5):161-8.

Water Works Sludge collected from a water treatment plant was processed and characterised for resource utilisation

potentials. The processing steps considered were gravity thickening and air drying incorporating mechanical agitation.

Scanning electron microscope (SEM), X-ray florescence (XRF) and X-ray diffraction (XRD) were used to characterize the

sample. Experimental results showed that the combined effects of temperature, relative humidity, wind speed, sun intensity

affect the drying rate of sludge. Additionally, it was observed that the incorporation of mechanical agitation cushioned the

effect of sludge depth while improving the performance of drying bed, which caused the achievement of higher solid content

of 80% using drying bed when compared to the value from other dewatering processes. The result of the chemical analysis

of the sludge by XRF showed a composition of 28.28% Al2O3 and 30.30% SiO2 with the major crystalline phases of kaolinite

and quartz. The microscopy showed that the sludge comprised of flake-like Kaolinite agglomerate and particles which fall

into the Kaolinite clay classification. In terms of practical interest, sludge can be used as a secondary raw material and for

adoption as viable alternative in material application and utilization in engineering design. It is noted that developing

operational systems appropriate to local conditions while assuring long-term services and sustainable treatment processes

is required for sustainable development in wealth creation and environmental protection.

Keywords: Sludge, characterization, sustainable, utilization, agitation, dewatering

RÉSUMÉ RÉSUMÉ RÉSUMÉ RÉSUMÉ [[[[FRANÇAISFRANÇAISFRANÇAISFRANÇAIS/FRENCH]/FRENCH]/FRENCH]/FRENCH]

Water Works boues prélevé dans une installation de traitement des eaux ont été traitées et caractérisé pour les potentiels

d'utilisation des ressources. Les étapes de traitement ont été considérés épaississement par gravité et séchage à l'air

intégrant une agitation mécanique. Microscope électronique à balayage (MEB), X-ray fluorescence X (XRF) et diffraction des

rayons X (XRD) ont été utilisés pour caractériser l'échantillon. Les résultats expérimentaux ont montré que les effets

combinés de la température, l'humidité relative, vitesse du vent, l'intensité du soleil affectent la vitesse de séchage des

boues. En outre, il a été observé que l'incorporation d'une agitation mécanique amorti l'effet de la profondeur des boues tout

en améliorant les performances de séchage lit, ce qui a causé la réalisation d'un contenu solide élevé de 80% avec lit de

séchage par rapport à la valeur du processus de déshydratation autres. Le résultat de l'analyse chimique des boues par XRF a

montré une composition de 28,28% Al2O3 et SiO2 30,30% avec les grandes phases cristallines de la kaolinite et de quartz.

La microscopie a montré que la boue constituée de flocons comme agglomérat de particules de kaolinite et qui tombent dans

la classification argile kaolinite. En termes d'intérêt pratique, les boues peuvent être utilisés en tant que matière première

secondaire et à l'adoption comme une alternative viable à l'épandage de matières et l'utilisation dans la conception

technique. Il est à noter que le développement de systèmes opérationnels adaptés aux conditions locales tout en assurant à

long terme des services et des procédés de traitement durable est nécessaire pour le développement durable dans la

création de richesse et de protection de l'environnement.

Mots-clés: Boues, la caractérisation, durable, de l'utilisation, de l'agitation, de déshydratation

INTRODUCTINTRODUCTINTRODUCTINTRODUCTIONIONIONION The increasing deterioration of world environments

caused by the extensive exploration of resources of virgin

materials and encouragement in the use of cheaper and

abundantly available waste materials has given rise to

the exploration of viable alternatives in material

application in engineering design. Particularly attractive

is the water works sludge which is a sustainable resource

as long as the production of potable water remains a

sustainable basic amenity.

World J of Engineering and Pure and Applied Sci. 2012;2(2(2(2(5555):):):):162162162162 ISSN 2249-0582


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Of interest is the increase in demand of potable water in

developing countries, which results in the fast increase in

sludge production and the resulting environmental

effects. At the Lower Usuma Dam Water Treatment Plant

(LUDWTP), Abuja, Nigeria for example, the large

quantities of sludge generated can be processed for

resource utilisation using any of the different treatment

processes that are flexible to local conditions, while

satisfying the regulatory and economic constraints.

Research findings show that water works sludge contains

mostly water and small amount of solids consisting of

different kinds of oxides, such as silicon oxide, calcium

oxide, iron oxide, and aluminium oxide, as well as rich

amounts of clay materials[1] which may be used for the

preparation of adsorbents and catalysts, including as soil

substitute for land application, and clay substitute in

brick making [2,3]. Other findings indicate that, utilizing

about 5% of water works sludge as alternative raw

material substitute in making bricks would create a

market for over 400,000 Tonnes of waste [4].

Additionally, the retrieval and reuse of oxides from

sludge and other applications is a direct way of treating

sludge waste and indirectly reducing the demand for

natural resources.

Although, handling of sludge is one of the most

significant challenges in water works management due

to its high treatment costs and the risks to environment

and human health, the adoption of dewatering

processing method could be more easily and

economically handled if the volume were reduced by

removing the water before subsequent processing and

transporting to its final disposal route. This can be

achieved by the use of drying beds, drainage and

evaporation to achieve a desired result at a minimal cost,

as proven to increase the operational and initial

investment costs [5].

Other activities intended for use in achieving the

objective of this work therefore, is to adopt the use of

comprehensive analytical method of analysis which can

accurately determine the microstructural and chemical

characteristics of Water Works sludge from the

LUDWTP, using scanning electron microscope (SEM), X-

ray florescence (XRF), and X-ray diffraction (XRD). Thus,

the need for strategies to promote sustainable

technology- based and production driven economy,

which is an unprecedented effort to jump-start the

economy, create and save millions of jobs, and address

long-neglected challenges while solving the

environmental problems posed by the indiscriminate

disposal of sludge is expedient.

MATERIALS AND METHODSMATERIALS AND METHODSMATERIALS AND METHODSMATERIALS AND METHODS Processing of Sludge

Sludge sample was collected from the desludging

chamber of the clarifier of the LUDWTP and

subsequently dewatered using gravitational thickening

method. The dewatered sludge was dried on a concrete

floor in an open of a weather monitoring station.

Meteorological data from weather station was

incorporated in the experiment at hourly intervals to

determine the drying kinetics parameter, as shown in

figures 1 to 6.

The initial and final moisture and solid contents were

measured to determine the effectiveness of natural

drying method in Abuja, Nigeria. To accelerate the

drying process, the solid was stirred at intervals

(mechanical agitation) to increase their exposure to sun

and air. The dried sludge was milled and passed through

a 200 mesh sieve for analysis.

Figure 1: Figure 1: Figure 1: Figure 1: This figure shows the desludging chamber

Figure 2:Figure 2:Figure 2:Figure 2: This figure shows the gravity thickening

facility

Characterization of Sludge

Determination of Chemical Composition (X-Ray

Fluorescence – XRF) Analysis

Chemical composition of the dry sludge sample was

determined using PW 4030 P-Analytical X-ray

fluorescence (XRF) machine. The sample was weighed

and ground in an agate mortar before subsequent


AnyakoraAnyakoraAnyakoraAnyakora et alet alet alet al. Strategy For Processing Water Works Sludge



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addition of PVC dissolved in Toluene (binding agent)

The product was carefully mixed and pressed in a

hydraulic press into a pellet. The pellet was loaded to the

spectrometer and voltage (30KV maximum) and a

current (1mA maximum) was applied to produce the X-

rays to excite the sample for a preset time of 10 minutes.

The spectrum from the sample was analysed to

determine the concentration of the element in the sample.

The system was controlled by a PC running the

dedicated mini pal analytical software.

Determination of Mineralogical Composition of Sludge

(X-Ray Diffractometer-XRD) Analysis

PW3050/60-XPERT-PRO MPD type X-ray diffractometer

(XRD) was used to study phase analysis under K α ray of

Cu from 30 to 750 2ϴ pipe pressure 40 KV, pipe flow 30

Ma, with a scanning step of 0.060 at scanning speed

4°/min. The diffraction data were detected by automated

detector X Celarator. The samples were then analysed to

determine the mineralogical components.

Determination of Microstructure of Sludge

The sludge samples were quantitatively analyzed using

EVO/MA 10 Scanning Electron Microscope (SEM).The

test pieces; measuring approximately 15 x 15mm2 were

mounted on sample holder already prepared with

conductive (carbon) adhesive tapes to hold samples. The

sample holder, with the held sample specimens was

subsequently loaded into the SEM specimen chamber,

and operated on variable pressure mode, with the

vacuum created to the level needed to propagate electron

beam. As the indicator showed ‘Blue’, the microscope

was subsequently directed on each of the samples for

magnification. Each sample was magnified and viewed

at separately, thus the morphology and structure of

sample is detected.

RESULTSRESULTSRESULTSRESULTS Combined Effects of Drying Parameters on Drying Rate

Result of drying experiment (field trial) is shown in Table

1.

Table 1: Table 1: Table 1: Table 1: This table shows result of field-trial experiment

Month Temp

(0C)

Relative

Humidity

(%)

Wind

Speed

(m/s)

Evaporation

(mm)

Sun Intensity

W/m2

Initial

Solid

Content

(%)

Initial

Moisture

Content

(%)

Final Solid

Content

(%)

Final

Moisture

Content

(%)

Drying

Time

(h)

Aug 19-22, 2011 25.5 88 3.0 2.2 447 5.03 94.97 80.01 19.99 77

Sept 17-29, 2011 25.5 85 4.0 2.2 785 5.43 95.57 79.69 20.31 50

Oct 29-30, 2011 24.0 86 3.7 3.3 948 4.83 95.17 79.5 20.05 49

Nov 12-14, 2011 25.9 70 3.7 5.1 901 5.04 94.96 80.13 19.87 45

Dec 14-15, 2011 24.6 39 2.4 9.2 809 4.68 95.32 80.46 19.54 24

Jan 16, 2012 24.2 25 2.7 10.4 892 4.99 95.00 80.79 19.21 18

Feb 5, 2012 30.6 34 3.6 9.4 903 5.01 94.99 80.13 19.87 22

Mar 7-8, 2012 30.2 43 2.4 9.1 960 4.78 95.222 80.00 20.00 31

Apr 4-5, 2012 30.1 57 2.2 4.9 729 4.97 95.03 79.98 20.02 43

Figure 3: Figure 3: Figure 3: Figure 3: This figure shows sample of dried sludge on

the drying bed

Figure 4: Figure 4: Figure 4: Figure 4: This figure shows sample of liquid (raw)

sludge



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Figure 5: Figure 5: Figure 5: Figure 5: This figure shows sample of dewatered

sludge

Figure 6: Figure 6: Figure 6: Figure 6: This figure shows sample of dried sludge

Effect of Sludge Depth with Time

Result of changes in drying rate with time on sludge

depth is shown in figure 7.

Figure 7: Figure 7: Figure 7: Figure 7: This figure shows changes in drying rate with

time on sludge depth in 3D.

Performance Evaluation Table 2 shows the effect of mechanical agitation on

(stirring) on drying rate and time.

Characterization of Sludge

Due to the complex nature of sludge, there is need for

proper characterization to comprehensively analyze and

determine its main composition. This is very necessary to

determine sludge resource utilisation potentials. The

chemical composition of sludge from LUDWTP is shown

in Table 5.

Figure 8: Figure 8: Figure 8: Figure 8: This figure shows normal drying

Figure Figure Figure Figure 9999: : : : This figure shows aided (stirred) drying

Figure 10: Figure 10: Figure 10: Figure 10: This figure shows changes in drying rate with

time for natural drying showing the effect of stirring on

drying rate





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Table 2: Table 2: Table 2: Table 2: This table shows result of the effect of mechanical agitation (stirring) on drying rate and time

Time Weight 1(g) Weight 2(stirred)(g) Time(h) Rate 1(kgm-2h-1) Rate 2(Stirred)(kgm-2h-1)

7am 83.4 88.4 0 0 0

9am 78.9 83.8 2 0.001724138 0.001762452

10am 76.7 81.4 3 0.001685824 0.00183908

11am 69.8 74.2 4 0.005287356 0.005517241

12noon 61.1 65.1 5 0.006666667 0.00697318

1pm 53 56.1 6 0.006206897 0.006896552

2pm 46.7 49 7 0.004827586 0.005440613

3pm 41.8 41.5 8 0.003754789 0.005747126

4pm 41.5 39.1 9 0.000229885 0.00183908

Table Table Table Table 3333: : : : This table shows comparison of results of LUDWTP, Abuja dried sludge with some clay samples in Nigeria

Clay Location(State) Al2O3( % ) SiO3( % ) Fe2O3( % ) CaO+MgO( % ) Loss on ignition

Oshielle * Abeokuta (OG) 28.30 53.40 1.35 0.88 15

Ozubulu * Nnewi (AN) 19.31 58.30 1.55 1.25 14.16

Enugu * Enugu (EN) 22.71 55.00 2.42 1.95 16.35

Nsu * Okigwe (IM) 30.22 50.60 1.92 1.08 10.54

Okpekpe * Auchi (ED) 24.30 53.20 1.45 1.30 16.86

Kankara * Kankara (KT) 38.64 44.50 NIL 1.30 16.70

Giro * Giro(SO) 38.72 41.26 2.10 1.48 14.00

Warram * Warram (PL) 37.13 43.54 1.15 0.58 14.20

Sabon Gida * Jos (PL) 26.88 25.32 13.10 3.20 18.36

Alkaleri * Bauchi(BA) 25.43 54.30 1.05 1.00 15.73

LUDWTP sludge Abuja 28.28 30.8 9.17 1.88 20.78

* Source: [6]

Table 4:Table 4:Table 4:Table 4: This table shows comparison of result of drying bed with other dewatering methods

S/N Process Solid Concentration (%)

1. Gravity Thickening * 3 - 4 2. Scroll Centrifuge * 20 - 30

3. Belt Filter Press * 20 - 25

4. Vacuum Filter * 25 - 35

5. Pressure Filter * 35 - 45

6. Diaphragm Filter Press* 30 - 40

7. Sand Drying Bed * 20 - 25

8. Storage Lagoons * 7 - 15

9. Natural Drying Bed(Abuja) 80 *Source: [7]

Table 5: Table 5: Table 5: Table 5: This table shows chemical composition of LUDWTP sludge.

ComponentComponentComponentComponent Al203 SiO2 K2CaO TiO2 MnO Fe2O3 MgO Na2O Loss on Ignition

Composition (%) 28.28 30.8 0.90 1.55 0.89 3.11 9.17 0.33 0.41 20.78

DISCUSSIONDISCUSSIONDISCUSSIONDISCUSSION Combined Effects of Drying Parameters on Drying Rate

From Table 1, it is noted, as expected, that the reduction

in drying time during the dry season months was higher

than in the raining season months, thus Abuja natural

environment favours drying of water works sludge with

an average solid content of 80%.





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Figure 11Figure 11Figure 11Figure 11: : : : This figure shows the XRD pattern of LUDWTP sludge

Figure 1Figure 1Figure 1Figure 12222: : : : This figure shows the scanning electron

micrograph of LUDWTP sludge (5000X).

Effect of Sludge Depth with Time

From the result in Figure 7, it is noted that the higher the

sludge depth the longer the drying time, thus,

incorporating mechanical agitation increased their

exposure to sun and air as shown in Figure 8 , which

further increased the drying rate with attendant

reduction in the drying time as compared to normal

drying process shown in Figure 9.

Effect of Mechanical Agitation on Drying Rate and

Time

As can be observed from Figure 10, during the constant

rate drying period, free water was not available at the

drying surface, which was due to the internal transport

limitations of water. The observed cracks seem to have

contributed to the longer time.

The Chemical Composition of LUDWTP Sludge

Sample (XRF)

As shown from the XRF result in Table 5, there is

evidence of high silica and alumina contents, whose

oxide total content exceeds 58% by weight. The high

content of alumina in the LUDWTP sludge was noted to

be due to the presence of aluminum hydroxide (Alum)

used as the coagulant, including the iron oxide which

gave a distinct rust hue. This property is often desired in

the colouration of brick products [4].

Performance Evaluation

From Table 2, it is observed that the evaluation

performance of sludge proved a high solid content of

80% inferring that dewatering method of use of drying

bed is better suited.


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The Chemical Composition of LUDWTP Sludge

Sample (XRF)

As shown from the XRF result in Table 5, there is

evidence of high silica and alumina contents, whose

oxide total content exceeds 58% by weight. The high

content of alumina in the LUDWTP sludge was noted to

be due to the presence of aluminum hydroxide (Alum)

used as the coagulant, including the iron oxide which

gave a distinct rust hue. This property is often desired in

the colouration of brick products [4].

The XRD Pattern of the LUDWTP Sludge Sample

From Figure 11, it is evident that the crystalline nature of

sludge is as not high as can be seen by the background

bulge which is bigger and the relatively low intensity of

diffraction peak in whole. The sample sludge is noted as

an amorphous material whose composition is of both

organic and inorganic origin. Additionally, the result

showed the presence of some minerals like Kaolinite,

Quartz, and Iron Oxide as identified by their prominent

peaks [8]. This is in line with the characterization result

in Table 5, thus showing that the sludge is of Kaolinite

clay.

The Scanning Electron Micrograph of LUDWTP Sludge

From Figure 12, it is shown that the LUDWTP sludge has

irregular shape and contained lots of pores on the

surface. This structure is suspected to have been formed

by the coagulants which is related to its strong

adsorption capacity for organic and heavy metal

pollutants in the raw water. The SEM image revealed

that the microstructure of sludge comprised of flakes of

fine kaolinite clay particles [9].

From the XRD, SEM, and XRF analysis, it is evident that

the LUDWTP sludge is composed of quartz (SiO2) and

Alumina (Al2O3) in greater percentage compared to other

components. This gives an indication that the spectra

were collected from the clay particles, thus the binding

and strength properties of product of sludge will exhibit

improved strength characteristics.

CONCLUSIONCONCLUSIONCONCLUSIONCONCLUSION From the results obtained, it is can be concluded that the

sludge from Lower Usuma Dam Water Treatment Plant

(LUDWTP), Abuja, Nigeria, exhibited the conventional

sludge attributes of chemical and microstructural

composition with the following inferences:

• That suitable process condition was demonstrated

for the processing of water works sludge using

different treatment processes that are flexible to local

conditions, regulatory and economic constraints

while assuring long-term and sustainable measures

for resource utilization.

• That drying bed proved to have high solid content of

80%, in comparison with other dewatering methods,

thus offering a cost-effective method of dewatering

Sludge.

• The LUDWTP sludge has the physical characteristics

of: amorphous, Quartz and Kaolinite composition,

clay and irregular shaped, while the chemical

composition is of 28.28 % Al2O3 and 30.30 % SiO2,

which are similar to the characteristics of similar clay

deposits in Nigeria.

These findings will be of interest as resource utilisation

for engineering application and Regulatory Agencies for

reuse option as secondary raw material for building,

construction and mining industries and as the most

acceptable environmental-friendly method of sludge

disposal.

REFERENCESREFERENCESREFERENCESREFERENCES

[1] Zamora RM, Alfaro OC, Cabirol N, Ayala FE,

Moreno AD. Voalorization of Drinking Water

Treatment Sludges as Raw materials to Produce

Concrete and Mortar. American Journal of

Environmental Sciences 4(3):223-8,2008 ISSN 1553-

345X in Tay JH, Show KY, Hong SY, Chien CY and

Lee DJ. Potential Reuse of Wastewater Sludge for

Innovative Applications in Construction Industry.

Bulletin of College of Engineering,NTU,p.86;2002.

[2] Zamora RM, Alfaro OC, Cabirol N, Ayala FE,

Moreno AD. Voalorization of Drinking Water

Treatment Sludges as Raw materials to Produce

Concrete and Mortar. American Journal of

Environmental Sciences 4(3):223-8, 2008 ISSN 1553-

345X in Yunusov K. Disposal and Utilization of

Sludge from Wastewater in Production of

Aluminosilicate Catalysts. Plenum Publishing

Corporation 009-3092/83/0910-0473. Russia;1984.

[3] Dayton EA, Basta NT. Characterization of Drinking

Water Treatment Residuals for Use as a Soil

Substitute. Water Environ. Res. 2001;73:52-9;.

[4] Dunster A, Petavratzi E. Characterization of Mineral

Wastes, Resources and Processing Technologies -

Integrated Waste Management for the Production of

Construction Material;2007.

[5] Paul MR. From Conventional Drying Beds to High

Rate, High Capacity Vacuum Dewatering Beds. The

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Residuals & Biosolids Management Conference

Bellevue, Washington, July 12–5;1998.

[6] Ahmed KS. Development of Phosphate bonded

fireclay Refractory Castables [M.Sc Thesis]. Ahmadu

Bello University, Zaria, Nigeria. 1986.

[7] USEPA. Technology Transfer Handbook-

Management of Water Treatment Plant Residual,

American Water Works Association, New York:

1996.p54.

[8] Gonzalez A, Carrere S, Ruiz M.Phase

Transformation in Clays and Kaolins produced by

Thermal Treatment in Chlorine and Air

atmospheres. Latin America Applied Research

2007;37:133-9.

[9] Anwarul H, Yaseen I and Muhammad RK. Phase

and Microstructural Characterization of Kaolin

Clays from North Western Pakistan. J. Pak Mater.Soc

2009;3(2):77-90.

ACKNOWLEDGEMENT ACKNOWLEDGEMENT ACKNOWLEDGEMENT ACKNOWLEDGEMENT / / / / SOURCE OF SUPPORTSOURCE OF SUPPORTSOURCE OF SUPPORTSOURCE OF SUPPORT Nil

CONFLICT OF INTERESTCONFLICT OF INTERESTCONFLICT OF INTERESTCONFLICT OF INTEREST No conflict of interests was declared by authors.

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