Pertanika J. Sci. & Techno\. Supplement 9(1): 31 - 37 (2001)ISSN: 0128-7680

© Universiti Putra Malaysia Press

Natural Polyelectrolyte in Waste Sludge Treatment

Suleyman Aremu Muyibi, Megat Johari Megat Mohd Noor,Ding Tai Oog &: Khor Woon Kai

Department of Civil Engineering,Faculty of Engineering, Universiti Putra Malaysia,

43400 UPM, Serdang, Selangor

ABSTRACf

The study involved laboratory based investigations to determine the efficacy of a aturalPolyelectrolyte, Muringa oleifera seeds as a waste sludge conditioner. Waste sludge samplesare activated sludge from Taman Tun Dr. Ismail Wastewater Treatment Plant, KualaLumpur, Malaysia. Muringa oleifera seed was applied as dry powder(shelled blended),solution(shelled blended) and solution(shelled blended oil extracted) . Results of thestudies showed that Muringa oleifera improved the filterability of waste sludge up to 62 %in the optimum dosage range of 3000 to 6000mg/\. Sludge volume reduction of up to65% was also achievable using gravity filtration compared to the control (no Muringaoleifera added). The specific cake resistance of sludge conditioned with Muringa oleiferaaveraged 2.5 x 10 12 m/kg at the optimum dosage of 4000mg/\. The shelled blendedcategory applied in dry powder form performed the same as the solution of shelledblended but better than shelled blended oil extracted categories of Muringa oleifera.Vegetable oil from the shelled Muringa oleifera seed of up to 30% was obtained as a byproduct.

Keywords: Muringa oleifera, natural polyelectrolyte, sludge conditioner, gravity settling,vacuum IJItration, specific cake resistance

INTRODUCTION

With increasing population especially in urban areas, Malaysia like other emergingindustrialised economies is faced with the problem of increasing waste sludge generationfrom its wastewater treatment plants. In 1994, for example, the total waste sludgecollected from septic tanks and connected services amounted to 3.02 Mm' made up of1.13 Mm' (37%) from septic tanks and 1.89Mm' (63%) from connected services,increasing to 3.4 Mm' in 1998. There is, however, a reduction in sludge production of32 % from septic tanks, with increase in those from connected services to 68 % duringthe four-year period. The overall increase in sludge production is about 15% in fouryears (Indah Water 1997). In 20 years, the projected increase in sludge production willbe about 75 % using 1998 as base year. The current method of sludge disposal is madeup of oxidation pond/aerated lagoons (50 %), drying beds (30 %), others (oxidationditch, bio-filter, SBR etc. 20%. All these technologies especially oxidation ponds, anddrying beds require the use of large areas of land which is a dwindling resource withincreasing industrialisation and urbanisation.

The conditioning of waste sludge involves pre-treatment in order to facilitate waterremoval during subsequent hickening and or dewatering operations. During conditioning,small and amorphous particles are transformed into larger and stronger aggregates. Thisprocess increases the rate of water drainage and solid separation. In most dewateringoperations, the ability of sludge to form and maintain a porous structure that enhancesits compressibility is the desired goal (Clarke et al. 1997).

Sludge conditioners may be physical conditioners e.g. fly ash, diatomaceous earth etcor chemical conditioners viz. inorganic compounds (ferric chloride, lime etc) and

Suleyman Aremu Muyibi, Megat Johari Megat Mohd Noor, Ding Tai Ong & Khor Woon Kai

synthetic polymers. Synthetic polymers that can be used to alleviate this problem areexpensive and have to be imported with scarce foreign currency. A natural polymer thatis affordable and environmentally friendly (highly biodegradable), Maringa oleifera seedhas a potential to be used as a sludge conditioner for thickening and dewatering.

Maringa oleifera belongs to the family Maringaceae and is cultivated for a variety ofpurposes across the whole tropical belt (Jahn 1989). Many researchers have reported onits various uses as coagulant, Muyibi & Okuofu (1995), Ndabigengesere et al. (1995) andMuyibi (1998). The purpose of the present study, the first of its kind, was to evaluate thepotential of Maringa oleifera seed as a natural polymer for use as sludge conditioner priorto dewatering and/ or thickening.

The study that is laboratory based involved using two methods of preparation ofMaringa oleifera used in the investigation. The forms of Maringa oleifera used are, shelledblended, shelled dry powder, and shelled oil extracted. Waste sludge samples used forthe studies were obtained from Taman Tun Dr. Ismail Wastewater Activated SludgeTreatment Plant, Kuala Lumpur, Malaysia.

METHODOLOGY

Equipment

A six place jar test apparatus, Jar-Tester CZ150 was used for mixing the Maringa oleiferaseed with the waste sludge to enhance uniform and thorough distribution/mixing.National model MJ-C85N Juicer-blender with dry mill was used for the preparation ofMaringa oleifera into powder and solution for use. Sohxlet apparatus was used to extractoil from Maringa oleifera seeds. Vacuum pump connected to a Buchner funnel attachedto graduated thick walled flask was used for the determination of specific cake resistance.For gravity settling studies, 250ml graduated measuring cylinders were used.

Materials

Waste sludge samples used for the studies were collected from Taman Tun Dr. IsmailWastewater Treatment Plant, Kuala Lumpur. The dry Maringa oleifera seeds used for thestudies were obtained from Kano, Nigeria.

Procedure for Preparation of Maringa oleifera Seeds

The seed wings and coat were removed from selected dry good quality Maringa oleiferaseeds and the nuts ground to a fine powder using the National MJ-85CN. The groundpowder was divided into three portions. One portion had the oil extracted using theSohxlet apparatus.

Stock solution of the seed powder with and without oil extracted were prepared bydissolving 5 grams of each type in 500 ml tap water and mixing it thoroughly at highspeed in the National blender to extract the active ingredients. Any insoluble powderwas filtered out using a muslin cloth and the concentrated stock solution of 10,000 mg/I prepared. The third portion, the dry powder, was also set aside for use.

EXPERIMENTAL PROCEDURE

Determination of Sludge Volume Reduction with Increasing Maringa oleifera Dosage

200 ml of sludge samples were put into six, 500ml beakers and placed in the Jar Tester.The six paddles were inserted in the beakers and the speed set at 100 rpm. From thepreviously prepared stock solution of Maringa ol.eifera (shelled blended and shelled oil

32 Pertanikaj. Sci. & Techno!. Supplement Vol. 9 No.1, 2001

Natural Polyelectrolyte in Waste Sludge Treatment

extracted dosages with varying concentration of 1000 mg/1 to 6750 mg/1 were addedsimultaneously to all six beakers and mixed thoroughly for 1 minute. The six sampleswere immediately transferred into 250 ml measuring cylinders and the initial sludgeheights recorded. A control sludge sample with no Moringa oleifera applied was also putin a measuring cylinder and the initial sludge height recorded. The sludge height after30 minutes settling was recorded. The experiment was also carried out using varyingdoses of the dry Moringa oleifera (shelled) seed powder in the range of 500 mg (2500mg/l) to 1400 mg( 7000 mg/I). The results of the trial test gave the effective dosage inthe range 3750 to 5000 mg/I.

Determination of Specific Cake Resistance

The specific cake resistance is used to evaluate the effect of different dosages ofchemical conditioners and combination of sludge and conditioning agents on thespecific resistance and quality of the cake. A plot of specific resistance versus dose canbe used to determine the optimal operating condition.

Theory

Flow through the sludge cake and filter medium may be considered as flow throughporous media. Darcy's law may be used to model the process.

where Q = flow rate of filtrateV = Volume of waterA = Area of flowk = conductivityh = headL = distancet = time

Q = dV = 1<A..l\hdt II (1)

The resistance parameter depends on Reynolds number, porosity of the media,distribution of grains, and other characteristics of the media. Using the Hagen-Poiseuillelaw for pipe flow,

kgK=­

v

where K = intrinsic permeabilityv = kinematic viscosityg = gravity

dV KMP-=--dt Illl

where M' = positive pressure differentialII = depth of the mediumIl = dynamic viscosity of the filtrate

PertanikaJ. Sci. & Techno\. Supplement Vol. 9 No.1, 2001

(2)

(3)

33

Suleyman Aremu Muyibi, Megat Johari Megat Mohd oor, Ding Tai Ong & Khor Woon Kai

byThe intrinsic resistance, r, may be defined as r = 11k. The cake resistance Rc is given

R = r~Lc c

where rc

= intrinsic resistance of cake.

(4)

The cake resistance and filter medium resistance are independent, so the totalresistance, R of cake and filter may be added together to get,

(5)

where Rf

= resistance of the filter medium

The volume of cake formed, Vc is

v = A..6Lc (6)

Let the specific deposit, be the volume of cake formed per unit volume of filtrate,then

Equation (3) becomes;

dVdt

aV = A..6L (7)

(8)

Expressing the intrinsic resistance, rc' in terms of mass of dry cake solids formed perunit volume of filtrate,w,the specific resistance, r

wcis related to r

cby;

Substituting in equation(8) we have

(9)

dVdt

LlM'A 2

(10)

34

I, IV(wrrcV R f )dt=1-l --+-- dV~PA2 MA

o 0

At constant pressure, on integration over time,

PertanjkaJ. Sci. & Techno\. Supplement Vo\. 9 No.1, 2001

(11)

(12)

Natural Polyelectrolyte in Waste Sludge Treatment

t I-lwrweV I-lR f-= +--V 2~PA2 ~A

The specific resistance rwe is calculated from the slope m of the line

2~A2r =---m

we I-lW

(13)

(14)

Procedure fM the Detennination of Specific Cake Resistance

200 ml of the sludge sample was placed in 500 ml beakers and varying dosages(lOOO to6000mg/l) of Moringa oleifera powder was added. The beakers were placed in the jar testapparatus. The paddles were inserted and thoroughly mixed at 100 rpm for 1 minute.The speed was reduced to 40 rpm and continuously stirred to prevent sludge settling.50 ml of each of the prepared samples was added to the Buchner funnel containing afilter pad and connected to the vacuum pump. Vacuum pressure of 69000 /m2 wasapplied at 15 seconds intervals and the volume of the filtrate measured. Observationswere made until the vacuum broke or the filtrate volume remained constant.

RESULTS AND DISCUSSION

Gravity Settling Studies

Table 1 shows the summary of the results of gravity settling of waste activated sludge forvarying dosages of Moringa oleifera, shelled blended and shelled blended oil extractedfrom 3750 to 5000 mg/1. It was observed that increasing dosage of Moringa oleiferaresulted in increasing reduction in sludge volume compared to the control. For theshelled blended category, from a control with sludge reduction of 4.6%, increasingdosage of Moringa oleifera resulted in increase in sludge volume reduction reaching apeak at 12% at 4750 mg/I dosage and reducing to 10 % at 5000 mg/I dosage. For theshelled blended oil extracted category, increasing dosage of Moringa oleifera also resultedin increased reduction in sludge volume from the control of 4% reduction to 6.7% at3750 mg/I, to 8.7% at a dosage of 4250 mg/I and decreasing to a minimum of 7.3 %at 5000 mg/I dosage. Similarly, in Table 2 for the dry powder(shelled blended)application, it was observed that sludge volume reduction increased with increasingdosage of Moringa powder from 5 % at control to 13 % at 1200 mg (6000 mg/I). Afterwhich continued dosage gave constant sludge volume reduction.

When the results are compared to the control, it was observed that the shelledblended category was able to achieve a maximum of 2.6 times reduction in sludgevolume compared to the control at a dosage of 4750 mg/1. The shelled blended oilextracted category was able to achieve a maximum of 1.9 times sludge volume reductionat dosage of 4250 mg/I . Application of the dry powder(shelled blended) was also ableto achieve a maximum of 2.6 times sludge volume reduction compared to the control.

In general, application of the dry seed powder (shelled blended) was found to bemore effective than using the shelled blended oil extracted solution. Further studiesneed to be carried out in terms of cost and ease of application, as well as equipment andfacilities which will be required for each application method so as to select the mostefficient method application. The findings from this study the first of its kind, has apotential for its application to existing sludge holding tanks and drying beds as well asnew sludge treatment plants. The capacity of new sludge holding tanks and drying beds

PertanikaJ. Sci. & Techno\. SupplementVo\. 9 No.1, 2001 35

Suleyman Aremu Muyibi, Megat Johari Megat Mohd oor, Ding Tai Ong & Khor Woon Kai

can be reduced considerably whilst existing ones can be retrofitted with Maringa oleiferadosing system after pilot scale studies to enhance the filterability and settling characteristicsof the sludge. It is pertinent to note that up to 30% vegetable oil was extracted from theshelled Maringa oleifera seed. Further studies may be carried to explore possible commercialuse of the oil.

TABLE 1Summary of results of gravity settling studies of waste activated sludge

on application of varying dosages of Moringa oleifera seed(shelled blended and shelled oil extracted)

Dosage(mg/I)

Sludge volumereduction (%) aftergravity settling for

30 mins.

Ratio of sludgevolume reduction

after gravity settlingto control

Control375040004250450047505000

ShelledBlended

4.67.389.39.3

1210

Shelledblended

oilextracted

4.66.788.7887.3

Shelledblended

11.61.7222.62.2

Shelledblended

oilextracted

11.51.91.71.71.71.6

TABLE 2Summary of results of gravity settling studies of waste activated sludge

on application varying dosages of dry Moringa oleiferaseed powder (shelled)

Dosage of shelledblended Dry

Moringa powder(mg)

Control500(2500 mg/I)600(3000 mg/I)700(3500 mg/I)800(4000 mg/I)900(4500 mg/I)1000(5000 mg/I)1100(5500 mg/I)1200(6000 mg/I)1300(6500 mg/I)1400(7000 mg/I)

Sludgevolume

reduction(%after gravitysettling for

30mins.

59

10111111.51212.5131313

Ratio of sludgevolume

reduction aftergravity settling

to control

11.822.22.22.32.42.52.62.62.6

36 PertanikaJ. Sci. & Techno\. Supplement Vo\. 9 No.1, 2001

Natural Polyelectrolyte in Waste Sludge Treatment

Determination of Specific Cake Resistance and Optimum Dosage

For each dosage of shelled blended Maringa oleifera applied, plot of t/V versus V wasplotted which gave straight lines from which the specific resistances were calculatedusing equation 14. From Fig. 4, it is observed that the optimum dosage of Maringa oleiferawas 4000 mg/I with specific resistance, rwc of 2.5 x 10 12 m/kg for vacuum filtration.This value compares well with that reported by Droste(l997) for synthetic polymers.

100",

)000

,- ..._.....,..

1000

000 l.

o

u£~ 1001Q. .III

.. '"C 3.00 t- .._--ri; .~ :..----------.----..:-~-~---=1-""----~f---

! 2oo~ - -1 ioc i

j I

'r !."J" j:;m L_ 3000 <000 1000

Concentration of MorillgJ Oteiftra Seeds(mgII)

1 Specific cake resistance variation with Maringa oleifera dosageFig.

CONCLUSIONS

1. Within the economic dosage range of Maringa oleifera of 3750 to 5000 mg/I, sludgevolume reduction increased with increasing dosage.

2. The shelled blended category applied in dry powder form performed better than thesolution of shelled blended oil extracted categories of Maringa oleifera.

3. For vacuum filtration, the specific cake resistance was found to decrease withincreasing dosage of Maringa oleifera to an optimum of 2.5 x 1012 m/kg at a dosageof 4000 mg/1.

4. Up to 30% vegetable oil was extracted from the Maringa oleifera seed using theSoxhlet method.

REFERENCES

CLARKE J. W., W. Jr. VlESSMAN and M. J. HAMMER. 1997. Water Supply and PoUution Control. Harper &Row Publishers.

DROSTE, R. L. 1997. Theory and Practice oj Water and Wastewater Treatment. John Wiley & Sons Inc.

INOAH WATER SON. BHD. 1997. Sludge treatment and disposal strategy. Planning Report.

JAHN, S. A. A.1989 Using Moringa oleiJera seeds as coagulants in developing countries. J A mer. WaterWorks Association 8: 43 - 50.

MUYlBI, S. A. and C. OKUOFU. 1995. Coagulation of low turbidity surface waters with Moringa oleiJeraseeds. International Journal oj Environmental Studies 48: 263-273

NOABIGE GESERE, A., K.B. NARASlA and B.G. TALBOT. 1995. Active agents and mechanisms of coagulationof turbid waters using Moringa oleiJera. Water Res. (29): 703 - 710.

SULEYMA: AREMU MUYlBI. 1998. Moringa oleiJera seeds in water treatment.]. Insti. Engi. Malaysia. (59)3:37 - 50.

PertanikaJ. Sci. & Techno\. Supplement Vo\. 9 o. 1, 2001 37