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Application of locally produced activated carbons in

water treatment

Jane Misihairabgwia,*

, Victor Ntulia, Abisha Kasiyamhuru

a, Sekesai Zinyowera

b,

Ignatious Ncubec, Victor Chipofya

d.

*, a

Department of Biochemistry, University of Zimbabwe, P.O. Box MP167, Harare,

Zimbabwe. Tel: +263 4 308047,Fax:+263 4 333678.

bDepartment of Medical Microbiology, Medical School, Parirenyatwa Hospital, Harare,

Zimbabwe.

cDepartment of Biochemistry, Microbiology and Biotechnology, School of Molecular and

Life Sciences, University of Limpopo, P. Bag X1106, Sovenga 0727, South Africa. Tel:

+27 15 268 2341, Fax: +27 15 268 3234.

dCentre for Water, Sanitation, Health and Appropriate Technology Development, Malawi

Polytechnic, University of Malawi, P. Bag 303, Chichiri, Blantyre 3, Malawi. Tel:+265 1

870 411, Fax: +265 1 870 578.

Corresponding author: E-mail:[email protected]@yahoo.co.uk
mailto:[email protected]:[email protected]


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Abstract

Activated carbon has been widely used worldwide as an effective filtration or

adsorption material for removing biological and chemical contaminants from drinking

water. In most developing countries, the activated carbon is imported at high cost,

limiting the quantities of safe drinking water available to the people. The study was

directed at assessing the applicability of activated carbon produced locally in water

treatment. An assessment of the carbon prepared from macadamia nut shell to remove

contaminants in water was carried out. After treatment with activated carbon, the

chemical oxygen demand of the water was reduced from 54 to 8 mg/l. The total microbial

load of the water was reduced from 800 to 50 cells /ml. The turbidity of the water was

reduced from 19.8 to 3.1 Nephelometric Turbidity Units (NTU). Sulphates and nitrates

were reduced from 53 to 21 mg/l and 0.6 to 0.4 mg/l respectively. Total coliforms, faecal

coliforms and faecal streptococci were adsorbed completely from initial concentrations of

10, 4 and 2 c.f.u/100 ml respectively. Carbons prepared from macadamia nut shells,

baobab shells and marula fruit stones were evaluated for their ability to adsorb the

parasitesEntamoeba histolytica, Giardia lamblia, Chilomastix mesneli, Entamoeba coli,

Endolimax nana, Iodamoeba butschli and Entamoeba hatimanaifrom water. All carbons

were capable of adsorbing the parasites, with carbons prepared from macadamia nut

shells and baobab shells completely adsorbing all the parasites. Results indicate that the

carbons produced in this study are suitable for use in the removal of contaminants from

water.

Key words: activated carbon, adsorption, water treatment


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1. Introduction

The provision of safe water to the people is an urgent development priority of the

Southern African Region. The continual expansion and increasing of urban centers in

developing nations has resulted in pollution of water sources. Conventional water

treatment plants use processes such as pre-chlorination, fluoridation, alum coagulation

with hydraulic flocculation, sedimentation, dual anthracite and sand filtration and post-

chlorination to remove dyes and metal ions in contaminated waters (Ahmed et al.,2004).

In countries with poor economic base, the high cost of importing the water treatment

chemicals prevents consistently good drinking water quality being achieved in many

cases.

In recent years, there has been research focusing on the use of appropriate, low-

cost technology for the treatment of drinking water in the developing world. Research has

also been focused on the indigenous production of water treatment chemicals using

locally available raw materials (Warhurst et al.,1997). Activated carbon has been widely

used worldwide as an effective filtration or adsorption material for removing biological

and chemical contaminants from drinking water. Currently, Zimbabwe uses 20 tonnes of

activated carbon per month for urban water treatment and imports the carbon at high cost.

The high cost of importing the activated carbon puts a significant burden on the water

treatment budget since foreign currency is scarce.

In an effort to reduce the proportion of people without sustainable access to safe

drinking water, there is a need to optimize the production of activated carbon from locally

available aggroforestry wastes and apply it for water treatment in diverse communities. A

wide variety of carbons have been prepared from agricultural wastes such as rice husks,


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pith, bagasse, sawdust, Coir pith, parthenium plant, hazelnut shells and apricot stone

(Kardirvelu et al., 2001, 2003; Kobya, 2004; Ayyappan et al., 2005; Kobya et al., 2005).

Our previous study has shown that activated carbon prepared from local agroforestry

waste residues such as macadamia nut shells, baobab shells and marula fruit stones is

effective in the removal of heavy metal ions from aqueous solution (Misihairabgwi et al.,

2007). Each of the activated carbons has its own characteristic properties and variation

exists in the efficiency of removal of a range of impurities from waste water.

Characterisation of the carbons is important in the formulation of a consistent quality

carbon that can be used in water treatment plants.

The main aim of the study was to apply activated carbon prepared from local

agroforestry wastes in water treatment and assess the efficiency of the carbons in the

removal of organic, inorganic and biological contaminants in water.

Infections of Giardia lamblia and Entamoeba hystolytica are quite high in

Zimbabwe, causing diarrhoea and other water borne diseases in communities and

households, especially in rural communities. Boiling is an effective, simple method in

destroying many water borne pathogens but it is impractical for the rural poor due to the

scarcity of firewood and because it is time consuming. The study was also aimed at

developing a sustainable way of providing safe water to various communities by

assessing the effect of applying activated carbon in the removal of waterborne parasites

from water.


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2. Methodology

2.1 Activated carbon

Activated carbons prepared from macadamia nut shells (MNS), baobab shells

(BBB) and marula fruit stones (AML) were used in this study. The carbons were

obtained from the Centre for Water Sanitation and Hygiene, Malawi Polytechnic,

University of Malawi. All the biomass samples were activated and carbonized in a one-

step pyrolysis method in the presence of steam at 750oC and final soak time of 30 min

(Warhurst et al., 1997; Misihairabgwi et al., 2007).

2.2 Application of activated carbon to raw water

Activated carbon prepared from macadamia nut shells was used for the treatment

of water collected from Lake Chivero, Harare. The experiments were carried out in

triplicate. Samples of the water (100 ml) were mixed with carbon (0.1 g) in 250 ml

Erlenmeyer flasks. The mixtures were shaken at 200 rpm in a temperature controlled

shaker (Vacutec Cat N 10 4002) at (25 2oC) for 2 h then filtered using a Whatman

filter paper N 1 size 15 to remove the carbon. Full chemical and bacterial analysis were

done to check the water parameters after treating with activated carbon. The chemical

analysis included determination of alkalinity, chemical oxygen demand, cadmium,

calcium, chloride, copper, dissolved oxygen, electrical conductivity, iron, manganese,

magnesium ,lead , nitrate, pH, sulphate, total hardness, and turbidity. Bacteriological


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analysis included determination of total coliforms, faecal coliforms (E. coli); faecal

streptococci; and agar plate count at 22oC and 37

oC.

2.2.1 Determination of alkalinity.

A sample of water (100 ml) was diluted with distilled water (100 ml) and titrated

with 0.02 N HCl using Bromocresol 1 methyl red as an indicator. A blank was run which

contained sodium carbonate instead of the water sample. Alkalinity was calculated in

mg/l using the following equation (Clesceri, et al., 1989)

mg/l Alkalinity = 10(sample titre blank titre)

2.2.2 Chemical Oxygen Demand

A sample of water (50 ml) was poured into a 250 ml Erlenmeyer flask with

ground-glass 24/40 neck. Mercuric sulphate (HgSO4) (1 g) was added, followed by

several glass beads. Sulphuric acid (5 ml) reagent was poured into the flask with mixing

to dissolve HgSO4. After cooling, 0.04 M K2Cr2O7 (25 ml) solution was added. The flask

was attached to a 30 mm jacket Liebig condenser with 24/40 groundglass joint with

cooling water. The remaining sulphuric acid (70 ml) reagent was added through the open

end of the condenser. The mixture was refluxed for 2 h with a very small beaker covering

the open end to prevent entry of foreign material. After refluxing the mixture was cooled

and diluted to twice the volume using distilled water. The solution was cooled to room

temperature (25 2oC) and titrated with 0.25 N ferrous ammonium sulphate (FAS) using


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2 to 3 drops of ferroin indicator. The end point of the titration was the first sharp change

from blue-green to reddish brown that persisted for 1 min or longer. In the same manner,

a blank containing the reagents and a volume of distilled water equal to that of the

sample, was refluxed and titrated with FAS (Clesceri et al.,1989). COD was calculated

as follows:

2500.0=c

bM

where M is morality of FAS solution; b is volume of 0.04 M K2Cr2O7 solution titrated

(ml) and c is volume FAS used in the titration (ml).

COD as mg O2/l = [(A-B) xMx8000]/ml sample

where A is blank titre, B is sample titre

2.2.3 Dissolved Oxygen

A dissolved oxygen bottle which was air tight was filled with water sample (100

ml). Manganese solution (0.5 ml) and OH--l

--N3 (0.8 ml) were added. The bottle was

closed and shaken. The precipitate of MNO (OH)3was left to sediment about half way in

the bottle and was shaken again. For the second time the precipitate was left to sediment

about a third of the height of the bottle and concentrated phosphoric acid (1 ml) was

added and mixed well. When the solution was dissolved completely, the solution (50 ml)

was transferred into a conical flask and titrated with 0.02 N methiosulphate (NaS2O8) to a

straw yellow colour. Four drops of starch indicator were added and titration was

continued until a colourless solution was obtained. Dissolved oxygen was calculated as

follows:


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)(50

64000

DV

VChatemethiosulpa

=

where a is O2 (mg /l) , V is Volume capacity of bottle, C is concentration of thiosulphate

and D, is Volume of reagents (Clesceri et al.,1989).

2.2.4 Determination of Conductivity and pH

Conductivity of the water was determined using a conductivity meter, according

to the manufacturers instructions. The pH was determined on a Cripson GLP21 pH

meter.

2.2.5 Determination of Nitrates.

Nitrates were determined using a UV spectrophotometer (Shimadzu UV -160A).

Calibration standards ranging from 0.25-2.00 mg/l nitrate solution were prepared and

were used to plot a standard curve. Absorbance of the sample was read on the

spectrophotometer using quartz curvets at 210 nm.

2.2.6 Determination of sulphates.

Calibration standards were prepared from sulphate solution stock ranging from

10-80 mg/l sulphate. The standards were then used to plot a calibration graph. A

photometer (Spectronic 20 Genesys) was used to measure turbidity of the sulphates in the

sample. A sample (100 ml) was mixed well into an Erlenmeyer flask with citrate buffer

solution (20 ml) using a stirrer at constant speed. While stirring, a spatula of barium


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chloride was added and stirring continued for 1 min. After stirring, the solution was

poured into an absorption cell of the photometer and turbidity was measured at 450 nm.

The concentration of sulphate in the sample was then calculated from the calibration

graph.

2.2.7 Determination of turbidity.

A turbidity meter (2100N model) was used to measure turbidity of the sample.

The units for turbidity are nephelometric turbidity units (NTU).

2.2.8 Total hardness.

Calcium solution 0.2 N (10 ml) was diluted with distilled water (50 ml) and

titrated against E.D.T.A solution, using 2 ml ethanolamine buffer and 2 drops of

Eriochrome black T indicator solution in a 250 ml Erlenmeyer flask. The colour change

was from red to blue. Water samples, treated with activated carbon and untreated (50 ml)

and a blank (distilled water) were also titrated against E.D.T.A as above and titrations

were carried out three times. Total hardness was calculated as follows:

Total hardness as mg/l calcium carbonate = 20.018Volume of E.D.T.A consumed.

Final total hardness was obtained by subtracting the blank value from each sample value.


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2.2.9 Determination of calcium.

Water sample, treated and untreated (50 ml) was mixed with 2 M sodium

hydroxide (2 ml) in a 250 ml Erlenmeyer flask and titrated three times with E.D.T.A

using murexide indicator (0.1 g). The volume of titre was recorded (A). At end point,

colour changes from pink to purple. Standard calcium solution (200 mg/l) (10 ml) was

diluted into a 50 ml volumetric flak and titrated with E.D.T.A as above, and the volume

of the titre was recorded as F. A blank titration was carried out by titrating with distilled

water (50 ml), and the volume of the titre was recorded as B (Clesceri et al.,1989).

Calcium concentration was calculated as follows:

c

Fba

=

3200= 3200 F

where a, is Ca concentration (mg/l), b is (A-B) and c is the sample (ml).

2.2.10 Determination of Chloride.

A known concentration of chloride ions (1 mg/ml)in sodium chloride solution

(100 ml) was titrated with 2 N silver nitrate solution using two drops of potassium

chromate as an indicator. The colour change at end point was a slightest perceptible

reddish colour. After this, water sample treated and untreated and a blank (distilled water)

(100 ml) was treated as above and chloride concentration calculated as follows:

mg/l of Chloride = Volume of silver nitrate 10.


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Final chloride concentration was established by subtracting the blank value from each

sample value and average obtained.

2.2.11 Enumeration of Feacal Coliforms (E coli)

The water sample (10 ml) was diluted with sterile water in a 100 ml volumetric

flask and was mixed well. An absorbent pad was aseptically placed into each petri dish

and membrane lauryl sulphate broth MLSB (2 ml) was pipetted onto each pad. The broth

was allowed to soak until the pad was saturated. The membrane filter was placed with

grid upside down. A sterile funnel was placed on the filter base and sample (100 ml) was

poured into the funnel. The sample was vacuum filtered and membrane was placed on

growth media, grid side up. The plates were later incubated at 30C for 4 h, and then

followed by 44C for the remaining 20 h. For each batch sample, a blank was prepared. A

colony counter (Leica Quebec Darkfield colony counter) was used to count the E coliin

the water sample.

2.2.12 Total Coliform Determination

A maximum of 10 yellow colonies were picked from the membrane, initially

plated for E colienumeration and were inoculated aseptically using platinum loops into

Durham tubes. The tubes contained lactone peptone water (5 ml) and tryptophane (1 g).

The tubes were incubated at 37C for 24 h. A colour change from pink to yellow and the

presence of gas in Durham tubes confirmed the presence of coliforms. Total coliforms

were calculated as follows:


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d

cba

=

where, a, is Total Coliforms; b is the number of presumptive colonies, c is the number of

positive tubes and d, the number of inoculated tubes.

2.2.13 Enumeration of Streptococci.

Enumeration of Streptococci was carried out in a similar manner to the

enumeration ofE. coli.The sample (10 ml) was diluted in a 100 ml volumetric flask and

was mixed well. An absorbent pad was aseptically placed into each petri dish and

membrane lauryl sulphate broth MLSB (2 ml) was pipetted onto each pad. The broth was

allowed to soak until the pad was saturated. The membrane filter was placed, with grid

upside down. A sterile funnel was placed on the filter base and sample (100 ml) was

poured into the funnel. The sample was vacuum filtered and membrane was placed on

growth media, grid side up. The plates were incubated at 37C for 4 h, and then followed

by 44C for the remaining 44 h. Red and maroon colonies were counted using a colony

counter (Leica Quebec Darkfield colony counter).

2.2.14 Agar Plate Counts.

A sample (1 ml) was used for serial dilutions up to 10 times. An aliquot (100 l)

of dilution number 10 was used for inoculation of each nutrient agar plate followed by

even spreading under aseptic conditions. Two batches of plates were incubated, one batch

was incubated for 24 h at 37oC and the other was incubated at 22C. After the stipulated


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times, counting of was done manually using a colony counter (Leica Quebec Darkfield

colony counter).

2.3 Removal of Parasites from water

Stool samples were collected from Tafara Primary School in Harare urban.

Parasites (cysts) were isolated by the formal ether concentration method. Using the

formal ether method, faeces (1g) were emulsified in a 15 ml tube containing 10 %

formalin. The sample was filtered using an 80 mesh sieve into another 15 ml tube and

centrifuged for 1 min at 3000 rpm using Centronic selecta centrifuge. The supernatant

was decanted then the residue was resuspended with 10 % formalin (7 ml). 5% ether (3

ml) was also added and the mixture was shaken vigorously. The mixture was further

centrifuged at 3000 rpm for 1 min, and supernatant discarded. The sediment was

concentrated by the Discontinuous Percoll Gradient method. Using the Discontinuous

Percoll Gradient method, approximately 1 ml of sediment was thoroughly mixed with

sheaters sugar solution (500 g sucrose, 320 ml tap water and 6.5 g phenol). Centrifugation

of the mixture was done at 2000 rpm and the meniscus of the fluid was washed with

distilled water. The cyst was examined under a compound microscope (Carl Zeiss KF2).

Cyst suspension (1 ml) of known concentration was diluted with 99 ml distilled water.

Activated carbons from macadamia nut shells, baobab shells and marula fruit stones (0.2

g) were added into the diluted suspensions in flasks, and then the flasks were sealed with

parafilm. The mixtures were shaken at 100 rpm in a controlled shaker (Vacutec Cat N 10

4002) bath at room temperature 25C2 C for 24 h. The mixtures were then filtered

using Whatman N1 size 30 filter papers, into 15ml centrifuge tubes. Centrifugation was


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carried out for 3 min at 3000 rpm then the sediments were transferred into clean tubes

and the supernatants discarded. The sediments were mixed and viewed on a light

microscope to determine the count of parasites present. Two drops of 0.2 N iodine was

added for easier viewing and counting of parasites. Parasite concentration was counted

using a hemocytometer. A control was set which only contained 1 ml sample and 99 ml

distilled water, without activated carbon.

3 Results and Discussion

3.1 Application of activated carbon to raw water.

Many water treatment works often use activated carbon to reduce odor caused by

algae decay in drinking water. Tables 3.1 and 3.2 show the results of the full chemical

and bacteriological analysis of raw water, both treated with activated carbon and

untreated. The alkalinity for treated water, 139 mg/l HCO3, was higher than that for

untreated water, 119 mg/l HCO3. This is because the carbon used was alkaline, with a pH

value of 9.98. There was a marked adsorption of non-biodegradable organic material

from the water. The chemical oxygen demand was reduced from a concentration of 54

mg/l to less than 8 mg/l. Organic compounds are degraded by microorganisms in water

and this leads to consumption of dissolved oxygen in the water. A slightly higher

percentage saturation of dissolved oxygen of 102.5 % was noted in untreated water

compared to that in treated water, 98.5 %. Activated carbon adsorbed most of the organic

compounds and the microorganisms that utilize the oxygen for the degradation of

organics. Organic compounds also cause colour in water leaving water unacceptable to


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drink. Activated carbon adsorbed the organics, thus reducing turbidity from 19.8 to 3.21

NTU. Low levels of nitrates and sulphates were found in both treated and untreated

water, both being below the recommended limit and maximum limit allowed by Standard

Association of Zimbabwe (SAZ) which is 10 mg/l for nitrates and 200 mg/l for sulphates.

Nitrates and sulphates pose a problem of eutrophication in the aquatic ecosystem, and

thus result in odors in water if found in levels above the maximum limit. High cost for

water treatment plants would be needed to remove high concentration of algae due to

eutrophication. On treatment of raw water with activated carbon, nitrates were reduced

from 0.6 to 0.4 mg/l and sulphates from 54 to 21 mg/l (Table 3.1). The treated water

contained very low concentrations of heavy metals. The quantity of the metals in raw

water was below the recommended limit under SAZ. Activated carbon was capable of

removing microorganisms such as bacteria from water. It is not understood if activated

carbon removes bacteria by entrapment or by adsorption. Faecal coliforms and faecal

streptococci were removed from raw water (Table 3.2).

Streptococci and total coliforms were completely removed from the water by

carbon, from initial concentrations of 2 cells/100 ml and 10 cells/100 ml respectively.

Total microbial counts at 37o

C in the water were reduced from 860 cells/100 ml sample

to less than 50 cells/100 ml sample.

Some bacteria which are found in water are very harmful to human health and

need disinfectant such as chlorine for the removal. Activated carbon is applied first in the

water treatment plant before disinfectant. This reduces the quantity of disinfectant needed

to kill pathogens and thus it is cost effective to use activated carbon for water treatment.


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3.2 Removal of parasites from water.

Activated carbons with capacity to remove parasites from water are shown in

Table 3.3. Carbons prepared from macadamia nut shells and baobab shells removed all

parasites from the suspension sample of parasites which was under investigation.

Activated carbon prepared from marula fruit stones managed to remove some

parasites completely such as Lodamoeba butschii; Entamoeba coli andGiardia lamblia

from the suspension of parasites. The percentage removal of parasites such asEntamoeba

histolytica, Chilomastic mesinnelli, Endolimax nana and Entamoeba hartmanni by

activated carbon prepared from marula fruit stones was 50 % for all the parasites.

During treatment of water, conventional methods such as chlorination is not

effective in removal of parasites from water thus cheaper and effective methods are

needed. Activated carbon produced from agroforestry waste has the potential of

removing microbial contaminants such as parasites and bacteria from water and thus is

very much ideal to use in water treatment plants. Research is currently being directed at

elucidating the mechanism of removal of the parasites from water by activated carbon

since it is not fully understood if parasites are removed from water by entrapment or

adsorption on the adsorbent.

4. Conclusion

The results of the study show great potential of local agroforestry waste based

carbons to remove toxic organic compounds, biological contaminants and toxic metals

from water using low cost, domestic and environmentally safe technology.


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Carbons prepared from macadamia nut shells, baobab shells and marula fruit

stone carbons produce high quality carbons which compare well with commercially

available carbons found in Zimbabwe and if produced on a large scale, the water

treatment budget would be reduced and funds could be diverted to other uses. Local

production of activated carbon from agroforestry wastes can improve the quality of

drinking water and palatability, whilst reducing importation and expenditure of foreign

exchange, and contributing to improved local incomes.

5. References

Ahmed, E.R., Namasivayam C., Kadirvelu K., (2004) Coirpith, an agricultural waste by-

product, for the treatment of dyeing wastewater. Bioresource. Technology. 48,

79-81.

ASTM (1991) D4607-86: Standard test method for determination of iodine number of

activated carbon. American Society for Testing and Materials, Philadelphia,

U.S.A.

Ayyappan, R., Carmalin Sophia, A., Swaminathan, K., Sandhya, S. (2005). Removal of

lead from aqueous solution using carbon derived from agricultural waste. Process.

Biochemistry. 40,1293-1299.

Clesceri, L.S, Greenberg, A.E, Rhodes, T. (1989). Standard methods for the examination

of water and waste water. 17th

Ed. American Public Health.

Giles C. H. and Nakhwa S. N. (1962) Studies in adsorption. XVI. The measurement of

specific surface areas of finely divided solids by solution adsorption. Journal .

Application. Chemistry. 12,266-273.


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Girgis , B. S., Yunis, S.S ., Soliman ., (2000) . Characterisation of activated carbon from

pecan hulls in relation to conditions of preparation. Matter. 57, 164-172.

Hasar, H., (2003). Adsorption of nickel from aqueous solution onto activated

carbon prepared from almond husk. Journal. Hazard. Mater. B97, 49-57.

Haykiri- Acma H, Yaman, S .,Kabyrak, S .(2005). Gasification of Biomass chars in steam

nitrogen mixture .Energy Conservation. 56,76-80.

Helleur, R, Liu, D, Ikura, M, (2001). Caracterisation and potential application of

pyrolytic char from ablative pyrolysis of used tyres. Journal. Annual.

Application.Pyrolysis. 59,813-824.

Kadirvelu, K., Thamaraiselvi, K., Namasivayam, C., (2001). Removal of heavy metals

from industrial wastewaters by adsorption onto activated carbon prepared from an

agricultural solid waste. Bioresource. Technology. 76, 63-65.

Kadirvelu, K., Kavipriya, M., Karthika, C., Radhika, M., Vennilamani, N., Pattabi, S.,

(2003). Utilization of various agricultural wastes for activated carbon preparation

and application for the removal of dyes and metal ions from aqueous solutions.

Bioresource. Technology. 87, 129-132.

Kobya, M., (2004). Adsorption, kinetic and equilibrium studies of Cr(VI) by hazelnut

shell activated carbon. Adsorption. Science. Technology. 22, 51-64.

McConnachie, G., Mtawali A., Young R., (1994) Design aspects of hydraulic

flocculates, 3,284-288.

Meyer V., Carlsson F. H. H. and Oellermann R. A. (1992) Decolourisation of textile

effluent using a low cost natural adsorbent material. Water Science. Technology.

26, 1205-1211.


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Minkova, V., Razvigorova, M., Bjornbom, E., Budinova, T., (2003). Effect of water

vapour and biomass nature on yield and quality of the pyrolysis product from

biomass. Fuel. Process. Technology. 70,53-61.

Morton, I. F., (1991). The horseradish tree, Moringa pterygosperma (Moringaceae)-a

boon to arid lands Economic. Botanic. 45, 318-333.

Tsai, W.T, Chang, C.Y,. Lee, S.L., (1997) Preparation and characterization of activated

carbons from corn cob. Carbon .35, 1198-1200.

Warhurst, A.M., McConnachie, G.L., Pollard, S.J.T., (1997). Characterisation and

applications of activated carbon produced from Moringa oleifera seed husks by

single step steam pyrolysis. Water. Resource. 31 (4), 759-766.


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Table 3.1 Chemical analysis results of water treated with activated carbon (MNS)

and untreated.

Treated Untreated

Maximum

allowedlimit

(Zimbabwe

Standards

Association)

Parameters Units

Alkalinity mg/l HCO3 139 119 *

Chemical Oxygen Demand mg/l


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Table 3.2 Full bacteriological analysis results of water treated with activated carbon

prepared from macadamia nutshells

Treated Untreated

Standards

Associationof

Zimbabwe

limit

Parameters tested Units

Total coliforms number/100 ml 0 10 0

Faecal Coliforms (E.coli) number/100 ml 0 4 0

Faecal streptococci number/100 ml 0 2 0

Agar plate count at 22oC number/1ml 50 860 100

Agar plate count 37oC number/1ml 5 800

100


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Table 3.3 Removal of parasites from water by activated carbon

Concentration of cells/ml

Parasite Initial After treatment

with carbonfrom baobab

shells

After treatment

with carbon frommacadamia nut

shells

After treatment

with carbon frommarula fruit

stones

Entamoeba

hysolytica

6.0x106 No parasites No parasites 2.0x10

3

Chilomastix

mesneli


3

Endomalix

nana


3

Entamoeba

hatimanai


4

Giardialamblia

3.4x106

No parasites No parasites No parasites

Entamoeba

coli

7.8x106 No parasites No parasites No parasites

Iodamoeba

butschii

1.6x106 No parasites No parasites No parasites

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