natural coagulants

USE OF NATURAL COAGULANTS IN WATER TREATMENT PROCESS

NAME: SAMSON NYAMONGO NYAMWEYA

REG. NO.: EECQ/00502/2011

SUPERVISOR: PROFESSOR GEORGE THUMBI

INTRODUCTION 

Availability of safe drinking water is an emerging global challenge.

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Turbidity in raw water is caused by tiny suspended solids.

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world wide, most water treatment facilities use alum to remove turbidity.

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Alum is expensive and generates large quantities of sludge.

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Extracts from some protein-containing seeds have been found to be

effective in the reduction of turbidity. 

The aim of the project is to find out if the natural coagulants can be a substitute to alum and determine optimum dosages.

PROBLEM STATEMENT  Turbidity brings about a serious challenge in the water treatment

process. Suspended and colloidal matter such as clay and silt are responsible for turbid water. Surface water has high levels of turbidity and therefore coagulants have to be used to improve water quality by reducing turbidity. Aluminum salts are commonly used for coagulation in the water treatment process. Alum is not available locally thus high cost incurred for importation and produces large amount of sludge during treatment of water.

OBJECTIVES 

Main objective

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Use of natural coagulants to reduce turbidity in the water treatment process.

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Specific objectives

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To evaluate the effectiveness of using natural coagulants on turbidity reduction in surface water.

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To determine the optimum amount of natural

coagulant to be added for turbidity removal.

LITERATURE REVIEW 

Surface water is prone to contamination as compared to ground water.

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To evaluate the quality of drinking water, various parameters have to be considered. The key ones are:

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Turbidity: refers to the cloudiness of water and is caused by suspended particles in the

water. 

Turbidity is a major challenge in treatment of surface water, but can be neglected in treatment of groundwater.

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Turbidity is measured in Nephelometric Turbidity Units (NTU), which is an optical measurement, where a light beam passes through the water sample, and the amount of scattered and absorbed light is detected.

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Other important parameters in water treatment are: bacteriological quality, hardness, pH and alkalinity, organic content, conductivity, and heavy metals.

METHODOLOGY 

The extracts used as natural coagulants were obtained from; Glycine max (Soya beans), Vigna unguiculata(Cowpeas), and Phaseolus vulgaris(ordinary beans).

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The seeds were dried and then ground to a fine powder using a mortar.

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The powder obtained was weighed, dissolved in distilled water and made to 50 g/l.

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The solution was then stirred for 30 minutes using a magnetic stirrer, and finally filtrated through a Whatman filter no 40.

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Raw water was obtained from River Ndarugu.

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The water sample gave an initial turbidity of 83.4 NTU.

JAR TESTS 

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The tests were carried out at The National Water Corporation Laboratory using Janke & Kunkel jar test apparatus with 6 beakers. Turbidity: Turbidity was measured using a 2100P turbidity meter. After the sedimentation phase, samples for turbidity measurement were collected from the supernatant using a standard pipette. Other measured parameters were: temperature, and pH.

RESULTS AND DISCUSSIONS 

The various coagulants used reduced turbidity and were capable of forming flocs in turbid water.

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The flocs formed indicated that powder obtained from various seeds possess adequate coagulation capacity.

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The dosses added for the corresponding six beakers ranged from 0 mg/l to 25 mg/l.

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The initial temperature of raw water was 22.5 ℃ and the pH was 7.5.

RESULTS USING SOYA BEANS EXTRACT 

Turbidity reduced to 83.4, 33.9, 19.8, 16.4, 16.4, and 16.4 corresponding to 0, 5, 10, 15, 20, and 25 mg/l Glycine max doses respectively.

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Soya beans powder was found to be most

effective for coagulation when the dose was 15 mg/l at a mixing rate of 65 revolutions per minute

(RPM) and a settling time of thirty minutes.

Coagulation results using Soya beans extract

Results using Cowpeas (Vigna unguiculata)



For cowpeas, doses of 0, 5, 10, 15, 20, and 25 mg/l reduced turbidity to 83.4, 54.7, 40.1, 31.2,

28.6, and 28.6 respectively, after dosing. 

Turbidity reduction increased with increase in

dosage up to the optimum point of 28.6 NTU.

Coagulation results using Cowpeas extract

Results using Ordinary Beans (Phaseolus vulgaris) 

Turbidity reduced to 83.4, 39.7, 23.5, 18.8, 19.3, and 21.7 corresponding to 0, 5, 10, 15, 20, and 25 mg/l doses of ordinary beans powder.

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The results obtained were used to plot the graph below.

Coagulation results using Ordinary beans extract

Results using Aluminum Sulphate (alum) 

Turbidity reduced to 83.4, 20.3, 2.6, 1.2, 2.8, and 3.8 NTU corresponding to 0, 5, 10, 15, 20, and 25 mg/l

aluminum sulphate doses. 

Alum coagulant was found to have an effect on the final pH of the water.

Coagulation results using Alum extract

CONCLUSION AND RECOMMENDATIONS

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Most of the results obtained using the natural coagulants complied with the WHO guidelines.

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Increasing dosage of the various seed coagulants led to reduction in turbidity up to the optimum dose after which the residual turbidity increased due to floc restabilization.

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The results obtained show that powder from seed kernels of soya beans, cowpeas, and ordinary beans contains some coagulating properties at loading doses of 5mg/L and above that have similar effect as the conventional coagulant, alum.

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Considering the fact that soya beans, cowpeas, and ordinary beans coagulants can be locally produced, their use in water purification should be encouraged.

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Use of natural coagulants is likely to reduce the high cost of the current water treatment systems in Kenya and other developing nations.

RECOMMENDATIONS 

Following the findings from the research, it is recommended that:

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Use raw water from different surface sources with varying levels of turbidity to find out the effectiveness of the natural coagulants on removal of low and high levels of turbidity.

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The natural coagulants powder should be blended in different proportions to find out their

effectiveness in the removal of turbidity from raw water. 

Cost-benefit analysis to be conducted to establish which type of natural coagulant is more economical for the removal of turbidity in raw turbid water.

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Improve the natural coagulants through isolation of bioactive constituents from the seeds to determine if there is an increase in the turbidity removal efficiency.