20620130101003

Journal of Civil Engineering and Technology (JCIET), ISSN 2347 –4203 (Print),
ISSN 2347 –4211 (Online) Volume 1, Issue 1, July-December (2013), © IAEME
26
A COMPARATIVE STUDY OF NATURAL COAGULANTS IN
FLOCCULATION OF LOCAL CLAY SUSPENSIONS OF VARIED
TURBIDITIES
Madhukar V. Jadhava
* Yogesh S. Mahajanb
a
Civil Engineering Department, Sanjivani Rural Education Society’s College of Engineering,
Kopargaon 423603, Maharashtra, India
b
Chemical Engineering Department, Dr. Babasaheb Ambedkar Technological University,
Lonere 402123, Tal-Mangaon, Raigad, Maharashtra, India
ABSTRACT
In the present study, experiments were carried out in the laboratory to investigate the
flocculation behavior of plant origin coagulants Nirmali seeds, Okara gum and the mucilage
isolated from the fruits of Coccinia indica (Kundru) as flocculent for the treatment of
synthetic turbid water. A series of experiments were performed on high (314.4 NTU),
medium (146.8 NTU) and low (34.2 NTU) turbid water with varying dosage of coagulants.
Effect of pH on flocculation efficiency of three coagulants has also been investigated. The
result showed that C. indica, Okara gum and Nirmali seeds have significant flocculation
properties. Flocculation was very rapid in pH range of 6.5 to 8.0. The performance of
Coccinia indica was found to better than other two, with turbidity removal efficiency of
99.3%. The coagulation activity has enhanced with concept of coagulation aid. All three
coagulants have performed better for high turbid water. There was minor change in pH of
treated water with these plant derived natural coagulants. Quality of sludge produced with
natural coagulants was observed to be thick and settles at more rapidly than sludge of
conventional coagulants.
Keywords: Coccinia indica, okara, nirmali seed, mucilage, coagulation, flocculation, dosage,
turbidity
1. INTRODUCTION
Water is considered as a national resource of the utmost importance. Water is vital to
ensure the population’s well- being and quality of life and to preserve the productivity of the
JOURNAL OF CIVIL ENGINEERING AND TECHNOLOGY
(JCIET)
ISSN 2347 –4203 (Print)
ISSN 2347 –4211 (Online)
Volume 1, Issue 1, July-December (2013), pp. 26-39
© IAEME: www.iaeme.com/jciet.asp
JCIET
© IAEME

27
agricultural sector. The increase in water demand for domestic uses, caused by population
growth and by the rising standard of living, together with progressive environmental
pollution problems have led to over-utilization of renewable drinking water sources and the
diminution of water quality. Many countries and, especially large cities facing with a water
scarcity problem. In order to meet the increasing water requirements for urban areas and for
the adjustment industries, water supply reservoirs have usually been constructed especially
for large cities. The quality of river or reservoir water is commonly characterized by the
content of suspended solids (SS), colloidal particles, natural organic matter (NOM) and other
soluble, mostly inorganic compounds, present in different concentrations. Therefore, when
the river or reservoir water is intended for human consumption, an appropriate treatment
process is usually considered as necessary to meet the respective drinking water standards.
One of the most important steps during the conventional treatment process is
coagulation/flocculation, which serves mainly for the removal of SS (including colloidal
micro particles) and NOM (Huang C and Pan J, 2002). Nearly all the colloidal impurities in
natural waters are negatively charged and, hence, these systems may be stable as a result of
mutual electrical repulsions (Duan J and Gregory J, 2003). According to the coagulation and
flocculation theory, colloidal destabilization can be achieved by adding cations that interact
specifically with the negative colloids and reduce (or neutralize) their charge (Peavey Rowe).
Alum is the most widely used coagulant in water treatment because of its proven performance
and cost effectiveness. The use of alum as a coagulant in the treatment of water increases the
aluminium concentration in treated water (Miller, 1984, Schintu M, 2000 & Gauthier,
2000).A high concentration of aluminium is also of concern because of its adverse effects on
health. Aluminium intake into the body has been linked with several neuropath logical
diseases including percentile dementia and Alzheimer’s disease (Craper D R, 1973, Pitchai,
1992 and Jadhav, 2011).
A polyelectrolyte in concurrence with a metal coagulant improves coagulation by
accelerating the process of coagulation. The coagulant aid reduces the necessity of alum and
improves the physical characteristics of flocs. Most of the naturally occurring
polyelectrolytes are of plant origin and the coagulants are derived from the seeds, leaves,
pieces of bark or sap, roots and fruit extracts of trees and plants. Many of the researchers
from the world have done their studies on various natural plant derived coagulants and
flocculants.(Bhole,1990 & 1995, Megat M.,2002, Diaz A.1999, Yarahmadi M. 2009 , Zhang
J. 2006, Mishra A. 2004 & 2005, Konstantinos A. 2009, Babu R. 2005, Patale Varsha
2010).The natural macromolecular compounds derived from cactus species and low cost
anionic polysaccharide and the polyelectrolyte derived from Strychnos potatorum are capable
of reducing turbidity of water through flocculation process (Singh 2003).Natural coagulants
of plant origin have been used for water purification for many centuries. Strychnos potatorum
(Nirmali seeds) was used as a clarifier between the 14th and 15th centuries BC. Shultz and
Okun together with Sanghi et al., reported that seeds of the Nirmali tree were used to clarify
turbid river water about 4000 years ago in India.
Studies on the performance of natural coagulants derived from plants such as nirmali
seeds, tamarind tree, guar plant, red sorella plant, fenugreek and lentils have been conducted
using raw water with turbidity ranged from 50 to 7500 NTU. The optimum dosage for the
nirmali extract was 50 mg/l, which produced a 76% reduction in turbidity. The effective dose
for the other plant coagulants extracts ranged from 2 mg/ l to 20 mg/l at pH levels from 4 to
9, and proved to be more economical for turbidity values greater than 300 NTU (Shultz and
Okun, 1984).

28
Moringa oleifera powder has been reported to have the capability of reducing low and high
turbidity values in surface water(Madsen et al., 1987; 1995; Muyibi and Okuofu, 1995,
Muyibi and Meget 2002, Muyabi and Abbs 2003, Muyabi & Alfugara 2003, Bhatia 2006 &
Chaudari 2009). Moringa oleifera was used as a natural coagulant in a full-scale treatment
trial at the water treatment works in Malawi. Turbidity values as high as 270–380 NTU were
reduced to around four NTU, which are within the WHO (2006) guideline value with the
addition of the powder (Sutherland et al., 1994).
Gholamreza Nabi Bidhendi et al., showed that Plantago ovata extract is less efficient
in high turbidities when used as a coagulant aid. Plantago ovata, as a coagulant aid, showed
positive influence on turbidity removal from water. In addition, optimized pH showed
important role in reducing turbidity. Agarwal M. et al. used okra gum for treatment of tannery
effluent , they found that okra gum acts as a very effective flocculent, capable of removing
more than 95 percent suspended solid and 69 percent dissolved solid from the effluent. Rajani
Srinivasan et al., have done research on okra (Hibiscus esculentus) and fenugreek (Trigonella
foenum graceum )mucilage for flocculation of textile effluent. Results showed that
polysaccharides (mucilage) obtained from okra and fenugreek was capable of removing
90%−94% of suspended solids, 30%−44% of total dissolved solids. Mishra et al. carried out
their work on Plantago psyllium mucilage for sewage and tannery effluent treatment. The
maximum solid removal (94.69 %) was seen only after 1 h with the suitable pH range. Study
by Zhang J. Y. et al. on the performance of cactus as a coagulant in water treatment indicates
that the coagulation performance of cactus was very much effective for turbidity removal;
residual turbidity of less than 5NTU could be obtained with initial turbidities from 20 to 200
NTU.
Natural coagulants have been reported to have several other advantages compared to
synthetic coagulants such as alum and ferric chloride, in that, they produce much lower
sludge volume and are safe to humans. Ghebremichael (2004) investigated that the sludge
produced from Moringa oleifera coagulated turbid water is only 20–30% that of alum.
Litherland, Katayon et al., and Sanghi et al., showed that the residue of alum in water may be
carcinogenic. Natural coagulants are biodegradable and cost effective for developing
countries since they can be locally grown and have a wider effective dosage range for
flocculation of various colloidal suspensions (Sanghi et al., 2006).
The objective of the present study is to investigate the coagulation-flocculation potential of
coagulants derived from plants, such as nirmali seeds, okara mucilage and Coccinia indica
mucilage, to remove the turbidity from synthetic turbid water prepared from local clays and
to determine the optimal dosages.
2. MATERIALS AND METHODS
The materials used in this study are seeds of S. potatorum (Nirmali seeds), Cactus
opuntia pads and fruits of Coccinia indica. The seeds of S. potatorum were purchased from
an ayurvedic medical shop of Nashik city, the Cactus opuntia pads were collected from a
nursery at Bhagur, Nashik and Coccinia indica fruits were purchased from vegetable market
Nashik. The preparation of coagulant powders and turbid water is elucidated below.
2.1 Preparation of turbid water
Locally available natural clay was used to prepare synthetic turbid water by soaking
the clay for 24 hours in tap water and then blending it for 10 min. The suspension was

29
washed through a 75- micron sieve. This was kept as a stock suspension for preparation of
different turbidities such as low, medium and high. A portion of the stock suspension was
diluted with tap water and after 30min of settling in a container, the supernatant was carefully
decanted and desired turbidities of 34.2 NTU (low), 146.8 NTU (medium) and 314.4 NTU
(high) were obtained by diluting it (Pramod Kumar Raghuwanshi , 2002).
Sedimentation analysis of the suspension was done. Particle size distribution results are as:
73% of particles were finer than 8.6 µm, 26% of particles were finer than 1.4 µm, 19% of
particles were finer than 1.25 µm, 13 % of particles were finer than 0.72 µm, and 9% of
particles were finer than 0.62 µm. Chemical characteristics of the tap water used to prepare
the synthetic turbid water are shown in Table 1.
Table 1. Composition of the tap water used to make synthetic turbid water
_______________________________________
Parameter Concentration
_______________________________________
pH 7.0-7.5
Turbidity 0.2 NTU
Alkalinity (as CaCO3) 247 mg/l
Total hardness (as CaCO3) 188 mg/l
Potassium (K+
) 5 mg/l
Sodium (Na+) 23 mg/l
Chlorides (Cl-) 103 mg/l
Calcium (Ca++) 34.6 mg/l
Sulphates (SO4 --) 8.7 mg/l
_______________________________________
2.2 Preparation of nirmali seed powder
Nirmali seeds were powdered and sieved through 150µm sieve, and a 2% suspension
was prepared with distilled water. These seeds due to their hard structure, could not be
powdered in a grinder. In such a case the seeds were kept immersed in 50 ml water
containing 2ml conc. HCl. After a week, the mixture was mashed to a soup-like solution, and
was washed through a nylon cloth and the material retained on the cloth was oven dried for
24 hours at 103°C to 105°C and weighed. By calculating the weight of the seeds dissolved,
the strength of the stock solution was determined (Bhole 1990, 1995).
2.3 Preparation of Okara mucilage
The raw material, seedpods of Okara was bought from local market. It was initially
washed thoroughly with water to remove any impurities, dried at 100oC for 6- 8 hours. The
okra gum was obtained by aqueous extraction of the seedpods of okra plant followed by
precipitation with alcohol. It is a white amorphous polysaccharide consisting largely of d-
galactose, l-rhamnose and lgalacturonic acid. The precipitated polysaccharide was then
washed with acetone 2 to 3 times to remove impurities and finally dried (Rajani
Srinivasan,2008 and Agarwal M.,2001).
2.4 Preparation of Coccinia indica powder
Coccinia indica ripped fruits purchased from the market are thoroughly washed with
water, cut into small pieces and soaked in distilled water overnight. The mucilaginous extract

30
was filtered through muslin cloth. Alcohol was added to precipitate the extract. The
precipitate was then washed with acetone 2-3 times and then dried by keeping in an oven at
the temperature of 40°C for 24 hours. The filtered extract was then used in the experiment
(Varsha Patale and Parikh Punita., 2010).
2.5 Preparation of alum solution
Alum solution was prepared from aluminium sulphate, stock solutions were prepared
according to the USEPA procedure for enhanced coagulation (USEPA, 1999), dissolving 10g
aluminium sulfate (Al2 (SO4)3.18H2O) in distilled water and the solution was made to one
litre. One ml of this stock solution gives concentration of 10 mg/l.
2.6 Experimental work
Sedimentation Jar test were carried to determine the coagulation properties of the
plant derived coagulants. One beaker was used as control and in other beakers varying dosage
of coagulants was added. Jar tests were conducted on 500 ml synthetic turbid water samples.
Following the addition of the coagulants dosages (Alum, Nirmali powder, Okara gum, and C.
indica.), the samples were subjected to a rapid mixing at 100 rpm for 1 minute, and a slow
mixing step at 30 rpm for 30 min., The stirrer was then switched off and the floc allowed to
settle undisturbed (ASTM 1995) for 30 minutes. The samples for residual turbidity
measurement were withdrawn using a pipette from a height of 5cm below the surface of each
beaker, and residual turbidity was measured. Effect of combined dose of natural coagulants
and alum on removal of turbidity that is natural coagulants as a coagulant aid also studied.
The effect of pH on turbidity removal was also studied by varying pH of turbid water. pH of
the suspension was adjusted to the desired value by adding either 0.1 M HCl solution or 0.1M
NaOH solution.
Turbidity measurement was carried out by Systronics Turbidity meter type 131,
Systronics, India. pH value of the suspension was measured using a Elico digital pH meter
model 121 . The chemical analyses were conducted as per Standard Methods (APHA 2005).
The procedure conformed to that described in Standard Methods for the Examination of
Water and Wastewater.
3.0 RESULT AND DISCUSSION
3.1 Determination of optimum dose of alum
Results on optimization of alum dosage for low, medium and high turbid water were
shown in figure 1. Optimum dose of alum for synthetic turbid waters of low (34.2 NTU),
medium (146.4 NTU) and high (314.4NTU) initial turbidity were 20, 20 and 30 mg/l
respectively. Above this dosage, the suspensions showed a tendency to restabilise. The lowest
dose with maximal efficiency was found to be 30 mg/l in high turbidity. In the study, it was
observed that irrespective of initial turbidity, application of 20-40 mg/l of alum leaves a
residual turbidity less than 5 NTU (Fig. 1). WHO recommends that if water turbidity is more
than 5 NTU, then some treatment to remove turbidity is needed before the water can be
efficiently disinfected with chlorine.

31
Fig.1. Plot of Alum dose verses residual turbidity
3.2 Effect of pH on the flocculation of synthetic turbid water
To study the effect of pH, tests were conducted on medium turbid water with pH
varying from 4.0 to 9.0 in the present study. Dosage of nirmali seed, okara mucilage and C.
indica were 2.0 mg/l, 2.0mg/l and 0.4 mg/l respectively. Figure 2 represents the details of
results. Based on this figure, it was seen that all the natural coagulants produces appreciable
reduction of turbidity only between pH 6.5-7.5. Results of this study are very much
comparable to the results of Bina B. et al., and Yang Y. C. et al.
Fig. 2. Plot of Effect of pH value on Turbidity Removal.
3.3 Optimum dose of natural coagulants
Results of coagulant test using varying dosage of natural coagulant such as N.S.
(nirmali seed, okara mucilage and C. indica are presented in figures 3 (a, b, and c).
From figure 3a, optimum dose of nirmali coagulant is 1.0, 2.0 and 2.0 mg/l with residual
turbidities of 8.5, 27.6 and 27.6 NTU for low, medium and high turbid water. From figure
3b, optimum dose of okara mucilage coagulant is 1.0, 2.0 and 2.0 mg/l with residual
turbidities of 7.4, 19.8 and 8.8 NTU for low, medium and high turbid water. Moreover, figure
3c represents, optimum dose of C. indica mucilage is 0.4, 0.4 and 0.6 mg/l with residual
turbidities of 5.7, 8.2 and 6.9 NTU for low, medium and high turbid water. It was seen that
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60
ResidualTurbidity,NTU
Alum Dose,mg/l
Low Turbidity
Medium Turbidity
High Turbidity
0
10
20
30
40
50
60
70
80
3 4 5 6 7 8 9 10
pH Value
Okara mucilage
Nirmali Seeds
Coccina Indica

32
pH of water after addition of alum dose decreased from 7.2 to 5.6, meaning that chemicals
need to be added to raise the pH of water to meet the permissible limit (WHO2006). However
with addition of natural coagulants there was minute change in pH of treated water, not
necessity of pH correction .This trend is in agreement with the research carried by Ng et al.,
(2006)..
a)
b)
c)
Fig. 3. Performance of a) Nirmali seed b) Okara mucilage and c) C. indica coagulant at
varying dosage
0
20
40
60
80
100
120
140
160
180
0 1 2 3 4 5 6
Dose of N.S .Coagulant , mg/l
Low turbidity
Medium Turbidity
High Turbidity
0
10
20
30
40
50
60
0 2 4 6
Dose of Okara Mucilage, mg/l
Low Turbidity
Medium Turbidity
High Turbidity
0
5
10
15
20
25
30
35
40
0 0.5 1 1.5
Dose of C. Indica ,mg/l
Low Turbidity
Medium Turbidity
High Turbidity

33
3.4 Optimization of natural coagulants as coagulant aid in combination with alum
In order to decrease residual aluminium concentration in treated water, and possible
adverse effects of aluminum in drinking water on human health, Nirmali seeds powder, okara
mucilage and C. indica mucilage were used as coagulant aid in conjunction with alum. The
performances of above natural coagulants in different turbidities were presented in Figure 4
(a, b and c).
a)
b)
c)
Fig. 4. Performance of a) Nirmali b) Okara mucilage and c) C. indica as a coagulant aid with
alum
0
10
20
30
40
50
0 0.5 1 1.5 2 2.5 3
Doses of N.S.+ Alum ,mg/l
Low Turbidity
Medium Turbidity
5 5 5 5 5 5
0
5
10
15
20
25
30
35
0 0.5 1 1.5 2 2.5 3
Dose of Okara + Alum , mg/l
Low Turbidity
Medium Turbidity
High Turbidity
5 5 5 5 5 5
0
5
10
15
20
25
30
35
40
0 0.1 0.2 0.3 0.4 0.5 0.6
Dose of C. indica + Alum , mg/l
Low Turbidity
Medium Turbidity
High Turbidity
5 5 5 5 5 5

34
Initially, the optimum doses of alum were determined for low, medium and high
turbid water at pH 7. To study the effect of coagulant aid, one fourth quantities of optimum
doses of alum and varying quantities of natural coagulants as a coagulant aid were used to
determine the optimum doses of coagulant aids (Mahmut, 2003, Mohammad Hadi
Mehdinejad, 2009). It is seen from figure 4a, optimum dose for nirmali seed as a coagulant
aid is 1.0 mg/l with residual turbidities of 8.5, 27.6 and 27.6 NTU for low, medium and high
turbid water. From figure 4b it has seen that, optimum dose of okara mucilage as a coagulant
aid are 1.0, 1.5 and 1.5 mg/l with residual turbidities of 4.5, 8.2 and 6.9 NTU. While from
figure 4c, optimum dose of C. indica mucilage are 0.2, 0.3 and 0.3 mg/l with residual
turbidities of 4.0, 4.0 and 3.8 NTU for low, medium and high turbid water.
3.5 Performance of selected natural coagulants
To remove the turbidity from low turbid water (34.2NTU) prepared from local clay,
C. indica produced the best results, with percentage reduction in turbidity of 81.2 %. .Okara
mucilage ranked second with percentage reduction of 78.2%. , while Nirmali seed coagulant
has removed 75.0% turbidity (fig.3). In terms of acceptable guideline values the World
Health Organization (2006) publishes that for drinking water the turbidity should be less than
5 NTU. From Figure 3, it was observed that none of the residual turbidity has attained the
guideline value of WHO (5NTU).
Hence further study was performed using the concept of coagulant aid. Figure 4
represents the performance of selected natural coagulants as a coagulant aid.
With ¼ of optimum dose of alum and nearly ½ of optimum dose of natural coagulants, C.
indica has attained percentage reduction in turbidity of 88.4%, okara mucilage achieve
reduction of 86.8% and nirmali seed coagulant removed 84.2% turbidity from low turbid
water.
For medium turbid water (146.8 NTU), C. indica produced reduction of 90.0%, okara
mucilage achieves 86.5% reduction, while, nirmali seed coagulant removed 81.2% turbidity.
Experiments with technique of coagulant aid improved the results, with increase in
percentage removal from 90 to 97.3% for C. indica, 86.5 to 94.4% for okara and 81.2 to
92.8% for nirmali coagulant. Residual turbidities were 10.5, 8.2 and 4.0 NTU, only C. indica
give residual turbidity within permissible limit.
Therefore, further study is necessary by passing the turbid water through slow
sand/rapid sand filter to achieve residual turbidity well within safe guideline.
For high turbid water 314.4 NTU turbidity, C. indica produced percentage reduction of
92.8% , okara mucilage has achieved 90.2% reduction, while, nirmali seed coagulant
removed 88.2% turbidity.
Coagulant aid technique improved removal efficiency better for C. indica and okara
mucilage. C. indica produced reduction of 99.3%, okara mucilage has attained reduction of
98.7%, while, nirmali seed coagulant removed 96.7% turbidity. Residual turbidities for C.
indica and okara are well within permissible limit of WHO.
Investigation on use of mallom mucilage and okara for treatment of synthetic
wastewater and effluent was carried by Konstantinos et al. (2009). With dosage of 12-26 mg/l
of mallon, there was 96.3- 97.7 % reduction in turbidity for synthetic waste water and 61-66
% reduction in turbidity for effluent. For okara with optimum dose of 5mg/l there was 93.0 -
97.3 % reduction in turbidity for synthetic wastewater and 70- 72 % reduction in turbidity for
effluent. These results are very much comparable with the results of this study.

35
To purify water relatively of high initial turbidity (Kumponda, shallow well water in
Malawi), Pritchard M. et al., (2005) utilized guar gum, J. Curcas and M. oleifera for
purification. With dose of 250 mg/l of M.O. there was 96% reduction in turbidity the
optimum dose of gaur Gum was 50mg/l, which reduces 95% turbidity and J. Curcas reduces
92% turbidity with optimum dose of 50mg/l, higher decline efficiency for high turbid water.
Same trend of result for this study as well.
Research on nirmali seed powder in coagulation-flocculation of turbid synthetic water
prepared from Kaolin with varying coagulant dose and pH on removal of turbidity was
investigated by Babu R. et al., (2005). For optimum dose of 1.5 mg/l of nirmali seed
coagulant there was 90% reduction in turbidity. pH of treated water was unaffected by
addition of coagulant dose .Results of research furnished in this paper, on natural coagulants
nirmali seeds, okara and coccinia indica are in agreement with the results of other
researchers.
One of the important parameters that have been considered to determine the optimum
condition for the performance of natural coagulants in coagulation and flocculation is dosage.
Several researchers were reported that during the initial stages with the increase in the
dosage, the percentage turbidity removal increases, but after the optimal dose, there is a
decrease in the removal efficiency (figure 3). The behavior could be explained by the fact that
the optimal dosage of flocculent in suspension causes larger amount of solids to aggregate
and settle. However further increase in the dosage of coagulant would cause the aggregated
particle to redisperse in the suspension and would also disturb particle settling. Table 2
compares the results obtained in this study to those obtained in other studies where natural or
chemical coagulants were used. Compared to other coagulants C. indica has performed better.
The results obtained by this study exhibited that natural coagulant of plant origin can be
effectively utilized in water and wastewater treatment. However, many of the studies
reported, in literature carried under controlled laboratory scale models and conditions.
Table 2: Comparison of coagulation efficiency of selected coagulant and chemical in a
variety of water
______________________________________________________________________________
Reference Type of water or w/w Type of Coagulant Optimum dose mg/l % reduction in
Turbidity
_________________________________________________________________________________________
This work Synthetic turbid Nirmali seed 2.0 75.0 - 88.2
water with local clay Okara mucilage 1, 2, 3 for L, M, H 78.2 - 90.2
C. Indica 0.4 81.2 - 92.8
N.S. + alum 1+5 84.2 - 96.7
Okara+ alum 1.5 + 5 86.8 - 98.7
C. Indica + alum 0.2 + 5 88.4 - 99.3
[05] Kaolin turbid water Nirmali seed 1.5 90.0
[38] Natural clay Nirmali seed 3+ 20 alum 99.0
[46] Kaolin turbid water C. Indica 0.4 94.0
[20] w/w & synthetic Okara 5 93- 97.3
[50] Estuarine & river water Cactus op. 13 49.2-98.2
[35] Surface water MO+ Alum (60+41) % 98.99
______________________________________________________________________________

36
4. CONCLUSIONS
From a plant extract record and laboratory analysis, natural coagulants derived from
plants such as, nirmali seed, okara and Coccinia indica have been identified to be
suitable for treating turbid water either as a sole coagulant or in combination with
alum as a coagulant aid.
A large reduction in turbidity is achieved at optimal dosage conditions. All the three
coagulants have performed better for high turbid water.
With addition of natural coagulants dosage, there has been found minor change in pH
of treated water but not necessity of pH correction. Quality of sludge with natural
coagulants observed to be thick and settles at more rapidly than sludge with
conventional coagulants.
WHO and IS1500 guideline value for residual turbidity has achieved with a plant
extract dose as a coagulant aid.
With reducing optimum dose of alum to 1/4 and optimum dose of natural coagulant to
1/2, there is rise of 10 to 15 % in turbidity removal efficiency for all the three natural
coagulants for turbidity levels of low, medium and high.
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