1. INTRODUCTION
Growing population, increased economic activity and industrialization have not only created an increased demand for fresh water but also resulted in severe misuse of natural resource. Water resources all over the world are threatened not only by over exploitation and poor management but also by ecological degradation. According to a survey conducted by United Nation Environment Programme (UNEP), 20% of world’s population lacks access to safe drinking water and 50% lacks access to safe sanitation. Polluted water is estimated to affect the health of about 1200 million people and contributes to the death of 15 million children (per year) under the age of five [1].
The use of plant materials as natural coagulants to clarify turbidity of water is common practice since ancient times. Seeds of Strychnos potatorum (S. potatorum) and Moringa oleifera (M. oleifera) have shown promising result as the source of natural coagulant in the clarification of turbid water [2-4]. Direct filtration with S. potatorum seeds as coagulant appeared effective in clarifying turbid water [5]. This property is attributed due to the presence of polyelectrolytes, proteins, lipids, carbohydrates and alkaloids containing the -COOH and free -OH surface groups in the seed [6]. Among all plant materials investigated, seeds of M. oleifera were found to be one of the most effective sources of primary coagulant for water treatment [3].
T. foenum-graecum (Fenugreek) belongs to the family Leguminosae that grows predominantly in Asia, Northern Africa and the Middle East. Fenugreek seed contains 23% - 26% protein, 6% - 7% fat and 58% carbohydrates of which 25% is dietary fiber, saponins [7] and rich in flavonoids. Fenugreek has been widely used as a flavoring agent and in folk medicine. Several beneficial effects, such as appetite stimulation [8], anti-inflammatory, antipyretic [9], antimicrobial [10], antioxidant, antidiabetic [11], anticancer [12] and antiatherogenic properties [13] have been reported. C. cyminum, an aromatic plant from the family Umbelliferae is used as a flavoring and seasoning agent in foods [14,15]. To our knowledge no studies have been carried out to find out, whether seeds of T. foenum-graecum and C. cyminum can serve as water coagulant. Hence, this study was ventured to investigate the applicability of natural coagulants extracted from seeds of above plants that are abundantly available in Asia.
2. MATERIALS AND METHODS
2.1. Preparation of Seed Extracts and Collection of Turbid Water
Seeds of T. foenum-graecum, C. cyminum, M. oleifera and S. potatorum were collected locally near the city of Puducherry, India. The whole seeds of T. foenum-graecum, and C. cyminum were ground to fine powder using a laboratory mill. All ground materials were sieved through 0.4 mm membrane sieve and the fraction with particle size less than 0.4 mm was used in experiments. 10 g of prepared powder was suspended in 1 L of distilled water or NaCl (0.5 M and 1.0 M) solution and the suspension was stirred using a magnetic stirrer for 10 min to extract the coagulation active components. The seeds of M. oleifera and S. potatorum were made into fine pieces and soaked in water or NaCl for 1 hr, grinded in mortar and pestle, 1% suspension of S. potatorum and 5% suspension of M. oleifera were made with distilled water [3,4] or 1.0 M NaCl solution [2,16,17]. The suspension was then gravity filtered through a rugged filter paper. The filtered solutions, called extracts, were kept in refrigerator at 4˚C.
Water was collected from pond (stagnant rain water in red soil) near Pondicherry University, Puducherry, India, in the month of February 2010. The turbid pond water was left undisturbed for 48 hr to check for any initial spontaneous particle settlement. But the turbidity of the water did not change with increase in time.
2.2. Coagulation Test
Coagulation efficiency of each seed extract was determined by the jar test. The pond water (300 ml) was filled into the beakers (600 ml) and mixed at 200 rpm at constant room temperature (25˚C). Various doses of seed extracts were added into the beakers and mixed for 1 min. The mixing speed was then reduced to 80 rpm and kept for another 30 min. Then the suspensions were left for sedimentation. After 1 hr, 3 hr, 6 hr, 12 hr and 24 hr of sedimentation, clarified samples were collected from the top of the beakers, and turbidity was measured as TS (Turbidity of Sample). The turbidity in the control was defined as TB (Turbidity of Blank). Turbidity was measured using a turbidimeter (TURB 550 IR) and it was expressed in nephelometric turbidity units (NTU). Coagulation efficiency was calculated as:
Coagulation efficiency (%) = (TB – TS) × 100/TB
Each experiment was performed as triplicates and the same was repeated three times. The values are expressed as mean ± S.D.
2.3. Analytical Analysis
The phytochemical analysis of the seed extract of T. foenum-graecum and C. cyminum were done as described by Trease et al. [18]. Protein concentration in crude extracts was measured by Lowry et al. [19]. The quality parameters of the different water were determined using standard methods [20]. Organic matter concentration in water after coagulation was determined as KMnO4 demand by Kübel-Tiemann [21]. Each experiment was carried out in triplicates and experiment was repeated thrice.
3. RESULTS AND DISCUSSION
3.1. Characteristics of Natural Coagulant
Water extract of T. foenum-graecum and C. cyminum samples were screened for the presence of phytochemical compounds (Table 1). As expected, two plant species (used for the present study) showed the presence of various phytochemicals. Plant sterol and steroid presence was observed in T. foenum-graecum, which was absent in C. cyminum. The coagulating active agents can be extracted from seeds by water, different salt solutions, buffer solutions or organic solvents [4,22,23]. Numerous researchers reported that proteins are the active coagulating components in plant extracts [22,24]. Ndabigengesere et al. [4] reported that the coagulation active agents in the seed extract of M. oleifera are dimeric cationic proteins. However Okuda et al. [25] and Sanghi et al. [26] suggested that the coagulation active agent in the extract of M. oleifera was neither a protein, nor a polysaccharide, nor a lipid, but an organic polyelectrolyte.
In the present study protein concentrations in extracts
Table 1. Phytochemical screening of seed extracts of T. foenum-graecum and C. cyminum.
of the different samples were determined. The efficiency of protein extraction from seeds of T. foenum-graecum and C. cyminum by distilled water, 0.5 M or 1 M NaCl solutions was done (Figure 1). Results showed the water extracts obtained from different samples has the highest values of protein concentration compared to 0.5 M and 1.0 M NaCl extracts. Water extract of T. foenum-graecum showed the highest (2.14 mg/ml) concentration of protein. The coagulating active agents were extracted by distilled water and two different salt concentrations (0.5 M and 1.0 M NaCl). 1.0 M NaCl extract of T. foenum-graecum showed highest coagulation efficiency (~81%) compared to 0.5 M NaCl (~25%) and water (~8%) extracts on pond water (Figure 2). C. cyminum also showed highest coagulation efficiency in 1.0 M NaCl extract (~16%). This coagulation efficiency of C. cyminum was negligible compared to that of T. foenum-graecum and hence the latter was used for further studies.
Figure 3 shows the coagulation efficiency of T. foenum-graecum along with 3 standard natural coagulants and 1 synthetic coagulant used in the study. The coagulation efficiency was maximum for synthetic coagulant Al2 (SO4)3 followed by S. potatorum, T. foenum-graecum and M. oleifera seed extracts. To verify that coagulation active components contributed to the coagulation efficiency, the authors performed coagulation test with NaCl alone (no added extracts). No significant changes were observed in the turbidity levels of control pond water and NaCl alone treated pond water (data not shown) even after 48 hr. This observation suggests the presence of coagulation active compounds in the seed extract of T. foenum-graecum, which is responsible for the coagulation of turbid pond water and not by other mechanisms [25].