Removal of turbidity from drinking water using natural coagulants

https://doi.org/10.1016/j.jiec.2013.08.023Get rights and content

Abstract

The ability of three plant materials, seeds such as Moringa oleifera, Strychnos potatorum and Phaseolus vulgaris, to act as natural coagulants was tested using synthetic turbid water formulated to resemble the drinking water. An improved and alternative method for the extraction of the active coagulant agent M. oleifera, S. potatorum, P. vulgaris seeds was developed and compared with the conventional water extraction method. In the new method the seeds were extracted using different solvents of NaCl and NaOH to extract the active coagulant agent from natural coagulants. In addition, ultrasound was investigated as a potential method to assist the extraction process. Batch coagulation experiments were conducted to evaluate the performance of the extracted coagulant achieved through various schemes. The optimum turbidity removal at different values of initial synthetic wastewater turbidity from 100 to 500 NTU was investigated. Sodium chloride at 0.5 M was found to provide a high turbidity removal of >99% compared to NaOH and distilled water extract. Among these three coagulant M. oleifera seed extracts is the highest performance in turbidity removal. The optimum coagulant dosage showed the coagulation with blended coagulant M. oleifera, S. potatorum and P. vulgaris. The study was carried out for initial turbidity of the sample such as 100 NTU (low), 250 NTU (medium) and 500 NTU (high). For the natural coagulant dosage was found to be 250–1000 mg/L respectively. It was found that the percentage of removal is highest in M. oleifera.

Introduction

A great problem in many developing countries is to get clean drinking water at low price. This can be normally solved by adding chemical coagulants such as aluminum sulfate which is generally at a high cost. The application of a coagulation/flocculation process is applied in water, wastewater treatment to remove turbidity, color and natural organic matter [1], [2]. Inorganic coagulants such as aluminum sulfate, ferric chloride and calcium carbonate and synthetic organic polymer (polyaluminium chloride (PACl) polyethylene imine) are common coagulant used in this treatment. However the sludge obtained from treatments using aluminum salts leads to disposal problems such as aluminum accumulation in the environment [3]. Moreover, some studies have reported that residual aluminum sulfate (alum) and polyaluminium chloride may induce Alzhemier's disease [4], [5]. Whereas the synthetic organic polymers, such as acrylamide, have neurotoxic and carcinogenic effects [6]. One possible solution to these problems may be natural coagulants which are preferably alternative excellent method for removal of turbidity from drinking water. These coagulants must be safe for human health and biodegradable.

In recent years, numerous studies on a variety of plant materials which can be used as source of natural coagulants have been reported. For example natural coagulants from Moringa oleifera (drumstick) [7], common bean (Phaseolus vulgaris) [8] and Nirmali seed (Strychnos potatorum) [9], [10] have been investigated. The material that has received the greatest degree of attention is the seed of M. oleifera [11], [12], [13]. M. oleifera seeds contain between 30% and 35% (w/w) of vegetable oil known as Behen (or) Ben oil. M. oleifera (drumstick) treatment due to the presence of water soluble cationic coagulant protein is able to reduce the turbidity of the water treated [14]. The seed extracts of S. potatorum (Nirmali) contain the anionic polyelectrolyte [15]. The crude extracts of common bean (P. vulgaris) seed showed ability to act as a natural coagulant [16].

The common bean seed has a food grade nature and contains no oil [17]. The three agro based seeds M. oleifera (drumstick), S. potatorum (Nirmali), and P. vulgaris (common bean) are non-toxic and effective coagulant aids useful for removing turbidity and bacteria from water. In this study the aim is to improve the coagulant agent from M. oleifera, P. vulgaris and S. potatorum. Since the active coagulant agent in the M. oleifera seed is believed to be a soluble cationic protein [18], [19], [20], it is of interest to investigate coagulant agent extraction using the different type of solvent, such as NaCl, NaOH and water. In addition previous research has also made use of ultrasound treatment in order to improve the extraction method [21]. The advantage of selectivity of natural coagulants used is having antimicrobial properties [22], [23]. The natural coagulants is the low cost method for removal of turbidity from drinking water. In the present study we collected pond water and used various naturally available seeds for removal of turbidity.

Section snippets

Materials

Sulfuric acid (98%), glycerol (95%), hydrochloric acid (35.4%), ethyl alcohol (95%), and silver nitrate (99.5%) were obtained from Merck (India).

Apparatus and measurements

Turbidity was measured using a turbidity meter (ELICO CL 52D NEPHELOMETER) and it was expressed in nephelometric turbidity units (NTU). pH is measured using a pH meter (ELICO LI 120 pH metre). Analytical instrument (ELICO PE 135 DO Analyser) was used to determine the dissolved oxygen. Conductivity meter (ELICO CM 180) was used to measure the water

Physicochemical characteristics of turbidity water given in Table 1

The physicochemical characteristics such as turbidity, alkalinity, hardness, sulfate, chloride and other ions concentration was measured for pond water and given in Table 1.

Effects of using different solvents as the extracting agent of the coagulant from natural seeds

In the determination of best solvent to be used for the extraction of the active coagulant agent from M.O seeds, the effects of M.O 0.5 NaCl and 0.5 M NaOH were compared with M.O distilled water. Fig. 1 shows the turbidity removal of synthetic wastewater using these three types of solvents. At 500 NTU M.O 0.5 M NaCl could

Conclusion

M. oleifera, P. vulgaris and the seeds of S. potatorum significant improvement in removing turbidity from synthetic raw water was found. Maximum turbidity reduction was attained in high turbid water. After dosing NaCl soluble extract of M. oleifera, S. potatorum and P. vulgaris reduced turbidity to 5, 10, 1 NTU respectively from 500 NTU. The natural coagulant NaCl extract is the greatest removal of turbidity compared to NaOH and distilled water.

References (23)

  • M.A. Aboulhassan et al.

    J. Hazard. Mater.

    (2006)
  • G.S. Madrona, G.B. Serpelloni, A.M.S. Vieira, L. Nishi, K.C. Cordeio, R.O. Water Air Soil pollut Bergamasco, 211 (2011)...
  • T. Okuda et al.

    Water Res.

    (1999)
  • S.A. Muyibi et al.

    Int.J.Environ.stud

    (2007)
  • Y.S. Chang et al.

    Chemosphere

    (2009)
  • V.N.S. Pillai et al.

    Water Res.

    (2002)
  • T.P. Flaton

    Brain Res. Bull.

    (2002)
  • C.N. Martyn et al.

    Lancet

    (1989)
  • J. Mallavialle et al.

    J. Am. Water Works Assoc.

    (1987)
  • A.Cr. Liew, M.J.M.M. Noor, S.A. Muyibi, International Journal of Environmental studies 63(2) (2006)...
  • M.G. Antony et al.

    Bioresour. Technol.

    (2010)
    M.G. Antony et al.

    Bioresour. Technol.

    (2010)
  • Cited by (0)

    View full text