184 International Journal of Environment 3(3): 184 -191, 2014 ISSN: 2077-4508

Corresponding Author: Sabah A.Badr, Water Pollution Research Department, National Research Center, Dokki, Giza, Egypt. E-mail: sabahbader@yahoo.com

Effectiveness of Activated Carbon Prepared from Saw Dust as Natural Coagulant Aid for Nile Water Algal Removal Sabah, A. Badr, Mahassen M. Ghazy, Nady A. Fathy and Reda M. Moghazy Water Pollution Research Department, National Research Center, Dokki, Giza,Egypt.

ABSTRACT

According to the excessive growth of phytoplankton, which is commonly seen during the whole years in the River Nile water becomes more problem affecting the conventional technique (prechlorination and alum) used in drinking water treatment plants. This search describes laboratory comparison of conventional technique (perchlorination and alum) used in drinking water treatment plants with modified procedures by using natural flocculent " Moringa oliefera seeds" and activated carbons produced from sawdust as coagulant aid for Nile water algal removal. The results show that, when comparing the efficiency of two chemical coagulants (Alum and ferric chloride) used and natural flocculants “Moringa oliefera" with activated carbons produced from sawdust as coagulant aid (PAC1), the most effective coupling was M. oliefera with PAC1. The results of toxicity tests on treated water using PAClab and PAC1 as coagulant aid with chemical and natural coagulants showed the absence of any toxicity effect on the test organism Daphnia magna.

Key words: Activated carbon, sawdust, modified, technology, water treatment, Moringa oleifera.

Introduction

Coagulation-flocculation followed by sedimentation, filtration and disinfection, often by chlorine, is used worldwide in the water treatment before the distribution of treated water to consumers (Edzwald et al., 1989; Kawamura, 1991a; Degremont, 1989; AWWA, 1990; Desjardins, 1988; 1985). Aluminum salts are by far the most widely used coagulants in water and wastewater treatment (Bratby, 1980). However, recent studies have pointed out several serious drawbacks of using aluminum salts, such as Alzheimer's disease and similar health related problems associated with residual aluminum in treated waters (AWWA, 1990; Miller et al., 1984; Letterman and Driscoll, 1988; Qureshi and Malmberg, 1985), besides production of large sludge volumes (James and O'Melia, 1982). There is also the problem of reaction of alum with natural alkalinity present in the water leading to a reduction of pH (Degremont, 1989), and a low efficiency in coagulation of cold waters (Haarhoff and Cleasby, 1988; Morris and Knocke, 1984). A significant economic factor is that many developing countries can hardly afford the high costs of imported chemicals for water and wastewater treatment (Schultz and Okun, 1983, 1984; Ndabigengesere, 1995).

Ferric salts and synthetic polymers have also been used as coagulants but with limited success, because of the same disadvantages as in the case of aluminum salts (Bratby, 1980; Haarhoff and Cleasby, 1988; Boisvert, 1992; Letterman and Pero, 1990; Goppers and Straub, 1976; Aizawa et al., 1990; Biessinger et al., 1976; Biessinger and Stokes, 1986; Mallevialle et al., 1984). Therefore, it is desirable that other cost effective and more environmentally acceptable alternative coagulants be developed to supplement if not replace alum, ferric salts, and synthetic polymers. In this context, natural coagulants present a viable alternative (Kawamura, 1991b).Recently however, there has been a resurgence of interest in natural coagulants for water treatment in developing countries (Jahn, 1981, 1986, 1988).

Moringa oleifera is a tropical multipurpose tree that is commonly known as the miracle tree (Fuglie, 2001). Among many other properties, M. oleifera seeds contain a coagulant protein that can be used either in drinking water clarification (Ndabigengesere et al., 1995) or wastewater treatment (Ndabigengesere and Narasiah, 1998). It is said to be one of the most effective natural coagulants and the investigation on these kinds of water treatment agents is growing nowadays (Sciban et al., 2009). Consequently, the search for simple and low cost purifications procedures as well as the use of the coagulant in combination with other coagulants in treatment processes needs to be adopted (Ghebremichael et al., 2009). Some examples of drinking water treatment using crude extract in pilot plant set up have been conducted (Beltran-Heredia and Sanchez-Martin, 2009).

The preparation of low-cost adsorbents for water purification, waste and wastewater treatment has recently been reviewed by Pollard et al. (1992). For example, a wide range of lignocellulosic agricultural by-products have successfully been converted into activated carbons, including coconut coir (Hitchcock et al., 1983), jute stick (Banerjee and Mathew, 1985), sarkanda grass (Chugtai et al., 1987), palm-tree cobs (Renouprez and Avom, 1988), rice husk (Nawar and Doma, 1989) and tamarind nut shells .The suitability of

185 Int. j. Environ. 3(3): 184 -191, 2014 these precursors is determined by their local and bulk availability, carbon content and the presence of inherent microstructure within the substrate itself. Viability of their ultimate use may be determined as much by these factors as by the adsorptive capacity, regenerative characteristics and physical form of the subsequent carbon product.

Activated carbons can be produced from virtually any type of carbonaceous materials such as coconut shell, palm shell, nut Shell, olive Stones, oil-palm stones, agricultural wastes, and many others. The preparation of activated carbon generally involves two steps: carbonization of the raw material in the absence of oxygen and activation of the carbonized products with water and/or CO2 .Volatile matters are released in the carbonization step, and the remaining solid carbon structure is generally called as char. In the following activation step, char reacts with activating agents to form activated carbon (AC) with improved pore structure and surface properties. (Muhamed 2010).

Nowadays, water quality has become the popular issue in this worldwide. A lot of people need the best quality of water for their daily lives. Therefore, it needs treatment to make it safe for human and all living things in the word. There are many types of treatment that improve water quality. One of the filaments is using activated carbon as algal removal. Activated carbon comes from many types like saw dust rice husk, coconut shell and other but this study will focusing more on activated carbon from saw dust. (Muhamed 2010). The main objectives of this study are:

-To produce activated carbon from saw dust. -To choose the most suitable and effective characteristics of activated carbon from saw dust as algal removal.

-To determine the effectiveness of activated carbon using sawdust as algal removal Materials and Methods

Water treatment

Chemical coagulant, namely, aluminum sulphate and ferric chloride were tested for Nile water algal removal. In addition, natural seeds flocculants, namely Moringa oleifera seeds was tested. A jar test procedure was used for these purposes. (Kawamura, 1991a, Bratby 1980).

Jar test

Coagulation and flocculation were conducted via the "Jar test" procedure. The apparatus used consists of multiple stirrer fitted with 6 paddles for stirring is equipped with a speed regulator. The jar test procedure devised by (Cohen, 1957, Bulusu & Sharma, 1967 and Berradi et al., 2014) was employed.For the jar test one litter sample of raw Nile water placed into jars and test coagulant added in rising dosages. While stirrer set to flash mixing at a stirring speed 100 rpm for 1 min. after which, the speed was further reduced in stepwise order down to 20 rpm for 15 min. then stopping to be settled for 30 min followed by sample siphoning from supernatant solution into clean containers. Characterization of water following coagulation was carried out for turbidity determination and residual phytoplankton counts.

Chemical coagulants

A- Aluminum sulphate solution. 1% Al2 (SO4)3 16 H2O solution in distilled water was prepared. B- Ferric chloride solution. 1% FeCl3 Solution in distilled water was prepared. Both coagulant solutions must be freshly

prepared prior to their use in every experiment. Natural flocculants

Moringa oleifera

After careful removal of seed coats and seed wings the quality of the kernels was inspected. The seeds

weighted and then thoroughly pounded and squeezed. In mortar. The powder was transferred to a flask and distilled water was added to the powder to make 3% suspension. The suspension was vigorously shaker for about 5 min. to promote water extraction of the flocculants then filtered through white cotton cloth suspensions can be refrigerated up to two weeks without suffering reduction in efficiency.

186 Int. j. Environ. 3(3): 184 -191, 2014 Preparation of Activated carbons from sawdust (SD):

In this study, two activated carbons were prepared by chemical activation of Saw dust (SD) with NaOH and H3PO4 as activating agents (PAC1 &PAC2). Briefly, SD was collected from local saw mill and washed thoroughly with hot water and distilled water to remove adhering contaminants followed by drying in an air oven at 100°C overnight. (Matos et al 2001, & Man and Ridzuan 2008).For chemical activation of SD with dissolved NaOH in distilled water with a weight ratio of sawdust/NaOH= 1/2, stirring for 60 min at 100°C to evaporate the excess water. The resulting mixture was then placed in an electric same furnace for carrying the carbonization at 700°C for 2 h with heating rate 10°/min. The produced sample was thoroughly washed with water, followed by 0.1M HCl and finally by distilled water to attain pH~ 6, and dried at 100°C overnight. The sample was designated as PAC1 and the carbon yield was found to be 11 %. This product has some characteristics; slurry pH= 8.4, total basicity= 2.66 meq/g, methylene blue number = 278 mg/g, total surface area= 485 m2/g, total pore volume= 0.235 cm3/g and pore diameter= 19 Aº.

On the other hand, 50 g of dried sawdust was impregnated with a 100 ml of 50% (v/v) phosphoric acid and left for soaking overnight. The soaked material was put in stainless steel box tube and calcined in a muffle furnace starting from room temperature to 500°C for 2 h. Then, the product was cooled to room temperature and washed with hot water followed by distilled water to reach pH~ 6. Afterwards, the sample (designed as PAC2) was also dried at 100°C overnight. It was found that carbon yield = 44.8 %, slurry pH = 3.5, total acidity = 2.45 meq H+/g, methylene blue number =150 mg/g. Also, the texture properties of PAC2 are measured: total surface area, total pore volume and pore diameter are 400 m2/g, 0.120 cm3/g and 12Aº, respectively (Fig 1).

Fig 1. SEM micrographs of sawdust (left) and activated carbon produced from activation of sawdust with NaOH

at 700oC (right). SEM: Scanning Electron Microscope

Toxicity testing: Experimental animals and food:

Daphnia magna strain that has been successfully grown in the laboratory in synthetic freshwater media (Fayed and Ghazy, 2000), was used as the test organism. Gravid females were transferred at regular intervals to 1-L glass beakers, in which the culture medium; synthetic freshwater medium (pH; 7.9 – 8.3, total hardness; 90 mg/L as MgCO3, alkalinity; 34 mg/L as CaCO3, conductivity; 260 μ mhos/cm) was renewed three times a week and was checked daily for the release of neonates to be used in starting experiments. In these beakers, the animals were fed three times a week with the green micro alga Scenedesmus obliquus. The algal culture was renewed once a week to maintain the algal solution in good condition. The algae and daphnids were kept at a temperature 22±2 °C with a light period of 16 L: 8 D both during culturing and experimental periods.

Acute toxicity tests:

Acute toxicity tests were conducted in triplicates; the daphnid neonates used in the tests were acquired

from an individual culture and maintained in a clean room. Three replicates of ten neonates (less than 24 h old) were used for each treatment and control. Groups of 10 daphnids were placed in 250-ml beakers, each

187 Int. j. Environ. 3(3): 184 -191, 2014 containing 100 ml test wastewater and subjected to test conditions for 48 h. Tests were run without food addition. The number of live organisms after the elapse of 48 h was recorded. Control test was run in parallel in triplicates; each control chamber containing 100 ml synthetic freshwater medium. Temperature was maintained at 22±2 °C by automatic heater. A mercury thermometer was used to measure the temperature in test containers. Daphnids were added to each test and control container and the results of daphnid mortality were recorded after 48 h. The results of experiments were acceptable only in cases where daphnids in the control containers were observed to have a mortality rate of less than 10 % (Ghazy et al., 2013).

Results and Discussion

Enhanced algae removal in drinking water using the conventional treatment

According to excessive phytoplankton growth, which is commonly seen during the whole year in the River Nile water becomes more problem affecting the conventional technique (prechlorination and alum) used in drinking water treatment plant. This search describe laboratory comparison of conventional techniques with modified procedures by using natural flocculant (Moringa oliefera seeds) and activated carbons from sawdust as coagulant aid for Nile water algal removal.

The optimal condition for best algal removal was 5 mg/L chlorine (5 min. contact time) and 30 mg/l aluminum sulphate (30 min. for sedimentation). Dependant on these conditions, the more sensitive algal group for prechlorination was green algae followed by diatoms, where the percentage removal of each total algal group after chlorination they decayed by 53.4% only of total diatoms. In contrast, the response of the three algal groups to aluminum coagulation was nearly equivalent. The combination of chlorine and alum improve the algal groups’ removal to reach 93.8%, 88.2% and 88.7% of each total algal group respectively for green algae, blue-green algae and diatoms.

From the results, the percentage removal for the three algal groups after filtration were 97.5%, 91.5% and 99% for green algae, blue-green algae and diatoms, respectively (Fig. 2).

Effect of commercial (PAClab) carbon and activated carbon produced from saw-dust as coagulant aid for algal removal with:- Aluminum sulphate: The coupling of different types of activated carbons with alum yields a higher rate of algal removal than alum alone. When comparing the efficiency of three activated carbons (PAClab, PAC1, PAC2) used as coagulant aid with alum, it was found that, PAC1 was more effective than PAClab or PAC2) in algal removal (Fig. 3).

188 Int. j. Environ. 3(3): 184 -191, 2014

Ferric chloride The best removal rate of Nile water algae attained by using an optimal ferric chloride dosage and optimal PAC1 dosage when comparing the efficiency of two activated carbons (PAClab or PAC1) used as coagulant aid with ferric chloride. (Fig. 4)

189 Int. j. Environ. 3(3): 184 -191, 2014 Natural flocculants (Moringa oleifera)

This study has focused on the use of appropriate low cost technology for the treatment of drinking water. Therefore, the treatment process of the Nile water algae was modified by stopping the use of alum and using M. oleifera for clarification.

Algal removal after treatment with optimal condition of M. oleifera was very high and reached 92% removal (Fig 5) this is due to the fact that the seed M. oleifera contain a coagulant protein which can replace conventional coagulants such as aluminum salts in both domestic and larger scale water treatment. Jahn and Dirar (1979), observed that purified water using M. oleifera as acoagulant contain a low total bacterial count indicating that the seeds might contain substances with antimicrobial activity.

Results of optimization of activated carbon (PAClab, PAC1) in conjunction with M.oleifera are shown in (Fig. 5). The results showed that the algal removal for (PAClab and PAC1) are the same.When comparing between the efficiency of two chemical coagulants (alum and ferric chloride) and natural flocculants M. oleifera with (PAC1) as coagulant aid, it was found that, the most effective coupling was M. oleifera with (PAC1). This is due to the heavy flocks of M.oleifera which entraps the Nile water algae and easily settled (Fig. 6).

Toxicity test

The results of toxicity tests on treated water, using laboratory activated carbon, the activated carbon prepared from saw dust as coagulant aid with natural coagulant (Moringa) and chemical coagulants (alum and ferric chloride), showed the absence of any toxicity.

190 Int. j. Environ. 3(3): 184 -191, 2014

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