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Removal of Heavy Metal from Acid Mine Drainage Effluents Using ... treatment technologies have focused attention on the metal binding qualities of various.

American International Journal of Research in Formal, Applied & Natural Sciences

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ISSN (Print): 2328-3777, ISSN (Online): 2328-3785, ISSN (CD-ROM): 2328-3793 AIJRFANS is a refereed, indexed, peer-reviewed, multidisciplinary and open access journal published by International Association of Scientific Innovation and Research (IASIR), USA (An Association Unifying the Sciences, Engineering, and Applied Research)

Removal of Heavy Metal from Acid Mine Drainage Effluents Using Vermiculture Ecotechnology R.W.Gaikwad1 and A.S.Gaikwad2 Department of Chemical Engineering, Pravara Rural Engineering College, Loni, Dist: Ahmednagar (MS)-413736, INDIA 2 Department of Civil Engineering, Dr. Babasaheb Ambedkar Technological University, Lonere, Dist: Raigad (MS)-402103, INDIA 1

Abstract: Acid mine drainage (AMD) is a serious environmental problem resulting from the weathering of sulfide minerals. The generation of AMD and discharge of dissolved heavy metals is an significant concern facing the mining industry. AMD usually contains high concentration of metals such as iron, manganese, zinc, lead, copper, and nickel. The intention of this work was to assess the suitability of vermiculture biotechnology, in a continuous flow, for removal of copper (II) ions from acid mine drainage effluents. A two-stage vermifilter was designed and to remove copper (II) ions. The vermicasting used as the bio filter media has shown remarkable capacity for reducing the copper (II) ions, BOD, COD and Suspended Solids in the effluent. The experiments were performed at room temperature with variation in initial concentrations and flow rates through the bed. The experimental results confirmed that vermiculture biotechnology could be used effectively for the removal of copper (II) ions from aqueous medium. Keywords: Adsorption; Copper; canna plants, vermifilter, BOD, COD, SS. I. Introduction The elimination of toxic heavy metals from aqueous wastewaters is currently one of the mainly important environmental issues being studied. Although this issue has been studied for several years, efficient treatment choice are yet limited. Chemical precipitation, ion exchange, reverse osmosis and solvent extraction are the methods most frequently used for removing heavy metals ions from dilute aqueous streams(1). Acid Mine Drainage (AMD) is a serious hazard to human health, animals and ecological systems. This is because AMD contains heavy metal contaminants, such as Cu2+, Fe3+, Mn2+, Zn2+, Cd2+ and Pb2+ which are not biodegradable and thus tend to accumulate in living organisms, causing various diseases and disorders (2,3,4). A number of methods have been used for acid mine drainage treatment including precipitation (5,6), electrochemical remediation (7), oxidation and hydrolysis (8), neutralization (9), ion exchange and solvent extraction (10), ion exchange and precipitation (11), titration (12) , biosorption (13), adsorption (14,15), reverse osmosis (16). Among all conventional methods for removal of heavy metal ions from acid mine drainage wastewater, the tertiary treatment using ion exchange has become a very efficient one (17,18). Studies carried out to look for new and innovative treatment technologies have focused attention on the metal binding qualities of various types of biomass (19). Biosorptive processes are generally rapid and theoretically suitable for extracting metal ions from large volumes of water (20). Even if various types of reactors, e.g. batch, continuously stirred tank reactors and fluidized-bed columns can be used, adsorption in vermifilter has several advantages. It is simple to operate, gives high removal of metals and can be simply scaled up from a laboratory process. Green technology is a technology which uses plants to clean up the contaminants from a specified area [21]. The process is relatively known as phytoremediation. It mainly works on five mechanism – phytoextraction, phytovolatilization, rhizosphere degradation, phytodegradation and hydraulic control [22] the removal of contaminants. Currently, phytoremediation is used for treating many classes of contaminants such as heavy metals, pesticides, petroleum hydrocarbons, explosives, radionuclides, CVOCs etc. [23]. The term heavy metals refers to metals and metalloids having densities greater than 5 g cm3 and is usually associated with pollution and toxicity although some of these elements (essential metals) are required by organisms at low concentrations [24]. Unlike organic compounds, metals cannot be degraded, and their cleanup requires their immobilization and toxicity reduction or removal [25]. For the construction of artificial wetland/ pilot scale study the basic components used are containers, plant species, sand and gravel media in certain ratio. Microbes and other invertebrates develop naturally. There are three life forms of macrophytes which are basically used for construction of constructed wetland. They are floating macrophyte (i.e. Lemna spp or Eichornia crassipes),

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submerged macrophyte (i.e. Elodea canadiensis) and rooted emergent macrophyte (i.e. Phragmites australis, Typha spp). The intention of this study was to explore the effect of flow rate and concentrations of feed metal ions on the functioning of copper (II) adsorption onto canna plant in a vermifilter. II. Experimental All the compounds used to prepare reagent solutions were of analytic reagent grade. A stock solution of copper II (1000 mg l−1) was prepared by dissolving a weighed quantity of CuSO4·5H2O salt in twice distilled water. The concentration ranges varied between 200 to 215 mg l−1 for single metal aqueous solution. Solution pH was adjusted with dilute 0.1 N H2SO4 or 0.1 N NaOH. The Canna plants used as an adsorbent. The naturally occurring Canna plants were procured locally. A Chemito-201 Atomic Absorption Spectrophotometer (AAS) was used to determine the concentration of unadsorbed copper (II) ions in the effluent. In order to test the feasibility of vermifilter and canna plants for the removal of copper (II) ions for an industrial application, a continuous mode of adsorption was studied in a acrylic column set up. The design of the process is shown in Fig. 1.The experimental setup consists of two acrylic boxes with dimension of 500mmx600mm. The boxes were provided with the holes at the bottom for water recovery. A layer of coarse gravel of 25mm size was laid at the bottom. This layer supports a 30mm thick layer of 12mm gravel, which in turn supports 20mm thick layer silt free sand passing through 1.70 mm I.S sieve. These layer make up the drainage system which does not play any major role in the vermification process except providing the support for upper vermification and providing drainage above the sand layer, 300mm thick layer of vermification with earthworm are placed and Canna trees are planted in each box. The vermifier was watered (by sprinkling) for ten days for acclimatization of the system. Wastewater was fed to VF1 by an arrangement shown in Fig. 1. The acid mine drainage wastewater is allowed into VF1 controlling device at the rate shown in Table No.I. Figure 1: Experimental set up

Table I. Rate of hydraulic loading Date

Hydraulic loading

27/2/2014 to 9/3/2014

20 liters per day (water)

10/3/2014 to 16/3/2014

20 liters per day (wastewater)

17/3/2014 to 23/3/2014

30 liters per day ( wastewater )

24/3/2014 to 30/3/2014

40 liters per day ( wastewater )

31/3/2014 to 6/4/2014

50 liters per day ( wastewater )

7/4/2014 to 13/4/2014

60 liters per day ( wastewater )

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The intention of this step was to get better process conditions, to minimize the outlet metal ions concentration of the treated effluent, and thus to obtain lower metal ions concentrations than those set by law before dumping. Hence, the effects of several parameters influencing the adsorption process were studied separately. The pH of the feed tank solution was adjusted to 6.6 before feeding the verifier. The experiments were carried out at constant room temperature (about 300C). In order to access the performance of vermifilter unit, samples were prepared synthetically. This sample was tested for SS, COD, BOD before feeding to VF1. The characteristics of wastewater are shown in Table no II. The samples of wastewater were fed to vermifilter VF1 at the constant rate of flow so that the rate of infiltration of vermifier was equal to the rate of application and no ponding occurred. The output from the first vermifier was sent to the second vermifier. The output from VF1 and VF2 were tested for BOD, COD ,SS, Cu(II) at regular intervals. All the samples of the wastewater which being collected and analyzed for important parameter like Biochemical Oxygen Demand, Chemical Oxygen Demand, Suspended solids and Cu(II) ions. Table II. The characteristics of wastewater Parameter

Concentration

pH

6.6

Temperature

22oC

Suspended solid (mg/lit)

310

COD (mg/lit)

546

BOD5 (mg/lit)

208

Cu(II) (mg/lit)

215

III. Result and Discussion For each of the organic loading rate applied to the vermifier, figures were prepared to depict the pattern of biodegradation of waste in terms of reduction in the concentration of various parameters like COD, BOD, SS and Cu (II).Each of these figures 2 to 5, presented the daily reduction in concentration of particular parameter in VF1 and VF2 throughout the duration of 7 days for which a particular loading rate was constantly maintained. The pattern of variation in concentration of COD with respect to time and with respect to different loading rate is shown in figure 2. From this, it can be seen that the percentage reduction in COD for VF1 ranges from a value of 61.00% to 76.00% corresponding to different initial organic loadings. The corresponding reduction in VF2 ranges from 65.00% to 86.00% thus the overall efficiency of removal of COD is higher in case of two stage vermifilter unit. Figure 2: Variations in COD

The percentage reduction in concentration of BOD in VF1 ranges from 75.00% to 93.00% corresponding respectively different organic loading. The corresponding reduction in VF2 ranges from 90.00% to 97.00% thus representing the higher efficiency of two stage filter in comparison with single stage which is shown in figure 3.

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Figure 3: Variations in BOD

Figure 4, shows the percentage reduction in concentration of suspended solids in VF1 corresponding to different loading varies from 91.00% to 94.00% respectively. The corresponding removal in VF2 ranges from 91.00% to 95.00%. Figure 4: Variations in Suspended Solids

The percentage reduction in concentration copper (II) in VF1 corresponding to different loading varies from 91.00% to 92% respectively. The corresponding removal in VF2 ranges from 95.00% to 98.00% which is shown in figure 5. Figure 5: Variations in Cu (II)

From the above results it is seen that the water quality in terms of BOD, COD and SS and Cu(II) ions have been reduced considerably as the wastewater passes through the two stage filter. Due the presence of earth worm the

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soil is broken into smaller units in the form vermicompost, due to which large percentage reduction in SS and Cu(II) ions is observed. IV. Conclusion Copper (II) ions, BOD, COD and SS can be removed from aqueous solutions very effectively by means of the vermicutural technology using Canna plants. Adsorption of copper (II) ions through vermifilter is an economically feasible technique for removing metal ions from a solution. The process allows treatment of a given volume of effluent by using a minimal mass of adsorbent which concentrates maximal content of metal. The low-cost, efficient, readily available plant materials can be used for the removal of heavy metals from solution. When compared with conventional wastewater treatment methods, this technology is more suitable for water clean up because they are accountable for decomposing organic pollutants to non-toxic low molecular substances which can easily be degraded by microorganisms. This technology does not bring in any supplementary chemical substances into the environment. They are moderately easy to supervise and they can be adopted without difficulty to the local needs. The best application is that they are able to remove several pollutants which are in combination. The plant species which are local can be used for recycling of water in the water bodies. The concentration of contaminants should not be in excess to ensure that they do not affect the growth rate of the plant species as excess may cause toxicity. The fundamental advantage is that it uses a natural process, simple in construction, improves water quality as well as recycling of water. Apart from that it uses local materials and plant species and no electricity is required. Thus it also contributes to conservation of energy. The only disadvantage is that it requires regular maintenance, certain life span and its construction cost. They must be effectively managed if they are to continue to improve water quality. V. References [1] [2] [3] [4] [5] [6]

[7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22]

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