Journal of Environmental Science and Health, Part A (2015) 50, 980–988 Copyright © Taylor & Francis Group, LLC ISSN: 1093-4529 (Print); 1532-4117 (Online) DOI: 10.1080/10934529.2015.1030299
Removal of ammonia nitrogen from leachate of Muribeca municipal solid waste landfill, Pernambuco, Brazil, using natural zeolite as part of a biochemical system CECILIA MARIA M. S. LINS1, MARIA CRISTINA M. ALVES1,2, JUACYARA C. CAMPOS3, 1 and EDUARDO ANTONIO M. LINS1 FERNANDO T. JUCA FABRICIA MARIA S. SILVA1, JOSE 1
Solid Waste Research Group (GRS), Federal University of Pernambuco, Recife, Brazil Civil Engineering Department, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil 3 School of Chemistry, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil 2
The inadequate disposal of leachate is one of the key factors in the environmental impact of urban solid waste landfills in Brazil. Among the compounds present in the leachates from Brazilian landfills, ammonia nitrogen is notable for its high concentrations. The purpose of this study was to assess the efficiency of a permeable reactive barrier filled with a natural zeolite, which is part of a biochemical system for the tertiary treatment of the leachate from Muribeca Municipal Solid Waste Landfill in Pernambuco, Brazil, to reduce its ammonia nitrogen concentration. This investigation initially consisted of kinetic studies and batch equilibrium tests on the natural zeolite to construct the sorption isotherms, which showed a high sorption capacity, with an average of 12.4 mg NH4C. L¡1, a value close to the sorption rates found for the aqueous ammonium chloride solution. A permeable reactive barrier consisting of natural zeolite, as simulated by the column test, was efficient in removing the ammonia nitrogen present in the leachate pretreated with calcium hydroxide. Nevertheless, the regenerated zeolite did not satisfactorily maintain the sorption properties of the natural zeolite, and an analysis of their cation-exchange properties showed a reduced capacity of 54 meq per 100 g for the regenerated zeolite compared to 150 meq per 100 g for the natural zeolite. Keywords: Leachate, natural zeolite, ammonia nitrogen, sorption, sanitary landfill, solid waste.
Introduction Leachate from urban solid waste sanitary landfills is nowadays considered to be a major environmental problem because it can cause contamination of soil as well as surface and underground water. High concentrations of ammonia nitrogen (>1.000 mg.L¡1) are commonly found in leachate from Brazilian landfills,[1] which if not properly treated and disposed, can cause serious environmental problems of water and soil contamination, leading to severe impacts to receiving water bodies.[1,2] Earlier studies have shown that zeolites can beneficially substitute the cation-exchange resins used in effluent treatment. They are also capable of facilitating ionic exchange between the ammonium ion (NH4C) and other more biologically acceptable cations such as sodium (NaC), calcium
Address correspondence to Maria Cristina M. Alves, Federal University of Rio de Janeiro, 149 Athos da Silveira Ramos Avenue, I-203, Rio de Janeiro 21941-909, Brazil; E-mail: [email protected] Received December 22, 2014.
(CaC2), potassium (KC) or hydrogen (HC).[3–6] Zeolites have a high capacity for cation exchange, good chemical properties and physical strength and an excellent environmental compatibility. The zeolites are a class of adsorbents of major economic and social interest, especially with regard to the removal of metal cations and ammonium ions.[7] Another major benefit of the use of zeolites is the possibility of their regeneration for reuse. The Muribeca Solid Waste landfill, located in the State of Pernambuco in the northeast of Brazil, received around 3,600 tons per day of waste since 1985 until July, 2009.[8] The biochemical system from Muribeca Landfill leachate treatment system uses the set of three components: soil, plants and microorganisms to remove, degrade or isolate toxic effluents.[9–11] This system is characterised as a tertiary treatment process of decontamination, which occurs of different and concomitant ways based on two principles of effluent treatment techniques already consolidated: permeable reactive barrier (PRB) and phytoremediation through aquatic plants, as shown in Figure 1. PRB is composed of reactive material that can retain effluent pollutant chemically and/or physically as it gets through it preventing contamination downstream of the
Removal of ammonia nitrogen from landfill leachate using natural zeolite
981
Fig. 1. Schematic diagram of the biochemical system of Muribeca Landfill.
barrier. As a first attempt, the PRB was filled with clay and activated carbon with the aim of minimizing the concentrations of heavy metals resistant to primary and secondary treatments.[10] In an attempt to use this technique to reduce ammonia nitrogen concentration, a new search for reactive materials was made, among which natural zeolite was selected as a promising candidate. This study aims to evaluate the application of natural zeolite in a PRB for the tertiary treatment of leachate from the Muribeca Municipal Solid Waste Landfill in Pernambuco State, Brazil.
analysis using a Rigaku model RIX 3000 X-ray fluorescence spectrophotometer (The Woodlands, TX, USA). To complement the chemical characterization of the zeolite, the cation-exchange capacity (CEC) was determined according to the procedure described by EMBRAPA.[12] The mineralogical characteristics of the zeolite were determined by X-ray diffraction analyses using a Siemens XRD D5000 (Buffalo Grove, IL, USA) diffractometer with a graphite monochromator and a nickel (Ni) filter. The physical characterization of the zeolite followed the standards described by Brazilian Standards (ABNT),[13] for soil geotechnical characterization.
Materials and methods This investigation consisted of three stages. The first stage involved characterizing the natural zeolite and the raw leachate used in the study. In the second stage, preliminary studies and batch equilibrium tests were carried out to construct the sorption isotherms. Finally, the PRB efficiency was assessed for the leachate treatment using column tests simulating onsite conditions including regeneration of the zeolite.
Characterization of natural zeolite The natural zeolite used in the experiments was extracted from a deposit located in the county of Calingasta, Province of San Juan, Argentina, according to the company that supplied the material (Sol Minerales do Brasil). The chemical composition of the oxides in the studied zeolite was determined by semiquantitative
Characterization of the leachate The leachate used in the experiments came from the Leachate Treatment Plant of the Muribeca Landfill, 16 km from the city of Recife in the county of Jaboat~ ao dos Guararapes, Pernambuco State, in northeast Brazil. This was the largest landfill in operation in the Recife metropolitan region, covering an area of 64 ha; the landfill ceased operating in 2009. The leachate samples were collected in a flow box located behind the decanting pool of the Muribeca landfill treatment plant to obtain a homogeneous raw leachate with a reduced amount of suspended solids. After collection, physicochemical characterization of the samples was made in accordance with the Standard Methods for the Examination of Water and Wastewater,[14] listed in Table 1. The reported values are the mean values of four collection campaigns run in August, October and December 2007 and January 2008.
982
Lins et al.
Table 1. Main analytical methods used to characterize the leachate. Parameters
Analytical method
Reference
pH Alkalinity (mg CaCO3.L¡1) BOD5 (mgO2.L¡1) COD (mgO2.L¡1) Color (uH) Turbidity (NTU) Conductivity (mS.cm¡1) Ammonia Nitrogen (mg NH4C.L¡1) Chloride (mgCl¡.L¡1) Solids Series (mg.L¡1)
Potentiometric Titrimetric Manometric Titrimetric (Digestion with K2Cr2O7) PhotoColorimetric Nephelometric Electrical Conductance Electrometric (Ion selective electrode - Orion Model 720**) PhotoColorimetric Gravimetric
SMEWW 4500 B SMEWW 2320 B SMEWW 5210 SMEWW* 5220 C SMEWW 2120 C SMEWW 2130 B SMEWW 2510 B SMEWW 4500 - NH3 D Spectroquant 14897 - MERCK*** Adapted from SMEWW 2540 B, 2540 C, 2540 D.
*SMEWW: Standard Methods For The Examination Of Water And Wastewater.[14] **Orion (Thermo Scientific, Billerica, MA, USA). ***Merck (Darmstadt, Germany).
Preparation of leachate samples for tests In the experiments using natural zeolite, two different types of leachate were tested: raw leachate (L1) and leachate pretreated with calcium hydroxide (L2). Besides, an aqueous mono solution of ammonium chloride (AS) was tested to evaluate the affinity of the zeolite for adsorving this particular ion. The raw leachate (L1) was prepared as follows: after determining the ammonia nitrogen concentration, dilutions of the raw leachate were made with deionized water to obtain different concentrations of ammonia nitrogen. The L2 was obtained from pretreatment of the L1 with calcium hydroxide in order to remove part of organic matter from the leachate. This pretreatment was undertaken in a test jar in which 12 L of L1 were shaken together with calcium hydroxide (35 g Ca(OH)2 per L) for 10 min at 120 rpm, after which the pH of the pretreated leachate was adjusted with a solution of HCl (6 mol.L¡1) to a value of around 8.5, similar to the L1. Dilutions were then made with deionized water, adopting the same procedure as with L1. For the aqueous ammonium chloride solution (AS), a solution was prepared with deionized water and ammonium chloride to obtain samples with different ammonia nitrogen concentrations for the experiments. Ammonia nitrogen concentration was 1,532 mg L¡1 in L1 and 1,270 mg L¡1 in L2. Preliminary studies Initial tests for assessing the ammonia nitrogen sorption by the zeolite were performed to determine the optimum conditions for the zeolite–ammonia nitrogen system to reach equilibrium. Six grams of zeolite were weighed and placed into 125-mL Erlenmeyer flasks to which 100 mL of the solutions (L1, L2 or AS) were added to provide a concentration around 340 mg NH4C.L¡1. For each solution, 11 Erlenmeyer flasks were prepared (zeolite C solution) and placed in an incubator with shaking at 120 rpm and a constant
temperature of 28 C. At preset intervals, varying from 3 min to 24 h, aliquots of the supernatants were collected from the zeolite and immediately analyzed for ammonia nitrogen concentration, pH, conductivity and chemical oxygen demand (COD). These analyses adopted the same procedures as those used for characterizing the leachate. Batch equilibrium tests The sorption of the zeolite was evaluated using batch equilibrium tests in accordance with the EPA/530/SW-87/ 006-F standard.[15] At this stage in the experiments, a series of suspensions was prepared in 125 mL Erlenmeyer flasks, each consisting of six g of zeolite and 100 mL of solutions (L1, L2 or AS) to provide concentrations varying between 30 and 1,700 mg NH4C. L¡1. Control samples were prepared using 100 mL of the contaminants at the various ammonia nitrogen concentrations without zeolite for evaluating loss by evaporation. The samples were placed in the incubator and shaken at 120 rpm at a constant 28 C temperature. After 24 or 72 h the solutions were removed, samples of the supernatants were taken and the ammonia nitrogen concentration, pH, conductivity and COD were determined. Column experiments and regeneration As the PRB with natural zeolite played the role of a final polishing treatment, this stage of experiments was only carried out with the pretreated leachate (L2). In this test, the sample was fitted into the permeameter (Tri-Flex System 2 - Soil Test, ELE International, Bedfordshire, UK) to simulate conditions in the onsite PRB. The RPB simulation was carried out into a PET cylinder 10 cm in diameter and 9 cm high were placed 715 g of dry zeolite so field specific weight and compaction conditions were met. The zeolite sample was then saturated with distilled water. Afterwards, a downward flow of the leachate-
983
Removal of ammonia nitrogen from landfill leachate using natural zeolite Table 2. Characterization of raw leachate collected from Muribeca Landfill used in this work. Parameters pH Alkalinity (mg CaCO3.L¡1) BOD5 (mgO2.L¡1) COD (mgO2.L¡1) BOD5/COD Color (uH) Turbidity (NTU) Conductivity (mS.cm¡1) Ammonia Nitrogen (mg NH4C.L¡1) Chloride (mgCl¡.L¡1) Total Solids (mg.L¡1) Total Dissolved Solids (mg.L¡1) Total Suspended Solids (mg.L¡1)
Mean values
Minimum values
Maximum values
8.59 7243 2781 3951 0.70 9558 170 19.90 1453 411 10341 8530 1811
8.46 5867 2320 3307 0.67 8645 137 18.24 1125 227 8890 7022 1280
8.70 7838 3190 4735 0.74 10550 193 21.33 1708 760 11469 9524 2082
solution was applied through the test sample and the effluent was periodically collected in graduated receivers. Shortly after each collection, the ammonia nitrogen concentration, pH and conductivity of the effluents were determined. The test should end when the ammonia nitrogen concentration was constant and approximately the same as the initial concentration of the contaminant. The second part of this test was the regeneration of the zeolite. This process was done using a 1 mol.L¡1 solution of sodium chloride (NaCl) as a percolating liquid, with the pH adjusted to within 10–11 with a 1 mol.L¡1 sodium hydroxide solution,[6] and adopted the same column test procedure described here.
Results and discussion Characterization of natural zeolite The zeolite was composed mainly of oxides, mostly SiO2, at 58.16%, followed by CaO, 9.9%; Al2O3, 7.67%; Fe2O3, 6.63%; and K2O, 3.07%. All other oxides were present in amounts less than 1%: TiO2, 0.965%; P2O5, 0.905%; BaO, 0.245%; SrO, 0.235%; MgO, 0.17%; ZrO2, 0.16%; MnO, 0.105%; other oxides, 0.175%. Loss on ignition was 11.62%. Analysis of X-ray diffraction result together with analysis of the oxides present in the zeolite indicated a clinoptilolite zeolite type. The CEC value of 130 meq per 100 g found for this zeolite is within the range obtained by other researchers, as follows: 62 to 229 meq per 100 g.[6, 16-18]
leachates from Brazilian Municipal Solid Waste (MSW) landfills. Preliminary tests It was found that the removal of the ammonia nitrogen from liquid phase occurred quickly with the three solutions studied (L1, L2 and AS), up to approximately 4 h of shaking, as shown in Figure 2. From this point onward, the removal efficiency values tended to stabilize as the contact time was increased, almost reaching a steady state between six and eight hours of shaking. After 24 h of shaking, it was still possible to detect a small reduction in the ammonia nitrogen concentration, which was considered negligible. The drop in the removal efficiency for ammonia nitrogen at the end of the experiment indicated a possible saturation of the zeolite by ammonium ions both on the outside surface and in the pores of the clinoptilolite.[16] Significantvariations in the concentration of ammonia nitrogen were not found in the tested control samples. This fact
Characterization of leachate Table 2 shows the complete characterization of the raw leachate. Values of the analyzed parameters are in accordance with Souto[19] in his comprehensive review of the published values of these parameters for
Fig. 2. Removal efficiency of ammonia nitrogen by the zeolite versus contact time.
984
Lins et al.
ensures that removal occurred just due to the presence of natural zeolite. The efficiency of ammonia nitrogen removal by the zeolite was lower for L2 than for L1, with the former reaching approximately 45% after 6 h, whereas the latter reached 60% by this time. The removal efficiency obtained with AS was above 75% after 6 h, reaching a little more than 80% after 24 h. Wang et al.[3] also found that higher adsorption capacities were obtained with an aqueous ammonium chloride solution than with leachate. On the other hand, the difference between the removal efficiency of the L1 and L2 was probably due to calcium left on the precipitation process in L1, which competed for the same sites with ammonia. Batch equilibrium Although the preliminary results yielded two sorption isotherms, i.e., for 24 and 72 h, for each solution (L1, L2 and AS), a minimum equilibrium period of 24 h was adopted to fulfill the US EPA standard,[15] although the preliminary results showed that 6 hours were enough to reach the equilibrium. Experimental data were adjusted according to the nonlinear Freundlich [Eq. (1)] and Langmuir [Eq. (2)] models, as linear approximations did not provide a good fit to the data. q D Kp CeN
(1)
where Kp (partition coefficient) is proportional to the sorption capacity and N is the slope of the curve that reflects the intensity of sorption as concentration increases. qD
½a b Ce ½ 1 C a Ce
(2)
where a is a constant of sorption and b is the maximum rate of sorption of chemical species of interest. The sorption curves obtained at 24 and 72 h are shown in Figure 3 for L1, in Figure 4 for L2 and in Figure 5 for AS. These figures show that the Langmuir isotherm better fitted the experimental data for all experiments. From the above data, the sorption parameters were calculated for the two models in question, namely, the partition coefficient (Kp) and Freundlich sorption constant (N) for the Freundlich model and the maximum sorption rate (b) and Langmuir sorption constant (a) for the Langmuir model. The values of these parameters are shown in Table 2 along with results previously reported in the literature. The coefficient of determination (R2) is also presented As the Langmuir model yielded a much better fit of the experimental data for AS, L1 and L2, subsequent analysis was focused on the Langmuir parameters b and a:
Fig. 3. Sorption isotherms with zeolite and raw leachate (L1) obtained after (a) 24 h and (b) 72 h.
The great majority of the published data shown in Table 3 deal with ammonium monosolutions except for the data presented in Wang et al.,[3] which concerns a mixture of leachate and an aqueous solution of ammonium chloride (AS). With respect to time effect on sorption parameters, the data obtained with AS in the present work indicate that 24 h was the ideal time for removing ammonia nitrogen, obtaining a maximum sorption rate of 13.69 mg NH4C.g¡1. For the 72-h time, a slight reduction in the sorption rate was found, resulting in 12.98 mg NH4C.g¡1. In contrast, both L1 and L2 showed higher values for b and a for the 72-h test. Nevertheless, as the differences between these values was less than 10% for all tests, it appeared reasonable to use 24-h tests as the standard for analysis. Analysis of the results from AS tests revealed that the values of the maximum sorption capacity (b) were very
Removal of ammonia nitrogen from landfill leachate using natural zeolite
985
Fig. 4. Sorption isotherms with zeolite and leachate pretreated with calcium hydroxide (L2) obtained after (a) 24 h and (b) 72 h.
Fig. 5. Sorption isotherms with zeolite and an aqueous ammonium chloride solution (AS) obtained after (a) 24 h and (b) 72 h.
similar to those obtained by Lei et al.[20] and Englert and Rubio,[21] although different from the results presented by Saltali et al.[5] Nevertheless, all these values are of the same order of magnitude. However, the value presented in Sarioglu[6] is almost two times that found in this study, which may be explained by the different mineralogical components of the natural zeolite used in their study (45% clinoptilolite, 35% mordenite and 20% other components). It was also found that the maximum sorption rates (b) obtained for L2 were slightly less than the L1 values. The reason for this small difference can be attributed to the treatment of L2, resulting in a larger quantity of calcium ions in solution than in L1. This may therefore have contributed to increased competition for exchangeable sites on the zeolite and reduced the adsorption rate of the ammonia nitrogen. Values of the sorption rates obtained for L1, L2 and AS, which varied from 10.53 mg NH4C.g¡1 for L2 to 13.69 mg NH4C.g¡1 for AS, were similar in the 24-hour test. In the 72-hour tests, these values were even
more similar, around 12 mg NH4C.g¡1 for all three tests (AS, L1 and L2). This fact is very important because it can be justified by the high affinity of the zeolite for the ammonium ions, in accordance with the order of selectivity: CsC> RbC> KC> LiC> NH4C> NaC> BaC2> CaC2.[5]
Column experiments Figure 6 shows the breakthrough curve obtained with the first passage of L2 through the zeolite, maintaining an average permeability of 1.48 £ 10¡4 cm.s¡1. The main point of the column test was the analysis of this breakthrough curve, and it is generally close to an “S” shape in sorption processes. However, several parameters such as initial pollutant concentration, flow rate, adsorption mechanism and column diameter can affect the shape of this curve.[6] It can be observed in the same figure that the C/Co ratio was very low until the tenth void volume, corresponding to
986
Lins et al.
Table 3. Sorption parameters in the literature compared to results of the present study. Freundlich model Source
Kp (mg.g¡1)
Wang et al.[3] Saltali et al.[5] Sarioglu[6] Du et al.[16] Lei et al.[20] Englert and Rubio[21] Karadag et al.[22]
0.43 0.93 2.23 1.36 5.09 — 0.61
Sorption test (AS) 24 h Sorption test (AS) 72 h Sorption test (L1) (24 h) Sorption test (L1) (72 h) Sorption test (L2) 24 h Sorption test (L2) 72 h
1.04 1.53 0.54 0.72 0.65 0.74
N (L.g¡1)
Langmuir model R2
0.458 0.98 0.488 0.96 0.380 0.98 0.279 0.99 0.220 0.99 — — 0.517 0.95 Results from present study 0.363 0.99 0.354 0.98 0.446 0.94 0.443 0.90 0.413 0.96 0.424 0.94
B (mg.g¡1)
a (L.mg¡1)
R2
2.13 9.64 25.77 — 13.74 12.3 8.12
0.182 0.055 0.018 — 0.23 — 0.029
0.99 0.96 0.98 — 0.95 0.97 0.92
13.69 12.98 11.36 12.82 10.53 12.05
0.008 0.038 0.007 0.012 0.009 0.011
0.97 0.99 0.98 0.99 0.99 0.99
16 h of testing, indicating the high sorption of the ammonia nitrogen by the zeolite. From this point on, the C/Co ratio began to increase, approaching the saturation of the zeolite. The column test was terminated after 159 h, due to operating limitations, reaching around 70% (C/Co D 0.7) saturation of the zeolite in this period. The reduction in contaminant removal efficiency when the L2 seeped through the zeolite was as expected, because the zeolite has a saturation point where the sorption capacity of the ammonia nitrogen is reduced or practically null. This fact was also observed during the batch equilibrium tests. Karadag et al.,[22] in their study of leachate with an ammonia nitrogen concentration of 200 mg.L¡1 at pH 8.3, found that the saturation of the zeolite occurred after 164 h of testing, and this time could be altered with pH variation, due to the form of ammonia nitrogen that may be present (dissociated ammonia,
NH4C, which is in the ionic form, and undissociated ammonia, NH3, which is also known as free ammonia), depending on the pH.[1]
Fig. 6. Breakthrough curve of ammonia nitrogen through zeolite bed with pretreated leachate (L2).
Fig. 7. Concentration of ammonia nitrogen during zeolite-regeneration process using NaCl solution.
Regeneration The potential for regenerating the zeolite after saturation with ammonium ions by leachate passage was tested. Figure 7 shows the data obtained from the zeolite-regeneration process. In the initial flow of sodium chloride solution, the ammonia nitrogen concentration reached a value of over 500 mg.L¡1 with only two void volumes passage through the column. This fact may be due to the initial displacement of calcium ions (data not measured), after that, the sodium ions begun to displace ammoniums ions. After
Removal of ammonia nitrogen from landfill leachate using natural zeolite reaching a peak value, the ammonia nitrogen concentration began to decrease and finally stabilized after 50–60 void volumes, corresponding to approximately 17 h of flow. Ammonia nitrogen concentration dropped to less than 1 mg.L¡1, thereby indicating the end of the zeoliteregeneration process. Du et al.[16] noted that during the regeneration process the highest peaks of ammonia nitrogen concentration (400–500 mg.L¡1) were obtained between 2.5–5 void volumes, and the process was concluded after 15–20 void volumes. Karadag et al.[22] found that the removal of ammonia nitrogen was fast in the first 30 min of regeneration, and in this study the total regeneration occurred after 15 h using 20 g NaCl.L¡1 and 23 h using 10 g NaCl.L¡1. After the regeneration process, a sample of the zeolite was removed and the new cation exchange capacity (CEC) was analyzed to check the efficiency of this regeneration. The natural zeolite CEC was 130 meq per 100 g, and after the regeneration it was 54 meq per100 g, 58% less than the raw natural zeolite, showing that the regeneration process utilized here was not so efficient. One hypothesis explaining this low efficiency is that the number of regeneration cycles was not satisfactory for an efficient cation exchange between the ammonium ions of the zeolite and the sodium ions in the regeneration solution or, as a second hypothesis, that the concentration of the regeneration solution used was not optimal. Finally, the organic matter, which was also adsorbed from the leachate, may be causing decreased zeolite CEC. Sarioglu[6] reported in experiments performed on domestic wastewater that there was a drop of 31.52% in the adsorption capacity of the zeolite after regeneration. However, experiments using synthetic ammonium solution showed that the regeneration process adopted in their experiments was efficient for regenerating the zeolite, mainly in the first regeneration cycles, where an increase was found in the adsorption capacity for ammonia nitrogen.[16]
Conclusions Considering the tests performed on a bench scale, the use of a reactive barrier consisting of natural zeolite is promising as a final polishing system in treating the leachate from the Muribeca landfill. From the kinetic tests, it was found that the ammonia nitrogen was removed quickly, especially in the first six hours of shaking, and that the rate of removal later decreased and tended to stabilize. With regard to the natural zeolite, it showed a high sorption capacity for the ammonia nitrogen present in the leachates, with an average of 12.4 mg NH4C.L¡1, a value close to the sorption rates found for the aqueous ammonium chloride solution. This indicates a high selectivity of the ammonium ion by the zeolite, as the leachate has a number of other ions that compete with ammonium ions for adsorption sites.
987
A permeable reactive barrier consisting of natural zeolite, as simulated by the column test, was efficient in removing the ammonia nitrogen present in the leachate pretreated with calcium hydroxide. Nevertheless, the regenerated zeolite did not satisfactorily maintain the sorption properties of the natural zeolite, and an analysis of their cation-exchange properties showed a reduced capacity of 54 meq per 100 g for the regenerated zeolite compared to 150 meq per 100 g for the natural zeolite.
Acknowledgments We also thank all the staff of the Solid Waste Group of the Federal University of Pernambuco, GRS/UFPE for their technical support.
Funding The authors thank the research network PROSAB/ FINEP/CNPq and CNPq through Edital Universal – Edital 2006 for financial support.
References [1] Campos, J.C.; Moura, D.; Costa, A.P.; Yokoyama, L.; Araujo, F. V.F.; Cammarota, M.C., Cardillo, L. Evaluation of pH, alkalinity and temperature during air stripping process for ammonia removal from landfill leachate. J. Environ. Sci. Health Pt. A 2013, 48(9), 1105–1113. [2] Liu, J.; Luo, J.; Zhou, J.; Liu, Q.; Qian, G.; Xu, Z.P. Inhibitory effect of high-strength ammonia nitrogen on bio-treatment of landfill leachate using EGSB reactor under mesophilic and atmospheric conditions. Bioresour. Technol. 2012, 113(3), 239–243. [3] Wang, Y.; Liu, S.; Xu, Z.; Han, T.; Chuan, S.; Zhu, T. Ammonia removal from leachate solution using natural Chinese clinoptilolite. J. Hazard. Mater. 2006. 136(3), 735–740. [4] Karadag, D.; Tok, S.; Akgul, E.; Turan, M.; Ozturk, M.; Demir, A. Ammonium removal from sanitary landfill leachate using natural Gordes clinoptilolite. J. Hazard. Mater. 2008. 153(1–2), 60–66. [5] Saltali, K.; Sari, A.; Aydin, M. Removal of ammonium ion from aqueous solution by natural turkish (Yildizeli) zeolite for environmental quality. J. Hazard. Mater. 2007, 141(1), 258–263. [6] Sarioglu, M. Removal of ammonium from municipal wastewater using natural Turkish (Dogantepe) zeolite. Separ. Purif. Technol. 2005. 41(1), 1–11. Comparison of different physico[7] Cotman, M.; Gotvajn, A.Z.; chemical methods for the removal of toxicants from landfill leachate. J. Hazard. Mater. 2010, 178(1–3), 298–305. [8] Maciel, F.J.; Juc a, J. F. T. Evaluation of landfill gas production and emissions in a MSW large-scale experimental cell in Brazil. Waste Mgmt. 2011, 31(5), 966–977. [9] Maciel, F.J.; Juc a, J.F.T. Biogas recovery in an experimental MSW cell in Brazil: lessons learned and recommendations for CDM projects. Greenhouse Gas Measure. Mgmt. 2013, 2(4), 186–197. [10] Alves, M.C.M.; Beltr~ ao, K.G.Q.; Juc a, J.F.T. Assessment of metals sorption in the permeable reactive barrier of the leachate treatment system of Muribeca Landfill, Recife, Brazil. In: 5th International Congress on Environmental Geotechnics, Cardiff -
988
[11]
[12]
[13]
[14]
[15]
[16]
Lins et al. Wales, United Kingdom. Jun 26–30, 2006; Thomas, H R. Editor; Thomas Telford Ltd.: London, 2006. Brito, K.G.Q.; Juc a, J.F.T. Alternativa para tratamento de chorume em aterros sanit arios - sistema de barreira bioquímica. In: XI Simposio Luso Brasileiro de Engenharia Sanit aria e Ambiental, Natal, Brazil. Mar 28–Apr 2, 2004; ABES: Rio de Janeiro, 2004. In Portuguese. EMBRAPA (Brazilian Company of Agricultural Research). Soil Analysis Handbook. 2nd edition, Brazilian Company of Agricultural Research: Rio de Janeiro, 2011. In Portuguese. ABNT (Brazilian Association for Technical Standards): NBR 6508 – Determination of Soil Particle Specific Mass. Brazilian Association for Technical Standards: Rio de Janeiro, 1984. In Portuguese. APHA. Standard Methods for the Examination of Water and Wastewater, 20th ed. APHA/AWWA/WEF: Washington, DC, 1998. US EPA. United States Environmental Protection Agency. BatchType Procedures for Estimating Soil Adsorption of Chemicals. Office of Solid Waste and Emergency Response: Washington, DC, 1992. Du, Q.; Liu, S.; Cao, Z.; Wang, Y. Ammonia removal from aqueous solution using natural chinese clinoptilolite. Separ. Purif. Technol. 2005, 44(3), 229–234.
[17] Booker, N.A.; Cooney, E.L.; Priestley, A.J. Ammonia removal from sewage using natural Australian zeolite. Water Sci. Technol. 1996, 34(9), 17–24. [18] Kesraoui-Oukl, S.; Cheeseman, C.; Perry, R. Effect of conditioning and treatment of chabazite and clinoptilolite prior to lead and cadmium removal. Environ. Sci. Technol. 1993, 27(6), 1108–1116. [19] Souto, G. D.B. Brazilian landfill leachate—Study of ammonia nitrogen removal by air stripping process. D. Sc. Thesis Graduate Program in Hydraulic Engineering and Sanitation. University of S~ ao Paulo. 371 pp. In Portuguese, 2009. Available at www.teses.usp.br/teses/disponiveis/18/18138/ tde-19022009-121756/publico/TeseGabrielSouto.pdf. (accessed Dec 2014). [20] Lei, L.; Li, X.; Zhang, X. Ammonium removal from aqueous solutions using microwave-treated natural Chinese zeolite. Separ. Purif. Technol. 2007, 58(3), 359–366. [21] Englert, A.H.; Rubio, J. Characterization and environmental application of a Chilean natural zeolite. Inter. J. Miner. Proc. 2005, 75(1–2), 21–29. [22] Karadag, D.; Koc, Y.; Turan, M.; Armagan, B. Removal of ammonium ion from aqueous solution using natural Turkish clinoptilolite. J. Hazard. Mater. 2006, 136(3), 604–609.
Copyright of Journal of Environmental Science & Health, Part A: Toxic/Hazardous Substances & Environmental Engineering is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
Removal of ammonia nitrogen from leachate of Muribeca municipal solid waste landfill, Pernambuco, Brazil, using natural zeolite as part of a biochemical system CECILIA MARIA M. S. LINS1, MARIA CRISTINA M. ALVES1,2, JUACYARA C. CAMPOS3, 1 and EDUARDO ANTONIO M. LINS1 FERNANDO T. JUCA FABRICIA MARIA S. SILVA1, JOSE 1
Solid Waste Research Group (GRS), Federal University of Pernambuco, Recife, Brazil Civil Engineering Department, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil 3 School of Chemistry, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil 2
The inadequate disposal of leachate is one of the key factors in the environmental impact of urban solid waste landfills in Brazil. Among the compounds present in the leachates from Brazilian landfills, ammonia nitrogen is notable for its high concentrations. The purpose of this study was to assess the efficiency of a permeable reactive barrier filled with a natural zeolite, which is part of a biochemical system for the tertiary treatment of the leachate from Muribeca Municipal Solid Waste Landfill in Pernambuco, Brazil, to reduce its ammonia nitrogen concentration. This investigation initially consisted of kinetic studies and batch equilibrium tests on the natural zeolite to construct the sorption isotherms, which showed a high sorption capacity, with an average of 12.4 mg NH4C. L¡1, a value close to the sorption rates found for the aqueous ammonium chloride solution. A permeable reactive barrier consisting of natural zeolite, as simulated by the column test, was efficient in removing the ammonia nitrogen present in the leachate pretreated with calcium hydroxide. Nevertheless, the regenerated zeolite did not satisfactorily maintain the sorption properties of the natural zeolite, and an analysis of their cation-exchange properties showed a reduced capacity of 54 meq per 100 g for the regenerated zeolite compared to 150 meq per 100 g for the natural zeolite. Keywords: Leachate, natural zeolite, ammonia nitrogen, sorption, sanitary landfill, solid waste.
Introduction Leachate from urban solid waste sanitary landfills is nowadays considered to be a major environmental problem because it can cause contamination of soil as well as surface and underground water. High concentrations of ammonia nitrogen (>1.000 mg.L¡1) are commonly found in leachate from Brazilian landfills,[1] which if not properly treated and disposed, can cause serious environmental problems of water and soil contamination, leading to severe impacts to receiving water bodies.[1,2] Earlier studies have shown that zeolites can beneficially substitute the cation-exchange resins used in effluent treatment. They are also capable of facilitating ionic exchange between the ammonium ion (NH4C) and other more biologically acceptable cations such as sodium (NaC), calcium
Address correspondence to Maria Cristina M. Alves, Federal University of Rio de Janeiro, 149 Athos da Silveira Ramos Avenue, I-203, Rio de Janeiro 21941-909, Brazil; E-mail: [email protected] Received December 22, 2014.
(CaC2), potassium (KC) or hydrogen (HC).[3–6] Zeolites have a high capacity for cation exchange, good chemical properties and physical strength and an excellent environmental compatibility. The zeolites are a class of adsorbents of major economic and social interest, especially with regard to the removal of metal cations and ammonium ions.[7] Another major benefit of the use of zeolites is the possibility of their regeneration for reuse. The Muribeca Solid Waste landfill, located in the State of Pernambuco in the northeast of Brazil, received around 3,600 tons per day of waste since 1985 until July, 2009.[8] The biochemical system from Muribeca Landfill leachate treatment system uses the set of three components: soil, plants and microorganisms to remove, degrade or isolate toxic effluents.[9–11] This system is characterised as a tertiary treatment process of decontamination, which occurs of different and concomitant ways based on two principles of effluent treatment techniques already consolidated: permeable reactive barrier (PRB) and phytoremediation through aquatic plants, as shown in Figure 1. PRB is composed of reactive material that can retain effluent pollutant chemically and/or physically as it gets through it preventing contamination downstream of the
Removal of ammonia nitrogen from landfill leachate using natural zeolite
981
Fig. 1. Schematic diagram of the biochemical system of Muribeca Landfill.
barrier. As a first attempt, the PRB was filled with clay and activated carbon with the aim of minimizing the concentrations of heavy metals resistant to primary and secondary treatments.[10] In an attempt to use this technique to reduce ammonia nitrogen concentration, a new search for reactive materials was made, among which natural zeolite was selected as a promising candidate. This study aims to evaluate the application of natural zeolite in a PRB for the tertiary treatment of leachate from the Muribeca Municipal Solid Waste Landfill in Pernambuco State, Brazil.
analysis using a Rigaku model RIX 3000 X-ray fluorescence spectrophotometer (The Woodlands, TX, USA). To complement the chemical characterization of the zeolite, the cation-exchange capacity (CEC) was determined according to the procedure described by EMBRAPA.[12] The mineralogical characteristics of the zeolite were determined by X-ray diffraction analyses using a Siemens XRD D5000 (Buffalo Grove, IL, USA) diffractometer with a graphite monochromator and a nickel (Ni) filter. The physical characterization of the zeolite followed the standards described by Brazilian Standards (ABNT),[13] for soil geotechnical characterization.
Materials and methods This investigation consisted of three stages. The first stage involved characterizing the natural zeolite and the raw leachate used in the study. In the second stage, preliminary studies and batch equilibrium tests were carried out to construct the sorption isotherms. Finally, the PRB efficiency was assessed for the leachate treatment using column tests simulating onsite conditions including regeneration of the zeolite.
Characterization of natural zeolite The natural zeolite used in the experiments was extracted from a deposit located in the county of Calingasta, Province of San Juan, Argentina, according to the company that supplied the material (Sol Minerales do Brasil). The chemical composition of the oxides in the studied zeolite was determined by semiquantitative
Characterization of the leachate The leachate used in the experiments came from the Leachate Treatment Plant of the Muribeca Landfill, 16 km from the city of Recife in the county of Jaboat~ ao dos Guararapes, Pernambuco State, in northeast Brazil. This was the largest landfill in operation in the Recife metropolitan region, covering an area of 64 ha; the landfill ceased operating in 2009. The leachate samples were collected in a flow box located behind the decanting pool of the Muribeca landfill treatment plant to obtain a homogeneous raw leachate with a reduced amount of suspended solids. After collection, physicochemical characterization of the samples was made in accordance with the Standard Methods for the Examination of Water and Wastewater,[14] listed in Table 1. The reported values are the mean values of four collection campaigns run in August, October and December 2007 and January 2008.
982
Lins et al.
Table 1. Main analytical methods used to characterize the leachate. Parameters
Analytical method
Reference
pH Alkalinity (mg CaCO3.L¡1) BOD5 (mgO2.L¡1) COD (mgO2.L¡1) Color (uH) Turbidity (NTU) Conductivity (mS.cm¡1) Ammonia Nitrogen (mg NH4C.L¡1) Chloride (mgCl¡.L¡1) Solids Series (mg.L¡1)
Potentiometric Titrimetric Manometric Titrimetric (Digestion with K2Cr2O7) PhotoColorimetric Nephelometric Electrical Conductance Electrometric (Ion selective electrode - Orion Model 720**) PhotoColorimetric Gravimetric
SMEWW 4500 B SMEWW 2320 B SMEWW 5210 SMEWW* 5220 C SMEWW 2120 C SMEWW 2130 B SMEWW 2510 B SMEWW 4500 - NH3 D Spectroquant 14897 - MERCK*** Adapted from SMEWW 2540 B, 2540 C, 2540 D.
*SMEWW: Standard Methods For The Examination Of Water And Wastewater.[14] **Orion (Thermo Scientific, Billerica, MA, USA). ***Merck (Darmstadt, Germany).
Preparation of leachate samples for tests In the experiments using natural zeolite, two different types of leachate were tested: raw leachate (L1) and leachate pretreated with calcium hydroxide (L2). Besides, an aqueous mono solution of ammonium chloride (AS) was tested to evaluate the affinity of the zeolite for adsorving this particular ion. The raw leachate (L1) was prepared as follows: after determining the ammonia nitrogen concentration, dilutions of the raw leachate were made with deionized water to obtain different concentrations of ammonia nitrogen. The L2 was obtained from pretreatment of the L1 with calcium hydroxide in order to remove part of organic matter from the leachate. This pretreatment was undertaken in a test jar in which 12 L of L1 were shaken together with calcium hydroxide (35 g Ca(OH)2 per L) for 10 min at 120 rpm, after which the pH of the pretreated leachate was adjusted with a solution of HCl (6 mol.L¡1) to a value of around 8.5, similar to the L1. Dilutions were then made with deionized water, adopting the same procedure as with L1. For the aqueous ammonium chloride solution (AS), a solution was prepared with deionized water and ammonium chloride to obtain samples with different ammonia nitrogen concentrations for the experiments. Ammonia nitrogen concentration was 1,532 mg L¡1 in L1 and 1,270 mg L¡1 in L2. Preliminary studies Initial tests for assessing the ammonia nitrogen sorption by the zeolite were performed to determine the optimum conditions for the zeolite–ammonia nitrogen system to reach equilibrium. Six grams of zeolite were weighed and placed into 125-mL Erlenmeyer flasks to which 100 mL of the solutions (L1, L2 or AS) were added to provide a concentration around 340 mg NH4C.L¡1. For each solution, 11 Erlenmeyer flasks were prepared (zeolite C solution) and placed in an incubator with shaking at 120 rpm and a constant
temperature of 28 C. At preset intervals, varying from 3 min to 24 h, aliquots of the supernatants were collected from the zeolite and immediately analyzed for ammonia nitrogen concentration, pH, conductivity and chemical oxygen demand (COD). These analyses adopted the same procedures as those used for characterizing the leachate. Batch equilibrium tests The sorption of the zeolite was evaluated using batch equilibrium tests in accordance with the EPA/530/SW-87/ 006-F standard.[15] At this stage in the experiments, a series of suspensions was prepared in 125 mL Erlenmeyer flasks, each consisting of six g of zeolite and 100 mL of solutions (L1, L2 or AS) to provide concentrations varying between 30 and 1,700 mg NH4C. L¡1. Control samples were prepared using 100 mL of the contaminants at the various ammonia nitrogen concentrations without zeolite for evaluating loss by evaporation. The samples were placed in the incubator and shaken at 120 rpm at a constant 28 C temperature. After 24 or 72 h the solutions were removed, samples of the supernatants were taken and the ammonia nitrogen concentration, pH, conductivity and COD were determined. Column experiments and regeneration As the PRB with natural zeolite played the role of a final polishing treatment, this stage of experiments was only carried out with the pretreated leachate (L2). In this test, the sample was fitted into the permeameter (Tri-Flex System 2 - Soil Test, ELE International, Bedfordshire, UK) to simulate conditions in the onsite PRB. The RPB simulation was carried out into a PET cylinder 10 cm in diameter and 9 cm high were placed 715 g of dry zeolite so field specific weight and compaction conditions were met. The zeolite sample was then saturated with distilled water. Afterwards, a downward flow of the leachate-
983
Removal of ammonia nitrogen from landfill leachate using natural zeolite Table 2. Characterization of raw leachate collected from Muribeca Landfill used in this work. Parameters pH Alkalinity (mg CaCO3.L¡1) BOD5 (mgO2.L¡1) COD (mgO2.L¡1) BOD5/COD Color (uH) Turbidity (NTU) Conductivity (mS.cm¡1) Ammonia Nitrogen (mg NH4C.L¡1) Chloride (mgCl¡.L¡1) Total Solids (mg.L¡1) Total Dissolved Solids (mg.L¡1) Total Suspended Solids (mg.L¡1)
Mean values
Minimum values
Maximum values
8.59 7243 2781 3951 0.70 9558 170 19.90 1453 411 10341 8530 1811
8.46 5867 2320 3307 0.67 8645 137 18.24 1125 227 8890 7022 1280
8.70 7838 3190 4735 0.74 10550 193 21.33 1708 760 11469 9524 2082
solution was applied through the test sample and the effluent was periodically collected in graduated receivers. Shortly after each collection, the ammonia nitrogen concentration, pH and conductivity of the effluents were determined. The test should end when the ammonia nitrogen concentration was constant and approximately the same as the initial concentration of the contaminant. The second part of this test was the regeneration of the zeolite. This process was done using a 1 mol.L¡1 solution of sodium chloride (NaCl) as a percolating liquid, with the pH adjusted to within 10–11 with a 1 mol.L¡1 sodium hydroxide solution,[6] and adopted the same column test procedure described here.
Results and discussion Characterization of natural zeolite The zeolite was composed mainly of oxides, mostly SiO2, at 58.16%, followed by CaO, 9.9%; Al2O3, 7.67%; Fe2O3, 6.63%; and K2O, 3.07%. All other oxides were present in amounts less than 1%: TiO2, 0.965%; P2O5, 0.905%; BaO, 0.245%; SrO, 0.235%; MgO, 0.17%; ZrO2, 0.16%; MnO, 0.105%; other oxides, 0.175%. Loss on ignition was 11.62%. Analysis of X-ray diffraction result together with analysis of the oxides present in the zeolite indicated a clinoptilolite zeolite type. The CEC value of 130 meq per 100 g found for this zeolite is within the range obtained by other researchers, as follows: 62 to 229 meq per 100 g.[6, 16-18]
leachates from Brazilian Municipal Solid Waste (MSW) landfills. Preliminary tests It was found that the removal of the ammonia nitrogen from liquid phase occurred quickly with the three solutions studied (L1, L2 and AS), up to approximately 4 h of shaking, as shown in Figure 2. From this point onward, the removal efficiency values tended to stabilize as the contact time was increased, almost reaching a steady state between six and eight hours of shaking. After 24 h of shaking, it was still possible to detect a small reduction in the ammonia nitrogen concentration, which was considered negligible. The drop in the removal efficiency for ammonia nitrogen at the end of the experiment indicated a possible saturation of the zeolite by ammonium ions both on the outside surface and in the pores of the clinoptilolite.[16] Significantvariations in the concentration of ammonia nitrogen were not found in the tested control samples. This fact
Characterization of leachate Table 2 shows the complete characterization of the raw leachate. Values of the analyzed parameters are in accordance with Souto[19] in his comprehensive review of the published values of these parameters for
Fig. 2. Removal efficiency of ammonia nitrogen by the zeolite versus contact time.
984
Lins et al.
ensures that removal occurred just due to the presence of natural zeolite. The efficiency of ammonia nitrogen removal by the zeolite was lower for L2 than for L1, with the former reaching approximately 45% after 6 h, whereas the latter reached 60% by this time. The removal efficiency obtained with AS was above 75% after 6 h, reaching a little more than 80% after 24 h. Wang et al.[3] also found that higher adsorption capacities were obtained with an aqueous ammonium chloride solution than with leachate. On the other hand, the difference between the removal efficiency of the L1 and L2 was probably due to calcium left on the precipitation process in L1, which competed for the same sites with ammonia. Batch equilibrium Although the preliminary results yielded two sorption isotherms, i.e., for 24 and 72 h, for each solution (L1, L2 and AS), a minimum equilibrium period of 24 h was adopted to fulfill the US EPA standard,[15] although the preliminary results showed that 6 hours were enough to reach the equilibrium. Experimental data were adjusted according to the nonlinear Freundlich [Eq. (1)] and Langmuir [Eq. (2)] models, as linear approximations did not provide a good fit to the data. q D Kp CeN
(1)
where Kp (partition coefficient) is proportional to the sorption capacity and N is the slope of the curve that reflects the intensity of sorption as concentration increases. qD
½a b Ce ½ 1 C a Ce
(2)
where a is a constant of sorption and b is the maximum rate of sorption of chemical species of interest. The sorption curves obtained at 24 and 72 h are shown in Figure 3 for L1, in Figure 4 for L2 and in Figure 5 for AS. These figures show that the Langmuir isotherm better fitted the experimental data for all experiments. From the above data, the sorption parameters were calculated for the two models in question, namely, the partition coefficient (Kp) and Freundlich sorption constant (N) for the Freundlich model and the maximum sorption rate (b) and Langmuir sorption constant (a) for the Langmuir model. The values of these parameters are shown in Table 2 along with results previously reported in the literature. The coefficient of determination (R2) is also presented As the Langmuir model yielded a much better fit of the experimental data for AS, L1 and L2, subsequent analysis was focused on the Langmuir parameters b and a:
Fig. 3. Sorption isotherms with zeolite and raw leachate (L1) obtained after (a) 24 h and (b) 72 h.
The great majority of the published data shown in Table 3 deal with ammonium monosolutions except for the data presented in Wang et al.,[3] which concerns a mixture of leachate and an aqueous solution of ammonium chloride (AS). With respect to time effect on sorption parameters, the data obtained with AS in the present work indicate that 24 h was the ideal time for removing ammonia nitrogen, obtaining a maximum sorption rate of 13.69 mg NH4C.g¡1. For the 72-h time, a slight reduction in the sorption rate was found, resulting in 12.98 mg NH4C.g¡1. In contrast, both L1 and L2 showed higher values for b and a for the 72-h test. Nevertheless, as the differences between these values was less than 10% for all tests, it appeared reasonable to use 24-h tests as the standard for analysis. Analysis of the results from AS tests revealed that the values of the maximum sorption capacity (b) were very
Removal of ammonia nitrogen from landfill leachate using natural zeolite
985
Fig. 4. Sorption isotherms with zeolite and leachate pretreated with calcium hydroxide (L2) obtained after (a) 24 h and (b) 72 h.
Fig. 5. Sorption isotherms with zeolite and an aqueous ammonium chloride solution (AS) obtained after (a) 24 h and (b) 72 h.
similar to those obtained by Lei et al.[20] and Englert and Rubio,[21] although different from the results presented by Saltali et al.[5] Nevertheless, all these values are of the same order of magnitude. However, the value presented in Sarioglu[6] is almost two times that found in this study, which may be explained by the different mineralogical components of the natural zeolite used in their study (45% clinoptilolite, 35% mordenite and 20% other components). It was also found that the maximum sorption rates (b) obtained for L2 were slightly less than the L1 values. The reason for this small difference can be attributed to the treatment of L2, resulting in a larger quantity of calcium ions in solution than in L1. This may therefore have contributed to increased competition for exchangeable sites on the zeolite and reduced the adsorption rate of the ammonia nitrogen. Values of the sorption rates obtained for L1, L2 and AS, which varied from 10.53 mg NH4C.g¡1 for L2 to 13.69 mg NH4C.g¡1 for AS, were similar in the 24-hour test. In the 72-hour tests, these values were even
more similar, around 12 mg NH4C.g¡1 for all three tests (AS, L1 and L2). This fact is very important because it can be justified by the high affinity of the zeolite for the ammonium ions, in accordance with the order of selectivity: CsC> RbC> KC> LiC> NH4C> NaC> BaC2> CaC2.[5]
Column experiments Figure 6 shows the breakthrough curve obtained with the first passage of L2 through the zeolite, maintaining an average permeability of 1.48 £ 10¡4 cm.s¡1. The main point of the column test was the analysis of this breakthrough curve, and it is generally close to an “S” shape in sorption processes. However, several parameters such as initial pollutant concentration, flow rate, adsorption mechanism and column diameter can affect the shape of this curve.[6] It can be observed in the same figure that the C/Co ratio was very low until the tenth void volume, corresponding to
986
Lins et al.
Table 3. Sorption parameters in the literature compared to results of the present study. Freundlich model Source
Kp (mg.g¡1)
Wang et al.[3] Saltali et al.[5] Sarioglu[6] Du et al.[16] Lei et al.[20] Englert and Rubio[21] Karadag et al.[22]
0.43 0.93 2.23 1.36 5.09 — 0.61
Sorption test (AS) 24 h Sorption test (AS) 72 h Sorption test (L1) (24 h) Sorption test (L1) (72 h) Sorption test (L2) 24 h Sorption test (L2) 72 h
1.04 1.53 0.54 0.72 0.65 0.74
N (L.g¡1)
Langmuir model R2
0.458 0.98 0.488 0.96 0.380 0.98 0.279 0.99 0.220 0.99 — — 0.517 0.95 Results from present study 0.363 0.99 0.354 0.98 0.446 0.94 0.443 0.90 0.413 0.96 0.424 0.94
B (mg.g¡1)
a (L.mg¡1)
R2
2.13 9.64 25.77 — 13.74 12.3 8.12
0.182 0.055 0.018 — 0.23 — 0.029
0.99 0.96 0.98 — 0.95 0.97 0.92
13.69 12.98 11.36 12.82 10.53 12.05
0.008 0.038 0.007 0.012 0.009 0.011
0.97 0.99 0.98 0.99 0.99 0.99
16 h of testing, indicating the high sorption of the ammonia nitrogen by the zeolite. From this point on, the C/Co ratio began to increase, approaching the saturation of the zeolite. The column test was terminated after 159 h, due to operating limitations, reaching around 70% (C/Co D 0.7) saturation of the zeolite in this period. The reduction in contaminant removal efficiency when the L2 seeped through the zeolite was as expected, because the zeolite has a saturation point where the sorption capacity of the ammonia nitrogen is reduced or practically null. This fact was also observed during the batch equilibrium tests. Karadag et al.,[22] in their study of leachate with an ammonia nitrogen concentration of 200 mg.L¡1 at pH 8.3, found that the saturation of the zeolite occurred after 164 h of testing, and this time could be altered with pH variation, due to the form of ammonia nitrogen that may be present (dissociated ammonia,
NH4C, which is in the ionic form, and undissociated ammonia, NH3, which is also known as free ammonia), depending on the pH.[1]
Fig. 6. Breakthrough curve of ammonia nitrogen through zeolite bed with pretreated leachate (L2).
Fig. 7. Concentration of ammonia nitrogen during zeolite-regeneration process using NaCl solution.
Regeneration The potential for regenerating the zeolite after saturation with ammonium ions by leachate passage was tested. Figure 7 shows the data obtained from the zeolite-regeneration process. In the initial flow of sodium chloride solution, the ammonia nitrogen concentration reached a value of over 500 mg.L¡1 with only two void volumes passage through the column. This fact may be due to the initial displacement of calcium ions (data not measured), after that, the sodium ions begun to displace ammoniums ions. After
Removal of ammonia nitrogen from landfill leachate using natural zeolite reaching a peak value, the ammonia nitrogen concentration began to decrease and finally stabilized after 50–60 void volumes, corresponding to approximately 17 h of flow. Ammonia nitrogen concentration dropped to less than 1 mg.L¡1, thereby indicating the end of the zeoliteregeneration process. Du et al.[16] noted that during the regeneration process the highest peaks of ammonia nitrogen concentration (400–500 mg.L¡1) were obtained between 2.5–5 void volumes, and the process was concluded after 15–20 void volumes. Karadag et al.[22] found that the removal of ammonia nitrogen was fast in the first 30 min of regeneration, and in this study the total regeneration occurred after 15 h using 20 g NaCl.L¡1 and 23 h using 10 g NaCl.L¡1. After the regeneration process, a sample of the zeolite was removed and the new cation exchange capacity (CEC) was analyzed to check the efficiency of this regeneration. The natural zeolite CEC was 130 meq per 100 g, and after the regeneration it was 54 meq per100 g, 58% less than the raw natural zeolite, showing that the regeneration process utilized here was not so efficient. One hypothesis explaining this low efficiency is that the number of regeneration cycles was not satisfactory for an efficient cation exchange between the ammonium ions of the zeolite and the sodium ions in the regeneration solution or, as a second hypothesis, that the concentration of the regeneration solution used was not optimal. Finally, the organic matter, which was also adsorbed from the leachate, may be causing decreased zeolite CEC. Sarioglu[6] reported in experiments performed on domestic wastewater that there was a drop of 31.52% in the adsorption capacity of the zeolite after regeneration. However, experiments using synthetic ammonium solution showed that the regeneration process adopted in their experiments was efficient for regenerating the zeolite, mainly in the first regeneration cycles, where an increase was found in the adsorption capacity for ammonia nitrogen.[16]
Conclusions Considering the tests performed on a bench scale, the use of a reactive barrier consisting of natural zeolite is promising as a final polishing system in treating the leachate from the Muribeca landfill. From the kinetic tests, it was found that the ammonia nitrogen was removed quickly, especially in the first six hours of shaking, and that the rate of removal later decreased and tended to stabilize. With regard to the natural zeolite, it showed a high sorption capacity for the ammonia nitrogen present in the leachates, with an average of 12.4 mg NH4C.L¡1, a value close to the sorption rates found for the aqueous ammonium chloride solution. This indicates a high selectivity of the ammonium ion by the zeolite, as the leachate has a number of other ions that compete with ammonium ions for adsorption sites.
987
A permeable reactive barrier consisting of natural zeolite, as simulated by the column test, was efficient in removing the ammonia nitrogen present in the leachate pretreated with calcium hydroxide. Nevertheless, the regenerated zeolite did not satisfactorily maintain the sorption properties of the natural zeolite, and an analysis of their cation-exchange properties showed a reduced capacity of 54 meq per 100 g for the regenerated zeolite compared to 150 meq per 100 g for the natural zeolite.
Acknowledgments We also thank all the staff of the Solid Waste Group of the Federal University of Pernambuco, GRS/UFPE for their technical support.
Funding The authors thank the research network PROSAB/ FINEP/CNPq and CNPq through Edital Universal – Edital 2006 for financial support.
References [1] Campos, J.C.; Moura, D.; Costa, A.P.; Yokoyama, L.; Araujo, F. V.F.; Cammarota, M.C., Cardillo, L. Evaluation of pH, alkalinity and temperature during air stripping process for ammonia removal from landfill leachate. J. Environ. Sci. Health Pt. A 2013, 48(9), 1105–1113. [2] Liu, J.; Luo, J.; Zhou, J.; Liu, Q.; Qian, G.; Xu, Z.P. Inhibitory effect of high-strength ammonia nitrogen on bio-treatment of landfill leachate using EGSB reactor under mesophilic and atmospheric conditions. Bioresour. Technol. 2012, 113(3), 239–243. [3] Wang, Y.; Liu, S.; Xu, Z.; Han, T.; Chuan, S.; Zhu, T. Ammonia removal from leachate solution using natural Chinese clinoptilolite. J. Hazard. Mater. 2006. 136(3), 735–740. [4] Karadag, D.; Tok, S.; Akgul, E.; Turan, M.; Ozturk, M.; Demir, A. Ammonium removal from sanitary landfill leachate using natural Gordes clinoptilolite. J. Hazard. Mater. 2008. 153(1–2), 60–66. [5] Saltali, K.; Sari, A.; Aydin, M. Removal of ammonium ion from aqueous solution by natural turkish (Yildizeli) zeolite for environmental quality. J. Hazard. Mater. 2007, 141(1), 258–263. [6] Sarioglu, M. Removal of ammonium from municipal wastewater using natural Turkish (Dogantepe) zeolite. Separ. Purif. Technol. 2005. 41(1), 1–11. Comparison of different physico[7] Cotman, M.; Gotvajn, A.Z.; chemical methods for the removal of toxicants from landfill leachate. J. Hazard. Mater. 2010, 178(1–3), 298–305. [8] Maciel, F.J.; Juc a, J. F. T. Evaluation of landfill gas production and emissions in a MSW large-scale experimental cell in Brazil. Waste Mgmt. 2011, 31(5), 966–977. [9] Maciel, F.J.; Juc a, J.F.T. Biogas recovery in an experimental MSW cell in Brazil: lessons learned and recommendations for CDM projects. Greenhouse Gas Measure. Mgmt. 2013, 2(4), 186–197. [10] Alves, M.C.M.; Beltr~ ao, K.G.Q.; Juc a, J.F.T. Assessment of metals sorption in the permeable reactive barrier of the leachate treatment system of Muribeca Landfill, Recife, Brazil. In: 5th International Congress on Environmental Geotechnics, Cardiff -
988
[11]
[12]
[13]
[14]
[15]
[16]
Lins et al. Wales, United Kingdom. Jun 26–30, 2006; Thomas, H R. Editor; Thomas Telford Ltd.: London, 2006. Brito, K.G.Q.; Juc a, J.F.T. Alternativa para tratamento de chorume em aterros sanit arios - sistema de barreira bioquímica. In: XI Simposio Luso Brasileiro de Engenharia Sanit aria e Ambiental, Natal, Brazil. Mar 28–Apr 2, 2004; ABES: Rio de Janeiro, 2004. In Portuguese. EMBRAPA (Brazilian Company of Agricultural Research). Soil Analysis Handbook. 2nd edition, Brazilian Company of Agricultural Research: Rio de Janeiro, 2011. In Portuguese. ABNT (Brazilian Association for Technical Standards): NBR 6508 – Determination of Soil Particle Specific Mass. Brazilian Association for Technical Standards: Rio de Janeiro, 1984. In Portuguese. APHA. Standard Methods for the Examination of Water and Wastewater, 20th ed. APHA/AWWA/WEF: Washington, DC, 1998. US EPA. United States Environmental Protection Agency. BatchType Procedures for Estimating Soil Adsorption of Chemicals. Office of Solid Waste and Emergency Response: Washington, DC, 1992. Du, Q.; Liu, S.; Cao, Z.; Wang, Y. Ammonia removal from aqueous solution using natural chinese clinoptilolite. Separ. Purif. Technol. 2005, 44(3), 229–234.
[17] Booker, N.A.; Cooney, E.L.; Priestley, A.J. Ammonia removal from sewage using natural Australian zeolite. Water Sci. Technol. 1996, 34(9), 17–24. [18] Kesraoui-Oukl, S.; Cheeseman, C.; Perry, R. Effect of conditioning and treatment of chabazite and clinoptilolite prior to lead and cadmium removal. Environ. Sci. Technol. 1993, 27(6), 1108–1116. [19] Souto, G. D.B. Brazilian landfill leachate—Study of ammonia nitrogen removal by air stripping process. D. Sc. Thesis Graduate Program in Hydraulic Engineering and Sanitation. University of S~ ao Paulo. 371 pp. In Portuguese, 2009. Available at www.teses.usp.br/teses/disponiveis/18/18138/ tde-19022009-121756/publico/TeseGabrielSouto.pdf. (accessed Dec 2014). [20] Lei, L.; Li, X.; Zhang, X. Ammonium removal from aqueous solutions using microwave-treated natural Chinese zeolite. Separ. Purif. Technol. 2007, 58(3), 359–366. [21] Englert, A.H.; Rubio, J. Characterization and environmental application of a Chilean natural zeolite. Inter. J. Miner. Proc. 2005, 75(1–2), 21–29. [22] Karadag, D.; Koc, Y.; Turan, M.; Armagan, B. Removal of ammonium ion from aqueous solution using natural Turkish clinoptilolite. J. Hazard. Mater. 2006, 136(3), 604–609.
Copyright of Journal of Environmental Science & Health, Part A: Toxic/Hazardous Substances & Environmental Engineering is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
