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Australian Journal of Basic and Applied Sciences, 5(12): 1365-1370, 2011 ISSN 1991-8178

Review on , Exchange and Methods for Landfill Treatment

Amin Mojiri

Young Researchers Club, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran.

Abstract: Urban landfill leachate is a high strength characterized by high concentrations of recalcitrant organic compounds, ammonia and, increasingly, arsenic. The aims of this study were the review on membrane bioreactor, and adsorption method for landfill leachate treatment. Membrane bioreactor (MBR) can be used for wastewater and landfill leachate treatment. The most important operating parameters in MBR which have an impact on nutrient removal and on fouling propensity, are the solid (or ) retention time (SRT) and hydraulic retention time (HRT). Ion- exchange/adsorption processes can be developed as post treatment to a membrane bio-reactor (MBR) because of the very high degree of clarification possible. has a high cation exchange capacity (CEC), and thus a high potential for an application for the removal of ammonia nitrogen from wastewater. Many investigations showed that the ion exchange method, using zeolite and ion exchange resin could be reducing nitrogen, phosphorus, organics (COD and BOD5) and heavy from landfill leachate. Activated carbon is considered as one of the most effective adsorbents. The application of activated carbon adsorption is effective for the removal of non-biodegradable compounds from landfill leachate.

Key words: Activated carbon, Ion exchange, Leachate, Membrane Bioreactor, Zeolite

INTRODUCTION

Landfill are reflected one of the kinds of wastewater with the utmost environmental influence. The most serious features of leachate are connected of the high concentrations of some contaminants. Urban landfill leachates enclose contaminants which can be separated into four key groups including dissolved and inorganic compound like , potassium, sodium, ammonium, calcium, , sulphates, chlorides, iron and like nickel, lead, copper, chromium, cadmium, zinc, xenobiotic organic materials (Aziz et al., 2010; Tengrui et al., 2007). Table 1 and 2 display characteristics of leachate generated from decomposition of municipal solid wastes in developing countries and Landfill Leachate classification vs. age, respectively. When moisture enters the refuse in a landfill generation of leachate occurs, dissolves the pollutants into liquid phase and becomes adequate to begin a liquid flow. Leachate varies from one landfill to another with fluctuations that depend on short and long-terms because of variations in climate, hydrogeology and waste composition. Because of this, improvements in landfill engineering are aimed at reducing leachate production, collection and treatment prior to discharge (Visvanathan et al., 2007). Urban landfill leachate is a high strength wastewater characterized by high concentrations of recalcitrant organic compounds, ammonia and, increasingly, arsenic (Englehardt et al., 2006). Urban landfill leachate has been one of the major problem for environment because of high organic, inorganic and heavy content and toxicity characteristics. In the operations, leachate treatment is both a very difficult and expensive process (EPA, 1995). In general, available landfill leachate treatment options include: (1) spray on adjacent grassland; (2) recirculation of leachate through the landfill; (3) co-treatment of and leachate; (4) leachate evaporation using landfill-generated methane as fuel; and (5) biological or physical/chemical treatment (4). The ability of leachate to contaminate rivers and lakes is expressed by the BOD5 which approximation the potential for use of oxygen. In fact, this potential is COD. The COD value is usually higher than BOD5. High COD and NH3-N content, high COD/BOD5 ratio and the attendance of heavy metal can cause difficulties in biological treatment of landfill leachate (Aziz et al., 2011; Park et al., 1999). One selection principles of leachate treatment ways, which depends on the type of deposited wastes and landfill age. In leachate-free volatile fatty acids signified the greatest group of organics, in the first years of landfill operation, then this portion displayed a fast reduction increasing age of the landfill. Ammonium nitrogen increased in leachate along with landfill age. It was detected that in mature landfill leachate this content was in the range of 2000-3000 mg NNH4/L. The most firm group with increasing age was a fulvic-like material with a comparatively high carboxyl and aromatic hydroxyl group density. Particular organic compounds recognized in

Corresponding Auhtor: Amin Mojiri, young Researchers Club, Isfhan (Khorasgan) Branch, Islamic Azad Unviersity, Isfaha, Iran. E-mail: [email protected] 1365 Aust. J. Basic & Appl. Sci., 5(12): 1365-1370, 2011 the leachate are phthalates, pesticides, BTEX, furans, halogenated aromatics, polycyclic aromatic hydrocarbons (PHAs) and napthalensulfonates (Klimiuk and Kulikowska, 2004).

Table 1: Characteristics of leachate generated from decomposition of municipal solid wastes in developing countries (UNEP, 2005). Parameter Range of Values (mg L-1) Parameter Range of Values (mg L-1) pH 4.5 to 9 Organic N 10 to 4250

Alkalinity (CaCO3) 300 to 11500 Ammonia NH3 30 to 3000 - BOD5 20 to 40000 Nitrite Nitrogen NO2 0 to 25 - COD 500 to 60000 Nitrate Nitrogen NO3 0.1 to 50 Calcium 10 to 250 Total Nitrogen 50 to 5000 Chloride (Cl-) 100 to 5000 Total Phosphate 0.1 to 30 2- Potassium 10 to 2500 Sulphate (SO4 ) 20 to 1750 Sodium 50 to 4000 Manganese 0.03 to 65 Magnesium 40 to 1150 Total Iron 3 to 2100 TDS 0 to 42300 Copper 4 to 1400 TSS 6 to 2700 Lead 8 to 1020 Hardness 0 - 22800 Zinc 0.03 to 120

Table 2: Landfill Leachate classification vs. age (Ngo et al., 2008). Parameter Young Intermediate Old Age (years) <5 5-10 >10 pH 6.5 6.5-7.5 >7.5 COD (mg/L) >10000 4000-10000 <4000

BOD5/COD >0.3 0.1-0.3 <0.1 5-30% VFA + Humic and Organic compound 80% volatile fat acids (VFA) Humic and Fulvic Acid Fulvic Acid Heavy metals Low-Medium Low Low Biodegradability Important Medium Low

Landfill leachate treatment, especially in municipal areas, has received significant attention in recent years. However, high COD and ammonium content, high COD/BOD ratio and also presence of toxic chemicals such as heavy metal ions present unique difficulties in biological treatment of landfill leachate. Combinations of physical, chemical and biological methods are used for landfill leachate treatment, since it is difficult to obtain satisfactory treatment efficiencies by either one of these methods alone. Physical/chemical treatment processes are often required for treatment of mature and recalcitrant leachates. Flocculation/precipitation, activated carbon adsorption, ion exchange, membrane , and oxidation technologies have been reported (Englehardt et al., 2006).

Fig. 1: Landfill leachate.

In this study the membrane bioreactor, ion exchange and adsorption for landfill leachate treatment methods has been investigated.

Membrane Bioreactor (MBR): The membrane (MBR) technology is the combination of together with micro or ultrafiltration membranes (MF or UF) with pore sizes ranging typically between 10 nm to 0.5 μm. In conventional activated sludge treatment plant, the membrane filtration process replaces mainly the final step treatment achieved by gravity only, while the activated sludge bioreactor is keep separated from the UF treatment. The membrane also provides disinfection by eliminating bacteria and virus producing high quality, suspended-solids free effluent (Battilani et al., 2009). Aust. J. Basic & Appl. Sci., 5(12): 1365-1370, 2011

MBR take only half the land area of conventional activated sludge processes, and sludge production is similarly halved. In addition, the MBR maintains high biomass concentration in the reactor, which could reduce HRT permitting a higher rate of organic and nutrient removal (Chae et al., 2007). Advantages of the MBR include better control of biological activity, effluent that is free of bacteria and pathogens, smaller plant size, and higher organic loading rates (Cicek, 2003). Treatment of domestic urban wastewater using membrane bioreactor (MBR) process is popular as effluent standards are evolving in stringency and current water conservation measures is giving a strong impetus for water reuse applications. This traditional MBR system usually removes both organic matter and nitrogen from water but it may fail to achieve the required water quality when exposed to peak and variable organic load as the efficiency of a MBR system depends on operating parameters. The most important operating parameters in MBR which have an impact on nutrient removal and on fouling propensity, are the solid (or sludge) retention time (SRT) and hydraulic retention time (HRT) (Johir et al., 2011).

Ion Exchange Treatment: The solid ion exchange particles can be classified as natural-inorganic particles () and synthetic- organic resins, which were developed from high-molecular-weight polyelectrolytes (Bashir et al., 2010). Development of ion exchange resins and characterization of naturally occurring ion exchange materials has demonstrated a wide range of possible applications of the technology in water and (Wang and Peng, 2010). The ion-exchange method offers a number of advantages including the ability to handle shock loadings and operate over a wider range of . Ion-exchange/adsorption processes can be developed as post treatment to a membrane bio-reactor (MBR) because of the very high degree of clarification possible. Further, processes using selective ion-exchangers are ideal candidates for reduction of dissolved ammonia and phosphate to near-zero levels provided that the sorbent is ammonia and/or phosphate selective, cost effective and amenable to efficient regeneration and reuse. It has been demonstrated that clinoptilite is effective in the removal of ammonia (Johir et al., 2011).

Zeolite: Some of the most popular and widely available natural ion exchangers are zeolites, which consist of an aluminosilicate molecular structure with weak cationic bonding sites (Guisnet and Gilson, 2002). Natural zeolites have been avoided in high purity processes or where consistency is vital because of irregularities and impurities of the material (Hegger, 2010). Zeolites are hydrated alumino silicates comprising silica and aluminium tetrahedra which are mutually bound by chemical covalent bonds with common oxygen atoms (Thornton et al., 2007). Zeolites are three-dimensional microporous, crystalline solids with well-defined structures that contain aluminum, silicium and oxygen in their regular framework. The most common use for zeolites is as an ion exchange material in many applications. Zeolite has a high cation exchange capacity (CEC), and thus a high potential for an application for the removal of ammonia nitrogen from wastewater. And, zeolite has shown a great capacity for metal adsorption (Cu, Cd, Pb and Zn) and that property can be useful for removing toxics for microorganisms in the biological processes. Zeolite can be also useful as a microbial support both in aerobic and anaerobic processes of different . The ion exchange properties of natural zeolites are well known. Recycling and reuse of ammonium loaded zeolites as slow release fertilizers have been studied, and the technique is well documented. Zeolite has also been introduced as an adsorbent in the advanced oxidation processes (AOPs) to increase the removal efficiency of a target compound (Kim et al., 2009).

The Synthetic Ion Exchange Resin: Natural zeolites (crystalline alumino silicates) were the first ion exchangers used commercially, however, zeolites had been completely replaced with synthetic resins (consists of a cross linked matrix where charged functional groups are attached by covalent bonding) in modern applications due to their faster exchange rates, longer life and higher capacity. Currently, there are no limitations for the commercialization of ion exchange resin varieties due to their polymer matrices, functional groups, capacity and porosity which are controllable during manufacturing. The cation ion exchange resins are copolymers typically made of styrene and divinyl benzene (DVB). Styrene acts as the backbone or chain, while DVB acts as a crosslinker. Strong acid - + cation resins function with the producing a sulfonic (-SO3 H ). Sulfonate group (- SO3-) is a fixed functional group. H+ is mobile exchangeable ion (Bashir et al., 2010).

Adsorption Method: Adsorption is a natural process by which of a dissolved compound collect on and adhere to the surface of an adsorbent solid. Adsorption occurs when the attractive forces at the carbon surface overcome the attractive forces of the liquid (CARBTROL® Corporation, 1992).

1367 Aust. J. Basic & Appl. Sci., 5(12): 1365-1370, 2011

Activated Carbon: Activated carbon is considered as one of the most effective adsorbents, especially for substances containing refractory organic compounds that resist biodegradation and persist in the environment. It can be used as a standalone treatment method as well as in tandem with biological, ozonation and limestone-based methods. In general, the application of activated carbon adsorption is effective for the removal of non-biodegradable compounds from landfill leachate (Blaney et al., 2007). Adsorption using activated carbon is also a well- recognized means of leachate treatment. Activated carbon is considered as one of the most effective adsorbents, especially for substances containing refractory organic compounds that resist biodegradation and persist in the environment. It can be used as a standalone treatment method as well as in tandem with biological, ozonation and limestone-based methods. In general, the application of activated carbon adsorption is effective for the removal of non-biodegradable compounds from landfill leachate (Lim et al., 2009). The specific capacity of a granular activated carbon to adsorb organic compounds is related to: molecular surface attraction, the total surface area available per unit weight of carbon, and the concentration of contaminants in the wastewater stream. The basic instrument for evaluating activated carbon use is the adsorption isotherm. The isotherm represents an empirical relationship between the amount of contaminant adsorbed per unit weight of carbon and its equilibrium water concentration. This relationship can be expressed in the form:

X/M = KC1/n (1)

Where:

X/M = Amount of contaminant adsorbed per unit weight of carbon. C = Concentration of contaminant in the water stream. K,n - Empirical constants particular to the contaminant.

The constants K and n are determined by plotting experimental results on log-log paper with the concentration of contaminant on the X axis and the amount of contaminant adsorbed on the y axis. The slope of the line developed is equal to 1/n and the intercept equal to K. These dimensionless, empirical constants are useful for comparing the adsorption capacities for different compounds or for assessing the adsorption capacities of various activated carbons (CARBTROL® Corporation, 1992).

Clay: Activated carbon has been the most widely used adsorbent because of its high capacity for the adsorption of heavy metals. However, due to the difficulty and expense involved in regeneration, clays are being considered as alternative low cost adsorbents. Studies show that the adsorption capabilities of clays are due to a net negative charge on the silicate which is neutralized by the adsorption of positively charged cations such as cationic dyes, heavy metals, etc. The other main reason for the high adsorption capacity of clays is the large surface areas ranging up to 800 mg2.g-1 (Chaari et al., 2011).

Review on some Investigations about Landfill Leachate and Wastewater Treatment by Ion Exchange and Adsorption Methods: Moton et al., (2010) investigated assessing the net benefits of using wastewater treated with a membrane bioreactor for irrigating vegetables in Crete. These results showed that the net benefit of treating wastewater with an MBR and using the to irrigate vegetables ranges from about 0.02 € /m3 to 2 € /m3 as water scarcity increases. Their results should be helpful in guiding analysts in Greece and other arid countries wishing to evaluate the financial viability of alternative methods of treating wastewater for use in agriculture. Foul et al., (2009) investigated the primary treatment of anaerobic landfill leachate using activated carbon and limestone: batch and column studies. Activated carbon-limestone mixture was used as a primary treatment process. More than 86% of colour and COD, 95% of iron, and 48% of ammoniacal nitrogen were removed by a mixture of activated carbon and limestone (15:25 by volume) in the batch study compared with 70, 80 and 90% respectively, by column study on the first five days. Thornton et al., (2007) investigated ammonium removal from solution using ion exchange on to MesoLite, + -1 an equilibrium study. Results indicated a maximum equilibrium capacity of 49 g NH4 -N kg of media is achievable under the experimental conditions studied. A detailed examination of the data shows that increasing solution concentration and increased contact time provide the best performance at an optimum pH of between 6 and 7. Sarioglu (2005) investigated removal of ammonium from municipal wastewater using natural Turkish (Dogantepe) zeolite. Results showed the cation exchange capacity of Dogantepe zeolite was found to be 164.62

1368 Aust. J. Basic & Appl. Sci., 5(12): 1365-1370, 2011 me. per 100 g. These findings show that Dogantepe zeolite can be used for the removal of ammonium from wastewater. Rahmani and Mahvi (2008) investigated use of ion exchange for removal of ammonium: a biological regeneration of zeolite. The results showed that the cation exchange capacity was 10.06 (in breakthrough point) + -1 and 18.38 mg NH4 g zeolite as total capacity. The results indicated that nitrification accelerated by increasing in MLVSS concentration and concentration of nitrate remains in solution. The results obtained from bioregeneration tests of zeolite showed that the efficiency was 87.7 to 99.8% in period of 3.5 to 5.5 hours. Based on the results, since regeneration is achieved in high concentration of nitrate, the use of nitrifying sludge in several cycles is possible and the use of system can be appreciated to an alternative economical method for + removing NH4 from effluent. Chang et al., (2009) studied Ammonium nitrogen removal characteristics of zeolite media in a Biological Aerated Filter (BAF) for the treatment of textile wastewater. This study showed that natural zeolites have the feasibility to be chosen as a useful media in BAF process for the treatment of textile wastewater. Wang et al., (2007) studied removal of low-concentration ammonia in water by ion-exchange using Na- mordenite. This study showed Ammonia uptake on the Na-mordenite was minimally influenced by operating in the range of 278-333 K. The coexistent K+ and Na+ in water had little influence on ammonia uptake of the Na-mordenite. In contrast, coexistent Ca2+ and Mg2+ significantly lowered the efficiency of the Na-mordenite for ammonia removal. Samad et al., (2004) investigated phosphate removal from municipal wastewater by different adsorbents. The was found to be the more suitable for the phosphate removal from wastewater. Low pH values and high temperatures were found to enhance the removal of phosphate. Bashir et al., (2010) investigated application of response surface methodology (RSM) for optimization of ammoniacal nitrogen removal from semi-aerobic landfill leachate using ion exchange resin. According to this study, ion exchange resins can be used for the efficient removal of ammoniacal nitrogen from semi-aerobic stabilized landfill leachate. Sarudji et al., (2007) investigated cement and treatment for organic matter containing leachate. The efficiency of clay in removing organic matter was circa 50% of the cement efficiency. However, clay increased biodegradability of treated leachate up to 20% while cement decreased leachate biodegradability at the same level.

Conclusion: The landfill leachate treatment has become a vital part of environmental protection. The treatment of municipal landfill leachates involves problems linked to the presence of high concentrations of organic compounds (i.e. COD), ammonia, toxic compounds (such as metal ions), chlorides, sulphates, salts and alkalinity. Physical/chemical treatment processes are often required for treatment of mature and recalcitrant leachates. Flocculation/precipitation, activated carbon adsorption, ion exchange, membrane filtration, and oxidation technologies have been reported. Many investigations showed that the membrane bioreactor, ion exchange and adsorption methods could be efficiency for landfill leachate treatment.

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