International Journal of Scientific & Engineering Research, Volume 6, Issue 5, May-2015 123
ISSN 2229-5518
Removal of Ammoniacal Nitrogen by using
Albite, Activated Carbon and Resin
1Research scholar, Centre for Environment, IST, JNT University Hyderabad-85, Telangana, India.
2Associate professor & BOS Chairman, Centre for Environment, IST, JNT University Hyderabad-85, Telangana
Abstract— Ammonical Nitrogen in waste waters promote Eutrophication of receiving waters and are potentially toxic to the aquatic life. Albite, Sodium Cation Exchange Resin and Activated Carbons have shown an affinity for Ammonium ions (NH4+) and were, potentially used for the removal of NH4+ ions.The major objective of this study was to evaluate the capacity of albite, Sodium Cation Exchange Resin and Activated Carbon to remove Ammonical nitrogen from waste waters using Batch Studies. Several operating variables such as pH, Temperature, Initial Ammonium ion Concentration on the exchange capacity were explored. Batch Studies were conducted using different concentrations of ammonical nitrogen and different amounts of Zeolite, Sodium Cation Exchange Resin and Activated Carbons. This experimental approach of removing Ammonia from Synthetic Waste waters using Resin, natural Zeolite and Activated Carbon has been simulated for the study of Ammonia Removal from synthetic waste waters.
Index Terms— Ammonical nitrogen, air stripping,ion exchange,Zeolites, ammonium removal ,albite,activated carbon,resin
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Water is generally known as an important necessity for all activi- ties such as living consumption, industries agricultural and rou- tinely human activities of drinking washing and bathing. Clean drinking water is essential to human and other living things. However, the sources of the clean drinking water are contaminat- ed by chemical constituents (organics, inorganics and gases) and physical contaminants (colour, odour and solid).Inorganic pollu- tants such as ammonia-nitrogen are the main problems water treatment plants (WTPs).
The Presence of ammoniacal nitrogen in municipal, indus- trial and agricultural wastewaters promotes eutrophication of receiving waters and is potentially toxic to fish and other aquatic life [1] [2]. When ammonia accumulates to toxic levels, fish can- not extract energy from feed efficiently. If the ammonia concen- tration becomes high enough, the fish will become lethargic and eventually fall into a coma and die. In properly managed fish- ponds, ammonia seldom accumulates to lethal concentrations. Of particular concern are the deleterious effects that inorganic forms of nitrogen (nitrate, ammonia, and nitrite) exert on human health. If nitrate is reduced to nitrite and ammonia by natural or artificial processes, it poses a serious public health threat, especially for very young infants [3]
For drinking water, the USEPA has set the maximum contam- inant level (MCL) at 1 mg NO2 –N/L. However, Indian current regulation shows the MCL at 1.5 mg NH3 -N/L. Nitrate and am- monia stimulates the excessive growth of algae and other un- wanted aquatic plants. They also have harmful effects on aquatic wildlife directly through toxic effects or indirectly by oxygen depletion. Ammonia in water is either unionized ammonia (NH3) or the ammonium ion (NH4+). The relative proportion of the two forms in aqueous solutions is mainly affected by pH. Un-ionized ammonia is the more toxic form and predominates when pH is high [4]. Ammonium ion is relatively nontoxic and predominates
when pH is low. In general, less than 10% of ammonia consists the toxic form when pH is <8. However, this proportion increases dramatically as pH increases
General chemical methods of ammonical nitrogen removal from waste water includes the following:
Air stripping is a full-scale technology in which volatile organics are partitioned from ground water by greatly increasing the sur- face area of the contaminated water exposed to air.Air stripping involves the mass transfer of volatile contaminants from water to air. For ground water remediation, this process is typically con- ducted in a packed tower or an aeration tank. The typical packed tower air stripper includes a spray nozzle at the top of the tower to distribute contaminated water over the packing in the column, a fan to force air countercurrent to the water flow, and a sump at the bottom of the tower to collect decontaminated water.
In waste water, either ammonium ions, NH4 +, dissolved ammo- nia, or both may be present. The pH dependency unfurls that at pH = 7 only ammonium ions may be present in true solution. At pH = 12 only dissolved ammonia gas is present, and this gas can be liberated from waste water under proper conditions. The equi- librium is represented by the equation shown here below. As the pH is increased above 7.0, the reaction proceeds to the right.
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Two major factors affect the rate of transfer of ammonia gas from water to the atmosphere are the surface tension at the air water interface, and Difference in concentration of ammonia in the wa- ter and the air. The ammonia stripping process then consists of (1) raising the pH of the water to the values in the range of 10.8 –
11.5 (2) formation and reformation of water droplets in a strip- ping tower, and (3) using air water contact and droplet agitation by circulation of large quantities of air through the tower.
Breakpoint chlorination is the point where the demand for chlo-
rine has been fully satisfied in terms of chlorine addition to wa- ter. Breakpoint chlorination consists of a continual addition of chlorine to the water upto the point where the chlorine enquiry is met and all present ammonia is oxidized, so that only free chlo- rine remains. This is usually applied for disinfection, but it also has other benefits, such as smell and taste control. In order to reach the breakpoint, a super chlorination is applied. To achieve this, one uses chlorine concentrations which largely exceed the 1 mg/L concentration required for disinfection." All Chlorine reacts with any organic materials present until they are destroyed. Chlo- rine then reacts with amino acids or urea. These compounds come from proteins or from urine in pool water. The products of this reaction are called chloramines.
If more chlorine is added the chloramines are themselves broken down until there is nothing left to react. At this point chlorine begins to appear as 'free chlorine residual'. This point is termed
'breakpoint.Waters containing nitrogenous material, such as milk wastes or sewage effluents, yielded pronounced “break-point" curves, whereas waters deficient in these forms of pollution and substantially free of ammonia-nitrogen, seldom produced a typi- cal “break-point” curve upon chlorination.
In Chemical Precipitation, supernatant of an aerobically digested activated sludge was used as the substrate with the aim of phos- phorous and nitrogen removal. During the precipitation process of ammonium and phosphate ions with magnesium sulfate usual- ly results the magnesium ammonium phosphate (MAP). MAP is a white inorganic crystalline compound which can be used as fertilizer. The crystallization process depends on multiple param- eters such as: concentrations of phosphate, ammonium and mag- nesium, pH value, ionic strength of solutions, N/P ratio
Steam Stripping:
Wastewater is fed in to the Stripper and heated up by the steam. The NH3 -rich steam was discharged from this stripper and trans- ferred to the Steam Compressor. The steam generated was re- heated by the compressor and used as the heat source for the wastewater at the re-boiler.After heat exchange at the re-boiler, NH3 -rich steam was fed to NH3 Catalytic Converter and decom- posed into nitrogen and steam. NOx is produced in NH3 catalytic reaction as by-product and decomposed in De-NOx Reactor. Gas after the catalytic reactions contained the small amount of the leak NH3 which was cooled and scrubbed before the release to the atmosphere .
The traditional method for removal of ammonia and organic pol-
lutants from wastewater is biological treatment, but ion exchange offers a number of advantages including the ability to handle shock loadings and the ability to operate over a wider range of temperatures. The ion exchange method usually employs organic resins, which are very selective. However, they are very expen- sive.
The discovery of natural Zeolite deposits has lead to an increas- ing use of these minerals for the purpose of eliminating, or at least reducing, many long standing pollution problems. Both nat- ural and synthetic Zeolites have shown their ability for removing several cations from solutions concerning adsorption and ion
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exchange features In order to comply with the increasingly strict limits being placed on ammonia levels in sewage discharged into receiving waters, a high-rate ammonia removal process was needed.
Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents .They are known to have an affin- ity for ammonium (NH4 +) and other cations and possess a unique framework[14].. Overseas studies have established that zeolites have the potential to remove NH4 + from municipal, industrial, and aqua cultural wastewaters. The capacity of zeolites to remove NH4 + from wastewaters has been found to vary, depending on the type of zeolite used, zeolite particle size, and wastewater anion- cation composition .
The main features of Zeolites are high level of ion exchange ca- pacity, adsorption, porous structure, molecular sieve, dehydration and rehydration, low density and silica compounds. However, the structural characteristics (e.g., porosity, density, and channel length) and the composition and exchangeability of Ca, Na, K, and Mg cations in Zeolites, amongst other factors (e.g., zeolite particle size and zeolite concentration in the host rocks) are also known to influence zeolite capacity to remove NH4 from wastewaters. Clearly, the NH4 removal capacities and perfor- mance of Zeolites cannot be predicted by a single zeolite chemi- cal-physical parameter.
Natural zeolites have a strong capacity to remove NH4 + from pond discharges; they may be used at the end of a two-pond sys- tem or within an oxidation pond-constructed wetland sequence as a filtering bed. Even in farms where land application is a pre- ferred alternative to a two pond system, zeolites play a useful role as an absorbing medium for NH4 . In these farms, wastewaters are
initially passed through zeolite beds before being applied to soils
(particularly soils with a low nitrate retention capacity) to mini- mize the risk of groundwater nitrate pollution (by absorption of applied ammonical N in Zeolites, thus minimizing its nitrification to nitrate for leaching and to reduce the agricultural area required for land application of wastewaters.
For Zeolites, the pore diameters vary from around 0.45 to 0.6 nm, and these pores dictate the size of ions that enter the Zeolite pores and undergo ion exchange. The effective pore size of the crystal lattice comprises channels of two different sizes, and each type may display a different selectivity behavior for certain cations. Barrer et al. claimed that the separate ion sieve effects of the two kinds of channel or pore size in the Zeolite, and the free dimen- sions of these channels, allow a cation of a particular size to ac- cess none, one, or both of the channels for exchange. Hence the degree of exchange is specific for each Zeolite with each cation in solution [5]The present work considers the Ammonia removal from Synthetic Waste waters using Resin, natural Zeolite and Activated Carbon.
All the glassware used in the present study was Pyrex Quality,
Manufactured by borosil Glassware Ltd, Mumbai. Distilled water was used throughout experiments in the laboratory, with pH 7.0-
7.2.Analytical Reagent grade chemicals were used in the present study.Reagents were prepared from Analytical Grade Chemicals, using double Distilled Water.
Albite (NaAlSi3 O8 ) which is a natural zeolite, activated carbon and resin are the three adsorbents of ammoniacal nitrogen on
which the batch experiments are conducted to evaluate the max- imum ammonia uptake by the adsorbent.
The instruments used for carrying out the present study included
digital pH meters (HACH) for pH measurements and conductivi- ty meters (HACH), UV-VISIBLE spectrophotometer (Analytic JENA SPEKOL 2000), Shaker (LSI-2005RLN), Kjeldahl Instru- ment (KPS 020).
NH4 Cl(ammonical nitrogen) in 1000ml of distilled water to give
1000mg/l stock solution. From the Stock Solution, 100 mg/l and
200 mg/l of Standard concentrations are prepared for the batch experiments
0.09.
During the adsorption batch studies of Ammonia Removal, the
pH of the Synthetic Sample was adjusted by adding HCL or
NAOH.
Temperature was monitored between 28-350C for the adsorption of Ammonia onto the albite ,activated carbon and resin
In order to provide proper mixing of the known concentrations of
ammonia with the albite,activated carbon and resin, the samples were placed in a shaker and the RPM was maintained between
145-150.All these monitoring processes were done by following by using standard methods for the Examination of water and Wastewater[6]
Adsorption of ammonia was calculated by titrating it against 0.02
N H2 SO 4 .The instruments used for measuring different parame- ters are magnetic stirrer, electric balance, pH meter, stopwatch, electric furnace, thermometer and sieves. Adsorption measure- ments were carried out via a batch technique at room temperature (30 ± 3 oC), Accordingly 100 ml of ammonia solution of 100 mg/l and 200 mg/l concentrations were shaken on orbital shaker with 0.5 g and1.0g of dry albite zeolite ,dry activated carbon and resin at 150 rpm in 250 ml conical flask for a given time pe- riod of 60 min (range-0min, 10min, 20min,30min, 40min,50min,
60min). The solution was then filtered through Whatman filter paper No. 42 (circular, 14.0 cm). The first 2-3 ml portions of the filtrate were rejected because of adsorption of ammonia on the
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filter paper. The concentration of ammonia was determined by
using the kjeldahl method. The percentage adsorption was calcu- lated also calculated simultaneously.
Apparent Ammonium ions removal was positively increased
with increasing pH from 8.9 to10.8, while no further significant removal rate was increased at pH 11.9. This result explains the fact that a small fraction of Ammonia also has an effect for a change in the pH.Waste water solutions containing Ammonia with pH 9.5 described in the experimental section has shown best results for Ammonia Removal.
The removal rate of Ammonium in the sample was high in the initial 5minutes, but thereafter the rate significantly levels off
after 1 hour. This change in the rate of removal was due to the fact that initially all adsorbent sites were vacant and the Ammo- nia uptake was high. Afterwards, the Ammonium uptake rate by the Albite, Resin and Activated Carbon decreased significantly, due to the decrease in the adsorbent sites.
Initially, the temperature was 27oC and with increase in tempera- ture there was an apparent increase in the Ammonia removal rate.
This apparent increase in the thermal activation enhances the selectivity of Resin, Albite and Activated Carbon for the Ammo- nium Ions.
It has been observed from the results that percent removal of ammonia increases with increasing amount of the adsorbent. This is due the greater availability of the active sites or surface area, when the adsorbent quantity is increased. Although 0.5gm,1.0 gm dose of adsorbent shows ammonia removal more than 89% but it may be concluded that by increasing the adsorbent dose, the re- moval efficiency (%) beyond a dose of one gram adsorbent is not striking. Therefore, the value of 1.0 g of albite dose appears to be optimal, It is also evident that below a dose of one gram, the re- moval rate is exceptionally high. Beyond that, the percentage removal reaches almost a constant value. Very slow increase in removal of ammonia beyond an optimum dose may be attributed to the attainment of equilibrium between adsorbate and adsorbent at the operating conditions; giving it a distinct mark over other adsorbate.
The selectivity of Ammonium ions for adsorbents was purely
based on the availability of vacant adsorption sites on its surface. This reason explains the total ion exchange capacity of Resin and Activated Carbon to that of Albite
Fig 3.6a indicates adsorption of Ammonia versus time intervals when 0.5gms of adsorbents are used
Fig 3.6b indicates adsorption of Ammonia versus time intervals when 1.0gm of adsorbents are used
Fig 3.6c indicates adsorption of Ammonia versus time intervals when 0.5gms of adsorbents are used
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Fig 3.6d indicates adsorption of Ammonia versus time intervals when 1.0 gm of adsorbents are used
Fig 3.6e indicates adsorption of Ammonia versus time intervals when 0.5gms of adsorbents are used
Fig 3.6f indicates adsorption of Ammonia versus time
Intervals 1.0gm of adsorbents are used.
Fig.3.8a and 3.8b presents the effects of ammonia concentrations
such as 100mg/l and 200 mg/l on the removal efficiency (%) of albite.activated carbon and resin.It is seen from the figure 3.8a and 3.8b that the removal of ammonia increases with the increase ammonia concentration. The removal efficiency of size fraction appears to be 89 % at ammonia concentration of 100 mg/l. It can be concluded that adsorption process is highly dependent on ini- tial concentration of ammonia because at lower concentration, the ratio of the initial concentration of ammonia to the available sur- face area is low (concentration / surface area) and subsequently the fraction adsorption of ammonia increases. However, at higher concentration the availability of active sites for adsorption be- comes less and hence the percentage removal of ammonia de- creases.
Graph 3.8 a and 3.8 b shows that of the three adsorbents studied
here, Albite (natural zeolite) has the highest capacity for ammo- nium ion. Resin shows the next to highest capacity. The lowest capacity is exhibited by
activated carbon. Overall, Ammonia percentage removal ranged between the following levels for Resin it is 41-75%, Albite 77-
88% and for Activated Carbon it is 21-46%.On the basis of these results, Albite (natural resin) was found to be an efficient adsor- bent in the removal of ammonium ions from the synthetic waste water systems in batch adsorption studies.
Fig 3.8a graph showing the overall percentages of three adsor- bents (0.5gms)
Fig 3.8b graph showing the overall percentages of three adsor- bents (1.0gms)
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The adsorption studies of Ammoniacal nitrogen from Syn- thetic Water were performed successfully with selective Ion- Exchange Process using Resin, Zeolites (Albite) and Acti- vated Carbon. The Albite, activated carbon and resin were found to be equally effective at removing Ammonium ions from Ammonium Chloride Solutions containing 100mg/l and
200mg/l. However, in solutions containing higher Ammoni- um Concentrations, Albite was more effective than Resin and Activated Carbon. Batch studies of Ammonia Removal were found to be essential for the description of how Ammonium concentration interacts with the adsorbents. Adsorption of Ammonia by adsorbents (Resin, Albite and Activated car- bon) was initially fast during 5-10 minutes depending upon the Initial Ammonium Concentration and then gradually de- creased with increase in time.Vigorous shaking and a contact time of 60 minutes between Ammonium ions and Adsorbents in the batch experiments reduced the effect of particle size on Ammonia removal.The percentage of Ammonia Removal varied between different adsorbents depending upon the mass, chemical composition and surface area. The maximum ammonium ion concentration achieved in this study was 10.2 mg/lit corresponding to the removal efficiency of 88% using
1gm of Albite .
The financial support of the University Grants Commission,
Rajiv Gandhi national fellowship scheme is gratefully acknowl- edged.
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