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ANAEROBIC AMMONIUM OXIDATION(ANAMMOX) PROCESS FOR NITROGEN

REMOVAL - A REVIEW

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2 AUTHORS:

Obuli Karthik

Hong Kong Baptist University

47 PUBLICATIONS 232 CITATIONS

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Kurian Joseph

Anna University, Chennai

82 PUBLICATIONS 584 CITATIONS

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Available from: Kurian Joseph

Retrieved on: 05 March 2016

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ANAEROBIC AMMONIUM OXIDATION (ANAMMOX) PROCESS FOR

NITROGEN REMOVAL – A REVIEW

Obuli P. Karthikeyan and Kurian Joseph

Centre for Environmental Studies, Anna University, Chennai – 600 025.

Tamil Nadu, INDIA

ABSTRACT

In wastewater treatment, nitrogen is being considered a one of the essential parameter as

it has significant adverse impacts on the environment. Anaerobic ammonia oxidation

( ANAMMOX ) is a novel process in which nitrite is used as the electron acceptor in the

conversion of ammonium to nitrogen gas. The ANAMMOX process offers great opportunities to

remove ammonia in fully autotrophic systems with biomass retention. No organic carbon is

needed in such nitrogen removal systems, since ammonia is used as electron donor for nitrite

reduction. This paper reviews and summarizes recent developments in nitrogen removal,

microbial aspects (occurrence, physiology, microbiology and biochemistry) of ANAMMOX,

followed by a qualitative comparison of several components of ANAMMOX technology with

conventional nitrogen removal systems and finally addresses the application of the ANAMMOX

process for nitrogen management.

KEYWORDS Wastewater, nitrogen, nitrification, and ANAMMOX

------------------------------------------------------------------------------------------------------------------------------------------------------------------

* Research Scholar and Corresponding author: [email protected]

1 Assistant Porfessor: [email protected]

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INTRODUCTION

An increasing population and industrialization will increase our water demand, placing

even more pressure on water resources. Conventional wastewater treatment plants have not been

designed for nitrogen removal, and many plants do not meet the current discharge limits (Jetten

et al., 2002). Wastewater originated from many other sources such as tannery, food processing,fertilizer manufacturing, slaughter house and landfill leachate contain greater amount of nitrogen

load, which should be treated before discharge into the surface water body (Table 1). Wastewater

containing huge amount of nitrogen compounds is not allowed to be released to the surface wateras it has ecological impacts and can affect human health (Kelter et al. 1997).

Chemical, Physicochemical and biological methods are broadly used for treatment ofwastewater loaded with highly concentrated NH4

+-N. In considering the criterion like cost-

benefit analysis, requirement of energy and chemical doses, familiarity with operational

procedures, and environmental sustainability, a particular treatment for a specific pollutant is

usually selected (Mulder et al 2003). Still, the tradition is that depending on the concentration of

nitrogen load presenting in the collected wastewater specimen, either physicochemical or biological treatment method is decided. According to Mulder (2003) three concentration ranges

could be differentiated:

• NH 4+-N concentration less than 100 mg NH4+-N/l - In this range biological N-removal is

the preferred process based on cost-effectiveness. Domestic wastewater is within this

range.

• NH 4+-N concentrations in the range 100-5000 mg NH 4

+-N/l - A typical example is sludge

liquor for which after extensive investigations biological treatment was preferred (Janus

et al., 1997). Although ammonia stripping and producing MgNH4PO4 were identified as

interesting alternatives for resource recovery these options were not cost-effective

(Priestley et al., 1995; Janus et al., 1997).

•

NH 4+

-N concentrations greater than 5000 mg NH 4+

-N/l - In this range physicochemicalmethod are technically and economically feasible. A successful example is the steamstripping of a wastewater with an ammonium concentration of 1.5% followed by

ammonia recovery which has been in operation on industrial scale since 1985 (Harmsenet al., 1986).

Table 1. Wastewater containing high concentrations of nitrogen content

Sources of Nitrogen Total Nitrogen (mg/L) Reference

Landfill leachate 500 - 2500 Chung et al (2003)

Starch Production 800 - 1100 Abeling and Seyfried (1993)

Wastewater from pectin

industry

1600 Deng Peterson et al (2003)

Wastewater from slaughter

house, after treatment in

aerobic lagoon

170 - 200 Keller et al (1997)

Wastewater from tannery 128 - 185 Marat et al (2003)

Discarded water 260 - 958 Gil and Choi (2004)

Source; Hulle 2005

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BIOLOGICAL NIROGEN REMOVAL

The biological process is cheaper and is the most widely practiced approach for nitrogen

control in wastewater treatment. Conventional biological nitrification and denitrification

processes have received the maximum attention. In Table 2, three process options of the new

system are presented and compared to a conventional nitrogen removal system based onautotrophic nitrification and heterotrophic denitrification system.

AEROBIC AND ANAEROBIC AMMONIUM OXIDATION

Ammonium oxidation has been observed in many bacterial species. Ammonia is oxidized by two pathways: first, ammonia is oxidized to nitrite by hydroxylamine, which is then oxidized

to nitrate by hydroxylamine oxidoreduxctase; Second, ammonia and nitrite are anaerobically

converted to nitrogen gas. The aerobic chemolithoautotrophic ammonia oxidizing bacteria

(AOB) are specialists that can grow on ammonia and carbon dioxide (Purkhold et al., 2000) anduse ammonia monooxygenase to convert ammonia into hydroxylamine. Many heterotrophic

bacteria, such as P. Pantotropha and Alcaligenes faecalis strain TUD (Otte et al., 1999), can

carry out the same reaction. Methanotrophs are capable of converting ammonia tohydroxylamine via the methane monooxygenase, whereas the ammonium monooxygenase can

oxidize methane to carbon dioxide. The recently identified lithotrophic planctomycete possessesthe ANAMMOX pathway, which is coupled to nitrite reduction (Strous et al., 1999).

Table 2. Qualitative comparison of several components of the ANAMMOX technology with

conventional nitrogen removal systems

Nitrifiers+ Various

heterotrophs

Aerobic NH4+oxidizers

+ Planctomycetes

Planctomycetes Aerobic NH4+

Oxidizers

Bacteria

0.05-41-36-121Reactor capacity (kg

N/m3day)

HighLowLowLowSludge production

YesNoneNoneNoneCOD requirement

NoneYesYesNoneBiomass retention

YesNoneNoneNonepH control

HighLowNoneLowOxygen requirements

Oxic; anoxicOxygen limited AnoxicOxicConditions

N2, NO3- ; NO2

-N2, NO3-N2, NO3

-NH4+, NO2

-Discharge

Wastewater Wastewater Ammonium nitrite mixtureWastewater Feed

2111Number of reactor

Conventional

nitrification,

denitrification

CANANON ANAMMOXSHARONSystem

Nitrifiers+ Various

heterotrophs

Aerobic NH4+oxidizers

+ Planctomycetes

Planctomycetes Aerobic NH4+

Oxidizers

Bacteria

0.05-41-36-121Reactor capacity (kg

N/m3day)

HighLowLowLowSludge production

YesNoneNoneNoneCOD requirement

NoneYesYesNoneBiomass retention

YesNoneNoneNonepH control

HighLowNoneLowOxygen requirements

Oxic; anoxicOxygen limited AnoxicOxicConditions

N2, NO3- ; NO2

-N2, NO3-N2, NO3

-NH4+, NO2

-Discharge

Wastewater Wastewater Ammonium nitrite mixtureWastewater Feed

2111Number of reactor

Conventional

nitrification,

denitrification

CANANON ANAMMOXSHARONSystem

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The ANaerobic AMMonium OXidation ( ANAMMOX ) process, which was discovered

10 years ago (Mulder, 1992) but already predicted to exist 30 years ago (Broda, 1977), couldoffer an alternative for the treatment of this return stream. Later, Van de Graff et al. (1997) and

Bock et al. (1995) observed that nitrite was the preferred electron acceptor for the process. Also,

other streams with high nitrogen and low carbon content such as landfill leachates and

evaporator condensates could be treated. In the ANAMMOX process ammonium is oxidizedunder anoxic, i.e. oxygen depleted, conditions with nitrite as electron acceptor. Ammonium and

nitrite are consumed on an almost equimolar basis. The ANAMMOX process should always be

combined with a partial nitritation process, such as the SHARON process (van Dongen et al.,2001a&b), where half of the ammonium is oxidized to nitrite. Both autotrophic processes will

increase the sustainability of wastewater treatment as the need for carbon addition (and

concomitant increased sludge production) is omitted and oxygen consumption and the emissionof nitrous oxide during oxidation of ammonia are largely reduced (Jetten et al., 1997). As such,

the combined process (partial nitritation and ANAMMOX ) was termed autotrophic nitrogen

removal process (Jetten et al., 2002).

OCCURANCE

The existence of ANAMMOX bacteria capable of producing nitrogen gas from ammonium

and nitrate/nitrite was demonstrated for the first time in denitrifying fluidized bed reactor treating

sewage sludge digester effluent and ammonia laden wastewater (Mulder et al., 1995; and Van deGraff et al., 1995), in marine sediments (Thamdrup and Dalsgaard, 2002), Black sea sediments

N2

TA

TNO

+ O2

+ O2

NO3-

+ COD

+ COD

TNO

N2

TA

TNO

ANAMMOX + O2

Nitrogen Fixation

Classical nitrogen removal

Autotrophic nitrogen removal

Figure 1. ANAMMOX process in nitrogen cycle

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(Kuypers et al., 2003), anoxic waters of Golf Dulce, a 200 m deep coastal bay in Costa Rica

(Dalsgaard et al., 2003) and landfill environments (Chung et al., 2003).

MICROBIOLOGY OF ANAMMOX

Microbial nitrogen metabolism also plays an important role in the global nitrogen cycle.

Microbial activities, such as denitrification and ANAMMOX , are the major mechanisms that

convert combined nitrogen to dinitrogen gas, thereby completing the nitrogen cycle. The updatednitrogen cycle with ANAMMOX is depicted in Figure 3 (after Jetten et al., 1999). Nitrification is

the aerobic oxidation of NH3 to NO3-. It consists of two sequential steps carried out by two

phylogenetically unrelated groups of aerobic chemolithoautotrophic bacteria. Some heterotrophic bacteria can also oxidize ammonium to nitrate, but this is only a very small contribution to the

overall ammonia oxidation (Pynaert, 2003). No single known autotrophic bacterium is capable of

complete oxidation of NH3 to NO3- in a single step (Abeliovich, 1992). In view of coupling a

partial nitrification unit with an Anammox unit, nitrite oxidising activity should be suppressed

and TAN should only be oxidised for about 50 % to TNO2.

The physiology of anaerobic ammonium oxidizing aggregates cultivated in a sequencing batch reactor was investigated by Strous et al. (1999). The maximum specific substrate

conversion rate of the ANAMMOX biomass was measured as a function of temperature and pH in

batch experiments. From the temperature dependency of ANAMMOX activity, the activationenergy was calculated to be 70 kJ/mol. Strous et al. (1998) have also reported that the affinity

constants for the substrates, ammonium and nitrite, are less than 0.1 mg N/L inhibited

ANAMMOX process completely. In another study Strous et al. (1999) have shown that the ANAMMOX process was reversibly inhibited by the presence of oxygen.

Bacteria capable of anaerobically oxidizing ammonium had not been known earlier and

were referred as the “lithotrophs missing from nature” (Shivaraman and Geetha, 2003). These

missing lithotrophs were discovered and identified as the new autotrophic members of the order

of planctomycete, one of the major distinct division of bacteria (Strous et al., 1999a). Theanaerobic ammonium oxidation reaction is carried out by two ANAMMOX bacteria that have

been tentatively named as “Brocardia anammoxidans” (Strous et al., 1999a) and “Kuenenia

stuttgartiensis” (Schmid et al., 2000). The high ANAMMOX activity observed for both bacteriain a pH range between 6.4 and 8.3 and temperature between 20

oC and 43

oC (Strous et al., 1999b;

and Egli et al., 2001). The ANAMMOX bacterial activity is 25-fold higher than aerobic nitirifying

bacterial oxidation of ammonium under anoxic conditions when using nitrite as the electronacceptor (Jetten et al., 1999). Acetylene, phosphate and oxygen are known to be strongly

inhibiting ANAMMOX activity (Van De Graaf et al., 1996).

BIOCHEMISTRY OF ANAMMOX

The possible metabolic pathways for anaerobic ammonium oxidation are depicted in

Figure 4. (Van de Graff et al., 1997). The ANAMMOX process is based on energy conservationfrom anaerobic ammonium oxidation with nitrite as electron accpetor without addition of

external carbon source (Jetten et al., 1999). Hydrazine and hydroxylamine are known to be some

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ANAMMOX reaction establishes a proton gradient by the effective consumption of protons in the

riboplasm and production of protons inside the anammoxosome, a mechanism known asseparation of charges. This result in an electrochemical proton gradient directed from the

anammoxosome to the riboplasm. Based on isotopic carbon analysis Schouten et al. (2004)

concluded that different ANAMMOX bacteria, such as Candidatus Scalindua sorokinii and

Candidatus Brocadia anammoxidans use identical carbon fixation pathways, which may beeither the Calvin cycle or the acetyl coenzyme A pathway.

APPLICATION OF ANAMMOX IN LEACHATE TREATMENT

Recent research has permitted the development of new ways of nitrogen removal, such as

the partial nitrification and the anaerobic oxidation of the ammonium ( ANAMMOX ), whichrepresent significant advances in the field of biological removal of the nitrogen pollution. The

application of a combined partial nitrification– ANAMMOX process to the treatment of high

ammonia nitrogen content influents, ex. leachate, is particularly promising. It would lead to

potential savings of up to 60% in oxygen generation and 100% in external carbon, besides

significantly reducing the sludge generation and the net emission of CO2 (Van Dongen etal.,2001), diminishing the total treatment operating cost up to 90 % (Jetten et al., 2001). The

introduction of partial nitrification/ ANAMMOX to the treatment of high-strength wastewaterswill lead to substantial savings of energy and resources. Such systems have been tested over

prolonged periods and demonstrated stable effluent quality and compact ammonium removal

without the need for process control. Given the low costs of our system, a full-scaleimplementation is to be expected in the near future.

LIMITATIONS

ANAMMOX coupled to nitrite reduction offers opportunities in the area of processdevelopment of nitrogen removal systems. One of the biggest challenges is how to accelerate the

slow rate of nitrogen removal from these systems (the rate is less than half that of aerobic

nitrification) (Strous et al., 1999; and Jetten et al., 1998). However, from a commercial

application perspective, the more challenging issue is the extremely slow growth rate (10-14days) of the bacteria known to carry out these reactions. Similar to aerobic nitrification,

ANAMMOX is subjected to inhibition. This process requires anaerobic conditions for ammonia

oxidation, but inhibition by oxygen is reversible

FUTURE STUDY

ANAMMOX technology has been evaluated using synthetic wastewater/sludge digester

effluent from domestic WWTP. Research is necessary to know the feasibility of applying

ANAMMOX process technology with other actual wastewater and leachates using appropriatereactor types and configuration. The performance of ANAMMOX process in treating actual

wastewater/leachate would not only depend on ANAMMOX bacteria but also on the co-existence

of other important oxygen scavenging and ammonia generating/ammonia to nitrite oxidizing

bacteria. Research is needs to be carried out to work out optimal conditions for such anecosystem to sustain in a reactor and develop methodologies to monitor the responsible

microbial community in the system. Applied genomic research can be used to identify genes and

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patterns of expression that are critical to the performance of nitrogen metabolism in responses

can be coupled with reporter systems for the development of online measurement systems.Coupling the advances related to bacterial nitrogen metabolism with improved monitors of

macroscopic performance should lead to more robust operating strategies for wastewater

bioreactors. Genomic information, in combination with traditional biochemical, genetic and

ecological studies is needed to understand the inorganic nitrogen metabolism, and thus benefittheir industrial applications.

ACKNOWLEDGEMENT

The authors wish to thank the financial support from Swedish International Development

Agency (SIDA), and technical co-ordination from Asian Institute of Technology (AIT),Bangkok, Thailand. The cooperation of Chennai Corporation in sample collection from

Kodungaiyur and Perungudi dumping grounds is gratefully acknowledged.

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