Ammonium removal with the anaerobic ammonium oxidation Song-E Baek

Contents Introduction Anammox Studies Summary

Introduction Nitrogen compound is becoming concern due to its impact on the quality of water bodies. It is required techniques for reducing the nitrogen content of both waste water and drinking water. Nitrification combined with denitrification is the most widely used method for nitrogen control in waste water treatment. The Anammox process was originally discovered in a denirifying fluidized-bed reactor by Mulder et al. (1995) A new process is that ammonium is converted to dinitrogen gas under anaerobic conditions with nitrite as the electron acceptor. The anaerobic ammonium oxidation process (Anammox) is a novel, promising, low-cost alternative to conventional nitrification/denitrification process.

Nitrification & Denitrification Nitrification (aerobic condition) NH4 + + 3/2O2 -> NO2- + 2H+ + 6H2O : nitrosomonas NO2- + 1/2O2 -> NO3- : nitrobacter Denitrification (anaerobic condition) 6NO3- + 5CH3OH + 6H+ -> 3N2 + 5CO2 + 18H2O

Mechanism HH NH4+ + NO2- --> N2 + 2 H2O (D G0’ = - 358 kJ/mol NH4+) NR HH HZO NR : nitrite-reducing enzyme HH : hydrazine hydrolase HZO: hydrazine-oxidising enzyme Mechanism of anaerobic ammonium oxidation. NH4+ + NO2- --> N2 + 2 H2O (D G0’ = - 358 kJ/mol NH4+)

Influence of oxygen The Anammox activity at four different air saturations (A 2%, B 1%, C 0.5%, and D 0%). Only when all oxygen was removed from the incubation by flushing with argon gas the disappearance of ammonium (●) and nitrite (■) could be observed.

ANAMMOX The Anammox process is a biological, autotrophic process, which is strictly anaerobic. The growth rate of the enrichment cultures is extremely low. The doubling time of Anammox culture has been reported to be 30 days (Van de Graaf et al. 1996) Stoichiometry of anammox as: 1NH4+ 1.32NO2- + 0.066HCO3- + 0.13H+  ->                               1.02N2 + 0.26NO3- + 0.066CH2O0.5N0.15 + 2.03H2O                                 : considered growth of microorganism

Partial nitrification/Anammox® (partial nitrification) 2NH4+ + 1.5O2 = NH4+ + NO2- + H2O + 2H+ (anammox) NH4+ + NO2- = N2 + 2H2O (total) 2NH4+ + 1.5O2 = N2 + 3H2O + 2H+ Partial nitrification 50% of the ammonia is biologically converted to nitrite, using nitrifying bacteria. Partial nitrification requires oxygen and therefore (limited) aeration is required. ANAMMOX ammonia and nitrite are biologically converted into nitrogen gas

Studies The application of anammox to nitrogen removal in wastewater First, ammonium removal from synthetic water with the anammox process in fludized-bed and fixed-bed reactors. Second, treatment of ammonium-rich wastewater by partial nitritation and subsequent anaerobic ammonium oxidation (anammox) in a pilot plant.

Results 1 Fludized-bed reactor VS Fixed-bed reactor Water research 31. 8 (1997) Operation of a fluidized-bed reactor with synthetic wastewater. Operation of a fixed-bed reactor with synthetic wastewater. The temperature is 36 , pH is controlled at pH 8. They were made anoxic by flushing them with an argon/CO2 mixture.

Results 1 Ammonium removal from synthetic water Water research 31. 8 (1997) In spite of clogging of the reactor, anammox process was supported by the fixed bed experiment. Ammonium removal with synthetic wastewater using the Anammox process can be achieved in fludized bed reactor and fixed bed reactor.

Anaerobic digestion is a common way to treat concentrated wastewater. Implementation of the SHARON-Anammox process at the WWTP Anaerobic digestion is a common way to treat concentrated wastewater. Ammonium is not removed in the digestion process. Sludge digestion generally yields an ammonium-rich effluent.

Partial nitrification/Anammox® Journal of biotechnology 99 (2002) Pilot plant Poly propylene 2,5 m3 2,5 m3 Reactor configuration for partial nitritation (left) and anaerobic ammonium oxidation (right). Partial nitritation was carried out in an aerated and continuously stirred tank reactor. Anaerobic ammonium oxidation took place in a sequencing batch reactor.

Result 2 Partial nitrification reactor Journal of biotechnology 99 (2002) Nitrite/ammonium ratio produced must be about 1.3 to operate anammox stably. Appropriate ratio of nitrite/ammonium is reached within a month. The start-up period is reduced significantly at 30℃ The nitrite production rate is 0.35 kg NO2-N m-3reactor d-1. 24℃ 30℃

Result 2 Anammox reactor Journal of biotechnology 99 (2002) The temperature was kept constant at 31.1±0.7 8℃. The total nitrogen elimination was 92±7% and depended strongly on the nitrite/ammonium ratio in the inlet of the anammox reactor. Ammonium and nitrite in the influent (‘inf’) and ammonium in the effluent (‘eff’) of the anammox reactor. N total,inf is the sum of NH4,inf and NO2,inf.

Nitrification/denitrification Vs Partial nitrification/anammox Comparison of oxygen and COD consumption of classical nitrification/denitrification (left) and partial nitritation/anammox(right).

Advantage reduce oxygen demand. Parameter Combined partial nitrification and Anammox Nitrification and denitrification in an activated sludge reactor Nitrification in a gas-lift reactor combined with denitrification Oxygen consumption a (kg O2(kg NH4+-N)-1) 1.9 3.4-5 Denitrification BOD consumption a (kg BOD (kg NH4+-N)-1) >1.7 Sludge production (kg VSS (kg NH4+-N)-1) 0.08 b 1 c a Follows from reaction stoichiometry. b Values obtained from Graaf et al. (1996) and Tijhuis et al. (1994). c Values obtained from Wiesmann (1994). reduce oxygen demand. organic electron donors such as methanol is not required. lower sludge is produced.

Application The first full scale anammox reactor (2002) at the Dokhaven wastewater treatment plant, Rotterdam, the Netherlands. The reactor was inoculated by the engineers from both Dokhaven and Paques. it is treating the effluent from the local partial nitritation reactor.

Summary Partial nitrification/anammox to the treatment of wastewaters lead to substantial saving of energy and resources. Partial nitrification/anammox would require less than 50% of the oxygen compared to nitrification/denitrification. application of the Anammox process would make unnecessary the addition of extra organic electron donors such as methanol and would lead to a lower sludge production. However, there are problems. Difficult to control partial nitrification How would ammonium be converted partially to nitrate? Long start-up time is required to grow enough biomass If these problems would be solved, Partial nitrification/anammox is low-cost and good treatment method for removal nitrogen.