The Nitrogen Cycle -
Control Ammonia and Nitrite

in Ponds, Lakes, Lagoons, Rivers
and Wastewater Treatment

by Valerie Anne Edwards, CEO Alken-Murray Corporation


Ammonia forms when urease enzymes produced by strains such as Escherichia coli, Hafnia elei Moller, Ureaplasma urealyticum Shephard, Sporosarcina pastureii (Miguel) Chester, (formerly Bacillus pasteurii), some Bacillus amyloliquefaciens and other strains, when they contact urea and uric acid from animal urine and water. Ammonia is also produced when proteins are degraded first to amino acids and then to ammonia.

Special strains of Nitrobacter winogradskyi and Nitrosomonas europaea, with superior talent for rapid nitrification under aerobic conditions, are included in our Alken Clear-Flo® 1100-50x, 1200, 1400-50x , and 7110-50x, formulas. Since molecular oxygen is involved in the reaction of these strains, they are termed obligately aerobic. These autotrophic microbes inefficiently use the energy gained from oxidizing ammonia to fix carbon. This activity gives these bacteria a dual ecological role - recycling nitrogen and fixing carbon into organic compounds. Carbon fixation by this method is not very efficient, because the fixation of one mole of carbon requires the oxidation of 35 moles of ammonia to nitrite and of 100 moles of nitrite to nitrate.

Nitrifiers are fragile microorganisms which are sensitive to acid despite the fact that they produce acid during oxidation of ammonia and nitrite. If a large source of nitrogen is dumped into the environment, these organisms can potentially kill themselves by metabolizing it to nitric acid, unless pH is buffered with limestone or other slow-dissolving sources of alkalinity.. Since they are also strict aerobes, nitrifiers can be killed if the introduction of wastes leads to excessive growth of other species that deplete oxygen. This is why Alken-Murray always recommends mechanical aeration with two to three ppm of oxygen when degradation of ammonia is desired.

Every year, 300 billion Kg, less than one millionth of the total available nitrogen is recycled biologically. Nitrogen released in an uncontrolled manner can have adverse environmental impacts, such as elevated levels of nitrate in food and water, which may constitute a health hazard to both humans and animals. Excessive N applied to the soil then produces an accumulation of nitrate in plants, and undesirably high levels of nitrate in potable water. In polluted waterways, excess organic wastes stimulate bacterial growth, which consumes oxygen. Since artificial aeration is not added to supplement oxygen levels, the dissolved oxygen in the water becomes depleted, causing the fish to die, followed by death of the lower forms, including protozoa. When oxygen completely disappears, the water becomes septic, acquires a black color and supports only anaerobic bacteria, which produce odors and toxic gases. By treating waste in lagoons, waste pits and digesters, one of the point sources for excess nutrient runoff, the responsible animal producer can reduce or eliminate these negative impacts. Ideal management practices encourage the streams and lakes to slowly recover, as various good anaerobic bacteria release oxygen during their metabolism, which increases the dissolved oxygen level in the waterbody, until it can again support normal aquatic inhabitants.

The biochemical reaction of Nitrosomonas spp is:

hydroxylamine + nitrous acid = nitrohydroxylamine


The next stage is a direct oxidation step, as follows:

nitrohydroxylamamine + oxygen = nitric acid

Sixty-six kilocalories of energy are liberated per gram atom of ammonia oxidized.

The biochemical reaction of Nitrobacter is a very simple reaction, involving the cytochrome system as follows:

equation 3

Then the cyt.Fe+++ is regenerated by:

equation 4

Eighteen kcal of energy is liberated per gram atom of nitrite oxidized.

This whole process removes electrons from a hydrated nitrite ion. The reactions of Nitrobacter are inhibited by small quantities of ammonia gas (NH3: 1.4 mg/L inhibits 99%), which can lead to a toxic buildup of nitrite, since Nitrosomonas is not inhibited from oxidizing ammonia to nitrite, in the presence of ammonia.

Both Nitrosomonas and Nitrobacter perform within a pH range of 6.8 to 8.5. Optimal pH is 8.2 to 8.3. Warmer temperatures (above 60°F) also enhance nitrification. The size and type of system, and degree of ammonia present, all influence the prescription dosage and application site. Normally, treatment once or twice weekly with Alken Clear-Flo 1100-50x or Alken Clear-Flo 7110-50x is sufficient, after an adequate biomass is established. Higher initial dosages are usually prescribed to establish a stable biomass rapidly.

Although there are a number of different strains which will perform nitrification, the rate of formation for Nitrosomonas is typically 1000 to 30,000 mgN/day/g dry weight cells and for Nitrobacter is 5000 to 70000 mgN/day/g dry weight cells, which is so much higher than the formation rates of the other strains capable of nitrification, that these two are the most useful strains. Other bacterial strains perform nitrification by forming hydroxylamine, amine oxides (R3N-O) or nitroso- compounds (-N-NO or -NOH-NO containing compounds).

Recently, it has been discovered that certain sulfide oxidizing, denitrifying bacteria, such as Paracoccus pantotrophus and our own Bacillus mojavensi AMH 118, are also capable of heterotrophic ammonia oxidation to nitrite. Both of these species can be found in Alken Enz-Odor 6 and Alken Clear-Flo 1005. These formulas do NOT replace true nitrifiers, but can augment performance in applications which prohibit the use of true nitrifiers, due to lower oxygen level, acidic pH range or levels of BOD and COD above 200 mg/L. Another product usefule when conditions prohibit the use of true nitrifiers is Alken Nu-Bind 3, which utilizes Yucca schidigera to inhibit the enzyme urease from turning urine into ammonia, while it provides Bacillus mojavensis AMH 118 (mentioned above) and other Bacillus spp. to utilize ammonia via both heterotrophic and chemotrophic pathways, depending on the level of BOD, COD, ammonia and dissolved oxygen present.

Alken Nu-Bind 3 is often applied together with various saprophytic heterotrophic microbial formulas designed to sufficiently degrade BOD, COD and specific pollutants that dissolved oxygen levels rise to a level where nitrifiers can survive to eliminate excessive ammonia that was not needed by the heterotrophs to balance high levels of organic carbon pollutants. The treatments applied in lakes, ponds, rivers and streams will usually be different from those selected for industrial and municipal wastewater, although some rivers in China and the Philippines are more polluted than the average USA or EU wastewater treatment system and must be treated accordingly.

Denitrification is the reduction of nitrate to nitrite and then to nitrous oxide or nitrogen gas. Denitrification is normally performed under anoxic conditions, which is comparable to anaerobic conditions except for the presence of nitrate and/or nitrite. In natural or aquaculture ponds and lakes, this condition is found only in the sludge, but in wastewater, the condition can be created by adding nitrate to collection systems, anaerobic lagoons etc., or is created by addition of wastewater that formerly contained ammonia, following nitrification, as described above. While Alken-Murray offers a number of products with classical denitrification talent, only Alken Clear-Flo 1005 offers aerobic denitrification, performed by Paracoccus denitrificans and two unique Bacillus pumilus strains discovered by Alken-Murray's Valerie Anne Edwards. For each 1 mg/L of nitrate reduced to nitrogen gas, you will recover 3.5 mg/L of alkalinity, which is a less than perfect offset to the alkalinity needed to buffer acid produced during nitrification.

Never apply nitrifiers CF 1100-50x/7110-50x together with Alken Clear-Flo 1005 since the faster growing aerobic denitrifiers in the latter product, will competitively exclude Nitrobacter winogradskyi in the nitrifier product, when both compete for nitrite, under low to moderately aerobic conditions. This is not an issue with classical denitrifying bacteria, found in such products as Alken Clear-Flo 1006, 7007, 7008 etc., since classical denitrifiers prefer free oxygen to nitrate and will use nitrite ONLY when no free oxygen or nitrate are available instead


Diagram of the Nitrogen Cycle 


Great new scientific paper examines genes of Nitrosomonas europaea


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