информация про блокирование нитрификации при нулевых фосфатах
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Plant and Soil
December 1974, Volume 41, Issue 3, pp 541–547
The influence of phosphate deficiency on nitrification
• B. S. Purchase
Cite this article as:
Purchase, B.S. Plant Soil (1974) 41: 541. doi:10.1007/BF02185815
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Ammonium sulphate applied to savanna grassland stimulated nitriteoxidizers in some plots but not in others. Extracts from the contrasting soils differed in suitability as growth media for nitrite-oxidizers. This difference could be eliminated by adding KH2PO4 or Na2HPO4 to the extracts
. The concentration of available P was highest in soils where nitrite-oxidizers had responded to (NH4)2SO4.
Various soils were mixed with (NH4)2SO4 and then incubated. In those containing less than 6 μg/g of available P, nitrate accumulation between days 4 and 11 was correlated with the concentration of available P.
Between days 11 and 31 there was no such correlation.
When a mixture of ammonia- and nitrite-oxidizers was grown in media containing various concentrations of P, nitrite accumulation was abnormally high where the P concentration was low.
It is concluded that nitrite-oxidizers are more sensitive to P deficiency than are ammonia-oxidizers and that P deficiency is sufficiently severe in many Rhodesian soils to restrict the growth rate of nitrite-oxidizers, thereby restricting their ability to compete for nitrogen.
This work forms part of a thesis approved by the University of London for the Ph.D. degree
Nitrification in rapid sand filter
hosphate limitation at low temperatures
Van der Aa, L. T. J., Kors, L. J., Wind, A. P. M., Hofman, J. A. M. H. and Rietveld, L. C., 2002. Nitrification in rapid sand filter
hosphate limitation at low temperatures. Water Science and Technology : Water Supply, 2 (1), pp. 37-46.
You may be able to access a copy if URLs are provided below.
In winter 1995-1996 the RSF of AWS River-Lake Waterworks suffered from ammonium breakthrough. Research indicated that the nitrification was limited by stagnated growth of the nitrifying bacteria due to low phosphate concentrations at low temperatures (0-3°C). Phosphoric acid was dosed prior to the RSF (dose 35-50 μg PO4 3- -P.I-1) to stimulate bacteria growth
. Two weeks after starting the addition, ammonium removal in the RSF had recovered. AWS is conducting research on alternatives for production capacity extension. Several alternatives involve the construction of an additional RSF prior to the reservoir. Pilot experiments on RSF prior to the reservoir show that complete nitrification in these additional RSF is possible. The phosphate concentration should amount at least 10 μg PO4 3- -P.I-1.
A model has been developed to predict nitrification in RSF. The model confirms the results from both the River-Lake Waterworks' RSF as from the pilot RSF. The model is used for process control and scenario studies
Neither ammonia nor nitrite is a particularly good substrate for growth from a thermodynamic standpoint. Nonetheless, these bacteria have developed metabolisms that rely almost exclusively on the use of these substrates for growth and maintenance. AOB require ammonia, carbon dioxide, sulfate, phosphate and some trace elements for growth, and from this they synthesize all the biochemical constituents required for life.
Three enzymes are key to this unusual metabolism (see Nitrification). The AOB use ammonia monooxygenase (AMO) to initiate the catabolism of ammonia, which is oxidized to hydroxylamine. Hydroxylamine oxidoreductase (HAO)then catalyzes the transformation of hydroxylamine to nitrite. The electrons released in the second step are partitioned back to ammonia monooxygenase, to an electron transport chain coupled to production of a proton gradient, and to reverse electron flow to produce NAD(P)H for biosynthesis.
In the NOB, a single enzyme, nitrite oxidoreductase (NXR), catalyzes the oxidation of nitrite to nitrate.
All species of nitrifying bacteria require a number of micronutrients. Most important among these is the need for phosphorus for ATP (Adenosine Tri-Phosphate) production. The conversion of ATP provides energy for cellular functions. Phosphorus is normally available to cells in the form of phosphates (PO4). Nitrobacter, especially, is unable to oxidize nitrite to nitrate in the absence of phosphates.
Sufficient phosphates are normally present in regular drinking water. During certain periods of the year, the amount of phosphates may be very low. A phenomenon known as "Phosphate Block" may occur. If all the above described parameters are within the optimum ranges for the bacteria and nitrite levels continue to escalate without production of nitrate, then phosphate block may be occurring. In recent years, with the advent of phosphate-free synthetic sea salt mixes, this problem has become prevalent among marine aquarists when establishing a new tank.
Fortunately, phosphate block is easy to remedy. A source of phosphate needs to be added to the aquarium.
Phosphoric Acid is recommended as being simplest to use and dose, however, either mono-sodium phosphate or di-sodium phosphate may be substituted. When using a 31% phosphoric acid mixture, apply a one time application of 1 drop per 4 gallons of water to activate the Nitrobacter. This small dosage of phosphoric acid will not affect the pH or alkalinity of marine aquaria.
Minimal levels of other essential micronutrients is often not a problem as they are available in our drinking water supplies. The increasing popularity of high-tech water filters for deionizing, distilling, and reverse osmosis (hyper-filtration) produce water that is stripped of these nutrients. While these filters are generally excellent for producing high purity water, this water will also be inhibitory to nitrifying bacteria.
The serious aquarist must replenish the basic salts necessary to the survival of the aquarium’s inhabitants. These salts, however, usually lack these critical micronutrients.