INTENSIFICATION OF BIOLOGICAL PROCESSES DURING THE REMOVAL OF AMMONIUM IONS FROM WATER

Abstract

Currently one of the main problems in the purification of natural and sewage water is the removal from them biogenic elements – nitrogen and phosphorus that cause eutrophication of water bodies. In relation to nitrogen, there are several ways of it removal from the water. So, ammonium can be converted to ammonia and then to blown out from alkaline water, he also can be eliminated from water by the method of electrolytic oxidation, by ozonization or chlorination followed by filtration through activated carbon. Nitrates and nitrites may be removed by chemically reducing until molecular nitrogen, by using distillation or electrolysis. All three of these nitrogen compounds can be removed by ion exchange or ultrafiltration. However, all these methods require expensive reagents and equipment, they are difficult to operate and low-effective. To date, a biological method is considered as the cheapest, environmentally perfect, and therefore the most widely used method of purification from nitrogen. But according to traditional technological schemes of their elimination it requires the participation of two microbiological processes – nitrification (oxidation of ammonium ions to nitrate ions) and denitrification (recovery of nitrate ions to gaseous nitrogen). These two processes are characterized by the presence of conflicting requirements to the aquatic environment by the quantity of oxygen, organic compounds and many other parameters. In this regard, the most common scheme which results to removal from water the nitrogen compounds is a combination of classic nitrification and denitrification processes when they pass separately. The disadvantages of separate systems consist in the large costs of building separate (aerobic and anaerobic) bioreactors, the need to build secondary settling tanks after each stage of purification, which requires the construction of additional pumping stations, which lead to higher energy costs to maintain of necessary concentration of oxygen during the nitrification, etc. So, now the most promising considered the use of combination system of nitrogen removal. In such schemes, nitrification and denitrification processes are occurring in the same building (the bioreactor) simultaneously.Unresolved and controversial part in this scientific problem is optimization process of extracting nitrogen from the water flow while aerobic-anaerobic processes of nitrification and denitrification pass in the same reactor (OND phenomenon), which so far has not found an adequate explanation. Compared to classical schemes, cleaning processes using this phenomenon require less concentration of dissolved oxygen, no need to add organic matter, reduced costs for hardware, etc. However, being attractive from an economic perspective, these processes very “capricious” in their practical application.Based on the above, the purpose of our work was to find basic principles of optimization and intensification of biological processes that lead to the removal of nitrogen from the water while passing simultaneously nitrification and denitrification in a bioreactor.At the first stage of this work studied the advisability of isolate individual physiological groups of microorganisms and their associations with different habitats and environmental zones. Established that hypolimnion’s zone is the environment within which emerging microbial community, the most suitable for the efficient removal from water ammonium ions by simultaneous nitro-denitrification.A comparison of different loading materials depending on their impact on the effectiveness removal of ammonium ions from water by the microcenosis of bioreactor had also conducted. It is shown that the best filling for the aerobic-anaerobic bioreactor are the polystyrene blocks with the addition of clay minerals.The processes of improving the efficiency of extracting ammonium from the water are accompanied by changes in the dynamics of microbial populations. Thus, as a result of 3-month adapt of mycrocenosis to increased levels of ammonium ions, decrease in the number of species of microorganisms in bioreactor on half while maintaining of the percentage of anaerobic microorganisms as well as increasing the total microbial number have been observed.