Chernoistochinsk (26.4 km2) and Verchne-Vyisk (6.0 km2) water reservoirs
These reservoirs differ from those above, they are used as sources of drinking water. Because of high level of cyanobacteria growth, especially in Chernoistochinsk Reservoir, there was a real threat of rejection of using the water for drinking needs. That’s why Nizhny Tagil authority decided to work on biological rehabilitation of the reservoirs using algocenosis correction method. Algolization works lead to positive results. Particularly in algocenosis structure there are no such kinds of cyanobacteria which cause water “bloom”.
Besides, during one year water quality improved in both reservoirs by the following indexes, controlled by Joint Stock Company Vodokanal-NT: sulfates, smell, COD, nitrates, chlorides, fluorides, total hardness, turbidity, ammonia, nitrites, magnesium, manganese, total iron, petrochemicals. The indexes can be divided into two groups.
The first group includes macro components and indexes, concentration changes of which, in the absence of large number, subject to season varieties. The group is composed of macro components namely calcium, magnesium, sodium, potassium, chlorides, sulfates and hydrocarbons. Their content is growing with temperature rise and goes down in cold weather.
Content of dissolved in water oxygen has reverse relationship.
Also this group contains such indexes as total hardness, biochemical and chemical consuming of oxygen.
Components and indexes, which have stochastic nature of concentration change, form the second group. Primarily they are heavy metals, nitrogen forms, phenols, SPP and petrochemicals. Heavy metals have atmofilling nature of getting into water and their concentration is growing rapidly in the result of snow melting but during a year tends to reduction. High content of ammonium nitrogen says about new flow of pollution. In a result of oxidation the pollutant transforms into the most toxic form – nitrite – ion which oxidizes to nitrate-ion. Nitrate content is in a reverse relationship with pH index.
On a basis of the indexes ORPI calculation was made and its changing in a season aspect was inspected. As it is shown on the schedule in figures 1-4, there is a vivid tendency to decreasing of the index.
Figures 1 Figures 2
Figures 3 Figures 4
It is important to notice that ORPI dynamics of pollutant content in a near-surface water layer, where the workers of Joint stock company NPO «Algobiotechnologia» Ltd take samplings, is similar to the changing dynamics of chemical water content which is taken from a depth of 4-6 meters by Joint Stock Company Vodokanal-NT. In both cases we talk about decreasing contaminant concentration. It happens because of the fact that in a result of algolization a near-surface water layer became purer and in a result of convective movement purifying of deeper water layers takes place. Algae biomass percentage of Chernoistochinsk and Verchne-Vyisk Reservoirs in August, 2011 is shown in figures 5-6.
Figure 5
Figure 6
We can’t avoid saying that in algocenosis structure there are no such types of cyanobacteria which cause water “bloom”.
These results can be got from reservoirs of other large freshwater objects, affected by water “bloom” with such cyanobacteria as Àðhanizomenon, Oscillatoria, Ànabaena, Microcystis. Taking high toxicity and pathogenicityo of cyanobactria into account ecological meaning of such work is extremely high.