Rusian Science News

Source: www.informnauka.ru/eng

HOW TO PRESERVE RIVER-WATER

12/21/2008

Researchers from Bashkiria have invented how to decontaminate sewage
of the enterprises where phosphate fertilizers are produced from ore. The
suggested method is not very simple but it is efficient.

Further information: Svetlana Mannanova, Ph.D. (Engineering), head of
laboratory of sewage, Scientific Research Institute of Safety of Vital
Activity, Bashkortostan Republic (Ufa), Tel.: + 7 (3472) 28-76-55, Fax: + 7
(3472) 28-39-13, mannanova1@yandex.ru
	
Researchers from the Scientific Research Institute of Safety of Vital
Activity (Ufa) have developed a method that enables to remove mineral salts
dissolved in them – sulphates and phosphates of alkali metals – from
sewage. The purified water can be freely used for industrial needs thus
saving clean river-water. The main stages of the process were for the first
time described by the authors at the VIIth All-Russian Conference on
Electrochemical Analysis Techniques “Ufa-2008”.

The subject of inquiry was the run-off water from the catch basin of the
biggest Russian enterprise for production of mineral fertilizers, including
phosphate fertilizers – Open Joint-Stock Company “Minudobreniya” (Meleuz).
In the course of ore processing (phosphate fertilizers are mainly produced
from the Kola Peninsular apatites), enormous amount of dust flies into the
air – the finest particles of the same mineral stuff, rich in ions of
alkali metals and anions – phosphates, fluorides and sulphates. Rains wash
off this dust, and water which is no longer clean rain-water but has become
industrial site sewage, gets into special reservoirs – catch basins. Having
analyzed the effluent contents, the specialists have found out that the
phosphate concentration, for example, reaches 270, and the sulphate
concentration – almost 900 milligrams per liter. Therefore, the waters
should be decontaminated in an efficient and inexpensive way. 

Two methods were suggested to solve the problem. One of them is the
so-called reagent decontamination, when a certain reagent (or several
reagents) is added into the water, dissoluble forms turn into insoluble
ones, after which it is relatively simple to remove them – to drain or wait
until they precipitate on the reservoir bottom. Having studied the effluent
composition, the chemists came to the conclusion that in this case, caustic
lime (quicklime) could help to get rid of phosphates and fluorides. If it
is added to sewage, the bulk of phosphates and sulphates will precipitate.
But – alas– although the fluoride concentration decreases significantly at
that, the fluoride content still remains too high even for industrial water
utilization. 

Alternatively, it was suggested that an additional – electrochemical
–decontamination stage should be introduced. After thorough investigation,
the researchers have shaped out parameters of the process, which enables
(with the help of galvanic coagulation) to practically fully remove
phosphates and ammonia nitrogen from the run-off water, although fluorides
would remain there. However, if reagent decontamination is applied after
that, the content of practically all toxic components can be reduced to an
acceptable level. Then the water can be used if not for drinking but for
technical needs in the enterprise water rotation system. 

Thus, rain-water (first contaminated, them decontaminated) would save clean
river-water from pollution. Let us take a realistic approach – if an
enterprise needs water, it would definitely get it. Fertilizers are
necessary, there is no arguing about that. The method suggested by chemists
from Bashkiria would minimize the damage to the environment. It is a
reasonable compromise – making the least harm while getting the greatest
advantage.

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