D.t.n. Kushnir V.G., k.t.n. Benyukh O.A., magistrant Chyursinov M.V.
Kostanay state university by A.
Baitursynov, Kazakhstan
Features selection of
filters for water systems
High
performance, highly profitable agricultural production is difficult to imagine
without an effective system of water supply. In addition to providing lifting units (production)
and water transportation devices play an important role for its further
purification. This is especially true in areas where the use of
relatively clean groundwater is difficult for various reasons and we have to
use surface water, which, given the general deterioration of the planet's
ecology are often heavily contaminated. [1]
Degree of water purification and
structure of facilities for this purpose depends on the requirements for water
quality and the water quality at the source. If the water supply sources does
not satisfy the requirements of GOST for drinking purposes or does not meet the
production process, then apply the following basic processes of purification:
lighting, which is achieved by settling water storage or clarifiers for
separation of water suspended substances and filtration of water through the
filter material and the disinfection to kill disease-causing bacteria in water,
softening - a decrease in the water content of calcium and magnesium salts. [2]
Other methods of water treatment -
removal of iron, desalination, decontamination and stabilization - rarely used,
mainly for the needs of large industrial enterprises.
Filtration is the process of passing
through a layer of water lightens the filter material. Filtration, as well as
sedimentation, is used for clarification of water, ie for reducing water
retention of suspended solids. The filter material should be a porous medium
with a very small pore. [3]
Filters by type of filter medium is
divided into granular (sand, anthracite, clay), net (grid cells with different
grain size) fabric (cotton, linen , etc.), frame or alluvial (diatomite).
Granular filters are separated by filtration on a slow speed -
with a velocity filter to 0,3 m/h, open, but rather - filtration at a speed
2...15 m/h, and the exposed pressure; high speed - filtration at a speed
exceeding 25 m/h.
On the grain size of the filter layer
distinguish fine-grained filters - grain size of less than 0,4 mm , medium - 0,4...0,8
mm, coarse - more than 0,8 mm.
Filter layer may be homogeneous and
heterogeneous. For filters with nonuniform filter layer are dual layer (sand,
anthracite) and multilayer.
The movement of water in the filters
may occur from the top down - slow, conventional ambulances, pressure, from the
bottom up - contact clarifiers, bottom up and top down - double flow.
Classified the water filters, which,
however, does not apply to full and comprehensive systematization of such
devices.
Separate the two kinds of filtering:
to form a surface film without its formation (depth filtration).
When filtering of the first kinds are
retained on the filter initially only such slurry particles those are larger
than the pore size of the filter material. Sediment layer (film) formed of
retained particles suspended in itself is a filter material and plays a major
role in the purification of water and sand filter media is a support for
supporting are deposited on its surface contamination. Lightening effect of
water filters at their work as film formation over the sand gradually
increases. Filtration through a surface film, in which the clarified water
without chemical pretreatment coagulants its most characteristic of the
so-called slow filters. They are loaded with fine sand, operate at low speed
filtering and can provide a high degree of clarification of water, holding the
smallest particles of the suspension.
When filtering without skinning
particle retention, water pollutants occurs in the filter sand layer is thicker
boot where these particles are extracted from the water and retained on the
grains of sand. Not all particles can stick to the grains of sand in the
filtration. Particles that pollute the water, in their natural state have the
so-called aggregate stability, preventing their mutual sticking - coagulation
and adhesion to any surface. However, after the water treatment coagulant
aggregative stability of suspended and colloidal particles decreases, so that
their mutual ability to coalesce and adhere to the sand grains increases.
The speed of slow filtration on a
filter with suspended solids in the source water to 25 mg/l is taken equal to 0,2
m/h (0,3 m/h with one of the filters is turned off for repairs, or washing).
When the content of suspended solids in the source water 25 to 50 mg/l
respectively receive the filtration rate in the range 0,2...0,1 m/h With such a
low filtration rate slow filters must have a very large area. This makes their
high construction costs. Slow filters are concrete or brick tanks.
Slow filters were the first type of
filters used in water practice. Their dignity - a very high degree of
clarification of water and a high percentage of bacteria detention, lack of Reagent. Disadvantages slow filters are
required for larger sizes of the device area and difficult cleaning.
For clarification and discoloration
of water are widely used contact clarifiers. By design they are similar to the
filters with sand load to be placed on a layer of gravel or directly to the
drainage system. Water flows upward load, that is, in the direction of reducing
the size of its grain. Coagulant is introduced into the treated water just
before entering the filter. Thus, there occurs contact coagulation in which the
colloidal particles stick to the grains load. This allows to reduce the dose of
coagulant, and hence the overall consumption.
Contact clarifiers are used in single-stage installations for
cleaning colored and turbid waters with little muddy content in the slurry are
not more than 150 mg/l, including formed as a result of coagulation.
Remove from water suspensions of particles
without the use of reagents retains chemical composition lightens natural
water, which in some cases is a requirement of water consumers. This explains
the use of chemical-free water clarification for the drinking water supply of
large cities such as London, Paris, etc.
In the USSR, in the XX century
reagent water purification station practically superseded in water systems
nonchemical water treatment devices. This is justified by technical and
economic comparison with the old reagent schemes imperfect methods of
chemical-free water clarification on slow filters. However, in recent years,
chemical-free water clarification technology has improved significantly.
Reagentless deep water clarification
to GOST standards can be done in two ways: film filtration and filtration
volume. At high turbidity raw water it is necessary to pre-lighten before
filters. In the agricultural water supply at nonchemical clarification most
economically and technically feasible filtered through two filters.
First stage filter reduces turbidity of
raw water without providing its deep cleaning to GOST standards. This water can
be used for technical needs within farms, garages, etc.
As the filter media used sand with an
equivalent diameter of 1,4...2 mm. Thickness usually take 100... 20 cm, the
rate of filtration - 3...6 m/h.
Second stage filter provides deep water
clarification to GOST standards. It can operate on the principle of volume or
film filtration. Accordingly, taking its structure.
In our opinion, in
the water system of small and medium farmers need to actively use nonchemical
water clarification plant capacity to 20000 m3/day, which have
advantages over both the reagent cost of construction and operation, and the
reliability of their work. In addition, chemical-free devices do not provide
clarification of water waste, polluting the environment.
Literature
1. Rychagov V.V. Nasosy i nasosnye stantsii/ V.V.
Rychagov, M.M. Florinskiy. - 4-e izd.-M.: Kolos, 1975.
2. Mekhanizirovannye sposoby ochistki shakhtnykh
kolodtsev / pod obshch. red. L.E. Tazhibaeva - Alma-Ata: Kaynar, 1980.
3. Mareev
A.G. Mekhanizatsiya ochistki shakhtnykh kolodtsev - Alma-Ata: Kaynar, 1975.