Insoluble imparties

Insoluble substances

In superficial waters in the weighed condition insoluble and badly soluble substances contain: particles of clay, sand, oozy substances, carbonic substances, water oxids of aluminium, iron, manganese, high-molecular admixtures frequently in the condition of organico-mineral complexes. Besides that, fito- and zooplankton can be found in such waters. The sizes of particles of the weighed substances are within the limits of the sizes of colloid and big dispersial particles and are defined basically by the speed of a flow of water in a source. The removal of basic weight of insoluble impurities from water is an indispensable condition of preparation of water for the drinking and technical purposes. Thus such parameters of water, as turbidity and transparency are improved. The contents of weighed insoluble impurity in water (mg/dm³) is defined by sucking certain amount through dense paper or diaphragmic filter. There are visual methods for the definition of turbidity, during which water is compared with standard suspensions, prepared from infusorian ground. Transparency of water is also checked by measurement of height of its column, through which it is possible to read a normal typographical font or to see a cross with thickness of a line of 1 mm put by a black paint on a white plate, and measurement of depth, on which you cannot see white disk, put into water of a source. The concentration of insoluble substances in superficial waters achieves sometimes incredible numbers - 3000-5000 and 5000-10000 mg/l. Usually their contents changes from 100 up to 1500 mg/l, changing smoothly on seasons of year and incidentally in steps as a result of atmospheric precipitation and high waters. Only for some rivers and reservoirs turbidity does not exceed 10-15 mg/l during high waters. .

Weighed substances	Size of particles, mm	Speed of precipitation ( hydraulic coarseness), mm/sec	Time of precipitation of particles on depth of 1 m
Sand
Large	1,0	100	10 sec
Average	0,5	50	20 sec
Fine	0,1	7	2,5 min
Silt
Large	0,05-0,027	1,7-0,5	10-30 min
Fine/td>	0,01-0,005	0,07-0,017	4-18 h
Clay
Large	0,0027	0,005	2 days
Thin	0,001-0,0005	0,0007-0,00017	0,5-2 months
Colloid patricles	0,0002-0,000001	0,000007	4 years

Speed of precipitation of the weighed substances, including particles of the unspherical form easily determined experimentally, use as criterion describing the size of particles (hydraulic coarseness). Usually heterogeneous systems formed by insoluble in water impurities, are polydispersious, - they contain particles differing by the sizes or hydraulic coarseness. For the characteristic of such systems on the basis of results of the dispercial analysis distribution of particles on the sizes or weights is done. Such curves have the maxima indicating the prevailling contents in the given system of particles of the certain sizes, and in one source of water disperciality of the weighed substances can change in 2-3 times depending on the season of the year. Alongside with reservoirs with a rather large suspension (10-30 microns) there are sources, in which the insoluble impurity forms systems that are close to colloid ones (0,5-1,0 microns). Water in them is clarified only after upholding within several months.