(3) The operation of filtration and washing is very important.
The municipality owns its waterworks and filtration plant.
The city added to its waterworks a filtration plant, with a total capacity of 150,000 gal.
There are pumping works and filtration beds for the water-supply of London.
Sand filtration, even when working in the best possible manner, falls short of the perfection necessary to prevent the passage of bacteria which may multiply after the filter is passed.
In connexion with the water works there is a good filtration plant.
In many processes of chemical technology filtration plays an important part.
The separation of organic substances by filtration under high pressure through a colloid membrane, gelatine supported in the pores of a porcelain filter being usually employed.
The city owns a fine water-supply and a filtration plant covering 20 acres, with a capacity of 30,000,000 gallons daily and storage reservoirs with a capacity of 2 2 7,000,000 gallons.
In some cases the operation of filtration is performed for the sake of removing impurities from the filtrate or liquid filtered, as in the purification of water for drinking purposes; in others the aim is to recover and collect the solid matter, as when the chemist filters off a precipitate from the liquid in which it is suspended.
The water supply is derived from the Maumee river and is filtered by a municipal filtration plant.
The space below the sieve thus formed is connected by means of an outlet tap with a closed tank, and this again communicates with a vacuum pump. By this means the filtration is quickened by the atmospheric pressure, and goes on very rapidly, as also does the subsequent washing.
As the process continued the salt-saturated layer, incapable of further effective filtration, grew in thickness downwards, until in the process of time it filled the whole mass of sandstone.
This dam has been in satisfactory use since 1885, and the slight filtration through the masonry which occurred at first is said to have almost entirely ceased.
Yet it cannot be too constantly urged that such filtration depends for its comparative perfection upon the surface film; that this surface film is not present when the filter is new, or when its materials have been recently washed; that it may be, and very often is, punctured by the actual working of the filters, or for the purpose of increasing their discharge; and that at the best it must be regarded as an exceedingly thin line of defence, not to be depended upon as a safeguard against highly polluted waters, if a purer source of supply can possibly be found.
Judging from the best observations that have been made on a large scale, the highest rate of efficient filtration when the surface film is in good condition is about 4 in.
A lately discovered effect of sand filtration is a matter of great importance in connexion with the subject of aqueducts.
Moreover, if a natural water is so liable to pathogenic pollution as to demand filtration of this kind, it ought at once to be discarded for an initially pure supply; not necessarily pure in an apparent or even in a chemical sense, for water may be visibly coloured, or may contain considerable proportions both of organic and inorganic impurity, and yet be tasteless and free from pathogenic pollution.
Attempts have been made, by adding certain coagulants to the water to be filtered, to increase the power of sand and other granular materials to arrest bacteria when passing through them at much higher velocities than are possible for successful filtration by means of the surface film upon sand.
No public supply should be open to any such doubt as ought to, or may, deter people from drinking the water without previous domestic filtration or boiling.
Filtration over charcoal or bleaching earth, are chiefly methods based on bleaching by means of oxygen or by chlorine.
Some of the more viscous crude oils obtained in the United States are employed as lubricants under the name of " natural oils," either without any treatment or after clarification by subsidence and filtration through animal charcoal.
The tertiary amine is then distilled off, the residual products separated by filtration and finally hydrolysed by a caustic alkali.
After filtration the water is pumped to the storage tanks.
For the sand-filtration of water on a large scale, in which the presence of a surface film containing zooglaea of bacteria is an essential feature, see Water Supply.
In that year, however, a League for Municipal Improvements was formed; in February 1902 a loan of $1,000,000 for municipal improvements was voted, landscape gardeners and sewage engineers were consulted, and a nonpartisan mayor was elected, under whom great advances were made in street cleaning and street paving, a new filtration plant was completed, the river front was beautified and protected from flood, sewage was diverted from Paxton Creek, and the development of an extensive park system was undertaken.
This is heated to boiling, and the residue after filtration contains about 30% of Prussian blue.
The Lamellibranchia have markedly diverged from the original type by the adoption of filtration as a method of feeding.
The city owns and operates its watersupply system (with an excellent filtration plant installed in 1904) and its gas and electric lighting plants.
Crude acetone may be purified by converting it into the crystalline sodium bisulphite compound, which is separated by filtration and then distilled with sodium carbonate.
Above the river; and there is a slow sand filtration plant for the filtration of the entire supply.
But before this was accomplished the filtration of the effluent became defective, and brackish water was received, which rapidly increased nearly to the saltness of the inflow.
395; Runeberg, "Filtration of Albuminous Liquids," Arch.
The systems of filtration employed by the different companies varied in efficacy, but both the Royal Commissions decided that water as supplied to the consumer was generally of a very high standard of purity.
To accelerate the rate of filtration various devices are resorted to, such as lengthening the tube below the filtering material, increasing the pressure on the liquid being filtered, or decreasing it in the receiver of the filtrate.
In diameter and filtered through a sand filtration plant.
A new field of inquiry was, however, opened up when, by filtration a bacterium-free toxic fluid was obtained which produced the important symptoms of the disease-in the case of diphtheria by P. P. E.
It would appear to be impossible with any water that requires filtration to secure that the first filtrate shall be satisfactory if filtration begins immediately after 'a filter is charged; and if the highest results are to be obtained, either the unfiltered water must be permitted to pass extremely slowly over the surface of the sand without passing through it, or to stand upon the sand until the surface film has formed.
Filtration in the chemical laboratory is commonly effected by the aid of a special kind of unsized paper, which in the more expensive varieties is practically pure cellulose, impurities like feric oxide, alumina, lime, magnesia and silica having been removed by treatment with hydrochloric and hydrofluoric acids.
Occasionally filtration into a vacuum is practised, but more often, as in filterpresses, the liquid is forced under pressure, either hydrostatic or obtained from a force-pump or compressed air, into a series of chambers partitioned off by cloth, which arrests the solids, but permits the passage of the liquid portions.
There are several ways to clarify water.
Starling does not accept this view, and cannot regard as an article of faith Heidenhain's dictum that normally filtration plays no part in the formation of lymph.
In regard to the purification of water, filtration was long looked upon as merely a mechanical process of straining out the solid particles, whereby a turbid water could be rendered clear.
Support is found for this opinion in Beyerinek's discovery that the juices of tobacco plants affected with the disease known as " leaf mosaic," will induce this disease after filtration through porcelain.
Heidenhain, on the other hand, rejected entirely the filtration view of lymph-formation, believing that the passage of lymph across the capillary wall is a true secretion brought about by the secretory function of the endothelial plates.
In some cases purely mechanical means such as the use of Spanish clay or filtration are employed for fining purposes.