Tseolit and Ecology (Water filtration)

ECOLOGY

1. WATER FILTRATION

Natural zeolite may be used at all water treatment stations that have filtering facilities. It may be used instead of silica sand and other filtering materials both in designing new sewage disposal plants and for reconstructing existing water treatment stations. The decision concerning the filter design is taken with due consideration of local conditions, source water quality, etc.

The use of filtering facilities loaded with natural zeolite for conditioning natural water (instead of filtering materials traditionally used for the purpose) allows to:

- improve technological parameters of the filtering process with rapid filters, namely, increase the filtering speed up to 8 to 11 m/h, the filtering cycle by 4 to 16 hours, dirt-holding capacity by 50 to 100%, as well as reduce water head losses in the filter layer;

- intensify the operation of facilities by increasing the rate of filtrate flow and filtration cycle duration by 20 to 50%;

- reduce water consumption for filter washing by 10 to 13% by increasing the dirt holding capacity of the filter layer and the filtration cycle duration;

- improve the quality of treated water by principal organoleptic, physical, chemical and biological indices;

- intensify significantly processes of water coagulation treatment by contact method within the filtering charge and improve water quality by aluminum compounds after coagulating it in settling reservoirs;

- assure a barrier role for filtering facilities in case of a local pollution of a water source with some specific ingredients: ions, cations of heavy metals, radionuclides, etc.;

- develop efficient technologies of cleaning underground water from iron with consideration for its initial concentrations (ranging from 0.5 to 20 mg/l) and form of being in the water source;

- introduce filter layer modification processes into technologies of cleaning water from components that are difficult to remove (e.g. manganese, fluorine, etc.) for the purpose of obtaining highly efficient goal-oriented composites

Besides, in a number of cases the use of natural zeolite allows to reduce the number of reagents for preliminary treatment of water, lowering its cost. The use of natural zeolite in traditional water treatment flow sheets does not require any special regeneration of the filter layer. Filtering facilities are subject to usual water- or water-air washing.

Regeneration of the filter layer is required if a special technology, including both sorption or ion-exchange and appropriate regeneraton processes, is used.

Advantages of natural zeolite in filter charging as compared with sand are as follows:

- natural zeolite pertains to the class of cation exchangers and possesses good sorption, molecular-screen and catalytic properties, while silica sand pertains to inert materials;

- natural zeolite grain form factor equals to 2.4, while silica sand grain form factor equals to 1.2;

- initial hydraulic gradient for charging natural zeolite is two times less than that for charging sand;

- duration of operation of a natural zeolite filter and its protective action time is three times as great as those of a sand one;

- intergranular porosity of natural zeolite is 51 to 62 percent, i.e by 13 to 16 percent more than that of sand;

- external surface of natural zeolite is 18 m2/g, out of which the share of micropores is 12 m2/g, i.e. one order of magnitude greater than the surface of silica sand which equals to 0.12 m2/g.

Natural zeolite possesses is highly active in sorption of aluminum ions which is expecially important in using water purification coagulation processes.