Method and facility for treating water contaminated with warfare

Details Method and facility for treating water contaminated with warfare Method and facility for treating water contaminated with warfare

1997-06-18

1999-04-27

Fortuna, Ana

Liquid purification or separation

Processes

Liquid/liquid solvent or colloidal extraction or diffusing...

210651, 210774, 2101951, 210175, 210181, B01D 6100

Patent

active

058977805

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention is directed to a process for treatment of warfare agent contaminated waters having a salt content of under 500 ppm, wherein crude water led, in a separation step operating in reverse osmosis mode to a semipermeable membrane formed of organic material, are divided into retentate and permeate and a facility for the treatment of water contaminated with warfare agents having a salt content under 500 ppm, comprising a separating step operating in reverse osmosis mode, having a semipermeable membrane formed of organic material, wherein the separating step is connected on the one side with a crude water conduit and a retentate conduit and on the other side with a permeate conduit.


DISCUSSION OF THE PRIOR ART

Such a process and such a facility are disclosed in EP-0 35 27 79 B1. This process however is only limited to the treatment of warfare agent contaminated sweet waters. Since warfare agents have the property that they operate as softening agents on the semipermeable organic polymer membranes in the separation stages.
This leads thereto that the warfare agents pass through the membranes of separation stages in increasing quantities once the latter have been in operation for a few hours.


SUMMARY OF THE INVENTION

Purpose of the present invention is starting from the known procedure, to improve the treatment of waters contaminated with warfare agents.
This task is solved by providing that the crude water is salinated by a salt dosing arrangement to a salt content of greater than 1,000 ppm and led to the separating step operating in reverse osmosis mode.
The advantage of the present invention lies therein that the membranes of the separation stage operating in reverse osmosis made, even after an extended working time, no longer permit the warfare agents to proceed therethrough in unacceptable amounts. Expressed in other words, the membranes retain their blocking action against the warfare agents independent of time of operation.
A further advantage of the invention lies therein that, in consequence of the higher retention rate achieved by salination, the membranes for the decontamination of a given amount of water per unit time, there may be utilized a facility of lower efficiency than would be the case in conventional facility concepts.
The warfare agents to be separated are set forth, for example, in the (translation) Textbook of Military Chemistry, 2nd. Ed., Military Publishing Facility of the German Democratic Republic, 1977. From experience, the separable warfare agents are nerve warfare agents such as those of the V-type, of the G-type, such as sarin or tabun, and combat agents in the form of arsenic compounds such as Lewisite, or Lost, such as nitrogen Lost.
The limit concentrations for these combat agents in water are, for VX at a maximum of 20 ppb in accordance with the NATO Standardization Agreement, STANAG 2136 and for the contained in arsenic Lewisite at 100 ppb in accordance with the German Potable Water Regulation. On the other hand, the concentration of these combat agents dissolved in water can, in a serious case, be as high as 10 ppm.
In accordance with the present invention, it has been determined that these warfare agents can be particularly efficiently separated by reverse osmosis when the contaminated drinking water is at the same time mixed with salt. In accordance with the present invention, the salt content of contaminated drinking water should lie above 1,000, preferably above 2,000, and in particular above 3,000 ppm, wherein such ratio is in terms of parts by weight.
As salts, there may be utilized any hygienically harmless salt, in particular common salt.
As reverse osmosis entities, there may be advantageously utilized reverse osmosis membranes which are utilized in the desalination of sea water.
The membranes made of organic polymers can for example comprise polypropylene, polyamide, polysulfone or acetate. Alternatively however, composite membranes may be utilized such as those sold by the company Filmtec. These membranes typically have a sal

REFERENCES:
patent: 4865726 (1989-09-01), De Vries
patent: 5244579 (1993-09-01), Horner et al.
patent: 5538641 (1996-07-01), Getty et al.
Chemical Abstract 117:5555d, 1992.
Desalination, 75(1989) 363-378, Els. S. Pub.
Chemical abstract 88:141236k, 1978.
Handbook of Water Purification Walter Lorch, pp. 318-329, McGraw Hill Book Co.

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