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- The main applications of polyacrylamide(PAM,FLOCCULANT)
There are some arguments on the polyacrylamide, one of the mostly mentioned topic is, that if the polyacrylamide is toxic or not.
It is reported, that the United States Food and Drug Administration believes that the polyacrylamide and its aqueous solution is of low toxicity or non toxicity. The toxicity of the polyacrylamide is from the acrylamide monomer residues and the toxic metal material which are entrained in the production process. The acrylamide is a kind of nerve induced agent, with the injury to the human nervous system after being poisoning, the human body may show the weakness and the ataxia etc symptoms. Therefore, the national public health authorities in all countries around the world all specify the content of the residual acrylamide monomer in the industrial polyacrylamide products; usually the value is 0.5% ~ 0.05%. In the general water purification treatment, the content of the acrylamide is below 0.2%, while being used for the treatment of the direct drinking water, the content of the acrylamide must be below 0.05%. The Polyacrylamide Standard which was issued in 1985 by the International Health Organization points out that when the amount of the residual acrylamide monomer in the polyacrylamide is controlled below 0.05%, and the amount of the polyacrylamide is also controlled, the content of the residual acrylamide monomer in the treated water will be lower than 0.25ug/L, this content value will meet the drinking water standard in most countries. At present, some countries in Europe and in America generally regulate that the content of the residual acrylamide monomer in the polyacrylamide which is used in the drinking water treatment and in the foodstuff must be lower than 0.05%, and the dosage of the polyacrylamide also must be controlled.
The situation of some cationic polyacrylamide is much more complicated, that is because the cationic polyacrylalmide introduces the amino groups which make its toxicity often dozens to hundreds times higher than that of the anionic polyacrylamide and the nonionic polyacrylamide. The chronic toxicity is under further researching.
For the flocculant used in the treatment of the drinking water, the food grade products should bemore suitable. In the manual of “Water Standard Specification for Water Supply and Drainage Treatment Standards”, the water treatment standard clearly regulates that the usage amount of the polyacrylamide is more than 0.1 mg/L under the non often use, while under the regular use, this amount is less than 0.1 mg/L. When the polyacrylamide is used in the water treatment process as the coagulation aid, the above mentioned standard value could be used as the maximum dosage for the practical usage amount. Use the high quality food grade polyacrylamide with the low residual acrylamide monomer amount can ensure the sanitation and the safety of the drinking water. For example, there is a water supply plant using the polyacrylamide as the coagulation aid and the maximum dosage of the polyacrylamide is 0.09 mg/L, the polyacrylamide is of food grade, and there is no residual acrylamide monomer found in the filter water and in the tap water. So, it is believed that it is safe for the drinking water to use the food grad polyacrylamide as the coagulation aid in the water treatment process if the quality of the polyacylamide could be controlled and the dosage of the polyacrylamide could also be controlled.
In recent outlook, the application of the polyacrylamide organic products working as the water treatment agent will gradually expend along with the extension of the water shortage in our country and with the increase of our national requirements for the drinking water. For example, comparing the data between the year 1997 and 1999 in a water supply company, the consumption of the polyacrylamide as the coagulation aid has increased about 8 times, at the same time, the number of the plants using the polyacrylamide has increased from 1 to 6 in the year 1999. The application range includes the coagulation, the coagulant and the filtration. It is reported that the adding of the polyacrylamide at the value 0.015 mg/L to 0.05 mg/L before the filtration can increase the filtering circles that is to enhance the production ability by 10% to 16%. But the increase of the filtration circle also makes the increase of the water loss at the same time, therefore, the recoil time and the strength must increase correspondingly. By the contrast, the adding of the polyacrylamide filtration aid is more economical in the cost consideration. The adding of the polyacrylamide filtration aid can prevent the algae from penetrating the filter, under sudden incident situation the use of the polyacrylamide filtration aid can ensure the quality of the filtered water, there is already the domestic water supply plant using this filtration technology, the treatment effect is satisfied. The use of the polyacrylamide organic product in the water treatment process can achieve the significant effects with many advantages, such as the enhanced flocculation, the improved filtration capacity of the filter, the improved water quality, the increased of the water amount and the cost saving etc, therefore, more and more water supply companies are willing to put the polyacrylamide into the practical production. The applications of the polyacrylamide in the treatment of the drinking water fields are continually researched and developed, its prospect is optimistic.
From the above mentioned data, it is very intuitive to determine that the polyacrylamide itself is basically non toxic, because after it enters into the human body, most of the polyacrylamide will be excreted in short term, it is rarely been absorbed by the alimentary canal. Most of the polyacrylamide does not stimulate the skin, only a certain kind of hydrolyzed component may have the residual alkali, when repeatedly and long-term exposed to the skin it can stimulate the skin. So, it is no need to worry about its harmfulness of the polyacrylamide too much.