Risk Ranking And Treatment By Coagulation Of TCM Precursor In Swimming Pool Water

In recent years,swimming has been more popular because it integrates fitness and leisure,and suitable for young and old.Therefore,people pay more and more attention to the water quality of swimming pool water.In order to ensure the swimming pool water quality reach the standard,to prevent the outbreak of infectious diseases,to protect the health of swimmers,indoor and outdoor swimming pools in China are mostly disinfected by chlorine dosing.But harmful disinfection by-products(DBPs)could be generated by reaction of chlorine and organic matter in swimming pool water during the process of disinfection.These organic compounds comes from organic matters in natural water such as humus,and others are come from swimmers,such as urine,sweat,hair,dander,cosmetics etc.Trichloromethane(TCM)is one of the most typical volatile DBPs in swimming pool environment,and it is found in large amounts in swimming pool water and air,which have potential carcinogenic effects,and attracts the attention of scientists.At present,physical and chemical fractionation methods have been used to analysis precursors of TCM by many scholars at home and abroad.Some research show that the physical and chemical characters of main TCM precursors in swimming pool are molecular weight(MW)in 1-3K Da and hydrophobic organic acid organic matter(HPOA),respectively.However,the independent physical and chemical methods can not completely reveal the properties of TCM precursors.Furthermore,the control methods of different risk ranking of organic matters which generate the TCM in swimming pool has not been researched.In order to provide theoretical basis for methods of decreasing the health risk taken from TCM in swimming pool water,this research through the completely analysis of TCM precursors in swimming pool water,using the physical-chemical combined fractionation method and different characterization methods of organic matter,reveal the TCM generate potential of different fractions,and the TCM generate risk ranking of swimming pool water organic matters has been obtained,integrated with the results of independent physical and chemical fractionation.On the basis of determining the best method of coagulation and the best method of enhanced coagulation,the control effect of coagulation and enhanced coagulation methods on the components of TCM precursors at different risk levels was revealed.The main results are as follows:(1)The largest content of organic matter in swimming pool water is hydrophilic organic matter(HPIM)which MW less than 1K Da,which accounts for more than 46% of total organic matter content in the pool.Hydrophobic acid organic matter(HPOA)which MW at 1k-3k Da has the maximum potential of TCM formation,thus causing the greatest risk of TCM production.(2)The risk of producing TCM in different fractions of water in swi mming pool is ranked from large to small: HPOA which MW at 1k-3k Da﹥HPOA﹥organic matter which MW at 1k-3k Da﹥HPIM ﹥HPOA which MW less than 1k Da﹥HPOA which MW at 3k-10 k Da.(3)The best coagulation conditions for controlling the TCM precursor of swimming pool water are as follows: Aluminum Chloride(PAC)is selected as coagulant,and the optimum dosage and p H range are 30mg/L and 6.0-7.0,respectively;(4)The best enhanced coagulation conditions for controlling the TCM precursor of swimming pool water are as follows: Based on the optimum coagulation conditions,adding Potassium Permanganate(KMn O4)0.8mg/L,and adding powdered activated carbon 2.0mg/L 2min after the addition of PAC;(5)The control effect of enhanced coagulation on the components of TCM precursors of different risk levels in the pool water were improved to some extent,compared with the control effect of coagulation.The TCM formation reduction of HPOA which MW at 1k-3k Da,HPOA,and organic matter which MW at 1k-3k Da after enhanced coagulation the were 75.18%,65.53% and 67.60%,respectively,which were higher than other organic matters.