Formation Characteristics And Control Techniques Of Chloral Hydrate In High Organic Containing Source Water

Chloral hydrate(CH)is a newly added disinfection by-product(DBPs)index in the Standards for Drinking Water Quality(GB5749-2006)of China.Its limit value is10?g/L,which is far below the regulation of other disinfection by-products,that is easy to reach the water quality standard limit in the water treatment plant with traditional chlorine disinfection process.In Northeast China,the content of humus is highin lake and reservoir water source,while the water treatment plant is mostly used in the conventional and chlorination process.Therefore,it has a high risk of CH exceeded,and a certain hidden danger to the safety of water supply.In this paper,aiming at the problem of potential CH excess risk in raw water of A water treatment plant,which is a typical lake and reservoir water source of high organic matters.The CH formation characteristics of raw water are studied by the method of the CH potential method(CHFPF),The control techniques of various improved water treatment processes on the formation of CH was studied by the method of the CH uniform formation conditions(CHUFC)in laboratory simulation of conventional water treatment experiments.Four optimization schemes for production and application of water quality characteristics in different periods of water plant were put forward,so that the effects of different optimization schemes on the formation and control of CH and other DBPs were investigated,in order to solve the problem of potential risk in CH exceeding,also provide some ideas and theoretical support for A water treatment plant.Firstly,taking the raw water from December to March of the following year as the research object,for studying the formation characteristics and control techniques of CH in raw water.The polarity of organic matter in raw water was separated by macroporous adsorption resin,which proved that hydrophobic organic matter was the main components the raw water of A water treatment plant,and most of the hydrophobic organic matter was strong.Through CHFP disinfection experiment of different polar components,it was proved that strong hydrophobic organic compound was the main precursor components of CH in raw water,which has the greatest contribution of CH formation.On the other hand,the per unit contend of hydrophilic organic matter had the strongest ability to generate CH,so that proved hydrophilic organic matter has the greatest influence on CH formation.By changing the technological parameters of CHFP disinfection experiments,it was determined that the factors of chlorine addition,reaction time and temperature are positively correlated with the formation of CH,differently,the factor of p H is negatively correlated with the formation of CH.Through the laboratory simulation of conventional water treatment and advanced treatment processes,the best improved conventional treatment techniques for controlling CHformationwas determined as follows:the CTS coagulant with 0.2 mg/L,the NaClO pre-chlorination with 2mg/L,the diatomite adsorption of 10mg/L and the advanced treatment of carbon sand filter with carbon sand filter material ratio to 10:1.By adjusting the chlorination ways of disinfection and replacing chlorine disinfectant,it is proved that adjusted the way to pre-chlorination and combined disinfection of chlorine dioxide and chloramine had the best control effect on the formation and control of CH.Finally,referring to the actual production and operation conditions of A water treatment plant and the different water quality characteristics of the reservoir raw water,it was analyzed comprehensively of the above effective control techniques that the production and application scheme is put forward: In the period of stable water quality in winter,the raw water has the characteristics of low temperature,low turbidity,high color,high organic matter and stable water quality,which is suggested to choose the scheme of adding chlorine preoxidant and coagulant to control the decrease of CH formation by about 28.15%.In the period of spring and autumn water quality fluctuation,the water quality index of raw water increases significantly,which is suggested to add chlorine preoxidant and coagulant,and add the advanced treatment of activated carbon sand filter or combined disinfection of chlorine dioxide and chloramine,so that the amount of CH can be controlled by 70.44% and 67.52%,respectively.During the eutrophication period in summer,the raw water has the characteristics of eutrophication and frequent pollution with extreme water pollution,which is suggested the scheme of uniting the processes with chlorine preoxidant and coagulant,the advanced treatment process and the chlorine dioxide-chloramine combined disinfection,so that the amount of CH formation can be reduced by 94.39%.