Research And Application Of Determination Method Of Salt Conductivity In Typical Industrial Wastewater

The typical industrial wastewater from total discharge port was taken as the research object in this paper, and we studied the electrical conductivity determination method for salinity in order to achieve rapid determination of the salinity in industrial wastewater and the method can meet the needs of online monitoring. This study is of great significance to achieve standardization of salt indicator as soon as possible, to control the discharge of saline wastewater, to reduce environmental pollution. First, look through lots of information to understand the characteristics of saline wastewater and determine the industry and specific enterprises to collect water sample. Then, take the actual wastewater for the determination of total salt and electrical conductivity and other parameters to have an intuitive understanding of the nature of wastewater from typical industries. Next, take use of the existing research results of scholars and research results obtained by group's simulated experiment to transform electrical conductivity and salinity of the actual wastewater, and make a comparison between electrical conductivity method salinity and gravimetric method total salt to analyze, and decide to correct the electrical conductivity determination method for salinity by simulated experiment in a low concentration. Take use of the existing formulas of scholars and group to compare and analyze the error between electrical conductivity method and gravimetric method for salinity of simulated standard saline wastewater, and set a new formula according to the error, by taking use of the actual wastewater to test the formula, the electrical conductivity determination method for salinity of typical industrial wastewater was preliminarily determined. Finally, a simple automatic online monitor for salinity was designed, so the identification and application of the electrical conductivity determination method for salinity of typical industrial wastewater was realized. The main conclusions are as follows:(1) Through an analysis of the nature of the thermoelectric industry, textile dyeing and finishing industry, pulp and papermaking industry wastewater from total discharge port, found: p H generally between 7 to 9; COD value of power plant wastewater is smaller, generally in 50mg/L or less, and has a low organic matter content while printing and dyeing, papermaking wastewater has a high organic content, COD can be up to several hundred mg/L; the total salt of power plant wastewater was commonly in 3000mg/L or less, while the total salt of printing and dyeing, papermaking wastewater can be up to several thousand even thousands; there was a big difference between salt content and electrical conductivity of the water samples in the same industry and different sampling sites, but no matter what kind of wastewater samples, water samples with high salt content, its conductivity is also large.(2) Analizing the existing conversion formulas of electrical conductivity and salinity, we found the when the major ion species and ion concentration and other properties of simulated wastewater were close to the actual industrial wastewater, the relative error between the salinity calculated by electrical conductivity method and gravimetric method is small, can be less than 10%, and when the major ion species are of a big difference, the relative error can reach more than 90%. Due to aiming at different water bodies when analyzed and identified, and the ion species, ion concentration and ion with charge number is not the same in the water, and the study of temperature, p H is limited, existing formula does not apply to industrial wastewater which was of complex composition in this study. The relative error calculated by the research formulas of the group has not reached the ideal range because of the too high simulated concentration and system error in the determination of salinity by gravimetric method.(3) During simulated experiment in a low concentration:when determining the salinity of simulated power plant wastewater, compared with standard salinity, the relative error calculated by electrical conductivity method which is determined by the group is less than 5%, so the accurate determination of salinity in wastewater can be realized by electrical conductivity method; When determining the salinity of simulated printing and dyeing wastewater, the relative error calculated by newly established electrical conductivity method is less than 1% while the error calculated by gravimetric method almost is almost less than 2%, so the salinity in the waste water can be determined accurately by newly established electrical conductivity method and gravimetric method; When determining the salinity of simulated papermaking wastewater, the relative error calculated by newly established electrical conductivity method is less than 5%, so the salinity of wastewater can be determined accurately.(4) Through the actual water test, it is possible to achieve fast, accurate determination of the salinity in industrial wastewater. When the p H is 6~10 and a temperature of 0~45?, a concentration of 500~40000mg/L, the mathematical model of salinity and electrical conductivity of power industry wastewater is y = 3.6 K/ 1 + ?(t- 25) + 581.2 K/ 1 + ?(t- 25)-61.4; when the p H is 6~10, the temperature is 0~45?, a concentration of 500~15000mg/L, the mathematical model of salinity and electrical conductivity of textile and dyeing industry wastewater is y = 6.378 K/ 1 + ?(- 25) + 591.59 K/ 1 + ?(- 25)- 52.798; for pulp and paper industry wastewater, it is need to increase the number of samples and analyze other interference factors to correct and determine the electrical conductivity method for salinity of wastewater.[K-electrical conductivity when the water temperature is t(0??t?45?), m S/cm; y-electrical conductivity method salinity, mg/L; t-the temperature of the water sample when measured,?; ?-temperature correction coefficient, 0.02].(5) A simple automatic online monitoring system for the determination of the salinity in industrial wastewater was designed, which can realize the application of electrical conductivity method, and the automatic online monitor has a certain application value.