Study On Health Risk Assessment Method Of Reclaimed Water For Toilet Flushing

With the increased shortage of water resources, reclaimed water, as a new watersource, has alleviated the water shortage to some extent. However, the safety ofreclaimed water has drawn more concern. In this paper, a health risk assessmentmethod of reclaimed water for toilet flushing was proposed combined disciplinarytheories and methods such as mathematical statistics, toxicology, risk assessment, etc.First of all, six kinds of organic pollutant indexes and four kinds of heavy metalindexes were selected as risk factors for water quality detection of reclaimed waterfrom the recycling plant J in Tianjin. Then lognormal distribution of detecting resultsfor each index was tested using Q-Q plot test and K-S non-parametric hypothesis test.Secondly, health risk assessment model and the model parameters quantificationwere studied. On the basis of the existing achievements, respiratory pathway lifetimeaverage daily exposure dose (concentration) assessment model and aerosol diffusionmodel were integrated to solve the problem that the chemical contaminantsconcentration in the air were difficult to monitor because the concentration was lowerthan the detection limit. For the model parameters, the concept of breathing rate forunit body weight was proposed, and the lognormal distribution of breathing rate forunit body weight and daily exposure time were tested.Finally, according to the health risk assessment model, the lognormal distributionfunction of some parameters, and the toxicity data of chemical contaminants, theuncertainty health risk assessment of reclaimed water for flushing was conducted. Theresults showed that:1) the health risks of organic pollutants were lower thannegligible risk level in most situation;2) all of the health risks of heavy metals wererelatively higher, but they were still lower than the maximum acceptable annual risklevel;3) there was a positive correlation between health risk and spraying intensity ofreclaimed water, and the health risks of chemical contaminants for female wereslightly higher than that for male;4) the total risk was lower than the maximumacceptable annual risk level, and the health risk from heavy metals constituted the vastmajority of the total risk.