Study On The Characteristics Of Spatial Distribution And Forecasting Model Of Bacterial Aerosols Produced By Spraying

The society would be concerned about a point that the potential health risks to people of the reuse of reclaimed water to fountain sight.According to the spray and atomization,the residual pathogen in water would come into the surrounding space.And we would be at the risk of inhaling them.So it is important to study the characteristics of spatial distribution of bacterial aerosols produced by fountain and establish mathematical model which used to forecast the rule.So sprinkler test was conducted in this study.Bacterial aerosols were sampled with six-stage Anderson air sampler at different sites around the sprinkler.The concentration and particle size distribution of bacterial aerosols were analyzed.There would be meaningful to illuminate the spatial distribution of bacterial aerosols using the wavelet neural network model.Bacterial aerosols were sampled around two fountains.The results showed that the total concentration of bacterial aerosols around two fountains is highe r than that in air without working fountains.And the number of bacterial aero sol particles which can invade human body bronchus and lung would increased when the fountain is working.We conducted sprinkler test in this study.Escherichia coli NK 5449 was test strain,the bullet sprinkler and centrifugal mist sprinkler were used as test sprinklers.The bacterial aerosols around the fountain were sampled and then bacterial were cultured and counted.The results showed that,in the space of 0.75 m to 1.75 m from the ground and 0.5m to 3m away from the sprinkler,the bacterial aerosols concentration decreased along with the increase of the height and the distance between the sampling site and the sprinkler,and had significant negative correlation with droplet diameter(P<0.05).The concentration of bacterial aerosols around centrifugal mist sprinkler is more than that around bullet sprinkler.The concentration of bacterial aerosols particles with size bigger than 7?m is more than particles with other size at every height away from the sprinkler 0.5 m.The bacterial aerosols particles mainly existed in the part with size between 1.1 and 4.7?m away from the sprinkler more than 0.5 m.The proportion of bacterial aerosols with size between 2.1 and 3.3?m around the centrifugal mist sprinkler is higher than that around the bullet sprinkler.A wavelet neural network model is established for the concentration of bacterial aerosols produced by fountain.The three-layer wavelet neural network model is based on BP wavelet neural network and Morlet wavelet basis function,and include four nerve cells in input layer: maximum spraying radius of sprinkler,the height,the distance between the sampling site and the sprinkler,concentration of bacterial suspension.The result show that when we use 4?9?12 as best node number of hidden layer,the model can well predict the total concentration of bacterial aerosols?the concentration of bacterial aerosol particles with size more than 7.0 ?m and between 0.6 and 2.1?m?the concentration of bacterial aerosol particles with size between 2.1 and7 ?m correspondingly.