Evaluation Of Rainwater Quality Safety On The Different Treatment Technologies

With the rapid development of Chinese economy,water resource is polluted to varying degrees.The population growth and the rapid expansion of the city have made the demand for water resources more and more.As a kind of water resources,rainwater has the advantages of large water volume,light pollution and easy availability.The effective using of it can alleviate the shortage of water resources in China to some extent.This paper mainly selects three types of rainwater treatment methods:artificial lake A,B and green roof C.Samples before and after rainfall or during rainfall were tested for water quality,and analyzed for pH,conductivity,turbidity,total phosphorus,total nitrogen,COD,SS.There are 9 indicators of acute toxicity of luminescent bacteria and SOS/umu genotoxicity.They were evaluated by the water quality comprehensive index method and the improved fuzzy comprehensive evaluation method.The water quality comprehensive index method is mainly based on the data of conventional indicators.The improved fuzzy comprehensive evaluation method can include both the conventional indicators and the biological indicators,and increases the number of indicators in the evaluation system to make the evaluation results more reliable.The results of comprehensive evaluation of the water quality of the three treatment technologies involved in A,B,and C are as follows:?1?In the analysis of artificial lake A water quality,the pH,conductivity and COD are lower than that before rain,turbidity and solid suspended matter value are higher than that before rain,and TP and TN change unobviously The law is not obvious.The bioacute toxicity zinc ion equivalent concentration EQCZn²⁺??g/L?and the bio-genetic toxicity value 4-NQO equivalent concentration TEQ_4-NQO?ng/L?all showed a lower regularity than that before the rain.After the water quality comprehensive index method is evaluated,the WQL score of the water quality before the rain is 2.711,and the water quality score after the rain is 2.463.The water quality is lower than the fourth grade standard and the water quality after the rain is better than that before the rain.After the improved fuzzy comprehensive evaluation method,the scores of the 16 evaluation subjects are as follows:0.065,0.057,0.068,0.057,0.073,0.058,0.0786,0.0785,0.047,0.050,0.057,0.059,0.069,0.073,0.059,0.051.There are 5rainfalls that the water quality is better than that before the rain.The overall quality of the artificial lake is better than that before the rain.The precipitation of rainwater and the interception of vegetation are conducive to the improvement of water quality.?2?In the analysis of artificial lake B water quality,the changes of pH,conductivity and TN are not obvious.The values of turbidity and SS are higher than that before rain,and the TP and COD are lower than before rain.The bioacute toxicity zinc ion equivalent concentration EQCZn²⁺??g/L?and the bio-genetic toxicity value 4-NQO equivalent concentration TEQ_4-NQO?ng/L?all showed a lower regularity than that before rain.After the evaluation of the water quality comprehensive index method,the water quality score WQL is2.411,and the water quality score WQL after the rainfall is 2.085.The water quality is lower than the fouth-level standard and the water quality after rain is better than that before the rain.After the improved fuzzy comprehensive evaluation method,the scores of the 10 evaluation objects are as follows:0.126,0.126,0.070,0.076,0.106,0.102,0.103,0.110,0.099,0.082.The water quality change before and after rainfall is not obvious.?3?In the water quality analysis of green roof C,the conventional indicators and bio-toxicity indicators all show a regular decrease with the increase of rainfall time.After the water quality comprehensive index method is evaluated,the WQL range of water quality during the three rainfall periods is 17.492².678;215.481⁶.816;39.301².282,the water quality exceed the standard of 4,the water quality is poor,but the water quality has improved to some extent with the increase of rainfall time.The scores of the evaluation objects in the three rainfalls are:0.267⁰.079;0.264⁰.135;0.237⁰.081.The evaluation objects in the three rainfalls decreased with the increase of rainfall time.Due to the initial effect of rainwater runoff and the interception and osmosis of the green vegetation through the roof,the water quality gradually increase with the rainfall time.In summary,physical techniques such as sedimentation,storage and retention,and chemical techniques such as dosing treatment can be obtained.Ecological purification such as vegetation interception and infiltration has a great effect on the improvement of rainwater quality.However,the overall quality of the water is poor,and advanced rainwater treatment technologies need to be added to improve water quality.