Study On Influence Of Disinfectant And Its Main Residues Chloride Ion On Bioretention Facilities

In case of public health emergencies,disinfectants were usually used to fight various viruses and prevent their spread.Sodium hypochlorite has been widely used in the environment over the past few years as an efficient and inexpensive disinfectant.During routine disinfection,large amounts of disinfectants and their major residue,chloride ions,would follow surface runoff into the bioretention facilities,which may adversely affect the function or structure of the facilities.Therefore,according to the requirements of disinfectant spraying and the climatic rainfall characteristics of Beijing,we designed the acute effect experiment of single disinfectant spraying and the effect experiment of combined pollution of runoff disinfectant and its main residue chloride ion.In this study,plants,the growing media layer and effluent were taken as research objects,and the effects of disinfectants on plant growth and the growing media layer properties in bioretention facilities as well as the removal effects of chlorine-containing disinfectants in bioretention facilities were analyzed.The conclusions of this paper were as follows:(1)The spray of disinfectant inhibited the growth of Iris tectorum and Hylotelephium erythrostictum.The higher the amount of disinfectant sprayed,the greater the wilting degree of Iris tectorum and Hylotelephium erythrostictum leaves,and the greater the decline of chlorophyll SPAD value of leaves.Hylotelephium erythrostictum was more tolerant to the disinfectant with low spraying amount than Iris tectorum,and Iris tectorum was more tolerant to the disinfectant with high spraying amount than Hylotelephium erythrostictum.The wilting index of plant leaves was negatively correlated with other growth and physiological indexes.(2)The spraying of disinfectant could increase the conductivity,urease,alkaline phosphatase,and catalase activities of the growing media layer in the facilities.Persistent application of chlorine-containing disinfectant resulted in the accumulation of Cl~-in the growing media layer,and the risk of accumulation in the Hylotelephium erythrostictum unit was higher than that in the Iris tectorum unit.The increase of Cl~-content in the growing media layer decreased the urease and catalase activities of the growing media layer in the Iris tectorum group.In addition,the growth of Iris tectorum was mainly affected by the direct spraying of disinfectant and the changes of matrix Cl~-,and enzyme activities,while the growth of Hylotelephium erythrostictum was more easily affected by the direct spraying of disinfectant.(3)The disinfectants in runoff and their residues chloride ions had little effect on the plant height,water content and chlorophyll content of Iris tectorum and Hylotelephium erythrostictum in the biological retention facility.Under the combined pollution of low concentration disinfectant and its main residue chloride ion,due to the addition of a small amount of Na Cl,the growth state of the plant was generally better.However,with the increase of the concentration of compound pollutants of the disinfectant,the growth of Iris tectorum was inhibited to some extent.(4)Low concentration of compound pollutants would increase the urease,alkaline phosphatase,and catalase activities of the growing media layer,but with the increase of concentration and persistent compound pollution of runoff disinfectant,the enzyme activities of the growing media layer were gradually decreased.The combined contaminated runoff entering the bioretention facilities would cause Cl~-accumulation in the growing media layer.In addition,the Cl~-accumulation degree of the growing media layer in the device for planting Iris tectorum was larger,and the urease and alkaline phosphatase activities of the growing media layer were lower than those in the Hylotelephium erythrostictum group on the whole.(5)The bioretention facilities could efficiently remove the chlorine-containing disinfectant from the runoff,but had no significant removal effect on the disinfectant residue Cl~-.The bioretention facilities planted with Hylotelephium erythrostictum had a better and stable removal effect of Na Cl O,and had a certain removal effect on high concentration of Cl~-.The concentration of disinfectant compound pollutants in the runoff would cause Cl~-accumulation in the growing media layer of the bioretention facilities,and Cl~-accumulation in the growing media layer to a certain extent would also affect Cl~-.In general,the spraying of disinfectant would have an acute negative impact on the growth of Iris tectorum and Hylotelephium erythrostictum in the bioretention facilities,while the combined pollution of disinfectant with runoff had a slow impact on the plant growth and the growing media layer properties.