Study On Application Of Constructed Wetland To Treat Small Island Sewage

As the number of residents on small islands increases,not only will there be a shortage of freshwater resources on small islands,but also a lot of production and domestic sewage.If these wastewaters are not treated and discharged directly into seawater near small islands,they may exceed the environmental bearing capacity of small islands and their ability to self-purify wastewater,causing the ecological environment of small islands to be destroyed.This is extremely unfavorable for the sustainable development of small islands and oceans.Therefore,strengthening the comprehensive treatment of small island sewage has become an urgent problem to be solved in the construction of small islands.The constructed wetland system has a good nitrogen and phosphorus removal effect and has been proved to be a new type of sewage treatment technology with low investment,low energy consumption,and low cost.It is very suitable for treating sewage generated on small islands.The purpose of this paper is to design practical models for the application of constructed wetlands to treat small-scale island wastewater in order to treat the wastewater generated on small islands,and to provide new ideas for the treatment and utilization of small-scale island wastewater.The coral sands commonly found on small islands were selected as research objects.The structures and physical properties of coral sands and the four substrates of coral sands,steel slags,zeolites and gravels were used for isotherm adsorption experiments,adsorption kinetics tests and matrix column dynamics.Adsorption tests were conducted to examine the adsorption performance of coral sands on pollutants,and the feasibility of using coral sands as a substrate for the treatment of small-scale island wastewater was studied.The study selected the common Pittosporum plant on the small island as a research object,and constructed a small-scale verticalflow constructed wetland system to study the treatment effect of the seashore plant Pittosporum as the constructed wetland plant on small-scale island wastewater,and to evaluate the feasibility of the treatment of small island sewage using Pittosporum as the constructed wetland plant.The feasibility of small island sewage.Through research on the above content,it provides technical support for the application of constructed wetland technology to the treatment of small island sewage.The main conclusions are as follows:(1)It can be known from the static adsorption tests that the four kinds of substrates of coral sand,steel slag,zeolite and gravel have the largest theoretical adsorption amount of phosphorus: coral sand substrate > zeolite substrate > steel slag substrate > gravel substrate.The maximum theoretical adsorption capacity of ammonia substrate in the four matrixes is: zeolite substrate > coral sand substrate > steel slag substrate > gravel substrate,test data and Langmuir,Freundlich isotherm adsorption model and first-order kinetics,secondary The kinetic model has a good correlation.The secondary kinetic model can better describe the kinetics of phosphorus adsorption on the four substrates.The first-order kinetic model can better describe the adsorption kinetics of ammonia nitrogen on the four substrates.Coral sand is rich in micropores,has good phosphorus adsorption performance,and also has the ability to absorb ammonia nitrogen.It can be used as a substrate for the treatment of small island sewage.(2)The dynamic adsorption test of coral-sand and gravel base column shows that coral sand significantly shortens the removal time of pollutants such as ammonia,nitrogen and phosphorus,and has faster adsorption rate and more efficient adsorption performance,compared with commonly used wetland substrates.(3)Pittosporum can improve the removal efficiency of contaminants in constructed wetland systems,but there is still a certain gap compared with commonly used constructed wetland plants.It is a common plant on many small islands and has the use-value as the constructed wetland plant.It can be used with other constructed wetland plants when dealing with small island sewage.