Application Of Alum Sludge In Ecological Restoration

Ecological problems are urgent to be solved at present.Desertification,abandoned mining areas and other ecological problems are particularly prominent in remote areas.If it is not treated in time,ecological security of surrounding areas will be affected.Alum sludge is the main by-product produced in the process of water treatment in waterworks.With the continuous increase of productivity in China,the water consumption also increases rapidly,leading to a large number of alum sludge cannot be effectively treated.However,the alum sludge has similar composition and properties with clay.If the alum sludge is applied to ecological restoration,it is of great significance for disposal of alum sludge and the sustainable development of China's ecology.Firstly,this article used the alum sludge as the cultivation matrix of plant to carry out cultivation experiments,exploring the feasibility of alum sludge as the cultivation matrix under different conditions(with or without pretreatment,different ingredients and different ratio).Through testing the bulk density,the specific gravity,the porosity and the nutrition of the alum sludge cultivation matrix and plant growth,the best structure of alum sludge cultivation matrix and matrix characteristics for plant growth were investigated.,providing a reference for application of alum sludge in large-scale ecological restoration.In addition,the sludge was used as the main raw material with the waste resources such as fly ash to make ceramsite which also can be used as cultivation matrix.The feasibility of whether the alum sludge can make ceramsitea and the optimum process were explored.Through the cultivation experiment,the influence of ceramsite on the growth of plant was preliminarily tested.The main results of this study were listed as follows:1)The untreated alum sludge cultivation matrix is not suitable for plant growth and development whereas the pretreatment alum sludge cultivation matrix obviously improved the properties of matrix.Adding the suitable amount of fly ash,vermiculite and plant ash to alum sludge cultivation matrix can improve the matrix structure properties and promote the growth and development of plant.The bulk density of the matrix can reach 1.0 g/cm~3,and the root length and fresh weight of the plant can be increased by 2-3 times.The result shows that the pretreatment alum sludge as the main cultivation matrix added with fly ash and other ingredients could be used in ecological restoration.When adding amounts of plant ash,vermiculite and fly ash were 5%,2%and 5%respectively,plant growth was best.2)The optimum process of making alum sludge ceramsite was developed as follow:the raw water sludge,fly ash and bentonite were mixed according to the best mass ratio of 2:1:1.Then,the mixture was dried in the temperature of 105?for 2hours and preheated in the temperature of 400?for 15 minutes flowed by roasted in the temperature of 1150?for 5 minutes.The average particle size of the ceramsite is 10mm,the apparent density is about 0.9 g/cm~3,the water absorption is about 12%and the compressive strength is about 2.2 Mpa.The texture of the ceramsite is hard.3)The environmental,economic and ecological benefits of the application of alum sludge for ecological restoration were evaluated,showing that a water works of 800000 ton/day can roughly earn one million per year and pretreatment alum sludge used in ecological restoration is a sustainable and promising technology.