The Study On The Ceramsition Of Dewatered Sludge As Filters In Constructed Wetlands

As the main treatment of rural domestic sewage,the constructed wetland has already become an important research topic,especially the critical component--fillers.The removal efficiency of the constructed wetland largely depends on the adsorption effect of filters,which has a great effect of the metal ion levels.In most of the research about the filters,the studies mainly focused on natural materials,although the natural materials are extensive,the disposal result is not ideal.At present,the cost of the better filters trends to be higher and difficult to be obtained.The waterworks sludge is the by-product in waterworks,while also be the main pollutant.It contains a lot of elements such as aluminum or iron for the application of the aluminum base or iron base water clarifying agents,the treatment and disposal of it is always a difficult point.This paper making a ceramsite filter by calcined the waterworks sludge,and studied the removal efficiency of pollutants with the ceramsite filter,and start the test in the model of constructed wetland with the ceramsite filter to study the removal effect of the pollutants,for solve the problem of the sludge disposal and provide guidance for the selection of filters in constructed wetland.In this paper,the sludge was calcined under 200℃,400℃,600℃,800℃.the adsorption characteristics and the physicochemical characteristics are studied to select the optimal temperature and explore the mechanism of adsorptive.The results showed that both Freundich and Langmuir equations were fitted for describing the adsorption characteristics of filters calcined under different temperature and have a good adsorption effect on phosphorus,the best one is filters calcined under 400℃,the absorption capacity is 13698.6 mg kg-1,the best buffering ability is filters calcined under 600℃;The adoption effect of the four different sludge ceramisite increase with the lower pH;The sludge ceramisite from the exterior surface of osteoporosis through scanning electron microscope(SEM),the most homogeneity of surface pores is filters calcined under 600℃,it’s average size is suitable for microbes growing with 1～2um;The X-ray energy-dispersive spectrometer(EDS)and the content of the Fe-P、Al-P showed that the adsorption effect have a positive correlation with metal ion levels of Fe、Al,and also suggested that phosphorus were adsorbed on the filters surface mainly through chemical additives;the filters calcined under four different temperature all contains aluminum oxide compound through X-ray diffraction(XRD),it showed that physical adsorption also exist.From the above results,confirm the 600℃ as the optimal temperature.In the simulation experiment of constructed wetland,experiment was divided into three groups followed constructed wetland with sludge ceramisite,constructed wetland with cinder-block,non-plant constructed wetland with sludge ceramisite.The result showed that:the constructed wetland with sludge ceramisite have a good removal efficiency in COD,ammonia nitrogen,TN,TP.Compared with the result of similar study which the removal rate of COD is 55%-80%and removal rate of TP is 85%-90%,the sludge ceramisite have a good application prospect;But the removal rate of ammonia nitrogen,TN followed 8%-28 and 12%-27%are similar with other kinds of filters such as gravel,vermiculite,slag,which the removal rate is about 20%.