| Porous ceramic emitter is a new type of emitter,which supplies water to the soil through the interconnected micro-channels and relies on the internal and external water potential difference.It has the advantages of energy saving and environmental protection.The problem of clogging of emitter has always been the key to restricting the large-scale promotion and application of micro irrigation technology.However,there is a lack of research on the clogging of porous ceramic emitters.In this paper,the effects of sediment,fertilizer and fertilizer-sediment coupling on the clogging of porous ceramic emitters are studied.The characteristics of the average relative flow rate of porous ceramic emitters with time and the distribution of sediment in the inner wall of the emitters are analyzed.the clogging mechanism of porous ceramic emitters was further revealed,and corresponding anti-blocking measures had also been proposed.The main conclusions are as follows:（1）Sediment deposition in muddy water is the main cause of physical clogging of porous ceramic emitter.In the early stage of irrigation,the clay content of sediment in muddy water had a great influence on the average relative flow of porous ceramic emitter.The higher the sediment content of clay,the greater the impact,and the easier it is to clog the emitter.However,in the later stage of irrigation（after 216 h）,the average relative flow rate of emitters was stable at around 72%,the sediment content of clay had little effect on the average relative flow rate.The sediment was deposited on the inner wall of the emitter to form a sediment film,but the sediment did not enter the ceramic micro pores of the emitter.（2）Fertilizer types have great influence on the chemical clogging of porous ceramic emitter.The larger the viscosity coefficient of fertilizer solution,the easier it is to clog.When urea was applied,the emitter does not clog,but potassium sulphate and compound fertilizer were applied,and the emitter was clogged.Among them,the compound fertilizer had the greatest influence on the clogging of the emitter.After applying the compound fertilizer,the average relative flow rate of the emitter decreased the fastest.When irrigating reached 132 h,the average relative flow rate decreased by 24%.The main cause of clogging is that the ceramic micropores filter part of the fertilizer,reducing the concentration of the fertilizer by 5%.Crystals were deposited on the outer wall of the emitter,and sediments were formed on the inner wall.The main components were（NH4）H2（PO4）2 and K2（NH4）P2O10.After the application of urea and potassium sulfate,the concentration of the fertilizer solution did not change substantially,and no sediment was formed on the inner wall of the emitter.After applying fertilizer,the viscosity coefficient of irrigation water increases.Among them,the viscosity coefficient of urea solution is the smallest while the viscosity coefficient of potassium sulfate is the largest.Therefore,the higher the viscosity,the more easily the porous ceramic emitter is clogged.（3）Fertilizer-sand coupling is more likely to cause clogging of porous ceramic emitter.The application of urea in the muddy water is more likely to cause clogging of the emitter than the sediment alone.The clogging time was advanced by 60 h,and the average relative flow of the emitter was reduced by 24%,mainly because urea accelerates the agglomeration of sediment particles and deposits in the emitter.When urea was applied to the muddy water,the average relative flow of the emitter dropped faster.When the irrigation time reached 156 h,the average relative flow of the emitter was decreased by 24%.At the later stage of irrigation（later 180 h）,the average relative flow of the emitter was stable around 70%.（4）Flushing can effectively improve the clogging of porous ceramic emitter.Flushing measures can be used to flush out the deposits on the inner walls of the pipes and emitters,so that the average relative flow of the emitters is restored to more than 90%of the initial flow.For the separate effect of sediment,before and after flushing,the time and degree of clogging of the emitters did not change much;for the fertilizer alone,before and after flushing,the re-clogging time of the emitters was advanced（24 h in advance）,and the degree of clogging increased;For fertilizer-sediment coupling,the re-clogging of the emitters was advanced（12 h in advance）and the degree of clogging increased.Irrigation with muddy water and the sediment concentration is 0.1 g/L,it is recommended to flush the irrigation system once for about 90 days;when using water-fertilizer integrated irrigation,the fertilizer should not use potassium sulfate and compound fertilizer with higher viscosity;When integrated with fertilizer and sand coupled with water and fertilizer,and the sediment concentration is 0.1 g/L,it is recommended to flush the irrigation system once for about 60days. |
