Analysis On The Scaling Character Of Urine Pipe And Study On The Construction Of Source Separation Drainage System

Urine source-separation has been considered as an alternative for the future sustainable drainage system.However, blocking of the urine-collecting pipes caused by scale has become a bottleneck for further application of the new system. In our research, we analyzed the running situation of source separation drainage system in Sino-italian environmental energy-saving building, Tsinghua university and the scaling situation of urine pipes. We also investigated the influencing factors of scale such as dilution radio, flushing water, and ammonification extentunder static condition. The impact of concentration of calcium, magnesium, phosphate and urea on the scaling mass and scaling efficiency was also investigated under dynamic condition. Based on these research results, we compiled design guidelines of source-separation drainage system, developed new source-separation toilet and analyzed the project which has applied the technology.Some problems still remain in the operation of Sino-italian environmental energy-saving building, including the cleanness of toilet, the uncomfortableness of toilet usage and the blocking of the urine-collecting pipes.We found that struvite and calcium carbonate were the major ingredients of scaling, and it also included some hydroxyapatitebased on XRD analysis.The results of the impact of different factorson the urine-collecting pipes under static condition indicated that lower dilution radio produced larger amount of scale which decreased gradually from 0.24 g to 0.02 g while higher dilution radio had stronger property of precipitating of unit pure urine which increased from 1.59g/L to 2.78g/L. Rain water was the perfect flushing water as least scale was produced,whichwas only 0.15 g in the same condition, compared with tap water and reclaimed water. Higher ammonification extent induced by more urease produced more scale, but it was uncontrollable in practical application.The results of the impact of different factors on the urine-collecting pipes under flush condition indicated that the concentration of calcium and magnesium had great impact on the scaling efficiency, but the effect of these two ions were opposite. It has the lowest scaling efficiency that was 48.26% when there was only magnesium in the solution compared with the highest scaling efficiency that was 69.6% when there was only calcium in the solution. When both ions existed in the solution, the scaling efficiency increased with the addition of calcium concentration, and reduced with the addition of magnesium concentration. The concentration of phosphate and urea had no obvious effect on scaling efficiency. The higher concentration of calcium, magnesium and phosphate resulted in more scaling, but phosphate was superfluous compared with calcium and magnesium for scaling in the urine. The concentration of urea has no impact on the amount of scaling, but its hydrolysis was trigger for the reaction of scaling.Compiled design guidelines of source-separation drainage system was aimed to instruct the calculation of urine water, the design of pipe diameter, depth ratio, air hose and something else about the urine-collecting pipes. The source-separation system ofYixing experiment elementary school of east campuswas more reasonable and met the related standard, which could serveas a demonstration project for the relevant source-separation drainage system.