Research On Control Technology Of Sediment In Combined Sewer System

Field investigation and experiment analysis was conducted in order tostudy the characteristics of sediment from different sources. The results showthat characteristics vary depending on the kind of sediment, especiallyfunctional zoons.The stragic periodic cleaning the drainage network duringdry weather is introduced based on sediment characteristics and mechanismsediment polluting the water body through CSOs. Own to limits of availablenetwork cleaning technlolgies and expriments,‘pipe-in-pipe’ cleanningtechnology is exploited, meanwhile a vortex separator is installed in the pumpstation. Sediment is removed from network by network cleaning and vortexseparation.‘Pipe-in-Pipe’ Cleanning Technology means that network can becleaned through jet flow generated by perforated pipes layed in the drainagenetwork. A series of simulation experiment is conducted in order to study theinfluence of angle and diameter of hole, length between holes and velocity ofjet flow on flushing effect, The following shows the best parameters: lateralangle is22°, axial angel is45°, diameter is4mm, velocity is7.5m/s, andlength between holes is50cm. Perforated pipes with parameters above canflush the sediment layer with5cm thickness in a DN200pipe in90seconds.Orthogonal tests and single factor tests are designed in order to optimizethe primary factors and secondary factors, and the contribution of primaryfactors to separative effect is accomplished through orthogonal analysis. Theresults show that factors influencing separative effect from most to least arediameter of overflow gate, diameter of underflow gate, inlet pressure andangle of taper section, and the values of factors are30mm,20mm,0.12Mpaand8°correspondingly. The following show results of single factor tests:diameter of inlet gate is35mm, depth of overflow pipe insertion is45mm,height of cylinder section is105mm, inlet shape is rectangular withcontraction, the feeding track line is spiral, and overflow gate pattern is thick wall. The cut diameter and corrected cut diameter is28.7μm and38.3μmrespectively, and removal efficiency of suspended solid, chemical oxgendemand, total phosphorus and total nitrogen is59%,38%,35%and25%respectively.Pipeline flushing combined with vortex separator technlolgy is applicatedon a sediment controlling project.‘Pipe-in-Pipe’ Cleanning Technology couldclean a pipeline effectively with a two-week performance period, and theresults of the project performance and monitor shows that the concentrationof SS and CODCrin CSOs before and after the project is implementedreduced by23.9%and23.2%respectively, hence inducing the availabilityand promotional value of the combined technology.