Technological Research On Storage-purification Of Storage Tank In Combined Drainage Systemand Groove Sand Removal

This research was based on the National Water Program of Pollution and Control.Combined sewage from areas of Kunming First Plant of Wastewater Treatment wassampled and experiments were conducted, including natural sentimentation property,selection of high sorption capacity flocculants and coagulants, relation betweenrainfall-runoff and quality-quantity of combined sewage, storage-purification andhydraulic flushing of combined sewage. Results showed that：Through experiment study by cumulative sedimentation of combined sewage, itshowed: after30min, most pollutants were removed and after120min, removal rate ofSS, COD_Cr, TN, TP, NH₃-N reached96.14%,90.63%,54.22%,66.95%and4.1%respectively; COD_Cr、TN、TP had positive correlation with SS that correlationcoefficients were0.974、0.961、0.989, but NH3-N was on the contrary; We alsostudied influence on the removal rate of the initial concentration of SS and removalrate was high with high initial concentration; and we got sedimentation laws of eachpollutant through function fitting of experimental data; it also showed when the initialeffect was not significant flocculant was added at30min; when the initial effect wassignificant, extending the HRT can reduce pollutants into Dianchi Lake.Selection experiments were performed among PAFC, polyaluminum sulfate,polymeric ferric sulfate, PAC, polymerization of dual acid ferroaluminum and theoptimum one was PAC. Mix red soil, Bentonite, Ceramsite particles, Pumice,Polyacrylamide and vesuvianite with PAC. Through experiments of comparison,vesuvianite was the best coagulant and it was chosen to be modified by acid-baseconditions. Relying on composite flocculant to treat sewage, it was obtained throughorthogonal tests L₉（3⁴） under conditions of70mg/L dosage PAC: when dosage of themodified vesuvianite was4g/L, reaction time was20min and the reaction pH was8.5,removal ratio of TN、TP、CODCrwere48.15%、82.25%�'�92.57%respectively;while dosage of modified vesuvianite was8g/L, treaction time was60⁷0min and thereaction pH was8.5⁹.0, removal ratio of ammonia nitrogen was26%～30%,reaching the highest.By monitoring Kunming rainfall we got emissions of pollutants of rainy seasonwere3-5times that of dry season and that of COD_Cr、TN and TP were more than4times; concentrations of TN、TP、COD_Cr、SS had obvious relations with flow andconcentration peaks of CODCrand SS lagged behind that of flow; SS was the mainpollutants of urban combined sewage and it was carrier of other pollutants.Through designing and improving pilot-storage tank, experiments wereconducted to study quality variations of dry season wastewater and combined sewagein different rain conditions. Storage tank scale was3～4m³/h and average surfacehydraulic load was0.674m³/（m².h）. As time of overflow continued, concentration ofdry season wastewater changged a little; average removal rate of SS and CODCrofcombined sewage in small rainfall intensity were87.76%and50%; SS、TP andCOD_Crremoval rate were98.68%、93.66%and92.58%in large rainfall intensityreaching discharge standard of discharge standard of pollutants for municipalwastewater treatment plant（GB18918—2002）; average sludge cake thickniss of threesorts of wastewater were5.0cm、2.7cm and9.4cm, moisture content of98.7%、99.1%and98.5%, rinse water volune of113.14L、56.57L and169.61L.