Study On Treatment And Disposal Technology Of River Sediment In Maozhou River Basin (Dongguan Part)

Sediment is an important component of natural river system ecosystems such as rivers and lakes.Excessive sediment deposition in river channel will easily weaken flood discharge capacity of river channel,increase water level,and easily cause flood disaster.At the same time,the pollutants in the sediment are constantly released into the water,forming secondary pollution.Therefore,the treatment of river sediment is an important link in the ecological restoration of rivers and lakes at present.Environmental dredging is the most common and effective way to treat sediment.How to treat the sediment produced by dredging has become an urgent problem to be solved.In this study,the sediment of the Maozhou River basin（Dongguan part）was selected as the research object,and the settling and filtration performance of the sediment was improved by adjusting the type,dosage and compound ratio of the dehydration conditioner.The settling rate of solid-liquid interface,30min settling ratio of bottom sludge,solid content of filter cake and specific resistance（SRF）were measured to evaluate the conditioning effect.After selecting the best dewatering conditioner,mechanical dewatering of the sediment is carried out with the plate and frame filter press for continuous operation for two months.The treatment and disposal scheme of the sediment is evaluated by monitoring each index of the output.Finally,the conclusions of this topic are as follows:（1）Determine the number of more common and toning effect is relatively good dewatering conditioner（Mg（OH）₂,AlCl₃,Ca（OH）₂,Fe Cl₃,KOH,PAM,fly ash,etc.）,and compare different kinds of dewatering conditioner through the experiment of Mao Zhou river basin（Dongguan part）river sediment,and the effects of dehydration,the results show that adding the dehydration conditioner can effectively improve nursing effect of river sediment.By measuring the sedimentation rate at the solid-liquid interface,the sediment settlement ratio of 30min,the solid content of the filter cake,etc.,the suitable dehydration conditioning agents were screened out,namely Ca（OH）₂,PAM and fly ash.The optimal dosage was 5g/L,0.04g/L and 8g/L,respectively.（2）Three kinds of conditioning agents Ca（OH）₂,PAM and fly ash were mixed and orthogonal experiment was carried out.The optimal dosage of compound conditioner Ca（OH）₂is 3g/L,PAM is 0.02g/L,and fly ash is 8g/L by measuring the sediment settlement ratio of 30min,the solid content of filter cake and specific resistance（SRF）.The results show that the minimum sediment settlement ratio is26.52%,the maximum solid content of the filter cake is 54.98%,and the minimum specific resistance（SRF）is 0.52×10¹¹m/kg.Compared with the use of a single conditioner,the conditioning effect of sediment has been significantly improved,the dosage of Ca（OH）₂and PAM has been significantly reduced,and the function of fly ash has been given full play,which is economical and reasonable,and can save costs.（3）The compound conditioner is applied in the actual dewatering and solidifying treatment and disposal project of river sediment.After two months of stable operation,according to the test results of sludge cake,residual water and other outputs,it can be seen that this set of dewatering and solidifying treatment and disposal scheme of river bottom mud runs well without failure,the outputs meet relevant standards and provisions,and the requirements of reduction,stabilization and harmlessness can be achieved,and the expected goals can be achieved.According to calculation,after the use of compound conditioner,the chemical cost is reduced by 12.08%and the efficiency of sediment treatment is increased by 15.79%,which has a certain application value in practical engineering.