Nutrients Release And Chemical Remediation Of Contaminated Municipal River Sediment

The contaminated municipal river sediment is one of the extrusive environment problem engulfing the global. The contaminated sediment just resulted from polluted river. It is the one of difficult to deal with sediment for municipal river pollution. The great deal of deleterious contamination which accumulates in sediment may be discharged via some exchange. It may become the second contaminative source to affect and restrict water quality. It has become a key question and to select effective remediation sediment technology for building municipal ecosystem and improving environmental quality.The sample of water and sediment collected from surrounding Tianjin region was analyzed in summer ant winter respectively. It reveals that the primary and secondary rivers of Tianjin have been seriously polluted. The secondary river sediment was much more polluted than primary river sediment. On the basis of polluted degree of municipal river sediment, the experiment of pollution releasing was carried out by means of collecting actual riverway sediment which was shelved in the experimental apparatus simulating riverway. It reveals that the water quality will keep well when the hydraulic retention time of riverway is 5 days. It is found that dissolved oxygen and disturbance(wave) are more prominent factors affecting phosphorus release. The phosphorus release amount is 3.7 time When the dissolved oxygen is 0.8mg/L vs 7.2mg/L.The remediation experiment was carried out on the basis of investigation and pollution release experiment. The experimental apparatus were prepared according to water seal principle. The remediation sediment experiment of different adding means and amount about calcium nitrate,calcium peroxide,PAC(Polyaluminium Chloride) was studied. It is evidence to inhibit phosphorus release in short term utilizing PAC, but it will be gradual wane after 17 weeks. Calcium peroxide also can inhibit phosphorus release during long time due to its slow oxygen release characteristic, but the water pH will be at 9~9.5. Calcium nitrate can inhibit phosphorus release during long time. The total phosphorus concentration was below 0.03mg/L during 20 weeks. The total nitrogen has been 5~6mg/L in the apparatus which was added 70g/m2 of calcium nitrate—N after 30weeks. The removal efficiency of sediment TOC was 7~8%. So the programme of adding calcium nitrate 70g/m2 and injecting to 10cm depth is best.The merit and demerit of different chemical medicine,adding means and adding amount was investigated involving ORP,sediment TOC,phosphorus fractions,heavy metal fractions and organic fractions at the first. The oxygenating environment of internal sediment was well-proportioned improved due to the favourable diffusibility of nitrate redical, so the removal efficiency of the surface and bottom sediment was unanimous. The heavy metal fractions of sediment hold the line after 30 weeks. It makes in-situ chemical remediation technology become possibly.The water quality model of calcium nitrate remediation was established employing multivariate regression. It may provide reference for actual riverway sediment remediation.