Research On In Situ Control Of Odor Matters In Sediments Of Shenzhen River Using Calcium Nitrate

This thesis conducted experiments to evaluate the performance of in-situ control ofodor matters in sediments using calcium nitrate. Main odor matters included acidvolatile sulfide (AVS), geosmin (GEM),2-methylisoborneol (2-MIB) and total organiccarbon (TOC). Its influence on microbial community succession was also explored.Analytical instruments as UV and GC-MS were adopted for analysis of AVS, GEM and2-MIB in sediments and overlying water.Distribution of pollutants in Shenzhen River was investigated. The results showedthat the surface sediments was serious polluted with AVS and TOC, ranged from10to3680mg/kg and0.8%to4.6%respectively. It was identified that the contains of AVSand TOC in Surface sediments dredged near Luohu bridge were relatively high withvalues of3280mg/kg and4.6%.Surface sediments dredged near Luohu bridge along Shenzhen river were used asexperimental samples. Three dosages of1000mg-N/L,3000mg-N/L and6000mg-N/Lcalcium nitrate were tested, compared with calcium peroxide, sodium hypochlorite,hydrogen peroxide at oxidation-reduction equivalence of3000mg-N/L. Results showedthat injection of calcium nitrate can remove AVS with41.24%,99.94%,99.64%, theother oxidants can remove AVS with100%,91.84%and0%. TOC can be removedpartly with efficiencies as12.41%,2.30%,6.97%,14.63%,11.45%and10.82%.Related control efficiencies for GEM and2-MIB were38%~61%and-40%~30%respectively. If the dosage of calcium nitrate excessed3000mg-N/L, some ammonianitrogen, nitrate and nitrite will be released from sediments. If the dosage of calciumnitrate was below1000mg-N/L, some AVS would be reformed. Although calciumperoxide can remove AVS very efffectively, the pH value of both sediments andoverlying water would increse sharply to10.28~11.24, heavy metals might be released,the treated sediments were also of explicit biological toxicity.More experiments were conducted with seven dosages of calcium nitrate, resultsshowed that AVS can be removed completely within21days, however, when the dosagebelow1500mg-N/L, AVS would be reformed. TOC in sediments can be removed verylittle within21days. It was concluded that calcium nitrate is suitable for in situ control of AVS in sediments. The designed total dosage included those for complete removal ofAVS, partial removal of TOC within proposed treatment time, as well as approptiateextra dosage for sustainable control of desulfurication.Calcium nitrate can result in enhancement of-proteobacteria,-proteobacteriaand Bacillales with most of-proteobacteria restrained in sediments. Major functionalbacterial species, according to the fingerprint of16S rDNA, were identified asThiobacillus sp.,Thiobacillus thioparus and Thiobacillus thiophilus for AVS removal.Some bacterial species including Pseudomonas stutzeri, Shewanella baltica,Paenibacillus uliginis, Thermomonas fusca, Rhodanobacter sp. and Unculturedγ-proteobacterium may be of denitrification but not for AVS removal. Some bactericalspecies like Paenibacillus uliginis and Uncultured-proteobacterium were also ofsignificane in ammoniation during denitrification. This thesis is of technical andtheoretical guidance for in situ control of AVS in river sediments.