| In those economically developed coastal cities, seawater can be used as flushing water and industrial water which can alleviate the pressure of fresh water shortage. However, high salinity of the wastewater containing seawater has serious effect on the biological treatment process, especially on its nitrification effectiveness. Therefore, it is necessary to develop an available biological process for treating the saline wastewater containing seawater. In this study, a BAF process packing with oyster shell was employed to investigate nitrification acclimation performance on removal of ammonia containing in real seawater and simulated seawater. The experiment was carried out in the sequencing batch and continuous operation. The feasibility on stable nitrification process in the saline wastewater treatment was discussed and the mechanism on accomplishment of salt-tolerant nitrification process was studied. The main results were described as follows:1. The nitrification performance on which a sequencing batch aeration biofilter (SBABF) packing with oyster shell removed ammonia from the wastewater containing real seawater was investigated using different parameters, such as seawater containing rate, glucose and ammonium concentrations in influent. Results showed that SBABF removed more than95%of ammonia at seawater containing rate ranging from40%to100%. In the seawater salinity acclimatized nitrifying bacteria, the tolerability of ammonia oxidizing bacteria (AOB) exhibited higher than that of nitrite oxidizing bacteria (NOB). When seawater containing rate was higher than70%, the activity of NOB decreased obviously by seawater salinity. At the higher seawater salinity, the decrease of both glucose and ammonia concentrations in influent could increase the activity of NOB. Both AOB and NOB in the suspended sludge and biofilm on the shell involved in ammonia removal, and their activities in the biofilm was higher than that in the suspended sludge.2. The acclimation mechanism was studied by using non-salt nitrifying sludge as seed biomass at various salinity levels in continuously feeding simulated saline wastewater containing ammonia. In addition, the change of activities of both AOB and NOB during the acclimation operation period were investigated at various BAFs, which partly inoculating with the shell attached the salt-tolerant nitrifying bacteria in biofilm, as well as the mangrove sediment sludge. The populations of salt-tolerant microbes grew at various saline conditions in this process were analyzed. The mechanism on accomplishment of steady and complete nitrification of the shell BAF process by acclimation operation with the seawater salinity was discussed. The results showed that:1) At ammonia concentration of50to200mg/L, the non salt-tolerant nitrifying bacteria in the oyster shell BAF was able to tolerate the salinity of10and20g/L NaCl in influent within a relatively short period. Both the suspended sludge and biofilm at the oyster shell surface were observed in each BAF. At the NaCl concentration of30g/L in influent, we observed that the biofilm and suspended sludge disintegrating and re-building occurred in forming the newly salt-tolerant biomass during the whole acclimation period. The activity of AOB recovered faster than NOB, and the acclimation period needed one to two months.2) In two BAFs at the beginning of acclimation operation, one was packing with shell without salt-tolerant biofilm attached, another one was packing with shell with salt-tolerant biofilm attached, the volume ratio of biofilm attached shell to fresh shell was1:3. We found that to achieve the stable and complete nitrification at the influent concentration of ammonia and NaCl of50mg/L and35g/L, the acclimation period for those BAFs needed24d and20d, respectively.3) In the BAFs inoculating with mangrove sediment sludge A and B, they needed45d and58d respectively to achieve the complete nitrification at the influent concentration of ammonia and NaCl of50mg/L and35g/L. In BAF inoculating with sediment sludge A, the activity of NOB was inhibited significantly, whereas the activity of AOB restored quickly to normal level. In BAF inoculating with sediment sludge B, the activity of AOB restored to even higher level, resulting to excessive accumulation of the nitrite while the nitrification performed stably. Nitrite accumulation rate reached its maximum at58d, and the ratio of nitrite in effluent to ammonia in influent was up to159%.4) During the acclimation period, MLSS, protein and DNA in EPS in the nitrifying sludge varied significantly. We found that the protein and DNA demonstrated opposite trend with MLSS. 5) Both β-Proteobacteria and γ-Proteobacteria were identified in all BAFs. In the BAFs, which inoculating with the carrier at the1:3packing ratio of the shell with and without salt-tolerant biofilm to fresh shell, the dominant specie in saline acclimation nitrifying sludge was β-Proteobacteria. In addition, in the BAFs, which inoculating with the carrier at the3:1packing ratio of the shell with and without salt-tolerant biofilm to fresh shell, the dominant species in saline acclimatized nitrifying sludge was γ-Proteobacteria. In the BAFs, which inoculating with mangrove sediment sludge, the dominant species in complete nitrification sludge was Flavobacteriia. |
PDF Full Text Request