Isolation Of Nitrite-oxidizing Bacteria And Its Application In Aquaculture Water Treatment

The nitrite-oxidizing bacteria are Gram-negative eubacteria that are able to use nitrite as a solesource of energy and CO2as the main source of carbon. The nitrite-oxidizing bacteria catalyzes thesecond step of the nitrification--oxidize the nitrite to nitrate, which has critical ecology andapplicrtions value in wastewater treatment, especially in aquaculturals water treatment.In order to screening nitrite-oxidizing bacteria with high nitrite oxidation activity, and adapt toaquaculturals environment. A strain of nitrite-oxidizing bacteria, ZS-1, was isolated from the waterof coastal Pseudosciaena crocea rearing pond in ZhouShan, Zhejiang province. The strain wasidentified as Nitrobacter winogradskyi based on its phylogenetic analysis of its16S rRNA geneand nxrA sequence. Then, effects of environment factors, including pH; temperature; concentrateof ammonium-N, nitrite-N and nitrate-N on the nitrite oxidation activity were investigated. Afterthat, ZS-1was immobilized onto assembled filters for aquaculture water treating. The condition forbiofilm forming and the effect of hydraulic retention time (HRT) on nitrite-N removal ware alsoinvestigated.Under aerobic condition, the nitrite-oxidizing activity of strain ZS-1did not change obviouslyin the range of pH7~9, but was strongly inhibited by lower (pH6) and higher (pH10) pH values.The optimum temperature range is25℃~32℃, lower temperature made the adaptive phase longer,but did not affect the maximum nitrite oxidization rate. The nitrite-oxidizing activity of strain ZS-1started to be inhibited by ammonia or nitrate when their concentration respectively reached to25mg/L and100mg/L, but was not inhibited by high concentration of nitrite (500mg/L). Theinhibition was stronger with higher concentration of ammonia or nitrate. An interesting finding wasthat the nitrite-oxidizing activity was somewhat promoted by low ammonia concentration. Thepromotion will get weaker when the concentration of ammonium-N got higher. ZS-1were wellimmobilized onto the fillers at30℃, pH7.0-7.5in aerated medium within7days. When the HRTwas set at12h、6h、3h or1h, the removal ratio of nitrite in a synthetic wastewater was100%、98.77%、90.59%、59.02%, respectively. With a HRT of1h, about75%of the nitrite-N wasremoved from marine shrimp wastewater.