The Study On Isolation And Identification And The Effect Of Water Treatment Of Microorganism Decomposing Ammonia Nitrogen In The RAS Biological Filter

The development of factory recirculating aquaculture system (RAS) provides a thought to solve worldwide depletion of water resources and aquatic safety issues. Water treatment technology as a key link of RAS, determines the status of whole system. Biological treatment technology, which on the carrier of biofilter,can efficiently remove ammonia and nitrite, but the microorganism in biofilter are complex and diverse, whose community structure and mode of action is just like a black box. In this experiment, biofilms are taken from biofilters of Atlantic salmon RAS in East Ocean, Epinephelus nebulosus RAS and ♀Epinephelus fuscoguttatus×♂ Epinephelus lanceolatu RAS in Laizhou Mingbo, through microbial enrichment and separation,3 bacteria from Atlantic salmon RAS,5 bacteria from EpinephelusnebulosusRhS and 6 bacteria from ♀Epinephelus fuscoguttatus×♂ Epinephelus lanceolatu RAS are acquired. Preliminary these 14 bacteria by Gram stain, exclusion of positive bacteria,later identify by 16SrRNA gene sequence analysis, Identification of bacteria belonging to four kinds, they are Labrenzia aggregata, Acinetobacter venetianus, Massilia suwonensisand Sinomicrobium oceani, there are 1 from Atlantic salmon RAS (Labrenzia aggregata),2 from Epinephelus nebulosus RAS (Labrenzia aggregata, Acinetobacter venetianus), and 4 from ♀ Epinephelus fuscoguttatus×♂ Epinephelus lanceolatu RAS (Labrenzia aggregata, Acinetobacter venetianus, Massilia suwonensis, Sinomicrobium oceani).The 2 bacteria from Epinephelus nebulosus RAS are selected to explore the effects in sewage treatment.This study consisted of two parts. First part is to explore the effect of ammonia removal by different concentrations of bacteria in simulate biofilter. The experiment carried out in a glass tank, in which simulated sewage was added, water temperature 25±1℃, pH 7.5, the two experimental groups Labrenzia aggregata and AcinetobacTer venetianus (hereinafter to be referred as L and A) 5ml,10ml, 20ml were added to six groups, each set of three parallel concentration, 20ml of normal saline were added in control group. Experimental cycle is 27 days, measures the concentration of ammonia and nitrite every two days. The results are as follows:After adding these two strains of bacteria, ammonia in water tended to decrease, and at the end of the experimental cycle, final values of ammonia and nitrite in each experimental group have no significant difference (P>0.05), at the beginning of experimental cycle, ammonia removal of 20ml broth L quickly than the 5ml and 10ml broth L, the ammonia curve of 5ml broth A is similar to 20ml broth A. The removal efficiency of ammonia nitrogen of two strains of bacteria increases by 25%-34%than the blank group. The result explain that efficiencies of ammonia nitrogen removal of three concentrations of broth L are roughly the same,20ml broth reacts faster,5ml and 10ml broth save cost, we can select the appropriate concentration according to actuality.The second part is to explore the effect of ammonia removal by single and mixed broth in simulate biofilter. The experiment carried out in recirculating water system indoor, in which simulated sewage was added, water temperature 25℃±1℃, pH 7.5, system cycling time of 35min. Three experimental groups were 20ml broth L,20ml broth A and (10ml+10ml) mixed broth of L and A, the broth above were added to three groups of tanks, each group consisted of three parallel experiments.20ml of normal saline were added in control group. Experimental cycle is 19 days, measures the concentration of ammonia and nitrite every two days. The results are as follows:after adding the broth, ammonia of mixed broth in water always declined, whose downward trend and speed are better than two single broth.At the end of the experimental cycle, final values of ammonia and nitrite in each experimental group have significant difference (P<0.05), the removal efficiency of mixed broth is 45% higher than that of blank group, so this is better than single broth in rate and effect of ammonia nitrogen removal, indicating that the two strains bacteria from same system are synergistic in terms of water purification.The experimental results are realistic for understanding the mode of action of bacteria in the biofilter and maintaining the biofilter running efficiently, and also provide a theoretical basis for optimizing the capacity of water treatment of biofilter.