Screening And Studying On Characteristic Of Bacteria Used For Purifying Water Quality Of Aquatic Water

We obtain 10 preponderant microorganisms with fort vitality by accumulating from mud and water in many areas' fishponds in Sichuan.Through sceond screening test, we obtain 1 microorganism which can obviously degrade organic matter and ammonia-nitrogen. The degradation rate of the strain reaches 56.8% and 21.5% in the denitrifies antiseptic aquatic wastewater which contains 30mg/L organic matter and 5mg/L ammonia- nitrogen. By bacteriological identificantion, the strain is identified as Bacillus firmus and named as SH-7.The results show that the strain of SH-7 has no haemolyticus on rats'5% blood plate .After 14 days, all the Mus musculus albus are healthily after drenched 0.5ml culture fluid whose concentration of SH-7 is 1×10⁹CFU/mL every time, and three times per day. Meanwhile, after 14 days, carps are survival and healthy after soaked in aquatic water which contains 1×10⁸ CFU/mL of SH-7.The experiment show that the strain of SH-7 has significantly inhibitory effect on the aquaculture-conditional pathogen-nic bacteria Aeromonas hydrophila(P<0.05).The experiment study the influence of environmental factor ,such as temperature,pH and dissolved oxygen on the degradation rate of organic matter and ammonia-nitrogen .When the pH is 7.0 and temperature is 30℃, the degradation rate of the strain to organic matter and ammonia nitrogen is strongest. And the degradation rate of the strain decrease with the increasing of culture medium volume.Through the experiment combining single-factor and orthogonal, we choose the best fermentation conditions and medium: glucose25g/L,soybean cake20g/L,MgSO₄1.0g/L,CaCl₂0.05g/L,K₂HPO₄2.0g/L,MnSO₄0.15g/L.The cultivante's temperature is34℃,initial pH is 7.2. shaking at 200r/min, after 22h of shaking acultivation,the number of bacillus reaches at 1.64×10¹⁰CFU/mL. Compared to the non-optimized medium, the number of bacillus has increased 978.9%.The dosage of the SH-7 test shows that, the optimization innoculation is1mL/m³ when the aquatic water contains 2.4×10⁴CFU/mL of chemoheterot-rophic bacteria. After using the SH-7 in aquarium, the number of SH-7 increased in crest-time after four and six days.the percentage of the SH-7 in the number of heterotrophic bacteria is 85%-90%,the number of heterotrophic bacteria in test group is lower in control group in 10-14d.The result of monitoring water quality show that the increment of ammonia-nitrogen,nitrite-nitrogen and organic matter in test group obviously lower than the control group(P<0.05); the increment of nitrate- nitrogen in test group has no difference with the control group(P>0.05).