Growth Characteristic Research Of Moderate Halophilic Bacteria In The High Salinity Wastewater Treatment

High salinity wastewater is one of the extremely unmanageable wastewater, in additionto containing a large amount of inorganic salt ions (Na⁺, Cl^-, SO₄^2-, Ca²⁺, and other ions),these wastewater also includes high concentrations of organic contaminants. At present, thetreatment method of saline organic wastewater mainly includes: physic chemical method andbiological method. Due to such a high content of organic pollutants in wastewater, generalphysic chemical method is less effective and large energy consumption, high cost, biologicaltreatment has the characteristic of economical, efficient and environmentally friendly, is theprefered treatment method, but the conventional biological treatment can not satisfied theprocessing requirement. Lots of research results show that domesticated active sludge caneffectively remove the organic matters in sewage in a certain salinity range, but salinity rangeof the domesticated salt-tolerant microorganism can withstand is limited, and thedomesticated cycle is long. Therefore, in the biochemical treatment of high salinitywastewater, the direct utilization of halophilic bacterium which grows in high salinityenvironment is a fast and effective method. At the same time, the actual high-salt wastewaterquality is unstable, salinity fluctuation is large, suddenly increasing and decreasing of salinitywill cause the expiration of biological systems, this problem is needed to solved urgently.Thus this study took a moderately halophilic bacterium Halomonas sp. STSY-3asresearch object, simulated the salinity fluctuation of actual high salinity wastewater by NaCl,adopted shake flask experiment to simulate the SBR reactor, utilized Monod and Haldanemodels to discuss the bacterial strain growth and organic matter degradation process under thesalinity change of high-salt wastewater, and established the kinetic models of this strain underdifferent salinity. Meanwhile, partition the growth of STSY-3based on the influence ofsalinity on bacteria growth and organic matter degradation ability, and proved the conclusionby test methods such as electronic scanning electron microscope and flow cytometryinstrument, which had the practical significance to the organic matter degradation under thelinity fluctuation. Main research conclusions are as follows:（1） The moderately halophilic bacterium Halomonas sp. STSY-3belongs to Halomonas,bacillus, Gram-negative bacteria. Its suitable growth salinity range is2%⁹%, among them7%is the optimal salinity. STSY-3obtained the maximum amount of growth under theoptimal salinity （7%, by NaCl）, OD₆₀₀is2.56, under0%salinity and34%salinity, the OD₆₀₀were only0.47and0.06respectively. （2） The growth kinetic of Halomonas sp. STSY-3was fitted by the Monod equation,glucose in medium component was the restrictive substance, established the bacterial growthkinetic under different salinity and compared the model parameters K_S, μmax. The analysisresults show that: The growth kinetics of moderately halophilic bacteria STSY-3was goodmatch with the Monod equation, the experimental results and the kinetic model calculatedvalues was basically corresponding; under the optimal salinity, bacterial cells and glucose wasaffined very well, saturation constant K_S=0.0082g/L, the maximum specific growth rateμmax=2.257h-1. Compared the model parameters K_S, μmaxand the impact of salinity on thegrowth of moderate halophilic bacterium STSY-3, there are three apparent partition of thegrowth of STSY-3: the optimal salinity area （salinity2%to9%）, halophilic transition zone（salinity9%to20%） and the growth inhibition zone （salinity≤2%or≥20%）.（3） The experiment studied the inhibition of phenol on the strain and the impact of salinityon the phenol degradation, the growth kinetics of STSY-3in phenol degradation process andthe phenol degradation kinetics were fitted by the Haldane equation. Experiment resultsshowed that: Accompanying with the gradually increasing of phenol concentration the effectof phenol on the bacteria growth turned promoting to inhibition, when the phenolconcentration in the medium is slow （＜60mg/L）, phenol as a carbon source, can promote thecell growth, when the phenol concentration is high （＞300mg/L）, the phenol obviouslyrestrained the cell growth. The phenol degradation ability of STSY-3was obviously affectedby the salinity, under the optimal salinity7%, the phenol degradation rate was highest and canreach to50%around with120hours, and the phenol degradation rate decreased with theincreasing salinity, when the salinity is <2%or>20%, the strain cannot degrade phenolbasically. The growth kinetics and the phenol degradation kinetics of moderately halophilicbacteria STSY-3in the phenol degradation process were good match with the Haldaneequation, compared the model parameters K_S, μmax, Kiand the impact of salinity on thegrowth of moderate halophilic bacterium STSY-3, there are three apparent partition of thegrowth of STSY-3in the same.（4） In order to study the organic matter degradation ability of the strain in the wastewater,the moderately halophilic bacterium Halomonas sp. STSY-3was throwing into the artificialsimulation wastewater and adopted shake flask experiment to simulate the SBR reactor, thesynthetic wastewater was divided into two categories: one with glucose as the target organiccompound, one is based on phenol as the target organism. The experimental results showedthat: The organic matter degradation ability of STSY-3was obviously affected by the salinity,under the optimal salinity7%, the degradation rate of glucose and phenol were highest which can reach to50%and20%respectively within120hours, and the organic matters degradationrate decreased with the increasing salinity, when the salinity was＜2%or＞20%, thedegradation rate of glucose and phenol were lower than30%and10%respectively. The extraimpact factors clearly affect the organic matter degradation ability of STSY-3in the syntheticwastewater, among them betaine concentration and inoculums amount were the greatestimpacts, when the extra betaine concentration reached to1.0g/L, glucose and phenoldegradation rate within120hours were more than90%and35%respectively, when theinoculation amount reached to10%, glucose and phenol degradation rate within120hourswere more than t95%and50%respectively. Compared the model parameters and the impactof salinity on the growth of moderate halophilic bacterium STSY-3, there are three apparentpartition of the growth of STSY-3in the synthetic wastewater, which was accordance with theresults in the medium.（5） The study utilized scanning electron microscopy and flow cytometry instrument toobserve the three partitions （the optimal salinity area, halophilic transition zone and thegrowth inhibition zone） which were mentioned above. Experimental results showed that: Thesalinity seriously impacted the structure of the moderately halophilic bacterium Halomonas sp.STSY-3, under the optimal salinity7%, the surface of bacteria was full, under0%salinity, thebacteria form was irregular and there were many fragments, under20%salinity, the size ofbacteria is obvious shorten. The salinity changes had different degree impact on the growth ofthe moderately halophilic bacterium Halomonas sp. STSY-3, under the optimal salinity7%,the percentage of living cells was highest and up to77.7%, from the salinity range7%to0%and7%to25%, the percentage of living cells was declining, the number of damaged cellswas increasing, under0%and25%salinity, the percentage of damaged cells were97.4%and99.6%respectively.Based on the experimental results above, there are three apparent partition of the growthof the moderately halophilic bacterium Halomonas sp. STSY-3: the optimal salinity area（salinity2%to9%）, halophilic transition zone （salinity9%to20%） and the growth inhibitionzone （salinity≤2%or≥20%）, which was corresponding confirmed by SEM and flowcytometry instrument. The laboratory model parameters and salinity partitions were very practical significance to the biological treatment of high saltinity wastewater.