| Heavy metal is a kind of poisonous and persistant pollutant whichendangers environment and human beings and has become a urgentproblem. There are many methods for treating heavy metal wastewaterare more, biological method,howere, has many advantages such aslow-cost and environmental friendly by purifying water through mutuallyaction between biology organism or its metabolize product and heavymetal ions. In this research, metabolizing activity of microorganism isused to remove heavy metal in wastewater by forming precipitatin,takingsulfate-reducing-bacteria (SRB) as a representation. In the anaerobiccondition SRB could deoxidize sulfate, changing sulfate to HS- and heavymetal the form of insoluble metal-sulfate-sediment to remove. There is noneed to add extra sulfate because heavy metal mostly exist in form ofsulfate. Method of SRB exists two deficiencies at present.First, being anow available technology, either free bacteria or Carrier-style SRB, it isdifficult to avoid the poisonous effects of the metal ions on SRB becauseSBR gets in touch with metal ions of wastewater directly; Second, theorganic carbon source for SRB growth which leads to high COD ofdischarged water is very difficult to make complete use. On the basis ofthis, the technology of inner carbon source of SRB sludge immobilizedpellets (ISIS) could realize a low-cost and high effect of heavy metalwaste water treatment method, reaching the requirement of wastewaterdischarging. In this techmology, the organic nutrition source needed inSBR could be immobilized inside the SBR sludge, through this goodenvironment for SBR growth was constructed inside and outside thepellets.Not only it is able to avoid metal ions poisoning SRB sludge butalso it resolves the problem of the organic contamination. At the sametime, the SRB sludge maks use of the nutrient substance more efficiently.In this research, on the premise of chooing the most suitable sludgefor sulfate-reducing-bacteria (SRB) and the best technological parametersof the technology of SRB sludge immobilized pellets, take heavy metalions (Cu2+, Zn2+, Cd2+)as main object of the study, the research ondynamics is primarily explored, providing the important theory basis to the treatment of heavy-metal wastewater in the technology of SRB sludgeimmobilized pellets. Concrete contents include:1. Choosing the suitable activity sludge as technology of immobilizewith sulfate-reducing-bacteria for the premise condition, makes use ofimmobilized SRB sludge beads to have penetrated into this researchcomparatively to heavy metal ions respectively. Immobilized SRB sludgebeads with after oxidation ditch activated sludge and waste activatedsludge are domesticated are having the ability disposing of heavy metalion in the waste water, the zinc and the cadmium can get the treatmenteffect of 90% without exception in pH=6-7 range. But effect ofimmobilized SRB sludge beads with waste activated sludge is obviouslybetter than oxidation ditch activated sludge.2. The immobilized SRB sludge beads of inner cohesive nutrientsource were prepared using Polyvinyl Alcohol(PVA) as entrapment agent.The optimal conditions were chosen in terms of the mechanical stability,mass transfer, and difficulty of forming beads ,and function parameterhave inspected an impact of addition CA, SiO2, CaCO3, PAC to SRBsludge beads step by step from childhood, have improved cross-linkedagent boric acid pH further and have added an impact of metal salt overcross-linked process,. And the biology-physical-chemistry capability ofimmobilized beads was improved by adjusting the pH value of boric acidand appending metal salt. In addition, the treatment of heavy-metalwastewater by immobilized beads was investigated. The result shows thatimproved PVA-boric acid was considered the best support And theoptimal conditions are 15% PVA solution, 25% entrapping agents ratios,3mm diameter,30h in saturated boric acid solution, and 0.15% sodiumalginate,2%SiO2,0.5%CaCO3 was added to improve the mass transferand its durability. The pH value of Saturated boric acid solution adding2% CaCl2 is 6-7.The sorbent of inner cohesive nutrient source is 3%Power Activity Carbon(PAC).3. The effect of initial pH value and beads and liquid compoundproportion amounts on reaction rate were confirmed with the change ofsulfate concentration in the process of bio-reduction being studied indetails. Kinetic equation in each condition was established and the corresponding apparent activation energy was also calculated. The resultsindicate that kinetic equation of sulfate reduction by sulfate-reducingbacteria (SRB) is V=-dC/dt=0.08056C .The reaction rates areapproximately same under pH value of 6 to7 and decrease gradually whenpH＜4 and pH＞10. The reaction order of sulfate reduction in alkalinemedia by sulfate-reducing bacteria (SRB) is one. The reaction rateconstant decreases and the apparent activation energy increases alongwith the decrease of beads and liquid compound proportion amounts.Meanwhile, the optimized technological conditions was obtained, i.e.,temperature 35℃, pH=6-7 and 1:10(g/mL)with ratio of beads to liquid.4. Restores with the dynamics of sulfate-reducing-bacteria treatmentsulfate has got a first step for the premise, the study of SRB sludgeimmobilized beads to heavy metal ion (Zn2+,Cd2+, Cu2+) dynamics hasgot some progresses. Result is indicated: Different heavy metal ion (Zn2+,Cd2+, Cu2+) have different the dynamics equation in the temperature 35℃,pH6-7, beads liquid matches condition being 1: 10 (g/mL) roughly, beingrespectively: VZn2+=-dC/dt=0.01112CZn2+1.57153VCd2+=-dC/dt=0.006497CCd2+2.1357 VCu2+=-dC/dt=0.004816CCu2+1.83604Make Arrhenius equation tired out according to the big mound, theapparent activation energy and K being unlike the heavy metal ion (Zn2+,Cd2+, Cu2+) are respectively with temperature relational expression:Ea(Zn2+)=17.46kJ/mol, belong to an irradiation under the control of, andK(T)=exp(0.96)exp(-2099.71/T);Ea(Cd2+)=28.83kJ/mol, belong to commixture under the control of, andK(T)=exp(6.22)exp(-3468.02534/T);Ea(Cu2+)=22.62kJ/mol, belong to commixture under the control of, andK(T)=exp(3.47)exp(-2720.38/T)。... |
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