The Study On Sulfate-reducing Reactor

The sulfate-containing wastewater which is more difficult to deal with has drawngreat attention at home and abroad. The anaerob ic biotechnology using sulfate-reducingbacteria is widely applied to the sulfate-containing wastewater treatment field. For thebiological desulfurization process, Sulfate-reducing process is the first and the mostcritical step. How to ensure the efficiency of sulfate-reducing bacteria to improve theconversion rate of sulfate in sulfate-reducing phase reactor has become a majorconstraining factor in biological desulfurization process. This paper studiedsulfate-reducing unit, utilizing the most widely used and sophisticated reactor the Upflow Anaerobic Sludge Blanket （UASB） and Anaerobic internal circulation reactor （IC） asa basic design model and combining the advantages of the UASB reactor and IC reactordesigned an improved reactor for sulfate-reduction.The granulation of granular sludge can be used as a sign of a successful start of thereactor. The SRB granular sludge must be fostered in the reactor in order to ensure thehigh stability of the process of sulfate reduction in sulfate-reducing reactor. In the start-upphase of the reactor, simulating sulfate wastewater of the manual configuration was used,T=35°C,pH=7.0，COD:N:P=300:5:1，adding trace elements liquor. According to formchanges of the sludge in the start-up process, the start-up process can be divided into:Sludge acclimation phase, the initial stage of the formation of granular sludge and theformation of granular sludge phase. The changes of pH, sulfate load, effluent SS andsludge phase were monitored at different stages of start-up phase and the reactoroperational parameter, liquid up-flow velocity （Vup） was studied and optimized. After asuccessful start of the reactor, the performance indicators of the formed SRB granularsludge were studied.In the operational phase of the reactor, the factors of the influence of thesulfate-reduction were studied, and in particular, the sulfate-reducing conditions wereanalyzed with the consideration of the low carbon-sulfur ratio. Then the sulfate reductionkinetics was studied and the related model was established.The main conclusions and dataare as follows:（1）After the purified enrichment, the size of the SRB is0.35μm⁰.55μm×1.0μm³.0μm. There are several forms such as oval, short rod, arc rod and rod-shaped form. It’sshowed that the logarithmic growth phase for the SRB is during28h⁵7h after inoculation,which is the main source of the sludge of sulfate reduction phase.（2）The successful start of the sulfate-reducing reactor lasts113days. In the sludgeacclimation period, sulfate load is within2.5kg/m³·d and the effluent SS varying from50¹00mg/L. There Appears large flocculent sludge with some free-state micro-organismsand non-granular sludge. In the initial stage of the formation of granular sludge, the largest negative of the sulfate in reactor is7.71kg/m3·d, pH=7⁸and the effluent SS isabout100mg/L, Some sludge has changed from flock into granule. In the granular sludgeformation stage, the sulfate load of the latter period of operation maintains over10kg/（m3·d）, pH maintains at neutral to slightly alkaline range, the effluent SS remains atabout at50mg/L, the size of the granular sludge particle of the lower sludge bed in reactorhas increased, the granular sludge in middle layer begins granulation, the granular sludgein upper layer performs to be the mixture of the activated sludge and small-size granulesludge and there exists the free micro-organisms in the upside.（3）The optimal ascending velocity of reactor in the start-up phase is0.12m/h and0.16m/h in the stable operation phase, respectively.（4）In the start-up phase, the number of granular sludge in the reactor increases withthe running time, the particle size ranges from0.69mm to0.9mm and the sedimentationvelocity （SV） is also increases with the average settling velocity of56m/h.（5）Within the influent sulfate concentration varying from0⁸00mg/L, SRB growthkinetics model with sodium lactate as the carbon is V=0.004S-0.0112, sulfate reductionrate is V_max=0.286gVSS·d. In the sulfate reduction process, the substrate reductionkinetic model is1/v=K_S/V_max*1/S_e+1/V_max in which V_max=0.455d^-1and K_S=1.712g/L.