Study On Rapid Cultivation Of Aerobic Granules And Its Biosorption Of Heavy Metals

In company with the fast development of the metal plating,mining, dying, petrochemical and battery industries, a great deal of wastewater containing the excessibe dangerous heavy metal ions has been discharged into the environment and would engender the great harm to the environmental ecology and the human health. Due to abroad source of absorbent, no second pollution, big biosorption capacity, the fast biosorption speed and so on advantages, researchers pay more and more attention to biosorption method.The wastewater treatment technology with aerobic granules is a new technique developed within recent years, which can not only be applied to remove COD, ammonia, poisonous organic wastewater as well as the wastewater with phosphorus, but also be used to dispose the wastewater with heavy metal. Aerobic granules has become the highlight in the wastewater treatment study as a result of so many viture it has.The research including two parts, including rapid cultivation of aerobic granules an adsorption of heavy metals. The effects of 15% additional mature aerobic granules to the formation of aerobic granules by inoculating activated sludge and feeding synthetic municipal wastewater and the influences of pH, time, heavy metal ion concentration, rotate speed, temperature to the adsorption of heavy metals were investigated respectively.The results showed aerobic granules could form more rapidly when 15% mature aerobic granules put into the reactor. The formation of aerobic granules has two phase by inoculating activated sludge, first, the rapid formation of small granules with diameter from 0.1 to 0.3cm;Second, the relatively slow formation of small granules turn into big granules.The research results indicated that pH value was one of important effect factors to heavy metal biosorption.Biosorption was potent only among the fitting pH values. When pH value was very low, plentiful H+ made protonation in fungi surface and made the low biosorption capacity; when pH value was very high, the heavy metal ions existed as the insoluble oxide or hydroxide, the aim to remove heavy metals using biosorption method was not obtained. The optimal pH value was different from the heavy metal ions. The optimal pH value of four heavy metal ions biosorption is 4 to 6. The results of contact time of biosorption indicated that the biosorption process could take into two parts: the surface biosorption course and the slow intracellular accumulation. The heavy metal ions concentrations of solution descend quickly through the first phase, and then its biosorption capacity increase gently and gradually get equilibrium. Increasing temperature and rotating speed in the proper range can be benefit to the adsorption of four heavy metals, but, high temperature and rotating speed can reduce the adsorption of heavy metals.Biosorption equilibrium was studied, and Langmuir and Freundlich adsorption isotherm equations were used to fit single heavy metal. The biosorption equilibrium curves used the two equations to describe the biosorption of Cd2+,Zn2 and Cu2+ with aerobic granules, the correlation coefficient were 0.0.9665 and 0.9411,0.9764 and 0.9227,0.989 and 0.9837 respectively.The aerobic granules adsorption mechanism study showed EPS chelation and ion exchange play a important role in the adsorption of heavy matals. Two kinds of mechanisms take more than 70% of the adsorption capacity. Competing adsorption of mixed heavy metals leads to a reduction of the adsorption.