Recycling Of Biological Activated Carbon Which Is Saturated In Water Plant’s Biological Activated Carbon Filter

This study received "Second five" special water project-"Guarantee technology and comprehensive demonstration of South-to-North Water TransferShandong area’s research drinking water safety" (2012ZX074074-003) support. Saturation biological activated carbon in Quehua Waterworks was set as the research object. Analysis of the effect of three kinds of regeneration method for regenerating biological activated carbon (BAC), on this basis, we proposed Microwave regeneration methods for biological activated carbon.Microwave, ultrasonic, solvent regeneration BAC tests showed that the affecting factors of microwave regeneration significantly follow the descendent order as:time> microwave power> gas flow rate> AC mass, the preferred conditions were time of 30 min, microwave power of 500 W, gas flow rate of 0.25 m3/h and AC mass of 10 g. The affecting factors of ultrasonic regeneration significantly follow the descendent order as:temperature> power> pH> time, the preferred conditions were temperature of 45℃, power of 90 W, pH of 1 and time of 15 min. Optimum operating conditions for the solvent regeneration was lOg activated carbon placed in 200 mL regenerated solution of NaOH:CH3COOH which mass ratio was 1:50 at 40℃ condition and oscillated for 6 h.Under the optimum conditions, ilodine value recovery rate of activated carbon by microwave regeneration(RAC-1), activated carbon by ultrasonic regeneration(RAC-2), activated carbon by Solvent regeneration (RAC-3) were 97.2%,73.5%,76% respectively. BET specific surface area of RAC-1, RAC-2, RAC-3 were 842.3 m2/g,747.01 m2/g,749.9 m2/g respectively; the total pore volume were 0.547 cm3/g,0.517 cm3/g,0.497 cm3/g respectively. The number of the basic, acidic carboxyl group and phenolic hydroxyl functional groups of new activated carbon(UAC) were 0.29 mmol/L,1.19 mmol/L,0.36 mmol/L,0.03 mmol/L respectively,0.76 mmol/L,0.89 mmol/L,0.51 mmol/L,0.66 mmol/L of SAC,0.88 mmol/L,0.39 mmol/L,0.22 mmol/L,0.27 mmol/L of RAC-1,0.84 mmol/L,1.01 mmol/L, 0.6 mmol/L,0.63 mmol/L of RAC-2,1.39 mmol/L,0.69 mmol/L,0.44 mmol/L,0.50 mmol/L of RAC-3, as can be seen from the results of the distribution of the activated carbon surface functional groups carbon, the number of carbon surface basic functional groups increasing in favor of the adsorption of hydrophobic and weakly acidic organic compounds, surface acidic functional groups contribute to increasing the hydrophilic and weakly basic organic adsorption. SEM results show, burn marks and obvious cracks appeared on the RAC-1 surface, there was no significant change on RAC-2 surface morphology, RAC-3 surface becomes smoother. Water content of RAC-1, RAC-2, RAC-3 were 1.2%,3.3%,2.4%, ash contents were 12.13%,10.75%,8.24%, strength reached 84%,85%,87%, respectively, pH were 8.5,6.5,8.9, respectively, more water molecules will directly affect the activated carbon adsorption of other substances, increasing of the ash content will reduce the activated carbon adsorption. From the iodine value, surface functional groups, surface morphology and other physical properties of the comparison can be seen, microwave regeneration is the best.The shortcomings of solvent regeneration was regenerating not thorough enough and pores easy to pluging, while microwaves can enter inside of activated carbon, heated from the inside features, thereby obtaining " Solvent-Microwave" activated carbon regeneration. To compared URAC which is obtained by" Solvent-Microwave" Regeneration method and HRAC which is obtained by thermal regeneration method, iodine value were restored to 853.3 mg/g and 811.4 mg/g; BET specific surface area was 836.42 m2/g,878.12 m2/g; the total pore volume were 0.547 cm3/g,0.513 cm3/g, increasing of specific surface area of activated carbon made adsorption capacity improved; the number of the basic, acidic carboxyl group and phenolic hydroxyl functional groups of URAC were 0.29 mmol/L,1.19 mmol/L,0.36 mmol/L, HRAC were 0.29 mmol/L,1.19 mmol/L,0.36 mmol/L, the removal rate of organic compounds by both URAC and HRAC is fast the equilibrium state can be achieved within two hours, removal rates of CODmh were 62.5%,56.3%, while removal rates of UV254 were 62.5%、56.3%.Among the traditional methods, regeneration microwave method of regeneration BAC superior ultrasonic method and the solvent method. "Solvent-Microwave" Regeneration is better than thermal regeneration method. "Solvent-Microwave" regeneration regeneration regeneration, although better than the microwave, the iodine value recovery rate increase of 0.9% only, no significantly change in surface area. Therefore, in practice, from the operational feasibility and economic point of view, you can select the microwave regeneration of biological activated carbon regeneration directly.