Sludge MFC For Continuous Excess Sludge Reduction And E-Fenton Driven For In Situ Antibiotics Degradation

With the growth of the world's population and the acceleration of urbanization,the output of domestic wastewater is growing with each passing day.For the moment,biological treatment is the dominant technology in wastewater treatment plants(WWTPs),which produces a large amount of excess sludge in the process of treatment,putting an extra burden on the ecological environment.However,the excess sludge contains abundant biomass energy,which cannot be extracted and utilized properly.Sludge microbial fuel cell(SMFC)can electricity by using biomass energy of the sludge in WWTPs and reduce the production of sludge,but it is difficult to realize continuous operation and the efficiency is relatively low.Besides,some antibiotics and other nonbiodegradable organics would be desorbed from sludge during the treatment and disposal process and release to the environment,which will cause secondary pollution to the aqueous environment.Antibiotics persisted in water environment not only have toxic effects on organisms but also can induce the production of resistant bacteria and resistance genes.In the light of of the problems above,an inclined-plate SMFC(InPSMFC)integrated with membrane filtration was constructed in this study,which achieved continuous wastewater treatment,sludge reduction,and energy production at the same time.Then,the energy produced by SMFC was further utilized to power electro-Fenton(E-Fenton)process and form an SMFC-E-Fenton system.On one hand,anode reaction of the system was used to reduce sludge production,release antibiotics in sludge during desorption and electricity generation process.On the other hand,generated electricity was used in situ to drive the E-Fenton process and degrade antibiotics in water.Finally,sludge reduction,energy recovery,and two-phase antibiotics removal was accomplished by the constructed SMFC-E-Fenton system.The specific research contents and results are as follows:Firstly,inclined plate anodes were installed in the middle of the reactor,which accelerated the sludge sedimentation,reduced the production of sludge and enhanced the electricity generation efficiency of SMFC.At the same time,hollow fiber membrane module was installed in the middle of cathode to improve the effluent quality,slow down membrane fouling by the action of cathode electric field and the obstruction effect of anode.The results showed that the power density of InPSMFC increased by 2.1 times and internal resistance was only 47.7%of normal SMFC.Sludge reduction rate reached 8.24×10-6-kg d-1,which was 1.5 times of normal SMFC.At the same time,the total resistance of membrane decreased by 33.8%,COD and nitrate-nitrogen removal efficiency reached 95.8%and 83.5%,respectively.Based on biomass energy extraction and sludge reduction of SMFC,biomass in sludege was further used to power E-Fenton reaction to treat antibiotics that are difficult to biodegrade in water.Fenton reaction occurs at the cathode,in order to enhance the stability of cathode,a novel grapheme polyacrylamide carbonized aerogel(?-FeOOH GPCA)was fabricated and was used as cathode of E-Fenton to degrade and mineralize sulfamethoxazole(SMX).The results showed that the ?-FeOOH GPCA had good conductivity,high porosity and electrochemically active surface area(EASA).The optimal material ratio and operating conditions of the electrode were obtained by optimizing the GO dosage,catalyst dosage,and the applied current intensity.Under optimal conditions,the degradation rates of SMX and TOC were 100%and 93.8±0.8%,respectively.Compared with the carbon felt(?-FeOOH CF)electrode,the degradation efficiency of ?-FeOOH GPCA was more stable during multi-batch experiments.The SMX and TOC degradation efficiencies of E-Fenton system with GPCA cathode still reached 99.9 ± 0.1%and 84.7±1.1%,respectively,at the last of multi-batch experiments.Finally,on the basis of SMFC sludge reduction and E-Fenton degradation,?-FeOOH GPCA was introduced into SMFC.SMFC was utilized to generate electricity to drive the E-Fenton process to construct the SMFC-E-Fenton system to degrade antibiotics with different adsorption properties.Unbiodegradable antibiotics were desorbed along with the consumption of sludge during the electricity generation process of SMFC,and then degraded and mineralized by E-Fenton process at cathode while consuming the electricity in situ.After 40 h treatment,the sludge reduction efficiencies while treating SMX and norfloxacin(NOR)were 6.2±0.3%and 5.7±0.8%,respectively,and the removal efficiencies of were 97.4±2.9%and 96.1±3.0%,respectively.Compared with anaerobic digestion process,residual SMX and NOR content in sludge decreased from 10.2±1.5%and 31.3±1.8%to 1.1±1.2%and 3.1±1.3%,respectively.Meanwhile,E-Fenton process could facilitate electricity generation of SMFC.While treating SMX and NOR,the maximum power densities were 472.2±11.5 mW m-2 and 43 1.4±15.6 mW m-2,respectively,which were 9.5%? 6.9%higher than normal SMFC.The results above demonstrated that the electricity generated in SMFC can be used in situ in the SMFC-E-Fenton system,sludge reduction and antibiotics degradation in both aqueous and sludge phases were accomplished at the same time.