Nitrogen removal efficiency of iron-carbon micro-electrolysis system treating high nitrate nitrogen organic pharmaceutical wastewater

The nitrate nitrogen removal efficiency of iron-carbon micro-electrolysis system was discussed in treating pharmaceutical wastewater with high nitrogen and refractory organic concentration. The results show that the granularity of fillings,pH,volume ratios of iron-carbon and gas-water,and HRT. have significant effects on the nitrogen removal efficiency of iron-carbon micro-electrolysis system. The iron-carbon micro-electrolysis system has a good removal efficiency of pharmaceutical wastewater with high nitrogen and refractory organic concentration when the influent TN,NH4+-N,NO3--N and BOD5/CODCr are 823 mg/L,30 mg/L,793 mg/L and 0.1,respectively,at the granularity of iron and carbon 0.425 mm,pH 3,iron-carbon ratio 3,gas-water ratio 5,HRT 1.5 h,and the removal rates of TN,NH4+-N and NO3--N achieve 51.5%,70% and 50.94%,respectively.

An internal circulation iron-carbon micro-electrolysis reactor for aniline wastewater treatment:Parameter optimization,degradation pathways and mechanism

Aniline is a vital industrial raw material.However,highly-toxic aniline wastewater usually deteriorated effluent quality,posed a threat to human health and ecosystem safety.Therefore,this study reported a novel internal circulation iron-carbon micro-electrolysis(ICE)reactor to treat aniline wastewater.The effects of reaction time,pH,aeration rate and iron-carbon(Fe/C)ratio on the removal rate of aniline and the chemical oxygen demand were investigated using single-factor experiments.This process exhibited high aniline degradation performance of approximately 99.86% under optimal operating conditions(reaction time=20 min,pH=3,aeration rate=0.5 m3·h^(-1),and Fe/C=1:2).Based on the experimental results,the response surface method was applied to optimize the aniline removal rate.The Box–Behnken method was used to obtain the interaction effects of three main factors.The result showed that the reaction time had a dominant effect on the removal rate of aniline.The highest aniline removal rate was obtained at pH of 2,aeration rate of 0.5 m^(3)·h^(-1)and reaction time of 30 min.Under optional experimental conditions,the aniline content of effluent was reduced to 3 mg·L^(-1)and the removal rate was as high as 98.24%,within the 95% confidence interval(97.84%-99.32%)of the predicted values.The solution was treated and the reaction intermediates were identified by high-performance liquid chromatography,ultraviolet-visible spectroscopy,Fourier-transform infrared spectroscopy,gas chromatography-mass spectrometry,and ion chromatography.The main intermediates were phenol,benzoquinone,and carboxylic acid.These were used to propose the potential mechanism of aniline degradation in the ICE reactor.The results obtained in this study provide optimized conditions for the treatment of industrial wastewater containing aniline and can strengthen the understanding of the degradation mechanism of iron-carbon micro-electrolysis.

Removal of TOC and Color in Bleaching Effluents from Straw Pulp and Paper Mill by Fe^0-H_2O_2 Process

TOC and color in the bleaching effluent from straw pulp paper process could not reach draining standard after its treatment by a biochemical process. In this study, advanced treatment by integrated micro-electrolysis （Fe^0） method and Fenton-like process was investigated under various conditions, i.e. pH, Fe/C ratio, initial I-I2O2 concentration and carrier gas. Results showed that Fe/C ratio（V/V = 1.5）, larger H2O2 dosage around 50 rag/L, lower pH（pH= 3） turned out to be particularly efficient. Temperature was a key parameter, remarkably increasing reaction rates. Carrier air not only improved reaction efficiency, but also saved H2O2 dosage. Chlorinated organic compounds could be reductive dechlorinated by Fe^0 reaction and oxidated by OH produced from Fenton process. The combination of Fe^0 and H2O2 reactions had been proved to be highly effective for the advanced treatment of such a type of wastewaters, and important advantages concerning the application in the study.

Treatment of Wastewater from Pharmaceutical Intermittent Production by Fe/C-Fenton-Hydrolysis Acidification-A/O Process

The design and running effect of treatment of wastewater from pharmaceutical intermittent production by iron-carbon（Fe/C）-Fentonhydrolysis acidification-anoxic/aerobic（A/O）process were introduced.The results of continuous operation showed that when the flow rate of the influent wastewater was 300 m^3/d,after the influent high-concentration wastewater（CODCrand NH4＋-N concentration were 35 000 and 1 000 mg/L,respectively）and medium-concentration wastewater（CODCrand NH4＋-N concentration were 1 500 and 100 mg/L,respectively）were treated by the process,CODCrand NH4＋-N concentration in the effluent decreased to 360-410 and 20-25 mg/L,respectively,and the quality of the effluent could meet the Grade III standard of Integrated Wastewater Discharge Standard（GB 8978-1996）.The combined process was proved to be an effective method to treat wastewater from pharmaceutical intermittent production,and its operation was stable.

Three-dimensional electro-Fenton system with iron-carbon packing as a particle electrode for nitrobenzene wastewater treatment

Traditional Fenton oxidation is an effective method for reducing pollutants that are difficult to degrade.Owing to the large amounts of Fe(II),acids,and alkalis added in the reaction,large amounts of Fenton sludge are produced,increasing treatment costs and restricting the method’s application.In this study,we developed a three-dimensional electro-Fenton system by adding iron-carbon filler and investigated the effects of different electrolytic cell structure arrangements,particle electrode dosages,sponge iron(SI)to granular activated carbon(GAC)dosage ratios,current densities,H_(2)O_(2)dosages,and cathodic aeration on nitrobenzene(NB)wastewater treatment.The optimal system conditions were a particle electrode dosage of 100 g/L,SI:GAC mass ratio of 3:1,current density of 30 mA/cm^(2),H_(2)O_(2)dosage of 50 mmol/L,cathodic aeration of 0.8 L/min,and hydraulic retention time of 120 min.The average NB removal rate and chemical oxygen demand reached 67.38%±1.05%and 70.60%±1.15%,respectively,for which the increase in Fenton sludge was 891.8 mg/L.Different from the traditional Fenton process,additional Fe(II)was not required in the process used herein,reducing iron sludge accumulation and lowering the operating costs of using Fenton sludge as a hazardous waste treatment.In addition,the process applied in this study was able to reduce the chemical amounts used and increase the treatment efficiency.The reductions in sludge treatment costs and secondary pollutants make the proposed process an efficient and sustainable alternative for treating NB wastewater.