An analysis of the bacterial community in a membrane bioreactor fed with photo-Fenton pre-treated toxic water

A photo-Fenton-membrane bioreactor (MBR) coupled system is an innovative tool for the treatment of wastewater containing high quantities of contaminants. In this paper, wastewater with 200 mg l^?1 of dissolved organic carbon (DOC) of a selected mixture of five commercial pesticides: Vydate^®, Metomur^®, Couraze^®, Ditimur-40^®, and Scala^® was treated by combining photo-Fenton and MBR. The effect of photo-treated pollutants on MBR operation was investigated by studying the population changes that occurred with time in the activated sludge of the biological system. Pre-treatment with photo-Fenton was carried out (only up to 34% of mineralization of DOC) and, after MBR treatment, 98% of biodegradation efficiency was obtained. During the biological treatment, little changes in the activated sludge population were detected by DGGE analysis, maintaining acceptable biodegradation efficiency, which points out the robustness of the MBR treatment versus changes in feed composition.     

Dyestuff wastewater treatment using chemical oxidation,physical adsorption and fixed bed biofilm process

Fenton’s oxidation and activated carbon adsorption were examined as pretreatment processes for dyestuff wastewater having high salinity, colour, and non-biodegradable organic concentrations. In this work, each wastewater stream produced by individual production processes was classified as streams R1, R2, and R3. The stream having a value of BOD₅/COD lower than 0.4 was pretreated by Fenton’s oxidation or activated carbon adsorption to increase the ratio of BOD₅/COD which indicates biodegradability. For Fenton’s oxidation with one stream having a value of BOD₅/COD lower than 0.4, the optimal reaction pH was 3.0 and the minimum dosing concentration (mg l⁻¹) of H₂O₂:FeSO₄·7H₂O was 700:3500. Stream R3, which consisted mainly of methanol was efficiently treated by activated carbon adsorption. The ratio of BOD₅/COD was also increased to 0.432 and 0.31 from 0.06 in Fenton’s oxidation and activated carbon adsorption, respectively. A biological treatment system using a fixed bed reactor was also investigated to enhance biological treatment efficiency at various hydraulic retention times, pretreatment conditions by Fenton’s reagent and salt concentrations by dyestuff wastewater. In addition, the efficiency of Fenton’s oxidation as a post-treatment system was also investigated to present a total treatment process of dyestuff wastewater. As the influent COD and salinity were increased, the effluent SS and COD were consequently increased. However, as the microorganisms became adapted to the changed influent condition, the treatment efficiency of the fixed bed reactor quickly recovered under the high COD and salinity since the microorganisms were well adapted to toxic influent conditions. A wastewater treatment process consisting of chemical oxidation, activated carbon adsorption, fixed bed biofilm process and Fenton’s oxidation as a post-treatment system can be useful to treat dyestuff wastewater having high salinity, colour, and non-biodegradable organic concentration.     

Integrated biosorption and photocatalytic oxidation treatment of di(2-ethylhexyl)phthalate

Di(2-ethylhexyl)phthalate (DEHP), a toxic phthalate ester, is a ubiquitous contaminant due to its extensive use and persistence. No available treatment method can cost-effectively remove it from industrial wastewater. In a previous study, DEHP was effectively removed from aqueous solution by adsorption onto the biomass of selected seaweed, i.e., beached seaweed and Sargassum siliquastrum. Since biosorption cannot detoxify DEHP, the degradation (and detoxification) of desorbed DEHP from seaweed biomass by photocatalytic oxidation (PCO) was attempted. The first part of this study was to optimize the conditions for the degradation of desorbed DEHP in aqueous solution by PCO. Under optimized conditions, a total degradation of 20 mg/L of DEHP was achieved within 45 min. The degradation intermediates/products such as phthalic anhydride and 2-ethyhexanol were identified by GC-MS analysis. Total organic carbon analysis was also used to ensure the complete mineralization of DEHP. The Microtox^® test was used to assess the toxicities of the parent and degraded compounds. In the second part of this study, DEHP was first removed and concentrated by adsorption onto seaweed biomass under the conditions optimized in the previous study. It was then desorbed from seaweed biomass and degraded by PCO. Results indicate that the treatment for DEHP by integrating biosorption and PCO is feasible.     

Performance of a pilot-scale sewage treatment: an up-flow anaerobic sludge blanket (UASB) and a down-flow hanging sponge (DHS) reactors combined system by sulfur-redox reaction process under low-temperature conditions

Performance of a wastewater treatment system utilizing a sulfur-redox reaction of microbes was investigated using a pilot-scale reactor that was fed with actual sewage. The system consisted of an up-flow anaerobic sludge blanket (UASB) reactor and a down-flow hanging sponge (DHS) reactor with a recirculation line. Consequently, the total COD_Cr (465 ± 147 mg L⁻¹; total BOD of 207 ± 68 mg L⁻¹) at the influent was reduced (70 ± 14 mg L⁻¹; total BOD of 9 ± 2 mg L⁻¹) at the DHS effluent under the conditions of an overall hydraulic retention time of 12 h, a recirculation ratio of 2, and a low-sewage temperature of 7.0 ± 2.8 °C. A microbial analysis revealed that sulfate-reducing bacteria contributed to the degradation of organic matter in the UASB reactor even in low temperatures. The utilized sulfur-redox reaction is applicable for low-strength wastewater treatment under low-temperature conditions.     

Efficient removal of NH4+ accumulated during anaerobic treatment of distillery wastewater from Shochu making

Propionate and NH₄⁺ were accumulated in the effluent during anaerobic treatment of five-fold diluted distillery wastewater from shochu making. Propionate could be removed efficiently during biological denitrification by the addition of NO₃⁻ (4.2 g/l) to the anaerobically treated wastewater. At a hydraulic retention time of more than 2 h, a TOC removal efficiency of 90% could be achieved. The wastewater was then treated aerobically by biological nitrification. With a hydraulic retention time of more than 14 h the efficiency of reduction of NH₄⁺ could be maintained above 97%. In order to reduce the amount of NO₃⁻ addition necessary for the removal of propionate, simultaneous removal of propionate and NH₄⁺ was studied by recirculating the effluent from a nitrification process to a denitrification process using denitrification and nitrification reactors connected in series. At a recirculation ratio of 2, the amount of NO₃⁻ that had to be added was reduced to 0.3 g/l of anaerobically treated wastewater, which corresponds to 6.9% of the theoretical value. Under the same conditions except for the addition of NO₃⁻ at 1.0 g/l, TOC and BOD in the effluent from the nitrification were 23 and 5 mg/l respectively, which are sufficiently low to allow discharge into river water. Moreover, the NO₃⁻ concentration in the effluent decreased with increases in the recirculation ratio.     

Degradation of Phthalate and Di-(2-Ethylhexyl)phthalate by Indigenous and Inoculated Microorganisms in Sludge-Amended Soil

The metabolism of phthalic acid (PA) and di-(2-ethylhexyl)phthalate (DEHP) in sludge-amended agricultural soil was studied with radiotracer techniques. The initial rates of metabolism of PA and DEHP (4.1 nmol/g [dry weight]) were estimated to be 731.8 and 25.6 pmol/g (dry weight) per day, respectively. Indigenous microorganisms assimilated 28 and 17% of the carbon in [¹⁴C]PA and [¹⁴C]DEHP, respectively, into microbial biomass. The rates of DEHP metabolism were much greater in sludge assays without soil than in assays with sludge-amended soil. Mineralization of [¹⁴C]DEHP to ¹⁴CO₂ increased fourfold after inoculation of sludge and soil samples with DEHP-degrading strain SDE 2. The elevated mineralization potential was maintained for more than 27 days. Experiments performed with strain SDE 2 suggested that the bioavailability and mineralization of DEHP decreased substantially in the presence of soil and sludge components. The microorganisms metabolizing PA and DEHP in sludge and sludge-amended soil were characterized by substrate-specific radiolabelling, followed by analysis of ¹⁴C-labelled phospholipid ester-linked fatty acids (¹⁴C-PLFAs). This assay provided a radioactive fingerprint of the organisms actively metabolizing [¹⁴C]PA and [¹⁴C]DEHP. The ¹⁴C-PLFA fingerprints showed that organisms with different PLFA compositions metabolized PA and DEHP in sludge-amended soil. In contrast, microorganisms with comparable ¹⁴C-PLFA fingerprints were found to dominate DEHP metabolism in sludge and sludge-amended soil. Our results suggested that indigenous sludge microorganisms dominated DEHP degradation in sludge-amended soil. Mineralization of DEHP and PA followed complex kinetics that could not be described by simple first-order equations. The initial mineralization activity was described by an exponential function; this was followed by a second phase that was described best by a fractional power function. In the initial phase, the half times for PA and DEHP in sludge-amended soil were 2 and 58 days, respectively. In the late phase of incubation, the apparent half times for PA and DEHP increased to 15 and 147 days, respectively. In the second phase (after more than 28 days), the half time for DEHP was 2.9 times longer in sludge-amended soil assays than in sludge assays without soil. Experiments with radiolabelled DEHP degraders suggested that a significant fraction of the ¹⁴CO₂ produced in long-term degradation assays may have originated from turnover of labelled microbial biomass rather than mineralization of [¹⁴C]PA or [¹⁴C]DEHP. It was estimated that a significant amount of DEHP with poor biodegradability and extractability remains in sludge-amended soil for extended periods of time despite the presence of microorganisms capable of degrading the compound (e.g., more than 40% of the DEHP added is not mineralized after 1 year).     

The effects of hydraulic retention time and sludge retention time on the fate of di-(2-ethylhexyl) phthalate in a laboratory-scale anaerobic-anoxic-aerobic activated sludge system

A laboratory-scale anaerobic-anoxic-aerobic (AAA) activated sludge wastewater treatment system was employed to investigate the effects of hydraulic retention time (HRT) and sludge retention time (SRT) on the removal and fate of di-(2-ethylhexyl) phthalate (DEHP). In the range from 5 to 14h, HRT had no significant effect on DEHP removal. However, longer HRT increased DEHP accumulation in the system and DEHP retention in the waste sludge. When SRT was increased from 15 to 25d, DEHP removal efficiency stayed above 96%. Compared to the removal of only 88% at SRT of 10d, longer SRT enhanced DEHP degradation efficiency. The optimal HRT and SRT for both nutrients (nitrogen and phosphorus) and DEHP removal were 8h and 15d. At these retention times, about 71% of DEHP was degraded by the activated sludge process, 26% was accumulated in the system, 2% was released in the effluent, and 1% remained in the waste sludge. The anaerobic, anoxic and aerobic reactors were responsible for 15%, 19% and 62% of the overall DEHP removal, respectively.     

Application of struvite precipitation as a pretreatment in treating swine wastewater

In this study, the effect of the pretreatment of NH₄-N by struvite precipitation on biological nitrogen removal was investigated in treating swine wastewater. Evaluation was mainly focused on nitrification which occurred in the activated sludge system after struvite precipitation. Laboratory experiments were performed at four different hydraulic retention times (HRT), i.e., 48, 32, 24 and 16 h. Results of the long-term operation of systems showed that the struvite precipitation used as the pretreatment of raw swine wastewater enhanced the nitrification performance in activated sludge system by reducing the applied loading rates of NH₄-N and TCOD in all operating conditions. The reduction of the applied NH₄-N loading rate kept the levels of free ammonia (FA) concentration in biological reactors low and it prevented nitrite accumulation. In addition, the struvite precipitation elicited the biological denitrification reaction and PO₄-P removal by increasing the ratios of carbon-to-nitrogen and carbon-to-phosphorus of wastewater after struvite precipitation. The struvite precipitation also enhanced the biological TCOD removal performance by reducing the toxic effect of FA. Triplicate INT-dehydrogenase tests clearly showed that FA inhibited the degradation of organic matter in activated sludge system. Finally, the struvite precipitation contributed to high TCOD, T-N and PO₄-P removals of 83, 90, and 97% by facilitating biological reaction at a short HRT of 16 h.     

Degradation of environmental endocrine disruptor di-2-ethylhexyl phthalate by a newly discovered bacterium, Microbacterium sp. strain CQ0110Y

In this study di-2-ethylhexyl phthalate (DEHP)-degradation strain CQ0110Y was isolated from activated sludge. According to the biophysical/biochemical characteristics and analysis of 16S rDNA, the strain was identified as Microbacterium sp. The results of this study showed the optimal pH value and optimal temperature which influenced the degradation rate in wastewater: pH 6.5–7.5, 25–35°C. Kinetics of degradation reaction had been performed at different initial concentrations and different time. Analyzed with SPSS10.0 software, the DEHP degradation can be described as the same exponential model when the initial DEHP concentration was lower than 1,350 mg/l. The kinetics equation was ln C = −0.4087t + A, with the degradation half life of DEHP in wastewater (1.59 days). To the best of our knowledge, this is the first reported case of DEHP degradation by Microbacterium sp. strain. Xiang Li and Ji-an Chen contributed equally to this work.     

Biological treatment of high strength wastewater by fed-batch operation

Biological treatment systems for high strength wastewaters are usually operated in continuous mode such as activated sludge systems. When operated at steady-state, continuous systems result in constant effluent standards. However, in the presence of shock loadings and/or toxic compounds in feed wastewater, system performance drops quite significantly as a result of partial loss of microbial activity. In fed-batch operation, wastewater is fed to the aeration tank with a flow rate determined by effluent standards. In this type of operation, wastewater can be fed to biological oxidation unit intermittently or continuously with a low flow rate without any effluent removal. Feed flow rate is adjusted by measuring COD concentration in the effluent. As a result of intermittent addition of wastewater high COD concentrations and toxic compounds are diluted in large volume of aeration tank and inhibition effects of those compounds are reduced. As a result, biological oxidation of these compounds take place at a much higher rate. In order to show the aforementioned advantage of fed-batch operation, a high strength synthetic wastewater consisting of diluted molasses, urea, KH₂PO₄ and MgSO₄ was treated in an biological aeration tank by fed-batch operation. Organisms used were an active and dominant culture of Zooglea ramigera commonly encountered in activated sludge operations. COD removal kinetics was found to be first order and the rate constant was determined.     

Monitoring of sequencing batch reactor for nitrogen and phosphorus removal using neural networks

The information of nutrient dynamics is essential for the precise control of effluent quality discharged from biological wastewater treatment processes. However, these variables can usually be determined with a significant time delay. Although the final effluent quality can be analyzed after this delay, it is often too late to make proper adjustments. In this paper, a neural network approach, a software sensor, was proposed for the real-time estimation of nutrient concentrations and overcoming the problem of delayed measurements. In order to improve the neural network performance, a split network structure applied separately for anaerobic and aerobic conditions was employed with dynamic modeling methods such as auto-regressive with exogenous inputs. The proposed methodology was applied to a bench-scale sequencing batch reactor (SBR) for biological nutrient removal. The extrapolation problem of neural networks was possible to be partially overcome with the aid of multiway principal component analysis because of its ability of detecting of abnormal situations which could generate extrapolation. Real-time estimation of PO₄³⁻, NO₃⁻ and NH₄⁺ concentrations based on neural network was successfully carried out with the simple on-line information of the SBR system only.     

Performance evaluation and phylogenic analysis of a full-scale subsurface cobble-bed biofilm system

The purpose of this study is to evaluate the efficiency of municipal wastewater treatment by a subsurface cobble-bed biofilm system (SCBS) in Taipei, Taiwan. In contrast to traditional wastewater treatment facilities, SCBS uses cobbles as the contact media in the biofilm treatment unit. In this study, the SCBS consists of a series of underground treatment units, including a sedimentation tank, a grit chamber, two bar screens, a pumping station, a distribution tank, a collection tank and an effluent tank. At the flowrate of 4000 m³/day, the average influent concentrations for biochemical oxygen demand, suspended solid, ammonium nitrogen, and total phosphorus were 66.99 mg/L, 26.14 mg/L, 17.33 mg/L, and 1.96 mg/L, respectively. After 39 months of operation, the measured influent and effluent results show that the treatment efficiencies obtained from the SCBS for biochemical oxygen demand, suspended solid, ammonium nitrogen, and total phosphorus are 91.3%, 84.0%, 84.0%, and 26.0%, respectively. The result of a first-order kinetic analysis shows that the NH₃-N degradation constant is greater than the BOD degradation constant in this cobble-bed biofilm unit. Probability analysis revealed that the SCBS may be an attractive alternative from the perspectives of treatment efficiency for municipal wastewater treatment. Klebsiella spp. were found to be the predominant species in the biofilm system in the SCBS.     

污水地下渗滤系统脱氮效果及动力学过程

建立了模拟污水地下渗滤过程的中试系统,重点考察了水力负荷对系统脱氮效率的影响情况,建立了描述地下渗滤系统微生物脱氮过程的动力学模型.结果表明:地下渗滤系统脱氮效果好,抗水力负荷冲击能力强,处理最佳水力负荷0.125m3· m-2· d-1,出水中氮浓度低于《城市污水再生利用——景观环境用水水质》标准( GB/T 18921-2002).地下渗滤系统硝化过程符合一级动力学模型NE=Noe-0.4812t,温度是影响硝化速率的主要因素,两者的关系是KT=0.2218×1.035(T-20);出水硝态氮浓度与水力停留时间之间呈负指数关系,可描述为C=16.3475e-0.2548t,碳源是引起反硝化速率变化的主要因子.在基质层垂直深度65 cm处二次补加生活污水,反硝化速率常数由0.0355提高到0.0488.强调地下渗滤系统的污水净化功能而忽视其生态服务功能,是系统运行中普遍存在的认识误区,过高的水力负荷不利于硝化-反硝化反应的顺利进行.地下渗滤系统运行应采取适宜的水力负荷方式,促进硝化-反硝化作用.     

Modeling speciation effects on biodegradation in mixed metal/chelate systems

A new model, CCBATCH, comprehensively couples microbially catalyzed reactions to aqueous geochemistry. The effect of aqueous speciation on biodegradation reactions and the effect of biological reactions on the concentration of chemical species (e.g. H₂CO₃, NH ₄ ⁺ , O₂) are explicitly included in CCBATCH, allowing systematic investigation of kinetically controlled biological reactions. Bulk-phase chemical speciation reactions including acid/base and complexation are modeled as thermodynamically controlled, while biological reactions are modeled as kinetically controlled. A dual-Monod kinetic formulation for biological degradation reactions is coupled with stoichiometry for the degradation reaction to predict the rate of change of all biological and chemical species affected by the biological reactions. The capability of CCBATCH to capture pH and speciation effects on biological reactions is demonstrated by a series of modeling examples for the citrate/Fe(III) system. pH controls the concentration of potentially biologically available forms of citrate. When the percentage of the degradable substrate is low due to complexation or acid/base speciation, degradation rates may be slow despite high concentrations of substrate Complexation reactions that sequester substratein non-degradable forms may prevent degradation or stopdegradation reactions prior to complete substrate utilization. The capability of CCBATCH to couple aqueous speciation changes to biodegradation reaction kinetics and stoichiometry allows prediction of these key behaviors in mixed metal/chelate systems.     

Performance of an ecological treatment system at three strengths of dairy wastewater loading

Ecological treatment systems, which rely on renewable resources, have successfully treated municipal and industrial effluents with reduced costs compared to conventional methods, but their capacity to treat dairy wastewater is unknown. In order for ecological treatment systems to be practical for agriculture they must be able to treat a significant portion of a dairy's daily wastewater production. In this study, the impact of three strengths of dairy wastewater on effluent water quality was assessed. Three ratios of wastewater and city water—(1) one part wastewater:three parts city water, (2) one part wastewater:one part city water, and (3) two parts wastewater:one part city water—were each pumped into an ecological treatment system. Influent and effluent water samples were analyzed for PO₄-P, TP, TN, NH₄-N, NO₃-N, total suspended solids (TSS), and carbonaceous biochemical oxygen demand (CBOD₅). Influent dairy wastewater volumetric loading rates were much greater than those of municipal wastewater. Regardless of influent wastewater strength, concentrations of all measured variables were significantly reduced between the influent and effluent of the ecological treatment system. At the lowest wastewater strength, PO₄-P was reduced 39%, TN 83%, and NH₄-N 89%, while at the highest wastewater strength, PO₄-P was reduced 41%, TN 79%, and NH₄-N 70%. Increased wastewater strength required greater aerobic treatment volume to reduce concentrations of NH₄-N and CBOD₅.     

Degradation of di-ethylhexyl phthalate (DEHP) in bioslurry phase reactor and identification of metabolites by HPLC and MS

Di-ethylhexyl phthalate (DEHP) belongs to the class of phthalate esters and is used as an additive in many products including plastics, paints and inks or as a solvent in industrial formulations. However, it is used mostly for its plasticizing ability in polyvinyl chloride (PVC) products, in which it is often added in concentrations exceeding 40% by mass. DEHP is one of the more recalcitrant phthalate esters, which has xeno-estrogenic, carcinogenic and mutagenic effects. Five different bioslurry reactors were operated under different conditions to study the degradation of DEHP (1 mg g⁻¹ soil) in soil. The process performance was assessed by monitoring DEHP concentration periodically using high performance liquid chromatography (HPLC). The ongoing biological process was monitored by analyzing pH, oxidation–reduction potential (ORP), dissolved oxygen (DO), oxygen uptake rate (OUR) and colony forming units (CFU) for every 24 h. More than 90% degradation was observed within 12 days of the cycle period in the augmented reactors. Metabolites formed during the degradation of DEHP in the slurry phase reactor were identified and the pathway was also established. The degradation process was found to follow zero-order kinetic model.     

Coupling of anodic biooxidation and cathodic bioelectro-Fenton for enhanced swine wastewater treatment

A novel bioelectrochemical reactor with anodic biooxidation coupled to cathodic bioelectro-Fenton was developed for the enhanced treatment of highly concentrated organic wastewater. Using swine wastewater as a model, the anode-cathode coupled system was demonstrated to be both efficient and energy-saving. Without any external energy supply to the system, BOD₅, COD, NH₃-N and TOC in the wastewater could be greatly reduced at both 1.1 g COD L⁻¹ d⁻¹ and 4.6 g COD L⁻¹ d⁻¹ of OLR, with the overall removal rates ranging from 62.2% to 95.7%. Simultaneously, electricity was generated at around 3-8 W m⁻³ of maximum output power density. Based on electron balance calculation, 60-65% of all the electrons produced from anodic biooxidation were consumed in the cathodic bioelectro-Fenton process. This coupled system has a potential for enhanced treatment of high strength wastewater and provides a new way for efficient utilization of the electron generated from biooxidation of organic matters.     

Coupling microbial fuel cells with a membrane photobioreactor for wastewater treatment and bioenergy production

Microbial fuel cells (MFCs) and membrane photobioreactors are two emerging technologies for simultaneous wastewater treatment and bioenergy production. In this study, those two technologies were coupled to form an integrated treatment system, whose performance was examined under different operating conditions. The coupled system could achieve 92–97 % removal of soluble chemical oxygen demand (SCOD) and nearly 100 % removal of ammonia. Extending the hydraulic retention time (HRT) of the membrane photobioreactor to 3.0 days improved the production of algal biomass from 44.4 ± 23.8 to 133.7 ± 12.9 mg L^?1 (based on the volume of the treated water). When the MFCs were operated in a loop mode, their effluent (which was the influent to the algal reactor) contained nitrate and had a high pH, leading to the decreased algal production in the membrane photobioreactor. Energy analysis showed that the energy consumption was mainly due to the recirculation of the anolyte and the catholyte in the MFCs and that decreasing the recirculation rates could significantly reduce energy consumption. The energy production was dominated by indirect electricity generation from algal biomass. The highest energy production of 0.205 kWh m^?3 was obtained with the highest algal biomass production, resulting in a theoretically positive energy balance of 0.033 kWh m^?3. Those results have demonstrated that the coupled system could be an alternative approach for energy-efficient wastewater treatment and using wastewater effluent for algal production.     

Effect of internal recycle on the nitrogen removal efficiency of an anaerobic/anoxic/oxic (A2/O) wastewater treatment plant (WWTP)

Internal recycle ratio is an important parameter in anaerobic/anoxic/oxic (A²/O) wastewater treatment plant (WWTP) operation. An increase in this ratio decreases nitrate and nitrite concentration in the effluent and hence improves the nitrogen removal efficiency, even though the economical cost increases simultaneously. Determining the most favourable recycle ratio taking into account both considerations is an important item in A²/O WWTP operational optimisation. In this work, the effect of recycle ratio on nitrogen removal when using different influent nitrogen loads was tested in a pilot A²/O WWTP. Experimental results obtained show how increasing the internal recycle ratio from 0 to 5 produced a 12% increase in nitrogen removal. This increase was achieved by improving N–NO_x removal by 9% with an increase in N–NH₄⁺ removal of 3%.     

Remediation of Nitrobenzene Contaminated Soil by Combining Surfactant Enhanced Soil Washing and Effluent Oxidation with Persulfate

The combination of surfactant enhanced soil washing and degradation of nitrobenzene (NB) in effluent with persulfate was investigated to remediate NB contaminated soil. Aqueous solution of sodium dodecylbenzenesulfonate (SDBS, 24.0 mmol L^-1) was used at a given mass ratio of solution to soil (20:1) to extract NB contaminated soil (47.3 mg kg^-1), resulting in NB desorption removal efficient of 76.8%. The washing effluent was treated in Fe²⁺/persulfate and Fe²⁺/H₂O₂ systems successively. The degradation removal of NB was 97.9%, being much higher than that of SDBS (51.6%) with addition of 40.0 mmol L^-1 Fe²⁺ and 40.0 mmol L^-1 persulfate after 15 min reaction. The preferential degradation was related to the lone pair electron of generated SO₄•⁻, which preferably removes electrons from aromatic parts of NB over long alkyl chains of SDBS through hydrogen abstraction reactions. No preferential degradation was observed in •OH based oxidation because of its hydrogen abstraction or addition mechanism. The sustained SDBS could be reused for washing the contaminated soil. The combination of the effective surfactant-enhanced washing and the preferential degradation of NB with Fe²⁺/persulfate provide a useful option to remediate NB contaminated soil.