Process control factors for continuous microbial perchlorate reduction in the presence of zero-valent iron

Process control parameters influencing microbial perchlorate reduction via a flow-through zero-valent iron （ZVI） column reactor were investigated in order to optimize perchlorate removal from water. Mixed perchlorate reducers were obtained from a wastewater treatment plant and inoculated into the reactor without further acclimation. Examined parameters included hydraulic residence time （HRT）, pH, nutrients requirement, and perchlorate reduction kinetics. The minimum HRT for the system was concluded to be 8 hr. The removal efficiency of 10 mg. L-1 influent perchlorate concentration was reduced by 20%-80% without control to the neutral pH （HRT = 8 hr）. Therefore pH was determined to be an important parameter for microbial perchlorate reduction. Furthermore, a viable alternative to pH buffer was discussed. The microbial perchlorate reduction followed the first order kinetics, with a rate constant （K） of 0.761 hr-1. The results from this study will contribute to the implementation of a safe, cost effective, and efficient system for perchlorate reduction to below regulated levels.     

Reduction of hexavalent chromium with scrap iron in a fixed bed reactor

The reduction of hexavalent chromium by scrap iron was investigated in continuous long-term fixed bed system. The effects of pH, empty bed contact time (EBCT), and initial Cr(VI) concentration on Cr(VI) reduction were studied. The results showed that the pH, EBCT, and initial Cr(VI) concentration significantly affected the reduction capacity of scrap iron. The reduction capacity of scrap iron were 4.56, 1.51, and 0.57 mg Cr(VI)·g^-1 Fe⁰ at pH 3, 5, and 7 (initial Cr(VI) concentration 4 mg·L^-1, EBCT 2 min, and temperature 25°C), 0.51, 1.51, and 2.85 mg Cr(VI)·g^-1 Fe⁰ at EBCTs of 0.5, 2.0, and 6.0 min (initial Cr(VI) concentration 4 mg·L^-1, pH 5, and temperature 25°C), and 2.99, 1.51, and 1.01 mg Cr(VI)·g^-1 Fe⁰ at influent concentrations of 1, 4, and 8 mg·L^-1 (EBCT 2 min, pH 5, and temperature 25°C), respectively. Fe(total) concentration in the column effluent continuously decreased in time, due to a decrease in time of the iron corrosion rate. The fixed bed reactor can be readily used for the treatment of drinking water containing low amounts of Cr(VI) ions, although the hardness and humic acid in water may shorten the lifetime of the reactor, the reduction capacity of scrap iron still achieved 1.98 mg Cr⁶⁺·g^-1 Fe. Scanning electron microscope equipped with energy dispersion spectrometer and X-ray diffraction were conducted to examine the surface species of the scrap iron before and after its use. In addition to iron oxides and hydroxide species, iron-chromium complex was also observed on the reacted scrap iron.     

Performance of an ANAMMOX reactor treating wastewater generated by antibiotic and starch production processes

A pilot-scale anaerobic ammonia oxidation (ANAMMOX) reactor was used to treat mixed wastewater resulting from a chlortetracycline and starch production process. The results, collected over the course of 272 days, show that the ratio of influent ammonium to nitrite, pH, and temperature can all affect the efficiency of nitrogen removal. The ratio of influent ammonium to nitrite was maintained at about 1:1 at a concentration below 200 mg·L^-1 for both influent ammonium and nitrite. The total nitrogen (TN) loading rate was 0.15–0.30 kgN·m^-3·d^-1, pH remained at 7.8–8.5, and temperature was recorded at 33±1°C. The rate of removal of ammonia, nitrite, and TN were over 90%, 90%, and 80%, and the effluent ammonium, nitrite and TN concentrations were below 50, 30, and 100 mg·L^-1.     

Biological removal of selenate in saline wastewater by activated sludge under alternating anoxic/oxic conditions

Removal of selenate in saline wastewater by activated sludge was examined. Sequencing batch reactor was operated under alternating anoxic/oxic conditions. Above 97% removal of soluble selenium (Se) was achieved continuously. Major Se removal mechanism varied depending on the length of aeration period. Various Se-reducing bacteria likely contributed to coordinately to Se removal. Selenium (Se)-containing industrial wastewater is often coupled with notable salinity. However, limited studies have examined biological treatment of Se-containing wastewater under high salinity conditions. In this study, a sequencing batch reactor (SBR) inoculated with activated sludge was applied to treat selenate in synthetic saline wastewater (3% w/v NaCl) supplemented with lactate as the carbon source. Start-up of the SBR was performed with addition of 1–5 mM of selenate under oxygen-limiting conditions, which succeeded in removing more than 99% of the soluble Se. Then, the treatment of 1 mM Se with cycle duration of 3 days was carried out under alternating anoxic/oxic conditions by adding aeration period after oxygen-limiting period. Although the SBR maintained soluble Se removal of above 97%, considerable amount of solid Se remained in the effluent as suspended solids and total Se removal fluctuated between about 40 and 80%. Surprisingly, the mass balance calculation found a considerable decrease of Se accumulated in the SBR when the aeration period was prolonged to 7 h, indicating very efficient Se biovolatilization. Furthermore, microbial community analysis suggested that various Se-reducing bacteria coordinately contributed to the removal of Se in the SBR and main contributors varied depending on the operational conditions. This study will offer implications for practical biological treatment of selenium in saline wastewater.     

Anaerobic treatment of wastewater containing methanol in upflow anaerobic sludge bed (UASB) reactor

The direct conversion of methanol into methane is the main process in anaerobic treatment of methanol containing wastewater. However, acetic acid can also be produced from methanol theoretically, which may probably result in an abrupt pH drop and deteriorate the anaerobic process. Therefore, it is interesting to know what would really happen in an anaerobic reactor treating methanol wastewater. In this study, an up-flow anaerobic sludge bed (UASB) reactor treating methanol wastewater was operated. The chemical oxygen demand (COD), acetic acid and pH of the effluent were monitored at different loadings and influent alkalinity. The results showed that the anaerobic reactor could be operated steadily at as low as 119 mg/L of influent alkalinity and high organic loading rate with no obvious pH drops. Volatile fatty acids accumulation was not observed even at strong shock loadings. The microorganisms in the sludge at the end of the test became homogeneous in morphology, which were mainly spherical or spheroidal in shape.     

Optimization of phosphorus removal in uniFed SBR system for domestic wastewater treatment

The characteristic of phosphorus removal and appropriate change of the traditional operation modes were investigated in UniFed sequencing batch reactor (SBR) laboratory-scale apparatus (40 L), treating actual domestic wastewater with low ratios of C/N (2.57) and C/P (30.18), providing theoretical basis for actual application of wastewater treatment plant. UniFed SBR system with its unique operation mode had the distinct superiority of phosphorus removal. On this occasion, the effect of volumetric exchange ratio (VER) and the method of influent introduction for phosphorus removal were studied. When the carbon source became the limiting factor to phosphorus release, the higher the VER, the lower the phosphorus concentration in the effluent. Three different influent patterns, including one-time filling, four-time filling, and continuous filling with the same quantity of wastewater could increase the release rate of anaerobic phosphorus from 0.082 to 0.143 mg·P·(L·min)^-1. Appropriate change of the traditional operation modes could optimize the efficiency of phosphorus removal. When the feed/ decant time was extended from 2 h to 4 h, the phosphorous removal efficiency increased from 59.93% to 88.45% without any external carbon source. In the mode of alternation of anoxic-aerobic (A/O) condition, phosphorous removal efficiency increased from 55.07% to 72.27% clearly. The carbon source in the influent can be used adequately, and denitrifying phosphorus removal was carried out in anoxic stage 2 (A2). This mode was optimal for the treatment of actual domestic wastewater with low C/N and C/P ratios.     

流化床三维电极电催化氧化深度处理焦化废水

研究了以焦粒为粒子电极的流化床三维电极反应器对二级生化处理后的焦化废水进行深度处理。结果表明：采用以焦粒为粒子电极的流化床三维电极反应器能有效降解废水中的有机物,COD去除率依赖于粒子投加量、电流密度、电导率、pH值、曝气量等操作参数的影响。在电导率（以S计）为7.1 m.cm-1,曝气量为160 L.h-1,电流密度（以A计）为48 m.cm-2,pH值为5.0,投加量30 g.L-1时,电解30 min,COD的去除率超过60%,表明流化床三维电极反应器在焦化废水深度处理中有很好工程应用前景。     

A/O-MBR处理某经济区市政污水的效能

采用A/O-MBR法处理某经济区市政污水,对其进、出水的水质进行连续监测,考察系统稳定性和处理效果。结果表明,在水力停留时间12小时,污泥龄30天,回流比75%,好氧段DO浓度1.3～8.5 mg/L的条件下,系统对COD、氨氮、总氮、总磷的平均去除率分别为92.04%、93.66%、78.04%、91.06%。反硝化...     

Fermentative hydrogen production from beet sugar factory wastewater treatment in a continuous stirred tank reactor using anaerobic mixed consortia

A low pH, ethanol-type fermentation process was evaluated for wastewater treatment and bio-hydrogen production from acidic beet sugar factory wastewater in a continuous stirred tank reactor (CSTR) with an effective volume of 9.6 L by anaerobic mixed cultures in this present study. After inoculating with aerobic activated sludge and operating at organic loading rate (OLR) of 12 kgCOD?m^-3·d^-1, HRT of 8h, and temperature of 35°C for 28 days, the CSTR achieved stable ethanol-type fermentation. When OLR was further increased to 18 kgCOD?m^-3·d^-1 on the 53rd day, ethanol-type fermentation dominant microflora was enhanced. The liquid fermentation products, including volatile fatty acids (VFAs) and ethanol, stabilized at 1493 mg·L^-1 in the bioreactor. Effluent pH, oxidation-reduction potential (ORP), and alkalinity ranged at 4.1–4.5, -250–(-290) mV, and 230–260 mgCaCO₃?L^-1. The specific hydrogen production rate of anaerobic activated sludge was 0.1 L?gMLVSS^-1·d^-1 and the COD removal efficiency was 45%. The experimental results showed that the CSTR system had good operation stability and microbial activity, which led to high substrate conversion rate and hydrogen production ability.     

Fe-C-H_2O_2协同催化氧化处理印染废水

用Fe-C-H2O2协同催化氧化体系对印染工业废水的降解脱色处理进行了研究。对影响印染废水降解的几种因素如铁屑/碳粒质量比、双氧水的质量分数、废水pH等进行考察。试验结果表明,对于色度为650度和ρ（COD）为468mg·L-1的印染废水,在废水pH=4.8的情况下,当铁屑/碳粒质量比为25∶1、H2O2用量为150mg·L-1、催化反应30min时,印染废水的脱色率达98%以上,CODCr去除率可达78%。与Fe-C微电解法相比,Fe-C-H2O2协同催化氧化方法对印染废水的脱色能力和去除COD,表现出了更好的处理效果。     

不同进水有机物浓度下移动床生物膜反应器(SBMBBR)脱氮除磷特性

考察了不同进水有机物浓度下厌氧/好氧序批式移动床生物膜反应器（SBMBBR）污染物去除特性,实验结果表明,SBMBBR能够实现低碳源污水中氮和磷的同步去除,在进水TN和TP浓度分别为116.7 mg.L-1和11.5 mg.L-1、COD浓度为456 mg.L-1的条件下,TN和TP去除率分别达到94.3%和92.2%以上.反应器除磷是基于常规生物除磷和反硝化除磷过程实现的,脱氮主要是基于好氧段发生的同时硝化反硝化（SND）作用而完成.由于生物膜内部存在的DO扩散梯度,在好氧阶段混合液DO浓度不断提高的条件下反应器内具有良好SND反应的发生.进水COD浓度由149 mg.L-1提高至456 mg.L-1的过程中,反应器硝化效果不变,反硝化和除磷效果改善.反应器在好氧阶段pH值基本维持在7.0—7.1之间,为各类菌群的生长创造了条件.碱度变化较pH值更能反映硝化和反硝化反应发生的程度.反应器中微生物相丰富,生物膜以丝状菌为骨架,其上附着大量的球状菌和杆状菌,而悬浮活性污泥中丝状菌较少,形成了由细菌、真菌到原生动物和后生动物的复杂的生态体系,为系统取得稳定的污水处理效果提供了有效的保证.     

Simultaneous denitrifying phosphorus accumulation in a sequencing batch reactor

In order to achieve simultaneous nitrogen and phosphorus removal in the biological treatment process, denitrifying phosphorus accumulation (DNPA) and its affecting factors were studied in a sequencing batch reactor (SBR) with synthetic wastewater. The results showed that when acetate was used as the sole carbon resource in the influent, the sludge acclimatized under anaerobic/aerobic operation had good phosphorus removal ability. Denitrifying phosphorus accumulation was observed soon when fed with nitrate instead of aeration following the anaerobic stage, which is a vital premise to DNPA. If DNPA sludge is fed with nitrate prior to the anaerobic stage, the DNPA would weaken or even disappear. At the high concentration of nitrate fed in the anoxic stage, the longer anoxic time needed, the better the DNPA was. Induced DNPA did not disappear even though an aerobic stage followed the anoxic stage, but the shorter the aerobic stage lasted, the higher the proportions of phosphorus removal via DNPA to total removal.     

Influence of aeration intensity on the performance of A/O-type sequencing batch MBR system treating azo dye wastewater

Among the numerous parameters affecting the membrane bioreactor (MBR) performance, the aeration intensity is one of the most important factors. In the present investigation, an anoxic/aerobic-type (A/O-type) sequencing batch MBR system, added anoxic process as a pretreatment to improve the biodegradability of azo dye wastewater, was investigated under different aeration intensities and the impact of the aeration intensity on effluent quantity, sludge properties, extracellular polymeric substances (EPS) amount generated as well as the change of permeation flux were examined. Neither lower nor higher aeration intensities could improve A/O-type sequencing batch MBR performances. The results showed 0.15 m³·h^-1 aeration intensity was promising for treatment of azo dye wastewater under the conditions examined. Under this aeration intensity, chemical oxygen demand (COD), ammonium nitrogen and color removal as well as membrane flux amounted to 97.8%, 96.5%, 98.7% and 6.21 L·m^-2·h^-1, respectively. The effluent quality, with 25.0 mg·L^-1COD, 0.84 mg·L^-1 ammonium nitrogen and 8 chroma, could directly meet the reuse standard in China. In the meantime, the sludge relative hydrophobicity, the bound EPS, soluble EPS and EPS amounts contained in the membrane fouling layer were 70.3%, 52.0 mg·g^-1VSS, 38.8 mg·g^-1VSS and 90.8 mg·g^-1VSS, respectively, which showed close relationships to both pollutant removals and membrane flux.     

Partial anammox achieved in full scale biofilm process for typical domestic wastewater treatment

• A full scale biofilm process was developed for typical domestic wastewater treatment. • The HRT was 8 h and secondary sedimentation tank was omitted. • Candidatus Brocadia were enriched in the HBR with an abundance of 2.89%. • Anammox enabled a stable ammonium removal of ~15% in the anoxic zone. The slow initiation of anammox for treating typical domestic wastewater and the relatively high footprint of wastewater treatment infrastructures are major concerns for practical wastewater treatment systems. Herein, a 300 m³/d hybrid biofilm reactor (HBR) process was developed and operated with a short hydraulic retention time (HRT) of 8 h. The analysis of the bacterial community demonstrated that anammox were enriched in the anoxic zone of the HBR process. The percentage abundance of Candidatus Brocadia in the total bacterial community of the anoxic zone increased from 0 at Day 1 to 0.33% at Day 130 and then to 2.89% at Day 213. Based upon the activity of anammox bacteria, the removal of ammonia nitrogen (NH₄⁺-N) in the anoxic zone was approximately 15%. This showed that the nitrogen transformation pathway was enhanced in the HBR system through partial anammox process in the anoxic zone. The final effluent contained 12 mg/L chemical oxygen demand (COD), 0.662 mg/L NH₄⁺-N, 7.2 mg/L total nitrogen (TN), and 6 mg/L SS, indicating the effectiveness of the HBR process for treating real domestic wastewater.     

Feedforward control for nitrogen removal in a pilot-scale anaerobic-anoxic-oxic plant for municipal wastewater treatment

To improve the efficiency of nitrogen removal with lower energy consumption, the study of feedforward control was carried out on a pilot-scale anaerobic-anoxic-oxic (AAO) plant for the treatment of municipal wastewater. The effluent qualities of the pilot plant under different control strategies were investigated. The results indicated that the change of external recycle was not a suitable approach to regulate the sludge concentration of plug-flow reactors; adjusting the aeration valve and dissolved oxygen set-point according to ammonia load could overcome the impact of influent fluctuation; and the denitrification potential could be estimated based on the transit time of anoxic zone and the relative content of carbon resource entering the anoxic zone. Simple feedforward control strategies for aeration and internal recycle were subsequently proposed and validated. The nitrogen removal was successfully improved in the pilot plant. The effluent total nitrogen had decreased by 29.9% and was steadily controlled below 15 mg·L^-1. Furthermore, approximately 38% of the energy for aeration had been saved.     

Control of sludge settleability and nitrogen removal under low dissolved oxygen condition

Low dissolved oxygen (DO) is an energy-saving condition in activated sludge process. To investigate the possible application of limited filamentous bulking (LFB) in sequencing batch reactor (SBR), two lab-scale SBRs were used to treat synthetic domestic wastewater and real municipal wastewater, respectively. The results showed that prolonging low DO aeration duration and setting pre-anoxic (anaerobic) phase were effective strategies to induce and inhibit filamentous sludge bulking, respectively. According to the sludge settleability, LFB could be maintained steadily by adjusting operation patterns. Filamentous bacteria content and sludge volume index (SVI) were likely correlated. SVI fluctuated dramatically within a few cycles when around 200 mL·g^-1, where altering operation pattern could change sludge settleability in spite of the unstable status of activated sludge system. Energy consumption by aeration reduced under low DO LFB condition, whereas the nitrification performance deteriorated. However, short-cut nitrification and simultaneous nitrification denitrification (SND) were prone to take place under such conditions. When the cycle time kept constant, the anoxic (anaerobic) to aerobic time ratio was determining factor to the SND efficiency. Similarity keeping aerobic time as constant, the variation trends of SND efficiency and specific SND rate were uniform. SBR is a promising reactor to apply the LFB process in practice.     

硫酸盐还原菌对酸性废水中重金属的生物沉淀作用研究

在小型连续搅拌槽式反应器（CSTR）中,研究了持续低pH条件下,硫酸盐还原菌的生物沉淀作用对人工配制酸性重金属废水的处理效果。试验设置反应器进水pH值依次为4-3,3．5和2．6三个处理,进水中Cu^2＋、Zn^2＋和Cr^3＋含量分别为65、36和10mg·L^-1,SO4^2-含量约为6200mg·L^-1,接种物为经耐酸驯化的混合硫酸盐还原菌,试验时控制水力停留时间为36h,通过定期测定反应器出水pH、氧化还原电位（ORP）、碱度、SO4^2、S^2-以及重金属含量变化等指标来考察废水生物沉淀的处理效果。研究结果表明：对于进水pH值为2．6～4.3的酸性重金属废水,硫酸盐还原菌的生物沉淀作用均有较好的处理效果。处理后,反应器出水pH值大幅升至6．5～8．0,碱度由起始的300～2000mg·L^-1增至7500-4600mg·L^-1,废水中S041-还原率达72％～80％,Cu^2＋和Zn^2＋的去除（沉淀）率达99．9％,Cr^3＋去除率达99．1％。此外,随着进水pH值由413降至2．6,反应器出水pH和碱度均呈现逐步下降的趋势,而S04}的生物还原和重金属的去除效果变化不大。从反应器运行稳定性考虑,控制酸性重金属废水的进水pH值为3．5较适宜今后的实际应用。     

Feasibility assessment of up-flow anaerobic sludge blanket treatment of sulfamethoxazole pharmaceutical wastewater

The UASB system successfully treated sulfamethoxazole pharmaceutical wastewater. High concentration sulfate of this wastewater was the main refractory factor. UASB recovery performance after a few days of inflow arrest was studied. The optimal UASB operating conditions for practical application were determined. Treatment of sulfamethoxazole pharmaceutical wastewater is a big challenge. In this study, a series of anaerobic evaluation tests on pharmaceutical wastewater from different operating units was conducted to evaluate the feasibility of using anaerobic digestion, and the results indicated that the key refractory factor for anaerobic treatment of this wastewater was the high sulfate concentration. A laboratory-scale up-flow anaerobic sludge blanket (UASB) reactor was operated for 195 days to investigate the effects of the influent chemical oxygen demand (COD), organic loading rate (OLR), and COD/SO₄^2? ratio on the biodegradation of sulfamethoxazole in pharmaceutical wastewater and the process performance. The electron flow indicated that methanogenesis was still the dominant reaction although sulfidogenesis was enhanced with a stepwise decrease in the influent COD/SO₄^2? ratio. For the treated sulfamethoxazole pharmaceutical wastewater, a COD of 4983 mg/L (diluted by 50%), OLR of 2.5 kg COD/(m³·d), and COD/SO₄^2? ratio of more than 5 were suitable for practical applications. The recovery performance indicated that the system could resume operation quickly even if production was halted for a few days.     

Preparation of nZVI embedded modified mesoporous carbon for catalytic persulfate to degradation of reactive black 5

• The MCNZVI is prepared as an interesting material for PS activation. • Graphitized carbon shells facilitate electron transfer from Fe⁰. • The MCNZVI exhibits excellent performance to degrade RB5 by ¹O₂. • The MCNZVI has high stability and reusability in the oxidation system. High-efficiency and cost-effective catalysts with available strategies for persulfate (PS) activation are critical for the complete mineralization of organic contaminants in the environmental remediation and protection fields. A nanoscale zero-valent iron-embedded modified mesoporous carbon (MCNZVI) with a core-shell structure is synthesized using the hydrothermal synthesis method and high-temperature pyrolysis. The results showed that nZVI could be impregnated within mesoporous carbon frameworks with a comparatively high graphitization degree, rich nitrogen doping content, and a large surface area and pore volume. This material was used as a persulfate activator for the oxidation removal of Reactive Black 5 (RB5). The effects of the material dosage, PS concentration, pH, and some inorganic anions (i.e., Cl⁻, SO₄²⁻) on RB5 degradation were then investigated. The highest degradation efficiency (97.3%) of RB5 was achieved via PS (20 mmol/L) activation by the MCNZVI (0.5 g/L). The pseudo-first-order kinetics (k = 2.11 × 10⁻² min⁻¹) in the MCNZVI/PS (0.5 g/L, 20 mmol/L) was greater than 100 times than that in the MCNZVI and PS. The reactive oxygen species (ROS), including ¹O₂, SO₄^·−, HO^·, and ·O₂⁻, were generated by PS activation with the MCNZVI. Singlet oxygen was demonstrated to be the primary ROS responsible for the RB5 degradation. The MCNZVI could be reused and regenerated for recycling. This work provides new insights into PS activation to remove organic contamination.     

球磨零价镁/石墨(ZVMg/C)降解水中三氯乙烯

利用机械球磨法制备了零价镁/石墨(ZVMg/C)材料,并将其用于水溶液中三氯乙烯(TCE)的降解.研究通过SEM、BET和XRD等分析手段解析了ZVMg/C的表面形态结构和成分组成;采用正交实验方法优化了ZVMg/C的制备参数,比较了石墨含量对材料性能的影响;并考察了ZVMg/C投加量、溶液初始pH和地下水中常见阴(C...