常用城市污水再生处理工艺净化效果比较分析

以城市污水回用为目的,对常规混凝-沉淀-过滤工艺、臭氧生物活性炭和直接超滤等深度处理技术处理城市污水处理厂二级出水的效果进行了试验研究,对各种工艺的去除效果进行了评价。     

Heavy metal removal from synthetic wastewaters in an anaerobic bioreactor using stillage from ethanol distilleries as a carbon source

This work was conducted to investigate the possibility of using stillage from ethanol distilleries as substrate for sulfate reducing bacteria (SRB) growth and to evaluate the removal efficiency of heavy metals present in wastewaters containing sulfates. The experiments were carried out in a continuous bench-scale Upflow Anaerobic Sludge Blanket reactor (13 l) operated with a hydraulic retention time of 18 h. The bioreactor was inoculated with 7 l of anaerobic sludge. Afterwards, an enrichment procedure to increase SRB numbers was started. After this, cadmium and zinc were added to the synthetic wastewater, and their removal as metal sulfide was evaluated. The synthetic wastewater used represented the drainage from a dam of a metallurgical industry to which a carbon source (stillage) was added. The results showed that high percentages of removal (>99%) of Cd and Zn were attained in the bioreactor, and that the removal as sulfide precipitates was not the only form of metal removal occurring in the bioreactor environment.     

基于电化学反应原理的含铬工业废水处理技术

对于含重金属离子的工业废水处理来说,污染物的去除和回收往往是最重要的指标。以电化学反应原理为基础的污水处理新技术以其在金属回收利用方面的独特优越性引起了研究人员的很大兴趣。在分析中,从铬(VI)回收利用的角度出发,介绍了电化学技术处理含铬工业废水的基本电极反应,对外加电场存在与否的两种情况下的除铬(VI)机理进行了分析,介绍了各自的典型处理流程,并讨论了各自的主要影响因素。     

Biological nitrogen and carbon removal in a gravity flow biomass concentrator reactor for municipal sewage treatment

A novel membrane system, the Biomass Concentrator Reactor (BCR), was evaluated as an alternative technology for the treatment of municipal wastewater. Because the BCR is equipped with a membrane whose average poresize is 20 μm (18–28 μm), the reactor requires low-pressure differential to operate (gravity). The effectiveness of this system was evaluated for the removal of carbon and nitrogen using two identical BCRs, identified as conventional and hybrid, that were operated in parallel. The conventional reactor was operated under full aerobic conditions (i.e., organic carbon and ammonia oxidation), while the hybrid reactor incorporated an anoxic zone for nitrate reduction as well as an aerobic zone for organic carbon and ammonia oxidation. Both reactors were fed synthetic wastewater at a flow rate of 71 L d^?1, which resulted in a hydraulic retention time of 9 h. In the case of the hybrid reactor, the recycle flow from the aerobic zone to the anoxic zone was twice the feed flow rate. Reactor performance was evaluated under two solids retention times (6 and 15 d). Under these conditions, the BCRs achieved nearly 100% mixed liquor solids separation with a hydraulic head differential of less than 2.5 cm. The COD removal efficiency was over 90%. Essentially complete nitrification was achieved in both systems, and nitrogen removal in the hybrid reactor was close to the expected value (67%).     

序批式气升环流反应器处理硝基苯废水

采用序批式气升环流反应器(SAR)处理硝基苯废水,研究了硝基苯浓度和COD/N对处理过程的影响,分析了缺氧段COD和硝基苯降解动力学。结果表明,硝基苯在缺氧段被还原为苯胺,而苯胺在好氧段得到快速降解。硝基苯与基质(葡萄糖-COD)最佳质量比为1∶35~1∶25,该条件下反应器对硝基苯和COD去除率分别可达99%~100%和92%~94%。由于受传质限制,进水需要维持106 mg/L的氨氮(葡萄糖-COD/N比值为100∶10)以满足缺氧段微生物对氨氮的营养需要。缺氧段COD的降解符合二级动力学,反应速率常数k2为2.7×10-4L·mg/h;硝基苯的降解符合一级动力学,反应速率常数k1为0.14 h-1。研究表明,序批式气升环流反应器可作为一种简单而有效的反应器用于处理硝基苯废水。     

Increasing the recovery of heavy metal ions using two microbial fuel cells operating in parallel with no power output

The present study aimed to improve the performance of microbial fuel cells (MFCs) by using an intermittent connection period without power output. Connecting two MFCs in parallel improved the voltage output of both MFCs until the voltage stabilized. Electric energy was accumulated in two MFCs containing heavy metal ions copper, zinc, and cadmium as electron acceptors by connection in parallel for several hours. The system was then switched to discharge mode with single MFCs with a 1000-Ω resistor connected between anode and cathode. This method successfully achieved highly efficient removal of heavy metal ions. Even when the anolyte was run in sequencing batch mode, the insufficient voltage and power needed to recover heavy metals from the cathode of MFCs can be complemented by the developed method. The average removal ratio of heavy metal ions in sequencing batch mode was 67 % after 10 h. When the discharge time was 20 h, the removal ratios of zinc, copper, and cadmium were 91.5, 86.7, and 83.57 %, respectively; the average removal ratio of these ions after 20 h was only 52.1 % for the control group. Therefore, the average removal efficiency of heavy metal ions increased by 1.75 times using the electrons stored from the bacteria under the open-circuit conditions in parallel mode. Electrochemical impedance data showed that the anode had lower solution resistance and polarization resistance in the parallel stage than as a single MFC, and capacitance increased with the length of time in parallel.

     

Urea removal coupled with enhanced electricity generation in single-chambered microbial fuel cells

High concentration of total ammonia nitrogen (TAN) in the form of urea is known to inhibit the performance of many biological wastewater treatment processes. Microbial fuel cells (MFCs) have great potential for TAN removal due to its unique oxic/anoxic environment. In this study, we demonstrated that increased urea (TAN) concentration up to 3940 mg/L did not inhibit power output of single-chambered MFCs, but enhanced power generation by 67% and improved coulombic efficiency by 78% compared to those obtained at 80 mg/L of TAN. Over 80% of nitrogen removal was achieved at TAN concentration of 2630 mg/L. The increased nitrogen removal coupled with significantly enhanced coulombic efficiency, which was observed for the first time, indicates the possibility of a new electricity generation mechanism in MFCs: direct oxidation of ammonia for power generation. This study also demonstrates the great potential of using one MFC reactor to achieve simultaneous electricity generation and urea removal from wastewater.

     

Phytoextraction of Pb,Cr, Ni,and Zn using the aquatic plant Limnobium laevigatum and its potential use in the treatment of wastewater

In order to study the bioaccumulation of Pb, Cr, Ni, and Zn and the stress response, the floating aquatic plant Limnobium laevigatum was exposed to increasing concentrations of a mixture of these metals for 28 days, and its potential use in the treatment of wastewater was evaluated. The metal concentrations of the treatment 1 (T1) were Pb 1 μg L⁻¹, Cr 4 μg L⁻¹, Ni 25 μg L⁻¹, and Zn 30 μg L⁻¹; of treatment 2 (T2) were Pb 70 μg L⁻¹, Cr 70 μg L⁻¹, Ni 70 μg L⁻¹, and Zn 70 μg L⁻¹; and of treatment 3 (T3) were Pb 1000 μg L⁻¹, Cr 1000 μg L⁻¹, Ni 500 μg L⁻¹, and Zn 100 μg L⁻¹, and there was also a control group (without added metal). The accumulation of Pb, Cr, Ni, and Zn in roots was higher than in leaves of L. laevigatum, and the bioconcentration factor revealed that the concentrations of Ni and Zn in the leaf and root exceeded by over a thousand times the concentrations of those in the culture medium (2000 in leaf and 6800 in root for Ni; 3300 in leaf and 11,500 in root for Zn). Thus, this species can be considered as a hyperaccumulator of these metals. In general, the changes observed in the morphological and physiological parameters and the formation of products of lipid peroxidation of membranes during the exposure to moderate concentrations (T2) of the mixture of metals did not cause harmful effects to the survival of the species within the first 14 days of exposure. Taking into account the accumulation capacity and tolerance to heavy metals, L. laevigatum is suitable for phytoremediation in aquatic environments contaminated with moderated concentrations of Cr, Ni, Pb, and Zn in the early stages of exposure.

     

Enhanced removal of heavy metals in primary treatment using coagulation and flocculation.

The goal of this study was to determine the removal efficiencies of chromium, copper, lead, nickel, and zinc from raw wastewater by chemically enhanced primary treatment (CEPT) and to attain a total suspended solids removal goal of 80%. Operating parameters and chemical doses were optimized by bench-scale tests. Locally obtained raw wastewater samples were spiked with heavy metal solutions to obtain representative concentrations of metals in wastewater. Jar tests were conducted to compare the metals removal efficiencies of the chemical treatment options using ferric chloride, alum, and anionic polymer. The results obtained were compared with those from other studies. It was concluded that CEPT using ferric chloride and anionic polymer is more effective than CEPT using alum for metals removal. The CEPT dosing of 40 mg/L ferric chloride and 0.5 mg/L polymer enhanced heavy metals removal efficiencies by over 200% for chromium, copper, zinc, and nickel and 475% for lead, compared with traditional primary treatment. Efficient metals capture during CEPT can result in increased allowable headworks loadings or lower metal levels in the outfall.     

铁盐絮凝+MBR处理钨冶炼含砷含氨氮废水

选用铁盐絮凝+MBR组合系统对钨冶炼废水进行了实验研究,考察了组合系统对废水中As、COD、NH+4-N和TN的去除效果。结果表明,系统对As、COD、NH+4-N和TN的去除效果较好,去除率分别为97.2%、93.4%、74.0%和52.8%;系统的抗流量冲击能力和抗有机物负荷冲击能力较强。     

Preparation of macromolecular heavy metal coagulant and treatment of wastewater containing copper.

Many treatment technologies for wastewater containing heavy metals have been developed in recent years, but these technologies have some disadvantages, such as poor removing efficiency and complex operation. For this reason, a macromolecular heavy metal coagulant polyethyleneimine-sodium xanthogenate (PEX) was prepared by grafting a xanthogenate group to polyethyleneimine. It was determined that PEX has the function of removing both turbidity and copper ions. It was also determined that copper ions and turbidity have a cooperative removal effect with each other in the process of treating wastewater containing both turbidity and copper ions by PEX. The investigation showed that PEX is an amphoteric polyelectrolyte. At lower pH values, the amino groups of the macromolecule are electrically positive; therefore, turbidity is removed because of electroneutralization coagulation; at higher pH values, both amino groups and xanthogenic radical groups contribute to the removal of heavy metals, as a result of chelation. Compared with traditional chemical precipitation by calcium oxide and coagulation by an ordinary inorganic coagulant, PEX showed obvious advantages, for example, removing both turbidity and copper ions, higher removal efficiency, lower suitable pH value, and higher floc settlement velocity.     

Preparation of calcium oxalate—bromopyrogallol red inclusion sorbent and application to treatment of cationic dye and heavy metal wastewaters

Background, aim, and scope  Dye pollutants are a major class of environmental contaminants. Over 100,000 dyes have been synthesized worldwide and more than 700,000 tons are produced annually and over 5% are discharged into aquatic environments. The adsorption or sorption is one of the most efficient methods to remove dye and heavy metal pollutants from wastewater. However, most of the present sorbents often bear some disadvantages, e.g. low sorption capacity, difficult separation of spoil, complex reproduction, or secondary pollution. Development of novel sorbents that can overcome these limitations is desirable. Materials and methods  On the basis of the chemical coprecipitation of calcium oxalate (CaC₂O₄), bromopyrogallol red (BPR) was embedded during the growing of CaC₂O₄ particles. The ternary C₂O₄ ^2––BPR–Ca²⁺ sorbent was yielded by the centrifugation. Its composition was determined by spectrophotometry and AAS, and its structure and morphology were characterized by powder X-ray diffraction (XRD), laser particle-size analysis, and scanning electron microscopy (SEM). The adsorption of ethyl violet (EV) and heavy metals, e.g. Cu(II), Cd(II), Ni(II), Zn(II), and Pb(II) were carried out and their removal rate determined by spectrophotometry and ICP-OES. The adsorption performance of the sorbent was compared with powder activated carbon. The Langmuir isothermal model was applied to fit the embedment of BPR and adsorption of EV. Results  The saturation number of BPR binding to CaC₂O₄ reached 0.0105 mol/mol and the adsorption constant of the complex was 4.70 × 10⁵ M^–1. Over 80% of the sorbent particles are between 0.7 and 1.02 μm, formed by the aggregation of the global CaC₂O₄/BPR inclusion grains of 30–50 nm size. Such a material was found to adsorb cationic dyes selectively and sensitively. Ethyl violet (EV) was used to investigate the adsorption mechanism of the material. One BPR molecule may just bind with one EV molecule. The CaC₂O₄/BPR inclusion material adsorbed EV over two times more efficiently than the activated carbon. The adsorption of EV on the CaC₂O₄/BPR inclusion sorbent was complete in only 5 min and the sedimentation complete in 1 h. However, those of EV onto activated carbon took more than 1.5 and 5 h, respectively. The treatment of methylene blue and malachite green dye wastewaters indicated that only 0.4% of the sorbent adsorbed over 80% of color substances. Besides, the material can also adsorb heavy metals by complexation with BPR. Over 90% of Pb²⁺, and approximately 50% of Cd²⁺ and Cu²⁺, were removed in a high Zn²⁺-electroplating wastewater when 3% of the material was added. Eighty-six percent of Cu²⁺, and 60% of Ni²⁺ and Cd²⁺, were removed in a high Cd²⁺-electroplating wastewater. Discussion  The embedment of BPR into CaC₂O₄ particles responded to the Langmuir isothermal adsorption. As the affinity ligand of Ca²⁺, BPR with sulfonic groups may be adsorbed into the temporary electric double layer during the growing of CaC₂O₄ particles. Immediately, C₂O₄ ^2– captured the Ca²⁺ to form the CaC₂O₄ outer enclosed sphere. Thus, BPR may be released and embedded as a sandwich between CaC₂O₄ layers. The adsorption of EV on the sorbent obeyed the Langmuir isothermal equation and adsorption is mainly due to the ion-pair attraction between EV and BPR. Different from the inclusion sorbent, the activated carbon depended on the specific surface area to adsorb organic substances. Therefore, the adsorption capacity, equilibrium, and sedimentation time of the sorbent are much better than activated carbon. The interaction of heavy metals with the inclusion sorbent responded to their coordination. Conclusions  By characterizing the C₂O₄ ^2––BPR–Ca²⁺ inclusion material using various modern instruments, the ternary in situ embedment particle, [(CaC₂O₄)₉₅(BPR)] _n ^2n–, an electronegative, micron-sized adsorbent was synthesized. It is selective, rapid, and highly effective for adsorbing cationic dyes and heavy metals. Moreover, the adsorption is hardly subject to the impact of electrolytes. Recommendations and perspectives  The present work provides a simple and valuable method for preparing the highly effective adsorbent. If a concentrated BPR wastewater was reused as the inclusion reactant, the sorbent will be low cost. By selecting the inclusion ligand with a special structure, we may prepare some particular functional materials to recover the valuable substances from seriously polluted wastewaters. The recommended method will play a significant role in development of advanced adsorption materials. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Treatment of tannery wastewater in a pilot-scale hybrid constructed wetland system in Bangladesh

This paper reports the pollutant removal performances of a hybrid wetland system in Bangladesh for the treatment of a tannery wastewater. The system consisted of three treatment stages: a subsurface vertical flow (VF) wetland, followed by a horizontal flow (HF) and a VF wetland. The wetlands were planted with common reed (Phragmites australis), but employed different media, including organic coco-peat, cupola slag and pea gravel. In the first stage, experimental results demonstrated significant removal of ammonia (52%), nitrate (54%), BOD (78%), and COD (56%) under high organics loading rate (690 g COD m⁻² d⁻¹); simultaneous nitrification, denitrification, and organics degradation were attributed to the unique characteristics of the coco-peat media, which allowed greater atmospheric oxygen transfer for nitrification and organic degradation, and supply of organic carbon for denitrification. The second stage HF wetland produced an average PO₄ removal of 61%, primarily due to adsorption by the iron-rich cupola slag media. In the third treatment stage, which was filled with gravel media, further BOD removal (78%) from the tannery wastewater depleted organic carbon, causing the accumulation of NO₃ in the wastewater. Overall, the average percentage removals of NH₃-N, NO₃-N, BOD, COD, and PO₄ were 86%, 50%, 98%, 98% and 87%, respectively, across the whole hybrid system. The results provided a strong evidence to support widespread research and application of the constructed wetland as a low-cost, energy-efficient, wastewater treatment technology in Bangladesh.     

活性焦吸附处理一硝基甲苯(MNT)废水

一硝基甲苯(MNT)废水是一种具有高毒性、难降解的火炸药废水。以活性焦为吸附剂,研究了活性焦对MNT废水中COD的吸附性能及pH、时间、温度和活性焦用量对吸附效果的影响,并分析了吸附前后MNT废水水质和急性毒性的变化。实验结果表明,pH、时间和活性焦用量是影响吸附效果的主要因素,吸附过程符合拟二级动力学,吸附速率常数为1.01×10-2g/(mg·min),可以用Freundlich吸附等温线来描述,等温线常数为Kf=1.14×10-4,n=0.58;在pH为3,温度为20℃,活性焦用量为80g/L的条件下吸附MNT废水3 h,COD的去除率达到72.0%,急性毒性下降了98.6%,表明活性焦能有效地吸附处理MNT废水。     

直接磁场对特定厌氧污泥活性影响的研究

在优势菌生物除铬系统中悬挂表面磁场分别为0～6 mT和0～20 mT的磁片,分别控制磁片之间的磁场强度介于0～4.5 mT和0～14 mT,以未加磁场的对照系统作为参照,考察试验污泥活性的变化.试验结果表明,反应器中磁场强度为0～4.5 mT时,对厌氧活性污泥活性的促进效果较好,最大产甲烷速率(Umax.CH4)达64.3 mL CH4/g VSS·d,比非磁场系统提高20.6%,消耗单位COD产甲烷量为0.140 mL CH4/mg COD,比系统非磁场系统提高70.7%.同时发现了磁场的引入,提高了试验污泥利用COD物质生成甲烷的效率,对于低有机负荷重金属废水的生物净化尤其意义重大.     

The application of zero-water discharge system in treating diffuse village wastewater and its benefits in community afforestation

The proposed on-site zero-water discharge system was comprised of four main components: anaerobic tank, aerobic bioreactor, activated soil filter and water-collecting well. The results demonstrate that at 350 m³ day⁻¹ of hydraulic load, the system can effectively remove pollutants from the wastewater, e.g., 86% removal of COD; 87% removal of SS; 80% removal of TP and 71% removal of TN. The growth states of the grasses, macrophytes and arbors in the activated soil filter were better than the control. The life of the activated soil filter was estimated to be ∼12-15 yrs, based on the laboratory microcosm studies. However, humic acid contents and soil porosity have suggested that the activated soil filter was able to regenerate itself and thereby prolonging its life by reducing clogging of the pores. The results suggest that the zero-water discharge system was a promising bio-measure in treating diffuse village wastewater and benefiting community afforestation.     

Multi-component adsorption of copper,nickel and zinc from aqueous solutions onto activated carbon prepared from date stones

The removal of Cu²⁺, Ni²⁺, and Zn²⁺ ions from their multi-component aqueous mixture by sorption on activated carbon prepared from date stones was investigated. In the batch tests, experimental parameters were studied, including solution pH, contact time, initial metal ions concentration, and temperature. Adsorption efficiency of the heavy metals was pH-dependent and the maximum adsorption was found to occur at around 5.5 for Cu, Zn, and Ni. The maximum sorption capacities calculated by applying the Langmuir isotherm were 18.68 mg/g for Cu, 16.12 mg/g for Ni, and 12.19 mg/g for Zn. The competitive adsorption studies showed that the adsorption affinity order of the three heavy metals was Cu²⁺?>?Ni²⁺?>?Zn²⁺. The test results using real wastewater indicated that the prepared activated carbon could be used as a cheap adsorbent for the removal of heavy metals in aqueous solutions.     

Equilibrium, kinetic, and thermodynamic biosorption of Pb(II), Cr(III), and Cd(II) ions by dead anaerobic biomass from synthetic wastewater

Purpose

Heavy metals are toxic pollutants released into the environment as a result of different industrial activities. Biosorption of heavy metals from aqueous solutions is a new technology for the treatment of industrial wastewater. The aim of the present research is to highlight the basic biosorption theory to heavy metal removal.

Materials and methods

Heterogeneous cultures mostly dried anaerobic bacteria, yeast (fungi), and protozoa were used as low-cost material to remove metallic cations Pb(II), Cr(III), and Cd(II) from synthetic wastewater. Competitive biosorption of these metals was studied.

Results

The main biosorption mechanisms were complexation and physical adsorption onto natural active functional groups. It is observed that biosorption of these metals was a surface process. The main functional groups involved in these processes were hydroxyl (–OH) and carboxylic groups (C=O) with 37, 52, and 31 and 21, 14, and 34 % removal of Pb(II), Cr(III), and Cd(II), respectively. Langmuir was the best model for a single system. While extended Langmuir was the best model for binary and ternary metal systems. The maximum uptake capacities were 54.92, 34.78, and 29.99 mg/g and pore diffusion coefficients were 7.23, 3.15, and 2.76?×?10^?11 m²/s for Pb(II), Cr(III), and Cd(II), respectively. Optimum pH was found to be 4. Pseudo-second-order was the best model to predict the kinetic process. Biosorption process was exothermic and physical in nature.

Conclusions

Pb(II) offers the strongest component that is able to displace Cr(III) and Cd(II) from their sites, while Cd(II) ions are the weakest adsorbed component.     

Macro-fungal (Agaricus bisporus) wastes as an adsorbent in the removal of the acid red 97 and crystal violet dyes from ideal colored effluents

The wastes from the macro-fungus Agaricus bisporus were used as an eco-friendly and low-cost adsorbent for the treatment of colored effluents containing the recalcitrant dyes, acid red 97 (AR97) and crystal violet (CV). The macro-fungal waste presented an amorphous structure, composed of particles with different sizes and shapes. Also, it presents typical functional chemical groups of proteins and carbohydrates with a point of zero charge of 4.6. The optimum conditions for the dosage were found to be as follows: 0.5 g L⁻¹ with an initial pH at 2.0 for the AR97 and 8.0 for the CV. From the kinetic test, it was found that it took 210 min and an adsorption capacity of 165 mg g⁻¹ for the AR97. Concerning the CV kinetics, it took 120 min to reach the equilibrium and it achieved an adsorption capacity of 165.9 mg g⁻¹. The Elovich model was the most proper model for describing the experimental data, achieving an R² ≥ 0.997 and MSE ≤ 36.98 (mg g⁻¹)². The isotherm curves were best represented by the Langmuir model, predicting maximum adsorption capacity of 372.69 and 228.74 mg g⁻¹ for the AR97 and CV, respectively. The process was spontaneous and favorable for both dyes. The ∆H⁰ values were 9.53 and 10.69 kJ mol⁻¹ for AR97 and CV, respectively, indicating physical and endothermic adsorption. Overall, the wastes from Agaricus bisporus have the potential to adsorb cationic and anionic dyes, thus solving environmental problems related to water quality and residue disposal.

     

In vitro assessment of AhR-mediated activities of TCDD in mixture with humic substances

Humic substances (HS) are ubiquitous natural products of decomposition of dead organic matter. HS is present in most freshwaters at concentrations ranging from 0.5 to 50 mg L⁻¹. Organic carbon can represent 20% dry weight of sediments. Recently, the interaction of dissolved HS with the aryl hydrocarbon receptor (AhR) has been demonstrated. The AhR is a cytosolic receptor to which persistent organic pollutants (POPs) can bind and many of their toxic effects are mediated through interactions with this receptor. We describe in vitro effects (using H4IIE-luc cells) of binary mixtures of various HS with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), since in contaminated environments these compounds occur simultaneously. Six out of 12 HS samples activated AhR even at environmentally relevant concentrations (17 mg L⁻¹), but did not reach the full AhR-activation even at excessive concentration. In simultaneous exposure of H4IIE-luc to HS (17 mg L⁻¹) and TCDD (1.2 pM) without any preincubation prior to exposure, either significant additive or facilitative effects were observed. No negative interactions, due to possible sorption of TCDD to HS was observed. Nevertheless, if the HS–TCDD binary mixture was preincubated for 6 days prior to the exposure on H4IIE-luc cells, the additive and facilitative effects were less due to possible sorption of TCDD onto HS. Similar results were obtained from analogous experiments with greater concentrations of both TCDD and HS.