Effect of deposit age on adsorption and desorption behaviors of ammonia nitrogen on municipal solid waste

Ammonia nitrogen pollution control is an urgent issue of landfill. This research aims to select an optimal refuse for ammonia nitrogen removal in landfill from the point of view of adsorption and desorption behavior. MSW (municipal solid waste) samples which deposit ages were in the range of 5 to 15 years (named as R₁₅, R₁₁, R₇, and R₅) were collected from real landfill site. The ammonia nitrogen adsorption behaviors of MSW including equilibrium time, adsorption isotherms, and desorption behaviors including equilibrium time were determined. Furthermore, the effects of pH, OM, Cu(II), Zn(II), and Pb(II) on adsorption and desorption behavior of ammonia nitrogen were conducted by orthogonal experiment. The equilibrium time of ammonia nitrogen adsorption by each tested MSW was very short, i.e., 20 min, whereas desorption process needed 24 h and the ammonia nitrogen released from refuses was much lesser than that adsorbed, i.e., accounted for 3.20 % (R₁₅), 14.32 % (R₁₁), 20.59 % (R₇), and 20.50 % (R₅) of each adsorption quantity, respectively. The maximum adsorption capacity estimated from Langmuir isotherm appeared in R₁₅-KCl, i.e., 25,000 mg kg^?1. The best condition for ammonia nitrogen removal from leachate was pH >7.5, OM 23.58 %, Cu(II) <5 mg L^?1, Zn(II) <10 mg L^?1, and Pb(II) <1 mg L^?1. Ammonia nitrogen in landfill leachate could be quickly and largely absorbed by MSW but slowly and infrequently released. The refuse deposited for 15 years could be a suitable material for ammonia nitrogen removal.     

微波诱导AC/Cu、AC/Fe催化非均相Fenton 反应催化降解垃圾渗滤液

采用活性炭载体负载Cu、Fe为催化剂,在微波诱导作用下,对垃圾渗滤液污染物进行降解。实验结果表明,活性炭负载金属前经适当浓度硝酸浸泡处理后,催化剂对COD去除率提高可超过15%,过高硝酸盐浓度对COD去除有不利影响;催化剂对COD去除率随Cu、Fe金属负载量增加呈先增加后降低的趋势,催化剂对Cu、Fe的最佳负载量分别为质量百分比2.11%和1.12%。对于AC-Cu体系,在初始pH=3,H2O2投加量为4.98×103mg/L,催化剂用量为5.0×103mg/L,420 W功率下微波辐射10 min时,垃圾渗滤液COD去除率可达到84.13%;对于AC-Fe体系,当H2O2投加量为0.33×103mg/L,催化剂AC-Fe用量为2.0×104mg/L,420 W功率下微波作用10 min时,垃圾渗滤液COD去除率为60.16%。分析2种催化剂对COD去除差异的原因,可能是催化剂AC-Cu表面单分子分布的阈值比AC-Fe高。降解液的pH值对AC-Cu体系、AC-Fe体系COD去除影响存在拐点,最高COD去除率点对应的降解液pH值为3。微波辐射功率较低时,体系COD去除率随辐射功率增加而增加;辐射功率较高时,高温下垃圾渗滤液中有机硫化物分解成小分子硫化物,对催化剂活性存在一定抑制作用。     

Landfill leachate treatment by immediate one-step lime precipitation,carbonation, and phytoremediation fine-tuning

The high pollutant load of sanitary landfill leachates poses a huge challenge in the search for efficient and environment friendly solutions for their treatment. The objective of this work was to study an integrated solution of environmentally friendly technologies — immediate one-step lime precipitation (IOSLP), carbonation (CB), and phytoremediation (Phyt) — to treat a sanitary landfill leachate. In the leachate sample treatment by IOSLP, the influence of CaO concentration (18.2–33.3 g_CaO L^?1) and stirring time (2–60 min) on the sludge sedimentability and pollutant removal was studied. Organic load and ammonia nitrogen (AN) removal increases with CaO added, as well as sludge volume. Stirring time has a small influence on organic load and AN removal, presenting a minimum for sludge volume. Thus, the best operational conditions were chosen as 27.6 g_CaO L^?1, and 40-min stirring time, with 64% chemical oxygen demand (COD) removal. Sludge humidity was 2.1%, making dewatering needless. IOSLP supernatant was submitted to CB by atmospheric CO₂, and 100% removals in AN and hardness were attained. Effluents from IOSLP and IOSLP?+?CB were utilized in Phyt tests, with Vetiver (Chrysopogon zizanioides (L.) Roberty). The best COD removal (37%) during Phyt was attained for the samples treated by IOSLP?+?CB.

     

Iron-loaded mangosteen as a heterogeneous Fenton catalyst for the treatment of landfill leachate

Iron-loaded mangosteen shell powder (Fe-MSP) was found as an effective heterogeneous Fenton catalyst for the treatment of stabilized landfill leachate. Sonolytically produced catalyst has higher efficiency than other catalysts. At the optimal conditions (pH 3, catalyst concentration of 1,750 mg/L and hydrogen peroxide concentration of 0.26 M), 81 % of the chemical oxygen demand (COD) was removed effectively from the landfill leachate. But, the efficiency of Fe-MSP was reduced in the first recycling due to the poisoning of active sites. A metal leaching study indicated that the degradation of the pollutant is mainly due to solid Fe ions present in Fe-MSP rather than the leached ferrous and ferric ions. Hydroxyl radical production in the system was confirmed by the Fenton oxidation of benzoic acid. Compared to the homogeneous Fenton process, the heterogeneous Fenton process using Fe-MSP had higher COD removal efficiency, indicating the practical applicability of the prepared catalyst.     

Nitrogen removal via the nitrite pathway during wastewater co-treatment with ammonia-rich landfill leachates in a sequencing batch reactor

The biological treatment of ammonia-rich landfill leachates due to an inadequate C to N ratio requires expensive supplementation of carbon from an external carbon source. In an effort to reduce treatment costs, the objective of the study was to determine the feasibility of nitrogen removal via the nitrite pathway during landfill leachate co-treatment with municipal wastewater. Initially, the laboratory-scale sequencing batch reactor (SBR) was inoculated with nitrifying activated sludge and fed only raw municipal wastewater (RWW) during a start-up period of 9 weeks. Then, in the co-treatment period, consisting of the next 17 weeks, the system was fed a mixture of RWW and an increasing quantity of landfill leachates (from 1 to 10 % by volume). The results indicate that landfill leachate addition of up to 10 % (by volume) influenced the effluent quality, except for BOD₅. During the experiment, a positive correlation (r ²?=?0.908) between ammonia load in the influent and nitrite in the effluent was observed, suggesting that the second step of nitrification was partially inhibited. The partial nitrification (PN) was also confirmed by fluorescence in situ hybridisation (FISH) analysis of nitrifying bacteria. Nitrogen removal via the nitrite pathway was observed when the oxygen concentration ranged from 0.5 to 1.5 mg O₂/dm³ and free ammonia (FA) ranged from 2.01 to 35.86 mg N-NH₃/dm³ in the aerobic phase. Increasing ammonia load in wastewater influent was also correlated with an increasing amount of total nitrogen (TN) in the effluent, which suggested insufficient amounts of assimilable organic carbon to complete denitrification. Because nitrogen removal via the nitrite pathway is beneficial for carbon-limited and highly ammonia-loaded mixtures, obtaining PN can lead to a reduction in the external carbon source needed to support denitrification.     

Cr(VI) and COD removal from landfill leachate by polyculture constructed wetland at a pilot scale

Four subsurface horizontal-flow constructed wetlands (CWs) at a pilot scale planted with a polyculture of the tropical plants Gynerium sagittatum (Gs), Colocasia esculenta (Ce) and Heliconia psittacorum (He) were evaluated for 7 months. The CW cells with an area of 17.94 m² and 0.60 m (h) each and 0.5 m of gravel were operated at continuous gravity flow (Q?=?0.5 m³ day^?1) and a theoretical HRT of 7 days each and treating landfill leachate for the removal of filtered chemical oxygen demand (COD_f), BOD₅, TKN, NH₄ ⁺, NO₃ ^?, PO₄ ^3?–P and Cr(VI). Three CWs were divided into three sections, and each section (5.98 m²) was seeded with 36 cuttings of each species (plant density of six cuttings per square metre). The other unit was planted randomly. The final distributions of plants in the bioreactors were as follows: CW I (He-Ce-Gs), CW II (randomly), CW III (Ce-Gs-He) and CW IV (Gs-He-Ce). The units received effluent from a high-rate anaerobic pond (BLAAT®). The results show a slightly alkaline and anoxic environment in the solid-liquid matrix (pH?=?8.0; 0.5–2 mg L^?1 dissolved oxygen (DO)). COD_f removal was 67 %, BOD₅ 80 %, and TKN and NH₄ ⁺ 50–57 %; NO₃ ^? effluents were slightly higher than the influent, PO₄ ^3?–P (38 %) and Cr(VI) between 50 and 58 %. CW IV gave the best performance, indicating that plant distribution may affect the removal capacity of the bioreactors. He and Gs were the plants exhibiting a translocation factor (TF) of Cr(VI) >1. The evaluated plants demonstrated their suitability for phytoremediation of landfill leachate, and all of them can be categorized as Cr(VI) accumulators. The CWs also showed that they could be a low-cost operation as a secondary system for treatment of intermediated landfill leachate (LL).     

Adsorption characteristics of Cu(II) from aqueous solution onto biochar derived from swine manure

The purpose of this study was to investigate adsorption characteristic of swine manure biochars pyrolyzed at 400 °C and 700 °C for the removal of Cu(II) ions from aqueous solutions. The biochars were characterized using BET surface area, Fourier transform infrared spectroscopy (FTIR), zeta potential, scanning electron microscopy/energy dispersive spectrometer (SEM–EDS), and X-ray diffraction (XRD). The adsorption of Cu(II) ions by batch method was carried out and the optimum conditions were investigated. The adsorption processes of these biochars are well described by a pseudo-second-order kinetic model, and the adsorption isotherm closely fitted the Sips model. Thermodynamic analysis suggested that the adsorption was endothermic. The maximum Cu(II) adsorption capacities of biochars derived from fresh and composted swine manure at 400 °C were 17.71 and 21.94 mg g^?1, respectively, which were higher than those at 700 °C. XRD patterns indicated that the silicate and phosphate particles within the biochars served as adsorption sites for Cu(II). The removal of Cu(II) ions from industrial effluent indicated that the fresh swine manure biochar pyrolyzed at 400 °C can be considered as an effective adsorbent.     

Hybrid zero valent iron (ZVI)/H2O2 oxidation process for landfill leachate treatment with novel nanosize metallic calcium/iron composite

A novel nanosize metallic calcium/iron dispersed reagent was synthesized and tested as coagulant/catalyst in a hybrid zero valent iron (ZVI)/H₂O₂ oxidation process to treat leachate. Two different types of leachates, one from municipal solid waste (MSW) tipping hall (MSWIL) and second from an MSW landfill site (MSWLL), were collected and characterized. The morphology, elemental composition, and mineral phases of the nano-Ca/CaO and nano-Fe/Ca/CaO were characterized by scanning electron microscopy–electron dispersive spectroscopy (SEM-EDS) and x-ray powder diffraction (XRD) analysis. The coagulation process with 2.5 g L^?1 nano-Ca/CaO attained 64.0, 56.0, and 20.7% removal of color, chemical oxygen demand (COD), and total suspended solids (TSS) in MSWLL. With only 1.0 g L^?1 of nano-Fe/Ca/CaO, relatively high color, COD and TSS removal was achieved in MSWLL at 67.5, 60.2, and 37.7%, respectively. The heavy metal removal efficiency reached 91–99% after treatment with nano-Fe/Ca/CaO in both leachate samples. The coupling process, using 1.0 g L^?1 of nano-Fe/Ca/CaO and 20 mM H₂O₂ doses, achieved enhancement removal of color, COD, and TSS, up to 95%, 96%, and 66%, respectively, without initial pH control. After this treatment, the color, COD, TSS, and heavy metals were significantly decreased, fitting the Korean discharge regulation limit. A hybrid coupled zero valent iron (ZVI)/H₂O₂ oxidation process with novel nanosized metallic calcium/iron dispersed reagent proved to be a suitable treatment for dealing with leachate samples.

Implications: Conventional treatments (biological or physicochemical) are not sufficient anymore to reach the level of purification needed to fully reduce the negative impact of landfill leachates on the environment. This implies that new treatment alternatives species must be proposed. A coupled zero valent iron (ZVI)/H₂O₂ oxidation process proved to be a suitable treatment for dealing with leachate samples. Coagulation with nFe/Ca/CaO allows 91–99% of heavy metals removal. The coupled coagulation–oxidation process by nFe/Ca/CaO reveals excellent ability to treat leachate. After coupled treatment the color, COD, and TSS were also much lower than the discharge regulation limit.     

Potential use of Caulerpa fastigiata biomass for removal of lead: kinetics, isotherms, thermodynamic, and characterization studies

The present study attempts to analyze the biosorption trend of biosorbent Caulerpa fastigiata (macroalgae) biomass for removal of toxic heavy metal ion Pb (II) from solution as a function of initial metal ion concentration, pH, temperature, sorbent dosage, and biomass particle size. The sorption data fitted with various isotherm models and Freundlich model was the best one with correlation coefficient of 0.999. Kinetic study results revealed that the sorption data on Pb (II) with correlation coefficient of 0.999 can best be represented by pseudo-second-order. The biosorption capacity (q _e ) of Pb (II) is 16.11?±?0.32 mg g^?1 on C. fastigiata biomass. Thermodynamic studies showed that the process is exothermic (ΔH° negative). Free energy change (ΔG°) with negative sign reflected the feasibility and spontaneous nature of the process. The SEM studies showed Pb (II) biosorption on selective grains of the biosorbent. The FTIR spectra indicated bands corresponding to –OH, COO^?, –CH, C?=?C, C?=?S, and –C–C– groups were involved in the biosorption process. The XRD pattern of the C. fastigiata was found to be mostly amorphous in nature.     

A Novel Design for Anaerobic Chemical Oxygen Demand and Nitrogen Removal from Leachate in a Semiaerobic Landfill

Abstract

The removal capacity of carbon and nitrogen from an artificial leachate was evaluated by using laboratory-scale columns, and a design was proposed to remove nitrogen more efficiently from a semiaerobic landfill. Five columns (i.e., two artificial municipal waste columns under anaerobic and semiaerobic conditions, an artificial construction waste column under semiaerobic conditions, and two crushed stone columns under anaerobic and semiaerobic conditions) were used. The influent load rates of organics [g chemical oxygen demand (COD)/m³ ·day], NH₄ ⁺, NO₃ ^?, and aeration conditions for the columns were varied, and the removal capacities of the columns for COD, NH₄ ⁺-N, and NO₃ ^?-N were measured.

Among the packed column materials, crushed stone was shown to be most effective in removing COD, NH₄ ⁺-N, and NO₃ ^?-N from artificial leachate. Average removal rates of crushed column under the semiaerobic condition (column D) for COD and NH₄ ⁺-N were estimated at about 150 g COD/m³·day and 20 g COD/m³ ·day, while those of crushed column under anaerobic condition (column E) for COD and NO₃ ^?-N at about 400 and 150 g COD/m³ ·day, respectively. It also was found that denitrification and nitrification reactions in column D occurred at the same time, and the ratio of denitrification to nitrification was estimated to be about 80%. Therefore, an anaerobic structure, which could be attached to the bottom of a main pipe in a semiaerobic landfill, is suggested to remove nitrogen and organic substances more effectively.     

Utilization of water chestnut for reclamation of water environment and control of cyanobacterial blooms

Overgrowth of water chestnut (Trapa spp.) is a regional problem throughout Asia and North America because of waterway blockage and water fouling upon decomposition. In the present study, we investigated the potential of water chestnut to control cyanobacterial blooms, via a high content of phenolic compounds. In addition, we assessed the impact of biomass harvesting and crude extract application on nutrient balance. We showed that the floating parts of water chestnut contained high concentrations of total phenolics (89.2 mg g^?1 dry weight) and exhibited strong antioxidant activity (1.31 mmol g^?1 dry weight). Methanol-extracted phenolics inhibited growth of Microcystis aeruginosa; the half maximal effective concentration (EC₅₀) of the extracted phenolics was 5.8 mg L^?1, which was obtained from only 103 mg L^?1 of dry biomass (the floating and submerged parts). However, the crude extracts also added important quantities of nitrogen, phosphorus, and potassium (1.49, 1.05, and 16.3 mg g^?1, respectively; extracted dry biomass weight basis); therefore, in practice, nutrient removal before and/or after the extraction is essential. On the other hand, biomass harvesting enables recovery of nitrogen, phosphorus, and potassium from the water environment (23.1, 2.9, and 18.7 mg g^?1, respectively; dry biomass weight basis). Our findings indicate that water chestnut contains high concentrations of phenolics and exhibits strong antioxidant activity. Utilization of these resources, including nutrients, will contribute to reclamation of the water environment, and also to disposal of wet biomass.     

城市生活垃圾填埋场渗滤液生化处理过程中重金属离子问题

我国对城市生活填埋场渗滤液处理技术的研究主要集中在COD与NH4 -N的去除上,对渗滤液中重金属离子的专项研究几乎未见报道.本文首先总结了国内外城市生活垃圾渗滤液中重金属的种类及浓度,在渗滤液中的存在状态,渗滤液中重金属与其他成分(有机物、氨氮)的相互作用关系,辨证分析了重金属在渗滤液生化处理过程中的有益作用和毒性,归纳了重金属在渗滤液生化处理过程中的变化规律,同时总结分析了重金属的去除技术.     

Evaluation of Acinetobacter sp. B9 for Cr (VI) resistance and detoxification with potential application in bioremediation of heavy-metals-rich industrial wastewater

Present work demonstrates Cr (VI) detoxification and resistance mechanism of a newly isolated strain (B9) of Acinetobacter sp. Bioremediation potential of the strain B9 is shown by simultaneous removal of major heavy metals including chromium from heavy-metals-rich metal finishing industrial wastewater. Strain B9 tolerate up to 350 mg L^?1 of Cr (VI) and also shows level of tolerance to Ni (II), Zn (II), Pb (II), and Cd (II). The strain was capable of reducing 67 % of initial 7.0 mg L^?1 of Cr (VI) within 24 h of incubation, while in presence of Cu ions 100 % removal of initial 7.0 and 10 mg L^?1 of Cr (VI) was observed with in 24 h. pH in the range of 6.0–8.0 and inoculum size of 2 % (v/v) were determined to be optimum for dichromate reduction. Fourier transform infrared spectroscopy and transmission electron microscopy studies suggested absorption or intracellular accumulation and that might be one of the major mechanisms behind the chromium resistance by strain B9. Scanning electron microscopy showed morphological changes in the strain due to chromium stress. Relevance of the strain for treatment of heavy-metals-rich industrial wastewater resulted in 93.7, 55.4, and 68.94 % removal of initial 30 mg L^?1 Cr (VI), 246 mg L^?1 total Cr, and 51 mg L^?1 Ni, respectively, after 144 h of treatment in a batch mode.     

Effects of silicon and copper on bamboo grown hydroponically

Due to its high growth rate and biomass production, bamboo has recently been proven to be useful in wastewater treatment. Bamboo accumulates high silicon (Si) levels in its tissues, which may improve its development and tolerance to metal toxicity. This study investigates the effect of Si supplementation on bamboo growth and copper (Cu) sensitivity. An 8-month hydroponic culture of bamboo Gigantocloa sp. “Malay Dwarf ” was performed. The bamboo plants were first submitted to a range of Si supplementation (0–1.5 mM). After 6 months, a potentially toxic Cu concentration of 1.5 μM Cu²⁺ was added. Contrary to many studies on other plants, bamboo growth did not depend on Si levels even though it absorbed Si up to 218 mg g^?1 in leaves. The absorption of Cu by bamboo plants was not altered by the Si supplementation; Cu accumulated mainly in roots (131 mg kg^?1), but was also found in leaves (16.6 mg kg^?1) and stems (9.8 mg kg^?1). Copper addition did not induce any toxicity symptoms. The different Cu and Si absorption mechanisms may partially explain why Si did not influence Cu repartition and concentration in bamboo. Given the high biomass and its absorption capacity, bamboo could potentially tolerate and accumulate high Cu concentrations making this plant useful for wastewater treatment.     

Electrooxidation of industrial wastewater containing 1,4-dioxane in the presence of different salts

The treatment of 1,4-dioxane solution by electrochemical oxidation on boron-doped diamond was studied using a central composite design and the response surface methodology to investigate the use of SO₄ ^2? and HCO₃ ^? as supporting electrolytes considering the applied electric current, initial chemical oxygen demand (COD) value, and treatment time. Two industrial effluents containing bicarbonate alkalinity, one just carrying 1,4-dioxane (S1), and another one including 1,4-dioxane and 2-methyl-1,3-dioxolane (S2), were treated under optimized conditions and subsequently subjected to biodegradability assays with a Pseudomonas putida culture. Electrooxidation was compared with ozone oxidation (O₃) and its combination with hydrogen peroxide (O₃/H₂O₂). Regarding the experimental design, the optimal compromise for maximum COD removal at minimum energy consumption was shown at the maximum tested concentrations of SO₄ ^2? and HCO₃ ^? (41.6 and 32.8 mEq L^?1, respectively) and the maximum selected initial COD (750 mg L^?1), applying a current density of 11.9 mA cm^?2 for 3.8 h. Up to 98 % of the COD was removed in the electrooxidation treatment of S1 effluent using 114 kWh per kg of removed COD and about 91 % of the COD from S2 wastewater applying 49 kWh per kg of removed COD. The optimal biodegradability enhancement was achieved after 1 h of electrooxidation treatment. In comparison with O₃ and O₃/H₂O₂ alternatives, electrochemical oxidation achieved the fastest degradation rate per oxidant consumption unit, and it also resulted to be the most economical treatment in terms of energy consumption and price per unit of removed COD.     

超声波-膜生物法联合处理垃圾焚烧厂渗滤液

采用超声波-膜生物法(MBR)联合处理垃圾渗滤液,探讨了超声波辐射时间和MBR的水力负荷对COD、NH3-N和TP去除的影响。结果表明,(1)超声波单独处理时,超声波辐射时间在30～90 s时,COD、NH3-N最大增加率分别34.31%、3.36%,而对TP的去除没有影响;(2)超声波-膜生物(MBR)联合处理时,超声波辐射时间为300 s,MBR的水力负荷为6.4 L/(m2.d)时,COD、NH3-N和TP的最佳去除率分别为92.20%、80.10%和91.12%;MBR的水力负荷为12.8 L/(m2.d),超声波辐射时间在5～20 min时,COD、NH3-N的最佳去除率分别为92.34%、79.93%,TP的浓度低于0.2 mg/L;MBR反应时间为7 h,超声波辐射时间为5～20 min,与未进行超声波辐射处理(超声波辐射时间为0 min)相比,COD、NH3-N的去除率增加了11.37%、15.26%;超声波预处理有助于提高后续MBR对COD、NH3-N的去除作用。     

Pentachlorophenol dechlorination and simultaneous Cr6+ reduction by Pseudomonas putida SKG-1 MTCC (10510): characterization of PCP dechlorination products, bacterial structure, and functional groups

It is the first report in which a novel psychrotrophic Pseudomonas putida SKG-1 strain was evaluated for simultaneous bioremediation of pentachlorophenol and Cr⁶⁺ under various cultural and nutritional conditions. Pentachlorophenol (PCP) dechlorination products, bacterial structure, and functional groups were characterized by gas chromatography and mass spectrometry (GC–MS), scanning electron microscope and energy dispersive X-ray spectroscopy (SEM–EDS), and Fourier-transform infrared (FTIR) techniques. The strain was extremely tolerant to excessively higher individual concentration of PCP (1,400 mg l^?1) and Cr⁶⁺ (4,300 mg l^?1). Increasing concentration of PCP and Cr⁶⁺ exerted inhibitory effect on bacterial growth and toxicants’ removal. The strain exhibited growth, and concomitantly remediated both the pollutants simultaneously over a broad pH (7.0–9.0) and temperature (28–32 °C) range; maximum growth, PCP dechlorination (87.5 %), and Cr⁶⁺ removal (80.0 %) occurred at optimum pH 8.0 and 30 °C (from initial PCP 100 mg l^?1 and Cr⁶⁺ 500 mg l^?1) under shaking (150 rpm) within 72 h incubation. Optimization of agitation (125 rpm) and aeration (0.4 vvm) in bioreactor further enhanced PCP dechlorination by ~10 % and Cr⁶⁺ removal by 2 %. A direct correlation existed between growth and bioremediation of both the toxicants. Among other heavy metals, mercury exerted maximum and cobalt minimum inhibitory effect on PCP dechlorination and Cr⁶⁺ removal. Chromate reductase activity was mainly associated with the supernatant and cytosolic fraction of bacterial cells. GC–MS analysis revealed the formation of tetrachloro-p-hydroquinone, 2,4,6-trichlorophenol, and 2,6-dichlorophenol as PCP dechlorination products. FTIR spectrometry indicated likely involvement of carbonyl and amide groups in Cr³⁺ adsorption, and SEM–EDS showed the presence of chromium on P. putida surface. Thus, our promising isolate can be ecofriendly employed for biotreatment of various industrial wastes contaminated with high PCP and Cr⁶⁺ concentrations.     

Novel chitosan/PVA/zerovalent iron biopolymeric nanofibers with enhanced arsenic removal applications

Enhanced removal application of both forms of inorganic arsenic from arsenic-contaminated aquifers at near-neutral pH was studied using a novel electrospun chitosan/PVA/zerovalent iron (CPZ) nanofibrous mat. CPZ was carefully examined using scanning electron microscopy (SEM) equipped with energy-dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), atomic fluorescence spectroscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermal gravimetric analysis (TGA). Application of the adsorbent towards the removal of total inorganic arsenic in batch mode has also been studied. A suitable mechanism for the adsorption has also been discussed. CPZ nanofibers mat was found capable to remove 200.0?±?10.0 mg g^?1 of As(V) and 142.9?±?7.2 mg g^?1 of As(III) from aqueous solution of pH 7.0 at ambient condition. Addition of ethylenediaminetetraacetic acid (EDTA) enabled the stability of iron in zerovalent state (ZVI). Enhanced capacity of the fibrous mat could be attributed to the high surface area of the fibers, presence of ZVI, and presence of functional groups such as amino, carboxyl, and hydroxyl groups of the chitosan and EDTA. Both Langmuir and Freundlich adsorption isotherms were applicable to describe the removal process. The possible mechanism of adsorption has been explained in terms of electrostatic attraction between the protonated amino groups of chitosan/arsenate ions and oxidation of arsenite to arsenate by Fentons generated from ZVI and subsequent complexation of the arsenate with the oxidized iron. These CPZ nanofibrous mats has been prepared with environmentally benign naturally occurring biodegradable biopolymer chitosan, which offers unique advantage in the removal of arsenic from contaminated groundwater.     

Scale-up of electrochemical oxidation system for treatment of produced water generated by Brazilian petrochemical industry

Scale-up of anodic oxidation system is critical to the practical application of electrochemical treatment in bio-refractory organic wastewater treatment. In this study, the scale-up of electrochemical flow system was investigated by treating petrochemical wastewater using platinized titanium (Ti/Pt) and boron-doped diamond (BDD) anodes. It was demonstrated that flow cell was successfully scaled-up because when it was compared with batch mode (Rocha et al. 2012b), higher performances on organic matter removal were achieved. Under the suitable operating conditions and better anode material, the chemical oxygen demand (COD) of petrochemical wastewater was reduced from 2,746 to 200 mg L^?1 within 5 h with an energy consumption of only 56.2 kWh m^?3 in the scaled-up BDD anode system. These results demonstrate that anode flow system is very promising in practical bio-refractory organic wastewater treatment.     

Examination of the influence of phenyltrimethylammonium chloride (PTMA) concentration on acetochlor adsorption by modified montmorillonite

The results presented in this paper show an impact of the concentration of the aromatic organic cation on the adsorption of acetochlor on the surface of the organic-modified montmorillonite. Natural montmorillonite from Bogovina (Boljevac municipality, Serbia) was used for organic modification in this experiment. Cation exchange capacity of this montmorillonite (86 mmol 100 g^?1 of clay) was determined using the methylene blue method. In pretreatment, montmorillonite was modified with NaCl. For the purpose of organic modification, three different concentrations of phenyltrimethylammonium chloride (PTMA) have been selected, based on calculated CEC value: 43 mmol 100 g^?1 of clay (0.5 CEC), 86 mmol 100 g^?1 of clay (1 CEC) and 129 mmol 100 g^?1 of clay (1.5 CEC). The changes in the properties of the inorganic and organic modified montmorillonite were examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and batch equilibrium method. Freundlich coefficients show higher uptake of the herbicide by montmorillonite modified with PTMA, compared to inorganic-modified montmorillonite. The results also indicate the influence of the organic cation concentration on the adsorption of the selected herbicide.