High chrome exhaustion in a non-float tanning process using a sulphonic aromatic acid

Tanning processes performed in drums consume large amounts of water and chemicals, most of which end up in the wastewater. This study explores an alternative approach at an industrial scale to the traditional pickle-chrome tanning method. The new method replaces formic and sulphuric acids with sulphonic aromatic acid. Because it is done without float, there is a sizeable reduction in the amount of added salt and chrome salt as well as an increase in temperatures at the end of the tanning process. From an environmental perspective, the new method offers important advantages. For instance, there is no float addition in the tannage. Also, there are reductions of 94% and 99%, respectively, in the discharge of chlorides and chrome, as well as a 75% reduction in the residual float. Our financial assessment demonstrated that the new method is 42% cheaper than a traditional approach.     

A potential new commercial method for processing leather to reduce environmental impact

INTRODUCTION: Current leather processing method involves dehairing and fibre opening employing lime and sulphide, which results in higher negative impact on the environment due to its uncleanness. This method of dehairing and fibre-opening process accounts for nearly 70-80% biochemical oxygen demand and chemical oxygen demand (COD) in tannery wastewater and also the generation of H(2)S gas. MATERIALS AND METHODS: Hence, an attempt has been made to reduce the environmental impact of the leather processing through a biochemical approach, employing proteolytic enzyme and sodium metasilicate for performing the above process more cleanly. RESULTS AND DISCUSSION: The developed process exhibits significant reduction in environmental parametres such as COD and total solid loads by 55% and 25%, respectively. This method completely avoids the formation of lime sludge. CONCLUSION: The functional properties of the leathers are also on par with conventionally processed leathers. Further, the process seems to be commercially viable.     

Minimization of the environmental impact in the unhairing of bovine hides

This study tests an alternative method to the traditional unhairing method used during the process of tanning the hides. The new method is based on the substitution of sodium sulfide by hydrogen peroxide as an unhairing agent in both hair recovery and recirculation of the floats employed in the process. The properties of the hides obtained using the two methods have been compared and the results indicate that those hides have similar physical, chemical, and organoleptic properties. However, the differences existing from an environmental point of view are significant. These include reductions of water consumption (approx 70%), chemical oxygen demand (approx 35%), toxicity (98%) and total kjendhal nitrogen (50%). Also, the risk associated with the production of hydrogen sulfide is eliminated, which implies a great improvement in terms of safety for the workers. Given the large amounts of water and chemical pollution discharged in the process, the reductions in absolute values represent a significant improvement. A financial assessment was carried out to demonstrate that the proposed new system is 16% more economic than the traditional one.     

Click chemistry approach to conventional vegetable tanning process: accelerated method with improved organoleptic properties

Click chemistry approaches are tailored to generate molecular building blocks quickly and reliably by joining small units together selectively and covalently, stably and irreversibly. The vegetable tannins such as hydrolyzable and condensed tannins are capable to produce rather stable radicals or inhibit the progress of radicals and are prone to oxidations such as photo and auto-oxidation, and their anti-oxidant nature is well known. A lot remains to be done to understand the extent of the variation of leather stability, color variation (lightening and darkening reaction of leather), and poor resistance to water uptake for prolonged periods. In the present study, we have reported click chemistry approaches to accelerated vegetable tanning processes based on periodates catalyzed formation of oxidized hydrolysable and condensed tannins for high exhaustion with improved properties. The distribution of oxidized vegetable tannin, the thermal stability such as shrinkage temperature (T _s) and denaturation temperature (T _d), resistance to collagenolytic activities, and organoleptic properties of tanned leather as well as the evaluations of eco-friendly characteristics were investigated. Scanning electron microscopic analysis indicates the cross section of tightness of the leather. Differential scanning calorimetric analysis shows that the T _d of leather is more than that of vegetable tanned or equal to aldehyde tanned one. The leathers exhibited fullness, softness, good color, and general appearance when compared to non-oxidized vegetable tannin. The developed process benefits from significant reduction in total solids and better biodegradability in the effluent, compared to non-oxidized vegetable tannins.     

Haematological and biochemical effects of polyphenolics in animal models

Polyphenols of natural and synthetic origin are exploited in tanning sector to convert putrescible skin/hide to non-putrescible leather. However, only 30-40% of the inputs have been taken up for processing, the remaining is released as unspent. The existing conventional wastewater treatment systems are inefficient in removing or degrading these unspent polyphenols and thus detrimental to ecosystem. The present study demonstrates the evaluation of impact of both synthetic and natural polyphenols on biochemical and haematological properties of blood and serum in animal models. The results reveal that concentrations of polyphenols play a major role. At higher concentrations, irrespective of their nature, there was a marked change in the lipid profile (81% reduction), followed by insignificant change in glucose levels, RBC and WBC counts and other haematological parameters. At lower concentrations, no significant changes in the above said properties were observed.     

Chemical and enzymatic interactions of Direct Black 38 and Direct Brown 1 on release of carcinogenic amines

Release of amine products from azo compounds is of considerable interest, since most of the metabolized amine products have toxic and carcinogenic characters. Moreover, most of the azo dyes are extensively used as coloring agents in inks, textiles, leathers, food and pharmaceutical industries. The present study emphasis on the quantification and comparison of amines released from water soluble dyes by (i) extra cellular protein (ECP) of Streptomyces sp. SS07 and by (ii) chemical methods. It has been observed that both the methods release considerable quantities of similar type of amine products. Release of amine compounds by ECP and chemical reduction in acid and alkaline sweat medium from a leather garment sample was also assessed. ECP (0.7852 mg protein/mg of ECP) releases benzidine and 4-amino biphenyl from Direct Black 38 and Direct Brown 1 as stable products at pH 9.2 and at 37 degrees C for a contact period of 24 h. On comparison with chemical reduction, it was observed that about 5-20% increase in the release of amine products by ECP was observed. However, more than 60% of amine products were released by chemical method from leather garment samples than direct treatment with ECP.     

制革废水中丙烯酸类鞣剂的膜分离特征

针对3种丙烯酸类鞣剂超滤(UF)、反渗透(RO)分离参数进行了实验研究,探索其在废水深度处理中膜去除的可行性,研究结果表明,3种鞣剂在分离参数:浓度为200 mg/L,超滤的操作压力(P UF)为0.11 MPa,反渗透的操作压力(P RO)为0.4 MPa的条件下UF-RO分离,效果最好。其次,丙烯酸类鞣剂对膜通量影响较大,导致产生的清液较少,所以用UF、RO处理含有这类物质的制革废水时,应尽可能对废水进行预处理。最后,丙烯酸类鞣剂分子中含有极性较强的基团时,粒径分离效果不同。     

Influence of residual carbon on the decomposition process of PCDD/Fs in MSWI fly ash

In heating treatment of fly ash to reduce PCDD/Fs, cooling process is important to inhibit de novo formation of PCDD/Fs. In this study, assuming that residual carbon is the dominant factor of de novo synthesis, the relation between PCDD/Fs and residual carbon was examined. Firstly, by using MSWI fly ash which was treated in an actually operated facility, both the content of PCDD/Fs and residual carbon were decreased as heating temperature increased. At temperatures higher than 400 degrees C, the reduction rate of residual carbon was higher than 20% and more than 95% of PCDD/Fs was decomposed. In order to simulate a heating treatment process, fly ash was heated at different temperatures and gas atmospheres, oxygen or nitrogen. Heated fly ash was placed for 2 h at 300 degrees C in oxygen to promote de novo synthesis, or cooled immediately. As a result, good correlation between PCDD/Fs and residual carbon was found, therefore it was shown experimentally that residual carbon was the main factor for PCDD/Fs formation by de novo synthesis in fly ash.     

铬渣制取铬黄淋滤液中过量铅离子的去除研究

用累托石做吸附剂来处理铬渣淋滤液制铬黄过程中产生的过量Pb^2-。当pH为5．6～7．3,反应时间90min,吸附剂与水量比为24g／L.pbe^2 浓度由2．5mg／L降到0．05mg／L,Pb^2 的去除率最高可达98％,外排废水符合GB8978—1996一级标准。     

Ecofriendly lime and sulfide free enzymatic dehairing of skins and hides using a bacterial alkaline protease

The ever-increasing attention to the environmental impact of leather industry has necessitated the development of enzyme-based processes as potent alternatives to pollution causing chemicals. In this study, a hair saving process is developed for dehairing of skins and hides using a bacterial alkaline protease preparation, completely eliminating the use of lime and sulfide. To evaluate the efficacy of the enzymatic process, comparative studies have been carried out with two controls; a conventional lime-sulfide process and enzyme-assisted process using commercial dehairing enzyme with reduced quantities of lime and sulfide. The developed process requires a shorter duration of 6h for complete dehairing of skins and hides than control groups and also, it avoids the use of silicate carriers since the enzymatic dehairing is carried out by dip method. Histological and scanning electron microscopic analyses of the dehaired pelts obtained from enzymatic process reveal complete removal of hair and epidermis with moderate opening up of fiber structure in both dermis and corium. Moreover, the collagen is not damaged and resulting in a leather of good quality. The developed process has resulted in a remarkable reduction of effluent load in terms of biochemical oxygen demand, chemical oxygen demand, total dissolved solids and total suspended solids. Physicochemical studies conclusively show that the leathers produced by enzymatic process are equivalent to or better than that obtained by control systems. Thus, the developed enzymatic process offers immense potential for greener mode of dehairing of skins and hides in leather industry coupled with environmental excellence.     

Trace elements in biodeposits and sediments from mussel culture in the Ria de Arousa (Galicia, NW Spain)

The trace elements present at highest concentrations were Cr and Zn, which probably originated from the dumping of effluent from a tanning factory. High proportions of these two elements were associated with the residual fraction. Biodeposits and sediments showed high concentrations of Cd and Pb in the reactive fraction, with a high proportion of the concentration in the reactive fraction being associated with carbonates. Nickel showed a higher degree of pyritization than the previous elements, although most of the Ni was associated with the residual and reactive fractions. Arsenic, Hg and Cu showed high degrees of pyritization, particularly below a depth of 5 cm. The results demonstrate that those elements with a high degree of pyritization may be released into the water through oxidation of the metal sulphides that they form when in suspension in oxic sea water, with the subsequent risk of increased bioavailability to benthic fauna.     

Combined chemical treatment of pharmaceutical effluents from medical ointment production

Three wastewater samples from a pharmaceutical plant formulating medical ointments were subjected to lab-scale treatment by a Fenton-like system in combination with lime coagulation. All samples were plant pre-treated by adsorption/flocculation/filtration processes with utilization of bentonite, but the quality of effluents did not comply with the regulations for wastewater discharged to local sewerage. The optimization of Fenton-like oxidation demonstrated the highest process efficacy at H(2)O(2)/COD weight ratio of 2:1, H(2)O(2)/Fe(2+) molar ratio of 10:1 and 2h of treatment time. The fast pH decrease to acidic values approximately 3 during first min of oxidation for all effluents suggested that pH adjustment was unnecessary. Combination of Fe(III) precipitation and lime coagulation proved feasible to improve considerably COD and residual iron concentration reduction in pharmaceutical effluents. Additionally, considerable BOD(7) reduction and BOD(7)/COD ratio improvement of pharmaceutical wastewater samples was achieved by combined treatment. The application of Fenton-like oxidation with subsequent iron (III)/lime coagulation did not only enhance the quality of pharmaceutical effluents with different chemical characteristics and help to meet the requirements for wastewater discharged to sewage, but also improve the biodegradability of pharmaceutical effluents.     

制革厂铬鞣废水中铬的回收处理研究

针对制革厂铬鞣废水含铬(Cr3 )量高、成分复杂、沉淀后铬泥纯度低的问题,本实验采用优化后的直接加碱沉淀法、絮凝后再加碱沉淀法和新型的硅铁电极法来回收铬鞣废水中的铬.3种方法所得铬泥的纯度分别在36%、65%和80%以上,比原铬泥纯度(27.7%)最多提高了近2倍.     

Through-electromigration: a new method of investigating pore connectivity and obtaining formation factors

The retardation of radionuclides and other contaminants in fractured crystalline rock is strongly associated with the diffusive properties of the rock matrix. At present, the scientific community is divided concerning the question of long-range pore connectivity in intrusive igneous rock. This paper presents a fast new method, called the through-electromigration method, of obtaining formation factors and investigating pore connectivity. The method involves the migration of an ionic tracer through a rock sample with an electrical potential gradient as the main driving force. The method is analogous to the through-diffusion method but the experimental time is reduced by orders of magnitude. This enables investigations of pore connectivity, as measurements can be made on longer samples. In a preliminary investigation, the new method is compared to the traditional through-diffusion method as well as to rock resistivity methods. The diffusive properties of nine granitic rock samples from Laxemar in Sweden, ranging from 15 to 121 mm in length, have been investigated and the results are compared.     

The role of mechanical and biological treatment in reducing methane emissions from landfill disposal of municipal solid waste in the United Kingdom

In Europe, the European Union Landfill Directive aims to reduce the negative environmental impacts of landfilling. This is mainly to be achieved by reducing the quantity of organic matter deposited, through measures such as the separate collection and recycling of the organic waste stream or pretreatment of residual wastes before landfilling. Other than incineration or other thermal processes, mechanical biological treatment is playing an increasingly important role. This study was conducted to seek the benefits of municipal solid waste (MSW) pretreatment, as well as the differences in methane production from the landfilling of untreated and mechanically/biologically treated (MBT) MSW using GasSim simulation. Results demonstrated that methane production rates vary significantly among waste fractions. Those that contribute most to methane generation (organic material and potentially reusable or recyclable material) could be targeted and treated before landfilling. The statistic relationship from the first phase of the study indicated that to match the increasingly stringent landfill waste organic content allowance, local councils should prioritize the reduction/sorting of certain targeted fractions, such as paper, card, green waste, and other putrescibles from MSW. Moreover, mechanical treatment alone produces organic-rich waste called mechanically sorted organic residues (MSORs), which can be viewed as an organic content concentration process. Mechanically and biologically pretreated waste, on the other hand, differs significantly from untreated MSW and MSORs. This work demonstrated that if efficient mechanical-biological treatment is used, considerable reductions in biological activity, landfill gas production, and energy content/total organic carbon could be achieved. Using GasSim, reductions in methane production of >74% have been simulated if a 90% organic content reduction can be achieved during biological treatment on MSORs. A 50-60% organic content reduction by following biological treatment can turn MSOR properties only into normal MSW equivalent though considerably less volume.     

Treatability of nonylphenol ethoxylate surfactants in on-site wastewater disposal systems.

The fate of nine-mole nonylphenol ethoxylate (NPE9) discharged to an on-site wastewater disposal (septic) system was the focus of a 2-year investigation. Known amounts of NPE9-based detergent were metered daily into the plumbing at a single-family household. The ethoxylate-containing wastewater was discharged to the highly anoxic environment of a 4500-L septic tank before distribution to the oxic subsurface via 100 m of leach line. After 180 days of injecting detergent to the septic system, periodic soil pore water and/or groundwater samples were collected and analyzed for nonylphenol ethoxylates (NPEs), nonylphenol ether carboxylates, and nonylphenol. The NPE9 and degradation intermediates that were measured were reduced by 99.99% on a molar basis. An 18% reduction in molar concentration within the septic tank was observed. This was followed by a further 96.7% reduction of molar concentration within the leach lines. As the pore water migrated through the vadose zone, an additional 99.69% reduction in molar concentration was measured between the bottom of the leach lines (leach line effluent) and the lowest vadose zone monitoring location. The results obtained from these analyses indicate that degradation of the surfactant occurs within the anoxic portion of the disposal system with continued rapid biodegradation in the oxic unsaturated zone. Only trace amounts of degradation residuals were detected in soil pore water. The concentration and distribution of various degradation intermediates with respect to location, time, and ambient physical conditions were evaluated. Rapid and systematic degradation of NPE in on-site wastewater disposal systems was documented.     

Transport and fate of organic wastes in groundwater at the Stringfellow hazardous waste disposal site, southern California

In January 1999, wastewater influent and effluent from the pretreatment plant at the Stringfellow hazardous waste disposal site were sampled along with groundwater at six locations along the groundwater contaminant plume. The objectives of this sampling and study were to identify at the compound class level the unidentified 40-60% of wastewater organic contaminants, and to determine what organic compound classes were being removed by the wastewater pretreatment plant, and what organic compound classes persisted during subsurface waste migration. The unidentified organic wastes are primarily chlorinated aromatic sulfonic acids derived from wastes from DDT manufacture. Trace amounts of EDTA and NTA organic complexing agents were discovered along with carboxylate metabolites of the common alkylphenolpolyethoxylate plasticizers and nonionic surfactants. The wastewater pretreatment plant removed most of the aromatic chlorinated sulfonic acids that have hydrophobic neutral properties, but the p-chlorobenzene-sulfonic acid which is the primary waste constituent passed through the pretreatment plant and was discharged in the treated wastewaters transported to an industrial sewer. During migration in groundwater, p-chlorobenzenesulfonic acid is removed by natural remediation processes. Wastewater organic contaminants have decreased 3- to 45-fold in the groundwater from 1985 to 1999 as a result of site remediation and natural remediation processes. The chlorinated aromatic sulfonic acids with hydrophobic neutral properties persist and have migrated into groundwater that underlies the adjacent residential community.     

Pretreatment of automobile shredder residue (ASR) for fuel utilization

Automobile shredder residue (ASR) was pretreated to improve its quality for fuel utilization. Composition analysis revealed that ASR components could be classified into four groups: (1) urethane and textile-light fraction and combustibles containing low levels of ash and Cl; (2) plastics and rubber-light or heavy fraction and combustibles containing high levels of Cl; (3) metals and electrical wire-heavy fraction and incombustibles, and (4) particles smaller than 5.6mm with high ash contents. Based on these results, we successively performed sieving to remove particles smaller than 5.6mm, float and sink separations to reject the heavy fraction and plastics and rubber containing Cl, thermal treatment under an inert atmosphere to remove Cl derived from PVC, and char washing to remove soluble chlorides. This series of pretreatments enabled the removal of 78% of the ash and 91% of the Cl from ASR. Sieving using a 5.6-mm mesh removed a considerable amount of ash. Product quality was markedly improved after the float and sink method. Specifically, the sink process using a 1.1 g cm(-3) medium fluid rejected almost all rubber containing Cl and a large amount of PVC. The remaining Cl in char, after heating at 300 degrees C under an inert atmosphere and washing, was considered to be present as insoluble chlorides that volatilized at temperatures above 300 degrees C. Based on a tradeoff relationship between product quality and treatment cost, ASR may be utilized as a form of refuse plastic fuel or char.     

Dispersion from courtyards and other enclosed spaces

The paper describes small scale wind tunnel experiments on the dispersion of contaminants discharged from the bottom of courtyards and other enclosed spaces. The experiments covered a range of courtyards with ratios of depth to width from 5 (consistent with light wells and other very deep cavities) down to 0.1 (consistent with shallow enclosed squares and piazzas that are frequently found in the urban environment). A variety of parameters within these shapes were investigated, including the depth of the walls around the courtyard, the presence of openings in the walls, the effects of wind direction, the presence of surface clutter and stratification of the air in the courtyard. In general courtyards are poorly ventilating spaces and high residual concentrations of any discharged contaminant occur. However, this behaviour may also be used to advantage in using courtyards as a method of modifying the local climate. The effects of the parameters investigated on contaminant concentrations were complex and quite variable, which allows for the possibility of designing courtyards to suit specific needs.     

MBBR-SA工艺处理模拟大豆深加工废水厌氧出水及污泥减量化

针对大豆深加工高浓度有机废水厌氧出水的特点,采用移动床生物膜反应器-沉淀池-厌氧池(MBBR-SA)工艺进行处理,重点考察了其COD去除、脱氮以及污泥减量化的性能。处理前厌氧出水水质参数为COD 1 350～1 851 mg/L、TN 45～73 mg/L和TP 35～55 mg/L。结果表明,经过70 d的运行,在最佳水力停留时间(HRT)1.68 d与最佳回流比0.75条件下,出水平均COD、TN和NH4+-N浓度分别为91.5、12.4和11.4 mg/L,分别达到了《城镇污水处理厂污染物排放标准》二级标准、二级标准和一级B标准,其平均去除率分别为96.0%、87.4%和88.3%;该工艺未排放剩余污泥,其表观污泥产率为0.13,比MBBR降低了43.5%,具有明显的污泥减量化特性。