CHARACTERIZATION OF URBAN WASTES ACCORDING TO FERTILITY AND PHYTOTOXICITY PARAMETERS

Several urban wastes of different nature and level of organic matter stability (municipal solid wastes, sewage sludges and composts) have been characterized analysing fertility and phytotoxicity parameters. Sewage sludges showed the highest N and P values of all the wastes. The total K content of the wastes was low but almost all was available to plants. Mature composts had the lowest organic carbon and humic substances values as a consequence of organic matter mineralization during the composting process. The soluble C at pH 2/precipitated C ratio decreased as the stability of the organic matter increased. In spite of the heterogeneity of the wastes analysed, the organic matter/total organic C ratio was largely constant with a mean value of 2.05. In no case did the heavy metal levels exceed the maximum allowed by the EU disposition for sewage sludges use in agriculture. The highest levels of phytotoxic substances occurred in the fresh wastes. The germination rates and root length were highest with mature composts. Germination index and root length were negatively correlated with water soluble carbon (WSC) and WSC/N ratio. The principal component analysis showed that extractable C, soluble C at pH 2 and water soluble C were the C fractions which most contributed to the total variability.     

Characterization, Fluxes and Toxicity of Leather Tanning Bath Chemicals in a Large Tanning District Area (IT)

The leather tanning industry is perceived as responsible of a significant consume of natural resources and output of wastes such as high concentration of organics, salts and heavy metals such as chromium, both in solid and liquid form as a result. Now as ever the future of tanneries strongly depends on the increase of their awareness that a sustainable industry for the future means embracing a forward-looking philosophy of the leather making process through optimal resource management within the tannery. This study reports the characterization of some chemicals used in a large tanning district area in terms of COD, BOD, aromaticity (UV₂₈₀) and double bond (UV₂₅₄) absorbance measurements, toxicity on fresh and saline water as well as terrestrial species, GC-MS scanning. The study provides a consistent set of information on tannin-associated concentration-related trends and suggests novel criteria in defining control quality for evaluating environmental impact of leather tanning industry.     

How changing regulations determine biotreatment options for petroleum wastes

Remediation of refinery wastes is regulated by three major federal environmental statutes: the Clean Air Act, the Clean Water Act, and the Resource Conservation and Recovery Act (RCRA); other statutes apply, but to a lesser degree. During the past two years, RCRA's rules have effectively outlawed the passive biological treatment of primary refinery waste sludges in waste ponds and lagoons, even though the law recommends active biological treatment as the second stage in the waste treatment train. RCRA's land disposal restrictions may also outlaw land farming treatment for the bottom sludges involved in crude oil storage. Since 1980, when the U.S. Environmental Protection Agency listed an initial group of five waste streams as hazardous, the agency has listed two more waste streams and twenty-five organic constituents, several found in petroleum wastes. Now it is about to list fourteen more petroleum refining wastes and is studying the addition of fifteen more waste streams. Treatment standards and restrictions have also been promulgated. This article explores the biotreatment techniques and technologies that are still available to petroleum and environmental engineers.     

Bio-processing of solid wastes and secondary resources for metal extraction - A review

Metal containing wastes/byproducts of various industries, used consumer goods, and municipal waste are potential pollutants, if not treated properly. They may also be important secondary resources if processed in eco-friendly manner for secured supply of contained metals/materials. Bio-extraction of metals from such resources with microbes such as bacteria, fungi and archaea is being increasingly explored to meet the twin objectives of resource recycling and pollution mitigation. This review focuses on the bio-processing of solid wastes/byproducts of metallurgical and manufacturing industries, chemical/petrochemical plants, electroplating and tanning units, besides sewage sludge and fly ash of municipal incinerators, electronic wastes (e-wastes/PCBs), used batteries, etc. An assessment has been made to quantify the wastes generated and its compositions, microbes used, metal leaching efficiency etc. Processing of certain effluents and wastewaters comprising of metals is also included in brief. Future directions of research are highlighted.     

Thermal valorization of footwear leather wastes in bubbling fluidized bed combustion

Transformation of hide (animal skins) into leather is a complicated process during which significant amounts of wastes are generated. Footwear is the sector that consumes the major part of leather (60%). Logically, this industry is producing the largest quantity of leather wastes. The objective of this work was to demonstrate the technical feasibility of fluidized bed technology to recover the energy from burning footwear leather wastes. Considering the characteristics of leather waste, especially the heating value (12.5-21 MJ/kg), it can be considered a fairly good fuel. Moreover, leather waste has suitable characteristics for combustion, e.g., high volatile matter (76.5%) and low ash content (5.2%). Two factors deserve special attention: N3O and NOx emissions as a consequence of its unusual high nitrogen content (14.1%) and the chromium speciation because chromium is the main element of ash (3.2%) due to its use in leather tanning. A series of experiments has been carried out in a 0.1 MWt bubbling fluidized bed pilot plant. The combustion efficiency, flue gas composition and chromium speciation were investigated. Despite having high nitrogen content, a low conversion rate of fuel-N to NOx and N2O was attained. Chromium was concentrated in the solid streams and it was consistently found as Cr(III+); no presence of Cr(VI+) was detected.     

国外超临界水氧化法在有机危险废物处理上的应用

介绍了以超临界水为反应介质的超临界水氧化法的特点及其在处理多氯联苯、二恶英等有机危险废物中的应用。     

Valorization of titanium metal wastes as tanning agent used in leather industry

The development of new tanning agents and new technologies in the leather sector is required to cope with the increasingly higher environmental pressure on the current tanning materials and processes such as tanning with chromium salts. In this paper, the use of titanium wastes (cuttings) resulting from the process of obtaining highly pure titanium (ingots), for the synthesis of new tanning agent and tanning bovine hides with new tanning agent, as alternative to tanning with chromium salts are investigated. For this purpose, Ti waste and Ti-based tanning agent were characterized for metal content by inductively coupled plasma mass spectrometry (ICP-MS) and chemical analysis; the tanned leather (wet white leather) was characterized by Scanning Electron Microscope/Energy Dispersive Using X-ray (Analysis). SEM/EDX analysis for metal content; Differential scanning calorimetric (DSC), Micro-Hot-Table and standard shrinkage temperature showing a hydrothermal stability (ranged from 75.3 to 77 °C) and chemical analysis showing the leather is tanned and can be processed through the subsequent mechanical operations (splitting, shaving). On the other hand, an analysis of major minor trace substances from Ti-end waste (especially vanadium content) in new tanning agent and wet white leather (not detected) and residue stream was performed and showed that leachability of vanadium is acceptable. The results obtained show that new tanning agent obtained from Ti end waste can be used for tanning bovine hides, as eco-friendly alternative for chrome tanning.     

Evaluation of metals in the residue of paper sludge after recovery of pulp components using an ionic liquid

The quantity of sludge produced by the paper industry in Japan in 2011 was estimated to be 27.91 million tons wet weight. This amount is the third largest among all industrial wastes. To explore ways of reusing recovered paper pulp and safely disposing of the residue, we investigated the distribution of metals in the process of recovery of pulp from two types of paper sludge using an ionic liquid. 32 and 46 % of pulp from paper sludge A and B was recovered using ionic liquid, respectively; the resultant weight reduction of the solid mass was comparable to that of incineration. There were virtually no heavy metals but aluminum in the recovered pulp, which makes its reuse viable at present. The characteristics of the metals in the residues differed according to the treatment used and properties of the paper sludge. Copper accounted for ~10 % in the ionic liquid used for recovery of pulp from the paper sludges. This suggests that [bmIm]Cl has the potential to dissolve a specific amount of copper compared to other metals.     

Calcium phosphate stabilization of fly ash with chloride extraction

Municipal solid waste incinerator by products include fly ash and air pollution control residues. In order to transform these incinerator wastes into reusable mineral species, soluble alkali chlorides must be separated and toxic trace elements must be stabilized in insoluble form. We show that alkali chlorides can be extracted efficiently in an aqueous extraction step combining a calcium phosphate gel precipitation. In such a process, sodium and potassium chlorides are obtained free from calcium salts, and the trace metal ions are immobilized in the calcium phosphate matrix. Moderate calcination of the chemically treated fly ash leads to the formation of cristalline hydroxylapatite. Fly ash spiked with copper ions and treated by this process shows improved stability of metal ions. Leaching tests with water or EDTA reveal a significant drop in metal ion dissolution. Hydroxylapatite may trap toxic metals and also prevent their evaporation during thermal treatments. Incinerator fly ash together with air pollution control residues, treated by the combined chloride extraction and hydroxylapatite formation process may be considered safe to use as a mineral filler in value added products such as road base or cement blocks.     

The effect of storage and mechanical pretreatment on the biological stability of municipal solid wastes

Modern mechanical–biological waste treatment plants for the stabilization of both the source-separated organic fraction of municipal solid wastes (OFMSW) and the mixed stream of municipal solid wastes (MSW) include a mechanical pretreatment step to separate recyclable materials such as plastics, glass or metals, before biological treatment of the resulting organic material. In this work, the role of storage and mechanical pretreatment steps in the stabilization of organic matter has been studied by means of respiration techniques. Results have shown that a progressive stabilization of organic matter occurs during the pretreatment of the source-separated OFMSW, which is approximately 30% measured by the dynamic respiration index. In the case of mixed MSW, the stabilization occurring during the reception and storage of MSW is compensated by the effect of concentration of organic matter that the pretreatment step provokes on this material. Both results are crucial for the operation of the succeeding biological process. Finally, respiration indices have been shown to be suitable for the monitoring of the pretreatment steps in mechanical–biological waste treatment plants, with a strong positive correlation between the dynamic respiration index and the cumulative respiration index across all samples tested.     

Waste management from pulp and paper production in the European Union

Eleven million tonnes of waste are produced yearly by the European pulp and paper industry, of which 70% originates from the production of deinked recycled paper. Wastes are very diverse in composition and consist of rejects, different types of sludges and ashes in mills having on-site incineration treatment. The production of pulp and paper from virgin pulp generates less waste but the waste has similar properties to waste from the production of deinked pulp, although with less inorganics. Due to legislation and increased taxes, landfills are quickly being eliminated as a final destination for wastes in Europe, and incineration with energy recovery is becoming the main waste recovery method. Other options such as pyrolysis, gasification, land spreading, composting and reuse as building material are being applied, although research is still needed for optimization of the processes. Due to the large volumes of waste generated, the high moisture content of the waste and the changing waste composition as a result of process conditions, recovery methods are usually expensive and their environmental impact is still uncertain. For this reason, it is necessary to continue research on different applications of wastes, while taking into account the environmental and economic factors of these waste treatments.     

Thermal behaviour of chrome shavings and of sludges recovered after digestion of tanned solid wastes with calcium hydroxide

The thermal behaviour of chrome shavings and of sludges recovered after digestion of tanned wastes with Ca(OH)2 was studied. Ashes obtained after incineration of wastes at various temperatures were analysed by X-ray diffraction and EDX method. The main crystallized phases present in the ash obtained at 600 degrees C are Cr2O3 and NaCl. The diffractograms revealed an increase in the intensities of the chromium oxide peaks and a very notable decrease of the amount of sodium chloride at 1100 degrees C. EDX analysis revealed a total disappearance of the chlorine peak at this temperature. Scanning electron micrographs show that the waste lost its fibrous aspect when the temperature increases. Formation of aggregates was noted after 550 degrees C. Combustion of organic matters and decarbonation phenomenon are the main stages observed on GTA and DTA curves of sludges. These phenomena are, respectively, exothermic and endothermic. The diffractogram of sludges recorded at 550 degrees C, in the presence of a constant oxygen surplus, revealed the presence of CaCrO4 and CaCO3.     

Study of the operational conditions for anaerobic digestion of urban solid wastes

This paper describes an experimental evaluation of anaerobic digestion technology as an option for the management of organic solid waste in developing countries. As raw material, a real and heterogeneous organic waste from urban solid wastes was used. In the first experimental phase, seed selection was achieved through an evaluation of three different anaerobic sludges coming from wastewater treatment plants. The methanization potential of these sludges was assessed in three different batch digesters of 500 mL, at two temperature levels. The results showed that by increasing the temperature to 15 degrees C above room temperature, the methane production increases to three times. So, the best results were obtained in the digester fed with a mixed sludge, working at mesophilic conditions (38-40 degrees C). Then, this selected seed was used at the next experimental phase, testing at different digestion times (DT) of 25, 20 and 18 days in a bigger batch digester of 20 L with a reaction volume of 13 L. The conversion rates were registered at the lowest DT (18 days), reaching 44.9 L/kg(-1) of wet wasteday(-1). Moreover, DT also has a strong influence over COD removal, because there is a direct relationship between solids removal inside the reactor and DT.     

Developing incineration process designs and remediation projects from treatability studies

The Bog Creek Farm CERCLA (Superfund) site in Howell Township, New Jersey, was extensively contaminated, allegedly with wastes from paint manufacturing. The site contained two types of incinerable wastes: contaminated soils and sediments. A remedial investigation and feasibility study (RI/FS) was conducted, leading to a recommendation to treat the most contaminated areas by incineration. This recommendation was converted into the selected approach through the Record of Decision (ROD) mechanism. Contaminants at the Bog Creek Farm site included a wide range of volatiles, semivolatiles, and heavy metals. The incineration approach chosen, therefore, had to remove the organics from the soil without creating additional problems associated with heavy metals emissions. In order to evaluate the incineration problem and develop an advisory conceptual design for its solution, Ebasco Services Incorporated performed extensive characterizations of the material. Such characterizations included performing proximate and ultimate analyses and determining other key physical, chemical, and thermodynamic properties of the soils and sludges. Energy and Environmental Research Corporation (EER) then performed treatability studies in its rotary kiln test incinerator. These treatability studies focused upon the rotary kiln, and the environment required for cleaning the soil. They assumed that contaminants in the vapor phase could be destroyed in the afterburner. Tests were conducted at bed temperatures of 1,000°F, 1,460°F, and 1,800°F. Samples were drawn from the kiln at intermediate times. Combustion regimes were therefore constructed for the treatment of Bog Creek Farm wastes, maximizing organic removal while managing the heavy metals problem. Ebasco then converted the results of the incinerability or treatability studies into an advisory conceptual design. This advisory conceptual design called for a kiln temperature of 1,600°F (bed temperature of 1,200°F) and a solids residence time in the kiln of 40 minutes. Additional data indicated that the afterburner could operate at 1,800°F in order to ensure destruction of the POHCs. Combustion chemistry fundamentals demonstrated that the minimum afterburner temperature required was 1,650°F. Ebasco converted this conceptual design into a performance specification to be used in the bid process, under the management of the U.S. Army Corps of Engineers. The remediation was then put out to bid. Chemical Waste Management was the successful bidder. The incineration was successfully completed by August 1990; the system was then demobilized, as the site was remediated.     

Laboratory-scale experiments applied to the design of a two-stage submerged combustion evaporation system

To simulate a submerged combustion evaporation (SCE) process under laboratory conditions, this study conducted three kinds of indirect-heating evaporation experiments, including normal evaporation, vacuum evaporation, and gas-carrying evaporation experiments on mature municipal solid waste (MSW) landfill leachate. The results showed that the organic concentrations in terms of COD in condensates were always very high at the beginning, then decreased rapidly, and stabilized at a low level, which suggests that only the forepart of vapors need to be safely treated to control the discharge of organic pollutants. This study applied the process in developing a two-stage SCE system, which has been implemented for the treatment of biologically pretreated and concentrated leachate from Membrane Bioreactor (MBR) and Reverse Osmosis (RO) combined process in the Beishenshu MSW Landfill, Beijing, China. The result shows that the two-stage SCE system can successfully further concentrate refractory organic matter in concentrated leachate and remove volatile organics from the vapor.     

A multi-criteria assessment of scenarios on thermal processing of infectious hospital wastes: A case study for Central Macedonia

In Greece more than 14,000 tonnes of infectious hospital waste are produced yearly; a significant part of it is still mismanaged. Only one off-site licensed incineration facility for hospital wastes is in operation, with the remaining of the market covered by various hydroclave and autoclave units, whereas numerous problems are still generally encountered regarding waste segregation, collection, transportation and management, as well as often excessive entailed costs. Everyday practices still include dumping the majority of solid hospital waste into household disposal sites and landfills after sterilization, still largely without any preceding recycling and separation steps. Discussed in the present paper are the implemented and future treatment practices of infectious hospital wastes in Central Macedonia; produced quantities are reviewed, actual treatment costs are addressed critically, whereas the overall situation in Greece is discussed. Moreover, thermal treatment processes that could be applied for the treatment of infectious hospital wastes in the region are assessed via the multi-criteria decision method Analytic Hierarchy Process. Furthermore, a sensitivity analysis was performed and the analysis demonstrated that a centralized autoclave or hydroclave plant near Thessaloniki is the best performing option, depending however on the selection and weighing of criteria of the multi-criteria process. Moreover the study found that a common treatment option for the treatment of all infectious hospital wastes produced in the Region of Central Macedonia, could offer cost and environmental benefits. In general the multi-criteria decision method, as well as the conclusions and remarks of this study can be used as a basis for future planning and anticipation of the needs for investments in the area of medical waste management.     

Effect of organic matter and moisture on the calorific value of solid wastes: An update of the Tanner diagram

Objective of the work was to experimentally determine the effect of the organic matter and moisture contents on the calorific value of organic solid wastes. Nine substrates (i.e. newsprint, biodried municipal solid wastes, municipal solid waste derived composts, wastewater sludges, and sea weed derived compost), with organic matter contents that ranged from 12% to 91% (dry weight) were used in the experiments. All substrates were dried and ground and deionized water was artificially added in order to achieve certain target moisture contents per substrate. The higher heating value (HHV) was, then, determined experimentally for each sample using a bomb calorimeter. Best reduced models were developed to describe the higher and lower heating values as a function of organic matter, ash and moisture contents. A triangular plot was constructed and the self-sustained combustion area was determined and compared to that of the Tanner diagram. Response surfaces were drawn to visually assess the effect of organic matter and moisture contents on the calorific value of the wastes.     

Towards a cleaner production in developing countries: a case study in a Chilean tannery.

A Chilean leather tanning industry (tannery) was studied in terms of input/output (I/O) analysis of beamhouse, tanyard and retanning processes. The physical-chemical characterization of 19 streams were investigated. Streams from the beamhouse process and some streams from the retanning process were found to have high organic contents ranging from 2.5 to 18.1 g COD L(-1). The pH ranged between 3.45 and 12.28. Sulphur was found in most of the streams whereas chromium was detected in two wastewaters from the tanyard and in seven streams from the retanning process. Pollution prevention opportunities were evaluated and an appropriate treatment strategy was proposed. The main emphasis was on determining waste reduction measures that can be easily implemented and are not particularly expensive. Measures for reduction at source were proposed to reduce water and chemicals consumption and wastewater pollution. A so-called S(index) strategy was used to evaluate proposals on segregation and specific treatment of the main chromium- and sulphur-containing wastewaters. It was suggested that some streams may be re-used, but it is necessary to apply anaerobic or aerobic treatment first, depending on their organic load. Solid wastes were also evaluated and a proposal for their reduction and disposal was made.     

Characterization of char derived from various types of solid wastes from the standpoint of fuel recovery and pretreatment before landfilling

Carbonization is a kind of pyrolysis process to produce char from organic materials under an inert atmosphere. In this work, chars derived from various solid wastes were characterized from the standpoint of fuel recovery and pretreatment of waste before landfilling. Sixteen kinds of municipal and industrial solid wastes such as residential combustible wastes, non-combustible wastes, bulky wastes, construction and demolition wastes, auto shredder residue, and sludges were carbonized at 500 degrees C for 1h under nitrogen atmosphere. In order to evaluate the quality of char as fuel, proximate analysis and heating value were examined. The composition of raw waste had a significant influence on the quality of produced char. The higher the ratio of woody biomass in waste, the higher heating value of char produced. Moreover, an equation to estimate heating value of char was developed by using the weight fraction of fixed carbon and volatile matter in char. De-ashing and chlorine removal were performed to improve the quality of char. The pulverization and sieving method seems to be effective for separation of incombustibles such as metal rather than ash. Most char met a 0.5 wt% chlorine criterion for utilization as fuel in a shaft blast furnace after it was subjected to repeated water-washing. Carbonization could remove a considerable amount of organic matter from raw waste. In addition, the leaching of heavy metals such as chrome, cadmium, and lead appears to be significantly suppressed by carbonization regardless of the type of raw waste. From these results, carbonization could be considered as a pretreatment method for waste before landfilling, as well as for fuel recovery.