Stabilization of Heavy Metal Containing Hazardous Wastes with Byproducts from Advanced Clean Coal Technology Systems

ABSTRACT

The purpose of this investigation was to evaluate the success of residues from advanced Clean Coal Technology (CCT) systems as stabilization agents for heavy metal containing hazardous wastes. In the context examined here, stabilization refers to techniques that reduce the toxicity of a waste by converting the hazardous constituents to a less soluble, mobile, or toxic form.¹ Three advanced CCT byproducts were used: coal waste-fired circulating fluidized bed combustor residue, pressurized fluidized bed combustor residue, and spray drier residue. Seven metal-laden hazardous wastes were treated: three contaminated soils, two air pollution control dusts, wastewater treatment plant sludge, and sandblast waste. Each of the seven hazardous wastes was treated with each of the three CCT byproducts at dosages of 10, 30, and 50% by weight (byproduct:waste). The treatment effectiveness of each mixture was evaluated by the Toxicity Characteristic Leaching Procedure. Of the 63 mixtures evaluated, 21 produced non-hazardous residues. Treatment effectiveness can likely be attributed to mechanisms such as precipitation and encapsulation due to the formation of hydrated calcium silicates and calcium sulfo-alu-minates. Results indicate that these residues have potential beneficial uses to the hazardous waste treatment community, possibly substituting for costly treatment chemicals.     

Anaerobic digestion of thermal-alkaline–pretreated cephalosporin bacterial residues for methane production

Optimum anaerobic conditions of cephalosporin bacterial residues after thermal-alkaline pretreatment were determined by orthogonal experiments. And through biochemical methane potential tests (BMPs) for cephalosporin bacterial residues, the ability for bacterial degradation of cephalosporin was also evaluated. The thermal-alkaline pretreatment with the optimum values of 6% NaOH at 105 °C for 15 min significantly improved digestion performance. With the thermal-alkaline pretreatment, the specific methane yield of the pretreated cephalosporin bacterial residue increased by 254.79% compared with that of the un-pretreated cephalosporin bacterial residue. The results showed that anaerobic digestion of thermal-alkaline–pretreated cephalosporin bacterial residues could be one of the options for efficient methane production and waste treatment.

Implications: This work investigates the thermal-alkaline pretreatment of cephalosporin bacterial residues, which can increase their methane yield by 254.79% compared with no pretreatment. The digestion performance is significantly improved under the condition of 6% NaOH at 105 °C for 15 min. The results show that anaerobic digestion of thermal-alkaline–pretreated cephalosporin bacterial residues could be one of the options for efficient methane production and waste treatment.     

Stabilization of APC residues from waste incineration with ferrous sulfate on a semi-industrial scale

A stabilization method for air pollution control (APC) residues from municipal solid waste incineration (MSWI) involving mixing of the residue with water and FeSO4 has been demonstrated on a semi-industrial scale on three types of APC residues: a semidry (SD) APC residue, a fly ash (FA), and an FA mixed with sludge (FAS) from a wet flue gas cleaning system. The process was performed in batches of 165-175 kg residue. It generates a wastewater that is highly saline but has a low content of heavy metals such as Cd, Cr, and Pb. The stabilized and raw residues have been subject to a range of leaching tests: the batch leaching test, the pH-static leaching test, the availability test, and the column test. These tests showed that the stabilized residues have remarkably improved leaching properties, especially with respect to Pb but also with respect to Cd, Cu, and Zn. The release of Pb was reduced by a factor of 250-36,000.     

Screening of antibiotic residues in fresh milk of Kathmandu Valley,Nepal

The prevalence of two groups of antibiotics; namely penicillin and sulfonamides was studied in fresh milk available in Kathmandu Valley of Nepal. The milk samples (n = 140) were collected from three different sources; individual farmers, cottage dairies and organized dairies of Kathmandu valley. Qualitative and semi-quantitative analysis with rapid screening kits revealed that 23% samples were positive for antibiotic residues in the fresh milk for penicillin and sulfonamide groups (1–256 µg/kg). High performance liquid chromatography (HPLC) analyses detected 81% samples positive for amoxicillin (68–802 µg/kg), 41% for sulfadimethoxine (31–69 µg/kg), 27% for penicillin G (13–353 µg/kg), and 12% for ampicillin (0.5–92 µg/kg). Due to the precision and accuracy of liquid chromatography method, it detected more positive samples and consequently presented higher prevalence than the rapid screening kits. The antibiotic residues were found above the maximum residue limits that presented serious threat to consumer health and raised a serious concern regarding the implementation and monitoring of international regulations in developing countries.     

Stabilization of APC Residues from Waste Incineration with Ferrous Sulfate on a Semi-Industrial Scale

Abstract

A stabilization method for air pollution control (APC) residues from municipal solid waste incineration (MSWI) involving mixing of the residue with water and FeSO₄ has been demonstrated on a semi-industrial scale on three types of APC residues: a semidry (SD) APC residue, a fly ash (FA), and an FA mixed with sludge (FAS) from a wet flue gas cleaning system. The process was performed in batches of 165-175 kg residue. It generates a wastewater that is highly saline but has a low content of heavy metals such as Cd, Cr, and Pb. The stabilized and raw residues have been subject to a range of leaching tests: the batch leaching test, the pH-static leaching test, the availability test, and the column test. These tests showed that the stabilized residues have remarkably improved leaching properties, especially with respect to Pb but also with respect to Cd, Cu, and Zn. The release of Pb was reduced by a factor of 250-36,000.     

The calcination process in a system for washing, calcinating, and converting treated municipal solid waste incinerator fly ash into raw material for the cement industry

Calcination is the second step in a washing-calcination-conversion system in which treated municipal solid waste incinerator fly ash and bottom ash can be reused as raw material in the cement industry and can decompose or stabilize hazardous compounds, reduce residue amounts, and alter residue characteristics. In this research, only fly ash is discussed. Chloride reduction is important if treated fly ash is to be reused in cement; however, the relationship between washed fly ash properties and chloride reduction by calcination is not well understood. This study used washed residues of three types of fly ash-raw fly ash (RFA) from the boiler or economizer of an incineration system, fly ash collected in a bag filter injected with calcium hydroxide (Ca(OH)2) for acid removal (CaFA), and fly ash collected in a bag filter injected with sodium bicarbonate (NaHCO3) for acid removal (NaFA)-in calcination experiments with varying temperature (400-1100 degrees C) and atmosphere (100% nitrogen [N2] at 25 mL/min or 10% oxygen [O2] [90% N2] at fluxes of 25, 50, and 75 mL/min). From the perspective of chloride reduction, heating to 1000 degrees C with 1-hr heating time, 1-hr holding time, and an atmosphere of 10% O2/90% N2 was most suitable for calcination. Under these conditions, chloride levels were reduced by 91, 52, and 96% in washed residues of RFA, CaFA, and NaFA, respectively. Among the washed residues, the weight of the washed residue of NaFA decreased the most.     

Insecticide residues in the blood serum and domestic water source of cacao farmers in Southwestern Nigeria

The blood serum of cacao farmers and their domestic water sources were analyzed for insecticide residues in selected cacao growing communities of Southwestern Nigeria. The farmers were grouped into five exposure periods based on their years of involvement in insecticide application, viz, <5 years, 5-9 years, 10-14 years, 15-19 years and >20 years. The residue analyses revealed that 42 out of the 76 farmers had residues of diazinon, endosulfan, propoxur and lindane in their blood; and 47.6% out of these farmers belonged in the >20 years exposure duration period. About 34% of the farmers had diazinon with a mean concentration of 0.067 mg kg(-1), 29% endosulfan (mean=0.033 mg kg(-1)), 23% propoxur (mean=0.095 mg kg(-1)), and 17% lindane (mean=0.080 mg kg(-1)) in their blood. The residues of lindane, endosulfan and propoxur in all the exposure duration categories were found to be far below the no observable adverse effect level (NOAEL) while diazinon residues detected in the blood serum of the farmers in all the exposure duration categories exceeded the NOAEL of 0.02 mg kg(-1) for the insecticide. The study also revealed that the sources of drinking water had been contaminated with dazinon and propoxur in some of the farmers' localities; and the concentrations of the insecticides exceeded the acceptable daily intake (ADI). It is concluded that cacao farmers in Southwestern Nigeria may have been occupationally exposed due to insecticide application for mirid control in their cacao plantations; and the exposure at times is of such magnitude as to be hazardous to the farmers and their respective communities.     

Experimental approaches and analytical techniques for determining organic compound bound residues in soil and sediment

Research has shown that many chemicals form persistent and permanently bound residues in soils and sediments that play an important role in soil and sediment detoxification processes, long-term compound partitioning behaviour and compound bioavailability and toxicity in soil and sediment. This article reviews the methodological approaches that have been applied to determine the nature of bound residues in soil and sediment, the application of specific analytical techniques, the type of information they generate, and their relative advantages and disadvantages. It begins by defining bound residues and discussing soil-compound interactions. The application of model compound studies for elucidating specific binding interactions is reviewed along with long-term laboratory and field soil incubation experiments. The use of radiolabelled compounds, isotopically labelled compounds and combinations of both in these experiments are outlined by examples from the literature, along with sequential extraction schemes for releasing bound residues from soil, sediment and humic materials. The importance of spectroscopic methods, and particularly nuclear magnetic resonance techniques for characterising the structure of bound residues in soil and sedimentary humic substances is discussed and illustrated by examples from the literature on the subject. The process of bound residue formation is highly complex and requires further research to establish the mechanisms of bound residue formation and their subsequent environmental and toxicological fate. Much of the uncertainty regarding the elucidation of bound residue formation arises from our poor understanding of the structure of soil and sedimentary organic matter. Significant advances in our understanding of the formation and fate of bound residues will be made when we develop a deeper insight into the complex and heterogeneous structure of soil and sedimentary organic matter.     

Error propagation in pesticide residue measurements estimated by computational simulations and inter-laboratory sample analysis

An assessment of the error associated with conventional pesticide residue analysis has been conducted based on computer simulations and inter-laboratory residue analysis. Computational simulations were conducted based on (i) typical performance and regulatory acceptance criteria of analytical methods, and (ii) field residue distributions. In addition, field samples with incurred residues were sent to different private laboratories and the results compared. The relative difference in pesticide residues obtained when samples from the same field or produce lot are analyzed at separate laboratories was used to quantify the uncertainty associated with residue analyses performed using common analytical technology, and methods that are in compliance with current regulatory requirements. The study showed that differences of > 100% are common and should be expected when samples from the same crop are analyzed at different laboratories. The results also suggest that the error within residue measurements can be particularly detrimental when a result is reported near the maximum residue limit (MRL).     

Nature of the field-to-field distribution of pesticide residues

The supervised trial datasets (1950), consisting of a minimum of five residue values and selected by the experts of FAO/WHO Joint Meeting on Pesticide Residues for recommending maximum residue levels between 1997 and 2011, were evaluated to obtain information on the typical spread of residue values in individual datasets. The typical relative standard deviation, CV, of field-to-field variation of pesticide residues was about 80%. The spread of residues in datasets is independent from the chemical structure of pesticides, residue level, pre-harvest interval and number of values in the datasets. The CV ranges within the Codex commodity groups and between groups overlapped and their difference were not statistically significant. The number of residues below the limit of quantification (LOQ) affects the CV at various extents depending on the ratio of LOQ/R _mean. The combined uncertainty of the highest residue in a dataset significantly affects the CV of the dataset. The lowest and intermediate ones have less influence. The residues in different fields receiving the same treatment vary within large range: 55%, 72%, 78%, 86% and 89% of the 25,766 residues values were, respectively, within 3, 4, 5, 6 and 7 times the median value of the corresponding dataset.     

Synthesis of novel hapten and production of generic monoclonal antibody for immunoassay of penicillins residues in milk

The objective of this study was to produce a generic monoclonal antibody for determination of penicillins residues in milk. The compound 6-aminopenicillanic acid was used as the template to synthesize two novel generic haptens that were used to produce the monoclonal antibodies. The obtained monoclonal antibodies simultaneously recognized 11 penicillin drugs (amoxicillin, ampicillin, penicillin G, penicillin V, sulbenicillin, carbencillin, methicillin, cloxacillin, dicloxacillin, oxacillin, and nafcillin). After evaluation of different reagent combinations, a heterologous indirect competitive enzyme immunoassay was developed to multi-determine the 11 drugs in milk. The crossreactivities to the 11 drugs were in a range of 16%–117% and the limits of detection were in a range of 0.7–9.3 ng/mL depending on the drug. The recoveries from the fortified blank milk were in a range of 77.6%–99.4% with coefficients of variation lower than 13.5%. This method could be used as a rapid screen tool for routine monitoring the residues of the 11 penicillin drugs in animal derived foods.     

Solubility analysis and disposal options of combustion residues from plants grown on contaminated mining area

Biomass, as a renewable energy source, is an excellent alternative for the partial replacement of fossil fuels in thermal and electric energy production. A new fuel type as biomass for energy utilisation includes ligneous plants with considerable heavy metal content. The combustion process must be controlled during the firing of significant quantities of contaminated biomass grown on brownfield lands. By implementing these measures, air pollution and further soil contamination caused by the disposal of the solid burning residue, the ash, can be prevented. For the test samples from ligneous plants grown on heavy metal-contaminated fields, an ore mine (already closed for 25 years) was chosen. With our focus on the determination of the heavy metal content, we have examined the composition of the soil, the biomass and the combustion by-products (ash, fly ash). Our results confirm that ash resulting from the combustion must be treated as toxic waste and its deposition must take place on hazardous waste disposal sites. Biomass of these characteristics can be burnt in special combustion facility that was equipped with means for the disposal of solid burning residues as well as air pollutants.     

Long-term residue of DDT compounds in forest soils in Maine

Soils in forests sprayed aerially with DDT in 1958-1967 have been sampled for persistence of residues at intervals since then and most recently in 1993. Results of all the samples are presented and show persistence through 30 years, with evidence of decline of residue only in the third decade. The metabolites of DDT--DDE and DDD--increased over time, each comprising about a third of total residue in 1993. Residue continues to be held in the organic mat with little evidence of movement downward to the inorganic soil horizons.     

Persistent organochlorine residues in northern fur seal from the Pacific coast of Japan since 1971

The present study was conducted to determine the residue levels of persistent organochlorines such as PCB homologues, DDT and its metabolites, and HCH isomers in the ventral blubber of female northern fur seal (Callorhinus ursinus) collected off Sanriku, the Pacific coast of northern Japan, since 1971. Among the organochlorines examined, the concentrations of PCBs and DDTs were found to be high in all samples. The residue levels of these two contaminants showed a drastic reduction following maturity and then a slight increase after the retirement from pregnancy/menopause. Temporal variation of PCB and DDT residues showed maximum levels around 1976 and then decreased, whereas HCH residue levels revealed a very slow declining pattern. Considering the concentrations and compositions of the residues, the northern fur seal is likely to be exposed to organochlorine contamination deriving from global terms. In this context, continuous contamination has been foreseen with regard to PCB and HCH residues. The pattern of organochlorine residues indicated that the northern fur seal has higher metabolic capacity than Dall's porpoise, while it is comparable to those of larga seal and Steller sea lion.     

Formation and long-term fate of non-extractable residues in outdoor lysimeter studies

Long-term outdoor lysimeter studies using (14)C-labelled compounds allow the quantification of the 'non-extractable residue fraction'. More than 20 lysimeter studies under realistic environmental conditions showed that more than 80% of residual carbon of the molecule is retained in the topsoil layer even after several years. Generally, 50-90% of this residual radiocarbon is regarded as 'soil bound residue'. Microbial biomass is present in large quantities in topsoil and continuously influences chemical and biochemical alteration of pesticide molecules that may interact directly with the total soil organic matter. Labelling techniques using radioactive isotopes like (14)C have been used to characterize these residues in the humus matrix. Our studies have been directed to the investigation of extractability and/or bioavailability of these residues in long-term investigations.     

Measurement of transferable chemical residue from nylon carpet using the California roller and a new mega-California roller

Human chemical exposures resulting from transfer of surface deposition on indoor nylon carpets may be estimated by measuring transferable residues (mu g chemical/cm2 carpet). A weighted roller developed at California Department of Food and Agriculture (CDFA) has been extensively used to sample transferable residue for estimates of human exposure in risk characterization. A modified roller has been developed to evaluate the influence of pressure on transferable chemical residue since weight and force (or pressure, kg/m2) may vary person-to-person and activity-to-activity. A 30.5 cm diameter roller was used to apply 60 to 2100 kg/m2 to bracket pressures exerted by humans on a flat nylon-carpeted surface. Measurements of transferable cyfluthrin residues were made after 1, 7, and 21 days. Total Soxhlet extractable cyfluthrin residues were relatively constant during the test period. Residue transferability decreased during the study period. Modest increases in the transferability of surface residues were observed over the broad range of pressures applied by the modified roller.     

Pesticide pollution remains severe after cleanup of a stockpile of obsolete pesticides at Vikuge, Tanzania

High levels of DDT residues and hexachlorocyclohexanes (HCHs) were found in soil, well water, and surface water around a collapsed pesticide storage shed at Vikuge Farm, Tanzania. Residues of DDT and HCHs were found at three soil depths down to 50 cm. Surface soil samples contained up to 28% total DDT and 6% total HCH residues. Water samples had concentrations of up to 30 microg L(-1) of organochlorine pesticides. Other compounds detected were aldrin, azinphos-methyl, carbosulfan, gamma-chlordane, chlorprofam, heptachlor, hexazinone, metamitron, metazachlor, pendimethalin, and thiabendazole. Although the visible remains of pesticides have been removed, the remaining soil is itself hazardous waste and poses a risk to the environment and the inhabitants of the surrounding villages. These findings show the necessity to follow up the environmental situation at former storage sites of obsolete stocks of pesticides, and that the environmental problems are not necessarily solved by removing the visible remains.     

Persistence and distribution of pesticide residues in fresh agricultural food consumed in the province of Bologna

The presence of pesticide residues in fresh vegetables and fruit have been qualitatively and quantitatively determined at the laboratories of the Regional Agency for Environmental Protection (ARPA), Division of the Province of Bologna. More than 1,700 samples have been tested by routine analyses. The possible risks for consumers have been evaluated by various parameters. The most important ones were: the amount of each residue; the respective ADI (Acceptable Daily Intake) limit; the contemporary presence of different residues; an estimation of the daily intake, based on the amount of fruit and vegetables consumed per person. It has been possible to evaluate that the daily intake of pesticide residues in the province of Bologna during the period 2003–06 resulted lower than the ADI limits concerning the vegetables. According to the information on fruit consumption the daily intake of omethoate (O,O-dimethyl S-methylcarbamoylmethyl phosphorothioate) resulted higher than its ADI limit, of dicofol (2,2,2-trichloro-1,1-bis(trichloromethyl)benzenemethanol) very close to the admitted limit, under the respective limits for all the other residues.     

Endosulfan in China 2—emissions and residues

Background, aim, and scope  Endosulfan is one of the organochlorine pesticides (OCPs) and also a candidate to be included in a group of new persistent organic pollutants (UNEP 2007). The first national endosulfan usage inventories in China with 1/4° longitude by 1/6° latitude resolution has been reported in an accompanying paper. In the second part of the paper, we compiled the gridded historical emissions and soil residues of endosulfan in China from the usage inventories. Based on the residue/emission data, gridded concentrations of endosulfan in Chinese soil and air have been calculated. These inventories will provide valuable data for the further study of endosulfan. Methods  Emission and residue of endosulfan were calculated from endosulfan usage by using a simplified gridded pesticide emission and residue model—SGPERM, which is an integrated modeling system combining mathematical model, database management system, and geographic information system. By using the emission and residue inventories, annual air and soil concentrations of endosulfan in each cell were determined. Results and discussion  Historical gridded emission and residue inventories of α- and β-endosulfan in agricultural soil in China with 1/4° longitude by 1/6° latitude resolution have been created. Total emissions were around 10,800 t, with α-endosulfan at 7,400 t and β-endosulfan at 3,400 t from 1994 to 2004. The highest residues were 140 t for α-endosulfan and 390 t for β-endosulfan, and the lowest residues were 0.7 t for α-endosulfan and 170 t for β-endosulfan in 2004 in Chinese agricultural soil where endosulfan was applied. Based on the emission and residue inventories, concentrations of α- and β-endosulfan in Chinese air and agricultural surface soil were also calculated for each grid cell. We have estimated annual averaged air concentrations and the annual minimum and maximum soil concentrations across China. The real concentrations will be different from season to season. Although our model does not consider the transport of the insecticide in the atmosphere, which could be very important in some areas during some special time, the estimated concentrations of endosulfan in Chinese air and soil derived from the endosulfan emission and residue inventories are in general consistent with the published monitoring data. Conclusions  To our knowledge, this work is the first inventory of this kind for endosulfan published on a national scale. Concentrations of the chemical in Chinese air and agricultural surface soil were calculated for each grid cell. Results show that the estimated concentrations of endosulfan in Chinese air and soil agree reasonably well with the monitoring data in general. Recommendations and perspectives  The gridded endosulfan emission/residue inventories and also the air and soil concentration inventories created in this study will be updated upon availability of new information, including usage and monitoring data. The establishment of these inventories for the OCP is important for both scientific communities and policy makers.     

Removal of endosulfan using aerobic mixed bacterial culture

With the increasing use of pesticides in modern agriculture, increased evidence of their disastrous effects on the environment has been noticed. Pesticides applied in various modes and places contaminate various parts of the environment, including groundwater sources. As pesticide problems are greater in the rural areas, the authors have developed a successful low-cost technology for rural areas with wood charcoal treated with nitric acid. As pesticides are classified as hazardous waste, the sludge resulting from their treatment has to be disposed off safely. This paper describes the removal of pesticides at a higher concentration of 24 mg/l, using a mixed culture of aerobic bacteria, and also a study of the inhibiting action of endosulfan on bacterial cells. It was found that bacteria without acclimatisation could remove 89.7% of endosulfan, and with prior acclimatisation the efficiency was 96%. It was found that removal in the initial phase is because of the hydrophobic nature of endosulfan and its affinity to sediments. The adsorbed endosulfan subsequently undergoes biotransformation, which has been confirmed by monitoring endosulfan concentrations in the bacterial sludge. Transformation was found to be significant in the acclimatised culture system. The fluctuation in bacterial performance was greater at lower concentrations of endosulfan, and overall inhibition was greater at higher concentrations.