Evaluation of heavy metal content in digestate from batch anaerobic co-digestion of sunflower hulls and poultry manure

In this experimental study, the biogas digestate from mesophilic batch anaerobic co-digestion of poultry manure and an agricultural residue, sunflower hulls, was characterized, particularly in terms of heavy metal content, in order to evaluate whether the biogas digestate was suitable for land applications. Ni, Zn, Cu, Pb, Cr, Cd, and Hg were detected in the biogas digestate in each trial, however, their concentrations were always lower than the limit values stated in Turkish regulations. The main source of heavy metals in the biogas digestate seemed to be the poultry manure, not the agricultural residue. The commercial feedstuffs that are frequently supplemented with various essential elements to promote optimum nutrient supply and optimum growth rates may have contributed to heavy metals presence in the biogas digestate. The results indicated that the biogas digestate from anaerobic co-digestion of manure and agricultural residue could be utilized as fertilizer in agricultural applications.     

Changes in soil chemical and microbiological properties during 4 years of application of various organic residues

A 4-year field trial was established in eastern Sweden to evaluate the effects of organic waste on soil chemical and microbiological variables. A simple crop rotation with barley and oats was treated with either compost from household waste, biogas residue from household waste, anaerobically treated sewage sludge, pig manure, cow manure or mineral fertilizer. All fertilizers were amended in rates corresponding to 100kgNha(-1)year(-1). The effects of the different types of organic waste were evaluated by subjecting soil samples, taken each autumn 4 weeks after harvest, to an extensive set of soil chemical (pH, Org-C, Tot-N, Tot-P, Tot-S, P-AL, P-Olsen, K-AL, and some metals) and microbiological (B-resp, SIR, microSIR active and dormant microorganisms, PDA, microPDA, PAO, Alk-P and N-min) analyses. Results show that compost increased pH, and that compost as well as sewage sludge increased plant available phosphorus; however, the chemical analysis showed few clear trends over the 4 years and few clear relations to plant yield or soil quality. Biogas residues increased substrate induced respiration (SIR) and, compared to the untreated control amendment of biogas residues as well as compost, led to a higher proportion of active microorganisms. In addition, biogas residues increased potential ammonia oxidation rate (PAO), nitrogen mineralization capacity (N-min) as well as the specific growth rate constant of denitrifiers (microPDA). Despite rather large concentrations of heavy metals in some of the waste products, no negative effects could be seen on either chemical or microbiological soil properties. Changes in soil microbial properties appeared to occur more rapidly than most chemical properties. This suggests that soil microbial processes can function as more sensitive indicators of short-term changes in soil properties due to amendment of organic wastes.     

Recycling of organic wastes in burnt soils: combined application of poultry manure and plant cultivation

A pot experiment was conducted to investigate the efficacy of a post-fire land management practice, including plant cultivation (Lolium perenne) combined with poultry manure addition, for restoring the protective vegetation cover in soils degraded by high intensity wildfires. The greenhouse experiment was performed with three burnt pine forest soils with added poultry manure at two doses of application and comparing the data with those obtained using NPK fertilizer. A significant effect of the amendment, soil properties and the interaction between amendment and soil properties on vegetation cover (phytomass production, nutrient content) was detected, but often the amendment treatment explained most of the variance. Changes induced by the organic amendment were more marked than those induced by inorganic fertilization. The increase of phytomass and nutrient uptake with poultry manure addition indicated the beneficial effects of this soil management practice. These findings can serve to develop field experiments and burnt soils reclamation technology.     

Heavy metal mobility and potential availability in animal manure: using a sequential extraction procedure

In this study, dairy cow manure, goat manure, and chicken manure were collected from three farms and analyzed to find out the concentration of Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn. The concentration and potential of mobility and availability of heavy metals were studied in the animal manure samples. BCR Sequential extraction procedure was used to determine the binding forms of the metals. In this study, pseudo total concentrations of Mn and Zn were found out to be predominant in all the types of animal manure samples. According to the results, it was traced that Cr, Cu, and Ni were observed to be at the second highest level while Cd, Co, and Pb were seen at the lowest level in all the manure samples. When extractable amounts of heavy metals are taken into consideration, it is seen that the amount of the mobile fractions of heavy metals except for Cr and Ni are higher in comparison with that of immobile fraction in all the animal manure samples. It was also viewed that Mn, Cd, and Zn are more available in dairy cow manure and chicken manure whereas Cd, Co, and Mn are more available in goat manure.     

Speciation of Cu and Zn during composting of pig manure amended with rock phosphate

Pig manure usually contains a large amount of metals, especially Cu and Zn, which may limit its land application. Rock phosphate has been shown to be effective for immobilizing toxic metals in toxic metals contaminated soils. The aim of this study work was to investigate the effect of rock phosphate on the speciation of Cu and Zn during co-composting of pig manure with rice straw. The results showed that composting process and rock phosphate addition significantly affected the changes of metal species. During co-composting, the exchangeable and reducible fractions of Cu were transformed to organic and residue fractions, thus the bioavailable Cu fractions were decreased. The rock phosphate addition enhanced the metal transformation depending on the level of rock phosphate amendment. Zinc was found in the exchangeable and reducible fractions in the compost. The bioavailable Zn fraction changed a little during the composting process. The composting process converted the exchangeable Zn fraction into reducible fraction. Addition of an appropriate amount (5.0%) of rock phosphate could advance the conversion. Rock phosphate could reduce metal availability through adsorption and complexation of the metal ions on inorganic components. The increase in pH and organic matter degradation could be responsible for the reduction in exchangeable and bioavailable Cu fractions and exchangeable Zn fraction in rock phosphate amended compost.     

Active capping technology—New approaches for in situ remediation of contaminated sediments

This study evaluated pilot‐scale active caps composed of apatite, organoclay, biopolymers, and sand for the remediation of metal‐contaminated sediments. The active caps were constructed in Steel Creek, at the Savannah River Site near Aiken, South Carolina. Monitoring was conducted for 12 months. Effectiveness of the caps was based on an evaluation of contaminant bioavailability, resistance to erosion, and impacts on benthic organisms. Active caps lowered metal bioavailability in the sediment during the one‐year test period. Biopolymers reduced sediment suspension during cap construction, increased the pool of carbon, and lowered the release of metals. This field validation showed that active caps can effectively treat contaminants by changing their speciation, and that caps can be constructed to include more than one type of amendment to achieve multiple goals. © 2012 Wiley Periodicals, Inc.     

Role of iron chemistry in controlling the release of pollutants from resuspended sediments

Aquatic sediments often contain a large number of chemical contaminants that are potential pollutants. It is often presumed that such contaminants are released to the water column during sediment resuspension and, in there, adversely impact aquatic life and other beneficial uses of the water. However, extensive laboratory and field studies of about 100 contaminated sediments from across the United States that specifically addressed this type of release showed that of about 30 common heavy metals, organic compounds, and other potential pollutants, only manganese II and ammonia were released to then remain in the water column after sediment resuspension. These results indicated that the chemistry of aqueous iron controls the availability of many contaminants in resuspended sediment. The formation of ferric hydroxide during sediment suspension into the water column, as a result of the reaction between ferrous iron in the sediments and dissolved oxygen in the water column, leads to rapid scavenging of many contaminants in the Fe(OH)₃ precipitate. The scavenged contaminants are redeposited in the sediments. This article reviews the role of the aqueous chemistry of iron as it relates to controlling the release of potential pollutants from resuspended sediments. © 2005 Wiley Periodicals, Inc.     

生物炭修复Cd,Pb污染土壤的研究进展

随着矿产开采、冶炼等工业活动以及污水灌溉、施用污泥和劣质化肥等农业活动的进行，Cd，Pb等有害重金属不断进入农业环境中，对农田、菜地等造成污染。生物炭作为重要的土壤改良剂，在对Cd，Pb污染土壤的修复中表现出巨大的潜力。从生物炭的特性及制备、修复效果及其影响因素、修复机理等方面，对近年来国内外有关生物炭修复Cd，Pb污染土壤的研究成果和现状进行了总结，并对生物炭修复Cd，Pb污染土壤的发展前景和未来研究方向进行了展望。     

Sequestration of metals in active cap materials: A laboratory and numerical evaluation

Active capping involves the use of capping materials that react with sediment contaminants to reduce their toxicity or bioavailability. Although several amendments have been proposed for use in active capping systems, little is known about their long‐term ability to sequester metals. Recent research has shown that the active amendment apatite has potential application for metals‐contaminated sediments. The focus of this study was to evaluate the effectiveness of apatite in the sequestration of metal contaminants through the use of short‐term laboratory column studies in conjunction with predictive, numerical modeling. A breakthrough column study was conducted using North Carolina apatite as the active amendment. Under saturated conditions, a spike solution containing elemental As, Cd, Co, Se, Pb, Zn, and a nonreactive tracer was injected into the column. A sand column was tested under similar conditions as a control. Effluent water samples were periodically collected from each column for chemical analysis. Relative to the nonreactive tracer, the breakthrough of each metal was substantially delayed by the apatite. Furthermore, breakthrough of each metal was substantially delayed by the apatite compared to the sand column. Finally, a simple 1‐D, numerical model was created to qualitatively predict the long‐term performance of apatite based on the findings from the column study. The results of the modeling showed that apatite could delay the breakthrough of some metals for hundreds of years under typical groundwater flow velocities. © 2012 Wiley Periodicals, Inc.     

Growth performance and proximate profile of Telfairia occidentalis Hook F. (cucurbitaceae) grown in crude oil‒contaminated soil

In this study, the growth performance and nutritional quality of Telfairia occidentalis planted in soil polluted with varied levels of water‐soluble fraction (WSF) of crude oil (Bonny light) were evaluated to assess the effectiveness of organic nutrients (poultry manure and sawdust) in the phytore mediation of WSF‐contaminated soil. The results showed that WSF application delayed germination of vegetables. However, treatment of soils with organic nutrients enhanced the germination rate of vegetables, promoted greenish coloration of leafs and increased the levels of energy‐yielding macronutrients (carbohydrate, lipid, and protein). Also, soils supplemented with poultry manure gave the highest caloric values for all the percentages of WSF studied, followed by sawdust. Our findings suggest that the adverse effects of WSF on soil could be remediated through organic nutrient supplementation. © 2006 Wiley Periodicals, Inc.     

Heavy metal and nutrient changes during vermicomposting animal manure spiked with mushroom residues

A pilot-scale trial of four months was conducted to investigate the responses of heavy metal and nutrient to composting animal manure spiked with mushroom residues with and without earthworms. Results showed that earthworm activities accelerated organic matter mineralization (e.g. reduction in C/N ratio, increase in total concentrations of N, P, K) and humification (e.g. increase in humic acid concentration, humification ratio and humification index). Despite composting increased total heavy metal (i.e. As, Pb, Cu, Zn) concentrations irrespective of earthworm, the availability of heavy metals extracted by DTPA significantly (P < 0.05) decreased particularly in treatments with earthworms introduced. The shift from available to unavailable fractions of heavy metals was either due to earthworm bioaccumulation, as indicated by total heavy metal concentrations being higher in earthworm tissues, or due to the formation of stable metal-humus complexes as indicated by the promotion of humification. Our results suggest that vermicomposting process could magnify the nutrient quality but relieve the heavy metals risk of agricultural organic wastes.     

Depletion of chlortetracycline during composting of aged and spiked manures

Chlortetracycline (CTC) is one of the most important pharmaceuticals occurring in the environment. An increase of its application as feed supplement for livestock and poultry in the world leads to a substantial CTC contamination of manures, because most of the CTC is excreted to manure. The simulation experiment of aerobic composting was adopted to investigate CTC depletion in aged and spiked manure composting, and to address the extent of CTC depletion during composting. The results showed that the extractable CTC initial concentration was markedly different between the different manures, with 94.71mgkg(-1) in broiler manure and 879.6mgkg(-1) in hog manure. The concentration of extractable CTC decreased rapidly at the initial stage of composting, and subsequently declined slowly during aged and spiked manure composting. At the end of composting, more than 90% of CTC in the manure composting process (42 days) was depleted, except for hog manure composting with a removal of only 27%. The CTC half-lives were 11.0 days in broiler manure, 86.6 days in hog manure, 12.2 days in layer-hen manure (150.3mgkg(-1) CTC), 12.0 days in layer-hen manure (100.0mgkg(-1) CTC) and 4.39 days in layer-hen manure (53.10mgkg(-1) CTC), all according to the first order kinetics. The significance of experimental parameters in CTC depletion was assessed by the Pearson correlation approach. Microbial degradation of CTC was not effective from manure composting. CTC depletion was in good correlation with total organic carbon, total nitrogen, total phosphorus, C/N, N/P and total heavy metals.     

重金属污染土壤生物毒性的发光菌法测定及评价

向土壤中人为投加重金属污染物,制备了重金属含量不同的一系列污染土壤,对土壤重金属浸提条件进行了探究,并应用明亮发光杆菌T3（Photobacterium phosphoreum T3）对单一Cu、Cd和Pb污染及Cu-Cd和Cu-Pb复合重金属污染土壤的生物毒性进行了测定。实验结果表明,土壤重金属的最佳浸提剂为0.1 mol/L HCl溶液,最佳浸提时间为2.0 h。在单一重金属污染条件下：Cu表现出低浓度促进生长、高浓度抑制生长的双重生物效应,而Cd和Pb则表现出浓度与生物毒性的正相关性;3种重金属污染土壤的毒性强弱顺序为Cd>Pb>Cu。在复合重金属污染条件下,由于重金属之间的相互作用,污染土壤的生物毒性增强。     

Evaluation of Active Cap Materials for Metal Retention in Sediments

This study evaluated chemically active amendments used to construct active caps for remediating contaminated sediments. Three experiments assessed the effects of apatite, organoclay, zeolite, and biopolymers (chitosan and xanthan) on metal mobility, retention, and speciation. The first showed that the amendments individually and in mixtures (2 percent dry weight) reduced the concentrations of Cr, Co, Ni, and Pb in water extracts from reduced sediment. The second experiment, which used sequential extraction procedures to evaluate the effects of the amendments on metal speciation, showed that the amendments reduced the potentially mobile fractions of Pb, Zn, Ni, Cr, and Cd that are likely to be bioavailable. Last, column studies showed that active caps composed of the amendments prevented the diffusive transport of metals from contaminated sediment over six months. In addition, there was a “zone of influence” beneath the caps in which water extractable concentrations of metals declined substantially compared with untreated sediment. © 2014 Wiley Periodicals, Inc.     

Poultry litter-based activated carbon for removing heavy metal ions in water

Utilization of poultry litter as a precursor material to manufacture activated carbon for treating heavy metal-contaminated water is a value-added strategy for recycling the organic waste. Batch adsorption experiments were conducted to investigate kinetics, isotherms, and capacity of poultry litter-based activated carbon for removing heavy metal ions in water. It was revealed that poultry litter-based activated carbon possessed significantly higher adsorption affinity and capacity for heavy metals than commercial activated carbons derived from bituminous coal and coconut shell. Adsorption of metal ions onto poultry litter-based carbon was rapid and followed Sigmoidal Chapman patterns as a function of contact time. Adsorption isotherms could be described by different models such as Langmuir and Freundlich equations, depending on the metal species and the coexistence of other metal ions. Potentially 404 mmol of Cu²⁺, 945 mmol of Pb²⁺, 236 mmol of Zn²⁺, and 250–300 mmol of Cd²⁺ would be adsorbed per kg of poultry litter-derived activated carbon. Releases of nutrients and metal ions from litter-derived carbon did not pose secondary water contamination risks. The study suggests that poultry litter can be utilized as a precursor material for economically manufacturing granular activated carbon that is to be used in wastewater treatment for removing heavy metals.     

Field trial experiment: Phytoremediation with Salix sp. on a dredged sediment disposal site in Flanders,Belgium

Remediation of heavy metal contamination in soil is a widespread environmental issue. Conventional remediation techniques are invasive and often too expensive, particularly if large areas of soil are contaminated. Phytoremediation is the use of plants to remediate soil and groundwater. Phytoremediation of inorganic comtaminants such as metals can be further catagorized into phytostabilization and phytoextraction. These techniques have gained an increasing amount of attention and research over the last ten years. Phytoextraction of heavy metals and periodical removal of harvestable plant parts results in a gradual decrease of pollutant levels in the top soil. Woody species such as Salix sp. (willow) do not represent the fastest phytoextraction procedure compared to uptake by herbaceous species; however, they offer the added advantage of possible reuse of the produced biomass (wood) for the production of renewable energy. Here we present the results of a field experiment conducted to evaluate the use of Salix to remediate soil contaminated with cadmium and zinc at a dredged sediment disposal site in Flanders, Belgium. © 2003 Wiley Periodicals, Inc.     

Evaluation of a soil‐amendment process demonstration for reducing the bioavailability of lead

The U.S. Environmental Protection Agency (EPA) evaluated an in‐situ application of a soil‐amendment process at a residential site that was contaminated with lead. The goal of the evaluation was to determine if the soil‐amendment process resulted in lower concentrations of bioavailable lead in the contaminated soils. The relative bioavailability of lead (bioaccessible lead) was measured by an in vitro test procedure that uses a highly acidic extraction procedure to simulate human digestive processes. The soil‐amendment demonstration showed that the 11.2 percent mean reduction in bioavailable lead concentration between untreated and treated soils was not statistically different. © 2002 Wiley Periodicals, Inc.     

Comparative fertilizer properties of digestates from mesophilic and thermophilic anaerobic digestion of dairy manure: focusing on plant growth promoting bacteria (PGPB) and environmental risk

The fertilizer properties of anaerobic digestate depend on the feedstock and operating conditions of digestion. In this study, the comparative fertilizer properties of mesophilic and thermophilic digestates from dairy manure were evaluated for plant nutrient contents, and special attention was paid to plant growth promoting bacteria (PGPB). Two digestates contained similar plant nutrient contents, while the thermophilic digestate contained higher contents of NH₄⁺–N. The quantity of Bacillus and Pseudomonas in the mesophilic digestate was significantly higher than in the thermophilic digestate. Furthermore, Bacillus showed siderophore production and antifungal activity (43.5–75.3%), and Pseudomonas showed siderophore and phytohormone production (4.2–75.2 µg ml^?1). One phosphate solubilizing isolate was also detected in the mesophilic digestate. These results indicated that two digestates showed different fertilizer properties with respect to nutrient contents and PGPB, and digestates had the potential to increase the availability of phosphorus and iron in the soil, both to provide phytohormones to plant roots and protect plants from fungal phytopathogens. The contents of indicator bacteria and heavy metals were analyzed to determine their environmental risk, and the results showed a high reduction in indicator bacteria and lower levels of heavy metals than in other feedstocks.     

Genotoxicity of leachates from highly polluted lowland river sediments destined for disposal in landfill

The Matanza-Riachuelo is one of the most polluted rivers of Latin America. The complex chemical mixture of pollutants discharged into the river is accumulated in the river sediments. In this paper, Matanza-Riachuelo river sediment composition and genotoxicity were tested in order to develop a cost-effective, environmentally sound option for disposal and management of contaminated dredged materials. Sampling was performed in a rural area, in a solid waste dumpsite and also in an urban and industrial area. The concentrations of total heavy metals increased from the upper basin to the lower basin. The Ames Salmonella typhimurium test and the Saccharomyces cerevisiae D7 test were performed using toxicity characteristic leachate procedure (TCLP) leachates. The concentrations of copper, lead, and chromium in the leachates exceeded the guide levels for the protection of aquatic life. Low concentrations of organic chlorinated compounds were detected in the leachates. Genotoxic profiles were obtained by testing TCLP leachates from polluted sediment samples with Salmonella typhimurium, Saccharomyces cerevisiae D7, and water sediment suspension with Allium cepa test. No mutagenicity effects on Ames test were observed. Gene conversion and mitotic reversion in Saccharomyces cerevisiae D7 and chromosome aberration in Allium cepa were induced by the sediment samples. Results obtained suggest that dredged sediments could be classified as genotoxic hazardous waste.     

Development of a waterjet system for direct delivery of granular iron and activated carbon to remediate contaminated aqueous sediments

While the techniques and technologies associated with contaminated sediment remediation are relatively mature, there are several issues associated with these practices that make them unattractive. The inability of currently used mechanical mixing implements to place amendments in aqueous environments and their intrusive behavior toward benthic communities are just two examples of a necessity for an improved delivery method. Waterjets may be a viable option for placement of particulate remediation amendments, such as activated carbon and granular iron, at depth. A custom waterjet nozzle and injection system has been fabricated by the authors to examine this delivery concept. The developed injection system's performance was tested by characterizing the waterjet‐delivered amendment (activated carbon and granular iron) distributions in a surrogate sediment. The delivered amendment distributions followed similar patterns for a range of injection times and a variety of amendments. The injection depths, however, were dependent upon the type of amendment being injected. These findings have led to a better understanding of what occurs during an amendment injection, which can be used for a more controlled placement of remediation amendments using this technique in the future. The laboratory results indicate that the subject waterjet system may have the potential for field‐scale applications, especially for granular iron delivery, as the authors were able to place between 60 and 70 wt percent into a surrogate sediment bed along the path of injection. © 2011 Wiley Periodicals, Inc.