Stocking rate and organic waste type affect development of three Chrysomya species and Lucilia sericata (Diptera: Calliphoridae): Implications for bioconversion

Fly larvae can be used effectively to reduce various organic waste types and produce value-added products, including protein as an ingredient in livestock feeds and oil for biodiesel production. However, fly development on different waste types may cause differences in growth rate and the body composition, which can further be influenced by fly species and their stocking rate. This study explored the impact of different waste types (kitchen waste, abattoir waste and swine manure) and larval stocking rate on growth and body composition of four blowfly species, Chrysomya chloropyga (Wiedemann), Chrysomya megacephala (Fabricius), Chrysomya putoria (Wiedemann) and Lucilia sericata (Meigen). First-instar larvae (20, 50 or 100), less than 3 hr old, were placed on 100 g of each waste type. Pre-pupal mass at commencement of post-feeding larval dispersal, time to onset of dispersal, survival and nutrient reserves were determined for each species, stocking rate and waste type. Our results revealed that larvae fed kitchen and abattoir waste had significantly higher dry mass, crude protein and lipid content compared with those fed swine manure. Higher survival rate was observed with increasing larval stocking rate. We provide important information to guide the mass production of high-quality nutrient-rich larvae and recommend C. putoria, which is versatile and effective on a range of waste products, as well as high in protein and lipids. The implications for waste management are discussed.     

Analysis of copper corrosion in compacted bentonite clay as a function of clay density and growth conditions for sulfate‐reducing bacteria

Aims: To investigate the relationships between sulfate‐reducing bacteria (SRB), growth conditions, bentonite densities and copper sulfide generation under circumstances relevant to underground, high‐level radioactive waste repositories. Methods and Results: Experiments took place 450 m underground, connected under in situ pressure to groundwater containing SRB. The microbial reduction of sulfate to sulfide and subsequent corrosion of copper test plates buried in compacted bentonite were analysed using radioactive sulfur (³⁵SO₄^2?) as tracer. Mass distribution of copper sulfide on the plates indicated a diffusive process. The relationship between average diffusion coefficients (D_s) and tested density (ρ) was linear. D_s (m² s^?1) = ?0·004 × ρ (kg m^?3) + 8·2, decreasing by 0·2 D_s units per 50 kg m^?3 increase in density, from 1·2 × 10^?11 m² s^?1 at 1750 kg m^?3 to 0·2 × 10^?11 m² s^?1 at 2000 kg m^?3. Conclusions: It is possible that sulfide corrosion of waste canisters in future radioactive waste repositories depends mainly on sulfide concentration at the boundary between groundwater and the buffer, which in turn depends on SRB growth conditions (e.g., sulfate accessibility, carbon availability and electron donors) and geochemical parameters (e.g., presence of ferrous iron, which immobilizes sulfide). Maintaining high bentonite density is also important in mitigating canister corrosion. Significance and Impact of the Study: The sulfide diffusion coefficients can be used in safety calculations regarding waste canister corrosion. The work supports findings that microbial activity in compacted bentonite will be restricted. The study emphasizes the importance of growth conditions for sulfate reduction at the groundwater boundary of the bentonite buffer and linked sulfide production.     

Semicontinuous anaerobic digestion of soft drink wastewater in immobilised cell bioreactors

Summary Saponite support considerably increased the kinetics of a. semicontinuous anaerobic digestion process treating soft drink wastewater showing values of the _max andK kinetic parameters (Chen and Hashimoto model) 2.5 and 1.4 times higher than for bentonite and polyurethane support, respectively. This was significant at 95% confidence level.     

Influence of the microorganism support on the kinetics of anaerobic fermentation of condensation water from thermally concentrated olive mill wastewater

Two materials of different structure, sepiolite and bentonite, evaluated as supports for the microorganisms effecting anaerobic fermentation, behaved differently towards condensation water from thermally concentrated olive mill wastewater from a kinetic point of view. Assuming the overall anaerobic digestion process to conform to first-order kinetics, the apparent kinetic constant for the digester including sepiolite as support was 1.12 day^-1, while that of the digester using the bentonite support was 0.73 day^-1. Thus, the apparent kinetic constant of the process was increased by 35% with the use of sepiolite. The yield coefficient, Y_p/s, was 0.344 and 0.318 litres CH₄ STP/g COD for the sepiolite and bentonite supports respectively.     

Microbial diversity and dynamics of a groundwater and a still bottled natural mineral water

The microbial abundance and diversity at source, after bottling and through 6 months of storage of a commercial still natural mineral water were assessed by culture‐dependent and culture‐independent methods. The results revealed clear shifts of the dominant communities present in the three different stages. The borehole waters displayed low cell densities that increased 1.5‐fold upon bottling and storage, reaching a maximum (6.2 × 10⁸ cells l^?1) within 15 days after bottling, but experienced a significant decrease in diversity. In all cases, communities were largely dominated by Bacteria. The culturable heterotrophic community was characterized by recovering 3626 isolates, which were primarily affiliated with the Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria. This study indicates that bottling and storage induce quantitative and qualitative changes in the microbial assemblages that seem to be similar as revealed by the two sample batches collected on 2 consecutive years. To our knowledge, this is the first study combining culture‐independent with culture‐dependent methods, and repeated tests to reveal the microbial dynamics occurring from source to stored bottled water.     

In vitro evaluation of the capacity of zeolite and bentonite to adsorb aflatoxin B1 in simulated gastrointestinal fluids

Anin vitro study using single concentration and isotherm adsorption was carried out to evaluate the capacity of Vietnamese produced zeolite and bentonite to adsorb aflatoxin B₁ (AFB₁) in simulated gastrointestinal fluids (SGFs), and a commercial sorbent hydrated sodium calcium aluminosilicate (HSCAS) was used as reference. In this study, AFB₁ solution was mixed with sorbents (0.3, 0.4 and 0.5% w/v) in SGFs at pH 3 and pH 7 and shaken for 8 h, centrifuged and the supernatant measured by Vicam fluorometer. Adsorption of AFB₁ onto zeolite and bentonite varied according to the pH of SGFs and was lower than HSCAS. Linearity between the increased amount of AFB₁ adsorbed on sorbents and the decrease of sorbent concentration was observed for bentonite and HSCAS, except for zeolite in SGFs at pH 7. The observed maximum amounts of AFB₁ adsorbed on bentonite and HSCAS were 1.54 and 1.56 mg/g, respectively. The adsorption capacities of bentonite and HSCAS for AFB₁ were 12.7 and 13.1 mg/g, respectively, from fitting the data to the Freundlich isotherm equation. Improvement in processing and purification for bentonite is needed to enhance the surface area, which would probably result in better adsorptive capacity for this sorbent.     

Nickel removal from nickel plating waste water using a biologically active moving-bed sand filter

Efficient removal of dissolved nickel was observed in a biologically active moving-bed `MERESAFIN' sand filter treating rinsing water from an electroless nickel plating plant. Although nickel is fully soluble in this waste water, its passage through the sand filter promoted rapid removal of approximately 1 mg Ni/l. The speciation of Ni in the waste water was modelled; the most probable precipitates forming under the conditions in the filter were predicted using PHREEQC. Analyses of the Ni-containing biosludge using chemical, electron microscopical and X-ray spectroscopic techniques confirmed crystallisation of nickel phosphate as arupite (Ni₃(PO₄)₂.8H₂O), together with hydroxyapatite within the bacterial biofilm on the filter sand grains. Biosorption contributed less than 1% of the overall sequestered nickel. Metabolising bacteria are essential for the process; the definitive role of specific components of the mixed population is undefined but the increase in pH promoted by metabolic activity of some microbial components is likely to promote nickel desolubilisation by others.     

Impact of abattoir waste on Woji Creek,Port Harcourt,Nigeria, using physicochemistry and macrozoobenthic diversity indices

The impact of waste discharge from Zoo abattoir, Port Harcourt, on the environmental quality of Woji Creek was studied from April 2001 to March 2002 using physicochemistry and diversity of benthic animals as indicators. Priority physicochemical parameters (total suspended solid, dissolved oxygen and biochemical oxygen demand) indicated high organic enrichment, chiefly due to inputs of bloody effluent. The burning of animal skin with discarded car tyres to produce kpomo, a common local soup component, contributes to the creek's quality alterations. Ironically, diversity of zoobenthos was highest at the area receiving the abattoir effluents compared to areas upstream and downstream from that point. Possible explanations are provided for the inverted diversity trend using the Hutcheson Index, which indicated significant diversities in invertebrate species amongst the three sample sites. The inefficiency of ecosystem quality evaluations using isolated single indices is also discussed.     

Effects of lipids on thermophilic anaerobic digestion and reduction of lipid inhibition upon addition of bentonite

Summary The effect of bentonite-bound oil on thermophilic anaerobic digestion of cattle manure was investigated. In digestor experiments, addition of oil was found to be inhibitory during start-up and the inhibitory effect was less pronounced when the oil was added in the form of bentonite-bound oil compared to when the oil was added alone. After adaption of the digestors, very rapid degradation of oil was observed and more than 80% of the oil was degraded within a few hours after daily feeding. In batch experiments, glyceride trioleate was found to be inhibitory to thermophilic anaerobic digestion when the concentrations were higher than 2.0 g/l. However, addition of bentonite (a clay mineral) at concentrations of 0.15% and 0.45% was found to partly overcome this inhibition. Addition of calcium chloride in concentration of 3 mM (0.033% w/v) showed a similar positive effect on the utilization of oil, but the effect was lower than with bentonite. Offprint requests to: I. Angelidaki     

Specificity of a Nuclease from Penicillium citrinum

The enzyme with high milk clotting activity produced by Irpex lacteus was partially purified by a CM-cellulose chromatography. Throughout the over-all process, the enzyme was purified approximately 9-fold from a crude powder with about 22.8% recovery of the original activity. The MCA/PU ratio of this fraction was 2.51 and the specific milk clotting activity was 188.7.

The purified enzyme is a sort of acid protease with optimum pH of 2.5 for casein digestion and 4.0 for hemoglobin digestion. The Lineweaver-Burk plot, when casein was used as a substrate, showed that the Km value of the enzyme was about 0.07% and the V_max value was 0.4. The molecular weight of the enzyme is about 34,000, the isoelectric point is pH 5.2 and a ultraviolet absorption maximum is at 277 mμ. The enzyme has not yet been crystalized but seems to be a sort of glycoprotein, because the Molish reaction was positive at the present purification stage.

Some enzymological properties of the enzyme was studied and compared with those of a calf rennet and Mucor rennet. In some respects such as pH optima, pH stability, thermostability and temperature optima, the enzyme is Mucor rennet alike. On the other hand, as to the increase in activity along with decrease in pH of milk and the increase in activity along with the addition of Ca ion, the enzyme is not very different from the calf rennet. However, proteolysis of milk casein by the enzyme was fairly higher than by the calf rennet.

As to the production of enzymes, I. lacteus can produce at least three types of proteases into liquid media. When, for example, R medium was used, only one type of protease, that is the fraction A, could mainly be produced and it was this enzyme that assumed to be a rennet like enzyme.     

Occurrence and Persistence of Erythromycin Resistance Genes (erm) and Tetracycline Resistance Genes (tet) in Waste Treatment Systems on Swine Farms

Animal manure from modern animal agriculture constitutes the single largest source of antibiotic resistance (AR) owing to the use of large quantities of antibiotics. After animal manure enters the environment, the AR disseminates into the environment and can pose a potentially serious threat to the health and well-being of both humans and animals. In this study, we evaluated the efficiency of three different on-farm waste treatment systems in reducing AR. Three classes of erythromycin resistance genes (erm) genes (B, F, and X) conferring resistances to macrolide–lincosamides–streptogramin B (MLS_B) and one class of tetracycline resistance genes (tet) gene (G) conferring resistance to tetracyclines were used as models. Real-time polymerase chain reaction assays were used to determine the reservoir sizes of these AR genes present in the entire microbiome. These classes of AR genes varied considerably in abundance, with erm(B) being more predominant than erm(F), erm(X), and tet(G). These AR genes also varied in persistence in different waste treatment systems. Aerobic biofiltration reduced erm(X) more effectively than other AR genes, while mesophilic anaerobic digestion and lagoon storage did not appreciably reduce any of these AR genes. Unlike chemical pollutants, some AR genes could increase after reduction in a preceding stage of the treatment processes. Season might also affect the persistence of AR. These results indicate that AR arising from swine-feeding operations can survive typical swine waste treatment processes and thus treatments that are more effective in destructing AR on farms are required.     

The Influence of Hydraulic Gradient and Rate of Erosion on Hydraulic Conductivity of Sand-Bentonite Mixtures

The use of sand-bentonite mixtures as liner materials for waste disposal is very common. In the laboratory, this study investigated hydraulic conductivities of such mixtures at different hydraulic pressure (hydraulic gradient), dry unit weights, and bentonite contents. The bentonite content and the dry unit weight of the samples were both important factors, significantly affecting the hydraulic conductivity of the liner material. A bentonite content of 5% was found to be sufficient in reaching a hydraulic conductivity under 10^?9 m/s, when the liner material was compacted under near optimum moisture content. Nevertheless, hydraulic conductivity was found to increase with hydraulic pressures, especially for the 5% bentonite mixtures subjected to pressure above 40 kPa, suggesting some degree of internal erosion (washing out of particles).

Therefore, this paper discuses the influence of internal erosion of the mixtures under a given hydraulic gradient, on the final value of k. The internal erosion of the tested mixtures was found to be influenced mainly by porosity, which can be reduced by properly selecting the sand particle size distribution and the bentonite percentage. Furthermore, this study proposed an empirical expression to predict the risk of internal erosion in the sand-bentonite mixtures, and therefore of k being higher than planned. This expression can be used for designing bentonite content and compaction to achieve very low permeability.     

Effects of Stimulation of Copper Bioleaching on Microbial Community in Vineyard Soil and Copper Mining Waste

Long-term copper application in vineyards and copper mining activities cause heavy metal pollution sites. Such sites need remediation to protect soil and water quality. Bioremediation of contaminated areas through bioleaching can help to remove copper ions from the contaminated soils. Thus, the aim of this work was to evaluate the effects of different treatments for copper bioleaching in two diverse copper-contaminated soils (a 40-year-old vineyard and a copper mining waste) and to evaluate the effect on microbial community by applying denaturing gradient gel electrophoresis (DGGE) of 16S ribosomal DNA amplicons and DNA sequence analysis. Several treatments with HCl, H₂SO₄, and FeSO₄ were evaluated by stimulation of bioleaching of copper in the soils. Treatments and extractions using FeSO₄ and H₂SO₄ mixture at 30°C displayed more copper leaching than extractions with deionized water at room temperature. Treatment with H₂SO₄ supported bioleaching of as much as 120 mg kg⁻¹ of copper from vineyard soil after 115 days of incubation. DGGE analysis of the treatments revealed that some treatments caused greater diversity of microorganisms in the vineyard soil compared to the copper mining waste. Nucleotide Blast of PCR-amplified fragments of 16S rRNA gene bands from DGGE indicated the presence of Rhodobacter sp., Silicibacter sp., Bacillus sp., Paracoccus sp., Pediococcus sp., a Myxococcales, Clostridium sp., Thiomonas sp., a firmicute, Caulobacter vibrioides, Serratia sp., and an actinomycetales in vineyard soil. Contrarily, Sphingomonas was the predominant genus in copper mining waste in most treatments. Paracoccus sp. and Enterobacter sp. were also identified from DGGE bands of the copper mining waste. Paracoccus species is involved in the copper bioleaching by sulfur oxidation system, liberating the copper bounded in the soils and hence promoting copper bioremediation. Results indicate that stimulation of bioleaching with a combination of FeSO₄ and H₂SO₄ promoted bioleaching in the soils and can be employed ex situ to remediate copper-impacted soils.     

Modified Ceria for “Low‐Temperature” CO2 Utilization: A Chemical Looping Route to Exploit Industrial Waste Heat

Efficient CO₂ utilization is key to limit global climate change. Carbon monoxide, which is a crucial feedstock for chemical synthesis, can be produced by splitting CO₂. However, existing thermochemical routes are energy intensive requiring high operating temperatures. A hybrid redox process (HRP) involving CO₂‐to‐CO conversion using a lattice oxygen‐deprived redox catalyst at relatively low temperatures (<700 °C) is reported. The lattice oxygen of the redox catalyst, restored during CO₂‐splitting, is subsequently used to convert methane to syngas. Operated at temperatures significantly lower than a number of industrial waste heat sources, this cyclic redox process allows for efficient waste heat‐utilization to convert CO₂. To enable the low temperature operation, lanthanum modified ceria (1:1 Ce:La) promoted by rhodium (0.5 wt%) is reported as an effective redox catalyst. Near‐complete CO₂ conversion with a syngas yield of up to 83% at low temperatures is achieved using Rh‐promoted LaCeO_4?x. While La improves low‐temperature bulk redox properties of ceria, Rh considerably enhances the surface catalytic properties for methane activation. Density functional theory calculations further illustrate the underlying functions of La‐substitution. The highly effective redox catalyst and HRP scheme provide a potentially attractive route for chemical production using CO₂, industrial waste heat, and methane, with appreciably lowered CO₂ emissions.     

Isolation and Identification of Autochthonous Microbiota from a Granitic Aquifer and Its Variation After the Bottling Process

The autochthonous microbiota from a granitic aquifer in Spain were studied. Several bacterial strains were isolated and identified. The major components of the microbiota were Pseudomonas-like strains, Flavobacterium, Acinetobacter, and Alcaligenes. The variation in the number of microorganisms after the bottling process was studied. The initial bacterial population increased over the first 5 days after bottling. This increase was higher in samples from polyvinyl chloride bottles. Sonication usually increased the total cell counts. As expected, most of the autochthonous microbiota were not detected in the viable cell counts. Received: 28 March 2000 / Accepted: 23 May 2000     

Application of variable number of tandem repeat analysis to track Salmonella enterica ssp. enterica serovar Typhimurium infection of pigs reared on three British farms through the production cycle to the abattoir

Aims: This study investigated the diversity and persistence of Salmonella strains through the pork finishing cycle, from the farm into the abattoir. Methods and Results: Isolates from four batches of finishers, from farm to abattoir, were used. Salmonella Typhimurium isolates were subjected to molecular typing using pulsed‐field gel electrophoresis and variable number of tandem repeat analysis. The results demonstrated that infection was transferred from the farm to the abattoir. Within the abattoir, infection from individual pigs contaminated the exterior of the carcass and pigs exposed to Salmonella in the lairage were infected. Conclusions: Salmonella can be introduced at various points in the pig production and slaughter process. Carcass contamination may arise from infection on farm and exposure in the lairage and abattoir environment. Pigs could be contaminated by previous batches of pigs while in lairage or during the dressing process. Salmonella infection on farms is dynamic with multiple serovars present from different sources. Significance and Impact of the Study: Molecular typing methods facilitated the tracing of Salm. Typhimurium through the production cycle and differentiated some farm‐acquired from abattoir‐acquired strains. The findings emphasize the importance of integrated control strategies along the pork food chain.     

Design of a Prediction Model for the Differentiation of Pasteurized Milk from Heated ESL Milk by Peptide Profiling

This study designs a prediction model to differentiate pasteurized milk from heated extended shelf life (ESL) milk based on milk peptides. For this purpose, quantitative peptide profiles of a training set of commercial samples including pasteurized (n = 20), pasteurized‐ESL (n = 13), and heated‐ESL (n = 16) milk are recorded by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS). Seven peptides are selected as putative markers, and cutoff levels and performance measures of each marker are defined by receiver operating characteristic (ROC) analysis. The accuracy of these peptides in the training set range between 71% and 90%. A prediction model is established based on the combined cutoff levels and evaluated by an independent blind test set. The processing method of 19 out of 20 unknown milk samples is predicted correctly achieving 95% accuracy. Five peptides of the prediction model are identified as α_S1‐casein_182–199 (m/z 2014.0), α_S1‐casein_180–199 (m/z 2216.1), α_S1‐casein_1–24 (m/z 2910.6), β‐casein_108–125 (m/z 2126.0), and β‐casein_106–125 (m/z 2391.2) indicating thermal release and the action of plasmin and cathepsins. Thus, the present study demonstrates that the milk peptide profile reflects even minor differences in production parameters.     

Mesophilic and thermophilic anaerobic co-digestion of abattoir wastewater and fruit and vegetable waste in anaerobic sequencing batch reactors

Anaerobic co-digestion of fruit and vegetable waste (FVW) and abattoir wastewater (AW) was investigated using anaerobic sequencing batch reactors (ASBRs). The effects of hydraulic retention time (HRT) and temperature variations on digesters performances were examined. At both 20 and 10 days biogas production for co-digestion was greater thanks to the improved balance of nutrients. The high specific gas productions for the different digestion processes were 0.56, 0.61 and 0.85 l g⁻¹ total volatile solids (TVS) removal for digesters treating AW, FVW and AW + FVW, respectively. At an HRT of 20 days, biogas production rates from thermophilic digesters were higher on average than from mesophilic AW, FVW and AW + FVW digestion by 28.5, 44.5 and 25%, respectively. However, at 10 days of HRT results showed a decrease of biogas production rate for AW and AW + FVW digestion processes due to the high amount of free ammonia at high organic loading rate (OLR).     

Chemical Compatibility of Lime Stabilized Indian Red Earth as Liner Material

Geotechnical liners are widely used to contain leachate generated within landfills and minimize the risk of sub-surface and underground water contamination. In this study, an attempt has been made to utilize locally available soil red earth as liner material. The collected red earth contains mostly quartz and kaolinitic minerals. Studies have shown that bentonite content higher than 20% by weight is not usually required. This study aims to assess the red earth with 20% by weight of bentonite as liner material. Further, the studies are being carried out to improve the amended material by stabilizing the mixture with 1% by weight of lime. The relative merits of these materials under different physico-chemical environments are studied. The assessment of the liner material is based on their basic and geotechnical properties. The studies reveal that the geotechnical properties of red earth with 20% by weight bentonite stabilized with 1% by weight of lime enhanced, particularly after curing for sufficient period. The pore fluids such as HCl and CCl ₄ increased volume change. The hydraulic conductivity of soils, which increased on treating with lime initially, decreased with curing. However, the hydraulic conductivity of stabilized soil increased in the presence of HCl and CCl ₄ . The strength of stabilized soil is affected with the fluids NaCl and HCl solutions.     

Removal of molecular weight fractions of COD and phenolic compounds in an integrated treatment of olive oil mill effluents

Previous works (Beccari et al. 1999b; Beccari et al. 2001a; Beccari et al. 2001b)on the anaerobic treatment of olive oil mill effluents (OME) have shown: (a) apre-treatment based on the addition of Ca(OH)₂ and bentonite was able toremove lipids (i.e. the most inhibiting substances present in OME) almostquantitatively; (b) the mixture OME – Ca(OH)₂ – bentonite, fed to amethanogenic reactor without providing an intermediate phase separation,gave way to high biogas production even at very low dilution ratios; (c) theeffluent from the methanogenic reactor still contained significant concentrationsof residual phenolic compounds (i.e. the most biorecalcitrant substances present inOME). Consequently, this paper was aimed at evaluating the fate of the phenolicfractions with different molecular weights during the sequence of operations(adsorption on bentonite, methanogenic digestion, activated sludge post-treatment).The results show that a very high percentage (above 80%) of the phenolic fractionbelow 500 D is removed by the methanogenic process whereas the phenolic fractionsabove 1,000 D are significantly adsorbed on bentonite; the 8-day activated sludgepost-treatment allows an additional removal of about 40% of total filtered phenoliccompounds. The complete sequence of treatments was able to remove more than the96% of the phenolic fraction below 500 D (i.e. the most toxic fraction towards plantgermination). Preliminary respirometric tests show low level of inhibition exerted bythe effluent from the methanogenic reactor on aerobic activated sludges taken fromfull-scale municipal wastewater plants.