Higher pH and faster decomposition in biowaste composting by increased aeration

Composting of source separated municipal biowaste has at several plants in Scandinavia been hampered by low pH. In this study the hypothesis that increased aeration would improve the process was tested in full-scale experiments at two large composting plants. The O2 concentrations were high (>15%) even at the low aeration rates, so the prevailing low pH was not due to an anaerobic process environment. In spite of this, increased aeration rates at the start of the process resulted in higher microbial activity, increased pH and a more stable compost product. At one plant the decomposition rate varied in proportion to the aeration rate, to the extent that the temperatures and O2 concentrations were similar during the early processes even though aeration rates varied between 10 and 50 m3/(h, m3 compost). However, increased aeration caused severe drying of the compost, but at one plant the addition of water was adequate to prevent drying. In conclusion, by increasing the aeration rates and adding water to compensate for drying, it was possible to shorten the time needed to produce a stable compost product and thus to increase the efficiency of the composting plants.     

Evaluation of leaching and extraction procedures for soil and waste

Laboratory leaching tests may be used for source term determination as a basis for risk assessment for soil-groundwater pathways on contaminated sites. In order to evaluate different leaching procedures, batch extraction tests and percolation tests were performed using three reference materials produced from contaminated soil, demolition waste and municipal solid waste incinerator bottom ash. Emphasis was placed on the investigation of the leachability of the heavy metals copper and chromium, polycyclic aromatic hydrocarbons (PAHs) and the anions chloride and sulfate. Significant discrepancies between column experiments and batch/extraction tests were found for the release of PAHs and to a lesser extent for the heavy metals Cu and Cr. Additionally interlaboratory comparisons were conducted based on different leaching tests with the reference materials and evaluated using the criteria of comparability and reproducibility. The best reproducibility was achieved for all investigated substances in column tests. The reproducibility of batch tests was acceptable except for PAHs. The results from the experimental work will help establish standardized and feasible laboratory procedures as fundamental for substance specific risk assessment of contaminated sites.     

Removal of insoluble chloride from bottom ash for recycling

In order to recycle bottom ash and use it as raw material for cement production, the removal of insoluble chloride was investigated by testing various washing techniques. The present work is also focused on investigating the properties of insoluble chlorides and determining the conditions for dissolving these compounds in order to reduce the chlorine content to the required level, i.e., less than 0.1 wt%. Within this framework, the effect of washing with water and CO2 bubbling was investigated, because the main insoluble chloride found in bottom ash, i.e., Friedel's salt, can be dissolved by CO2. Then, in order to better understand the removal of Cl, Friedel's salt was artificially synthesized by hydration and then the effect of CO2 bubbling was investigated. If all chlorides in the ash are converted into Friedel's salt by hydration, all chlorides can then be dissolved by CO2 bubbling. In addition, the effect of pH on removing the remaining insoluble chlorides was investigated by washing the ash with sulfuric acid solution. It was found that the most effective technique to reduce the Cl content to less than 1000 ppm was washing with sulfuric acid solution, while keeping the pH value at less than 4. By using this method, Friedel's salt and other insoluble chlorides were dissolved.     

Soils, climate change and the OECD

Some concepts of sustainability applied to soils are given in relation to the Organisation for Economic Co-operation and Development (OECD) Co-operative Research Programme 'Biological Resource Management for Sustainable Agricultural Systems'. The application of these concepts to climate change will be discussed in relation to seven high-profile papers published over the past 12 months. It is argued that multi-disciplinary (including social science) approaches are needed to address the issues. There is also a brief discussion on biomass energy in terms of soil sustainability and climate change.     

Participatory environmental governance in China: public hearings on urban water tariff setting

In the late 1990s China started to expand its market economic reform to the public sector, such as water services. This reform led to major changes in urban water management, including water tariff management. The reforms in water tariff management relate not only to tariffs, but also to the decision-making on tariffs. Water tariff decision-making seems to move away from China's conventional mode of highly centralized and bureaucratic policy- and decision-making. The legalization, institutionalization and performance of public hearings in water tariff management forms a crucial innovation in this respect. This article analyzes the emergence, development and current functioning of public hearings in water tariff setting, and assesses to what extent public hearings are part of a turning point in China's tradition of centralized bureaucratic decision-making, towards more transparent, decentralized and participative governance.     

Mechanical Property Characterization of Plasticized Sugar Beet Pulp and Poly(Lactic Acid) Green Composites Using Acoustic Emission and Confocal Microscopy

Sorbitol and glycerol were used to plasticize sugar beet pulp-poly(lactic acid) green composites. The plasticizer was incorporated into sugar beet pulp (SBP) at 0%, 10%, 20%, 30% and 40% w/w at low temperature and shear and then compounded with poly(lactic acid) (PLA) using twin-screw extrusion and injection molding. The SBP:PLA ratio was maintained at 30:70. As expected, tensile strength decreased by 25% and the elongation increased. Acoustic emission (AE) showed correlated debonding and fracture mechanisms for up to 20% w/w plasticizer and uncorrelated debonding and fracture for 30–40% sorbitol and 30% glycerol content in SBP–PLA composites. All samples had a well dispersed SBP phase with some aggregation in the PLA matrix. However, at 40% glycerol plasticized SBP–PLA composites exhibited unique AE behavior and confocal microscopy revealed the plasticized SBP and PLA formed a co-continuous two phase system.

Chloramphenicol influence on antioxidant enzymes with preliminary approach on microsomal CYP1A immunopositive-protein in Chamelea gallina

Chloramphenicol (CA) is a largely used antibiotic and it is an inhibitor of protein synthesis that also induces ROS production. In this work there were investigated activities and expressions in the Adriatic bivalve Chamelea gallina of some antioxidant and detoxification proteins like superoxide dismutase (Mn-SOD, Cu/Zn-SOD), catalase (CAT) and Cytochrome P450 (CYP1A). Clams exposed to 5mgl(-1) of chloramphenicol were sampled 2, 4 and 8 days after treatment (CA2, CA4 and CA8). SODs, CAT, and CYP1A activity and/or expression were detected in pooled digestive glands by Western blotting and by spectrophotometrical analysis. Enzymes activities increase during the entire antibiotic exposure. With respect to the control Cu/Zn-SOD expression increases, while Mn-SOD expression decreases significantly after 4 days. Two CYP1A immunopositive-proteins (57.7 and 59.8kDa) were detected. The lower band significantly decreases in CA8, the upper one also in CA4 condition. High levels of Mn-SOD, CAT activity and Cu/Zn-SOD expression, indicate intense ROS production while Mn-SOD expression inhibition might be ascribable to mitochondrial alterations due to CA and indirectly to ROS. CYP1A1 action determines H(2)O(2) production that would contribute to a CYP1A1 gene promoter down regulation, a response to oxidative stress with the antioxidant enzymes activation as a final result. This study highlights the close association, in C. gallina, in presence of chloramphenicol, between SOD/CAT and CYP system, and it appear particularly interesting to the lack of similar researches on mollusc species.     

Anoxic-aerobic treatment of the liquid fraction of cattle manure

Cattle manure from a dairy farm was treated in order to reduce its pollution potential. The manure came from a farm with 120 cows kept in stables in a free stall barn. As pretreatment, the manure is usually filtered on the farm using a screw press separator with a 0.5 mm mesh. Approximately 70% of the total filtered volume passes through the screen, thus constituting the liquid fraction. This fraction, with a composition of around 64,500 mg COD/l, 5770 mg total-N/l and 800 mg total-P/l, was subjected to centrifugation followed by a two-step biological treatment (anoxic-aerobic) to reduce organic matter (COD), nitrogen and phosphorus compounds. Centrifugation led to the following removal efficiencies: 35% total solids, 60% COD, 75% total phosphorus and 20% total nitrogen (mainly organic nitrogen). With the subsequent anoxic-aerobic treatment, average removal efficiencies of 85% for COD, 90% for total phosphorus and 75% for total nitrogen were achieved.     

Bench-scale composting of source-separated human faeces for sanitation

In urine-diverting toilets, urine and faeces are collected separately so that nutrient content can be recycled unmixed. Faeces should be sanitized before use in agriculture fields due to the presence of possible enteric pathogens. Composting of human faeces with food waste was evaluated as a possible method for this treatment. Temperatures were monitored in three 78-L wooden compost reactors fed with faeces-to-food waste substrates (F:FW) in wet weight ratios of 1:0, 3:1 and 1:1, which were observed for approximately 20 days. To achieve temperatures higher than 15 degrees C above ambient, insulation was required for the reactors. Use of 25-mm thick styrofoam insulation around the entire exterior of the compost reactors and turning of the compost twice a week resulted in sanitizing temperatures (>or=50 degrees C) to be maintained for 8 days in the F:FW=1:1 compost and for 4 days in the F:FW=3:1 compost. In these composts, a reduction of >3 log(10) for E. coli and >4 log(10) for Enterococcus spp. was achieved. The F:FW=1:0 compost, which did not maintain >or=50 degrees C for a sufficiently long period, was not sanitized, as the counts of E. coli and Enterococcus spp. increased between days 11 and 15. This research provides useful information on the design and operation of family-size compost units for the treatment of source-separated faeces and starchy food residues, most likely available amongst the less affluent rural/urban society in Uganda.     

Reclamation and revegetation of fly ash disposal sites - Challenges and research needs

Coal-fired power generation is a principal energy source throughout the world. Approximately, 70-75% of coal combustion residues are fly ash and its utilization worldwide is only slightly above 30%. The remainder is disposed of in landfills and fly ash basins. It is desirable to revegetate these sites for aesthetic purposes, to stabilize the surface ash against wind and water erosion and to reduce the quantity of water leaching through the deposit. Limitations to plant establishment and growth in fly ash can include a high pH (and consequent deficiencies of Fe, Mn, Cu, Zn and P), high soluble salts, toxic levels of elements such as B, pozzalanic properties of ash resulting in cemented/compacted layers and lack of microbial activity. An integrated organic/biotechnological approach to revegetation seems appropriate and should be investigated further. This would include incorporation of organic matter into the surface layer of ash, mycorrhizal inoculation of establishing vegetation and use of inoculated legumes to add N. Leaching losses from ash disposal sites are likely to be site-specific but a sparse number of studies have revealed enriched concentrations of elements such as Ca, Fe, Cd, Pb, and Sb in surrounding groundwater. This aspect deserves further study particularly in the longer-term. In addition, during weathering of the ash and deposition of organic matter during plant growth, a soil will form with properties vastly different to that of the parent ash. In turn, this will influence the effect that the disposal site has on the surrounding environment. Nevertheless, the effects of ash weathering and organic matter accumulation over time on the chemical, physical and biological properties of the developing ash-derived soil are not well understood and require further study.