Codisposal of municipal refuse, sewage sludge and marine dredgings for methane production

As marine disposal of sewage sludge and dredged sediments may impose serious adverse effects to marine ecosystems, landfilling seems to be the most feasible method for the final disposal of these wastes. A batch experiment was conducted to study waste degradation and gas production after sewage sludge and marine dredgings were mixed with municipal refuse at 13 different ratios for 36 days. The addition of sludge and dredgings to municipal refuse enhanced gas production, compared with the degradation of refuse or sludge alone. A proper mixing ratio of wastes can also shorten the time to reach the final phase of anaerobiosis. The highest gas production was obtained from the ratio of 75-20-5 (refuse-sludge-dredgings) (wet weight basis). Its average daily gas production rate was 1.42 l kg(-1) waste mixture; methane content was 68.3%. The results indicated that codisposal of the three wastes would be beneficial for energy recovery from landfill gas.     

Effects of leachate recirculation on biogas production from landfill co-disposal of municipal solid waste,sewage sludge and marine sediment

Leachate recirculation is an emerging technology associated with the management of landfill. The impact of leachate recirculation on the co-disposal of three major wastes (municipal solid waste, sewage sludge and sediment dredgings) was investigated using a laboratory column study. Chemical parameters (pH, COD, ammoniacal-N, total-P) and gas production (total gas volume, production rates and concentrations of CH4 and CO2) were monitored for 11 weeks. Leachate recirculation reduced waste-stabilization time and was effective in enhancing gas production and improving leachate quality, especially in terms of COD. The results also indicated that leachate recirculation could maximize the efficiency and waste volume reduction rate of landfill sites.     

烟酰胺降解菌的筛选及其降解特性

采用HPLC对某烟酰胺生产废水的主要成分进行分析,并模拟废水中的主要成分烟酰胺(nicotinamide)的浓度,对以烟酰胺为唯一碳源配制的培养基进行降解实验,获得有较佳降解率和生长能力的菌株YSI-1和YSI-2.结果表明,YSI菌株的混合菌降解效果优于单株菌,混合菌在初始OD600值为0.4,pH为7.0时,对浓度为2000 mg/L的烟酰胺降解2 d的降解率可达32.8%.延长处理时间或提高菌种的初始OD600值,烟酰胺的去除率均有较大的增加.     

Modeling the reaction kinetics of Fenton's process on the removal of atrazine

The degradation of pesticide, atrazine (ATZ), 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine, by Fenton's reagent (FR) was investigated as a function of reagents' concentrations and ratios in a batch reactor. The degradation of ATZ was effectively achieved by hydroxyl radicals, which were generated in the FR process. The decay rates of ATZ and the oxidation capacities of FR were found to depend on the concentrations of hydrogen peroxide and ferrous ion. The removal kinetics of ATZ are initiated by a rapid decay and then followed by a much slower one. After an extended reaction time (5-10 min), the reactions ceased because the Fe(II) and H(2)O(2) were consumed and would be deactivated in the process. A mathematical model was successfully developed to describe the two-stage reaction kinetics by using two simple but critical parameters: the initial ATZ decay rate and the final oxidation capacity of Fenton's process. In general, higher [Fe(II)] or H(2)O(2) concentrations result in faster initial decay rate and higher oxidation capacity. However, the oxidation capacity is more sensitive to the initial [Fe(II)] due to the presence of side reactions as discussed in the paper.     

Physiological aspects of vetiver grass for rehabilitation in abandoned metalliferous mine wastes

Physiological aspects of why vetiver grass (Vetiveria zizanioides L.) can be tolerant to heavy metals and be used as an alternative method for rehabilitation of abandoned metalliferous mine wastelands have been investigated. The results showed that high proportions of lead and zinc (Pb/Zn) tailing greatly inhibited the leaf growth, dry matter accumulation, and photosynthesis of leaves, but stimulated the accumulation of proline and abscisic acid (ABA), and enhanced the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), implying that different mechanisms to detoxify active oxygen species (AOS) existed in different parts of plants. Physiological responses to heavy metal treatments differed greatly between roots and shoots. Nitrogen fertilizer application could greatly alleviate the adverse effects of high proportions of Pb/Zn tailing on vetiver grass growth.     

Herbicides based on 2,4-D: its behavior in agricultural environments and microbial biodegradation aspects. A review

Environmental Science and Pollution Research - One of the main herbicides used in the agricultural environments is 2,4-dichlorophenoxyacetic acid (2,4-D). It is a synthetic plant hormone auxin...     

Interactions of bacteria and fungi on decomposing litter: differential extracellular enzyme activities

Fungi and bacteria are key agents in plant litter decomposition in freshwater ecosystems. However, the specific roles of these two groups and their interactions during the decomposition process are unclear. We compared the growth and patterns of degradative enzymes expressed by communities of bacteria and fungi grown separately and in coexistence on Phragmites leaves. The two groups displayed both synergistic and antagonistic interactions. Bacteria grew better together with fungi than alone. In addition, there was a negative effect of bacteria on fungi, which appeared to be caused by suppression of fungal growth and biomass accrual rather than specifically affecting enzyme activity. Fungi growing alone had a high capacity for the decomposition of plant polymers such as lignin, cellulose, and hemicellulose. In contrast, enzyme activities were in general low when bacteria grew alone, and the activity of key enzymes in the degradation of lignin and cellulose (phenol oxidase and cellobiohydrolase) was undetectable in the bacteria-only treatment. Still, biomass-specific activities of most enzymes were higher in bacteria than in fungi. The low total activity and growth of bacteria in the absence of fungi in spite of apparent high enzymatic efficiency during the degradation of many substrates suggest that fungi provide the bacteria with resources that the bacteria were not able to acquire on their own, most probably intermediate decomposition products released by fungi that could be used by bacteria.     

The partitioning and modelling of pesticide parathion in a surfactant-assisted soil-washing system

Soil sorption of organic pollutants has long been a problematic in the soil washing process because of its durability and low water solubility. This paper discussed the soil washing phenomena over a wide range of parathion concentrations and several soil samples at various fractions of organic content (foc) levels. When parathion dosage is set below the water solubility, washing performance is stable for surfactant concentrations above critical micelle concentration (cmc) and it is observed that more than 90% of parathion can be washed out when dosage is five times lower than the solubility limit. However, such trends change when non-aqueous phase liquids (NAPL) is present in the system. Parathion extraction depends very much on the surfactant dosage but is not affected by the levels of foc in the system. In between the extreme parathion dosage, a two-stage pattern is observed in these boundary regions. Washing performance is first increased with additional surfactant, but the increase slows down gradually since the sorption sites are believed to be saturated by the huge amount of surfactant in the system. A mathematical model has included foc to demonstrate such behavior and this can be used as a prediction for extraction.     

Sustainability of rice production systems: an empirical evaluation to improve policy

An evaluation is needed to monitor the progress of sustainable development (SD) in rice production systems. The purpose of this study is to provide policy inputs, examine the sustainability of rice production, and determine major policy areas. A requisite set of 12 indicators of three dimensions of SD, namely economic, was generated by employing an assemblage of top–down and bottom–up approaches. The data were gathered from farm households’ survey as well as in-depth discussion with stakeholders from the regions that represent irrigated, rain-fed lowland, rain-fed upland, flood-prone, and saline-prone rice-growing ecosystems in Bangladesh. By constructing composite indicators, the results revealed that 44 % of rice growers were economically viable, environmentally sound, and socially developed. The irrigated rice production system was found to be the most sustainable. The path analysis measured the contribution of the indicators to the index, and results highlighted that rice growers’ knowledge, skills, and social networks development, improving land productivity, and integrated nutrient management were essential for promoting sustainable rice production. However, the study findings suggest that pluralistic (i.e., government and non-government) agricultural advisory services can serve as an engine of transition to rice production sustainability in which a multi-year planning and strategy formulation are crucial besides investing in the modernization of extension services. Overall and ecosystem-specific policy implications that emerged from the findings of this study are outlined.     

Perspectives of farmers and tourists on agricultural abandonment in east Lesvos,Greece

Regional Environmental Change - Multi-stakeholder perceptions of landscape changes are increasingly recognized as essential inputs to discussions on future landscape developments, particularly when...