Water resources issues of small island developing states

The water resources of most small island developing states (SIDS) are often very limited and require special consideration to ensure that they are developed and managed in a sustainable manner. Many small islands, typically located in the humid tropics, have no surface water resources and rely on limited groundwater resources in the form of thin freshwater lenses. The exposed location of small islands makes them particularly vulnerable to natural disasters such as cyclones, floods and droughts. Pollution from population centres and from agricultural and other activities is an increasing problem. This article provides an overview of the water resources of small islands, and the main problems and issues related to water resources. Some suggested solutions, based on practical experiences, are offered for water resource assessment and monitoring programmes, and water resource development. Water resource policy, planning and management issues are also addressed, and suggested approaches for resolving some of the major water resource problems presented.     

堆肥技术及进展

堆肥技术是有机固体废弃物处理和资源化利用的一种有效手段。堆肥系统可分为条垛式、强制通风静态垛式和反应器式三大类。影响堆肥系统运行的主要操作因素有：水分、Ｃ／Ｎ比、调理剂、氧含量、温度和ｐＨ值     

生活垃圾厌氧堆肥产甲烷特性研究

为了更好地利用厌氧处理产生的气体,在介绍模拟厌氧堆肥试验的基础上,对厌氧堆肥产甲烷的基本特性进行了研究。结果表明,在厌氧堆肥开始阶段20d左右,甲烷只有7．8％（质量分数,下同）左右,远远低于32．8％的二氧化碳;而随着反应的进行,二氧化碳呈下降趋势,甲烷先升高后降低,直到反应进行到第70天左右时,甲烷才逐渐高于二氧化碳,片于第90天左右时达到最高值42．0％;此后二氧化碳及甲烷都逐渐降低,但甲烷始终高于二氧化碳。     

Effective removal of antibiotic resistance genes and potential links with archaeal communities during vacuum-type composting and positive-pressure composting

As a major reservoir of antibiotics, animal manure contributes a lot to the augmented environmental pressure of antibiotic resistance genes (ARGs). This might be the first study to explore the effects of different ventilation types on the control of ARGs and to identify the relationships between archaeal communities and ARGs during the composting of dairy manure. Several ARGs were quantified via Real-time qPCR and microbial communities including bacteria and archaea were analyzed by High-throughput sequencing during vacuum-type composting (VTC) and positive-pressure composting (PPC). The total detected ARGs and class I integrase gene (intI1) under VTC were significantly lower than that under PPC during each stage of the composting (p < 0.001). The relative abundance of potential human pathogenic bacteria (HPB) which were identified based on sequencing information and correlation analysis decreased by 74.6% and 91.4% at the end of PPC and VTC, respectively. The composition of archaeal communities indicated that methane-producing archaea including Methanobrevibacter, Methanocorpusculum and Methanosphaera were dominant throughout the composting. Redundancy analysis suggested that Methanobrevibacter and Methanocorpusculum were positively correlated with all of the detected ARGs. Network analysis determined that the possible hosts of ARGs were different under VTC and PPC, and provided new sights about potential links between archaea and ARGs. Our results showed better performance of VTC in reducing ARGs and potential HPB and demonstrated that some archaea could also be influential hosts of ARGs, and caution the risks of archaea carrying ARGs.     

Household Demand for Waste Recycling Services

Municipalities everywhere are coping with increasing amounts of solid waste and need urgently to formulate efficient and sustainable solutions to the problem. This study examines the use of economic incentives in municipal waste management. Specifically, we address the issue of recycling, if and when this waste management option is—on social welfare grounds—a preferred solution.A number of studies have recently assessed the monetary value of the externalities of alternative solid waste management options. In the present context, these subsidies could be interpreted as the implicit value of the benefits from reducing environmental externalities associated with landfilling as perceived by local government authorities. We surmise that the difference between mean households willingness to pay (WTP) for recycling services, via the purchase of a subsidized waste disposal facility, and the above (proxy) value of externalities reflects the difference between private and public perception regarding the negative externality associated with landfilling. We believe that this information is useful in determining the level of subsidization needed (if at all) to sustain any recycling program.The study is unique in the sense that its conclusions are based on revealed household behavior when faced with increased disposal costs, as well as information on WTP responses in hypothetical but related (and, therefore, familiar) scenarios. The article also explores the influence of the subsidization schemes on recycling rates. It was found that with low levels of effort needed to participate in a curbside recycling program, households participation rates are mainly influenced by economic variables and age, and households are willing to pay a higher price for the recycling scheme. When the required effort level is relatively high, however, households would pay a lower price, and the rate is influenced mainly by their environmental commitment and by economic considerations. We found that in both cases a subsidy would be required in order to achieve an efficient level of recycling. The median price that households are willing to pay for recycling devices is found to be about NIS 370 (New Israeli Shekel, approximately $90).     

Composting of vinasse and cotton gin waste by using two different systems

Two composts were obtained by co-composting of a concentrated depotassified beet vinasse and cotton gin waste using two different aeration systems: static aerated pile (forced aeration provided by a blower whom operated in the positive mode) and windrow (turned pile). The composting mixtures were cotton gin trash (55%) and vinasse (45%) (dry weight). In static pile, the total amount of vinasse was added at the beginning of the process whereas, in windrow two additions of vinasse were performed. Differences in temperature changes between both composting systems were found: a faster increase of temperature in the windrow (54 °C at 7 days) than in the static pile (45 °C at 21 days) was observed. Probably in the static pile system, the compaction of the substrates made difficult the correct distribution of the air inside the pile. Moreover, after the second addition of vinasse a new thermophilic phase was started in windrow. The different aeration systems and the way of addition of vinasse could cause differences in organic matter (OM) degradation and in weight (22.6% for the static pile and 26.7% for the windrow) and gas losses during the process. Nevertheless, the composts obtained by the two systems had a high fertilizer value (25.1 g kg⁻¹ N; 3.2 g kg⁻¹ P₂O₅; 21.4 g kg⁻¹ K₂O; C/N8) for compost obtained in static pile and (16.2 g kg⁻¹ N; 3.4 g kg⁻¹ P₂O₅; 16.1 g kg⁻¹ K₂O; C/N 12) for compost obtained in the windrow). A high degree of stability was reached in the final composts. Composting of vinasse with cotton gin waste serves two objectives, disposal of wastes and recycling of waste components.     

Contribution of arbuscular mycorrhiza to soil quality in contrasting cropping systems

The aim of this study was to determine how the potential to rely on arbuscular mycorrhiza (AM) for plant nutrition differs between a conventional and a low-input cropping system in the long term. The roles of fertilisation rate, composting of recycled plant residues and stage of the rotations in the overall impact of the cropping systems on soil quality and AM were also identified. The conventional cropping system with a non-leguminous crop rotation (barley–barley–rye–oat–potato–oat) was fertilised at either full or half the recommended rate. In the low-input cropping system, one year with barley was replaced by clover, and oat was cultivated mixed with pea. Straw and clover were returned to the soil either with or without composting. In the low-input system, biotite and rock phosphate were used to compensate for K and P in the harvested yield, while animal manure was applied at the start only. After 15 years, crop growth and nutrition, AMF colonisation and soil quality were assessed in the field, while the AM contribution to growth and nutrient uptake were determined in a bioassay in a growth chamber. AM functioning made a higher contribution to soil quality in terms of crop performance and environmental benefits in the low-input cropping system than at either fertilisation rate in the conventional system. Halving fertilisation in the conventional system prevented some costs and enhanced some of the benefits of AM in comparison with full fertilisation. However, only the low-input system with composting conclusively favoured AM in comparison with the conventional system. It resulted in the highest percentage colonisation and, in a bioassay with flax and clover, gave a relative average contribution to growth of 27% and to P uptake of 68% in comparison with 4 and 36%, respectively, for the conventional cropping system with full fertilisation. Rye yield was in the low-input system without composting similar to that in the conventional system with full fertilisation, and with composting 87% of the latter one. Incorporation of clover green manure without composting inhibited AM functioning, leading to a temporary loss of AM contribution to crop performance. This effect draws attention to the impact of the form of recycled organic matter on supporting ecosystem services such as nutrient cycling.     

Bioaerosolization behavior along sewage sludge biostabilization

• Aerosolization behavior during a lab-scale sludge biostabilization was determined. • Many pathogenic species were identified to be preferentially aerosolized. • Bioaerosol concentration along the biostabilization ranged from 160 to 1440 cell/m³. • Sludge aerosolization behavior was different with that of other biowaste. Biostabilization is a cost-effective method for the beneficial utilization of sewage sludge. However, during the operation of sludge biostabilization, some microbial species could be released into the atmospheric environment from the solid-phase of sludge easily and present a high risk to human health. This study aimed to evaluate the risk of bioaerosol during sludge biostabilization. We found a total of nine bacterial phyla, one archaeal phylum, and two fungal phyla in the bioaerosol samples. Among them, Proteobacteria, Actinobacteria, Bacteroidetes, and Ascomycota were the dominant phyla. In addition, the bioaerosolization indexes (BI) of prokaryotic phyla and fungal phyla ranged 0–45 and 0–487, respectively. Massilia, Pseudarthrobacter, Pseudomonas, Tremellales spp., and Fusarium were the preferentially aerosolized microbial genera with maximum bioaerosolization indexes of 19962, 10360, 1802, 3055, and 7398. The bioaerosol concentration during the biostabilization ranged from 160 to 1440 cell/m³, and we identified species such as Stenotrophomonas rhizophila and Fusarium graminerum with high bioaerosolization indexes that could be threats to human health. Euryachaeota, which belongs to archaeal phyla, had the highest biostabilization index in our study. We also found that Pseudarthrobacter was the easiest to aerosolize during the sludge biostabilization process.     

A fate model of pathogenic viruses in a composting toilet based on coliphage inactivation

A composting toilet using sawdust as a matrix has the potential to trap pathogens that might occasionally be contained in human feces. Therefore, care should be taken when handling the sawdust. It should also be noted that pathogenic viruses tend to have stronger tolerance than pathogenic bacteria. The fates of several species of coliphages, T4, , Q and MS2, in sawdust were investigated as a viral model. The fates of coliphages were significantly different among them, and they changed in response to temperature and the water content of the sawdust. As the results, T4 coliphage had the strongest tolerance and Q had the weakest one in sawdust. It was estimated the days required to decrease virus to a safe level based on a risk assessment. According to the rates of Q and T4, 15 days and 167 days were required respectively for a safe level of infection risk based on actually operated composting toilet condition. Thus, it was significantly different depending on the species and sawdust conditions.     

Economic and environmental analysis of standard, high efficiency, rainwater flushed, and composting toilets

The current sanitation technology in developed countries is based on diluting human excreta with large volumes of centrally provided potable water. This approach is a poor use of water resources and is also inefficient, expensive, and energy intensive. The goal of this study was to compare the standard sanitation technology (Scenario 1) with alternative technologies that require less or no potable water use in toilets. The alternative technologies considered were high efficiency toilets flushed with potable water (Scenario 2), standard toilets flushed with rainwater (Scenario 3), high efficiency toilets flushed with rainwater (Scenario 4), and composting toilets (Scenario 5). Cost, energy, and carbon implications of these five design scenarios were studied using two existing University of Toledo buildings. The results showed that alternative systems modeled in Scenarios 2, 4, and 5 were viable options both from an investment and an environmental performance perspective. High efficiency fixtures that use potable water (Scenario 2) is often the most preferred method in high efficiency buildings due to reduced water use and associated reductions in annual water and wastewater costs. However, the cost, energy, and CO(2)EE analyses all showed that Scenarios 4 and 5 were preferable over Scenario 2. Cost payback periods of scenarios 2, 4 and 5 were less than 10 years; in the future, increase in water and wastewater services would further decrease the payback periods. The centralized water and wastewater services have high carbon footprints; therefore if carbon footprint reduction is a primary goal of a building complex, alternative technologies that require less potable water and generate less wastewater can largely reduce the carbon footprint. High efficiency fixtures flushed with rainwater (Scenario 4) and composting toilets (Scenario 5) required considerably less energy than direct energy demands of buildings. However, the annual carbon footprint of these technologies was comparable to the annual carbon footprint from space heating. Similarly, the carbon savings that could be achieved from Scenario 4 or 5 were comparable to a recycling program that can be implemented in buildings.