Investigation on removal of p-nitrophenol using a hybridized photo-thermal activated persulfate process: Central composite design modeling

The aim of this work is the study of p-nitrophenol (PNP) removal, as a nitroaromatic compound, using a hybridized photo-thermally activated potassium persulfate (KPS) in a fully recycled batch reactor. Response surface method was used for modeling the process. Reaction temperature, KPS initial dosage and initial pH of the solution were selected as variables, besides PNP degradation efficiency was selected as the response. ANOVA analysis reveals that a second order polynomial model with F-value of 41.7, p-value of 0.0001 and regression coefficient of 0.95 is able to predict the response. Based on the model, the process optimum conditions were introduced as initial pH of 4.5, [KPS]₀ = 1452 mg/L and T = 66 °C. Also experiments showed that using thermolysis and photolysis of the persulfate simultaneously, the role of thermolysis is not considerable. A pseudo first order kinetic model was established to describe the degradation reaction. Operational cost, as a vital industrial criterion, was estimated so that the condition of initial pH of 4.5, [KPS]₀ = 1452 mg/L and T = 25 °C showed the highest cost effective case. Under the preferred mild condition, the process will reach to 84% and 89% of degradation and mineralization efficiencies, after 60 and 120 min, respectively.     

Life-cycle cost-benefit analysis of extensive vegetated roof systems

The built environment has been a significant cause of environmental degradation in the previously undeveloped landscape. As public and private interest in restoring the environmental integrity of urban areas continues to increase, new construction practices are being developed that explicitly value beneficial environmental characteristics. The use of vegetation on a rooftop--commonly called a green roof--as an alternative to traditional roofing materials is an increasingly utilized example of such practices. The vegetation and growing media perform a number of functions that improve environmental performance, including: absorption of rainfall, reduction of roof temperatures, improvement in ambient air quality, and provision of urban habitat. A better accounting of the green roof's total costs and benefits to society and to the private sector will aid in the design of policy instruments and educational materials that affect individual decisions about green roof construction. This study uses data collected from an experimental green roof plot to develop a benefit cost analysis (BCA) for the life cycle of extensive (thin layer) green roof systems in an urban watershed. The results from this analysis are compared with a traditional roofing scenario. The net present value (NPV) of this type of green roof currently ranges from 10% to 14% more expensive than its conventional counterpart. A reduction of 20% in green roof construction cost would make the social NPV of the practice less than traditional roof NPV. Considering the positive social benefits and relatively novel nature of the practice, incentives encouraging the use of this practice in highly urbanized watersheds are strongly recommended.     

Cost-efficiency of rainwater harvesting strategies in dense Mediterranean neighbourhoods

Rainwater harvesting (RWH) presents many benefits for urban sustainability and it is emerging as a key strategy in order to cope with water scarcity in cities. However, there is still a lack of knowledge regarding the most adequate scale in financial terms for RWH infrastructures particularly in dense areas. The aim of this research is to answer this question by analysing the cost-efficiency of several RWH strategies in urban environments. The research is based on a case study consisting of a neighbourhood of dense social housing (600 inhabitants/ha) with multi-storey buildings. The neighbourhood is located in the city of Granollers (Spain), which has a Mediterranean climate (average rainfall 650 mm/year). Four strategies are defined according to the spatial scale of implementation and the moment of RWH infrastructure construction (building/neighbourhood scale and retrofit action vs. new construction). Two scenarios of water prices have been considered (current water prices and future increased water prices under the EU Water Framework Directive). In order to evaluate the cost-efficiency of these strategies, the necessary rainwater conveyance, storage and distribution systems have been designed and assessed in economic terms through the Net Present Value within a Life Cycle Costing approach. The pipe water price that makes RWH cost-efficient for each strategy has been obtained, ranging from 1.86 to 6.42€/m³. The results indicate that RWH strategies in dense urban areas under Mediterranean conditions appear to be economically advantageous only if carried out at the appropriate scale in order to enable economies of scale, and considering the expected evolution of water prices. However, not all strategies are considered cost-efficient. Thus, it is necessary to choose the appropriate scale for rainwater infrastructures in order to make them economically feasible.     

Costs of food waste along the value chain: Evidence from South Africa

In a previous paper (Nahman et al., 2012), the authors estimated the costs of household food waste in South Africa, based on the market value of the wasted food (edible portion only), as well as the costs of disposal to landfill. In this paper, we extend the analysis by assessing the costs of edible food waste throughout the entire food value chain, from agricultural production through to consumption at the household level. First, food waste at each stage of the value chain was quantified in physical units (tonnes) for various food commodity groups. Then, weighted average representative prices (per tonne) were estimated for each commodity group at each stage of the value chain. Finally, prices were multiplied by quantities, and the resulting values were aggregated across the value chain for all commodity groups. In this way, the total cost of food waste across the food value chain in South Africa was estimated at R61.5 billion per annum (approximately US$7.7 billion); equivalent to 2.1% of South Africa’s annual gross domestic product. The bulk of this cost arises from the processing and distribution stages of the fruit and vegetable value chain, as well as the agricultural production and distribution stages of the meat value chain. These results therefore provide an indication of where interventions aimed at reducing food waste should be targeted.     

Life cycle assessment of sewage sludge co-incineration in a coal-based power station

A life cycle assessment was conducted to evaluate the environmental and economic effects of sewage sludge co-incineration in a coal-fired power plant. The general approach employed by a coal-fired power plant was also assessed as control. Sewage sludge co-incineration technology causes greater environmental burden than does coal-based energy production technology because of the additional electricity consumption and wastewater treatment required for the pretreatment of sewage sludge, direct emissions from sludge incineration, and incinerated ash disposal processes. However, sewage sludge co-incineration presents higher economic benefits because of electricity subsidies and the income generating potential of sludge. Environmental assessment results indicate that sewage sludge co-incineration is unsuitable for mitigating the increasing pressure brought on by sewage sludge pollution. Reducing the overall environmental effect of sludge co-incineration power stations necessitates increasing net coal consumption efficiency, incinerated ash reuse rate, dedust system efficiency, and sludge water content rate.     

层次分析法(AHP)在安全经济分析中的应用

简单介绍层次分析法，提出了安全项目的效益层次结构和成本层次结构，应用层次分析法对罐区监控预警系统做了综合评价。     

Adequate air volume in working face after mechanical refrigeration

By analyzing the coal mine working face ventilation and cooling cost after mechanical method is adopted for temperature decrease, the relationship between air volume and ventilation cooling cost was established. And through mathematical analysis and specific applications of the model, the reasonable air volume is determined. With respect to the actual conditions of a coal mine, the air volume is figured out. In order to verify the correctness of the air volume by the new method, the Ansys model of ventilation cooling for the working face is established, and the effect of cooling under the air volume is simulated. The simulation results can meet the mine cooling requirement after being applied in coal mine, the cooling effect and the economic benefit are satisfactory.     

A Comparison of Alternative Strategies for Cost-Effective Water Quality Management in Lakes

Roughly 45% of the assessed lakes in the United States are impaired for one or more reasons. Eutrophication due to excess phosphorus loading is common in many impaired lakes. Various strategies are available to lake residents for addressing declining lake water quality, including septic system upgrades and establishing riparian buffers. This study examines 25 lakes to determine whether septic upgrades or riparian buffers are a more cost-effective strategy to meet a phosphorus reduction target. We find that riparian buffers are the more cost-effective strategy in every case but one. Large transaction costs associated with the negotiation and monitoring of riparian buffers, however, may be prohibiting lake residents from implementing the most cost-effective strategy. An erratum to this article is available at .     

Response to ‘Discussion of the paper “Cost effective policies for alternative distributions of stochastic water pollution” by Gren, Destouni and Tempone’ by Kampas and Adamidis

The note by Kampas and Adamidis (2004; KA) argues for a series of limitations in the paper by [Gren, I.-M., Destouni, G., Tempone R., 2002. Cost effective policies for alternative distributions of stochastic water pollution. Journal of Environmental Management, 66, 145–157.]. We systematically go through and reply to the arguments made by KA, showing that they are all based on misunderstanding of the pollutant load quantities involved in the GDT study and of the scope and purpose of the study. Specifically, the KA arguments are critically based on the invalid assumption of log-normality in individual, basin-scale annual pollutant loads, which are the basic pollutant transport quantities involved in the GDT study. We show that GDT never made, or had physical reason to make any such assumption, whereby the following KA arguments become irrelevant.     

Techno-economic analysis of natural gas combined cycles with post-combustion CO2 absorption, including a detailed evaluation of the development potential

We performed a detailed analysis of the potential future costs and performance of post-combustion CO₂ absorption in combination with a natural gas combined cycle (NGCC). After researching state-of-the-art technology, an Excel model was created to analyze possible developments in the performance of energy conversion, CO₂ capture, and CO₂ compression. The input variables for the three time frames we used were based on literature data, product information, expert opinions, and our own analysis. Using a natural gas price of 4.7 €/GJ, we calculated a potential decrease in the costs of electricity from 5.6 €ct/kWh in the short term to 4.8 €ct/kWh in the medium term and 4.5 €ct/kWh in the long term. The efficiency penalty is calculated to decline from 7.9%-points LHV in the short term to 4.9%-points and 3.7%-points in the medium and long terms, respectively. In combination with NGCC improvements, this may cause an improvement in the net efficiency, including CO₂ capture, from 49% in the short term to 55% and 58% in the medium and long terms, respectively. The total capital costs including capital costs of the NGCC ware calculated to decline from 880 in the short term to 750 and 690 €/kW in the medium and long terms, respectively, with a decline in the incremental capital costs due to capture from 350 in the short term to 270 and 240 €/kW in the medium and long terms, respectively. Finally, the avoidance costs may decline from 45 €/tCO₂ in the short term to 33 €/tCO₂ in the medium term and 28 €/tCO₂ in the long term.