Experimental investigations on regeneration energy and energy management strategy in series hydraulic/electric synergy system

This research work draws an insight into the experimental investigations on a series hydraulic/electric synergy system—a green transportation system. An experimental test rig of the system with all necessary sensors and instrumentation has been developed to study the energy saving through hydraulic regenerative braking. The effect of various system parameters, such as braking time, maximum accumulator pressure, pre-charge pressure of hydro-pneumatic accumulator, volumetric displacement of the hydraulic master pump, and hydraulic regeneration pump on the quantum of regeneration energy, was analyzed. In addition, an AMESim model of the real-time experimental test rig has been developed and validated with experimental results. A set of five different experimental designs (parameter variations) of the system is defined with the available standard component sizes. The best design is selected of the available experimental designs based on the maximum hydraulic regeneration energy and regeneration efficiency. It was observed that the selected design has an energy efficiency of 13.3% and a regeneration efficiency of 43.8%. An accumulator-centric control strategy for energy management is developed and implemented on the experimental test rig configured with the selected design. The effectiveness of the control strategy is tested through experiments and simulation on the developed test rig.     

Some happy,others sad: exploring environmental justice in solid waste management in Kinshasa,The Democratic Republic of Congo

This paper explores the concept of environmental justice (EJ) in solid waste management (SWM) in Kinshasa, the Democratic Republic of Congo (DRC). It evaluates the extent to which EJ occurs in SWM and discusses the factors accounting for this state of affairs. The paper examines the relevant theoretical framework(s) and mechanisms that would facilitate the attainment of EJ in Kinshasa. It is argued that solid waste (SW) often ends up in the poorest and least powerful communities in the cities of the DRC. A qualitative research methodology, which includes exhaustive critical review of the literature, system analysis, reflections from best practices through case studies and discussion with stakeholders, was used for this study. Findings revealed that SWM in Kinshasa is a duty entrusted to publicly-funded municipal authorities. There are evidences of a clear divide between the rich and poor neighbourhoods in the manner SW is managed. This is an inequality that has only recently begun to be recognised as injustice practices in SWM. It is argued that a politico-cultural mechanism on remedying SWM inequities could enable changes that will address EJ in Kinshasa. Such a solution will go directly against the prevailing notion “some happy, others sad”.     

The Financial Impact of Different Stormwater Fee Types: A Case Study of Two Municipalities in Virginia

Eight stormwater user fees (SUFs) were applied to the City of Roanoke and the Town of Blacksburg, Virginia, to determine the effect each has on how land use type impacts the sources of revenue. Roanoke is larger and includes more industrial areas, but less multifamily impervious areas than Blacksburg, which translates differently in the SUFs. Residential parcels comprise the highest percentage of the revenue in all eight SUFs in Blacksburg and four in Roanoke. For both municipalities, two specific SUFs consistently comprised the highest percentage burden for residential homeowners while three other SUFs demonstrated the highest burden for commercial parcels. Open space parcels contain little impervious area, yet account for up to 27% of the revenue in the Blacksburg Area fee structure. Industrial parcels comprise more revenue in Roanoke, averaging 10.1‐4.5% in Blacksburg. Fee types that are easier to administer (e.g., Flat fees) may not fully represent the stormwater contribution from the parcels. SUF types that more accurately represent the stormwater burden on the municipality are also more administratively intensive and are more variable with fee factors.     

Accretion of Nutrients and Sediment by a Constructed Stormwater Treatment Wetland in the Lake Tahoe Basin

This unique study evaluates the cumulative 16‐year lifetime performance of a wetland retention basin designed to treat stormwater runoff. Sediment cores were extracted prior to basin excavation and restoration to evaluate accretion rates and the origin of materials, retention characteristics of fine particulate matter, and overall pollutant removal efficiency. The sediment and organic layers together accreted 3.2 cm of depth per year, and 7.0 kg/m²/yr of inorganic material. Average annual accretion rates in g/m²/yr were as follows: C, 280; N, 17.7; P, 3.74; S, 3.80; Fe, 194; Mn, 2.68; Ca, 30.8; Mg, 30.7; K, 12.2; Na, 2.54; Zn, 0.858; Cu, 0.203; and B, 0.03. The accretion of C, N, P and sediment was comparable to nonwastewater treatment wetlands, overall, and relatively efficient for stormwater treatment wetlands. Comparison of particle size distribution between sediment cores and suspended solids in stormwater runoff indicated the wetland was effective at removing fine particles, with sediment cores containing 25% clay and 56% silt. A majority of the accretion of most metals and P could be attributed to efficient trapping of allochthonous material, while over half the accretion of C and N could be attributed to accumulation of autochthonous organic matter. Stormwater treatment was shown to be effective when physical properties of a retention basin are combined with the biological processes of a wetland, although sediment accretion can be relatively rapid.     

Hot,Salty Water: A Confluence of Issues in Managing Stormwater Runoff for Urban Streams

Research increasingly highlights cause and effect relationships between urbanization and stream conditions are complex and highly variable across physical and biological regions. Research also demonstrates stormwater runoff is a key causal agent in altering stream conditions in urban settings. More specifically, thermal pollution and high salt levels are two consequences of urbanization and subsequent runoff. This study describes a demonstration model populated with data from a high gradient headwaters stream. The model was designed to explain surface water‐groundwater dynamics related to salinity and thermal pollution. Modeled scenarios show long‐term additive impacts from salt application and suggest reducing flow rates, as stormwater management practices are typically designed to do, have the potential to greatly reduce salt concentrations and simultaneously reduce thermal pollution. This demonstration model offers planners and managers reason to be confident that stormwater management efforts can have positive impacts.     

Detention Outlet Retrofit Improves the Functionality of Existing Detention Basins by Reducing Erosive Flows in Receiving Channels

By discharging excess stormwater at rates that more frequently exceed the critical flow for stream erosion, conventional detention basins often contribute to increased channel instability in urban and suburban systems that can be detrimental to aquatic habitat and water quality, as well as adjacent property and infrastructure. However, these ubiquitous assets, valued at approximately $600,000 per km² in a representative suburban watershed, are ideal candidates to aid in reversing such cycles of channel degradation because improving their functionality would not necessarily require property acquisition or heavy construction. The objective of this research was to develop a simple, cost‐effective device that could be installed in detention basin outlets to reduce the erosive power of the relatively frequent storm events (~ < two‐year recurrence) and provide a passive bypass to maintain flood control performance during infrequent storms (such as the 100‐year recurrence). Results from a pilot installation show that the Detain H₂O device reduced the cumulative sediment transport capacity of the preretrofit condition by greater than 40%, and contributed to reduced flashiness and prolonged baseflows in receiving streams. When scaling the strategy across a watershed, these results suggest that potential gains in water quality and stream channel stability could be achieved at costs that are orders of magnitude less than comparable benefits from newly constructed stormwater control measures.     

A decision framework for possible remediation of contaminated sediments in the River Kymijoki, Finland

Background, aim, and scope  The paper describes the spatial contamination of the River Kymijoki, South-Eastern Finland, and the coastal region of the Gulf of Finland with PCDD/Fs and mercury. The findings of ecotoxicologial and human health studies are also reported, including environmental and human risk assessments. Sediments from the River Kymijoki, draining into the Gulf of Finland, have been heavily polluted by the pulp and paper industry and by chemical industries. A wood preservative, known as Ky-5, was manufactured in the upper reaches of the river between 1940 and 1984 causing severe pollution of river sediments with polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF). Moreover, the sediments have been polluted with mercury (Hg) from chlor-alkali production and the use of Hg as a slimicide in pulp and paper manufacturing. Materials and methods  An extensive sediment survey was conducted as well as sediment transport modeling, toxicity screening of sediment invertebrates, and a survey of contaminant bioaccumulation in invertebrates and fish. Studies on human exposure to PCDD/Fs and the possible effects on hypermineralization of teeth as well as an epidemiological study to reveal increased cancer risk were also conducted. An assessment of the ecological and human health risks with a null hypothesis (no remediation) was undertaken. Results  The sediment survey revealed severe contamination of river and coastal sediments with PCDD/Fs and Hg. The total volume of contaminated sediments was estimated to reach 5 × 10⁶ m³ and hot spots with extremely high concentrations (max 292,000 ng g⁻¹ or 1,060 ng I-TEQ g⁻¹ d.w.) were located immediately downstream from the pollution source (approximately 90,000 m³). Sediment contamination was accompanied by changes in benthic assemblages, but direct effects were masked by many factors. The fish showed only slightly elevated PCDD/F levels in muscle, but orders of magnitude higher in the liver compared with reference freshwater sites and the Baltic Sea. The concentrations in human fat did not reveal high human exposure in the Kymijoki area in general and was lower than in sea fishermen. The relative risk for total cancer among farmers was marginally higher (RR = 1.13) among those living close to the river, compared with farmers living further away, and the possibility of increased cancer risk cannot be ruled out. A conservative risk assessment revealed that the present probability of exceeding the WHO upper exposure limit of 4 pg WHO-TEQ kg⁻¹ d⁻¹ for PCDD/Fs and DL-PCBs was 6%. The probability of exceeding the WHO limit value of 0.23 μg kg⁻¹ d⁻¹ for methyl mercury was estimated to be notably higher at 62%. Based on these studies and the estimated risks connected with different remediation techniques a general remediation plan with cost benefit analysis was generated for several sub-regions in the river. Dredging, on-site treatment, and a close disposal of the most contaminated sediments (90,000 m³) was suggested as the first phase of the remediation. The decision regarding the start of remediation will be made during autumn 2008. Conclusions  The sediments in the River Kymijoki are heavily polluted with PCDD/Fs and mercury from earlier chlorophenol, chlor-alkali, and pulp and paper manufacturing. A continuous transport of contaminants is taking place to the Gulf of Finland in the Baltic Sea. The highly increased PCDD/F and Hg levels in river sediments pose an ecotoxicological risk to benthic fauna, to fish-eating predators and probably to human health. The risks posed by mercury exceed those from PCDD/Fs and need to be evaluated for (former) chlor-alkali sites and other mercury releasing industries as one basis for remediation decision making. Recommendations and perspectives  The studies form the basis of a risk management strategy and a plan for possible remediation of contaminated sediments currently under consideration in the Southeast Finland Regional Environment Centre. It is recommended that a detailed restoration plan for the most seriously contaminated areas should be undertaken. Based on current knowledge, the restoration of the whole river is not feasible, considering the current risk caused by the contaminated sediment in the river and the costs of an extensive restoration project. The experiences gained in the present case should be utilized in the evaluation of PCDD/F- and mercury-contaminated sites in other countries. The case demonstrates that the historic reservoirs are of contemporary relevance and should be addressed, e.g., in the national implementation plans of the Stockholm Convention. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Management-oriented sensitivity analysis for pesticide transport in watershed-scale water quality modeling using SWAT

The Soil and Water Assessment Tool (SWAT) was calibrated for hydrology conditions in an agricultural watershed of Orestimba Creek, California, and applied to simulate fate and transport of two organophosphate pesticides chlorpyrifos and diazinon. The model showed capability in evaluating pesticide fate and transport processes in agricultural fields and instream network. Management-oriented sensitivity analysis was conducted by applied stochastic SWAT simulations for pesticide distribution. Results of sensitivity analysis identified the governing processes in pesticide outputs as surface runoff, soil erosion, and sedimentation in the study area. By incorporating sensitive parameters in pesticide transport simulation, effects of structural best management practices (BMPs) in improving surface water quality were demonstrated by SWAT modeling. This study also recommends conservation practices designed to reduce field yield and in-stream transport capacity of sediment, such as filter strip, grassed waterway, crop residue management, and tailwater pond to be implemented in the Orestimba Creek watershed.     

Financial assurance and mine closure: Stakeholder expectations and effects on operating decisions

Financial assurance is increasingly seen as a means to ensure orderly, clean and lasting closure of mines. Broadly interpreted, “closure” requires leaving viable ecosystems on mining lands that are compatible with a healthy environment and with human activities, that have low hazard, and that encompass measures to prevent ongoing pollution from the site in the long-term. Financial assurance encompasses environmental surety instruments that protect the government and public in the event a mining company cannot meet its reclamation or rehabilitation obligations. As such, financial assurance is in essence the money available for closure of the mine in the case when the mine owner is not available to perform the work. A general trend towards greater environmental concern among social stakeholders in mining further serves to focus attention on policies and practices that can actually “assure” financial assurance.Financial assurance is also perceived as a means to address closure-related challenges that are increasing in number as well as diversity. Notably, current trends involve a shift towards a greater focus to the societal aspects of mine closure rather than just the ecological. The use of financial assurance, however, also raises some fundamental questions about how assurance mechanisms influence mining operations and the relationship between mining operations and their surroundings. This paper examines both the internal effect of a variety of financial assurance approaches on mining operations—in particular the manner in which environmental and social concerns are addressed by mining firms, and the almost inevitable tension between some form of financial provision for closure on the one hand, and governmental expectations of tax revenue on the other. As a major argument for supporting the conduct of mining is that state revenues from the extractive industries supply monies for the building of human and infrastructural capital, this second area of tension also has strong social and developmental overtones.     

Assessing the long-term supply risks for mineral raw materials—a combined evaluation of past and future trends

This paper develops a method for identifying and assessing long-term supply risks for mineral raw materials. The method is based on a combined evaluation of past and future supply and demand trends. By analysing raw material boom and bust cycles over the past 50 years, we have quantified indicators and defined benchmarks for identifying critical market situations. By applying the method, risks for supply shortage may be identified at an early stage. In addition, a numerical evaluation model has been developed for better comparison between various mineral raw materials. Compared to other assessment methods this method uses specific benchmarks for each raw material to better assess supply risks. The method is embedded within a systematic and comprehensive analytical approach.