Environmental Engineering

The interaction between a power system and a wind-farm can be studied using either a simplified ‘aggregated’ or a complex ‘detailed’ model. The detailed-model results compare well with the actual, therefore, provided that both models have similar dynamic characteristics, the aggregated model provides a rapid and cost-effective way of representing large wind-farms in power system dynamic studies. A brief overview of wind-farm aggregation methods is given and their application in power systems analysis is discussed. Aggregation techniques are then applied to a wind-farm with thirty wind turbines. It is shown that the aggregation of the swing equation and equivalent representation of network and generator impedances can be used for aggregated representation of fixed speed wind turbines. A similar approach applied to the d-and q-axis controller of a doubly-fed induction generator (DFIG) failed initially to provide satisfactory dynamic characteristics with the aggregated model. Consequen...

Wastes are usually thought of as unwanted or unusable materials. Waste is any substance which is discarded after primary use, or considered worthless, defective, and of no use. The term is often subjective, as not every application has identical raw material requirements and sometimes even objectively inaccurate. A starting point towards managing waste is the division in basic categories, ranging from municipal and agricultural waste to radioactive and explosive waste. Through proper collection of municipal solid waste, very important metals and other valuable sources can be recovered and used in new products, thus achieving significantly lower production cost and environmental impact. Success stories in waste management are reported in countries around the world. These typically showcase optimal waste transformation to wealth. Furthermore, applied waste management methods are specified. These actions should be adapted by every organization handling waste. At a managerial level, the...

Along with economic development, urbanization will generate a large amount of solid waste and put pressure on the waste management systems in developing countries. Face-to-face interview methods were used to investigate the current status of construction and demolition waste (CDW) management (collection, transportation, treatment, and storage) as well as reveal attitudes of governmental agencies and enterprises towards CDW recycling and recycled material products in Hai Phong City, Vietnam. Waste generation rates (WGRs) of the works were also determined by site surveys and as-built drawings method of typical old buildings to be demolished and two licensed new construction works. WGRs of 34.5 kg/m2 and 758 kg/m2 were identified during the construction and demolition of small private houses, respectively, while WGRs at public house demolition sites were 1053 kg/m2. To effectively manage the CDW, the gross floor area of new construction work was estimated by a multiple regression equat...

Present work reports the application of a composite of ZIF-67/rGO for the simultaneous detection of traces of lead and cadmium via square wave anodic stripping voltammetry (SWASV) technique. For this, graffoil sheets were modified with synthesized composite for the electrode fabrication [(ZIF-67/rGO)/Graffoil] for its use in sensing studies. The SWASV response of (ZIF-67/rGO)/Graffoil electrode was optimized against deposition potential (-1.0 V) and time (350 s), required for the accumulation of metal ions onto the sensor electrode. The performance of the sensing electrode was then evaluated for lead (Pb2+) and cadmium (Cd2+) ions at various concentrations. The sensor displayed linear response in a wide concentration range of 5-100 ppb. The peak current of the electrode was found to be shifted towards the higher potential at higher metal ion concentrations. Based on the response measured, the limit of detection (LOD) of the fabricated sensor has been estimated and found to be 5 and ...

A study was conducted to estimate the possible environmental impacts arising from the generation of bioethanol from oil palm frond sugar juice in a theoretical oil palm based biorefinery model. A life cycle assessment (LCA) with the gate-to-gate approach was performed with the aid of SimaPro version 8.0 whereby ten impact categories were evaluated. The scope included frond collection and transportation, frond sugar juice extraction, and bioethanol fermentation and purification. Evaluation on the processes involved indicated that fermentation contributed to the environmental problems the most, with a contribution range of 52% to 97% for all the impact categories. This was due to a substantial usage of nutrient during this process, which consumes high energy for its production thus contributing a significant burden to the surrounding. Nevertheless, the present system offers a great option for biofuel generation as it utilizes sugar juice from the readily available oil palm waste. Not ...

InthispapertheexperimentalstudiesontheresidualyieldandultimatestrengthofFe500gradereinforcing steelatelevated temperatureisstudied.Fortheexperimentalstudy, Fe500reinforcing steel bars wereex posed to d ifferent temperature sranging from200?C to 700? Cwithanintervalof 100?Cfordifferentsoakingperiods.Afterattainingthe targettemperaturetherods wereretained in thefurnacefor30,60 and120minutes soaking period. After the fire exposure of rods, the rods were cooled to room temperature. Thenthetensilestrength testof thereinforcingsteelwascarried out.

Water security and safety is of vital concern in arid and semiarid regions of Kenya. Potable water accessibility and supply is limited due to fluctuating climatic conditions and environmental pollution that lower the wholesomeness of most water sources. The aim of this study was to establish the suitability of these water sources for drinking and use in industrial food processing by the small and medium enterprises (SME’s). The aim of this study was to establish suitability of these water sources for drinking and use in industrial food processing by the small and medium enterprises (SME’s). A total of 60 surface and ground water sources samples were purposively collected aseptically from the four administrative units (Ngare Mara, LMD, Leparua, and Wabera) of Isiolo County. ISO 16649-3, 688-2, 7937, 9308-1, and 18744 were used for enumeration of E.coli, Staphylococcus aureus, Clostridium pafringens, Coliforms, and cysts. Highest mean Clostridium pafringens counts in ground and surfac...

Nile perch (Lates niloticus) viscera oil was extracted by wet rendering method and refined by neutralization, deodorization and winterization. After winterization, the oil was decanted and separated by filtration into a low melting point fraction (LMPF) and a high melting point fraction (HMPF). The two fractions were used to carry out storage stability study. Each fraction was stored at room temperature (19 – 23oC) for a period of 20 weeks in transparent and amber colored glass containers. The oil fractions were subjected to quality tests to assess their storage stability. The effects of package color and storage duration were assessed by analyzing for the content of free fatty acids (FFA) as oleic acid and the peroxide value (PV) at the beginning of storage and at intervals of two weeks during storage. The resulting data were subjected to statistical analysis (p ≤ 0.05) using GenStat software, 13th edition. There was a general increase in FFA and PV, with significant differences be...

Risers are very important component of deep sea-bed mining. Unfortunately, risers have high risks of damage because they are exposed to harsh environmental conditions such as a current, pressure, high tension and vortex induced vibration. Therefore, it is very significant to retain riser’s performance and to detect damage before the riser failure is occurred. A main objective of this paper is to propose a structural health monitoring technique to detect damage of a toptensioned riser. In this paper, the top-tensioned finite element (FE) model is considered as an analytical model of the riser, and a vibrationbased damage detection method with responses from damaged model is proposed. The present method consists of a FE model updating and damage index method. In order to accomplish the goal of this study, first, a sensitivity-based FE model updating method using the natural frequencies and the zero frequencies is introduced. Second, modal parameters of the top-tensioned riser are esti...

Two explicit schemes of the finite difference method are presented and analyzed in the paper. The applicability of the Lax-Wendroff and McCormack schemes for modeling unsteady rapidly and gradually varied open channel flow is investigated. For simulation of the transcritical flow the original and improved McCormack scheme is used. The schemes are used for numerical solution of one dimensional Saint-Venant equations describing free surface water flow. Two numerical simulations of flow with different hydraulic characteristics were performed - the first one for the extreme flow of the dam-break type and the second one for the simplified flood wave propagation problem. The computational results are compared to each other and to arbitrary solutions.

The paper focuses mainly on laboratory investigations of transient and transcritical flow in a single pipe of a sewer system. The aim of this paper is to present a comparison between pressure values calculated by an improved McCormack scheme and those measured at the hydraulic laboratory of the Gdańsk University of Technology, which were observed inside a pipe in an experiment for water flow with pressurization. The analysis proves that the numerical approach applied to flow simulation is a sufficiently accurate and reliable technique for predicting the basic parameters of storm sewer flow

Empirical frequency distributions of multiplicative cascade weights, or breakdown coefficients, at small timescales are analyzed for 5-min precipitation time series from four gauges in Germany. It is shown that histograms of the weights, W, are strongly deformed by the recording precision of rainfall amounts. A randomization procedure is proposed to statistically remove the artifacts due to precision errors in the original series. Evolution of the probability distributions of W from beta-like for large timescales to combined beta-normal distribution with a pronounced peak at W ≈ 0.5 for small timescales is observed. A new 3N-B distribution built from 3 separate normal, N, distributions and one beta, B, distribution is proposed for reproduction of the empirical histograms of W at small timescales. Parameters of the 3N-B distributions are fitted for all gauges and analyzed timescales. Microcanonical cascades models with a generator based on 3N-B distributions are developed and their p...

Purpose The textiles industry is a substantial contributor to environmental impacts through the production, processing, use, and end-of-life of garments. Wool is a high value, natural, and renewable fibre that is used to produce a wide range of garments, from active leisure wear to formal wear, and represents a small segment of the global fashion industry. Woollen garments are produced by long, global value chains extending from the production of ‘greasy’ wool on sheep farms, through processing to garment make-up, retail, consumer use, and end-of-life. To date, there have been limited life cycle assessment (LCA) studies on the environmental impacts of the full supply chain or use phase of garments, with the majority of wool LCA studies focusing on a segment of the supply chain. This study aimed to address this knowledge gap via a cradle-to-grave LCA of a woollen garment. Methods This study investigated greenhouse gas (GHG) emissions, fossil fuel energy, and water stress associated w...

O planejamento da expansão da capacidade de sistemas elétricos visa garantir o fornecimento futuro de energia elétrica. A busca por esse objetivo deve ser feita tendo em vista critérios como custos, tecnologias disponíveis, confiabilidade e impactos ambientais. No presente trabalho, o foco são os objetivos de mínimos custos e mínimas emissões de gases de efeito estufa, da geração elétrica. No contexto global atual, esse planejamento representa um grande desafio. Sendo uma atividade de grande importância para o desenvolvimento dos países, envolve, além das incertezas próprias da atividade, também as incertezas das políticas energéticas, as quais dependem de outras agendas políticas da administração em turno. Além disso, uma vez que a geração de energia é baseada em muitos casos em recursos naturais sensíveis às condições climáticas, o processo de planejamento também deve lidar com a incerteza da mudança climática. Dessa forma, são necessários planos flexíveis capazes de antecipar pos...