Parametric sensitivity analysis of leachate transport simulations at landfills

This paper presents a case study in simulating leachate generation and transport at a 2000 ton/day landfill facility and assesses leachate migration away from the landfill in order to control associated environmental impacts, particularly on groundwater wells down gradient of the site. The site offers unique characteristics in that it is a former quarry converted to a landfill and is planned to have refuse depths that could reach 100 m, making it one of the deepest in the world. Leachate quantity and potential percolation into the subsurface are estimated using the Hydrologic Evaluation of Landfill Performance (HELP) model. A three-dimensional subsurface model (PORFLOW) was adopted to simulate ground water flow and contaminant transport away from the site. A comprehensive sensitivity analysis to leachate transport control parameters was also conducted. Sensitivity analysis suggests that changes in partition coefficient, source strength, aquifer hydraulic conductivity, and dispersivity have the most significant impact on model output indicating that these parameters should be carefully selected when similar modeling studies are performed.     

Production of lightweight aggregate from industrial waste and carbon dioxide

The concomitant recycling of waste and carbon dioxide emissions is the subject of developing technology designed to close the industrial process loop and facilitate the bulk-re-use of waste in, for example, construction. The present work discusses a treatment step that employs accelerated carbonation to convert gaseous carbon dioxide into solid calcium carbonate through a reaction with industrial thermal residues. Treatment by accelerated carbonation enabled a synthetic aggregate to be made from thermal residues and waste quarry fines. The aggregates produced had a bulk density below 1000 kg/m³ and a high water absorption capacity. Aggregate crushing strengths were between 30% and 90% stronger than the proprietary lightweight expanded clay aggregate available in the UK. Cast concrete blocks containing the carbonated aggregate achieve compressive strengths of 24 MPa, making them suitable for use with concrete exposed to non-aggressive service environments. The energy intensive firing and sintering processes traditionally required to produce lightweight aggregates can now be augmented by a cold-bonding, low energy method that contributes to the reduction of green house gases to the atmosphere.     

The clayey quarry sludge from a waste to a valuable raw material for red ceramics

Journal of Material Cycles and Waste Management - This study aims to evaluate the reuse of clayey quarry sludge generated during the washing process of aggregates in crushing plants as a raw...     

Performance of industrial by-products in controlled low-strength materials (CLSM)

As the construction industry continues to recognise the importance of sustainable development, technologies such as controlled low-strength material (CLSM) have come to the forefront as viable means of safely and efficiently using by-product and waste materials in infrastructure applications. CLSM, also known as flowable fill, can be defined as an engineered backfill material containing fine aggregates, Portland cement, water and a by-product material. CLSM can provide an economically and technically feasible alternative to conventional fill materials because of potential cost savings related to its unique and often superior technical properties. In this present experimental study, three industrial by-products, namely fly ash (FA), rice husk ash (RHA) and quarry dust (QD), were used as constituent materials in CLSM. Mixture proportions were developed for CLSM containing these industrial by-products and were tested in the laboratory for various properties, such as flowability, unconfined compressive strength (UCS), stress-strain behaviour, density, water absorption and volume changes. Comparison between the two pozzolanic materials, namely FA and RHA, for their potential to produce an effective CLSM has been made. It can be observed from the results that by-product materials such as FA, RHA and QD can be successfully used in CLSM. This successful utilization of by-product materials is important to sustainable development and is the focus of this research.     

Strength and durability assessment of concrete containing dolomite quarry waste as fine aggregate

Journal of Material Cycles and Waste Management - The present study focuses on utilizing stockpiled dolomite quarry waste for sustainable and cleaner production of concrete. Natural river sand is...     

Sustainable reuse potential of landfill mining waste retrieved from urban mining sites in South India

Journal of Material Cycles and Waste Management - The present study assesses the reuse potential of landfill mining waste, finer than 2 mm retrieved from the urban mining activity at...     

Constitutive model for municipal solid waste incorporating mechanical creep and biodegradation-induced compression

A constitutive model is proposed to describe the stress–strain behavior of municipal solid waste (MSW) under loading using the critical state soil mechanics framework. The modified cam clay model is extended to incorporate the effects of mechanical creep and time dependent biodegradation to calculate total compression under loading. Model parameters are evaluated based on one-dimensional compression and triaxial consolidated undrained test series conducted on three types of MSW: (a) fresh MSW obtained from working phase of a landfill, (b) landfilled waste retrieved from a landfill after 1.5 years of degradation, and (c) synthetic MSW with controlled composition. The model captures the stress–strain and pore water pressure response of these three types of MSW adequately. The model is useful for assessing the deformation and stability of landfills and any post-closure development structures located on landfills.     

Treatment of the biodegradable fraction of used disposable diapers by co-digestion with waste activated sludge

The results presented in this paper are part of a project aimed at designing an original solution for the treatment of used disposable diapers permitting the recycling of materials and the recovery of energy. Diapers must be collected separately at source and transported to an industrial facility to undergo special treatment which makes it possible to separate plastics and to recover a biodegradable fraction (BFD) made up mainly of cellulose. The methane yield of BFD was measured and found to be 280 ml CH₄/g VS_fed on average. 150 kg of dry BFD can be retrieved from the treatment of one ton of used disposable diapers, representing an energy potential of about 400 kW h of total energy or 130 kW h of electricity. As the treatment process for used diapers requires very high volumes of water, the setting up of the diaper treatment facility at a wastewater treatment plant already equipped with an anaerobic digester offers the advantages of optimizing water use as well as its further treatment and, also, the anaerobic digestion of BFD. The lab-scale experiments in a SBR showed that BFD co-digestion with sewage sludge (38% BFD and 62% waste activated sludge on volatile solids basis) was feasible. However, special attention should be paid to problems that might arise from the addition of BFD to a digester treating WAS such as insufficient mixing or floating particles leading to the accumulation of untreated solids in the digester.     

A bibliometric analysis of anaerobic digestion for methane research during the period 1994–2011

This study uses a bibliometric approach in identifying global research trends related to the anaerobic digestion of biomass for methane production using related literature in the Science Citation Index Expanded database, retrieved from the ISI Web of Science. The data used covers the period 1994–2011. The articles acquired from such literature were concentrated on the general analysis by scientific output, the research performances by countries, institutes, and collaborations, and the research trends by the frequency of author keywords, words in title, words in abstract, and ‘KeyWords plus’. The research outputs of anaerobic digestion for methane had notably increased in the field of environmental sciences, biotechnology and applied microbiology, environmental engineering, energy and fuels, and microbiology, while increased slightly in water resources. The USA with most publications and China with the highest growth rate were compared. Finally, author keywords, words in title and ‘KeyWords plus’ were analyzed contrastively, with the recent hotspots provided.     

The applicability of different waste materials for the production of lightweight aggregates

The applicability of different waste materials for the production of lightweight aggregates has been studied. The following waste materials were investigated: silica sludge, superfluous clay in the quarry, waste glass, and residue from the polishing process of different types of stone. SiC and MnO₂ were selected as foaming agents. Feldspar containing minerals and scrap glass were added in order to lower the softening point of the waste materials. The granules were prepared by mixing together finely ground waste with one or both of the selected foaming agents. The granules were then fired at different temperatures above the softening point of the glassy phase within the temperature range from 1150 to 1220 °C, where the foaming agent degasses, and the resulting gasses remain trapped in the glassy structure. The foaming process was observed by hot-stage microscopy. The properties of the so-obtained granules, such as their apparent density and compressive strength, were determined, and their microstructures were evaluating using SEM and polarizing microscopy.With the addition to clay of polishing residue from granite-like rocks, after firing at 1220 °C homogeneously porous granules with a density down to 0.42 g/cm³ were obtained, whereas with the addition to waste silica sludge of polishing residue from granite-like rocks and waste glass with a foaming agent, after firing at 1220 °C densities from 0.57 to 0.82 g/cm³ were obtained.     

Fuzzy control for the process of heat removal during the composting of agricultural waste

This paper shows the concept and preliminary test of the composting process control with fuzzy logic. The temperature in the compost heap during the process is greater than 80 °C. Because wastes of agricultural origin do not require hygienization, part of the heat can by retrieved, which lowers the temperature in the heap to 55 °C (this is also the optimum temperature for the composting process). The heat retrieved from a compost heap can be used in another place. Therefore, a composting system was developed in which the aeration rate and heat removal rate can be adjusted. There are two goals of this system: maximising the amount of the heat retrieved from the heap and minimising the duration of the composting process. In the preliminary experiments freshly mown grass with 50 % cabbage was used as the compost material. The results show that the fuzzy logic control system functions correctly with respect to calculations. During the study, a median 90 MJ of heat was produced by the bioreactor; the thermophilic phase was shortened to 12 days. There was also a reduction in the emission of ammonia.     

Analytical Modelling Of Inorganic Contaminants In Leachate

The need for estimating the contaminant concentration of leachates from landfills has rapidly become important because of the increased demand for landfilling, causing serious pollution of water bodies in some places. The present study examines the movement of inorganics from waste into leachate in the course of time. Inorganics are discussed in two groups according to their solubilities in water. The first group of inorganics dissolve immediately in water (i.e. at time t = 0). The inorganic compounds of the second group transfer into water over a longer period of time. The mathematical model is based on a porous and well-mixed medium, and on assumptions of dissolution/dilution and mass transfer according to their infiltration rate. The agreement between theoretical and experimental results from laboratory and literature are investigated. After experimental verification, some mathematical relationships to predict the mass transfer coefficient (k) and maximum concentration (C_max) were also investigated.     

Examination of the influence of dissolved halite (NaCl) on the leaching of lead (Pb) from cement-based solidified wastes

The leaching of lead from cement-based solidified waste forms mixed at different water/cement ratios was studied by conducting equilibrium and semi-dynamic leaching tests using deionized water and sodium chloride solutions. The results suggest that leaching of the primary constituents of the cement (calcium, silicon and sulfate) is controlled by solubility equilibria, with increased leaching into chloride solutions due to ionic strength effects. The original porosity of the waste forms increased with water/cement ratio and chloride solutions further increased it as a result of decalcification. Lead leaching was generally low, and appears to be a transport-controlled process, such that leaching correlates positively with porosity.     

平板陶瓷膜回收烟气水热的实验研究

将平板陶瓷膜组成膜组件对烟气水分和余热进行回收,考察了烟气的温度、相对湿度、流速和冷却水温度等参数对膜组件水热回收性能的影响。在实验工况下,水通量和水回收效率随着烟气温度、烟气相对湿度的增加和冷却水温度的降低而上升;水通量随着烟气流速的加快而上升,水回收效率随着烟气流速的加快先上升后降低;膜组件的水通量和水回收效率最高分别可达22.0 kg/(m²·h)和36.3%。平板陶瓷膜回收的热量主要来自烟气潜热,烟气潜热换热量与水通量呈正相关变化趋势。在实验工况下,平板陶瓷膜组件的总传热系数最高为412 W/(m²·℃),高于多通道管式陶瓷膜和单通道管式陶瓷膜。     

Utilization of industrial by-products for the production of controlled low strength materials (CLSM)

Industrial by-products were used for the production of controlled low-strength material (CLSM). CLSM, also known as 'flowable fill' is used as a replacement of compacted soil in cases where the application of the latter is difficult or impossible. The low mechanical requirements (compared with structural concrete) enable the use of industrial by-products for the production of CLSM. In this study cement kiln dust, asphalt dust, coal fly ash, coal bottom ash and quarry waste were tested for the possibility of producing CLSM with large proportions of those wastes. The results showed that in most cases, CLSM with good properties could be made with significant amounts of dust (25-50%w), especially when the dust has some cementing or pozzolanic potential as do fly ash and cement kiln dust.     

非常规气采出水回注环境风险的研究进展

采用水力压裂法开采非常规气时,成分复杂、高盐度的采出水需经简单处理后回注地层。此过程可能引发的环境风险逐渐受到各界关注。针对采出水回注的井位层位、回注水水质等环境风险,综述了室内高温高压静态反应釜实验、动态驱替实验、数值模拟、分析评价等方面的研究进展,在此基础上提出了该领域研究存在的问题和发展方向,为我国采出水回注环境影响研究提供借鉴。     

Groundwater and Nutrient Discharge into Jiaozhou Bay,North China

The health of near shore marine ecosystems has long been a concern because of its importance to coastal areas. Jiaozhou Bay (JZB) is one such marine ecosystem experiencing rapid water quality degradation in the last several decades. From the area surrounding the bay, the nutrients discharged into the bay through surface water and groundwater has been greatly changed. The thickness of the aquifers and the permeability is relatively high, the concentrations of nutrients in the groundwater are generally high, and so the groundwater discharged into JZB is very significant. However, no attempt has ever been made to evaluate the amount of nutrients discharged into the bay area via groundwater. In this study, the cross-section method and water balance method were used to estimate the amount of groundwater and nutrients discharged into JZB via the subsurface. Groundwater was monitored and sampled at aquifers surrounding the bay area, and some previously available data was also analyzed. The results indicated that groundwater from the Baisha Aquifer east of JZB now is the major source of nutrients (nitrate, dissolved SiO₂) being discharged into the bay. The concentrations of nutrients in the groundwater have been increasing with intensive agricultural land use. However, Dagu Aquifer, the largest aquifer north of JZB, only provides limited nutrients to the bay area because of the construction of a low permeability subsurface dam. Historically, during the 1970s to the 1990s, the Baisha Aquifer experienced seawater intrusion due to excessive groundwater withdrawal. The same was true for the Dagu Aquifer from the 1980s to the 1990s. Because of this, no significant nutrients were discharged into the bay.     

Tracking of release and remediation progress from large pipeline break east of Dallas,Texas: Protection of Lake Tawakoni water supply

A gasoline pipeline owned by Explorer Pipeline Company ruptured leaking methyl tertiary butyl ether (MTBE), a gasoline additive, into a creek and lake that the city of Dallas used as a water source. Because of the contamination, the city had to build a pipeline (nine feet in diameter, over two and three‐quarters of a mile in length, and built in three months) to another lake, at a cost of about $9 million. The volume of the release was estimated at 1.7 million gallons of gasoline containing MTBE at 9 percent per volume. Thousands of soil, water, and groundwater samples were taken to track the MTBE plume as it migrated from the spill site, through almost 30 miles of creek and throughout a lake containing 700,000 acre‐feet (228 billion gallons) of water. Four years after the spill, MTBE remains throughout the groundwater system, primarily in the drainage basin along the almost 30 miles of creek. This article focuses on the detailed tracking of all sampling data and the impact that the ongoing threat of MTBE contamination had on the water supplier. © 2006 Wiley Periodicals, Inc.     

臭氧在循环冷却水中缓蚀作用的研究

循环冷却水处理是工业生产中的一个重要环节。臭氧作为单一的水质稳定剂在循环冷却水中具有缓蚀作用。研究结果表明：吸附在金属表面的臭氧使金属表面从活化腐蚀状态转变为钝化状态,使金属腐蚀电位由活化电位区跃变到钝化电位区,阻止金属的溶解;同时氧的传质速率加快,也可以降低由于浓差极化所产生的腐蚀作用;对于未经预膜处理的金属,臭氧改变金属表面状态,形成一层氧化钝化膜,从而起到了缓蚀作用。     

Water movement through an experimental soil liner

A field-scale soil liner was constructed to test whether compacted soil barriers in cover and liner systems could be built to meet the U.S. EPA saturated hydraulic conductivity requirement (⩽ 1 × 10⁻⁷ cm s⁻¹). The 8 × 15 × 0.9 m liner was constructed in 15 cm compacted lifts using a 20,037 kg pad-foot compactor and standard engineering practices. Water infiltration into the liner has been monitored for one year. Monitoring will continue until water break through at the base of the liner occurs. Estimated saturated hydraulic conductivities were 2.5 × 10⁻⁹, 4.0 × 10⁻⁸, and 5.0 × 10⁻⁸ cm s⁻¹ based on measurements of water infiltration into the liner by large- and small-ring infiltrometers and a water balance analysis, respectively.Also investigated in this research was the variability of the liner's hydraulic properties and estimates of the transit times for water and tracers. Small variances exhibited by small-ring flux data suggested that the liner was homogeneous with respect to infiltration fluxes. The predictions of water and tracer breakthrough at the base of the liner ranged from 2.4–12.6 y, depending on the method of calculation and assumptions made. The liner appeared to be saturated to a depth between 18 and 33 cm at the end of the first year of monitoring. Transit time calculations cannot be verified yet, since breakthrough has not occurred. The work conducted so far indicates that compacted soil barriers can be constructed to meet the saturated hydraulic conductivity requirement established by the U.S. EPA.