Pollution Management in the Twentieth Century

A literature review is presented on the evolution of water pollution management and its impact on land pollution from 1900 to 2000 within an hypothesis of whether we could have done more, sooner. Stream pollution science in the context of the fundamental sanitary engineering concepts of reasonable use and assimilative capacity is examined in light of evolving regulatory frameworks from the early 1900s, when regulation and standards were mostly lacking, to the zero discharge goals and comprehensive federal command/control regulations of the late Twentieth Century. Details on the interplay through the years of improving environmental analytical chemistry, environmental quality definitions, wastewater control technologies, municipal–industrial wastewater differences, and regulatory will/diligence are provided. The pressure exerted on land and groundwater pollution as a result of water pollution control is emphasized. The author’s conclusion is that more effective, faster pollution control evolution would have been difficult.     

Shear Strength Parameters of Municipal Solid Waste with Leachate Recirculation

The objective of this study was to characterize relative changes in waste shear strength parameters during waste decomposition. Twelve direct shear tests (100?mm diameter by 50?mm thickness) were performed on waste specimens ranging from fresh to well-decomposed residential refuse. In addition, nine direct shear tests were performed on selected waste components including fresh paper, partially decomposed refuse, and plastics. Results indicate that the friction angle of refuse decreased with decomposition. As refuse decomposed, the plastic content increased, which contributed to a decrease in friction angle as the friction angle of plastics is 18–19° as compared to 33° for fresh shredded waste. The extent of refuse decomposition was characterized by the cellulose plus hemicellulose to lignin ratio [(C+H)/L]. The measured friction angle decreased from 32 to 24° as (C+H)/L decreased from 1.29 to 0.25. The shearing pattern for decomposed refuse showed a peak, followed by residual, which was then followed by a steady increase in shear stresses with displacement; the final rate of increase was similar to that observed in fresh paper specimens. Results from this work were comparable to data from previous reports, though it is important to characterize the extent of solids decomposition for a valid comparison with published studies.     

Hydraulic Conductivity of Geosynthetic Clay Liners Exhumed from Landfill Final Covers

Samples of geosynthetic clay liners (GCLs) from four landfill covers were tested for water content, swell index, hydraulic conductivity, and exchangeable cations. Exchange of Ca and Mg for Na occurred in all of the exhumed GCLs, and the bentonite had a swell index similar to that for Ca or Mg bentonite. Hydraulic conductivities of the GCLs varied over 5 orders of magnitude regardless of cover soil thickness or presence of a geomembrane. Hydraulic conductivity was strongly related to the water content at the time of sampling. Controlled desiccation and rehydration of exhumed GCLs that had low hydraulic conductivity (10?9?to?10?7?cm/s) resulted in increases in hydraulic conductivity of 1.5–4 orders of magnitude, even with overburden pressure simulating a 1-m-thick cover. Comparison of these data with other data from the United States and Europe indicates that exchange of Ca and/or Mg for Na is likely to occur in the field unless the overlying cover soil is sodic (sodium rich). The comparison also shows that hydraulic conductivities on the order of 10?6?to?10?4?cm/s should be expected if exchange occurs coincidently with dehydration, and the effects of dehydration are permanent once the water content of the GCL drops below approximately 100%. Evaluation of the field data also shows that covering a GCL with a soil layer 750–1,000?mm thick or with a geomembrane overlain by soil does not ensure protection against ion exchange or large increases in hydraulic conductivity.     

Unit Weight Determination of Landfill Waste Using Sonic Drilling Methods

The total unit weight of waste in a 40.5?ha landfill, up to 34?m thick, was estimated based on tube samples taken from borings made using sonic drilling technology. The waste’s unit weight was needed for input into slope stability calculations, which were part of the landfill’s closure design. The sonic drill was capable of penetrating and obtaining samples of all types of materials in the landfill. No significant correlation of waste unit weight, with depth, was found. Instead, the waste samples’ constituents were observed to have the greatest effect on their unit weights. The site also offered the unique opportunity to back-calculate the waste’s overall unit weight using a numerical model, and knowledge of the in situ stresses in the underlying clay as determined by oedometer testing. These calculations indicated that samples taken, using sonic drilling, gave a good a approximation of the waste’s overall unit weight at each boring location.     

Evaluation of Strength Properties of Polypropylene-Based Polymers in Simulated Landfill and Oven Conditions

Polymeric films and fibers are used extensively in industrial and personal products. Many of these products are intended to be disposable and, after initial use, are disposed in landfills that are increasingly expensive and limited. Proprietary additives are being promoted to enhance the biodegradation of polypropylene (PP) and related materials. A test was run on samples of diapers containing PP in simulated landfills and in convection ovens over a period of 52?weeks. Samples in the oven treatment lost all strength properties in less than 27?weeks. Back sheet and cuff samples in the landfill lost insignificant (P<0.05) strength under landfill conditions over 52?weeks. Statistics show significant differences (P<0.05) in strength and sample percent elongation during testing for time, temperature, and time-temperature interactions for both the oven and landfill tests. The study led to the conclusion that the polypropylene additive was efficacious for programmable destruction in an oxidative environment but not efficacious in an anaerobic environment.     

Compaction Characteristics of Municipal Solid Waste

Compaction characteristics of municipal solid waste (MSW) were determined in the laboratory and in the field as a function of moisture content, compactive effort, and seasonal effects. Laboratory tests were conducted on manufactured wastes using modified and 4X modified efforts. Field tests were conducted at a MSW landfill in Michigan on incoming wastes without modifications to size, shape, or composition, using typical operational compaction equipment and procedures. Field tests generally included higher efforts and resulted in higher unit weights at higher water contents than the laboratory tests. Moisture addition to wastes in the field was more effective in winter than in summer due to dry initial conditions and potential thawing and softening of wastes. The measured parameters in the laboratory were γdmax-mod = 5.2?kN/m3, wopt-mod = 65%, γdmax-4×mod = 6.0?kN/m3, and wopt-4×mod = 56%; in the field with effort were γdmax-low = 5.7?kN/m3, wopt-low = 70%; γdmax-high = 8.2?kN/m3, and wopt-high = 73%; and in the field with season were γdmax-cold = 8.2?kN/m3, wcold = 79.5%, γdmax-warm = 6.1?kN/m3, and wwarm = 70.5%. Soil compaction theory was reasonably applicable to wastes with the exception that the Gs of waste solids increased with compactive effort resulting in steep degree of saturation curves and low change in wopt between efforts. Moisture addition to wastes during compaction increased the workability, the unit weight, and the amount of incoming wastes disposed, and reduced the compaction time. The combined effects have significant environmental and economic implications for landfill operations.     

现代垃圾填埋场设计思路的探讨

本文对我国垃圾填埋场存在的问题进行分析 ,并针对这些问题提出了解决的措施 ,为我国现代垃圾填埋场的优化设计提供新的思路     

Computer simulation of gas generation and transport in landfills II: Dynamic conditions

Extensive simulations have been carried out to study generation of landfill gases by biodegradation of wastes and their transport in a model landfill, using a comprehensive three-dimensional model developed in Part I of this series. The model has been developed for a four-component gas mixture, and takes into account the effect of heterogeneity in the landfill's morphology, as well as that of the surrounding soil. It accounts for the presence of gas extraction wells with an arbitrary spatial distribution. The model is utilized for investigating the dynamic behavior of a landfill, and in particular pressure build-up, under a variety of conditions. These include, for example, the cases in which some of the extraction wells are shut down, or new wells are drilled. It is shown that the spatial distribution of the permeability has a very strong effect on the dynamic behavior of a landfill, whereas mechanical dispersion, manifested by effective dispersion coefficients that depend on the flow velocities, has virtually no effect. Thus, development of an accurate data base for the spatial distributions of the permeability, porosity, and other morphological characteristics of a landfill, in addition to its transport and reaction properties, is essential for accurate forecasting of the landfill's behavior, including identifying the areas with large amounts of methane and a potential for explosion. Limited comparison of the model's predictions with experimental data for a particular landfill indicates the potential of the model for predicting the dynamic behavior of large landfills.     

武汉市垃圾卫生填埋场沉降计算及意义

生活垃圾卫生填埋场的沉降是目前卫生填埋法所涉及的主要的岩土工程问题之一。深人开展生活垃城,卫生填埋场沉降特性的研究意义重大。选取武汉市的一处卫生填埋场,研究了填埋过程中和填埋场封顶后垃圾土的长期沉降变形,结果表明填埋沉降百分率高达100％左右。     

Strategy for Complete Nitrogen Removal in Bioreactor Landfills

Waste acclimation and batch microcosm studies containing digested municipal solid waste were conducted at different temperatures (22, 35, and 45°C) and gas-phase oxygen concentrations (0.7–100%, by volume) to provide guidance for field-scale implementation of in situ nitrogen removal processes. Results demonstrate that in situ ammonia–nitrogen is feasible in decomposed aerated solid waste environments at the gas-phase oxygen concentrations and temperatures evaluated and the potential for simultaneous nitrification and denitrification in field-scale bioreactor landfills is significant due to the presence of both aerobic and anoxic areas. Small amounts of oxygen were found sufficient for nitrification/ammonia removal to proceed, although removal rates increase with oxygen concentration. Laboratory results suggest field-scale implementation of in situ nitrogen removal occur in small dedicated treatment zones containing previously degraded waste (later in the life of a bioreactor landfill). Model simulations indicate removal of ammonia–nitrogen to low levels can occur with relatively short aeration depths (depth estimates ranged from 1.6 to 7.2?m below the point of leachate injection). Field-scale verification of these depth estimates is required prior to routine acceptance.