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It is often assumed that soils are homogeneous when designing septic systems or modeling wastewater flow from their trenches. The main objective of this study was to assess water infiltration and movement from the trenches similar to the ones commonly used for on-site wastewater dispersal by septic systems. Four separate experiments, each using a small drainfield with four parallel trenches, were conducted at three sites with different soils. In two experiments the trenches were in the coarse-textured soil above a clayey Bt horizon. In the other two experiments the trenches were in the Bt horizon. For each experiment, 50 L of a solution containing potassium bromide and brilliant blue FCF (as a tracer dye) were applied once a day to each trench for 14 or 15 days. A sampling pit was dug perpendicular to the trenches after the tracer solution application, and the distribution of the tracer dye and Br- around the trenches on the two walls of the pit were assessed. Tracer solution infiltration from the trenches was not uniform in any of the experiments. Water flow in the Bt horizon was mainly through macropores. Further, water containing Br- and dye moved a substantial distance from the trenches through macropores when trenches were installed in the Bt horizon. When trenches were installed in the coarse-textured soil above the Bt horizon, most of the tracer solution moved away laterally from the drainfield through the zone above the Bt horizon. Overall, the results indicate that soil morphological properties and soil horizonations, as well as the nature of water movement from trenches must be considered when modeling water flow from septic system trenches or when designing septic system drainfields. [ABSTRACT FROM AUTHOR]

On-site wastewater systems (OWS) provide a sustainable method for disposing of residential wastewater. Large “cluster” OWS systems are now frequently being used to serve multiple-unit housing developments. Groundwater perching, mounding, and lateral flow can occur when the effluent application rate to an infiltration area exceeds the soil’s capacity to infiltrate the wastewater. This study addresses mounding of wastewater on a low hydraulic conductivity (K) layer in the vadose zone, and focuses on modeling tools available to design systems so that the potential for the occurrence of surface or side-slope breakout is minimized. In particular, we demonstrate how an existing analytical model developed by Khan et al. (1976) can be used for evaluating the mounding problem. The robustness and limitations of the analytical solution due to certain constraining assumptions are evaluated for a few realistic scenarios by comparing it to results of a numerical model that is not constrained by the assumptions. The height and extent of mounding depends on both the hydraulic conductivity of the soil below the infiltration field, as well as the K value of the low-permeability layer. The numerical modeling demonstrates that the analytical solution is more accurate for the case of a thick low-K layer, and for conditions that represent a deep water table, because these conditions are more closely aligned with the conceptual model that the analytical solution derivation is based on. The analytical solution is less accurate for cases of a shallow water table, or a thin low-K layer. Mounding is smaller for thin low-K layers and for deep water tables. In general, it is shown that the analytical model is a conservative predictor for mounding for several reasons. First, it does not consider the capacity of the vadose zone to conduct infiltrating water laterally. Second, nonuniformities in a low-permeability layer (e.g., breaks in the layer) tend to reduce the mounding compared to the uniform layer assumed by the analytical solution. Third, anisotropic soils, where the vertical K is less than the horizontal K (a typical case), exhibit a smaller mounding height and lateral extent of mounding than predicted by the analytical solution. Measurement or accurate estimation of hydraulic conductivity values for subsurface soil layers is necessary for both analytical and numerical models if an accurate assessment of mounding is desired. [ABSTRACT FROM AUTHOR]

Lead removal from water and contaminated soils was investigated using biosurfactant, anionic, and nonionic surfactants in continuously stirred batch reactors. Lead-contaminated water up to 100 mg/L and clay soil up to 3,000 mg/kg were used in this investigation. The surfactant concentration up to 10 critical micelle concentration was used. The speciation of lead into the micelles was quantified and the lead removal efficiency depended on the level of contamination, surfactant type, and concentration. Of the surfactants used, biosurfactant (produced from used vegetable oil) had the best removal efficiency (75%) at a lead contamination of 100 mg/L in water at pH of over 12. The Fourier-transformed infrared spectroscopy study showed that the carboxyl group in the biosurfactant was effective in removing the lead from the solution. Langmuir and Freundlich relationships were used to represent the micelle partitioning of lead in the surfactant solutions. Desorption of lead from contaminated kaolinite clay was represented using linear isotherms. The biosurfactant solution had a higher micelle partitioning for the lead from contaminated water and desorbing the lead from the contaminated soil compared to the other chemical surfactants. [ABSTRACT FROM AUTHOR]

Analyzes the artesian landfill liner system. Features of the system; Geometric programming of the system; Cost optimization of the system.

The purpose of this technical note is to present two analytic solutions for modeling one-dimensional gas flow in municipal solid waste landfills with horizontal gas collection systems. In previous work, vertical flow was considered. In the present communication, situations in which cylindrical or spherical symmetry apply are considered. These models, although not perfect descriptions of typical landfill geometries, should be useful during the 'roughing-out' stage of gas collection systems and may be used to estimate maximum pressures with a minimal effort. Because all the requisite background is developed in the cited reference; the reader is directed to consult it for that purpose. [ABSTRACT FROM AUTHOR]

This article introduces the journal with a discussion of the hydrology of septic tank systems and other on-site sewage disposal processes.