Journal of Environmental Engineering

Diffusive mass transfer between fracture and matrix accompanied with sorption significantly influences the efficiency of natural attenuation in hard rocks. While these processes have extensively been studied in a fractured formation, limited information exists on the sorption nonlinearity. For this purpose, a numerical model is developed that couples matrix diffusion and nonlinear sorption at the scale of a single fracture using the dual-porosity concept. The study is limited to a constant continuous solute source boundary condition. The influence of both favorable and unfavorable sorption intensities on solute mobility is investigated using the method of spatial moments. The differing capacities of available sorption sites between fracture surfaces at the fracture-matrix interface and the solid grain surfaces within the rock matrix result in a slower migration of solutes along the fracture, and a larger amount of diffusive mass transfer away from the high permeability fracture.

Two separate on-site wastewater treatment systems were constructed at premises in eastern Ireland, one using a conventional septic tank, the other using a septic tank followed by a naturally aerated peat filter. The respective effluents were then split at each site whereby half was directed into percolation trenches and the other half pumped into intermittently dosed, stratified sand filters for a year. Samples were taken at different depths in the subsoil beneath both the percolation trenches and sand filters and analyzed for chemical and bacteriological determinants. Samples were also taken at different layers within the sand filters, which were tested at various hydraulic loading rates. Although the sand filters require a much smaller surface area, the respective pollutants on each site were attenuated to the same level in the subsoil when compared to the percolation trenches. As a result of the trials, the recommendations for design hydraulic loading rates in Ireland were $30\mathrm{L}∕{\mathrm{m}}^2\text{day}$ for filters receiving septic tank effluent and $60\mathrm{L}∕{\mathrm{m}}^2\text{day}$ for filters receiving secondary treated effluent.

Sanitary sewer systems are fundamental and expensive facilities for controlling water pollution. Optimizing sewer design is a difficult task due to its associated hydraulic and mathematical complexities. Therefore, a genetic algorithm (GA) based approach has been developed. A set of diameters for all pipe segments in a sewer system is regarded as a chromosome for the proposed GA model. Hydraulic and topographical constraints are adopted in order to eliminate inappropriate chromosomes, thereby improving computational efficiency. To improve the solvability of the proposed model, the nonlinear cost optimization model is approximated and transformed into a quadratic programming (QP) model. The system cost, pipe slopes, and pipe buried depths of each generated chromosome are determined using the QP model. A sewer design problem cited in literature has been solved using the GA-QP model. The solution obtained from the GA model is comparable to that produced by the discrete differential dynamic programming approach. Finally, several near-optimum designs produced using the modeling to generate alternative approach are discussed and compared for improving the final design decision.

Most widely used nonpoint source models associate pollutant loads almost exclusively with land use via pollutant export coefficients and some kind of runoff coefficient. Not surprisingly, the range of management options suggested by such models’ simulations are largely linked to changes in land use. This problem is addressed by developing models of dissolved phosphorus (DP) mobility for specific agricultural sources: manure, fertilizers, soil/plant complexes, and impervious surfaces and those associated with baseflow P loads. These models are coupled with a spatially distributed hydrologic model, the variable source loading function model. The model was applied to a small $\left(164\mathrm{ha}\right)$ , upstate New York watershed and tested against 1996–2000 stream flow and DP data. The source-specific model required no direct calibration of parameters compared to eight parameters needed in a similar export coefficient type model. Both models predicted stream DP loads well but the source-specific model provided additional insights into, for example, how much DP in the stream was derived from accumulated soil P as opposed to direct leaching from manure. This type of information is necessary to develop and assess a full range of options for best management practices, especially those that involve nonstatic activities such as manure spreading.

In this project, the ability of natural media filtration (NMF) to remove colloidal particles and associated hydrophobic organic compounds from the aqueous phase was evaluated by performing sorption and transport experiments with leaf compost media. Phenanthrene sorption isotherm experiments for compost and model colloidal (latex) particles found that phenanthrene has a greater affinity for the colloidal particles than for the compost materials. In column experiments, the transport of phenanthrene through the NMF in the presence and absence of two colloidal particles with different hydrophobicities [sulfate (more hydrophobic) and carboxylate (less hydrophobic)] showed that the effluent phenanthrene concentration in the presence of colloids, particularly sulfate latex particles, is much higher than that in the absence of colloids. The results from a mathematical model used to evaluate data from the column experiments suggest that enhancement of contaminant transport can be significant under the following conditions: high colloidal concentrations, high partition coefficient between contaminant and colloids, or a slow desorption rate of contaminant from colloids.

Consumer batteries littered in urban environments are generally littered on pavements. These batteries rapidly deteriorate by several physical and chemical mechanisms that breach their structural integrity and release a host of environmentally significant pollutants (Ag, Ba, Cd, Cr, Cu, Hg, Li, Mn, Ni, Pb, Ti, Zn) to storm-water runoff. Research on urban battery litter began at Case Western Reserve University in the summer of 2001. This paper presents much of what is currently known about the occurrence of urban battery litter. Data are presented on the number, type, and condition of over 6,100 littered batteries collected in field surveys conducted in urban areas around Cleveland. Methods are presented for estimating battery litter rates and for characterizing the size, structure, internal chemistry, deterioration status, life expectancy, and contaminant release potential of urban battery litter. Results from field study sites demonstrate that at “hot spot” locations, battery litter can be a significant source of contamination. Annual litter rates as high as $215\text{batteries}∕\mathrm{ha}$ (nearly 90/acre) of parking lot pavement and $0.4\text{batteries}∕\mathrm{m}$ of street curb (one battery for every $8\mathrm{ft.}$ of curb) have been measured. At some locations the Zn mass loading from batteries approaches $1\mathrm{kg}∕\mathrm{ha}$ and could be the most significant source of pavement-related Zn released to urban storm-water runoff.

Lead pollution is common in Western China and has caused serious public health problems recently. The treatment of wastewater containing Pb(II) is stringent for the sustainable development of local economics. The Chinese loess proved effective to remove Pb(II) from aqueous solution and applicable in the treatment of wastewater from lead–zinc ore mining sites. The adsorption capacity of Chinese loess about Pb(II) is determined as high as $270.26\mathrm{mg}{\mathrm{g}}^{-1}$ in this study. Factors affecting the adsorption of Pb(II) include slurry concentration, solution pH, temperature, and equilibrating duration. The optimum conditions for Pb(II) adsorption include sorbent $\text{dosage}⩾0.05\mathrm{g}∕50\mathrm{mL}$ , $\mathrm{p}{\mathrm{H}}_i⩾\mathrm{p}{\mathrm{H}}_{\mathrm{zpc}}$ , $\text{temperature}=55°\mathrm{C}$ , and equilibration $\text{duration}⩾30\min$ . The isotherms and kinetic data are well fitted with Langmuir model and pseudo-first order kinetics, respectively. The thermodynamic behavior reveals the exothermic and spontaneous nature of the adsorption. The adsorption of Pb(II) on loess involves chemical reaction with calcite and surface complexation with clay minerals and hydrolysis of quartz; the former is considered as the dominant mechanism. X-ray diffraction and Fourier transform infrared patterns confirmed these speculations.