Considerations for Monitoring Permeable Ground-Water Treatment Walls

Permeable ground-water treatment walls (PTWs) have been implemented as a means by which innovative ground-water treatment technologies can be applied in-situ. Though not widely addressed in the technical literature, the ground-water monitoring program for a PTW at a commercial site should consider several factors including: (1) design elements of the PTW; (2) the remediation process to be implemented through the PTW; (3) the distribution of contaminants in the affected aquifer; (4) ground-water sampling methods; and (5) regulatory issues. Also, the compliance monitoring well network within the PTW and sampling plan should be designed to assure that (1) design ground-water residence time goals within the PTW are achieved prior to sampling; (2) the uniformity of ground-water flow through the PTW is accounted for; and (3) ground-water samples are collected using techniques (e.g., micropurging) that reduce the potential for collecting nontreated ground water from down- or upgradient of the PTW. A case study illustrates the concepts used to develop a ground-water monitoring program for a PTW that was accepted by regulatory agencies for a commercial site.     

Controlled Field Experiment for Performance Evaluation of Septic Tank Effluent Treatment during Soil Infiltration

Decentralized systems are responsible for treating approximately 25% of the wastewater generated in the United States. The most common decentralized system involves onsite treatment using a septic tank unit followed by dispersal to a subsurface soil infiltration unit where percolation to groundwater occurs. To evaluate the hydraulic and purification processes occurring during soil treatment of septic tank effluent (STE), a field experiment was initiated in the Spring of 2003 with continued operation and monitoring for 2 years. A replicated factorial design (22) was employed to evaluate three infiltrative surface architectures (ISAs) (open, stone, and synthetic) and two daily hydraulic loading rates (HLRs) (4 and 8?cm/day). Pilot-scale test cells were established in native sandy loam soils at the Mines Park Test Site located on the Colorado School of Mines campus in Golden, Colo. STE was obtained from a nearby multifamily apartment building and applied to the test cells daily. Field monitoring included baseline characterization of soil and site properties, routine characterization of the STE applied, observations of STE ponding on the infiltrative surface, periodic measurement of constant-head infiltration rates, and periodic sampling and analyses of the soil pore water at 60- or 120-cm depths below the infiltrative surface. Monitoring revealed that the ISA and HLR influenced the rate and extent of hydraulic capacity loss during soil treatment. For example, an open horizontal infiltrative surface maintained an infiltration capacity that was 40–80% higher than one covered with either washed stones or synthetic aggregate. Purification of STE during infiltration and percolation through the sandy loam soil was very high. The cumulative mass removed during 2 years of operation for dissolved organic carbon, total nitrogen, and total phosphorus averaged 94, 42, and 99%, respectively. While there was no significant difference in the purification performance based on ISA or HLR, an increase in the vadose zone depth slightly increased purification.     

Storm-Water Infiltration and Focused Recharge Modeling with Finite-Volume Two-Dimensional Richards Equation: Application to an Experimental Rain Garden

Rain gardens are infiltration systems that provide volume and water quality control, recharge enhancement, as well as landscape, ecological, and economic benefits. A model for application to rain gardens based on Richards equation coupled to a surface water balance was developed, using a two-dimensional finite-volume code. It allows for alternating upper boundary conditions, including ponding and overflow, and can simulate heterogeneous soil-layering or more complex geometries to estimate infiltration and recharge. The algorithm is conservative, and exhibits good performance compared to standard models for several test cases (less than 0.1% absolute mass balance error); simulations were also performed for an experimental rain garden and comparisons to collected data are presented. The model accurately simulated the matrix flow, soil water distribution, as well as deep percolation (potential recharge) for a natural rainfall event in the controlled experimental setup.     

Fate of Polybrominated Diphenyl Ethers, Nonylphenol, and Estrogenic Activity during Managed Infiltration of Wastewater Effluent

About a billion cubic meters of wastewater effluent are artificially recharged annually in the United States for maintenance of groundwater levels and prevention of seawater intrusion. There is concern that trace contaminants, including various endocrine disrupting compounds (EDCs), are not completely removed during infiltration, leading to deterioration of groundwater quality. In this work, we investigate the mechanisms and efficiency of EDC removal at the Sweetwater Recharge Facility, which is used to recharge secondary effluent from the Roger Road Wastewater Treatment Plant in Tucson, Ariz. Material was collected from the top meter of sediments in two infiltration basins and analyzed for extractable nonylphenol (NP), polybrominated diphenyl ethers (PBDE) and total estrogenic activity. The basins differed significantly in length of service (7 versus 15 years). Nevertheless, profiles of extractable contaminants and estrogenic activity were similar in the two basins. Results suggest that hydrophobic determinants of estrogenic activity are efficiently retained in surface sediments during soil-aquifer treatment. However, measurable levels of PBDEs, NP, and estrogenic activity are present in infiltrate that reaches the local unconfined aquifer at ～ 40?m below land surface.     

Use of Layered Geotextiles to Provide a Substrate for Biomass Development in Treatment of Septic Tank Effluent Prior to Ground Infiltration

The use of layered geotextile filters for biological treatment of septic tank effluent prior to ground infiltration was investigated. The goal was to provide secondary treatment and prevent soil clogging by fostering biomass growth in the internal porosity of commercially available geotextiles. The study used primary effluent from a water pollution control facility that serves a combined sewer area. To identify sustainable operating conditions, the hydraulic loading rate (HLR) and other parameters were varied in tests with columns packed with multiple geotextile and granular layers. At continuous high hydraulic loading rate application, over 90% of total suspended solids and biochemical oxygen demand was removed, but the three layer filters eventually clogged. When a 365?L/m2?day?(9.0?gal/ft2?day) HLR was applied in dose and drain cycles to two filter layers, not only was there little loss in permeability, but ammonia (NH3) and nitrate (NO3?) concentrations in the effluent were reduced to below 5 and 10?mg/L, respectively. Scanning electron microscope images showed that the biomass morphology was not a continuous biofilm as was expected, but a discontinuous floc trapped within the geotextile pore structure. This provided intimate contact between substrate, oxygen, and biomass to produce the desired effluent quality and limited loss in filter permeability.     

Analytical Ground-Water Flow Solutions for Channel-Aquifer Interaction

A general solution scheme for determining ground-water levels for channel∕group-water systems with recharge is developed and verified. The analytical solution uses the Laplace transform method to solve a linearized form of the Boussinesq equation. Unlike other solutions, this scheme allows for both boundaries and sources∕sinks to vary as a function of time and space. To verify the analytical scheme, three one-dimensional case studies of flow between two line sources in an unconfined aquifer were explored through a base run and a set of sensitivity analyses. These runs involved comparisons to MODFLOW and changes in the boundary conditions and dimensions. As noted, the flow equations were linearized about a point called the representative flow depth. A value of havg, defined as the average water depth between the initial and steady flow conditions, was used as the representative flow depth. Results of the proposed method matched very well with MODFLOW solutions for all times and locations using an optimal linearization point. In addition, using havg improved the solutions compared to those obtained previously.     

Evaluation of Hopscotch Method for Transient Ground-Water Flow

The hopscotch finite-difference technique is shown to be a fast and accurate way to simulate transient, saturated, ground-water flow in relatively typical but heterogeneous 2D and 3D domains. The odd-even hopscotch (OEH) and line hopscotch methods are reviewed, and their implementation for saturated ground-water flow is presented. The OEH scheme, which is a second-order accurate explicit process, is efficient, requiring only six floating point operations per mesh node and time step, and is unconditionally stable (for saturated ground-water flow). Numerical experiments on typical 2D meshes (2,500 nodes) with synthetic, randomly heterogeneous hydraulic conductivity, suggest that the OEH process is approximately 1.5 times faster than the alternating direction implicit method and 3–4 times faster than the Crank-Nicolson implicit method using preconditioned conjugate gradient iteration. Similar experiments on medium-sized 3D meshes (87,500 nodes) suggest that the OEH process is between 7 and 10 times faster than the Crank-Nicolson preconditioned conjugate gradient method. Although the numerical results presented illustrate only typical test problem performance, they nevertheless clearly indicate promise for using OEH to simulate transient ground-water flow in 2D and, especially, 3D heterogeneous domains requiring fine spatial meshes.     

某达标企业废气污染扰民引发的思考

通过实例,对企业废气虽然达标排放,但却造成污染扰民问题进行探讨,并通过进一步分析,提出解决完善固定大气污染源控制法规和标准的对策及建议。     

利用生产氧化铝的废水制取软化水的工业实践

介绍中铝山西分公司利用生产氧化铝废水制取软化水的试验和生产实践。工业试验结果表明,滤池出水的有关指标始终保持悬浮物≤10mg/l、总硬度≤125mg/l、总溶解性固体≤950mg/l。     

Explicit Infiltration Function for Furrows

This study addresses infiltration from furrows or narrow channels. The basic approach is to develop the two-dimensional infiltration as a combination of the corresponding one-dimensional vertical and an edge effect. The idea is borrowed from previous applications for infiltration from disc and strip sources. The assumption is tested directly with numerical experiments using four representative soils and three furrow shapes (triangular, rectangular, and parabolic). The edge effect is the difference between the cumulative infiltration per unit of adjusted wetting perimeter and the corresponding one-dimensional infiltration. A general conclusion is that the edge effect is linearly related to time. In addition, it was observed that the two empirical parameters in the function used to relate the edge effect with time have narrow ranges and are related to soil hydraulic parameters, furrow shape, the boundary and initial conditions and additional geometric factors. The approach leads to a physically based infiltration function for irrigation furrows (or narrow channels) without the need to perform a fully two-dimensional simulation. Also, a simplified expression was found for the limiting steady-state case, which is analogous to Wooding’s equation for infiltration from a shallow pond.     

Simulation of Ground-Water Flow in Steep Basin with Shallow Surface Soil

A coupled ground-water∕channel flow distributed model has been developed for continuous simulation in a 123-km2 basin. The aim was to analyze the streamflow generation processes in natural vegetated environments. Finite-difference schemes have been used to solve conservation equations of the 2D saturated subsurface flow and the 1D kinematic surface flow. Because of the high hydraulic conductivity of the surface soil, only the saturation excess mechanism of runoff production has been considered. Parameter sensitivity analysis showed the overriding influence of soil storage capacity and conductivity. A grid discretization >100 m produces a hydraulic conductivity greater than physically meaningful, which considerably increases as the space-grid step increases. Results indicate that the model can satisfactorily simulate the water-flow behavior of the catchment after fitting the three parameters of surface hydraulic conductivity, effective porosity, and evapotranspiration losses. These are done after calculating the conductivity as a function of the height of the water table. The simulation efficiency has varied from 87% in the first 5-year calibration period to 85.8% in the subsequent 5-year validation period.     

充分利用澜沧铅矿尾矿与废渣的思考

阐述了云南澜沧铅矿尾矿和废渣存在的一些问题，提出了切实可行的处理办法。     

Multidimensional Infiltration with Arbitrary Surface Fluxes

A new solution to the multidimensional linearized Richards equation was derived using a Fourier integral transform. Exponential functional forms k = kseαψ and θ = θr + (θs ? θr)eαψ were used to represent the hydraulic conductivity and pressure relation and the soil water release curve. The analytical solutions consider the conditions of time dependence and nonuniform distribution of rainfall intensity and arbitrary initial water content distribution with a water table. The analytical solutions can be used to predict the ponding time and to obtain the volumetric water content distribution over time and space.     

废塑料配煤炼焦试验

在炼焦煤中配入一定量的废塑料,利用20kg试验焦炉做炼焦试验,对所得焦炭产率、冷态和热态强度进行了分析。试验表明：除添加0．5％聚乙烯（PE）炼焦未使焦炭产率增加外,添加废塑料后,焦炭的产率均比未加废塑料的高;添加废塑料后焦炭的抗碎强度（M40）整体出现下降趋势．耐磨强度（M10）整体也是降低的;添加废塑料后焦炭的反应性（CRI）整体出现升高趋势,相应的反应后强度（CSR）成整体降低趋势。     

Quick Method for Estimating Furrow Infiltration

This paper presents a simple and quick method for estimating furrow infiltration using a single advance point based on the volume balance equation. The furrow infiltration and water front advance along the furrow are assumed to follow the modified Kostiakov infiltration and power advance equations, respectively. The volume balance equation, including these equations, is simplified to a function containing two parameters, i.e., the exponents of power advance and Kostiakov infiltration equation (with a prior-known basic infiltration rate). These parameters are estimated by minimizing the function to zero using a quasi-Newton search algorithm, provided with Excel Solver. The estimated exponents are used to determine the Kostiakov infiltration parameters. The proposed one-point method is tested with seven independent furrow irrigation evaluation data sets and the estimated cumulative infiltration is compared with the observed counterparts. Performance of the proposed method was evaluated using the root-mean-square error and index of agreement (Ia). The results show that the proposed one-point method estimated cumulative infiltration is closer to the observed; the method performed as good as Valiantzas’ method. Shepard’s method did not perform well for the tested data sets. The algorithm and the results of the proposed method reveal that the proposed method can be used as a tool for quick estimation of furrow infiltration using a single advance point.     

New Process Design Procedure for Dealing with Variable Trickling Filter Effluent Suspended Solids

Based on a survey which showed that seven of eight conventional trickling filter (CTF) plants exceeded the U.S. Environmental Protection Agency secondary treatment regulatory requirements, a new design procedure is proposed. It recognizes that bioflocculation within CTFs is poor and that most of the effluent violations seen in the survey could be related directly or indirectly to the level of effluent suspended solids. In past practice, process design focus has been on soluble or settled effluent biochemical oxygen demand (BOD5) rather than the effluent suspended solids. The principal focus in CTF process design should be on predicting effluent suspended solids (SS) after secondary clarification, rather than effluent carbonaceous BOD5. If the total organic loading (TOL) is set in the proper range, the effluent carbonaceous BOD5 is primarily determined by the effluent SS. A new design procedure has been developed that identifies the highest TOL that can be sustained without posing a constraint on effluent SS due to effluent CBOD5 limitations. This is coupled with the incorporation of additional design features that can control effluent SS.     

Unsteady Solution for Well Recharge in a Low Diffusive Aquifer

Finite aquifer solution exists for the constant head in a fully penetrating well. Their use for well recharge is limited, as they do not permit simultaneous computation of unsteady wellhead pressure and variable recharge rate. In the present paper semianalytical solutions are presented for well recharge under variable head boundary condition. These solutions were developed using the method of separation of variables and Duhamel’s convolution theorem. The solution developed in the paper was verified with the Jacob-Lohman solution and subsequently validated using field data pertinent to constant-head boundary conditions. Subsequently for variable head boundary condition such an appropriate background was found missing in the literature.     

Considerations for conducting group intervention with adults who stutter

With recent changing trends in healthcare delivery and reimbursement, the focus on more efficient and cost-effective intervention has become increasingly important. A summary of desired clinician skills and responsibilities reported in the literature are presented along with information on structuring group intervention. Preliminary findings and a rationale for conducting speech therapy in a group environment with several adults who suffer are presented. In addition, findings and perceptions gleaned from the authors' experience in conducting group treatment with persons who stutter are also discussed.     

Infiltration of Water into Soil with Cracks

This paper presents the physical basis of the FRACTURE submodel for simulating infiltration of precipitation∕irrigation water into relatively dry, cracked, fine-textured soils. The FRACTURE submodel forms part of the HYDRUS-ET variably saturated flow∕transport model. Infiltration into the soil matrix is formally divided into two components: (1) Vertical infiltration through the soil surface; and (2) lateral infiltration via soil cracks. The first component is described and solved using the 1D Richards' equation. Excess water that does not infiltrate through the soil surface is either considered to be runoff, if no soil cracks are present, or routed into soil cracks from where it may laterally infiltrate into the soil matrix. Horizontal infiltration from soil cracks into the soil matrix is calculated using the Green-Ampt approach and incorporated as a positive source∕sink term Sf in the Richards' equation describing flow in the matrix. In addition to the hydraulic properties of the soil matrix, the FRACTURE submodel requires parameters characterizing the soil cracks, notably the specific crack length per surface area lc and the relationship between crack porosity Pc and the gravimetric soil water content w. An example problem shows that infiltration from soil cracks can be an important process affecting the soil water regime of cracked soils. A comparison with the more traditional approach, involving surface infiltration only, indicates important differences in the soil water content distribution during a rainfall∕irrigation event. This extension of the classical approach to include crack infiltration significantly improves the identification and prediction of the soil water regime.