Journal of Environmental Engineering

A dynamic water quality model for storm induced flows in rivers is presented. The hydrodynamic portion is solved by a four‐point implicit Newton‐Raphson procedure, while the water quality code is formulated with a Holley‐Preissmann nonlinear formulation. The water quality model represents the effects of biodegration by plankton, sedimentation, and diffusion of material into the benthos by a single turbulence dependent decay term. Eight constituents are employed and the effects of light shading are considered. Two simple tests were used to provide simple initial calibrations. The first test, the propagation of a Gaussian wave, demonstrated the necessity of higher order treatment of the water quality numerical analog. The second test was a steady state test of the water quality model against data from the Olentangy River. The minimum kinetic structure required for Ohio streams should include CBOD, organic nitrogen, ammonia nitrogen, nitrate nitrogen, and orthophosphate.

Field data were collected at 54 small stream head loss structures in northeastern Illinois to evaluate weir and spillway aeration characteristics. The British dam aeration equation, which employs the use of an aeration coefficient (b), is used as a model to calibrate each head loss structure. The head loss structures are categorized according to basic physical configurations; nine generalized classes are presented. The aeration coefficients vary widely within classes due to seemingly small or subtle differences in structural design or overall physical condition. Spillways having the same basic geometric design may exhibit widely divergent aeration coefficients depending upon conditions at the toe or apron. Hydraulic jumps built into toes produce significantly higher b‐values than those similarly constructed but without hydraulic jumps. The nine dam categories are assigned aeration coefficients which represent the median value observed within each grouping. These values are suitable for use in preliminary model development or when time constraints preclude making field surveys. However, whenever possible field surveys should be conducted using the methodology presented as a guide.

Sewage sludges are often described as excellent soil conditioners. In land application, the physical and chemical properties of the sludge are always carefully characterized; however, the soil conditioning effect resulting from sludge application has seldom been documented. This report describes an experiment which quantitatively measures the effect of sewage sludge on the physical properties of receiving soils in term of four factors: (1) Bulk density; (2) hydraulic conductivity; (3) water holding capacity; and (4) modulus of rupture. Results indicated the agronomic nature of the soil may be improved by such sludge application. However, the amount of sludge required to induce significant changes in soil properties is far greater than the amount normally used to satisfy nutrient requirements for crop growth. Conditioning soils by using sewage sludges results in a reduction of soil bulk density and cohesion, and an increase in water holding capacity and hydraulic conductivity.

A canopy model has been developed to calculate throughfall characteristics based on canopy properties, ambient air quality, and precipitation quantity and quality. The processes considered include wet and dry deposition, leaf exudation, nitrification, and oxidation of ${\mathrm{SO}}_2$ and ${\mathrm{NO}}_x\text{.}$ The model has been calibrated with data collected at Woods Lake in the Adirondack Mountains of New York. The model has accurately simulated throughfall volume and the concentration of 15 throughfall chemical constituents. Ammonium $\left({\mathrm{NH}}_4^{+}\right)$ accumulated on the canopy is nitrified rapidly, resulting in an increase in acidity and nitrate fluxes. The dominant process occurring in the coniferous canopy is dry deposition. The enrichment of acidity in coniferous throughfall is derived primarily from the accumulation of acidic air particulates. The dominant process occurring in the deciduous canopy is exudation. This partially neutralizes the acidic deposition.

A rational procedure for the optimization of branched water supply networks is developed in closed form. Two case studies are presented to illustrate the procedure for the optimal design of complete gravity systems and direct pumping systems.

A multiobjective goal programming method is proposed for use in analyzing problems involving a network flow structure which are commonly found in the wastewater and sludge management systems when cost functions are linear. The goals considered are the minimization of: (1) Costs, (2) water quality impact, and (3) land use impact. The model also selects interceptor routes, treatment plants, transport routes and sludge disposal sites, along with flow directions through these facilities under optimal solutions. A hypothetical example problem dealing with regional wastewater management is analyzed to demonstrate the potential usefulness of the method.

The homogeneous surface diffusion model (HSDM) was found capable of simulating effluent concentration history profiles for a commercial humic acid, a peat fulvic acid (PFA), and a coagulated PFA. The model successfully simulated column data for four granular activated carbons (GAC), several empty bed contact times (EBCTs), two GAC mesh sizes, several influent concentrations, and several hydraulic loadings. Accordingly, the HSDM was used to evaluate the impact of process design variables on cost and adsorber performance for the removal of these humic substances. Model calculations were carried out to evaluate the impact of EBCT and influent concentration on adsorber performance. It was found that for each doubling of EBCT in the range of 3.77 minutes–75.4 minutes the bed life of the carbon was more than doubled. For 50% reductions in influent concentration, the bed life was about doubled for influent TOC concentrations ranging from 1 mg/L–20 mg/L. By estimating the cost of treatment for various EBCTs, the most economical EBCT was determined for a single adsorber, for two adsorbers in‐series, for two adsorbers inparallel, and for three adsorbers in‐parallel. Two adsorbers operated in‐parallel were found to be more economical than a single adsorber, or two adsorbers operated in‐series. The lowest cost operation was for three adsorbers operated in‐parallel. Treatment costs for two adsorbers in‐parallel were found to decrease with increasing treatment plant size, decreasing influent concentration, and dereasing GAC particle size.

A rational method for the design of an onsite sewage disposal system based upon evapotranspiration, and adaptable to different geographical areas, is developed. Available design information and its limitations is noted and the need to exercise informed professional judgement is emphasized. Two examples and water balance tables show application of the design method.

A mathematical model was developed that provides a temperature correction factor for biological reaction rate coefficients over a temperature range of 4 °C–30 °C. The model can be applied for any reference temperature, $T_R\text{,}$ for which a reaction rate coefficient, $K_R\text{,}$ is known. The relative accuracy of the proposed model in estimating the true effect of temperature on the biological reaction is contingent upon values of the upper and lower threshold temperatures, $T_u$ and $T_l\text{,}$ and the value of the temperature coefficient, $G_l\text{,}$ near the lower threshold temperature. The performance of the model was evaluated against known reaction rate values.

A transient thermal simulation model of a hybrid cooling lake is developed to assess the impact of cooling water withdrawals and cooling tower discharges on the thermal structure of the lake. The model is based on one‐dimensional mechanical and thermal energy balances and includes the physical processes of solar heating, wind stirring, vertical advection, and hypolimnetic diffusion. Temperature data were collected on two small lakes in northern Indiana, and the simulated temperatures are compared with the measured data for the lake stratification seasons of 1976 and 1978. It is shown that cooling water circulations significantly thicken the epilimnion due to vertical advection of heat. The simulation results are examined in terms of the values of the wind Richardson number, the withdrawal densimetric Froude number, and the dimensionless surface buoyancy flux. The sensitivity of the lake thermal structure to the densimetric Froude number is demonstrated.

A method has been proposed for the computation of the transverse mixing coefficient in wide and shallow rivers. The study addresses the flow regime where vertical mixing has been completed. The method makes use of the second moments of the tracer concentration distribution and is very easy to apply. It can account for tracer loss by a first order process and for variability of stream cross sections. Field data from a portion of the upper Mississippi River were used for the computations. The values of the transverse mixing coefficient obtained agree well with results reported in the literature.

The Las Vegas area is one of the most arid parts of the driest state in the nation. It is among the fastest growing areas in the nation, and water supplies must be sought and managed to meet the demands of this growth. This paper describes a long range plan of action to ensure adequate water supplies for the next fifty years. Water supplies currently available include groundwater, Colorado River water, and wastewater reuse. The paper describes water supply and water demand alternatives available to conjunctively use groundwater, Colorado River water, wastewater, and water conservation to meet demand considering uncertainties on available supplies and competing demand. Water demand functions were developed by different user classes including residential, commercial, industrial, civic, agricultural and non‐agricultural irrigation, and system losses. These functions can assist other planners in determining water use in arid climates.

A numerical model has been developed to simulate flow in rectangular clarifiers operating at neutral density conditions. The equations of motion in the $\psi -\omega$ format are solved using a finite‐difference method. A two‐step ADI three time level, weighted upwind‐centered difference scheme is used to solve the ω‐equation. The centered‐difference analog of the ψ‐equation is solved using the SOR method. A truncation convergence criterion was derived where the local Courant Number has to be kept below one. Computational stability depends on both Courant number and grid Reynolds number. A variable size mesh reduces both execution time and storage requirements without loss of solution accuracy. A partial slip boundary condition improves on the turbulence model. The finite difference and experimental flow fields are in good agreement.

A relationship between the transfer coefficient of sparingly soluble gases and wind velocity is developed in terms of the liquid film and surface renewal concepts. When a wind blows over water, shear is exerted at the interface, which establishes the structure of the boundary layers in both media. The dynamic characteristics of these interfacial regions influence the rate of transfer between air and water. The functions relating the viscous sublayer and roughness height with the wind shear provide the basis for the development of equations which define the transfer coefficient for both smooth and rough surface conditions. The relationships are applied to the exchange of volatile organic chemicals which are characterized by liquid film control.

The equation governing the concentration field for a dilute suspension of particles is presented for flow in circular and rectangular primary settling basins. The formulation is valid for two‐dimensional, mean steady, isothermal, turbulent flow conditions. Basin flow velocities are obtained from a hydrodynamic model which determines the turbulent diffusion coefficients for mass transport as part of the overall solution. A numerical solution to the mathematical model is formulated by application of the Galerkin finite element method to the equation residuals. The resulting linear, algebraic equation set is solved by a standard elimination scheme. Results include contour plots of particle concentration fields for rectangular and circular basins and removal efficiencies for these tanks. The effect of partial resuspension at the bed (deposition retarded) is included in the analysis.