Journal of Environmental Engineering

This paper presents a cost‐benefit analysis for alternative programs intended for the control of the nuisance growth of an attached alga (Cladophora). Such analyses require that changes in water quality be quantitatively related to the cost of implementation for specific management strategies. In this study, a mathematical model for Cladophora growth provided the link between management strategy and water quality. Credibility of the model as a management tool was established through a program of model development, calibration and verification at a site on Lake Huron. The modeling program was complemented by an extensive field monitoring effort and comprehensive scientific studies defining the processes of nutrient uptake and algal growth. Cost‐benefit analyses were prepared for three general control strategies: (1) Reduction of phosphorus loading by treatment using chemical precipitation; (2) reduction of nearshore phosphorus concentrations using an offshore discharge; and (3) combinations of phosphorus removal and offshore discharge. The results of the analysis, although specific for the study site at Harbor Beach, Michigan, suggest that treatment of the effluent to 0.5 to 1.0 mg P/L (total phosphorus) combined with offshore discharge, provides an effective and cost‐optimal control procedure.

A continuous simulation reservoir model was used to develop streamflow‐related effluent standards for nitrate‐N discharges into a water supply impoundment. The nitrogen removal standard for advanced wastewater treatment (AWT) plant represents relaxation of year‐round 1.0 mg/L total N effluent standard intended for lake eutrophication management. During years with average or above‐average streamflow conditions, AWT discharges must reach 40 mgd $(151.6\times {10}^{6}L/\mathrm{day})$ before even limited AWT nitrogen removal operations may be necessary to meet the reservoir's 5 mg/L nitrate‐N standard. During years with relatively low streamflows, the 5 mg/L nitrate‐N standard can be met with limited or no AWT nitrogen removal operations by a 10 mgd $(37.9\times {10}^{6}L/\mathrm{day})$ discharge while extensive nitrogen removal operations during most or all of the low flow period are typically required for discharges in excess of 20 mgd $(75.8\times {10}^{6}L/\mathrm{day})\text{.}$ Streamflow‐related effluent standard and AWT operating rule curves permit annual operation and maintenance cost‐savings of approximately one to two million dollars, depending upon AWT discharge and streamflows, and deferral of nitrogen removal unit expansion for 10–15 years.

NPS continuous simulation model was calibrated to 11 single‐land use watersheds in Chesapeake Bay drainage area to derive nonpoint pollution loading factors (total N and total P) for rural, agricultural, and urban land use categories. Flow, rainfall, and nonpoint pollution monitoring records for each test watershed cover approximately 1–1.5 years. Parameter adjustments for calibration of both the hydrologic and nonpoint pollution submodels relied upon NPS model executions with continuous 15‐minute rainfall record covering the entire monitoring period. Parametric and nonparametric statistics were used to assess goodness‐of‐fit for nonpoint pollution loading calibration. In light of the higher power than normal statistics for datasets characterized by small sample sizes and skewed distributions, nonparametric statistics are recommended for goodness‐of‐fit assessments for nonpoint pollution loading models. Calibrated NPS loading factors for total N and total P are presented for the following land uses: (1) Forestland; (2) pastureland; (3) high and low tillage cropland; (4) single family residential; and (5) commercial. Simulated annual unit area loads for each land use are compared for years of normal and above‐average rainfall.

Large volumes of brine are being discharged into the Gulf of Mexico where cavities are being mined in salt domes for the storage of crude oil along the Gulf Coast. A model study of a dense, vertical jet in a stagnant homogeneous fluid was conducted to develop diffuser design criteria. The model study indicated that in addition to the densimetric Froude number the riser height is a significant diffuser design parameter. The ratio of volume brine discharged to receiving water volume had considerable influence on the jet dilution. In model runs where the jet reached the surface, the resulting dilution was greater than that of a comparable jet that did not reach the surface. Results of field studies at the Freeport, Texas brine disposal outfall compared favorably with the results of the model study.

A two‐dimensional hydrodynamic‐temperature model was applied to Cherokee Reservoir to examine similarities between circulation patterns and observed water quality phenomena. A circulation pattern, involving reverse bottom flows which occurred during March through July, was believed to be the pattern most likely to influence: (1) High fecal coliform concentrations in a water supply intake, located in the reservoir upstream of a wastewater outfall; (2) depressed dissolved oxygen concentrations in the metalimnion; and (3) the development of dissolved oxygen depletion in the hypolimnion.

AS a consequence of new coal mining practices, coal preparation plants have been inundated with increased loads of coal and clay particles in their wastewater. Traditionally, the industry has employed primary sedimentation for the treatment of these sediment‐laden waters. This study examined the possible use of commercial coagulants for the treatment of these wastewaters, with specific emphasis being placed on the impact of mixing conditions on observed solids removal. Aluminum sulfate and cationic polymers were utilized in research studies under varying conditions of mixing intensity and time. The results showed that efficient coagulation was accomplished under a variety of mixing conditions, with poor solids removal noted only when the coagulated suspensions were exposed to excessive shear. Particle size distribution analyses were utilized extensively in the interpretation of experimental results and the formulation of project conclusions.

A finite‐element density‐homogeneous lake circulation model is coupled to a finite‐segment water quality model for phytoplankton modeling in the embayments of lakes. This coupled model is applied to the Rochester Embayment, Lake Ontario during the nonstratification period and to Saginaw Bay, Lake Huron throughout the whole year. A relationship is developed to favorably calculate large‐scale dispersion and turbulent exchange coefficients from detailed velocities calculated from the finer‐scale lake circulation model around the coarser water quality segments. The utility and advantage of using a detailed lake circulation model in eutrophication analysis is indicated and a series of steady‐state calculations with a circulation model is shown to be applicable for simulation of time‐variable, seasonal phytoplankton variation in embayments. Water current outputs and constituent concentration are found to be sensitive to the change of vertical eddy viscosity, drag coefficient on the water surface, and wind data for the circulation model.

The performance of three lagoon‐intermittent sand filter systems treating municipal wastewaters were monitored for three 30‐consecutive days, 24‐hour composite sampling periods during different seasons of the year. Operation and maintenance requirements were also monitored for one year at each site. All but one of the systems satisfied the 1972 federal secondary treatment discharge standards for ${\mathrm{BOD}}_5\text{,}$ and that facility removed 84% of the ${\mathrm{BOD}}_5$ instead of the required 85% removal. The 30‐day mean effluent ${\mathrm{BOD}}_5$ concentrations for all three systems ranged from 3‐21 mg/L with a percentage removal range of 84%‐98%. The 30‐day mean effluent SS concentrations ranged from 8‐21 mg/L. Eighty five percent removal of SS was not achieved during two of the nine sampling periods, once at Mt. Shasta, California, and once at Ailey, Georgia. At no time did the 30‐day geometric mean effluent fecal coliform concentration of the three systems exceed 200 organisms/100 ml. Geometric mean fecal coliform concentrations of less than 200 organisms/100 ml were produced without disinfection. Only three of 260 effluent samples had a pH value that did not lie within the required range of 6.0 to 9.0. Total treatment costs for the three niters evaluated ranged from $\$0.04-\$0.06\mathrm{per}{m}^3$ of nitrate.

Ability of a continuous simulation model to predict nonpoint pollution loads and reservoir water quality was reevaluated for conditions significantly different from those used for calibration/verification. Lower pollution loadings than calibration/verification period resulted from start‐up of regional advanced wastewater treatment (AWT) plant and significant switchover from high tillage cropland practices within the reservoir's 580 sq mile $\left(1\text{,}500{\mathrm{km}}^2\right)$ drainage area. Use of both parametric and nonparametric statistical tests to assess model goodness‐of‐fit is demonstrated. Nonpoint pollution loading factors from small testing sites are reverified with gaging data at the mouths of two watersheds representing more than 90% of reservoir drainage area. Simulated water quality statistics for two‐layer reservoir are compared with daily average of recorded data from 7 monitoring stations. There was typically no significant difference between simulated and recorded statistics on nonpoint pollution loadings and concentrations of critical indicators of lake eutrophication. Results are further evidence of the model's reliability for water quality studies of land use plans or control measures that also produce major changes in pollution loadings.

The results of full‐scale chemical‐physical treatment of sanitary landfill leachate are analyzed. The plant receives approximately 75,000 L/day from a lined 50 acre landfill. The treatment sequence consists of equalization, lime precipitation, sedimentation, and air stripping of ammonia. Overall percent removal efficiencies are ${\mathrm{BOD}}_5\text{,}$ 69; kjeldahl‐N, 53; cadmium, 59; copper, 38; iron, 98; lead, 66; mercury, 52; nickel, 54; zinc, 95, and, suspended solids, 95. Equalization markedly reduces operating costs. The effects of temperature and pH on heavy metals removal are also reviewed.

Automatic control methods are applied to combined sewer systems in order to reduce pollution of receiving waters through maximum utilization of existing storage capacity. Because of the high dimension and complexity of the control problem, a multilayer control structure is developed taking into account practical requirements like moderate computational effort and real‐time evaluation. A constrained discrete dynamical optimal control problem for a simplified form of the overall network is solved online in an optimization layer using the discrete maximum principle and gradient techniques. Resulting optimal state and control trajectories are used as reference trajectories for the decentralized control of small subnetworks. Prediction of runoff trajectories are provided by a supremal adaptation layer. Efficacy of the control system is demonstrated by application to a practical problem.

The upward transport of phosphorus through the lower portion of the metalimnion of hypereutrophic Onondaga Lake, mediated by vertical diffusivity, was estimated for a productive seven month period during 1980. This upward flux was simulated by Fickian diffusion, which incorporates estimates of the vertical diffusivity coefficient for heat and measurements of the vertical phosphorus gradient. The field and laboratory analytical program included thermal profiles and dissolved phosphorus fractions from depths bracketing the metalimnion. Samples were collected on 53 dates during the study period. Two different time segmentations, approximately semimonthly and monthly, were utilized in the determination of the vertical diffusivity coefficient. The turbulent component of vertical diffusivity demonstrated a strong seasonality during the stratification period, varying from $0.060{\mathrm{cm}}^2{\sec }^{-1}$ in early summer to $0.002{\mathrm{cm}}^2{\sec }^{-1}$ during the maximum stability period of late summer. The total dissolved phosphorus gradient increased during stratification to a maximum of $0.14\mathrm{mg}\cdot L^{-1}\cdot m^{-1}$ in late August and early September. The internal loading of phosphorus to the epilimnion from diffusivity‐based transport during the study was approximately 21% and 18%, respectively, of the external loading of dissolved and total phosphorus. The elimination of the present industrial ionic loading to the lake could result in increased internal loading of phosphorus through vertical transport by as much as a factor of 7.

Vertical oxygen profiles of lakes are typically insensitive to the rate of reaeration across the air-water interface when non-eddy diffusivity dominates epilimnetic waters. Steady-state models are developed to analyze the dependency of oxygen regimes upon the reaeration coefficient, the diffusivity coefficient, and the rate of oxygen consumption. For example, an oxygen model is insensitive to a reaeration coefficient of greater than 1 m/d if the vertical diffusivity coefficient is less than 1 m²/d. Other combinations can be analyzed using the models developed.

Factors influencing the shape of oxygen profiles in the epilimnetic and hypolimnetic waters of lakes and reservoirs are analyzed. A vertical one-dimensional model of others applied to Fontana Reservoir is used in the analysis. Epilimnetic dissolved oxygen is controlled by molecular diffusivity and vertical currents induced by inflow-outflow differences. Deep hypolimnetic oxygen regimes can be explained by sediment oxygen demand and by incomplete overturn during the previous autumn.

The distance between the potential waste transfer station site and disposal site determine the viability of using a transfer station rather than the distance between the collection area and the disposal site as currently practiced. Proof to the above statement is given using a detailed cost analysis.