Christopher G. Uchrin

An oxygen equivalent model for water quality dynamics in a macrophyte dominated river

Abstract A water quality modeling study was performed in a macrophyte dominated river. A computer model, MACRIV (macrophyte growing river) was formulated to incorporate diurnal dissolved oxygen variations and nutrient uptake/recycle caused by all aquatic plants, including macrophytes. In this model, the aquatic plant is represented as an equivalent amount of dissolved oxygen by reach, which varies diurnally as well as seasonally depending upon solar radiation, temperature, and nutrients. The solar radiation is computed in the model based on the latitude, Julian day, and real-time of day. The model simulates seven coupled state variables (BOD (CBOD or 5-day BOD), DO (daily average value or diurnal variation), organic nitrogen, ammonia nitrogen, nitrite/nitrate nitrogen, total organic phosphorus, dissolved inorganic phosphorus (DIP)) and two non-coupled variables (a first-order decay substance, and a conservative substance). Through a stoichiometric relationship between plant protoplasm and physiological processes including photosynthesis, respiration, and death, the water quality variables interacting with aquatic plants are computed in the model. The model was calibrated and verified against data collected from an impounded river in which macrophytes play an important role in defining water quality dynamics. There were reasonable agreements between model predictions and the field measurements both for steady-state water quality and diurnal dissolved oxygen. The overall study demonstrated that the developed MACRIV model can simulate the most important parameters involved in waste load allocation studies in macrophyte growing rivers, such as diurnal DO variation, BOD (autochtonous and allochtonous), ammonia toxicity, and nutrient dynamics.

Ultrafiltration processes for the characterization and separation of landfill leachates

Abstract Ultrafiltration is demonstrated to be an effective method for characterizing industrial landfill leachates by molecular weight (MW) distribution. The majority of the organic matter (as TOC and COD) for the hazardous wastes examined was found to be below 500 MW. The applicability of ultrafiltration as an effective process for removal of low MW organic matter from industrial wastes is limited. Ultrafiltration, however, is useful as a pretreatment process for removal of large MW compounds that interfere with subsequent treatment processes. Ultrafiltration of raw landfill leachates is hindered by concentration polarization and severe fouling. Physiochemical lime treatment of the highly turbid raw leachate was found to aid in the stabilization of product flux.

Estimating Exposure Using Kriging: A Simulation Study

Retrospective studies of disease often are limited by the resolution of the exposure measurements. For example, in a typical study of adverse health effects from contaminated groundwater, the number of wells sampled may range from only a few to as many as several dozen, while the number of cases and controls may be in the hundreds or more. To derive individual estimates of exposure for wells that were not sampled, investigators must extrapolate. In this study, we compare three methods of extrapolating from a limited number of observations to estimate individual exposures. Using two naive models of groundwater contamination, we compare nearest neighbor interpolation, inverse distance squared weighting, and kriging for estimating exposure based on a limited number of measurements. Our results show that although kriging is a statistically optimal method, it is not markedly better than simpler interpolation algorithms, though it is considerably more complex to use. Aberrant well measurements and discontinuities are problematic for all methods. We provide some guidance in interpolating data and outline a more comprehensive comparison of methodology.

A stoichiometric model for water quality interactions in macrophyte dominated water bodies

Abstract A computer model, SIREM1, which incorporates water quality interactions of aquatic plants including planktonic algae, periphyton, and macrophytes is presented in this paper. In this model, the total amount of aquatic plants is represented dynamically as an oxygen equivalent, dependent upon available solar radiation. Through the stoichiometric relationship between plant protoplasm and processes including photosynthesis, respiration, and death, nutrients and autochthonous organic matter are computed based on simulated oxygen equivalents. The model was applied to an impounded stream where macrophytes played an important role in water quality dynamics. There was good comparison between model prediction and actual observations. The results indicate that the time variable oxygen equivalent concept for aquatic plants could be a useful approach for simulating the function of aquatic plants in diurnal dissolved oxygen variations, nutrient uptake/recycle, and the generation of autochthonous organic matter.

The study of dissolved oxygen dynamics in the Whippany river, New Jersey using the QUAL2E model

Abstract An intensive water quality study of the lower Whippany River, located in northeastern New Jersey, was performed examining dissolved oxygen, biochemical oxygen demand, sediment oxygen demand, photosynthesis, river hydrology, geomorphology, and major inputs. Dissolved oxygen dynamics were studied using the USEPA Enhanced Stream Quality Model “QUAL2E”. Model validation was performed using field data collected during 1980 and 1985 summer, low-flow surveys. The computed values for DO, CBOD and nitrogen species corresponded closely to the actual instream data. DO uptake in the river was found to result predominantly from the biooxidation of carbonaceous and reduced nitrogenous compounds originating from two major municipal point sources: the Morristown and Hanover Sewerage Treatment Plants. Sediment oxygen demand occurring in reaches located immediately below the Morristown Sewerage Treatment Discharge also contributed significantly to DO uptake. The model did predict that by improving effluent quality of two major municipal discharges to 8 mg/l BOD-5 and 2 mg/l ammonia-nitrogen and by reducing the rate of SOD in the river, river DO will exceed 7.0 mg/l at most locations.

Physiochemical pretreatment of landfill leachates using coagulation

Abstract Physiochemical pretreatment of landfill leachate using coagulation was examined and found to be an effective means of reducing turbidity, suspended solids, metals and dispersed oil. Lime was found to be the most effective pretreatment coagulant for treating the landfill leachate examined in this study. A 6.0 g/1 dosage resulted in 98% reduction in turbidity. Reductions in dispersed oil were substantial and were accompanied by small removals of dissolved organic matter. Additionally, many heavy metal species were successfully removed. Polyelectrolyte coagulant aids were found to be useful in increasing the rate of turbidity reduction. Re‐carbonation is suggested, to lower the pH to a range desirable for successive treatment processes.

Modeling and simulation of compressive gravity thickening of activated sludge

Abstract A mathematical model of compressive thickening is developed which is based on Kos’ model yet can be calibrated from measurements of concentration, concentration gradient, and bulk underflow velocity in continuous thickening experiments. The need for sensitivity and difficult measurements such as interparticle pressure or volumetric solids concentration is eliminated. Numerical programs to simulate the model are described. The model was calibrated and tested using steady state continuous thickening experiments. Unsteady state continuous thickening was studied by use of computer simulation of the model. Programs are described for nonlinear regression of the models to continuous thickening column data, and for steady state and unsteady state simulation.

Adsorption of phthalate esters on soil at near saturation conditions.

Abstract Batch studies were performed to determine the adsorption behavior of dimethyl phthalate ester and diethyl phthalate ester on two sandy New Jersey soils at near saturation conditions. One soil had a very low organic matter content (<0.012%) while the other was quite higher (1.33%). Both esters displayed BET type adsorption to the high organic content soil, while little adsorption was displayed to the low organic matter soil. Linear, Langmuir, Freundlich, BET, and a composite isotherm proposed by Marinas and Li were fitted to the data. The composite isotherm fir best in all cases. The diethyl phthalate evidence a greater tendency to adsorb than the dimethyl phthalate.

Waste load allocation for a macrophyte growing impoundment: A combined modeling approach

Abstract A waste load allocation study was performed for the Matchaponix Brook‐Duhernal Lake system, where both free flowing and impounded reaches exist. In an impounded area, macrophytes can play an important role affecting water quality whereas no discernible effects are usually observed in free flowing reaches. Due to the nature of the study system, two models were combined to assess the probable impact on receiving water quality caused by an upstream treated wastewater discharge. The collected water quality and flow data were used to determine the critical ambient conditions. The study demonstrated how the macrophytes growing in the downstream impounded area respond to the upstream waste loads.

Temperature effects on tubificid worms and their relation to sediment oxygen demand

Sediment samples were collected from the Dead River in New Jersey and tested in the laboratory under two temperature conditions, 4°C and 20°C. The study was conducted to determine the effect of worm density on the sediment oxygen demand (SOD) rate and if temperature affects the ability for tubificid worms to deplete dissolved oxygen (DO) from the overlying stream water. The study showed that the DO concentration was affected by tubificid worm density and that higher temperature increased the metabolic activity of the worms.