Journal of Environmental Engineering

Oxygen transfer is an important part of wastewater treatment and accounts for as much as 60% of energy consumption in the activated sludge process. Prior to 1984, no standard method for quantifying oxygen transfer existed, which created problems in the design and warranties for treatment plants. The ASCE standards for the measurement of oxygen transfer in clean water and the Standard Guidelines for In-Process Oxygen Transfer Testing have found widespread application and have reduced design variability. The standard has allowed operators and engineers to better evaluate process operation of existing treatment plants. This paper illustrates the key concepts of the standard and shows why they are important and how they reduce the variability of oxygen transfer testing. The reasons for the standard’s success are described, as are the pitfalls of earlier approaches. The paper also highlights key new areas of the revised clean water standard, including an optional correction for test water total dissolved solids concentration and applications to the loop (ditch) activated sludge process and the high-purity-oxygen activated sludge process. Finally an analysis is presented that shows how numerical treatment of the transfer data minimizes the impact of gas-side oxygen depletion.

Recent concerns about excessive algal (Cladophora) growth in the nearshore area have prompted a comprehensive study of phosphorus concentrations and loads in the Milwaukee watershed (2000–2008). During this period, total phosphorus (TP) decreased slightly for Outer Harbor water monitoring Station 1 (OH-1) representing the confluence of the three rivers into the Outer Harbor; whereas TP remained the same or slightly increased for Outer Harbor water monitoring Station 2 (OH-2) near the Jones Island Water Reclamation Facility (WRF) outfall. Concentrations of TP at OH-2 ($0.095\pm 0.005\mathrm{mg}/\mathrm{L}$) are higher than at OH-1 ($0.073\pm 0.006\mathrm{mg}/\mathrm{L}$). Years with high rainfall and river discharge during May through June produce high daily and annual average TP loads. This appears to be caused by resuspension and erosion of sediments containing TP in the river beds. Jones Island WRF contributes $39,500\mathrm{kg}/\mathrm{year}$ or less than 34% of the total load to the Harbor. An estimate of TP load to Lake Michigan from rivers is $76,500\mathrm{kg}/\mathrm{year}$ (65.7%). Stepwise regression results show that total soluble phosphorus (TSP), total suspended solids (TSS), and biochemical oxygen demand (BOD), in that order, are important predictors of TP except for Station OH-2.

It has been a challenge to couple a stream channel system with adjacent wetlands and to simulate their interactions and the dynamic processes associated with water flow, sediment movement, and contaminant transport. In this study, a physically based model was developed for simulating metal and sediment transport in a coupled stream-wetland system that consisted of the water column, the underlying active bed, and the adjacent wetland subsystems. The model simulated the dynamic interactions and mass exchanges (water, sediment, and metal) between subsystems and accounted for a set of processes related to the two-phase (dissolved and adsorbed phases) metal and sediment transport, including advection, dispersion/diffusion, sorption, settling, resuspension, and sedimentation. The integrated metal-sediment transport model was solved by using a semidiscrete method. Model simulations of cadmium fate and transport were tested against field data from Little Black Creek (LBC) in western Michigan, which was heavily impacted by historic discharges of cadmium originated from metal plating operations. The preliminary modeling results emphasized the important roles of the cadmium-contaminated sediments in cadmium transport in the stream-wetland system (e.g., accumulation in streambed sediments and release through resuspension) and the potential of heavy metal accumulation in Mona Lake, which received discharge from LBC and the adjacent wetlands.

Biocovers constitute a promising technology to reduce fugitive and residual emissions from landfills throughout their operational life and after gas collection systems are turned off. The aim of this study was to assess the efficiency of two substrate materials in oxidizing ${\mathrm{CH}}_4$ into ${\mathrm{CO}}_2$ under field conditions and in the laboratory (column tests). The two substrates evaluated were: 1) a mixture of sand and compost, and 2) the same sand-compost mixture with gravel added. The oxidation rates obtained in the field attained a maximum of $576\mathrm{g}{\mathrm{CH}}_4{\mathrm{m}}^{-2}·{\mathrm{day}}^{-1}$ for one of the substrates and $352\mathrm{g}{\mathrm{CH}}_4{\mathrm{m}}^{-2}·{\mathrm{day}}^{-1}$ for the other, with oxidation efficiencies nearly of 100%. These maximum values were much higher than those obtained in the laboratory: 115 and $118\mathrm{g}{\mathrm{CH}}_4{\mathrm{m}}^{-2}·{\mathrm{day}}^{-1}$, respectively, for an oxidation efficiency of 96% in both cases. The exact causes for the discrepancy between field and laboratory results were not identified, but it was hypothesized that vegetation on the surface of the passive methane oxidation biocovers (PMOBs) greatly improved methane oxidation efficiencies in the field.

An overlay of porous asphalt known as permeable friction course (PFC) is an innovative roadway material that improves both driving conditions in wet weather and water quality. Placed in a layer 25–50 mm thick on top of regular impermeable pavement, PFC allows rainfall to drain within the porous layer rather than on top of the pavement. This paper presents water quality measurements for PFC and conventional pavement collected over six years near Austin, TX and two years in eastern North Carolina. The data show that concentrations of total suspended solids from PFC are more than 90% lower than from conventional pavement. Lower effluent concentrations are also observed for total amounts of phosphorus, copper, lead, and zinc. The combined data sets show that PFC’s benefits last through the design life of the pavement, that results in Texas are consistent with those from North Carolina, and that both are consistent with earlier studies from France, the Netherlands, and Germany.

Methoprene larvicide is a biochemical insect growth regulator used in North America to control the mosquito population. It can be incorporated in clay pellets or chalks and dropped into a catch basin sump. The slow release mechanism of methoprene has the potential to inhibit the growth of mosquito larvae into pupae in the sump and reduce the emergence of adult mosquitoes. As a result, the vector transport of the West Nile virus can be minimized. The main concern is whether or not the methoprene pellets or ingots will remain in a catch basin sump or be flushed during storm events, resulting in ecological impacts on the receiving waters. A full-scale physical model was constructed to investigate the flushing characteristics of methoprene pellets and chalks in a catch basin. It was found that (1) the sump water could provide a cushion against the hydraulic turbulence of inflows and trap the pellets and ingots; (2) flushing of pellets or ingots was more sensitive to the critical inflow magnitude than the time to reach this flow; (3) ingots would require a higher inflow to be flushed than would pellets; and (4) sediments and leaves at the sump might inhibit the flushing of pellets. Using the measured critical inflow rate at which pellets and ingots were flushed in the experiments, it was found that a 3-month storm and 1.4-year storm in Toronto might have the potential to flush out pellets and ingots respectively in a catch basin filled with sediments. Additionally, the risk of flushing pellets over the summer months may be high when the sump water depth of a catch basin is shallow. On the other hand, the risk of flushing ingots over the summer months is low. As a result, ingots should be used in larviciding catch basins.

As is known, zinc pollution has been a public environmental issue for a long time. Accordingly, the major objective of this study is to examine the effect of activated Firmiana simplex leaf on Zn(II) removal from aqueous solution. The result shows that activated Firmiana simplex leaf can remove Zn(II) effectively at 250°C due to the preservation of amine, carboxyl, and phosphate groups. Several factors were determined to have significant effects on the adsorption of Zn(II), including the adsorbent component, dosage, initial concentration, solution pH, temperature, and duration. Pseudo first order and pseudo second order kinetics equations were used to predict the kinetic and thermodynamic constants that reveal the endothermic and spontaneous nature of the adsorption. Using the Langmuir model, the maximum zinc adsorption capacity was calculated to be $55.096\mathrm{mg}/\mathrm{g}$, which was subsequently confirmed by Fourier transformed infrared radiation (FT-IR) analyses and X-ray diffraction (XRD) spectra.

This study aims to improve a decontamination process developed for chromated copper arsenate (CCA)-treated wood waste. This process included metal extraction from the wood by a sulphuric acid-leaching step, and the treatment of metal-loaded leachate by precipitation with ferric chloride and sodium hydroxide. This study showed that sodium hydroxide can be advantageously replaced by calcium hydroxide to enhance performance ($>99\%$ metal precipitation above pH 6.5 with $\mathrm{Ca}(\mathrm{OH}{)}_2$ and above pH 7 with NaOH) and lower chemical costs [US$30.8/ton of treated wood (TTW) with $\mathrm{Ca}(\mathrm{OH}{)}_2$ instead of US$50.83TTW with NaOH]; however sludge production and sludge disposal cost were higher when using $\mathrm{Ca}(\mathrm{OH}{)}_2$ for precipitation. Moreover, this study investigated the possibility of recycling the final process effluent obtained after metallic sludge separation. This effluent was successively reused in the process for the leaching step. Five recycling loops comprised of one leaching step, one precipitation step of the leachate with $\mathrm{Ca}(\mathrm{OH}{)}_2$, and three rinsing steps were conducted. Arsenic removal from the wood varied from 96 to 98%, chromium removal from 91 to 93% and copper removal from 95 to 96%. Metal removal stayed relatively stable along the five loops, meaning that process water recycling did not influence metal extraction. Leachate treatment with calcium hydroxide and ferric chloride was efficient and allowed, beside metals precipitation, DOC and sulfate partial removal. This avoided fast accumulation of these compounds in the system.

A factor that impedes the practicability of environmental models is a lack of confidence in system performance stability in the face of uncertainty. This paper presents the development and application of a fuzzy radial interval programming (FRIP) approach for identifying waste diversion plans under uncertainty. FRIP allows uncertain parameters in the formats of radial intervals, conventional intervals, and fuzzy sets to be directly communicated into the optimization process. It can be protected against numerous input fluctuations, generating robust solutions that remain optimal in spite of divergent subjective judgments and changing objective conditions. More importantly, such conservativeness in solutions is proactively adjustable by changing protection levels of constraints according to site-specific features and stakeholders’ expectations, avoiding a significant adverse effect on the system optimality. Other capacities of FRIP include a prior quantification of risks associated with solutions, fulfillment of uncertain management goals, and flexibility in the constraints, so that higher public acceptance and easier implementation of the generated schemes can be achieved. A computationally tractable interactive solution algorithm was also proposed for FRIP. The developed methodology has been applied to a representative waste-management case. More than 20 sets of interval solutions were obtained under varied protection levels, asserting that FRIP could help managers make robust and flexible decisions without sacrificing the economic interests to any great extent. The sensitivity analysis of fluctuation radii further verified their significant impacts on the system. FRIP was also compared to potential alternative models to demonstrate its superiority.

The authors analyze runoff and road salt delivery and loading data from an indoor salt storage facility in eastern Massachusetts over multiple deicing seasons. The facility converted its delivery/loading from outdoors to indoors. Data and simple theory document a fivefold decrease in spillage as a result of the conversion. A seasonally varying balance of first order dissolution and a spill fraction is used to quantify the improvement; the data and model suggest that 0.3% of the outdoor delivered/loaded road salt spilled onto the pavement. The conversion to indoor delivery/loading reduced the spillage fraction to 0.06%.