Journal of Environmental Engineering

This paper was presented as the Simon W. Freese Lecture at the 2000 ASCE Annual Meeting in Kansas City, Kansas, July 24, 2000. It is obvious that an increasing global population with aspirations for a higher standard of living is significantly altering our natural systems. This affects the quality and quantity of life on earth. Technology is both partially the cause and a critical component of a future solution. Have engineering schools incorporated the topic of sustainability in meaningful ways? This paper attempts to answer this question. Findings are based on published literature and two questionnaires. The first survey went to environmental engineering faculty via the 724 Members of the Association of Environmental Engineering and Science Professors. Twenty two responses were received. The second questionnaire was sent to 600 U.S. based environmental professionals employed by Environmental Resources Management (ERM) as representatives of recent graduates. The paper concludes that the faculty believes that teaching principles of sustainability is important, even though many are generally ill informed, and that graduates should have a basic understanding, but they don’t. Although many colleges offer courses, only a few appear to be seriously incorporating sustainability concepts.

Current research focuses on the simultaneous removal of Cd and Cr(VI) in water by a newly developed material having both abilities of sorption and electrochemical reduction. The material was derived from the zeolite modified by Fe(II) chloride followed by sodium borohydride reduction. The Fe-loaded zeolite simultaneously removed Cd and Cr(VI) to below the detection limit at a fairly rapid rate within $1\mathrm{h}$ for Cd and within $20\mathrm{h}$ for Cr(VI), under the pH ranging from slightly acid to around neutral. At high concentration of coexisting Cr(VI), the removal efficiency of Fe-loaded zeolite for Cd slightly decreased due to surface fouling by Cr(III) hydroxide precipitations. On the contrary, the coexisting Cd was found to increase the removal rate of Cr(VI) by Fe-loaded zeolite. From the test results, the Fe-loaded zeolite was found to be a possible alternative in simultaneous removal of Cd and Cr(VI) in the aqueous phase.

Nitrogen (N), phosphorus (P), and carbon (C) flux through a three pond wastewater stabilization system (WWSP) was measured over the course of a year in a cold weather region (Minnesota) with $4\text{months}$ of ice cover. The system was surprisingly efficient at N removal (averaging 80%) primarily through volatilization of un-ionized ammonia during the late spring when the pH was above 8 and ammonia levels were still high. P removal was less efficient, with over 50% of influent P leaving the system in the effluent. Soluble carbonaceous biochemical oxygen demand (CBOD) removal was $>90\%$ , with most of the removal occurring in the primary pond. Algal carbon requirements were met by a combination of $\mathrm{C}{\mathrm{O}}_2$ released by bacterial oxidation of influent organic matter and inorganic carbon in the influent. Photosynthesis provided much of the oxygen needed for CBOD removal in the primary pond, and the onset of aerobic conditions was nearly coincident with the highest rates of ammonia volatilization. Bacterial respiration in the sediment returned $>80\%$ of the sedimented C back to the water column long term. These results demonstrate the importance of ammonia volatilization as a N sink in WWSPs that experience ice cover setting up conditions for both high primary production and high ammonia levels in spring.

In a packed-bed reactor grains of the calcium silicate mineral wollastonite dissolved incongruently. A silicon-rich residue layer appeared to form on the grain surfaces and this quickly limited the overall rate of mineral dissolution. Approximately 54% of the silicon associated with the dissolved calcium was retained on the grains and about 46% went into solution with the calcium. As the amount of Ca dissolved per unit area of grain surface approached approximately $0.5\mu \mathrm{mol}∕{\mathrm{cm}}^2$ the effluent concentration of Ca decreased to a value that was significantly less than the equilibrium concentration (approximately $300\mu \mathrm{mol}∕\mathrm{L}$ ) and the effluent pH decreased from approximately 10 to slightly greater than the influent value of 6.8. The effluent Ca and Si concentrations were effectively predicted by a finite difference model that used layer-by-layer calculation of a residue layer mass transfer resistance (for the Ca ion) acting in series with an extraparticle mass transfer resistance. The effluent pH was predicted using chemical equilibrium calculations and the assumption that the dissolved Si controls the proton balance across the column.

From the performance data of the upflow sludge bed (USB) reactors (with sufficient carbon), the rate-limiting step in denitrification is nitrate reduction. Biological denitrification in the USB reactors (superficial velocity=0.5, 1.0, 2.0, and 4.0 m/h) can be greatly enhanced with sludge wasting from the bioreactor [i.e., maintain granular sludge retention time (GSRT) at 20 days], including high volumetric loading rates of up to 6.61 g ${\mathrm{NO}}_3^{-}$ –N/L day, high specific denitrification rates [arithmetic mean=0.31–0.42 g $\mathrm{N}{\mathrm{O}}_3^{-}$ –N/g volatile suspended solids (VSS) day], high denitrification efficiencies (97.6–97.8%), and relatively low washout rates of biomass granules (arithmetic mean $\omega$  =0.13–0.31 g VSS/L day). The biomass concentration, average granule size ( $d_p$ ), and microbial density of the USB reactors with sludge wasting were greater than those of the USB reactors without sludge wasting (i.e., the former grew more compact granules than the latter). From the granulation experiment, the granule size distribution and $d_p$ of the broken-up granules in the sludge-bed zone can restore to those of the original granules in one GSRT, implying that spontaneous flocculation of extra-cellular polymer of denitrifying-bacteria cells occurred in the USB reactor, which may also be accelerated by a rigorous backing-mixing effect of continuous production of biogas. Accordingly, the USB reactor with sludge wasting can be regarded as a promising alternative to treat high-strength nitrate wastewater.

The experimental studies conducted at the Hanover-Gümmerwald pilot wastewater treatment plant (WWTP) focused on minimizing nitrogen loads discharged during stormwater events. The data collected during the plant operation were used for a long-term process simulation. The aim of this study was to compare predictive capabilities of two different mechanistic models (ASM2d and ASM3P) in terms of nitrogen removal. The influent wastewater composition was generated using on-line measurements of only three parameters (COD, $\mathrm{N}–\mathrm{N}{\mathrm{H}}_4^{+}$ , $\mathrm{P}–\mathrm{P}{\mathrm{O}}_4^{3-}$ ) and the model predictions were primarily compared with on-line data (concentrations of $\mathrm{N}–\mathrm{N}{\mathrm{H}}_4^{+}$ , $\mathrm{N}–\mathrm{N}{\mathrm{O}}_3^{-}$ ) originating from the aerobic zone of the bioreactor. The simulation results confirmed the experimental data concerning the capabilities of the system for handling increased flows during stormwater events. The predicted peaks of $\mathrm{N}–\mathrm{N}{\mathrm{H}}_4^{+}$ at the line with the quadruple dry weather flow rate were normally exceeding $8\mathrm{g}\mathrm{N}\bullet {\mathrm{m}}^{-3}$ (similar to the observations), whereas no (or minor) peaks of $\mathrm{N}–\mathrm{N}{\mathrm{H}}_4^{+}$ were predicted for the line with the double dry weather flow rate. The relationships between ASM2d and ASM3P predictions for $\mathrm{N}–\mathrm{N}{\mathrm{H}}_4^{+}$ and $\mathrm{N}–\mathrm{N}{\mathrm{O}}_3^{-}$ were highly correlated $(r^2=0.83–0.99)$ with the slopes remaining close to 1.0. Both models appear to be equally suitable for practical applications in common municipal WWTPs.

Batch bioassay tests were conducted to evaluate the effect of particulate chemical oxygen demand (COD) $\left({\mathrm{COD}}_P\right)$ on anaerobic digestion of wastewater at different ratio of food to microorganism $(F∕M)$ . Synthetically prepared soluble and complex wastewaters were used. Experiments were conducted in seven sets of serum bottles maintained at $F∕M$ ranging from 0.18 to 2.0. Each set contained six bottles having a total COD $\left({\mathrm{COD}}_T\right)$ of 500 mg and ${\mathrm{COD}}_P$ from 0 to 100%. Methane generation conforms to the first order rate kinetics. At all $F∕M$ , $k\left({\text{day}}^{-1}\right)$ decreased linearly with increase in fraction of ${\mathrm{COD}}_P({\mathrm{COD}}_{\mathrm{PF}}={\mathrm{COD}}_P∕{\mathrm{COD}}_T)$ . Biomethane potential (BMP), and substrate and sludge activities also exhibited declining trend with increasing ${\mathrm{COD}}_{\mathrm{PF}}$ . The optimum value of $F∕M$ ranged from 0.57 to 0.68. The two variables, ${\mathrm{COD}}_{\mathrm{PF}}$ and $F∕M$ , were compounded to yield the ratio of ${\mathrm{COD}}_P$ to microorganisms [ $M$ , measured as volatile suspended solids (VSS)]. On increasing the ${\mathrm{COD}}_P∕\mathrm{VSS}$ from 0 to 0.9, the rate constant for methane generation is reduced by 81%. ${\mathrm{BMP}}_{30}$ , percent sludge activity, and substrate utilization rate are lowered by 52–55%. These correlations could serve as useful guidelines to quantitatively assess the impact of particulate COD on biodegradability parameters.

Electronic waste (E-waste), including all obsolete electronic products, has become the fastest growing component in the solid waste stream. Personal computers (PCs)—the most significant component in E-waste stream—were studied for their potential leaching toxicity of contaminants. All the components in a PC that are composed of, or contain printed wire boards (PWBs) including the motherboard, various expansion cards, disk drives, and power supply unit were tested by the toxicity characteristic leaching procedure (TCLP). The total contents of eight heavy metals including arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver in the PWBs and their TCLP leaching from the PWBs were examined. Among these eight heavy metals lead was found to be the predominant element that causes the toxicity characteristic of the PC components. The lead concentrations in the TCLP extracts of the vast majority of the PWBs ranged from 150 to $500\mathrm{mg}∕\mathrm{L}$ , which are 30–100 times the regulatory level of $5\mathrm{mg}∕\mathrm{L}$ for classifying a waste as hazardous. The motherboard in a PC contributed 50–80% of the total lead that could leach out from all the PWBs in the PC under the TCLP test conditions. The contents of barium and silver were found to be high in some components, but they were not leachable under the TCLP test conditions. The contents of other five elements in all the PC components were hardly detectable. They would not have the potential to cause toxicity characteristic leaching concern.

Capping is a common remediation technology for the containment/stabilization of contaminated sediments. During capping activities, clean material is commonly released from a barge at the water surface and falls through the water column to the sediment surface, providing an uncontaminated surface sediment layer. Little information exists on the potential release of in situ contaminated sediments during and after capping operations. This paper focuses on the measured release of contaminants during capping events at Boston Harbor, Mass. (confined aquatic disposal cells for contaminated sediment) and Eagle Harbor, Wash. (creosote-contaminated sediment from a wood treating facility). The water column was sampled during capping events to evaluate whether cap placement resulted in the release of polycyclic aromatic hydrocarbons (PAH)- or polychlorinated biphenyls (PCB)-contaminated sediments at Boston Harbor, or PAH-contaminated sediments at Eagle Harbor. Though results at both sites indicated some contaminant resuspension during capping operations, in general contaminant resuspension was relatively low for all capping events. PCB and PAH concentrations for most samples were in the low $\mathrm{ng}∕\mathrm{L}$ range. The most significant releases occurred when previously uncapped sediments were initially capped, and the magnitude of contaminant resuspension decreased with successive capping layers. These results may have important implications regarding sediment cap installation techniques and their potential impacts on water quality. Resuspension during capping may be minimized by placing cap material in lifts, where the first lift provides a uniform layer of clean material using techniques that minimize sediment disturbance and subsequent lifts are placed more aggressively once contaminated sediment is covered.

The Island Copper Mine pit near Port Hardy, Vancouver Island, B.C., Canada, was flooded in 1996 with seawater and capped with fresh water to form a meromictic (permanently stratified) pit lake of maximum depth 350 m and surface area $1.72{\mathrm{km}}^2$ . The pit lake is being developed as a treatment system for acid rock drainage. The physical structure and water quality has developed into three distinct layers: a brackish and well-mixed upper layer; a plume stirred intermediate layer; and a thermally convecting lower layer. Concentrations of dissolved metals have been maintained well below permit limits by fertilization of the surface waters. The initial mine closure plan proposed removal of heavy metals by metal–sulfide precipitation via anaerobic sulfate-reducing bacteria, once anoxic conditions were established in the intermediate and lower layers. Anoxia has been achieved in the lower layer, but oxygen consumption rates have been less than initially predicted, and anoxia has yet to be achieved in the intermediate layer. If anoxia can be permanently established in the intermediate layer then biogeochemical removal rates may be high enough that fertilization may no longer be necessary.

Measuring the heavy metal burden of “old contamination” soils (soils with aged contamination) can be challenging. Many laboratory procedures are currently in use and these can yield a wide range of burden estimates for the same soil. The appropriate extraction method selection depends on the intended use of the information and on compatibility with the procedures used to generate the “reference” data to which results are compared. In this work, results for an extraction based on the electrokinetic mobilization of old contamination heavy metals were compared to the results of established single analyte and sequential extraction methods. Accomplishing extractions electrokinetically offers promise for simplifying processes and for evaluating the electrokinetic remediation potential of old contamination soils. On the brownfield soils tested, electrokinetic extraction identified an average of 82% of the soil’s Cr, Cu, Pb, and Zn burden relative to Environmental Protection Agency Method 3050B extractions. However, results also indicated that neither of these methods were successful at extracting all of the sequestered (residual) fraction of heavy metals and thus underestimated the total contamination burden of the soil.

Often, the initiation of a total maximum daily load (TMDL) program is delayed until intensive monitoring data can be collected—even in watersheds where large historical data sets exist. This paper provides a case study of a modeling effort that utilizes available historical data to fulfill an intermediate goal of a TMDL program for the Passaic River Basin. The subject model is developed to simulate total phosphorus concentrations (and loads) within the basin’s effluent-dominated streams. The model is based on the assumption that the primary process controlling in-stream total phosphorus concentrations is the dilution of the cumulative upstream effluent load—which was computed on a continuous (daily) basis. Model comparisons indicate a generally good fit to long-term river-monitoring data at several key sites. Model results, and data analyses, suggest that secondary processes have a relatively minor impact on total phosphorus (TP) concentrations in this relatively large, urbanized system. This finding is consistent with a previous QUAL2E model study of the system, and consistent with the relatively conservative behavior of TP reported in many medium-to-large river systems throughout the United States. Model results are used to facilitate TMDL planning efforts for a major water supply reservoir in the basin.

Long-term nonpoint source (NPS) pollutant flux is described within the rapidly developing Occoquan watershed west of Washington, D.C. Data consist of up to 24 years of observed rainfall, integrated pollutant discharge, and land use/land cover from four headwater basins of the Occoquan River. Three of the four study basins, ranging in size from 67 to $400{\mathrm{km}}^2$ , are predominantly forest and mixed agriculture. The fourth basin, the $127{\mathrm{km}}^2$ Cub Run watershed, has urbanized rapidly over the past 20 years. Higher annual NPS sediment and nutrient fluxes in Cub Run after 1983 are linked to increased soil disturbance from urban construction and increased storm volumes resulting from increased mean impervious percent. Over the long-term, storm fluxes of NPS particulate P, soluble P, particulate N, and soluble N make up 92, 67, 89, and 50%, respectively, of the total fluxes of those constituents, with between 88 and 98% of mean annual total suspended solids fluxes delivered by storm flow. Higher NPS pollutant fluxes in Cub Run basin after 1983, and specifically during the growing season, indicate a seasonal impact of replacing vegetated cover with impervious surface.

This paper presents a hydrodynamic and water quality modeling system for Wissahickon Creek, Pa. Past data show that high nutrient levels in Wissahickon Creek were linked to large diurnal fluctuations in oxygen concentration, which combining with the deoxygenation effect of carbonaceous biological oxygen demand (CBOD) causes violations of dissolved oxygen (DO) standards. To obtain quantitative knowledge about the cause of the DO impairment, an integrated modeling system was developed based on a linked environmental fluid dynamics code (EFDC) and water quality simulation program for eutrophication (WASP/EUTRO5) modeling framework. The EFDC was used to simulate hydrodynamic and temperature in the stream, and the resulting flow information were incorporated into the WASP/EUTRO5 to simulate the fate and transport of nutrients, CBOD, algae, and DO. The standard WASP/EUTRO5 model was enhanced to include a periphyton dynamics module and a diurnal DO simulation module to better represent the prototype. The integrated modeling framework was applied to simulate the creek for a low flow period when monitoring data are available, and the results indicate that the model is a reasonable numerical representation of the prototype.

Odors arising from hot mix asphalt (HMA) production and application are a serious problem due to the proximity of HMA production to human habitation. One possible solution to this problem is the use of odor-reducing agents, which are intended to suppress the production of malodorous compounds. In this study, the ability of seven odor-reducing agents to reduce the odor compounds produced by 22 different HMA binders was quantified. Some odor-reducing agents produced only modest reductions in odors and were inconsistent in performance. Results indicate that terpine and essential oil based odor reducing agents did not appear to be effective in reducing odors. The aldehyde based agents attained the highest degree of odor reduction and appeared to be the most consistent performer over the spectrum of asphalt binders tested. Aldehydes produced reductions in odor potential that consistently exceeded 50% in odor-related volatile organic compounds. The odor reduction seen with the aldehydes is similar to those obtained with a nitrogen purge, leading to the hypothesis that these type of agents act as an oxygen scavenger.

Rock filters used to treat effluents from waste stabilization ponds do not remove ammonia as they are anoxic. A pilot-scale aerated rock filter was investigated, in parallel with an unaerated control, over an $18\text{-}\text{month}$ period to determine whether aeration provided conditions within the rock filter for nitrification to occur. Facultative pond effluent containing $\sim 10\mathrm{mg}$ $\mathrm{N}{\mathrm{H}}_4–\mathrm{N}∕\mathrm{L}$ was applied to the filters at a hydraulic loading rate of $0.15{\mathrm{m}}^3∕{\mathrm{m}}^3\text{day}$ during the first $8\text{months}$ and at $0.3{\mathrm{m}}^3∕{\mathrm{m}}^3\text{day}$ thereafter. The results show that the ammonia and nitrate concentrations in the effluent from the aerated filter were $<3$ and $\sim 5\mathrm{mg}\mathrm{N}∕\mathrm{L}$ , respectively, whereas the ammonia concentration in the effluent from the control filter was $\sim 7\mathrm{mg}\mathrm{N}∕\mathrm{L}$ . Fecal coliforms were reduced in the aerated filter to a geometric mean count of $65\text{per}100\mathrm{mL}$ ; in contrast the effluent from the control filter contained ${10}^3–{10}^4$ fecal coliforms per $100\mathrm{mL}$ . Aerated rock filters are thus a useful land-saving alternative to aerobic maturation ponds.