Journal of Environmental Engineering

A study was conducted to assess the impact of media aging on Cryptosporidium parvum transport and retention in granular filters. Column experiments were conducted with sand, anthracite, and granular activated carbon (GAC) filters. All columns possessed an identical filter design and grain size distribution. Oocyst removal was evaluated with both new and aged media. The variation in performance among new media was attributed to the shape of the tested granular media and to the concentration of extractable metals on the surface of collector grains. Media aging significantly increased the treatment performance of sand (26%) and GAC (31%) but had no influence on the performance of anthracite. This enhanced performance of aged media correlated well with the extent of biofilm development. The best removal performance was observed with aged GAC ($71\pm 2\%$), which supported the highest amount of biomass according to polysaccharide and protein measurements. The results of this investigation are of particular interest because they suggest that media aging increases the removal of protozoan parasites in full-scale granular filters.

The postsedimentation addition of polyaluminum chloride (PACl) was investigated as a means to enhance particle removal efficiency in dual media filtration. The process modification was evaluated in laboratory studies and at the Cornell Water Filtration Plant (CWFP). The PACl was continuously metered into CWFP filter influent to increase concentrations by $0.06–4.2\mathrm{mg}/\mathrm{L}$ (as aluminum) during the filter-to-waste stage of the filter operation cycle to accelerate filter ripening. Lower influent PACl concentrations ranging from $0.056–0.43\mathrm{mg}\mathrm{Al}/\mathrm{L}$ were also continuously applied during filtration. In comparison to a control filter that received no PACl addition, the ripening time required decreased with PACl dose, and the incremental improvement in particle removal during filtration increased with PACl dose. The addition of $0.056\mathrm{mg}\mathrm{Al}/\mathrm{L}$ of PACl (the lowest concentration tested) significantly reduced initial filter ripening time at the CWFP from 10–1.4 h, and effluent turbidity in the test filter over the 77 h filter run was lower than the control filter by an average of 17%. Incremental head loss increase caused by the PACl feed was dose dependent and was negligible for the lowest dosage tested.

This paper presents an innovative Monte Carlo simulation—aided analytical hierarchy process (MC-AHP) approach by integrating the beta-PERT distribution, pairwise comparison, and Monte Carlo simulation. A case study related to non-point-source pollution management in southwest China is used to demonstrate the applicability of the proposed approach. Five alternative best management practices (BMPs) (i.e., constructed wetlands technology, conservation tillage, fertilizer and pesticide management, irrigation management, and livestock grazing management) are evaluated by experts using a number of criteria such as reliability, capital costs, and environmental benefits. Statistical analysis indicates that conservation tillage has the highest score (0.25–0.36) in most replications, and its overlap with the second-best alternative is statistically negligible. Constructed wetlands technology, along with fertilizer and pesticide management, are mostly found as the second- and third-best alternatives, with scores ranging from 0.18 to 0.28 and 0.17 to 0.25, respectively. Compared with the traditional analytic hierarchy process (AHP), the proposed MC-AHP approach addresses the uncertainty resulting from insufficient information and opinion difference in group decision-making problems.

An investigation into an extraction of polychlorinated biphenyls (PCBs) from transformer oil (TO) using different solvents and its dechlorination with visible light was conducted. The extraction experiments showed that dimethyl sulfoxide (DMSO) was the preferable solvent for extraction of PCBs from TO, with an average of 88.79% recovery. Multicycle extractions using DMSO led to 87.93, 11.22, and 0.77% PCBs recovery during the first, second, and third cycles, respectively. Optimization studies indicated that for TO with low concentrations of PCBs, a 5-min shaking time, and a DMSO to TO ratio of $6:1$ is optimal. For higher concentrations of PCBs in TO, the optimum conditions were 30 min of shaking time with a DMSO to TO ratio of $6:1$. Furthermore, water aids in the extraction. PCBs were effectively dechlorinated using visible light in conjunction with sodium borohydride, ${\mathrm{NaBH}}_4$, as a reducing agent. The presence of DMSO did not seem to interfere with the dechlorination.

The heavy metals leaching potential of lime fly ash cements was evaluated for one low loss on ignition (LLOI) and one high loss on ignition ash (HLOI). Three different test methods were used: (1) a standard shaken (stirred) extraction test, (2) a modified shaken extraction test, and (3) a modified EP-TOX test. Testing was conducted on the as-receive ashes and lime fly ash samples cured for 0, 7, 28, and 84 days at 40°C. The results show that such curing time sequences can be used to study the rate of sequestration by the hydration product relative to the rate of leaching from the ash. X-ray diffraction (XRD) was used to characterize the reaction products of cured lime fly ash cements and isothermal calorimetry to study the rates of hydration at 25 and 40°C. The leaching tests results indicate that leachability of some heavy metals is greatly dependent on leachant pH and likewise, the test method used. Furthermore, formation of hydration products throughout the leaching does appear to partially sequester some heavy metals. The XRD shows that major hydration products include ettringite and an unidentified calcium aluminosilicate hydrate (CASH) phase, depending on the ash source. Isothermal calorimetry results indicate that hydrations of LLOI fly ash is measureable at 40°C but slow at 25°C, whereas HLOI fly ash hydrates with much slower yet detectable rates.

Beneficial reuse of coal combustion byproducts, e.g., in highway construction, requires an evaluation of metal leaching potential. Metal leaching from high-carbon fly ash in soil mixes typical of highway embankment construction was evaluated using different soil-fly ash mixtures and three common leaching tests: the water leach test (WLT), the Toxicity Characteristic Leaching Procedure (TCLP), and the column leach test (CLT). The effect of test methodology and pH on Cu, As, and Cr leaching was examined. TCLP concentrations for Cu and As exceeded those from WLTs in the majority of mixtures due to lower pH conditions, while Cr was higher in the WLT for alkaline fly ash mixtures. Maximum CLT concentrations were higher than TCLP and WLT concentrations for the majority of mixtures, but usually decreased rapidly, suggesting that leachate concentrations might initially exceed regulatory limits, but only for a short time. A comparison of leaching results is discussed as a framework for the development of a flexible, integrated leaching protocol incorporating elements of batch and column leach tests to provide more accurate, site-specific leaching predictions given time and cost constraints.

A hollow fiber membrane bioreactor (HFMB) was employed for aqueous-organic two-phase biodegradation of phenol using Pseudomonas putida ATCC 11172, and the results were compared with that in a two-phase partitioning bioreactor (TPPB). Phenol containing 2-undecanone was nondispersively contacted with mineral medium that was inoculated with the bacteria. P. putida in suspension was able to biodegrade inhibitory phenol concentrations at $600–\mathrm{2,000}\mathrm{mg}/\mathrm{L}$ without experiencing severe substrate inhibition. For example, $\mathrm{1,000}\mathrm{mg}/\mathrm{L}$ phenol was completely biodegraded in 46 h at a maximum specific growth rate of $0.49{\mathrm{h}}^{-1}$, whereas the biomass yield and average biodegradation rate were $0.36\mathrm{g}/\mathrm{g}$ and $62\mathrm{mg}/\mathrm{L}·\mathrm{h}$, respectively. Biomass yield and maximum specific growth rate decreased concomitantly with increasing phenol concentration. Phenol removal started at an exponential rate, and subsequently attained a linear profile in nutrient-limited conditions. Unlike conventional two-phase biodegradation systems, HFMB offered a better growth environment for the cells, as evident from the absence of the lag phase. The HFMB was more environmentally friendly and offered ease of operation and analysis that could mitigate the problems of foaming and emulsification that are associated with conventional TPPBs. In evaluating the effects of membrane area on biodegradation rate, the writers found that by doubling the interfacial area, $\mathrm{2,000}\mathrm{mg}/\mathrm{L}$ phenol could be mineralized within 43 h with improved growth and removal rates. For comparable mass transfer flux across the aqueous-organic interface, biodegradation was faster in the HFMB relative to that in TPPB.

Ferrate [Fe(VI)] and alkaline chlorination (AC) were investigated for the treatment of a maritime wastewater (CN, Cd, Cu, Ni, Pb, and Zn) in a seawater matrix. AC reduced CN concentrations but large dosages were required (0.018–0.056 mol CN consumed/mol HOCl). Metal removal occurred during the first stage ($\mathrm{pH}>10$) but the amount of sludge produced was large due to $\mathrm{Mg}(\mathrm{OH}{)}_{2(S)}$ formation. Fe(VI) was effective in oxidizing CN and removing heavy metals to low levels without pH adjustment. Fe(VI) requirements [$0.12\mathrm{mol}\mathrm{CN}/\mathrm{mol}\mathrm{Fe}(\mathrm{VI})$] were higher than those observed for other wastes but are considered more manageable compared with HOCl. Metal removal occurred by adsorption and coprecipitation with Fe(III) oxide, which results from the oxidation of Fe(VI). During staged treatment, metal removal and CN destruction increased [2× for Cd, 3× for Cu, 2.7× for Ni, 0.12 to 0.18 mol CN consumed/mol Fe(VI)]. Fe(III) oxide was relatively easy to separate using ultrafiltration tubular membranes and the amount of sludge produced is much less than what would occur with AC. The Fe(III) oxide was separated using ultrafiltration with the amount of sludge produced much less than AC.

The homogeneous surface diffusion model (HSDM) is widely used for adsorption modeling of aqueous solutions. The Biot number is usually used to characterize model behavior. However, some limitations of this characterization have been reported recently, and the Stanton number has been proposed as a complement to be considered. In this work, a detailed dimensionless analysis of HSDM is presented and limit behaviors of the model are characterized, confirming but extending previous results. An accurate and efficient numerical solver is used for these purposes. The intraparticle diffusion equation is reduced to a system of two ordinary differential equations, the transport–reaction equation is discretized by using a discontinuous Galerkin method, and the overall system evolution is integrated with a time-marching scheme. This approach facilitates the simulation of HSDM with a wide range of dimensionless numbers and with a correct treatment of shocks, which appear with nonlinear adsorption isotherms and with large Biot numbers and small surface diffusivity modulus. The approach is applied to simulate the breakthrough curves of granular ferric hydroxide. Published experimental data is adequately simulated.

Electrokinetic experiments were undertaken to transport permanganate (${\mathrm{MnO}}_4^{-}$) through a low permeability porous media. The experiments employed a one-dimensional apparatus in which ${\mathrm{MnO}}_4^{-}$ was electromigrated through a central porous media core. Two outer porous media cores separated the electrode reservoirs from the inner permanganate source and permanganate target reservoirs. By utilizing a pH-isolation technique, whereby electrolysis reactions occurring at electrodes were isolated, uniform and repeatable ${\mathrm{MnO}}_4^{-}$ electromigration was achieved. This result was compared with non-pH-isolated experiments (normal mode), which resulted in a stalled ${\mathrm{MnO}}_4^{-}$ electromigration front. The research also investigated potential stalling mechanisms, including voltage gradient nonlinearity through the central porous media core and the reduction of ${\mathrm{MnO}}_4^{-}$ to ${\mathrm{Mn}}^{2+}$. It was observed that the voltage gradient decreased as a result of ${\mathrm{MnO}}_4^{-}$ stalling; however, it was not considered a stalling mechanism. Results from ${\mathrm{Mn}}^{2+}$ analysis determined that the ${\mathrm{Mn}}^{2+}$ distribution for normal mode experiments extended partially beyond the extent of ${\mathrm{MnO}}_4^{-}$ electromigration; however, competing ions interfered with the analysis and definitive conclusions could not be made. pH-isolated experiments described in this research provide a simple method for implementing electrokinetic in situ chemical oxidation as a groundwater remediation technique where low permeability porous media exists.

Ozone/activated carbon coupling could be an efficient method to remove micropollutants, such as phthalates, that are refractory to classical treatments. However, this wastewater-treatment process can lead to the formation of oxidation by-products that may be toxic and which also need to be removed. The aim of this work was to study the evolution of the mineralization and the toxicity of the effluent during the treatment process so as to determine the efficiency of this method and the required time of treatment. Analyses [Fourier transformed infrared spectroscopy (FTIR), thermogravimetric analyses, ${\mathrm{N}}_2$ adsorption isotherms] of the adsorbent material were performed to understand the role of activated carbon during the treatment. It is shown that depending on the activated carbon properties and the experimental conditions, a fast and complete removal of diethylphthalate, and total mineralization and detoxification of the treated solution can be obtained. Moreover, it is demonstrated that the activated carbon acts more as a reaction site than as an adsorbent, leading to an in situ renewal of the material during the process.

Straining depicts the geometrical retention of fine particles within materials’ pore network. Whether or not fines can be retained depends on (1) the structure of materials’ pore network as well as (2) fines’ size distribution, manner of deposition, and retained amount. In this paper, the main results of straining tests are presented for randomly packed beads filters. The experimental program included a series of tests performed in both dry and water-saturated filters. The tests provided information on the dynamics of fines in the filters’ pore network and changes of filters’ efficiency. For instance, data supported the existence of four distinct stages: the filling of accessible cavities, the formation then clogging of the preferential pathways, the transfer of fines toward the lateral unobstructed capillaries, and eventual formation of a surface cake. The postulated mechanisms inherent to every single stage are discussed in terms of retention rate, straining length, lateral transfer, and progressive obstruction of constrictions. Additionally, the straining mechanisms were also probed in hydrodynamic conditions at increasing water flows.

A life cycle analysis (LCA) was performed for six commonly used types of water and wastewater pipe materials: polyvinyl chloride (PVC), ductile iron, cast iron, high density polyethylene (HDPE), concrete, and reinforced concrete. The objectives were to (1) compare the six pipe materials in terms of global warming potential (GWP) through four LCA phases: pipe production, transport, installation, and use; (2) determine the primary source(s) of differences in LCA results; and (3) examine the effectiveness of currently used pipe size selection criteria when LCA GWP is considered. The results for unit lengths of discrete pipe sizes were used to generate functions relating GWP per kilometer of pipe to diameter and material selections. The LCA results were monetized using an emission penalty of $\$25/\text{equivalent}$ ton of ${\mathrm{CO}}_2$. For pipe diameters $\le 61\mathrm{cm}(24\mathrm{in}\mathrm{.})$, GWP due to pipe manufacture, transport, and installation of ductile iron pipe was the largest among the six materials. At diameters $\ge 76\mathrm{cm}(30\mathrm{in}\mathrm{.})$, the GWP of PVC was highest. Concrete pipe resulted in the lowest GWP across the entire range of pipe sizes investigated. The GWP for pipe production, transport, and installation in a high-growth planning area in southeast Tucson, Arizona, was approximately one-tenth of the GWP derived from pipe network operation. The lifetime GWP from production, transport, and installation increased monotonically with pipe diameter for all materials analyzed, whereas, for a given flow, GWP from energy loss due to friction in flow simulations was inversely related to pipe diameter. The tradeoff suggests that there is an optimum diameter that minimizes lifetime GWP. However, optimum pipe sizes based on GWP were similar to pipe diameters selected based on economic cost alone, suggesting that LCA of water distribution and wastewater collection systems will not yield major changes in criteria for selection of pipe size.

Sodium hypochlorite (NaOCl) is a common cleaning agent for treating ultrafiltration (UF) membranes. Although it efficiently removes fouling, NaOCl accelerates membrane degradation and reduces membrane integrity. In this paper, new and polluted polyvinylchloride hollow fiber membranes were treated with NaOCl solutions. The effects on the membrane were evaluated by using transmembrane pressure, bovine serum albumin permeability, particle-size distribution of the effluent (PSDE), attenuated total reflectance-Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. The membrane pore size increased after exposure to solutions with a NaOCl mass fraction of $<1\%$. The membrane surface wrinkled after exposure to solutions with a NaOCl mass fraction of $>1\%$. The PSDE was successfully used to test membrane integrity. When the NaOCl mass fraction was $<1\%$, the PSDE increased; otherwise, the PSDE decreased. The main reason for pore-size enlargement was the breaking of C–C and C–H bonds, which caused C=C bond formation and chain scission. Polluted membranes were affected more than new membranes by NaOCl cleaning.

Excessive bacteria levels are a major water-quality problem in U.S. water bodies, and this study looked at the use of watershed-scale computer models to predict in-stream bacteria concentrations. The study site was the Little River Experimental Watershed (LREW) in Tifton, Georgia, and fecal coliform fate and transport models were built for four of the LREW subwatersheds over the period January 1996–December 2002. Three models were examined: HSPF, the soil and water assessment tool (SWAT), and the characteristic concentration (CC) model based on the principles of hydrograph separation. It was found that the most sensitive HSPF and SWAT water-quality parameters were associated with the in-stream bacteria processes, whereas parameters relating to terrestrial activity varied from sensitive to completely insensitive. Model performance was evaluated using the Nash–Sutcliffe statistic, and HSPF, SWAT, and the CC model performed comparably while showing distinct performance capabilities.

Understanding microorganism levels in urban runoff is essential for appropriate storm-water management, especially when storm-water is utilized by humans. An Escherichia coli monitoring program was conducted at four urban catchments in Melbourne, Australia. Simple and multiple correlation analyses were conducted that related climatic, rainfall, storm-water runoff, and other water-quality characteristics with the event mean concentrations (EMCs) of E. coli. Also, several existing and modified storm-water-quality models were tested against the measured storm-water E. coli levels to determine whether existing storm-water models could be used for prediction. The key findings are that source, growth, and removal of microorganisms are more important than wash-off and transport processes during wet weather since the most influential factors for E. coli EMC levels are (1) antecedent catchment conditions, such as vapor pressure prior to an event; (2) nutrient levels in storm water, such as ammonium, total phosphorus, and total nitrogen levels. However, rainfall intensity, which was found to be the most important transport-related variable (although less significant than the aforementioned build-up parameters), may also be considered in EMC prediction.

This is a first analysis of end-use energy intensity (EUEI) and greenhouse gas (GHG) emissions in water and wastewater (W/WW) sectors in India, and it examines their contribution to community-wide energy use and GHG emissions in cities in India. EUEI and related GHG emissions for W/WW infrastructures in Indian cities were analyzed and compared with data for cities in the United States. Data gathered by ICLEI-South Asia, Government of India, and the University of Colorado Denver were used to conduct this analysis. W/WW infrastructures were found to contribute 3–16% of community-wide electricity use and GHG emissions for 16 cities in India; for another 23 cities, the proportion was less than 3%. EUEI for drinking water supply and wastewater treatment averaged $0.3\pm 0.2\mathrm{W}·\mathrm{h}/\mathrm{L}(n=7)$ and $0.1\pm 0.05\mathrm{W}·\mathrm{h}/\mathrm{L}(n=5)$, respectively. EUEI for drinking water provision was more than double that for wastewater treatment, the reverse of typical cities in Colorado, likely a result of poorer source water quality in India. In general, although the sample size of Indian W/WW plants is small, EUEI in India appears to be much smaller than in the United States for both water and wastewater sectors based on this first review of quantitative data.

A literature review and 30-day leaching regime were conducted to determine the extent storm-water infrastructure coatings affect water quality. Newly installed polymer-enhanced cement mortar (PECM) and polyurea (PEUU) storm-water pipe coatings were removed from the field and underwent 10 three-day water immersion periods. For both materials, the greatest water quality alterations occurred during the first water contact period, followed by significant reductions in water quality alterations. Mineral release from PECM consistently elevated pH from 7.1 to 10.1–11.8 throughout the entire study. Organic contaminant release [total organic carbon (TOC) and ${\mathrm{UV}}_{254}$] was also detected for PECM during the first two water contact periods only. Alkalinity increased by $534\mathrm{mg}/\mathrm{L}$ as ${\mathrm{CaCO}}_3$ because of the first contact period and $18–50\mathrm{mg}/\mathrm{L}$ as ${\mathrm{CaCO}}_3$ for each remaining periods. Isocyanate resin from PEUU reacted with water and reduced water pH by 1.0 to 1.2 pH units during the early contact periods and lesser magnitude for the remaining exposure period. Chemical oxygen demand (COD), TOC, and ${\mathrm{UV}}_{254}$ results showed that organic contaminants were released from PEUU. A limited quantity of organic contaminants released by PEUU was biodegradable. Nitrogen compounds were detected only during the first PEUU water contact period.

Accelerated stormwater runoff creates environmental problems in many urban communities. Methods for reducing this runoff are available, but most do not work well if soils are poorly drained. Analysis of a rain barrel implementation strategy that diverts only roof runoff, for which there is a beneficial garden use, is presented and illustrated with a case study application. This approach reduces operation to the growing season and requires that the rain barrel function to benefit the garden and to reduce runoff, but may improve homeowner acceptance and operation. General methods for quantifying and bounding system effectiveness are illustrated. Case study results indicate that a 50-gal. (189-L) rain barrel connected to 25% of a $\mathrm{2,000}\text{-}{\mathrm{ft}}^2$ ($186\text{-}{\mathrm{m}}^2$) residential roof and serving a $150\text{-}{\mathrm{ft}}^2$ ($14\text{-}{\mathrm{m}}^2$) garden in Cleveland Heights, Ohio, would reduce the total roof growing-season runoff by 2.4–5.4% and the total annual roof runoff by 1.4–3.1%, depending on the irrigation strategy applied. Increasing garden and barrel size could increase the annual runoff reduction to 7.4%, but barrel capacity constrains additional reductions. These results illustrate the stormwater management limitations of rain barrels used in the case study location. The degree to which the analytical methods and results may be generalized to other communities is discussed.

Although constructed wetlands have become an accepted technology for the treatment of graywater for nonpotable reuse, little guidance is available on the design and sizing of wetlands specifically for graywater treatment. A common practice for sizing constructed wetlands is to apply the first order plug flow $k\text{-}{C}^{*}$ model. The objective of this work was to estimate $k$ and $C^{*}$ parameters in a free-water-surface wetland processing graywater during summer, fall, and winter months for five-day biochemical oxygen demand (${\mathrm{BOD}}_5$), total nitrogen (TN), and ammonia. Mass removal rates were consistently higher during summer months than winter months. Estimated values for $k$ were higher in summer than winter for ${\mathrm{BOD}}_5$ ($15.9\mathrm{m}{\mathrm{year}}^{-1}$ compared to $2.5\mathrm{m}{\mathrm{year}}^{-1}$) and TN ($16.4\mathrm{m}{\mathrm{year}}^{-1}$ compared to $5.5\mathrm{m}{\mathrm{year}}^{-1}$). Additionally, estimates of $k$ for ${\mathrm{BOD}}_5$ removal during all seasons was lower for graywater than typically observed for domestic and livestock wastewaters. The parameter ($k$ and $C^{*}$) estimates provided here can be applied to appropriately size free water surfaces intended for the treatment of graywater, and $k$ values should be modified based on the season of interest.