Journal of Environmental Engineering

Control and reduction of pollution from stormwater overflow is a major concern to be addressed by municipalities in order to improve the quality of the receiving water bodies and the environment in general. In the European context, these actions are driven by the Water Directive 2000/60/CE. In this regard, assessment studies of the potential load from sewer networks recognize the need for adaptation and upgrade of existing networks with waterworks and management measures. In many cases this is done by building first-flush detention tanks that, however, present consistent practical and economical burdens. In this work, simple rules to manage existing pumping stations in combined sewer systems are proposed as a way to apply management rules that mitigate pollution load. Such rules can be easily implemented in real cases with minimal cost of activation and no need of additional infrastructures. The procedure is based on the previous knowledge of the precipitation forcing and of a quantity/quality model of the sewer network. The steps adopted are (1) use of a (long-term, high-resolution) sequence of rainfall events to compute a wide spectrum of flow conditions (hydrographs and pollutographs) to the pumping stations; (2) definitions of a pumping rule to apply to the whole sequence of events to filter the incoming flow toward the wastewater treatment plant, so to compute outflows; and (3) efficiency assessment of the pumping rule by cumulative frequency analysis of water volume, pollutant mass, and pollutant mean concentration. Rule optimization can be performed by iterating points (2) and (3). An example is proposed to show how two simple parameters (a discharge threshold on the inflow and a maximum pumping time) can control the management of water and pollutant fluxes. Numerical results show that a proper optimization allows one to reduce the pumped volumes (thus reducing energy requirements and increasing the treatment plant efficiency) without significant changes to the overall pollutant mass outflow. The new pumping rules can be implemented on real stations with minimal and economically sustainable interventions.

Ethylenediaminetetraacetic acid (EDTA) as traditional chelating agent and nitrilo triacetic acid (NTA) as biodegradable chelating agent were used to evaluate the efficiency of leaching in silty-clay-loam soil contaminated with Pb, Cd, and Zn. Three concentrations of NTA and EDTA, 0.1, 0.01, and 0.005 M, were used in column leaching and each was set up in triplicate. Results demonstrate that the highest efficiency of heavy metals extraction was obtained in treatments with a concentration of 0.1 M EDTA and NTA. The extraction efficiency in first, second, and third pore volumes of 0.1 M EDTA were 41.92, 70.35, and 81.63% of Pb, 19.26, 44.28, and 77.58% of Cd, and 41.24, 56.14, and 65.8% of Zn, respectively. Also the extraction yields in first, second, and third pore volumes of 0.1 M NTA were 6.44, 14.72, and 16.78% of Pb, 47.68, 59.4, and 66.85% of Cd, an 11.44, 15.45, and 18.84 8% of Zn, respectively. Statistical analysis showed that EDTA concentration and pore volume have significant ($p<0.05$) effects on heavy metal leaching efficiency. At a washing solution pH of 4.5, the Pb, Cd, and Zn extraction efficiencies at the fifth pore volume were 87.25, 81.23, and 70.05% for the 0.1 M EDTA and 79.7, 59.8, and 60.12% for the 0.1 M NTA, respectively, when multiple heavy metals were used. The Pb, Cd, and Zn extraction efficiency for reuse of EDTA from leached solution were 99.12, 99.71, and 99.33%, respectively, for ${\mathrm{Na}}_2\mathrm{S}$ and 99.66, 99.74, and 98.59%, respectively, for ${\mathrm{Na}}_2\mathrm{S}/\mathrm{Ca}{(\mathrm{OH})}_2$ treatment. The acidity of the environment has a significant impact on heavy metals removal for both chelating agents. The overall orders of metal extraction efficiency for EDTA and NTA that resulted from this study are $\mathrm{Pb}>\mathrm{Cd}>\mathrm{Zn}$ and $\mathrm{Cd}>\mathrm{Zn}>\mathrm{Pb}$, respectively.

Stormwater ponds provide cost and space-efficient treatment of urban runoff via gravitational settling. The goal of this paper was to quantify different mechanisms by which wind can affect the particle removal efficiency of a shallow retention pond. An analytical bulk model was developed and validated numerically against total suspended solids (TSS) measurements in a small (0.3 ha), optimally designed oval pond during four runoff events with $7–11\mathrm{m}/\mathrm{s}$ winds. Simulations highlighted wind as an effective mixing mechanism, lowering the removal of medium silt particles by 10–20% from ideal plug flow, and severely constraining the removal of small clay and silt particles ($<6\mathrm{\mu m}$). Initial background concentrations of $<12\mathrm{mg}/\mathrm{L}$ TSS were positively correlated with wind speed 5 h prior to the event, indicative of localized wind resuspension. A widespread remobilization of bed sediments was found unlikely in a 1.7-m deep, 112-m fetch pond. A stirred reactor with 60% effective volume is proposed as a first order tool to assess the treatment performance of ideally structured ponds in areas with strong, unobstructed winds.

Chlorinated ethene (CE) concentration profiles in 184 injection area wells at 37 enhanced reductive dechlorination (ERD) sites were evaluated to assess the overall behavior of individual CE compounds and estimate in situ removal rates. ERD is effective at reducing parent compound concentrations, with a median extent of removal of 88% (PCE) and 91% (TCE). However, concentrations of cis-DCE and vinyl chloride (VC) increased at many sites. Given these conflicting trends, it can be difficult to assess the overall performance of ERD. Total organic chlorine ($\mathrm{\Sigma }\mathrm{Cl}$) is proposed as a more comprehensive and robust metric to describe ERD performance. $\mathrm{\Sigma }\mathrm{Cl}$ concentrations declined in over 85% of wells. The median decline in $\mathrm{\Sigma }\mathrm{Cl}$ was 67%, with one-quarter of the wells achieving $\mathrm{\Sigma }\mathrm{Cl}$ removal greater than 99%. In approximately half of all wells with a statistically significant downward trend, $\mathrm{\Sigma }\mathrm{Cl}$ removal rates slowed a few years after substrate injection. The reason for the rate decline is not known, but it does not appear to be correlated to pH, total organic carbon (TOC) levels, or $\mathrm{\Sigma }\mathrm{Cl}$ concentration. As concentrations decline, removal rates may slow and approach the rate at which contaminants are released from poorly treated areas (e.g., low permeability zones and upgradient contaminated areas). In the 30 wells with sufficient postdegradation phase data, $\mathrm{\Sigma }\mathrm{Cl}$ concentrations began to rebound in 13% of wells and remained stable, had no identifiable trend, or continued to decline at a slower rate in 87% of wells.

Nitrous oxide (${\mathrm{N}}_2\mathrm{O}$) is a potent greenhouse gas. Wastewater treatment is considered to be a minor source of ${\mathrm{N}}_2\mathrm{O}$; however, observed in-plant emission factors are more variable than previously considered. Further, emissions associated with treated wastewater effluent are highly uncertain. A model incorporating these uncertainties was compared with current ${\mathrm{N}}_2\mathrm{O}$ estimates. The modified model features distribution-based emission factors and Monte Carlo simulation. Results of these simulations indicate ${\mathrm{N}}_2\mathrm{O}$ emissions 7.3, 8.6, and 9.4 times estimates generated with the current method for in-plant, effluent-derived, and total emissions, respectively. Future changes in biological nitrogen removal (BNR) associated with clean water objectives may alter ${\mathrm{N}}_2\mathrm{O}$ releases. The model, which distinguishes between BNR and non-BNR treatment, predicts decreasing ${\mathrm{N}}_2\mathrm{O}$ emissions with increasing BNR treatment. Examining the Chesapeake Bay system, the model suggests 2012 BNR levels reduced ${\mathrm{N}}_2\mathrm{O}$ emissions by 0.86 MMT ${\mathrm{CO}}_2$ eq per year, and planned BNR expansions will result in emissions being reduced by 1.77 MMT ${\mathrm{CO}}_2$ eq relative to 0% BNR scenarios. The new estimation method would be improved through additional collection of data on effluent emissions.

Manganese mud (MnM) is a manganese oxide petal-like nanostructured precipitate that accumulates on the inner surface of pipes transferring reclaimed effluent from the Shafdan soil aquifer treatment system to irrigation fields in southern Israel. It was found that ${\mathrm{Mn}}^{2+}$ adsorbs on the MnM sediment, and under aerobic conditions, rapid Mn(II) oxidation takes place. The MnM exhibited superior Mn(II) adsorption capacity compared to other commercially available manganese oxide catalysts. A filter loaded with anthracite-supported MnM was developed and used as a highly efficient, reagentless catalyst for the continuous oxidative removal of dissolved Mn. A $10–13{\mathrm{m}}^3·{\mathrm{h}}^{-1}$ pilot plant was constructed for Mn removal from Mn-rich effluent by atmospheric oxygen oxidation. The system operated continuously for more than two years with minimal maintenance, without oxidative regeneration. No ripening period was required, and the fixed bed exhibits exceptionally high catalytic efficiency. The proposed filter is superior to synthetic supported manganese oxide reactors because it does not require periodic regeneration by strong oxidizers; it is superior to filtration units for manganese removal because it does not require ripening time. A possible explanation for the superior catalytic activity based on the delicate, two-dimensional structure of MnM is presented.

This paper presents the results of oxygen transfer properties of a free, wall-supported, and plate-supported plunging rectangular jet. Consistently, the free jet had the highest values of oxygen transfer coefficient, $K_L{a}_{20}$; wall-supported and plate-supported jets were typically 0.93 and 0.74 times that of the free jet, respectively. At constant jet height $h_j$ and jet velocity $v_j$, $K_L{a}_{20}$ decreases as the water depth in the pool increases for all types of jets. This is attributed to a decrease in the air/water interface, also known as the contact area, as volume increases. An optimum water depth, $h_w^{\prime }$, can be inferred for all three supports below which $K_L{a}_{20}$ decreases due to the bubble plume impinging on the bottom of the pool. For varying $h_j$ and $v_j$, $K_L{a}_{20}$ increases with the former while a power relationship is observed between $K_L{a}_{20}$ and the latter for all supported jets. Ultimately, for each type of support an empirical equation based on the properties of the jet and the pool is proposed.

In this study, a surrogate of Cryptosporidium parvum oocysts was prepared using Cryptosporidium-sized carboxylated polystyrene microspheres and an alpha-1-acid glycoprotein (AGP). The zeta potential of the modified surrogates was found to be similar to that of viable Cryptosporidium parvum. These surrogates were used in laboratory-scale filtration experiments under the effects of flow velocity, alum addition, and humic acid (HA) coating on quartz sand surfaces. Filtration results showed that increased flow rates enhanced the transport of microspheres mostly as a result of increased hydrodynamic force. HA adsorbed on the grain surfaces greatly enhanced the mobility of microspheres in the packed bed, possibly as a result of increased repulsion between microspheres and the media. Alum inhibited the transport of microspheres in the column mostly as a result of the charge neutralization of the microspheres. The transport of microspheres when alum and HA coexisted was almost the same as the condition when alum and HA were absent. Deposition profiles showed a monotonic decline with distance under conditions where no HA was present, while nonmonotonic depositions were observed under conditions where HA was adsorbed on collector surfaces.

A kinetic model based on the Michaelis-Menten kinetic equations for simulating the complex reductive biodegradation kinetics of groundwater contaminants was developed that incorporates multiple levels of branching via the formation of multiple daughter products from a parent compound and/or a daughter product from multiple parent compounds. The model was tested using experimental data from two published laboratory studies involving the biodegradation of 2,4,6-trinitrotoluene (TNT) in the presence and absence of sorption. In each case, reasonable correlation was observed between the model-calculated and experimentally observed concentrations of TNT and its biodegradation products and the total mole balance with time. Model calibration–determined maximum specific rates of biodegradation were found to decrease with increasing substitution of nitro groups by amino groups from TNT to 2,4,6-triaminotoluene via aminodinitrotoluenes (ADNTs) and diaminonitrotoluenes (DANTs). Biodegradation of DANTs was also found to be strongly inhibited by the presence of parent intermediates ADNTs. The maximum specific rates of biodegradation for TNT and products were found to decrease in the presence of sorption.

Occasional dissolved-air supersaturation—such as may occur, for instance, downstream of dams—is harmful to fish because it causes gas bubble disease. A counterintuitive but effective means of reducing dissolved air content is the injection of bubbles in the supersaturated water. The bubbles greatly increase the air–water surface area available for the exsolution of the dissolved air, bring the interface into direct contact with the supersaturated water, and mix the water with their ascensional motion. This paper is a computational study of the process. The results suggest that the method has great potential and may be effective in applications.

At least 90% of the research on bioremediation has been based on the use of materials in cometabolism and/or as electron donors. The main purpose of this study was to evaluate biodegradation rates of explosives in soil in terms of economics and feasibility. Two lab-scale bioreactors were operated in this study, and results showed biodegradation rates of 2,4,6-trinitrotoluene (TNT) and pentaerythritol tetranitrate (PETN) at 84 and 67% after 60 days compared with rates of 46 and 29% without the monorhamnolipid contribution. Chemical oxygen demand (COD) was monitored during bioremediation and showed that reduction in COD concentration was directly proportional to desorption of intermediates from the soil matrix and their degradation, along with degradation of the parent compounds. Results also showed that the anaerobic condition for nitroaromatic bioreduction as the sole source of nitrogen was time consuming. The monorhamnolipid overcomes this challenge via enhanced biodegradation efficiency of nitroaromatics. Furthermore, application of the monorhamnolipid as in situ explosive bioremediation is feasible, suitable, environmentally friendly, and economical, especially in hot and wet areas with extensive contamination.