Journal of Environmental Engineering

Mathematical models are significant tools for urban runoff management. A rational account of sediment-limited and energy-limited situations in developing a mathematical model may facilitate the improved simulation of total suspended solid (TSS) wash-off in urban impervious surfaces. In this study, a differential equation called the P/r model is proposed to improve the simulation of the sediment discharge process. In this equation, rainfall intensity and the ratio of sediment mass per unit catchment area to rainfall intensity are considered the main variables. The rationality behind the P/r model is analyzed. TSS wash-off from six rainfall events is investigated using the P/r model. Uncertainty analyses are performed to determine the best-fit parameters for the model, with the maximum Nash–Sutcliffe efficiency (NSE) criterion being 0.53 and the minimum normalized objective function being 0.40. The observation percentage within prediction bands is 75%, and the average relative interval length is 1.07 when the NSE is 0.50. Results show that the proposed mathematical model can fit well with the TSS data observed in the case study.

Falling water in dropshafts can induce large amounts of air into the airspace of sewers, and the subsequent release of the pressurized air can cause sewer odor concerns. The construction of a vertical airshaft that is connected to a dropshaft via pipes is expected to circulate the air and reduce air induction into sewers. In this study, two deep dropshafts with drop heights of 24 and 11 m were retrofitted sequentially with air circulation pipes in a sanitary sewer system. Air pressure inside the sewer line and air flow rates inside the air circulation pipes were monitored in 2006–2011. The results show that the retrofits reduced the manhole air pressure by about 10–47%. Air pressures in the manholes and the dropshafts, as well as air flow rates in the air circulation pipes, were noticed to have diurnal patterns, which appeared to relate to wastewater discharge and air pipe elevation. Overall, the ratios of air flow rate to water flow rate were found to be $160\pm 78$ and $144\pm 113$ for the two dropshafts, which are several times larger than those reported for laboratory dropshafts without air circulation pipes. Sewer air was indeed circulated via air pipes in the first dropshaft, while no circulation was observed most of time in the second dropshaft because the air was directly pushed downstream by the upstream dropshaft.

Soil can naturally attenuate contamination, depending on its interaction with contaminants. Soils can delay the spread of the contaminant plume and even reduce the bioavailability of the contaminant because of their contaminant retention capacity. The retention capacity may be influenced by several physicochemical factors of both the soil and the contaminant. The aim of this study was to assess the retention capacity of a clayey, basaltic residual soil to an organic contaminant (soybean biodiesel) under different variable conditions, such as moisture content, void ratio, and presence or absence of biostimulation nutrients, specifically nitrogen (N), phosphorus (P), and potassium (K). Experiments were conducted using 100-g samples of dry soil under different void ratios (1.14, 1.24, and 1.34) and different moisture contents (15, 25, and 35%). Two series of experiments were conducted: one in the absence of nutrients and another in the presence of nutrients. The soil samples were initially sterilized, and they were spiked with biodiesel at a concentration of $40\mathrm{g}/\mathrm{kg}$ of dry soil (4%) and homogenized. The extent of retention of the contaminant in the soil was assessed immediately and after 15 and 30 days of contamination. Residual contaminant content in the soil was determined based on the difference between the initial contaminant mass and the extracted contaminant mass using ultrasound technique. Results showed that the moisture content had a profound impact on contaminant retention—as the moisture content increased, contaminant retention decreased. The presence of nutrients also reduced the retention capacity of the soil under all tested conditions in this study. Generally, the amount of residual contaminant in the soil increased with the contact time. Overall, biostimulation nutrients and high moisture content reduced the contaminant retention, creating conditions favorable for contaminant migration, which increase environmental risk associated with the contamination.

Dissolved organic phosphorus (DOP) has been found to be a significant fraction of the urban runoff phosphorus load. To achieve enhanced DOP removal, bioretention soil media (BSM) amended with an aluminum-based water treatment residual (WTR) and montmorillonite (both 10% by mass) were additionally treated with aluminum sulfate (10% by mass) to improve sorption capacities. The sorption of myo-Inositol hexakisphosphate (IHP) and adenosine monophosphate (AMP), two forms of organic phosphorus, by modified BSM were studied using batch experiments. The sorption of AMP was increased by a factor of 17 and 21 for WTR- and montmorillonite-amended BSM with 10% alum, respectively. Similarly, the IHP removal capacity of these two modified media mixtures were increased by factors of 4 and 5, respectively. Scanning electron microscopy (SEM) and Brunauer, Emmett, and Teller (BET) surface area analyses were used to provide support for underlying sorption mechanisms for the enhanced DOP removal. The oxalate ratio (OR) was employed to provide an index for DOP sorption onto BSM. Generally, greater DOP sorption was observed with higher oxalate ratios.

This paper describes findings from the City of St. Louis Low Impact Development Green Alley Pilot Study to reduce water quantity in the combined sewer system. Permeable pavement is one green infrastructure technique used for water quantity reduction. The effectiveness of permeable pavement in reducing the stormwater runoff to the combined sewer was tested. Monitored flow from reconstruction and postconstruction of permeable pavement are used for analysis. The separation of base flow and runoff is based on estimating the base flow in the antecedent/subsequent dry days of the rainfall events. The comparison between runoff in the reconstruction and postconstruction of the permeable pavement from three alleys showed different percentages of runoff reduction from different types of pavement (36, 13, and 46% from permeable concrete, permeable asphalt, and permeable pavers respectively). Permeable asphalt had the lowest percentage reduction, most likely due to the slope of the site and the small ratio of permeable to catchment area in this location. The permeable paver showed the highest percentage of runoff reduction.

The oxidation of dyes by alkaline-activated peroxymonosulfate (PMS) was investigated for the first time and the dominant oxidizing species in the process were identified. Various dyes [methylene blue (MB), orange G, and direct blue 53] were almost completely removed ($>98.5\%$) by PMS under slightly alkaline conditions ($\mathrm{pH}=7.7$), although there were little or low oxidation efficiencies of dyes by PMS only. Sulfate radicals were proved to be the dominant oxidizing species responsible for rapid and effective dye removal in the alkaline-activated PMS system according to radical scavenger experiments. The dye degradation processes followed a pseudo-first-order kinetic model with high correlation coefficients ($r>0.9538$). The oxidation rate constants of MB under slightly alkaline conditions increased by approximately 10 times compared with that under acidic or neutral conditions. Increasing the oxidant concentration enhanced the generation of radicals and increased MB removal efficiencies. The mineralization and degradation of MB were further proved by monitoring ultraviolet-visible absorbance spectra and total organic carbon contents of the reaction solution. This alkaline-activated PMS oxidation system would be a good candidate technique for the remediation of wastewater since it leads to less energy consumption and secondary pollution of catalysts compared to other PMS activation methods.

Scale-up of a lead dioxide (${\mathrm{PbO}}_2$) anode system is significant to the practical application of electrochemical oxidation (EO) in biorefractory wastewater treatment. In this study, response surface methodology (RSM) was employed to investigate the effects of different operating conditions on phenol removal by electro-oxidation with a $\mathrm{Ti}/{\mathrm{PbO}}_2$ anode. A central composite design (CCD) was used to optimize the electro-oxidation process and to evaluate the individual and interactions effects of current intensity, electrolysis time, and recirculation flow rate on phenol removal. Synthetic wastewater (or distillate water) with phenol concentration of $10\mathrm{mg}/{\mathrm{L}}^{-1}$ was used in this study. Optimal conditions for phenol removal were established at 1.12 A current intensity, 40 min electrolysis time, and $188\mathrm{mL}·{\min }^{-1}$ recirculation flow rate, in which a removal of $78.97\pm 1.72\%$ was achieved. The decay kinetics of phenol removal was fitted a first-order reaction.

Urban wet-retention pond performance has been extensively studied for many water contaminants. However, very few studies have focused on wet-retention pond efficiency under agricultural production systems. This study presents the results drawn from a 5-year data set collected on a retention pond constructed in Saint-Samuel (Canada) at the outlet of a 23.1-hectare watershed under cash crop production. A total of 62 runoff events were analyzed for hydrological performance, 20 events for total suspended solids (TSS), 11 events for total nitrogen (TN), and 14 events for total phosphorus (TP). Peak flows were reduced by 38% on average and the retention pond reduced the frequency and duration of exceedance of the erosion threshold. Drawdown times for 50, 75, 90, and 100% of the runoff volume were 7, 18, 28, and 42 h, respectively. The mean detention time was 3.2 h compared to the watershed lag time of 3.4 h. Mean removal efficiency ratios based on event-mean concentrations (EMC) and event-total loads (ETL) were similar to those reported for urban areas, with values of 50–56%, 42–52%, and 48–59% for TSS, TN, and TP, respectively. Effluent water quality analyses have shown that environmental criteria were often exceeded and threshold concentrations below which treatment is unlikely to occur were similar to irreducible concentrations reported for urban areas with estimated values of 30, 1, and $0.2\mathrm{mg}/\mathrm{L}$ for TSS, TN, and TP, respectively. The primary treatment mechanism of the retention pond is most likely the sedimentation of sand and silt particles and particulate nutrients.

The heterogeneous Fenton oxidation reaction was investigated at two different catalytic supports including the blank alumina plates and alumina plates with thin carbon nanofiber (CNF) layer. Iron (III) oxide was used as a catalyst and propionic acid (PA) was studied as a model organic compound. A carbon nanofiber layer and a thin catalytic layer of iron (III) oxide were prepared using the chemical vapor deposition method with acetylene and ferrocene precursors. The reaction rate of heterogeneous Fenton oxidation was compared with the rate of homogeneous reaction. Obtained results indicate that the reaction rate is significantly higher at homogeneous Fenton oxidation at high temperature (70°C), however, the reaction rate for homogeneous and heterogeneous oxidation is comparable at room temperature (25°C) if carbon nanofiber support is used for the iron (III) oxide catalyst.

Surfactant amendment has been proposed as a means to stabilize or mobilize groundwater contamination by modifying the soil’s natural sorption characteristics in situ. The importance of the native soil’s characteristics with regard to contaminant sorption and the effect of surfactant amendment were evaluated using three varied soil samples and naphthalene as a model contaminant. As expected, soils with high cationic exchange capacity and organic matter content tend to have the greatest ability to sorb naphthalene and the surfactant cetylpyridinium chloride. Micelle formation was noted in the presence of weakly sorbing natural soil, though not in the more reactive soil samples. Surfactant amendment significantly increased naphthalene sorption capacity for sterilized, nonreactive sand, increasing the partitioning coefficient, $K_d$, by 50%, and decreasing sorption among soils with high natural sorption capacity, partitioning naphthalene back into the aqueous phase.

Foaming is a major concern for wastewater treatment plant operators attributable to its significant impacts on process efficiency and operational costs. Several causes and remedial measure have been suggested over the past few years by researchers. However, the supporting experimental information is inadequate to implement these measures. This technical report aims to provide the results obtained from the foaming events which occurred during the operation of the sludge-bed anaerobic membrane bioreactor (SB-AnMBR). The report explores the cause and remedial measures to prevent the foaming in AnMBRs.