Journal of Environmental Engineering

Lagrangian actinometry represents a new method of photochemical reactor characterization. The method is based on an application of dyed microspheres, which were developed by attachment of $\left(E\right)$ -5-[2-(methoxycarbonyl)ethenyl]cytidine (hereafter referred to as $S$ ) to polystyrene microspheres. $S$ is a nonfluorescent molecule that when subjected to ultraviolet (UV) irradiation yields a single product, 3- $\beta$ -D-ribofuranosyl-2,7-dioxopyrido[2,3- $d$ ]pyrimidine (hereafter referred to as $P$ ), which displays a strong fluorescence signal. Dyed microspheres were subjected to UV irradiation under a collimated beam and using a single-lamp, monochromatic (low pressure Hg), continuous-flow reactor. In parallel with these experiments, a biodosimetry experiment was conducted using Bacillus subtilis spores as the challenge organism. Particle-specific fluorescence intensity measurements were conducted on samples from the collimated-beam experiments and the flow-through reactor experiments by flow cytometry. Estimates of the dose distribution delivered by the flow-through reactor for each operating condition were developed by deconvolution of data resulting from flow cytometry analysis of these samples. In conjunction with these experiments, a numerical model was developed to simulate the behavior of the reactor system. A commercially available computational fluid dynamics package was used to simulate the flow field, while line-source integration was used to simulate the irradiance field. A particle-tracking algorithm was employed to interrogate the flow and irradiance field simulations for purposes of developing particle-specific (Lagrangian) estimates of dose delivery. Dose distribution estimates from the microspheres assays and the numerical simulations were combined with the measured dose–response behavior of B. subtilis spores to yield estimates of spore inactivation in the flow-through experiments. For the range of operating conditions used in these experiments, predictions of spore inactivation based on dose distribution estimates from both methods were in good agreement with each other, and with the measured spore inactivation behavior. Lagrangian actinometry is capable of yielding accurate, detailed measurements of dose delivery by continuous-flow UV systems. This method represents a substantial improvement over existing experiment-based methods of UV reactor characterization (e.g., biodosimetry) in that it yields a measurement of the dose distribution for a given operating condition. This method also represents an improvement over existing methods for validation of numerical simulations. Specifically, because this method yields a measurement of the dose distribution, it is possible to compare these measurements with predicted dose distributions from the numerical simulation. The combined application of biodosimetry, numerical modeling, and Lagrangian actinometry represents an extremely robust approach to reactor characterization and validation.

In this paper, the oxidation of methyl tert-butyl ether (MTBE) in aqueous solution by an ozone/ultraviolet (UV) process was described. The oxidation process was investigated experimentally in a semibatch reactor under various operational conditions, i.e., ozone gas dosage, UV light intensity, and water quality in terms of varying bicarbonate concentration. The ozone/UV process was very successful in oxidizing MTBE. The rate of removal of MTBE increased when the incident UV light intensity increased for the same concentration of influent ozone gas. Similarly, an increase in influent ozone gas concentration resulted in faster removal of MTBE for the same incident UV light intensity. However, bicarbonate in the range of $2–8\mathrm{mM}$ showed no significant effect on MTBE removal for MTBE concentration $(\sim 1.0\mathrm{mM})$ used in this study. Moreover, it was observed that the reaction intermediates could react well in the ozone/UV process, and complete mineralization could be achieved by the ozone/UV process, if desired.

An approach that links a Monte-Carlo simulation based reliability program with the water treatment process behavior and performance model is presented for uncertainty analysis of the conventional water treatment plant (WTP) design. The expected mass concentration of suspended solids $\left(SS\right)$ in the effluent water is employed as a measurement of system reliability. The approach for uncertainty analysis of a WTP is illustrated with a hypothetical case study. The parameters contributing significantly to the variability of $SS$ concentration in the effluent water are identified. From an operational viewpoint, the variability in effluent water quality resulting from uncertainty in the system parameters is investigated. Also, improvement in the reliability of WTP using modified design parameters is investigated along with its cost implications. From the results, a method to calculate a set of safety factors corresponding to various performance reliability levels is proposed.

A procedure is presented for evaluating and comparing the biological activity of biofilms attached to various biofilm carriers by measurement of the glucose consumption rate. This technique allows for the economical design and selection of small particulate biofilm carriers that will maximize substrate removal when used in industrial-scale fluidized bioreactors. Methods for ensuring reproducible results are described. To support the glucose consumption rate findings, biofilm dry weights were obtained at the conclusion of activity rate experiments, and scanning electron micrographs were taken to evaluate the presence of biofilm and to view surface characteristics. Fourteen different biofilm carriers were evaluated ranging from commercially available products to novel carriers designed specifically for this study. Carriers that exhibited the highest reaction rates in descending order included: Syntrex 1220 (Kinetico, Inc.), Kaldnes Carrier Element—Modified (Kaldnes North America, Inc.), Kaldnes Carrier Element—Original (Kaldnes North America, Inc.), Macrolite Modified CEPP-02 (Kinetico, Inc.), Macrolite 357 (Kinetco, Inc.), and Virgin Foam Cubes (BB Bradley Co.). Results showed that the accumulation of biofilm depended most strongly on carrier surface properties, such as surface roughness and specific surface area. The biofilm activity as measured by glucose consumption rate correlated well with activity determinations made by COD measurements when a complex carbohydrate was used as substrate in place of glucose. Substrate consumption rates in microreactors were within $\pm 43\%$ of those measured in a 3-L bioreactor. The method presented here produced highly reproducible results and may be used to accurately and economically screen a large number of newly-designed carriers for application in industrial bioreactor processes.

Blast furnace (BF) slag is a by-product of steel plants. The objective of this study was to evaluate experimental methods to determine the phosphorus sorption capacity of BF slag. The handling of BF slag, before usage and clogging were also considered, as well as estimating the phosphorus retention capacity. Agitation and pilot-scale experiments were performed using both wastewater and phosphate solutions. This investigation showed that sorption capacities derived by wastewater experiments were considerably lower compared to those by phosphate solutions. Fresh BF slag briefly exposed to rainfall had a higher phosphorus sorption than weathered BF slag, indicating the importance of handling the slag carefully before usage. The risk for leakage of sulfuric compounds is considerable, especially during the initial operation phase of BF slag filters. Locations of BF slag filter beds for wastewater treatment must be carefully chosen from an environmental point of view.

In this paper, a model-based algorithm for optimizing the primary sludge fermentation process design and operation is described and evaluated. This is a recently used method to obtain the volatile fatty acid (VFA), needed for the enhanced biological phosphorus removal process, directly from raw wastewater. The proposed algorithm consists of a heuristic reasoning algorithm based on the expert knowledge of the process. Only effluent VFA and the sludge blanket height have to be set as design criteria, and the optimization algorithm obtains the minimum return sludge and waste sludge flow rates which fulfill those design criteria. It has been evaluated by simulating different temperature and sludge volume index (SVI) influent conditions in order to evaluate the algorithm performance under different conditions, as well as its sensitivity with respect to temperature and SVI, which are the most important parameters in these systems. The same tendencies observed by simulation were observed afterward in pilot plant experiments.

The objective of this study was to investigate the character and fate of bulk organics in reclaimed water used for groundwater recharge via soil-aquifer treatment (SAT). The study design followed a watershed guided approach considering hydraulically corresponding samples of drinking water sources, SAT-applied wastewater effluents, and subsequent post-SAT samples representing a series of different travel times in the subsurface. Water samples were fractionated into hydrophobic acids, transphilic acids, and hydrophilic carbon using a XAD resin-based protocol. Extensive characterization of organic carbon in the different samples was performed using state-of-the-art analytical techniques including excitation–emission matrix fluorescence spectroscopy, size exclusion chromatography, carbon-13 nuclear magnetic resonance spectroscopy $\left({}^{13}\mathrm{C}\text{-}\mathrm{NMR}\right)$ , Fourier transform infrared spectroscopy (FTIR), and elemental analysis. During SAT, transphilic and hydrophilic organic matter were preferentially removed. The results generally demonstrated that naturally derived (NOM) and effluent-derived organic matter after SAT overlap extensively in molecular weight distribution, amount and distribution of hydrophobic and hydrophilic carbon fractions, and chemical characteristics based on elemental analysis and ${}^{13}\mathrm{C}\text{-}\mathrm{NMR}$ and FTIR spectroscopy. However, the residual portion of the dissolved organic carbon contained both effluent-derived organic matter and NOM.

The effects of pH, alkalinity, and mass transfer efficiency on the removal of arsenite [As(III)] by zero-valent iron (ZVI) were evaluated in this study. The optimum pH range for removal of As(III) was found to be between 7 and 8. As(III) removal varied with salinity, pH, alkalinity conditions, and As(III) concentration. Degradation of As(III) removal performance was observed only under conditions of high alkalinity and arsenic concentrations [alkalinity $>10\mathrm{g}$ CaCO3/L and $2.9\mathrm{mg}∕\mathrm{L}$ As(III)]. A strong correlation between As(III) removal and increasing Reynolds number in batch testing suggests that mass transfer efficiency plays an important role in the removal of As(III) by ZVI. A diffusion-limited adsorption model was used to describe the removal of As(III) as the result of adsorption to precipitated iron oxides generated from ZVI corrosion. After an initial period of As(III) rapid adsorption to surface rusts formed during manufacturing and exposure to air, As(III) removal rate is most likely controlled by the rate of iron corrosion and the diffusion of As(III) to adsorption sites in ZVI/iron oxides.

The improvement in the effluent quality of the treated sanitary sewage entering the South Saskatchewan River at Saskatoon, Canada, and the impending change in provincial legislation governing urban runoff, provided the impetus for Saskatchewan Environment to initiate the stormwater runoff quality study reported in this paper. Among others, the study involved a field program for characterizing the urban runoff water quality from four catchments, each representing a different type of land use. Both a site mean concentration approach and a multiple variable regression analysis approach were used to quantify the pollutant load contained within the runoff. Thereafter, using the runoff water quality characterizations developed in the study, rainfall–runoff pollutant loads from the entire city were estimated and compared with two local point sources to the receiving stream. On the basis of this analysis, it was found that urban runoff contributes more total suspended solids and total Kjeldahl nitrogen load, similar chemical oxygen demand load, and slightly less total phosphorus load than the two local point sources.

The catalytic decomposition of acrylonitrile with catalysts was investigated in a bench scale fixed bed reactor in this study. Two catalysts, including $\mathrm{Pt}∕\gamma \text{-}{\mathrm{Al}}_2{\mathrm{O}}_3$ and ${\mathrm{Cr}}_2{\mathrm{O}}_3∕\alpha \text{-}{\mathrm{Al}}_2{\mathrm{O}}_3$ , were tested to study their catalytic activity in the complete oxidation of acrylonitrile. The results show that the $\mathrm{Pt}∕\gamma \text{-}{\mathrm{Al}}_2{\mathrm{O}}_3$ catalyst has better performance. The operating parameters such as operating temperature, acrylonitrile concentration, space velocity, and oxygen concentration were conducted in a series of experiments on the $\mathrm{Pt}∕\gamma \text{-}{\mathrm{Al}}_2{\mathrm{O}}_3$ catalyst. The results indicate that decomposition efficiency increases with temperature and oxygen concentration and decreases with the increases of space velocity and acrylonitrile concentration. With a regression model, the operating temperature is the most effective parameter on the decomposition of acrylonitrile. Carbon dioxide is the dominant product and carbon monoxide is an insignificant product of the decomposition of acrylonitrile. Material balance on carbon is good for the experiments. According to the BET and elemental analyzer analysis, major factors that cause the deactivation effect may result from nitrogen poisoning and carbon masking on the catalyst surface, especially at lower temperatures.

Contaminant transport in the unsaturated zone is important for managing water resources and assessing the damage due to contamination in the field of irrigation, water management, wastewater management, and urban and agricultural drainage systems. Deterministic modeling which is widely used for contaminant transport is not adequate because it considers model input parameters as well-defined crisp values and hence does not account for uncertainties and imprecision. This paper presents a contaminant transport model based on fuzzy set theory to simulate water flow and contaminant transport in the unsaturated soil zone under surface ponding condition. Among all soil hydraulic parameters that have uncertainty associated with them, saturated hydraulic conductivity was found to be the most sensitive to model outputs. Trapezoidal fuzzy numbers were used to express the uncertainties associated with saturated hydraulic conductivity. The incorporation of uncertainties into contaminant transport model is useful in decision making, as it yields scientifically and practically based estimates of contaminant concentration.

A three-dimensional numerical model was developed for simulating the phosphorus concentration in shallow lakes. In this model, the computational domain was divided into two parts: the water column and the bed sediment layer. The processes of mineralization, settling, adsorption, desorption, bed release (diffusion), growth, and death of phytoplankton were taken into account, and the concentration of organic phosphorus, phosphate, and related water quality constituents was simulated. The concentrations of adsorbed (particulate) and dissolved phosphate due to adsorption-desorption were calculated using two formulas derived based on the Langmuir equation. The release rate of phosphorus from the bed sediment layer was calculated by considering the effects of the concentration gradient across the water-sediment interface, pH, temperature, dissolved oxygen concentration, and flow conditions. The adsorption and desorption of phosphate from sediment particles, as well as its release from bed sediment, were verified using laboratory experimental data. The model was calibrated and applied to Deep Hollow Lake in the Mississippi alluvial plain. The simulated trends and magnitudes of phosphorus concentration were compared with field observations. The simulation results show that there are strong interactions between sediment-related processes and phosphorus concentration.

The river inflow in a natural lake with important suspended sediment load during floods, can impact water quality by mobilizing dissolved matters like phosphorous from deep to surface waters. Generally due to thermal stratification in prealpine lakes, the water column is stable. It does not mix vertically unless acted on by outside forces, for example, currents or winds. Since Lake Lugano has a strong thermal stratification, river inflow exhibits different modes of density currents, from surface flows and thermocline intrusion to bottom currents. Turbidity currents are the direct cause of the downward water flow, and at the same time at the origin of upward directed flow. In this study, the impact of river born turbidity currents in Lake Lugano under varying ambient conditions was investigated using field measurements at the inflow river and inside the lake, together with a full three-dimensional numerical model of the entire lake. The paper characterizes the induced circulation of the turbidity plume and gives some indications on the relevance of turbidity currents on the lake.

Experiments were carried out to gain insight into the effect of inherent factors on the radiolytic degradation of two biorefractory contaminants, Acid Orange 7 (AO7) and nitrobenzene (NB). The effects of irradiation dose rate $\left(D_r\right)$ , initial substrate concentration $\left(C_0\right)$ , pH, and temperature of solutions were evaluated in terms of degradation kinetics, degradation efficiency, initial $G$ values of substrate decomposition, and total organic carbon reduction. Higher $C_0$ and lower $D_r$ values were favorable for the efficient utilization of radiation energy, whereas higher $D_r$ and lower $C_0$ levels were beneficial for degradation rate. An increase in pH led to a reduction in degradation rate constant or degradation efficiency. The temperature of solutions had different effects on the radiolytic degradation of AO7 and NB. The degradation of AO7 followed the empirical Arrhenius law, whereas an increase in temperature led to a reduction in the degradation of NB.

Operators at waterworks in which flat-bottom floc blanket clarifiers are used, are advised to increase coagulant dose when the turbidity of clarified water is high, to stabilize the blanket and yield quality drinking water. This work showed that, even when the raw water is sufficiently alkaline, the blanket responded anomalously to the increased dose of polyaluminum chloride (PACl), which was used herein as a coagulant. Restated, rather than being stabilized, the blanket was destabilized by the high dose of PACl. This “anomalous” behavior of the blanket is caused by a temporary drop in local pH at the injection port at the bottom of the blanket, which is caused by poor PACl dispersion, and the subsequent charge reversal of the constituent particles and the decline in the blanket stability. A step increase in PACl dose may result in complete blanket loss.

Laboratory scale bioreactors were used to investigate sorption and biodegradation of $17\alpha$ -ethinylestradiol (EE2). EE2 is among many emerging micropollutants that may cause endocrine disruption of aquatic organisms in the environment. Results showed that the sludge taken from the membrane bioreactor (MBR) had a sorption distribution coefficient that was more than twice that of biomass derived from sequencing batch reactors (SBRs). The MBR biomass had smaller particles and was more hydrophobic than the SBR biomass. Experiments with nitrifying sludge showed that sorption was more important when the initial ammonia concentration was $48\mathrm{mg}∕\mathrm{L}$ or less, but at higher initial ammonia concentrations the role of biodegradation became more important. The ammonium monooxygenase enzyme extracted from a nitrifying mixed culture removed EE2 in batch experiments. These findings are the first that we are aware of to link biomass particle size, hydrophobicity, and sorption capacity. These results also support the notion that cometabolic biodegradation of EE2 can occur in nitrifying sludge.

The growing concern of the possible impact of natural disasters and extreme events on the environment has recently created new demands for information from, and assessment by, environmental engineers and climatologists. Mediterranean river basins encompass a diverse range of valley and floodplain environments and are affected by many different processes, such as hydroclimate, land-use, catchment geology, and relief. The objective of this paper is to develop a methodology for exploratory rainstorms data analysis and uncertainty estimation in regional hydrogeomorphological frequency analysis (HFA). A general framework is proposed for designing spatial variability of rainstorms with assigned return periods $\left(T\right)$ inducing multiple damaging hydrogeomorphological events in the Campania region, south Italy. To this end, the analysis of precipitation, involving means techniques of regional HFA and geostatistical theory integrated approaches, is a subject of great interest. However, the hydrogeomorphological consequences depend on complex interactions between extreme precipitation and torrential characteristics of the landscape. In Mediterranean environments, climatic fluctuations in hydrological regime, especially those exceeding rain thresholds for an acceptable range of flexibility, can be the main causes of relevant hydrogeomorphological impacts. An algorithm for the characterization of this impact termed with the acronym DRHI (Design Rainstorms Hazard Index) in this paper is presented first. Next, the continuous DRHI data are converted at each location using a binary variable indicator transform based on critical thresholds. In the third step, the expansion of DRHI-soft information from point to landscapes were assessed geostatistically using the records of 70 rain stations of the Department of Civil Protection established by Regional Monitoring Networks. In this way, threshold values for extreme hydrogeomorphological impacts were selected based on geographical distribution patterns of precipitation maxima with a duration of $3\mathrm{h}$ for a return period of 10, 20, and 50 years. Moreover, the map-based method provides the identification where future infill sampling should be focused in support of more precise characterization.

Anaerobic degradation of phenol mixed with a readily degradable synthetic wastewater (DSWW) as a cosubstrate was studied in a $12\mathrm{L}$ upflow anaerobic sludge blanket reactor at $30\pm 2°\mathrm{C}$ over a period of $632\text{days}$ . DSWW was prepared by diluting sugar cane based molasses. The biomass was acclimatized to high phenol concentration by gradually decreasing the DSWW chemical oxygen demand (COD) of $\mathrm{4,000}\mathrm{mg}∕\mathrm{L}$ . Feed made up of phenol COD and DSWW COD in the ratio of 7:3 (phenol $\text{concentration}=\mathrm{1,176}\mathrm{mg}∕\mathrm{L}$ ) was successfully treated at a hydraulic retention time (HRT) of $12\mathrm{h}$ and organic loading rate (OLR) of $8\mathrm{g}\mathrm{COD}∕\mathrm{L}\text{day}$ . Phenol removal ranged from 99.9 to 84% at phenol COD varying from 10 to 70% in the feed. During the entire operation, COD removal varied from about 74 to 91.3%. The influent COD was distributed into $\mathrm{C}{\mathrm{H}}_4–\mathrm{COD}$ $(\sim 72\%)$ , effluent COD $(\sim 17\%)$ , and sludge and unaccounted COD $(\sim 11\%)$ . The process failure occurred at 4:1 phenol COD: DSWW COD. Specific methanogenic activity of granular sludge exhibited uniform activity up to phenol COD of 70%. The performance of the reactor could not be maintained beyond 70% phenol COD even by reducing the sludge loading rate, increasing HRT, or decreasing OLR.