Journal of Environmental Engineering

This paper presents the sensitivity and uncertainty analysis of a mathematical model for greenhouse gas emission (GHG) and energy consumption assessment in wastewater treatment plants. A sensitivity analysis was carried out (using two different methods) to determine which model factors have the greatest effect on the predicted values of the GHG production. Further, an uncertainty analysis was carried out to quantify the uncertainty of the key model outputs, such as carbon dioxide production from activated sludge treatment. The results show that influent fractionation factors, which characterize influent composition, have an important role on direct and indirect GHGs production and emission. Moreover, model factors related to the aerobic biomass growth show a relevant influence on GHGs in terms of emission from off-site power generation ($m_{\mathrm{CO}2\mathrm{eq},\mathrm{PG}}$). Further, model factors related to the autotrophic biomass growth were found to strongly interact with other factors especially in modeling $m_{\mathrm{CO}2\mathrm{eq},\mathrm{PG}}$. Finally, nitrous oxide (${\mathrm{N}}_2\mathrm{O}$) emission associated with the effluent has the highest uncertainty, suggesting the need for a mechanistic model for ${\mathrm{N}}_2\mathrm{O}$ production in biological treatment.

The efficiency of soil vapor extraction (SVE) depends primarily on mass transfer parameters. The objective of this work was to determine whether mass transfer parameters obtained from calibrating a model against unidirectional column experiments could be used for three-dimensional (3D) applications. A 3D experimental setup was designed and constructed to simulate a decontamination system at the bench scale. A mathematical model simulating multiphase flow and multicomponent transport of contaminants in the subsurface under nonequilibrium transient mass transfer conditions was developed and used. Results showed that the mass transfer parameters obtained from unidirectional column assays were several orders of magnitude greater than those obtained with the 3D trials. Quantitative analyses of the experimental data showed that mass transfer limitations occurred in 3D. Mass transfer coefficients are related to the distribution of air velocity in the 3D reactor. Consequently, unlike the 1D column, mass transfer coefficients may not be linked to a single value of air velocity.

Hydraulic parameters play an important role in mass transfer phenomena in photocatalytic reactors. These fundamental hydraulic parameters are flow rate, relative roughness, and Reynolds number. This research experimentally evaluates the effects of flow rate and artificial relative roughness in order to determine the factors influencing the removal efficiency and reaction rate constant of Reactive Yellow 81 (RY81). For this purpose, a cascade photocatalytic reactor is constructed which consists of similar polymethylmethacrylate plates coated by ZnO nanoparticles and with various types of roughness. Dye removal efficiency is calculated for different flow rates with and without considering relative roughness. Furthermore, this study also reveals main effective parameters increasing the mass transfer rate, and uses a decision tree model called M5-Pruned (M5P) for predicting dye removal efficiency. Therefore, simple relations are provided for calculation of dye removal efficiency that consider important parameters including flow rate, run-time, roughness height, and initial pollution concentration.

Constructed wetlands (CWs) are increasingly being applied for wastewater treatment and as pretreatment before artificial recharge of the effluents. Three horizontal subsurface-flow CWs were operated in parallel for almost 7 months and fed with three types of treated effluents to analyze enhancement of water quality at an average hydraulic retention time (HRT) of 1.3 days. The wastewater effluents analyzed in this study were an on-site anaerobically pretreated sewage at an Al-Mazra’a house, tertiary effluent at Al-Bireh City, and secondary effluent at the Birzeit University campus in Palestine. The average dissolved organic carbon (DOC) removal of 48, 50, and 47%, chemical oxygen demand (COD) removal of 55, 45, and 50%, biochemical oxygen demand (BOD) removal of 57, 38, and 60%, ammonia-nitrogen (${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$) removal of 96, 90, and 97%, nitrate-nitrogen (${\mathrm{NO}}_3^{-}\text{-}\mathrm{N}$) removal of 88, 94, and 93%, total nitrogen (TN) removal of 72, 70, and 71%, phosphate (${\mathrm{PO}}_4^{3-}$) removal of 63, 61, and 57%, total suspended solids (TSS) removal of 37, 41, and 42%, and fecal coliform (FC) removal of 90, 85, and 95% were achieved with the CWs of the Al-Mazra’a, Al-Bireh and Birzeit effluents, respectively. The dissolved solids in the effluent of the three investigated CWs were increased. The total dissolved solids (TDS) and electrical conductivity (EC) of the (influent; effluent) of Al-Mazra’a, Albireh, and Birzeit were (337, $366\mathrm{mg}/\mathrm{L}$; 680, $737\mathrm{\mu s}/\mathrm{cm}$), (327, $351\mathrm{mg}/\mathrm{L}$; 658, $695\mathrm{\mu s}/\mathrm{cm}$), and (299, $326\mathrm{mg}/\mathrm{L}$; 603, $653\mathrm{\mu s}/\mathrm{cm}$), respectively. The CW was efficient in terms of ${\mathrm{NH}}_4^{+}$, ${\mathrm{NO}}_3^{-}$, and BOD removal, and achieved the Palestinian standards for treated effluent reuse and discharge to wadis for recharge, despite the high evapotranspiration of approximately 24%. The maximum achieved specific removal rates of phosphorous (P), nitrogen (N), and BOD were 2,211, 15,329, and $\mathrm{5,980}\mathrm{k}\mathrm{g}/\mathrm{ha}/\mathrm{year}$, respectively. The study clearly showed that CWs have a high potential for further polishing treated effluents in both urban and rural arid areas of Palestine, such as Al-Bireh and Ramallah Cities and the adjacent villages, while achieving the double goal of environmental protection and environmental restoration.

In the last decade, many Activated Sludge Model No. 3 (ASM3) extensions were proposed to adopt new concepts such as simultaneous storage and growth of heterotrophic organisms and two-step nitrification-denitrification processes. From these ASM3 model extensions, four are included in this study: ASM3 with two-step nitrification-denitrification, ASM3 for simultaneous autotrophic and heterotrophic storage-growth, ASM3 extension for two-step nitrification-denitrification, and ASM3 for simultaneous storage-growth and nitrification-denitrification. The four models are analyzed and compared to the original ASM3 model with respect to the modeling concepts adopted, the process kinetic rates modified, and the kinetic parameters and stoichiometric coefficients introduced. A new schematic representation of the modeling concepts concerning the organisms’ activities is introduced. A database of all parameters and coefficients of the four considered model extensions is developed using a unified notation system to reduce effort and confusion of the future researchers using their values as initial calibration or guidance values. Finally, the four models and the original ASM3 model are implemented using the parameters’ values from the developed database, then the simulation results are compared with actual field measurements.

This paper describes the design and development of an operational diagram that was developed based on the solids flux theory and connects the process operational parameters, namely, mixed-liquor suspended solids, flow, volume, area, and recycle ratio in an unified graphical form to facilitate the design and operation of secondary clarifiers for an Indian pulp and paper industry. A control strategy was developed based on steady-state control methods by utilizing the batch settling data generated in stationary phase complimented with artificial neural network models. These diagrams evaluate the operating strategies in response to changes in flow rate or settleability of solids. These operational diagrams developed based on steady-state control analysis, can be used for controlling the performance of the activated sludge process subjected to long term variations in the influent flowrate and substrate concentration. The plant operator can make a rational decision on his own to control the process using the operation diagrams.

Many older water reclamation plants (WRPs) are implementing model-based process control to satisfy increasingly stringent effluent requirements while they lower energy costs, but these methods require reliable process information. Soft sensors can help to provide such information by building on easily acquirable and historical data. In this investigation of a soft-sensor approach at a conventional WRP, many historical data were missing, which suggested that a large fraction of the information would be lost if the missing data were not well managed. This study applied an iterated stepwise multiple linear regression (ISMLR) approach to minimize the loss of data and to predict real-time influent ammonia and ${\mathrm{CBOD}}_5$ (5-day carbonaceous biochemical oxygen demand), and future influent flow at the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) Calumet WRP. Relative to a simple deletion method (which retained about 45% of the daily data), the ISMLR approach successfully retained substantially more information (65–82% of the days) and provided good predictions on real-time ammonia concentrations ($r\approx 0.92$) and future influent flow ($\approx 0.91$). Two additional tests, uncertainty analysis and random missing data, were also conducted, which demonstrated the high reliability and flexibility of the ISMLR approach.

The nonideal segregated flow (SF) model was adapted for modeling single-sludge carbonaceous biochemical oxygen demand (cBOD) reduction and nitrification within a plug-flow-like bioreactor. Principles associated with the CMFRs (complete-mix flow reactors) in series (also called continuous-flow stirred tank reactors, CFSTRs, in series, or simply tanks in series, TiS) and plug-flow with dispersion (PFD) models were combined with the SF model to develop a powerful modeling approach with the capability to predict reactant and product concentrations and process rates as a function of position along the reactor flow path. The single CMFR, plug-flow (PF), TiS, and SF models were then used to simulate the steady-state performance of a hypothetical activated sludge bioreactor to compare capabilities to predict spatial process variation. All simulations were forced to a common target effluent ammonia-nitrogen concentration, yielding unique sets of predicted performance parameters from each of the models. Predictions of positional oxygen consumption rates were generated and compared to discern model applicability. The SF model was shown to be quite adaptable to modeling of spatially variant processes in plug-flow-like reactors with predictions highly sensitive to the magnitude of the dispersion coefficient employed to characterize reactor hydrodynamics. Key limitations of the currently developed modeling approach include (1) to-date development is for steady state conditions, (2) the bioreactor is decoupled from sedimentation operations, and (3) the model is not yet calibrated against actual lab-scale or full-scale reactor systems.

This paper examined and compared the hydraulic and environmental performance of permeable interlocking pavers (PICPs), porous asphalt (PA), and porous concrete (PC) under cold climate conditions in Calgary, Alberta, Canada. Assessments were made of their hydraulic performance in terms of storm runoff reduction and surface infiltration capacity, and environmental performance in terms of the removal of several pollutants including total suspended solids (TSS), total nitrogen (TN), total phosphorous (TP) and, heavy metals: copper (Cu), lead (Pb), and zinc (Zn). Results from this paper demonstrated that PA, PC, and PICPs are all effective in mitigating storm runoff under cold climate conditions. Surface infiltration rate was substantially affected by winter sanding materials for PA, PC, and PICPs. Pressure washing was demonstrated to be able to partially restore surface infiltration rates for all three types of pavements. All pavement types in general have the same level of performance in removing TSS, TP, TN, and heavy metals. The removal of TSS, TP, and heavy metals appears to be independent of climatic conditions, whereas TN removal tends to decline with a decrease in pavement temperature.