Lagrangian Method to Model Advection-Dispersion-Reaction Transport in Drinking Water Pipe Networks.

A Lagrangian method to simulate the advection, dispersion, and reaction of a single chemical, biological, or physical constituent within drinking water pipe networks is presented. This Lagrangian approach removes the need for fixed computational grids typically required in Eulerian and Eulerian-Lagrangian methods and allows for nonuniform computational segments. This makes the method fully compatible with the advection-reaction water quality engine currently used in EPANET. An operator splitting approach is used, in which the advection-reaction process is modeled before the dispersion process for each water quality step. The dispersion equation is discretized using a segment-centered finite-difference scheme, and flux continuity boundary conditions are applied at network junctions. A staged approach is implemented to solve the dispersion equation for interconnected pipe networks. First, a linear relationship between the boundary and internal concentrations is established for every pipe. Second, a symmetric and positive definite linear system of equations is constructed to calculate the concentrations at network junctions. Last, pipe internal concentrations are updated based on the junction concentrations. The solution generates exact results when the analytical solutions are available and leads to more accurate water quality simulations than advection-reaction-only water quality models, especially in the areas where dispersion dominates advection.

Framework for Modeling Lead in Premise Plumbing Systems Using EPANET.

The lead contamination of drinking water in homes and buildings remains an important public health concern. In order to assess strategies to measure and reduce exposure to lead from drinking water, models are needed that incorporate the multiple factors affecting lead concentrations in premise plumbing systems (PPS). In this study, the use of EPANET, a commonly used hydraulic and water quality model for water distribution systems, was assessed for its ability to predict lead concentrations in PPS. The model was calibrated and validated against data collected from multiple experiments in the EPA's Home Plumbing Simulator that contained a lead service line and other lead sources. The EPANET's first-order saturation kinetics model was used to simulate the dissolution of lead in the lead service line. A version of EPANET was developed to include one-dimensional mass dispersion. Modeling results were compared to experimental data, and recommendations were made to improve the EPANET-based modeling framework for predicting lead concentrations in PPS.

Efficacy of inactivation of human enteroviruses by dual-wavelength germicidal ultraviolet (UV-C) light emitting diodes (LEDs).

The efficacy of germicidal ultraviolet (UV-C) light emitting diodes (LEDs) was evaluated for inactivating human enteroviruses included on the United States Environmental Protection Agency (EPA)'s Contaminant Candidate List (CCL). A UV-C LED device, emitting at peaks of 260 nm and 280 nm and the combination of 260∣280 nm together, was used to measure and compare potential synergistic effects of dual wavelengths for disinfecting viral organisms. The 260 nm LED proved to be the most effective at inactivating the CCL enteroviruses tested. To obtain 2-log10 inactivation credit for the 260 nm LED, the fluences (UV doses) required are approximately 8 mJ/cm2 for coxsackievirus A10 and poliovirus 1, 10 mJ/cm2 for enterovirus 70, and 13 mJ/cm2 for echovirus 30. No synergistic effect was detected when evaluating the log inactivation of enteroviruses irradiated by the dual-wavelength UV-C LEDs.

Treatment of reverse osmosis concentrate using an algal-based MBR combined with ozone pretreatment.

Algal treatment was combined with ozone pretreatment for treatment of synthetic reverse osmosis concentrate (ROC) prior to microfiltration. The research mainly focused on minimizing the fouling of polyvinylidene-fluoride membranes and maximizing the restoration of membrane permeability. The algal treatment alone was only moderately effective for the mitigation of fouling in microfiltration, while a markedly improved performance was achieved when the algal treatment followed ozonation. The combination of ozonation and algal treatment reduced membrane permeability decline and significantly (p < 0.05) increased the reversibility of fouling after hydraulic washing. A longitudinal evaluation was also performed with a goal of achieving a robust removal of contaminants. Ozonation followed by algal treatment was very effective in attenuating both caffeine and carbamazepine, as well as removing organic matter and inorganic nutrients from ROC in a single bioreactor. In this study, an alkaline condition (∼pH 12), produced by microalgae in the light without supplemental aeration was applied for in-situ cleaning of fouled membranes. The result showed that the algal-induced cleaning successfully restored the permeability of organic-fouled membranes during the filtration of both raw and algal-treated ROC. This in-situ strategy offers a novel option for periodic cleaning of fouled membranes while maintaining operational simplicity, especially for existing submerged membrane filtration facilities.

A proof of concept study for wastewater reuse using bioelectrochemical processes combined with complementary post-treatment technologies.

This article describes a proof-of-concept study designed for the reuse of wastewater using microbial electrochemical cells (MECs) combined with complementary post-treatment technologies. This study mainly focused on how the integrated approach works effectively for wastewater reuse. In this study, microalgae and ultraviolet C (UVC) light were used for advanced wastewater treatment to achieve site-specific treatment goals such as agricultural reuse and aquifer recharge. The bio-electrosynthesis of H2O2 in MECs was carried out based on a novel concept to integrate with UVC, especially for roust removal of trace organic compounds (TOrCs) resistant to biodegradation, and the algal treatment was configured for nutrient removal from MEC effluent. UVC irradiation has also proven to be an effective disinfectant for bacteria, protozoa, and viruses in water. The average energy consumption rate for MECs fed acetate-based synthetic wastewater was 0.28±0.01 kWh per kg of H2O2, which was significantly more efficient than are conventional electrochemical processes. MECs achieved 89±2% removal of carbonaceous organic matter (measured as chemical oxygen demand) in the wastewater (anolyte) and concurrent production of H2O2 up to 222±11 mg L-1 in the tapwater (catholyte). The nutrients (N and P) remaining after MECs were successfully removed by subsequent phycoremediation with microalgae when aerated (5% CO2, v/v) in the light. This complied with discharge permits that limit N to 20 mg L-1 and P to 0.5 mg L-1 in the effluent. H2O2 produced on site was used to mediate photolytic oxidation with UVC light for degradation of recalcitrant TOrCs in the algal-treated wastewater. Carbamazepine was used as a model compound and was almost completely removed with an added 10 mg L-1 of H2O2 at a UVC dose of 1000 mJ cm-2. These results should not be generalized, but critically discussed, because of the limitations of using synthetic wastewater.