Journal of Environmental Engineering

The barrier properties of composite membranes containing either zero-valent iron nanoparticles or powdered activated carbon mixed into an aqueous clay suspension and sandwiched between two sheets of high-density polyethylene were measured using carbon tetrachloride and trichloroethylene as model contaminants. The lag time to trichloroethylene breakthrough increased 17-fold when $24\mathrm{wt}\%$ powdered activated carbon was mixed into the $\mathrm{400-}\mu \mathrm{m}$ -thick center layer of the composite. Zero-valent iron was successful in extending the lag time for carbon tetrachloride but not for trichloroethylene, presumably because the latter reaction with zero-valent iron is slow relative to diffusion. Approximately 30% of the total iron in the composite membrane was consumed before carbon tetrachloride breakthrough, a major improvement over the 2–3% reported previously for single-layer high-density polyethylene membranes containing iron nanoparticles. Simplified multilayer membrane models used to describe contaminant breakthrough are consistent with the experimental results.

This study examined a common form of filtration, a passive radial cartridge filter (RCF) system, to physically separate hetero-disperse particulate matter in rainfall-runoff. The RCF tested utilizes aluminum-oxide coated media with a uniform pumice substrate $(d_{50\mathrm{m}}=3.56\mathrm{mm})$ gradation. To examine the RCF, this study applied laser diffraction and real-time pressure sensor measurements to validate a computational fluid dynamics (CFD) model to predict particle separation and filter head loss for hetero-disperse particulate matter (PM). Filter hydrodynamics are resolved using a macroscopic approach for the porous media with a $k\text{-}\epsilon$ turbulence model coupled with the Ergun equation. PM fate was resolved using a discrete phase model. CFD results closely followed measured data for filtration and head-loss response for all flow rates. With influent PM at $200\mathrm{mg}∕\mathrm{L}$ $(d_{50\mathrm{m}}=16.3\mu \mathrm{m})$ , effluent PM ranged from $32\text{to}57\mathrm{mg}∕\mathrm{L}$ for surface loading rates of $24\text{to}189\mathrm{L}∕{\mathrm{m}}^2\min$ , respectively. There was agreement between measured and modeled data for effluent PM and head loss. CFD postprocessing provided added insight into the mechanistic behavior of the RCF by means of three-dimensional hydraulic profiles, particle trajectories, and pressure distributions, illustrating that a RCF is nonuniformly loaded. As part of design and regulation, such physical testing coupled with modeling is a required precursor to uncontrolled field testing, regular maintenance and certification of a BMP.

A pilot scale up-flow anaerobic sludge blanket (UASB) coupled with cross-flow membrane filtration was used to treat low strength municipal wastewater in Singapore. The application of membrane filtration as a polishing unit of UASB effluent could produce better effluent quantity than conventional UASB. In this research, with gradually reducing hydraulic retention time from $10.0\text{to}5.5\mathrm{h}$ , membrane effluent was able to meet the more stringent effluent criterion over the whole experiment. Simultaneously, biogas yield increased from $61.8\text{to}120.7\mathrm{mL}∕\mathrm{g}$ ${\mathrm{COD}}_{\text{removed}}$ , in which methane percentages were also increased from 59.3 to 65.2%, respectively. Furthermore, the results of anaerobic membrane filtration showed that there were three different methods could effectively mitigate rapid membrane fouling and maintain trans-membrane pressure as low and stable as possible. These would reduce membrane cleaning frequency and prolong membrane life span.

Hydrologic models play an important role in the assessment of nonpoint source (NPS) pollution, which is essential for the environmental management of water resources. The present study has been undertaken to evaluate the applicability of a physically based continuous time scale, hydrological, and water quality computer model—Hydrologic Simulation Program-Fortran (HSPF)—in simulating runoff and sediment associated NPS pollutant losses from a small mixed type (land under agriculture, shrubs and forest, rocks, grasses) watershed of the Damodar Valley Corporation, Hazaribagh, India. Water soluble $\mathrm{N}{\mathrm{O}}_3–\mathrm{N}$ , $\mathrm{N}{\mathrm{H}}_4–\mathrm{N}$ , and P were considered as pollutants and their concentrations in the runoff were measured at the outlet of the watershed, randomly for 15 dates during the monsoon season (June–October) of 2000 and 2001. The model calibration and validation results reveal that the seasonal trend of HSPF simulated runoff, sediment yield, and NPS pollutants compared reasonably with their measured counterparts. Although the concentrations of pollutants were generally overpredicted for $\mathrm{N}{\mathrm{O}}_3–\mathrm{N}$ and underpredicted for $\mathrm{N}{\mathrm{H}}_4–\mathrm{N}$ and water-soluble P in the month of June when fertilizers releasing $\mathrm{N}{\mathrm{H}}_4–\mathrm{N}$ and P are applied in rice fields, the differences in the mean concentration were not significantly different at a 95% level of confidence. Variation in the simulated losses of water soluble N and P species between the years occurred largely due to differences in the amount and distribution of rainfall. These results indicate that the HSPF model can be used as a tool for simulating runoff and sediment associated NPS pollution losses from the study area.

Typically, microbes associated with biological wastewater treatment processes are subjected to dynamic organic and nutrient loading conditions. This constantly changing environment imposes a stress, referred to as “feast-famine” that selects for microbes capable of biologically storing substrates as polymers during high organic concentration periods (i.e., feast) for use during periods of low organic availability (i.e., famine). In this study, we monitored the production of biostorage polymers generated with actual cheese wastewater treatment by way of sequencing batch reactors (SBRs). SBRs were employed and operated in duplicate under two long (i.e., hours) filling scenarios (1) “react fill” with mixing/aeration and (2) “static fill” with no mixing/aeration. Despite comparable effluent water quality levels, the results reveal that a “static fill” approach outperforms a “react fill” with respect to maximum biostorage polymer production (50% more poly- $\beta$ -hydroxybutyrate, 15% more glycogen). The presence of biostorage polymer production has been shown to be indicative of a more stable and robust process.

Hydraulic jumps, plunging jets and stepped channels are generally used as energy dissipators and self-aerators. Accordingly, it is expected to find a positive correlation between the aeration efficiency and energy dissipation. For this purpose, hydraulic jump self-aeration efficiency has been investigated with the function of energy dissipation rate per unit width. The hydraulic jump data revealed a positive linear relationship between the aeration efficiency and energy dissipation rate. This new procedure could have practical implications for predicting hydraulic jump aeration efficiency.