Journal of Environmental Engineering

Several food processors use land application to treat process wastewater. Excessive organic and hydraulic loadings can result in environmental harm through surface water runoff and groundwater contamination. A recently recognized impact is the mobilization of heavy metals from the soil. The metals serve as the electron acceptors when oxygen is depleted and anaerobic microorganisms predominate. The objective of this research is to determine the feasibility of using moisture and oxygen sensors to predict changes in the soil environment resulting from the addition of wastewater that leads to anaerobic conditions. Eight 46-cm diameter, 0.97-m tall columns were constructed, filled with clean sand, and instrumented with sensors at three depths. Three organic loadings were tested: 7-, 56-, and $112\text{-g}\text{biological}\text{oxygen}\text{demand}/{\text{m}}^2/\text{day}$ . The sensors predicted soil conditions that led to the leaching of Mn and chemical oxygen demand from the more highly loaded columns. Trends from the phospholipid and respiratory quinone analyses indicated a shift to anaerobic biomass for the more highly loaded columns. The use of sensors as part of an irrigation strategy has potential to predict safe loading levels as compared to a prescriptive approach that uses fixed hydraulic and organic loadings without regard to wastewater characteristics, soil conditions, and weather.

Adsorptive filtration is becoming a common unit operation/process following a primary unit operation such as volumetric clarification of urban drainage flows and particulate matter. In this study, axial columns packed with aluminum oxide coated media (AOCM) were used to examine breakthrough phenomena and models for total dissolved phosphorus (TDP) at levels typical of urban drainage primary effluent. Mechanistic Langmuir and Freundlich models incorporated a one-dimensional mass balance, transport equation, mass transfer model, and initial and boundary conditions. Parameters of the mechanistic models were determined by isotherm and kinetics testing of TDP adsorption on AOCM. Empirical Thomas model and empirical bed-depth-service-time model were also examined. Measured TDP adsorption breakthrough curves (BTCs) demonstrated typical “S-shaped” curves. Results indicated that smaller AOCM media (higher specific surface area), slightly acidic pH, lower TDP concentrations, and lower surface loading rates generated increased breakthrough capacity. While ${\text{Ca}}^{2+}$ enhanced, and ${\text{SO}}_4^{2-}$ inhibited breakthrough capacity, combined at urban drainage concentrations, these interactions were small compared to other tested parameters. Media capacities determined by BTC were smaller than isotherm capacities of longer contact time. Results indicate that the Thomas model most consistently reproduced measured BTCs within the range of typical urban drainage conditions.

Volumetric clarification incorporating filtration with engineered granular media is increasingly used as a viable combined unit operation for separation of rainfall-runoff particulate matter (PM). Such combined unit operations are typically operated at the catchment-level for rainfall-runoff clarification of transient loadings, in contrast to centralized watershed or sewershed regional treatment. Using computational fluid dynamics (CFD), this study models the PM separation by a volumetric clarifying filter (VCF) subject to unsteady event-based hydrologic, hydraulic, mass, and particle size distribution (PSD) loadings. Modeled and measured physical model results indicate that the VCF is capable of PM load reductions and effluent concentrations at or below 30 mg/L. These results, with PM measured as suspended sediment concentration (SSC) represent reductions ranging from 83 to 97% on an event basis. CFD model results predict effluent PM mass loads. Modeled effluent median particle diameter $\left(d_{50\text{m}}\right)$ , as an index for the filtered effluent PSD, reproduces the $d_{50\text{m}}$ from the VCF physical model on an event basis. Filter head loss is examined as a function of flow rate. Despite geometric asymmetry of the multiple radial cartridge configuration tested, hydraulic loading for each individual cartridge is relatively uniform.

Household water treatment with dilute hypochlorite solution has been shown to improve microbiological water quality and reduce diarrheal disease in developing countries. One concern raised by governmental agencies, implementers, and nongovernmental organizations is whether the hypochlorite solution remains stable during distribution and after the bottle is opened and usage begins. In this study, laboratory and field research was conducted to determine the expiration date and stability in the home of hypochlorite solution. Expiration-date testing found that pH-stabilized $\sim 1.25\mathrm{\%}$ hypochlorite solution made using various production techniques in Ethiopia, Guinea, and Nigeria was stable for a minimum of 12 months in temperatures less than $35°\text{C}$ . Stability testing during laboratory simulated normal usage showed no degradation, and 77–91% of bottles collected from households tested met standards. Hypochlorite solution concentration drops rapidly when pH is not stabilized, when pH levels fall, and when solution is exposed to direct sunlight.

Organic contaminants may permeate through plastic pipes in water distribution systems and adversely affect the quality of drinking water. In this study, we developed a microscopic visualization technique to investigate the permeation of common organic contaminants (benzene, toluene, ethylbenzene, xylene, and trichloroethene) through polyvinyl chloride (PVC) pipes. By observing the propagation of organic moving fronts in the pipe materials with a light microscope, the technique was able to predict the permeation breakthrough times through PVC pipes that were determined in the pipe-bottle test. The advance of an organic moving front was found to be linearly dependent on the square-root of time and the propagation rate increased with an increase in the external organic chemical activity. Permeation of organic mixtures into PVC pipes was found to be additive in proportion to the permeation rates and volume percents of each component. In combination with a 2-year pipe-bottle test for PVC pipes exposed to premium gasoline, mathematical extrapolations based on the microscopic visualization tests predicted that PVC pipe are likely to resist permeation by commercial gasoline for the service life of the pipe.

The first full-scale nitritation and anaerobic ammonium oxidation (Anammox) processes for an inorganic wastewater of semiconductor factory were installed and performances were evaluated. Existing facilities of conventional nitrification and denitrification were retrofitted to a combination of the nitritation and Anammox process. Novel nitritation method, selective acceleration of ammonia oxidation by high concentration of inorganic carbon, was evaluated in full-scale aeration tank with carrier material. The ammonia conversion rate of the nitritation reactor was in the range of $0.27–0.48\text{kg}{\text{NO}}_2\text{-N}/{\text{m}}^3\text{day}$ after start-up period, and stable nitritation was achieved for over 10 months. In an Anammox reactor, on-site cultivation of anammox bacteria was performed, and the most plausible reason for slower nitrogen conversion at the beginning was oxygen contamination into the reactor. After minimizing influence of oxygen contamination, design loading was achieved within 3 months of operation. After start-up period, stable Anammox reactions are maintained for over 10 months. The nitrogen removal rate after start-up period was in the range of $1.04–3.29\text{kg}\text{N}/{\text{m}}^3\text{day}$ . In combination with conventional denitrification process, soluble nitrogen in the final effluent was reduced below 8 mg/L.

Storm-water best management practices (BMPs) are typically assessed using the performance metric of pollutant concentration removal efficiencies. However, debate exists whether this is the most appropriate metric to use. In this study, a storm-water wetland constructed and monitored in the coastal plain of North Carolina is evaluated for water quality and hydrologic performance using four different metrics: concentration reduction, load reduction, comparison to nearby ambient water quality monitoring stations, and comparison to other wetlands studied in North Carolina. The River Bend storm-water wetland was constructed in spring 2007 and was monitored from June 2007 through May 2008. Twenty-four hydrologic and 11 water quality events were captured and evaluated. The wetland reduced peak flows and runoff volumes by 80 and 54%, respectively. Reductions were significant. Concentrations for the following pollutants increased: total kjeldahl nitrogen (TKN), NH4–N, total nitrogen (TN), and total suspended solids (TSS); inflow and outflow concentrations did not change for total phosphorus (TP), while only ${\text{NO}}_{2–3}–\text{N}$ and orthophosphorus (OP) concentrations were lower at the outlet. Using a load reduction metric, results were strikingly different, showing positive load reductions of 35, 41, 42, 36, 47, 61, and 49% for these respective pollutants: TKN, ${\text{NO}}_{2–3}–\text{N}$ , ${\text{NH}}_4–\text{N}$ , TN, TP, OP, and TSS. When comparing the effluent concentrations from the wetland to ambient water quality in the Trent River, all effluent nitrogen species concentration were either similar or lower. TP and TSS concentrations leaving the wetland were higher than ambient water quality data. Finally, by comparing pollutant concentrations among different North Carolina wetlands, it is apparent the River Bend wetland received relatively “clean” water and released water with pollutant concentrations comparable to all other studies examined. Major conclusions from this study include: (1) storm-water wetlands sited in sandier soils (such as those of the North Carolina coastal plain) should be considered a low impact development tool and (2) the selection of performance metric has a pronounced bearing on how a BMP’s performance is perceived. Sole reliance on a concentration reduction metric is discouraged.