Journal of Environmental Engineering

The anaerobic hydrolysis rate of organic solid waste was studied at fixed volatile fatty acid (VFA) concentrations ranging from 3 to 30 g COD/L and fixed pH values between 5 and 7. For separate control of both VFA and pH, a special completely mixed reactor was designed. In this way, it was possible to distinguish between the inhibitory effects of pH, total VFA, and undissociated VFA on anaerobic hydrolysis. It was shown that hydrolysis of the organic solid waste followed first-order kinetics. Using a statistical analysis, it was found that the hydrolysis rate constant was pH dependent but was not related to the total VFA and undissociated VFA concentrations.

This work examines the thermal pyrolysis characteristics of polyelectrolyte-flocculated activated sludge at a heating rate up to 873 K by means of thermogravimetric analysis (TGA). Although the polyelectrolyte does not affect the pyrolysis rate of the sludge at a temperature of 8 or 14 K/min, using polyelectrolyte flocculation to charge neutralization appears to accelerate the pyrolysis process at 20 K/min. TGA/mass spectrometer tests were performed to identify the species released during pyrolysis of the sludges. A parallel-reaction kinetic model (Reactions 1 and 2) was applied to interpret the experimental data, with Reaction 1 corresponding to the release of C₇H₁₄ equivalents or lighter, and Reaction 2 corresponding to the heavier compounds. Using polyelectrolyte flocculation to change the neutralization point enhances Reaction 1 by transforming the heavier organics that are originally released at elevated temperature (Reaction 2) to the lighter compounds in the low-temperature regime (Reaction 1).

An investigation was conducted to develop a practical approach for in situ moisture content monitoring of municipal solid waste landfills. This paper describes the three phases of investigation: feasibility assessment to identify the most viable technique, laboratory program to quantify limitations, and field application trial. The study concluded that there is no indirect method that can be used in landfills without some difficulty and limitations. However, provided certain limitations are accepted, the use of a neutron probe with in situ access tubes offers the advantages of reliability, ease of measurement, nondestructiveness, repeatability and, most importantly, a large effective sampling volume to achieve a macroscopic-scale moisture content measurement. A practical field installation procedure also is recommended.

This four-year study evaluated the effect of phosphate inhibitors on the corrosion of iron pipes under extended stagnant water conditions. Study parameters included pH and alkalinity, age of the pipe, water stagnation time, and inhibitor type. For iron release, addition of phosphate inhibitors had no statistically significant effect (at 95% confidence) in two-thirds of the experiments. In the remaining experiments, addition of orthophosphate or zinc orthophosphate always increased iron concentration. Polyphosphate addition decreased iron release at only one water quality and increased it at other conditions. For weight loss, polyphosphate inhibitor dosing did not decrease the extent of scale buildup or overall weight loss. Orthophosphate dosing reduced overall weight loss at only one water quality condition; at all other conditions, the addition of orthophosphate had a detrimental effect.

Ponds holding industrial wastewater can quickly develop algal blooms, which in turn results in high pH excursions. Such deterioration in water quality is experienced in Portland Aluminium's retardation pond. A covering of floating aquatic plants, such as Azolla filiculoides and Lemna minor, will reduce the light entering the water body, in turn reducing algal production and lowering pH levels. In the case of Portland Aluminium's retardation pond, the initial installation of such a system has to be established under alkaline conditions and in high fluoride concentrations (up to 10 mg/L). The survival and growth of A. filiculoides and L. minor under alkaline conditions (pH levels of 7–9.5) and under different fluoride concentrations (0–10 mg/L) were assessed in the laboratory and in field conditions. L. minor grew well under alkaline and high fluoride conditions in short-term laboratory tests, but appeared unable to compete with itinerant algae in the field. A. filiculoides survived only in media of pH 7 and 0-mg/L fluoride in the short-term laboratory tests, but grew very well in the long-term field experiments. A. filiculoides was also observed to inhibit algal growth in the field. Both species absorbed fluoride. Fluoride concentrations in the plants rose and fell in relation to the fluoride concentrations in the pond, suggesting that the fluoride was readily desorbed and that the absorption itself was by a passive mechanism.

A time-dependent mechanistic model has been developed to describe the coupled heat and mass transfer during microwave steam treatment of contaminated soils. The model consists of multiphase mass and energy conservation equations, along with various temperature-dependent parameterizations of important physical state properties. The coupled nonlinear equations were solved numerically by applying a macroscopic control volume method with the appropriate boundary and initial conditions and using a finite-difference scheme. Microwave heating experiments of soil samples were performed. The effects of microwave power, soil sample depth, and soil type on water evaporation rate and temperature were measured with time. The modeled results are in good agreement with the experimental data. The results revealed that microwave power density and soil sample depth significantly affect the microwave evaporation process of water from soils. Water evaporation rate and temperature variation are complex and associated with the dielectric properties of liquid water distributed within the soil. The deeper the soil sample, the more nonuniform the evaporation process, although nonuniformities diminish as the evaporation process approaches completion. Finally it was verified that soil types and their thermal properties play a minor role, provided that the soil minerals are microwave transparent.

The state of air pollution in Japan, and in particular in Nagoya, has improved since the 1960s in terms of sulfur dioxide (SO₂) and carbon monoxide (CO). However, suspended particulate matter (SPM), nitrogen oxides (NO_x) emitted by automobiles, and photochemical oxidants (O_x), especially ozone (O₃), have become major pollution problems in urban life. Nagoya has adopted a number of measures to improve air quality, such as air pollution monitoring, regulation and guidance for industries and businesses, and measures against automobile exhaust gases. This paper reviews the air quality measures in Nagoya and develops an empirical model for evaluating urban SPM concentration in problem areas. The model presented in this study is suitable for predicting long-term average SPM concentrations and can be utilized for analyzing the effects of various traffic emission reduction strategies. In addition, this model can be utilized for new urban development as an alternative to vigorous monitoring by predicting long-term SPM concentration from NO_x monitoring data.

A field study was conducted over an intermittent period of 2.5 years to determine whether air cleaning, using a portable high efficiency particulate air filter air cleaner with an activated carbon filter, was a viable method of reducing indoor radon levels. Past studies showed that air cleaners could reduce radon and/or radon progeny concentrations. The data collected in this study showed that the air cleaner did not reduce radon levels and so was not an effective mitigation device. The data also showed that above radon levels of 6 pCi/L there was a strong positive linear correlation to moisture content. Below 6 pCi/L there was essentially no correlation. Radon concentrations were determined using EPA approved commercial test kits that were occasionally run in duplicate. In these cases it was found that there was good reproducibility between the test kits over a range of levels from 1.1 to 14.5 pCi/L, with the average difference being under 10%.

The discovery in California of methyl tertiary-butyl ether (MTBE) in surface waters used for recreational boating has raised concerns over the potential impact on drinking water quality. Concentrations of MTBE above the California secondary maximum contaminant level of 5 ppb have been reported. Here we present a model to predict the fate of MTBE in surface waters as a function of wind speed, water temperature, epilimnion depth, and lake surface area. The model was validated with MTBE concentration data from Lake Perris in southern California and Calero Reservoir in northern California. When applied to typical lake conditions in California [i.e., epilimnion depth <11 m (<35 ft) and water temperature >15°C], the maximum half-life for MTBE is <40 days for quiescent conditions, and as low as 6 days if the average wind speed is >4.5 m/s (10 mi/h). The model can be used for management of recreational boating based on a target MTBE concentration in the reservoir.

A mass balance approach was used to determine the most important nonpoint source of volatile organic compounds (VOCs) in storm water from an asphalt parking lot without obvious point sources (e.g., gasoline stations). The parking lot surface and atmosphere are important nonpoint sources of VOCs, with each being important for different VOCs. The atmosphere is an important source of soluble, oxygenated VOCs (e.g., acetone), and the parking lot surface is an important source for the more hydrophobic VOCs (e.g., benzene). VOCs on the parking lot surface appear to be concentrated in oil and grease and organic material in urban particles (e.g., vehicle soot). Except in the case of spills, asphalt does not appear to be an important source of VOCs. The uptake isotherm of gaseous methyl tert-butyl ether on urban particles indicates a mechanism for dry deposition of VOCs from the atmosphere. This study demonstrated that a mass balance approach is a useful means of understanding non-point-source pollution, even for compounds such as VOCs, which are difficult to sample.

Effect of hydraulic retention time (HRT) on the acidogenesis of dairy wastewater was studied using an upflow reactor at pH 5.5, 37°C, and six HRTs ranging from 4 to 24 h. Results showed that the degree of acidification increased rapidly with HRT from 28.2% at 4 h to 54.1% at 12 h; further increase of HRT to 16 and 24 h only increased acidification slightly to 55.8 and 59.1%, respectively. The biodegradability of the three major constituents in dairy wastewater increased with HRT, following the order of carbohydrates > proteins > lipids. The predominant products were acetate, propionate, butyrate, lactate, and ethanol.

Feasibility of the upflow anaerobic sludge blanket (UASB) process was investigated for the treatment of tapioca starch industry wastewater. After removal of suspended solids by simple gravity settling, starch wastewater was used as a feed. Start-up of a 21.5-L reactor with diluted feed of approximately 3,000 mg/L chemical oxygen demand (COD) was accomplished in about 6 weeks using seed sludge from an anaerobic pond treating tapioca starch wastewater. By the end of the start-up period, gas productivity of 4–5 $m^3/m^{{\mathit{3}}_{\mathit{r}}\cdot \mathrm{day}}$ was obtained. Undiluted supernatant wastewater with a COD concentration of 12,000–24,000 mg/L was fed during steady-state reactor operation at an organic loading rate of 10–16 kg $\mathrm{COD}/m^{{\mathit{3}}_{\mathit{r}}\cdot \mathrm{day}\text{.}}$ The upflow velocity was maintained at 0.5 m/h with a recirculation ratio of 4:1. COD conversion efficiencies >95% and gas productivity of 5–8 $m^3/m^{{\mathit{3}}_{\mathit{r}}\cdot \mathrm{day}}$ were obtained. These results indicated that removal of starch solids from wastewater by simple gravity settling was sufficient to obtain satisfactory performance of the UASB process.

While successful in removing turbidity and pathogens from drinking water, slow sand filters require ripening periods at the beginning of each filter run. The premise of this research was that it should be possible to enhance the ripening of slow sand filters. Potential ripening agents were screened by assessing their interaction with the surface of filtration media and turbidity particles. Four natural organic polymers and nine synthetic polymers were investigated for their potential to enhance filter ripening. Of the 13 modifying agents considered, none conclusively sorbed to the filter media, and only one, a synthetic polymer, interacted with kaolin particles. A filter modified with continuous feed of the polymer ripened successfully and produced water with turbidity below 1.0 NTU in about 24 h. Most turbidity removal in the treated filter occurred in the schmutzdecke rather than within the depth of the filter bed. Hence, the mechanism of enhanced ripening in this case probably was particle agglomeration with resulting acceleration of particle deposition at the filter surface accompanied by straining or attachment to previously removed particles.