Chemical fate models can be used to estimate the transformation reactions and the partitioning behavior of pharmaceuticals and personal care products (PPCPs) in sewage treatment plants (STPs). Modeling the fate of PPCPs in a STP requires parameters such as rate constants or partition coefficients that are often unique to a specific STP, and that may exhibit significant temporal variability. Chemical fate models provide both a valuable test of our understanding of the fundamental underlying mechanisms regarding the fate of PPCPs in STPs, as well as a means of providing both qualitative and quantitative estimates for PPCP removal. This paper is not intended to provide calibration or validation of these models for a specific system, but rather to review the most common approaches to modeling the chemical fates of PPCPs in STPs (as well as other chemicals and other systems).

This paper reviews the current United States sewage sludge disinfection regulations and their associated practices; discusses the limitations of the practices; the criteria employed in evaluating a new (innovative or alternative) disinfection process, and notes both some processes recently evaluated and ones evaluated. The United States regulations are designed to protect human health by minimizing the contact of humans with pathogenic microorganisms. Two types of disinfection processes are employed. Processes like pasteurization are employed to reduce pathogens below their analytical detection limits, while processes like anaerobic digestion are combined with requirements for organic matter reduction and access restrictions. Issues with the present disinfection alternatives such as their only being concerned with the presence or absence of certain pathogens like enteric viruses or Ascaris sp. are discussed and remedies suggested. Similarly, several of the current options for measuring vector attractiveness (stability) such as volatile solids reduction are in need of improvement. Work is underway to evaluate bacterial enzymatic activity and biochemical oxygen demand as possible measures of vector attractiveness. Innovative and alternative methods for disinfection are frequently proposed and it is important to understand how the stressors employed by the process contribute to its reduction of pathogenic bacteria, viruses, protozoa, and parasites. For example with an alkaline disinfection process it may be possible to utilize the beneficial effects of time, temperature, pH, chemical agents like ammonia, and pressure. A two-phase and batch thermophilic anaerobic digestion system, however, is able to utilize the benefits of high temperature, high levels of volatile fatty acids, and free ammonia to accomplish a large reduction of pathogens. Vermicomposting and a process that uses a fumigant are currently under evaluation by the U.S. Environmental Protection Agency and briefly discussed.

A three-stage process was developed at Lawrence Livermore National Laboratory to treat potentially pyrophoric depleted uranium metal wastes. The three-stage process includes waste sorting/rinsing, acid dissolution of the waste metal with a hydrochloric and phosphoric acid solution, and solidification of the neutralized residuals from the second stage with clay. The final product is a solid waste form that can be transported to and disposed of at a permitted low-level radioactive waste disposal site.

Oil production generates a significant amount of water byproduct known as produced water. Following primary gravity separation, produced water is normally disposed of by injection into the formation from which it came. However, high amounts of suspended solids or oil in the produced water may cause significant problems if the injection formation becomes clogged. This study evaluated the effectiveness of dissolved air flotation in treating two produced water samples obtained from Saskatchewan heavy oil production sites. In the dissolved air flotation experiments, maximum oil and suspended solids removals were 77 and 59%, respectively. The use of polymers with dissolved air flotation showed maximum oil and suspended solids removals of 94 and 66%, respectively.

Particle size distribution studies were performed on raw, hydrolyzed, sterilized, and Bacillus thuringiensis (Bt) fermented wastewater sludge at different solids concentration $(10–40\mathrm{g}{\mathrm{L}}^{-1})$ . Correlations of particle size (PRS) were drawn with different parameters like sludge volume index (SVI), sedimentation velocity, viable spores, and entomotoxicity. The volume distribution of particle size showed a greater number of particles for hydrolyzed fermented wastewater sludge in the $0.2–12\mu \mathrm{m}$ region in comparison to nonhydrolyzed Bt fermented sludge where the PRS was restrained to a $0.5–10\mu \mathrm{m}$ region at a cumulative volume percent of 30 and 20%, respectively, irrespective of solids concentration. Similar trends were observed for surface distribution profiles. The entomotoxicity decreased and SVI increased with an increase in particle size. The sedimentation velocity was computed based on Stoke’s law and was lower for hydrolyzed sludge. The lower SVI and particle size of hydrolyzed fermented sludge are the required characteristics suitable for biopesticidal formulations serving as an excellent Bt fermented medium for the purpose. Thus, PRS can act as an important tool in screening sludges as raw materials for Bt based biopesticide fermentation, centrifugation, formulation, and field application.

In pace with a growing focus on environmental protection, geophysical techniques to characterize abandoned hazardous sites contribute necessary information for remediation. Study of physical property distribution in the subsurface allows insight relevant to the successful investigation of such sites. Resistivity image profiling (RIP) is one of the most effective and stable geophysical techniques for contaminated land investigations where it is generally desirable to minimize ground disturbance. A former gas factory and carbide waste disposal site in Hsin-Hua County of southern Taiwan was being investigated. The site is located next to a low-density residential community and was previously considered unattractive. It is now being developed for domestic infrastructure and has to be cleaned. Records of dumping activities are poor. In order to estimate the budget of future remediation, RIP works were used to determine buried carbide geometry such as the thickness of fill and the spread of waste carbide. In addition, assessment of groundwater contamination associated with this landfill is also a main concern of this study. The thickness of waste carbide computed from RIP data was confirmed by post borings. The final carbide layer sections obtained from the RIP survey provide the base data to calculate the amount of carbide. Mapping of relative changes of resistivities with depth indicates that free water flows across the site in approximately a southwesterly direction. The presence of clayey soil may prevent a downward migration of leachate plume emanating from the carbide. Two-dimensional RIP resistivity surveying did very efficiently in waste carbide disposal explorations and provides relevant information on this area.

The Chiang-Chun River basin is the largest and the most intensively used river basin in Tainan County, Taiwan. Based on the recent water quality analysis, the Chiang-Chun River is heavily polluted. Concern about the deteriorating condition of the river led the Government of Taiwan to amend the relevance legislations and strengthen the enforcement of the discharge regulations to effectively manage the river and control the pollution. Investigation results show that the hog farming is one particularly important activity in the watershed. Most of the untreated hog farm waste is indiscriminately discharged into the river. Moreover, municipal wastewater in the watershed is also discharged into the river without proper treatment. Thus, the hog farm and municipal wastewaters are the major causes of the deterioration of water quality of Chiang-Chun River. Currently, the percent of sewer system connection in the Chiang-Chun River watershed is less than 1%. Investigation results show that the daily wastewater, biochemical oxygen demand (BOD), and ${\mathrm{NH}}_3\text{-}\mathrm{N}$ loadings into the river are approximately $\mathrm{101,600}{\mathrm{m}}^3$ , $\mathrm{15,800}\mathrm{kg}$ , and $\mathrm{3,900}\mathrm{kg}$ , respectively. Results also indicate that the domestic wastewater and hog farm waste contribute more than 50% of the daily BOD and ${\mathrm{NH}}_3\text{-}\mathrm{N}$ loads to the river, respectively. In this study, the enhanced stream water quality model was selected as a water quality-planning tool to perform the water quality evaluation and carrying capacity calculation. The calculated BOD and ${\mathrm{NH}}_3\text{-}\mathrm{N}$ carrying capacities were 2,700 and $210\mathrm{kg}$ per day, respectively. A comprehensive strategy for the management of Chiang-Chun River basin has been proposed based on the results from water quality investigation and modeling. The strategy consists of short-term management and improvement measures, long-term structural measures (e.g., sewer system construction to achieve 30% of connection in the basin within 10 years), and land use management and legislation (e.g., river bank management and enforcement of wastewater discharge standards). After the implementation of the proposed measures, the water quality can be significantly improved. The developed watershed management strategies can also be applied to other similar watersheds.

Natural clay deposits and compacted clay liners are used as landfill barriers; however, there is no consensus on what an appropriate thickness of the barrier ought to be, due to difficulties encountered while analyzing soil liners. In the present study, an attempt has been made to estimate thickness of clay barriers for landfills for conservative/nonconservative contaminants. The optimum thickness is decided on the basis of the travel time taken by leachate as it moves down through the clay barrier. The one-dimensional (vertical) model is solved numerically by the Green element method and the developed model is first validated for transport of chlorides and dissolved organic carbon through a soil barrier at a landfill site. Later, an analysis is conducted taking a finite mass of the pollutant as the top boundary of the soil barrier and the maximum relative concentration of the contaminant determined, as it moves down. On the basis of these results, knowledge of the total mass of solid waste and the maximum concentration of the solute in the landfill, the minimum thickness of the liner for an equivalent leachate height, and Darcy velocity can be obtained from the design charts developed.