In the last few years microbial activities within the drinking water distribution network have gained more and more attention. Hygienic problems, harassment with odor and bad taste, and even material deterioration are the consequences of microbial life in the pipes. The growth of adhesive bacteria, so-called biofilms, seems to be the main reason for the problems mentioned above. Bacteria settling down as biofilm develop specific characteristics concerning persistence, increased metabolic activities, and sheltering opportunistic microbes. Moreover, biofilms are difficult to detect and to identify by conventional microbiological methods. In the distribution network of a German city biofilms were sampled and characterized by sensitive molecular biological and biochemical techniques. The correlation between different pipe materials and biofilm growth could be followed up over the time. The source and quality of the raw water influenced the population diversity as well as the metabolic activity of the biofilms. Opportunistic and pathogenic bacteria such as enterococci, mycobacteria, and legionellae were obviously sheltered and may persist within the biofilms, even though rarely. The specific characteristics of biofilms increased the tolerance to disinfection steps and initiated the microbial stress and repair responses. Besides that, a horizontal gene transfer between different biofilm bacteria has to be considered as potentially risky, especially with surface water as a raw water source. As a conclusion, monitoring of biofilms in distribution networks is technically as important as conventional hygienic control to avoid harassment and to manipulate inevitable biofilms to support good water quality.

A field demonstration of acetate mediated biologically active zone enhancement (BAZE) for in situ reductive transformation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in groundwater was conducted at the former Nebraska Ordnance Plant (NOP). The primary objectives of the field demonstration were to assess the potential of the BAZE process to remediate the RDX-contaminated groundwater, and to quantify the capital and operation/maintenance costs associated with the use of the BAZE process for in situ treatment of RDX contamination in groundwater. The study also delineated the effects of the BAZE process on subsurface biomass, and water quality parameters (metals mobilization, total organic compound, etc.). The results of this 20-month field study demonstrated that acetate is an excellent source of carbon capable of creating reduced conditions conducive for reductive transformation of RDX in groundwater. Over the period of demonstration, the background RDX concentration of about $256\mathrm{\mu }\mathrm{g}∕\mathrm{L}$ was reduced to below the U.S. EPA’s health advisory level of $2\mathrm{\mu }\mathrm{g}∕\mathrm{L}$ . Besides significant reduction in RDX background concentrations, other chemical (low $E_h$ and nitrate denitrification) and biological (biomass buildup and enrichment) changes in the subsurface validated the development of a biologically active zone after the amendment addition. A total of $\mathrm{2,250}\mathrm{kg}$ runway deicer ( $\sim \mathrm{1,493}\mathrm{kg}$ acetate) was injected into the subsurface over the period of the demonstration, which translates to a stoichiometric consumption of approximately $161\mathrm{g}$ acetate/g RDX. Approximately $\mathrm{36,200}{\mathrm{m}}^3$ of groundwater ( $\sim 9.27\mathrm{kg}$ RDX) were treated during the course of study at a unit cost of about $\$18.85∕{\mathrm{m}}^3$ groundwater treated ($73.70/g RDX destroyed).

A biocoagulant developed by the writers and called Bio-CoA was used to treat the turbid water in a bench-scale reactor as well as in a large pilot plant. The water quality after Bio-CoA treatment was compared to that treated by the traditional chemical coagulant, PACl. Although both Bio-CoA and PACl perform well in turbidity removal, Bio-CoA prevails over PACl since it removes suspended solids from turbid water with no changes in aluminum, $\mathrm{pH}$ , and conductivity of the effluent. In other words, Bio-CoA can be applied to drinking water treatment without any health concerns even under a high dosing condition. Meanwhile, with Bio-CoA application no alkali is required to neutralize the resulting low- $\mathrm{pH}$ water as is required for $\mathrm{PACl}$ , and the water after Bio-CoA treatment has a higher potential for extra pure water preparation and irrigation usage based on the lower conductivity of the effluent. Bio-CoA and the related treatment process can be used as a pretreament unit to reduce the turbidity of the superturbid water to a tolerable concentration for present drinking water treatment plants, which may overcome the water-offering deficiency during typhoon periods.

The influence of temperature on sorption and transport behavior of cadmium in three soils (sandy loam, loam, and clay loam) was studied with column and batch experiments. In the column experiments, nonequilibrium transport behavior was observed in breakthrough curves at 10 and $21°\mathrm{C}$ , whereas the transport behavior at $35°\mathrm{C}$ was in general agreement with the prediction of the equilibrium transport model. The durations of tailing were also reduced with increasing temperatures, indicating a lesser extent of nonequilibrium. The shift from nonequilibrium to equilibrium transport behavior with increasing temperature was probably promoted by the corresponding increase of sorption rate coefficient. The extent of increase in the sorption rate coefficient advocates intraparticle diffusion being the rate-limiting process. The retardation was found to increase with increasing temperature. This was likely because of the change of transport behavior and variation of surface chemical properties with temperature. Similar positive temperature dependence of sorption was revealed in the batch experiments. The recognition of nonequilibrium transport behavior at low temperature provides a better solute transport prediction and soil treatment design in cold regions.

Long-term impact of stabilized/solidified hazardous waste on the environment was evaluated using a combination of long-term leaching tests and mathematical modeling. The waste used in this research is a dust collected from filters used in the production of nickel-cadmium accumulators. It contains nickel hydroxide, cobalt hydroxide, and cadmium oxide, and based on toxicity characteristic leaching procedure test it is a hazardous waste. This waste was stabilized using two different aqueous anionic asphalt emulsions. Several extraction tests were used to evaluate the long-term leaching of stabilized waste. Then using a mathematical model, the long-term leaching test data was analyzed to obtain mass transport parameters for the contaminants in the stabilized wastes. From the leaching test results mathematical model parameters needed to estimate the transport and release of contaminants to the real environment under alkaline pH from the stabilized waste were obtained. The model simulation of the performance of the stabilized waste under the actual environmental conditions of the disposal site showed that there is insignificant release of the contaminants from the stabilized waste. Hence it was concluded based on the experimental and modeling data that if the environment is able to maintain an alkaline pH condition, then the stabilized waste will not damage the environment.

To meet the increasing demand for potable water, reuse and reclamation projects must be developed and implemented to augment water sources. The reuse of treated wastewater could provide a significant portion of the demand for clean water. Although there are many issues concerning the quality and safety of wastewater before it can be reused, the major technical concerns are how to deal with microbial and chemical contamination. Pathogenic organisms such as Cryptosporidium and Giardia pose a potential threat to public health. Cryptosporidium parvum oocysts can withstand many typical disinfection processes, particularly chlorine-based systems. Typically, the chlorine dose can be increased to eliminate the pathogens, but there is a trade-off in treatment strategies. Eliminating the biological contaminants with large doses of chlorine brings about the disinfectant by-product (DBP) problem, while minimizing the DBP formation requires reduced rates of chlorine, leading to a larger population of potentially dangerous microorganisms, e.g., Cryptosporidium and Giardia. The goal of this research was to assess ultrasonic technology for the treatment of wastewaters for possible reuse. As ultrasonic waves travel through a liquid medium, hydroxyl radicals/are produced $(\mathrm{O}\mathrm{H}\mathbf{\bullet })$ . $\mathrm{O}\mathrm{H}\mathbf{\bullet }$ is a powerful oxidation agent that can react with a wide spectrum of soluble organic chemicals and can also render bacteria and protozoan pathogens inactive. Additionally, the extreme temperatures and pressures, along with the shock wave caused during cavitation bubble collapse, can exert great forces on the pathogens and cause impairment. Various factors that may affect the efficiency of the inactivation of Cryptosporidium such as initial microbial density, pH, temperature, and energy intensity were assessed. It was demonstrated that the ultrasonic process is an effective disinfection technology.

Growth patterns of four different serovar of Bacillus thuringiensis (Bt) (Bt kurstaki, Bt israelensis, Bt tenebrionis, and Bt aizawai) were studied using wastewater sludge as a raw material. A comparative study using synthetic medium (soy) was also performed. It was observed that the four Bt strains gave cell counts of the order of ${10}^8\mathrm{CFU}∕\mathrm{mL}$ in wastewater sludge and ${10}^9\mathrm{CFU}∕\mathrm{mL}$ in synthetic medium. The sporulation (% spores) in two media was 90%. The entomotoxicity per unit spore (specific entomotoxicity) was much higher in sludge medium compared to synthetic medium. Therefore, sludge was a good source of nutrients for growth and toxin production by all types of serovar used in this study.