Factors controlling nitrosamine formation during wastewater chlorination

Recent discoveries of the formation of low levels of the potent carcinogen N-nitrosodimethylamine (NDMA) during wastewater chlorination has caused concern where indirect potable water reuse is practiced. Experiments indicate that nitrosamine formation during chlorination of wastewater is consistent with a reaction scheme involving the slow formation of a hydrazine intermediate from a secondary amine and monochloramine, followed by its rapid oxidation to the corresponding N-nitrosamine. A survey of precursors indicates that secondary amines form their corresponding N-nitrosamines to the greatest extent. However, molecules containing the secondary amine as a functional group can also form the corresponding N-nitrosamine. NDMA is the predominant N-nitrosamine found in chlorinated wastewater. However, other nitrosamines are detected. These N-nitrosamines may be important if the summed risk posed by the exposure to all N-nitrosamines is considered.</jats:p

Attenuation of Wastewater-Derived Contaminants in an Effluent-Dominated River

TextTo assess attenuation rates under conditions encountered in such systems, samples from the Trinity River were analyzed for a suite of wastewater-derived contaminants during a period when wastewater effluent accounted for nearly the entire flow of the river over a travel time of approximately 2 weeks. Results of this study indicate that natural attenuation can result in significant decreases in concentrations of wastewater-derived contaminants in large rivers.Univ. of California Dept. of Civil and Env. Engr.Center for Research in Water Resource

Dissolution of mesoporous silica supports in aqueous solutions: Implications for mesoporous silica-based water treatment processes

Under pH 7-10 conditions, the mesoporous silica supports proposed for use in water treatment are relatively unstable. In batch experiments conducted in pH 7 solutions, the commonly used support SBA-15 dissolved quickly, releasing approximately 30mg/L of dissolved silica after 2h. In column experiments, more than 45% of an initial mass of 0.25g SBA-15 dissolved within 2 days when a pH 8.5 solution flowed through the column. In a mixed iron oxide/SBA-15 system, the dissolution of SBA-15 changed the iron oxide reactivity toward H 2O 2 decomposition, because dissolved silica deposited on iron oxide surface and changed its catalytic active sites. As with SBA-15, other mesoporous silica materials including HMS, MCM-41, four types of functionalized SBA-15, and two types of metal oxide-containing SBA-15 also dissolved under circumneutral pH solutions. The dissolution of mesoporous silica materials raises questions about their use under neutral and alkaline pH in aqueous solutions, because silica dissolution might compromise the behavior of the material

Local perspectives on water

No abstract available

Police posing as juveniles online to catch sex offenders: Is it working?

Abstract This paper explores the extent and effectiveness of proactive investigations in which investigators pose as minors on the Internet to catch potential sex offenders. It utilizes a subsample of cases from the National Juvenile Online Victimization Survey, which concerned persons arrested for Internet sex crimes against minors in the year beginning July 1, 2000. Results suggest proactive investigations represented a significant proportion (25%) of all arrests for Internet sex crimes against minors. Such investigations were being conducted at all levels of law enforcement. The online personas assumed by investigators paralleled the ages and genders of real youth victimized in sex crimes that started as online encounters. These proactive investigations accessed an offender group that appeared somewhat less deviant in terms of adult sexual behavior and arrest history but equally deviant as other online offenders in terms of possession of child pornography. Prosecution of these cases produced high rates of guilty pleas and low rates of dismissed or dropped cases. The entrapment, fantasy or role-playing, and factual impossibility defenses were used but not successfully. Findings suggest that the Internet sometimes allows law enforcement to interdict before a youth is victimized, gather solid evidence of offenses, and find and track some offenders