Reactions of chlorine with inorganic and organic compounds during water treatment—Kinetics and mechanisms: A critical review

Formation of N-nitrosodimethylamine (NDMA) from reaction of monochloramine: a new disinfection by-product

Partition coefficients for the binding affinities of pyrene, fluoranthene, and anthracene to 26 different humic materials were determined by fluorescence quenching. Sources included isolated humic acids, fulvic acids, and combined humic and fulvic fractions from soil, peat, and freshwater as well as Aldrich humic acid. Each of the humic materials was characterized by elemental composition, ultraviolet absorbance at 280 nm, molecular weight, and for 19 samples, composition of main structural fragments determined by 13C solution-state NMR. The magnitude of the Koc values correlated strongly with the independent descriptors of aromaticity of humic materials, including atomic H/C ratio, absorptivity at 280 nm, and three interdependent 13C NMR descriptors (CAr-H,R, ΣCAr, ΣCAr/ΣCAlk). Statistical comparison of humic sources grouped by the origin revealed that binding affinities were best predicted by the 13C NMR descriptors, with a slight prevalence of ΣCAr/ΣCAlk ratio, while molecular weight was the poorest pr...

Relationships between structure and binding affinity of humic substances for polycyclic aromatic hydrocarbons: relevance of molecular descriptors

Reaction of aromatic compounds with hydroxyl radical is inhibited by dissolved natural organic matter (NOM). The degree of inhibition is significantly greater than that expected based on a simple model in which aromatic compound molecules bound to NOM are considered to be unreactive. In this study, hydroxyl radical was produced at steady-state concentrations using Fenton chemistry (H2O2 + Fe2+ → Fe3+ + HO- + HO·). Suwannee River fulvic acid and humic acid were used as NOM. The most likely mechanism for the observed inhibition is that hydroxyl radical formation occurs in microenvironmental sites remote from the aromatic compounds. In addition to changes in kinetics, pyrene hydroxyl radical reaction also exhibited a mechanistic change in the presence of fulvic acid. The mechanism changed from a reaction that was apparently first-order in pyrene to one that was apparently second-order in pyrene, indicating that pyrene self-reaction may have become the dominant mechanism in the presence of fulvic acid. Dissol...

Inhibition of hydroxyl radical reaction with aromatics by dissolved natural organic matter

The effects of colloids on the transport of two strongly sorbing solutesa hydrophobic organic compound, phenanthrene, and a metal ion, Ni2+were studied in sand-packed laboratory columns under different pH and ionic strength conditions. Two types of column experiments were performed as follows:  (i) sorption/mobilization experiments where the contaminant was first sorbed in the column under conditions where no colloids were released and mobilized under conditions where colloids were released as a result of ionic strength reduction in the influent; and (ii) transport experiments where the contaminant, dissolved or sorbed on colloids, was injected into columns packed with a strongly sorbing porous medium. In the first type of experiment, contaminant mobilization was significant only when all releasable colloids were flushed from the column. In all other cases, although high colloid particle concentrations were encountered, there was no marked effect on total contaminant concentrations. In the second type of ...

Chemical factors influencing colloid-facilitated transport of contaminants in porous media

A kinetic model for chlorine transfer in the aqueous chlorine/ammonia/organic nitrogen system was constructed and used to explain the distribution of the chlorine species over time. Observed second-order rate constants for chlorine transfer from organic chloramines to ammonia were found to be 3.84×10 -2 M -1 s -1 for N - chloroglycine, 1.55×10 -2 M -1 s -1 for N-chloroglycylglycine, and 5.85×10 -3 M -1 s -1 for N-chloromethylamine (pH 6.8). Chlorine transfer from organic chloramines to ammonia was found to be significant under simulated conditions of wastewater disinfection

Distribution of aqueous chlorine with nitrogenous compounds: chlorine transfer from organic chloramines to ammonia

The primary disinfectant in wastewater treatment is inorganic monochloramine, formed from the reaction of added chlorine with ammonia. Laboratory studies have shown that monochloramine can transfer chlorine to nitrogenous organics, producing organic chloramines that are weak disinfectants. Thus, chlorine transfer from monochloramine may result in poorer disinfection. In this study, chlorine transfer from monochloramine was observed in 4 of 10 samples collected from four wastewater treatment facilities. Chlorine acceptors in these wastewaters reacted with monochloramine about as fast as amino acids and peptides reacted with monochloramine. The monochloramine concentration was reduced by one-half in approximately 10 to 70 minutes. Evidence was found for negative interferences in the measurement of total residual chlorine (TRC) by amperometric titration. A rapid spectrophotometric method was developed to measure TRC more precisely.

Jeyong Yoon

Papers

Distribution of aqueous chlorine with nitrogenous compounds: chlorine transfer from organic chloramines to ammonia

Chlorine transfer from inorganic monochloramine in chlorinated wastewater