In an effort to better control formation of disinfection by‐products (DBPs), the US Environmental Protection Agency's recently promulgated Disinfectants/DBP Rule requires that US surface water treatment plants whose influent and effluent waters meet certain criteria practice enhanced coagulation. Although this treatment technique has been shown to effectively reduce natural organic matter, and consequently DBPs, questions have been raised concerning its effect on other aspects of water treatment such as particle and pathogen removal. The current study was designed to investigate the influence of decreased coagulation pH levels (an integral component of enhanced coagulation) on removal of Cryptosporidium oocysts as well as on reduction of total organic carbon (TOC), turbidity, and particle counts. A series of pilot‐plant trials was conducted in which commonly used coagulants (ferric chloride, alum, and polyaluminum chloride) were used at various pH levels to treat river water spiked with large numbers of Cryptosporidium oocysts. The results showed that TOC removal is significantly enhanced by coagulation at lower pH levels and that all three coagulants are effective in removing Cryptosporidium oocysts during conventional treatment (mean removal = 4.3 log units). However, turbidity and particle counts appear to be unreliable indicators of oocyst removal. Finally, the investigation suggested that lowering coagulation pH does not interfere with removal of Cryptosporidium. However, questions remain concerning the use of alum at pH 5.

A summary of our recent publications describing water-soluble imidazole containing polymers is presented. Copoly[1-alkyl-4-or 5-vinylimidazole/4(5)-vinylimidazole] (I), copoly[vinylamine/4(5)-vinylimidazole] (II), and dodecane-block-poly[ethylenimine-graft-4(5)-methylimidazole] (III) have been used to investigate the hydrophobic interaction in esterolytic reactions. A brief survey of related work is presented along with our current work.Several reviews have been published describing our work on imidazole catalysis.(1-4) Other investigators in this field have published comprehensive review articles comparing synthetic catalysts to enzymes.(5-9) The esterolytic activity of the three catalyst systems reviewed in this paper have been compared to poly[4(5)-vinylimidazole] (PVIm) in 28.5% ethanol-water solutions since PVIm is not soluble in water. However, within each system, minor changes in catalyst apolarity illustrate the effect of hydrophobic interactions on the rate of esterolysis. The substrates consisted of a series of neutral p-nitrophenyl esters (Sn) and negatively charged 4-acyloxy-3-nitrobenzoic acids (Sn -), where n denotes the number of carbons in the acyl chain. I

In the previous paper, some ω‐(1‐imidazolyl) and ω‐[4(5)‐imidazolyl]alkanoic acids were synthesized and grafted onto poly(vinylamine). These water soluble catalysts of varying apolarity contain both hydrophobic and electrostatic binding sites for neutral and charged substrates. The influence of side chain length, percent graft, and the substitution in the imidazole ring are described. The grafts possessing the longer side chains and lesser apolar weight were more efficient catalysts than the grafts containing numerous short side chains and greater apolar weight. These grafts exhibited slower rates than poly[4(5)‐vinylimidazole].

Some ω‐(1‐imidazolyl) and ω‐[4(5)‐imidazolyl]alkanoic acids were synthesized and grafted onto poly(vinylamine) with an amide bond. These water‐soluble grafts were used to study the kinetics of the esterolysis of activated phenyl esters. The 1‐substituted imidazoles were prepared by the reaction of the sodium salt of imidazole with the ethyl ω‐bromoalkanoates. The 4(5)‐substituted imidazoles were prepared from urocanic acid or 4(5)‐hydroxymethylimidazole. The ω‐(1‐imidazolyl)alkanoic acids were grafted onto poly(vinylamine) via their acyl–guanidine derivatives; the 3‐[4(5)‐imidazolyl]propanoic acid was grafted with a water‐soluble carbodiimide.

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