Batch study results may help utilities select appropriate chloramination conditions to limit DBP formation. Batch experiments were conducted on three diverse water sources to study the formation of dissolved organic halogen (DOX), trihalomethanes (THMs), haloacetic acids (HAAs), and cyanogen halides (CNX) during chloramination. The authors used preformed chloramines to examine the effect of pH, mass ratio of chlorine to ammonia–nitrogen (Cl2 to N), and bromide concentration on disinfection by‐product (DBP) formation. Formation of specific DBPs as well as the group parameter DOX was greatest at low pH and high Cl2‐to‐N ratios and followed the general trend of decreasing with increasing pH and decreasing Cl2‐to‐N ratio. Bromide addition increased the concentration of bromine‐substituted DBPs and DOX. These experiments demonstrated that because of dihaloacetic acid formation, HAA formation is more problematic during chloramination than THM formation. Because the specific DBPs measured in this research (THMs, six HAAs, and CNX) accounted for no more than 35 percent of the DOX concentration, utilities may want to consider both specific DBPs and DOX in selecting appropriate chloramination conditions.
Nitrification occurred in two covered finished‐water reservoirs in Southern California following a change from free chlorine to chloramine disinfection. The proliferation of autotrophic ammonia‐oxidizing bacteria was suspected to be the cause. Adverse water quality effects caused by the nitrification episodes included a rapid decline in the total chlorine and total ammonia‐nitrogen residuals and elevated levels of nitrite and heterotrophic plate count bacteria. As a result, the reservoirs were taken out of service and breakpoint‐chlorinated. This article examines the conditions leading to the development of nitrification in reservoirs containing chloraminated water, along with the measures that can be used to control the process.
Chlorinated disinfection byproducts (DBPs) generated from the reaction of the disinfectant chlorine with naturally occurring humic substances in raw water have been intensively studied over the past three decades, yet only a fraction of the total organic halogen (TOX) formed during chlorination has been chemically identified or even well characterized. The majority of the unknown portion of the TOX is likely attributable to high molecular weight (MW) DBPs (above 500), which may have potential adverse health effects. In this work, typically dosed chlorinated Suwannee River fulvic acid (SRFA) samples with and without coagulation pretreatment were separated and fractionated by using ultrafiltration (UF) and size exclusion chromatography (SEC) techniques. The SEC fractions corresponding to the high MW region were concentrated with nitrogen sparging and characterized by negative ion electrospray ionization mass spectrometry (ESI-MS) and ESI-MS/MS. The results demonstrate that the ESI-MS/MS precursor ion scan is an effective tool for the selective detection of the electrospray ionizable chlorine-containing compounds in a complex mixture. Many high MW chlorine-containing DBPs were tentatively found in the UF-SEC fractions of the chlorinated SRFA samples with/without coagulation pretreatment. The SEC-UV chromatograms and SEC-ESI-MS spectra show that coagulation could significantly reduce the formation of high MW chlorinated DBPs.
The objectives of this study were to investigate various distribution conditions that directly affect the production of tastes and odors, identify the chemical causes, and develop guidelines to help water utilities solve or prevent these types of problems. This paper presents four case studies of taste-and-odor problems generated in distribution systems. Two types of problems will be presented, (1) problems that occur in association with pipe or reservoir lining material leaching into the water and (2) problems that are caused by a continuation of chemical reactions in the water within the distribution system. The sensory method used was flavor profile analysis (FPA) and the chemical methods were closed loop stripping analysis (CLSA) or liquid-liquid extraction (LLE) coupled with gas chromatography/mass spectrometry (GC/MS). Bromophenols and bromodichloroiodomethanes were found to be the cause of the medicinal odors, while alkyl benzenes and naphthalene were found to be associated with the oil-base paint type of odors.
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