I.H. Suffet

Binding of DDT to dissolved humic materials

Quantitative measurements have been made by using equilibrium dialysis techniques on the extent of binding between DDT and dissolved humic materials. A significant fraction of the dissolved DDT found in natural waters may be bound to dissolved humic materials. The extent of binding depends on the source of the humic material, the pH, the calcium concentration, the ionic strength, and the concentration of humic materials.

Monitoring techniques for odour abatement assessment

Odorous emissions from sewers and wastewater treatment plants are a complex mixture of volatile chemicals that can cause annoyance to local populations, resulting in complaints to wastewater operators. Due to the variability in hedonic tone and chemical character of odorous emissions, no analytical technique can be applied universally for the assessment of odour abatement performance. Recent developments in analytical methodologies, specifically gas chromatography, odour assessment approaches (odour wheels, the odour profile method and dynamic olfactometry), and more recently combined gas chromatography-sensory analysis, have contributed to improvements in our ability to assesses odorous emissions in terms of odorant concentration and composition. This review collates existing knowledge with the aim of providing new insight into the effectiveness of sensorial and characterisation approaches to improve our understanding of the fate of odorous emissions during odour abatement. While research in non-specific sensor array (e-nose) technology has resulted in progress in the field of continuous odour monitoring, more successful long term case-studies are still needed to overcome the early overoptimistic performance expectations. Knowledge gaps still remain with regards to the decomposition of thermally unstable volatile compounds (especially sulfur compounds), the inability to predict synergistic, antagonistic, or additive interactions among odorants in combined chemical/sensorial analysis techniques, and the long term stability of chemical sensors due to sensor drift, aging, temperature/relative humidity effects, and temporal variations. Future odour abatement monitoring will require the identification of key odorants to facilitate improved process selection, design and management.

Evaluation of granular activated carbons for removal of methylisoborneol to below odor threshold concentration in drinking water

Abstract Four granular activated carbons manufactured from different raw materials were evaluated for the removal of 2-methylisoborneol (MIB) to below odor threshold concentration using equilibrium isotherm tests. MIB adsorption isotherms were compared in the aqueous equilibrium concentration range 400 daltons) contributed to changes in isotherms and to the reduction of MIB adsorption capacity. A database of organic pure water isotherms with MIB would be of important value to water facilities requiring T&O control as it provides a reliable starting point for GAC product selection. However, field or pilot tests are still needed for the final selection owing to the varying characteristics of individual water source.

Electrochemical removal of bromide and reduction of THM formation potential in drinking water

Trihalomethanes (THMs), a by-product of the chlorination of natural waters containing dissolved organic carbon and bromide, are the focus of considerable public health concern and regulation due to their potential as a carcinogen by ingestion. This paper presents a promising new water treatment process that lowers the concentration of bromide in drinking water and thus, lowers the THM formation potential. Bromide is oxidized by electrolysis to bromine and then the bromine apparently volatilized. The electrolyzed water, when chlorinated, produces measurably lower amounts of THMs and proportionately fewer brominated THMs, which are of greater public health concern than the chlorinated THMs. Removing bromide should also reduce the formation of other disinfection by-products such as bromate and haloacetic acids.

Quantitative structure-activity relationship using molecular connectivity for the activated carbon adsorption of organic chemicals in water

Quantitative structure-activity relationships (QSARs) for estimating the adsorption of organic chemicals on activated carbon were developed using molecular connectivity. The QSARs were based on adsorption data for 363 chemicals [expressed as (X/C)min] obtained from six literature sources, representing a wide range of aromatic and aliphatic chemical classes. In order to test the predictive capabilities of the QSAR equations and to illustrate their use, the QSARs were applied to data from three additional data sources. The existence of divergent literature values for the same chemicals was addressed in one QSAR by a “dummy variable” to identify the data source. The resulting QSARs are well suited for use in the water treatment industry because they are based on a wide range of chemicals, use readily calculated parameters, and represent adsorption at low adsorbate concentrations. However, in applying QSARs based on literature data, it is imperative to consider the relevance of the data source to ones own investigative situation.

Distribution-generated taste-and-odor phenomena

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.

Identification of 1,1,1-trichloroacetone (1,1,1-trichloropropanone) in two drinking waters: a known precursor in haloform reaction

1,1,1Trichloroacetone (1 ,I, 1 -trichloropropanone) , a known precursor in the haloform reaction, was isolated from the drinking water of two different river water supplies. An on-line XAD-2 macroreticular resin and a continuous liquid-liquid extractor were used as isolating techniques. The water was adjusted to near pH 4 before it was passed through the XAD-2 resin. GC/MS confirmation of the analysis is presented when free chlorination and/or ammoniation at two water supplies were practiced.

Growth of estuarine fish is associated with the combined concentration of sediment contaminants and shows no adaptation or acclimation to past conditions

We tested whether the growth rates of small benthic fish (Gillichthys mirabilis) in three southern California estuaries corresponded with the local concentrations of contaminants. Fish originating from each estuary were transplanted to cages in each estuary in two reciprocal transplant experiments. The growth rates of caged fish, and the size-distribution of natural populations, showed the same pattern of difference among estuaries. Twelve metals and organic contaminants occurred in bulk sediments at concentrations close to their individual ERL values, and a simple index of their combined concentration (the mean ERL quotient) was inversely correlated to the growth of caged fish. Metals in the water column occurred at lower concentrations, relative to toxicity thresholds, than those in sediments and were unrelated to fish growth. Fish used in the field caging experiments, and other fish held in the laboratory under constant conditions, showed no difference in growth according to their estuary of origin. Fish originating from different estuaries also showed no consistent differences in their tissue burden of organic contaminants. Our results thus suggested no genetic adaptation or physiological acclimation to the past contaminant regime, but revealed a possible association between fish growth rates and the combined concentration of multiple sediment contaminants.

Ultrafiltration separation of aquatic natural organic matter: Chemical probes for quality assurance

Characterization of molecular size of natural organic matter (NOM) is a valuable tool when assessing its effect on the performance of water treatment systems as well as its geochemical origin. Size fractionation can be accomplished by ultrafiltration (UF). Unfortunately, membrane manufacturing generates a range of pore sizes. Many membrane manufacturers use molecular weight cutoff (MWCO) metric based on a 90% retention of given solute after specified duration of filtration. The objective of this study was to characterize the ability of different commercially available UF membranes to separate different size fractions of NOM. The UF membranes characterized were YM (regenerated cellulose, negatively charged) and PB (polyethersulfone, negatively charged) product lines by Millipore. The probes used to represent the size, shape and charge of NOM were polymers (polyethylene glycols (PEGs), dextrans, polystyrene sulfonates (PSSs)), dyes (bromocresol green, congo red, methyl red, methyl orange) and biological molecules (vitamin B-12 and bacitracin). The results show that MWCO definition does not hold for membranes of 5kDa and 10kDa pore openings using most polymers and dyes. The MWCO definition holds for 1kDa membrane for all tested probes. Under natural water conditions PSSs assume random coil configurations that are nearly identical to Suwannee fulvic acid. The results show that PSS agrees with stated MWCOs. The study demonstrates that ultrafiltration is not a simple mechanical sieving process, but that charges on the membrane and the constituent play a significant role in the rejection process. Effective probe size was increased seven- to fourteen-fold by charge interactions between the negative probes and negatively charged membrane. Uncharged molecules larger than specified MWCOs are able to pass through pores (PEGs), while small charged molecules (dyes) do not pass. For probes with low or neutral charges, shape becomes an important factor, with globular being favored over linear structure. Thus, MWCOs cannot be trusted for purposes of NOM size characterization. The study recommends the use of YM 1K, PB 5K and YM 10kDa membranes for comparative-only NOM size ultrafiltration characterization within the 1-10kDa size range.

Off-site forensic determination of airborne elemental emissions by multi-media analysis: a case study at two secondary lead smelters.

A study is presented of multi-element multi-media airborne emissions via analysis of solids, soils, wipes, and glass fiber filters on and around two secondary lead smelters. Characteristic ratios of lead :antimony :arsenic were found in all of these media along with a correlated presence of cadmium and silver. The further the medium was from the plant, the less of all of these elements found while the ratio was maintained. Media downwind had higher concentrations than upwind in other directions. Conclusive forensic evidence was accumulated as to the origin and route of emission of the elements.