Sadahiko Itoh

Use of chlorophyll fluorescence of Closterium ehrenbergii and Lemna gibba for toxic effect evaluation of sewage treatment plant effluent and its hydrophobic components

In this study fluorometric methods using an alga, Closterium ehrenbergii, and a higher plant, Lemna gibba, were employed to evaluate the toxicity of sewage treatment plant (STP) effluent and its hydrophobic components. Fluorescence parameters such as the operational photosystem II quantum yield at steady state of electron transport, the nonphotochemical quenching, and the complementary area were modified in the presence of hydrophobic components, particularly with C. ehrenbergii. It was found that C. ehrenbergii was a suitable species to be used in a hydrophobic components bioassay, since this alga was 400 times more sensitive than L. gibba to hydrophobic components. Results indicate that hydrophobic STP effluent components are less toxic as a constituent of the STP effluent than when they are extracted from the effluent. We also demonstrated here that in addition to the growth inhibition test, fluorometric methods can be usefully employed in bioassays for the toxic effect evaluation of pollutants present in municipal wastewater treatment plant effluents.

Contributions of disinfection by-products to activity inducing chromosomal aberrations of drinking water

The relationships between activity inducing chromosomal aberrations of waters treated with disinfectants and by-products were investigated by focusing on nitro and carbonyl groups, respectively. The contribution of the carbonyl group to activity inducing aberrations of treated waters was found to be large. On the other hand, the contribution of the nitro group was small. In the case of chlorinated water, organochlorine compounds contribute to activity inducing aberrations in addition to carbonyl group. The carbonyl group could be useful as a coarse indicator to compare activity inducing aberrations among waters treated with chlorine dioxide, chloramine, and ozone. Activity inducing aberrations of chlorinated water including the same amount of carbonyl group was demonstrated to reach approximately 10 times those of waters treated with three other disinfectants.

Revising the existing Performance Indicator system for small water supply utilities in Japan

97.5% of the water utilities in Japan serve less than 50,000 customers, and are called small water utilities. The Performance Indicator system in Japan, used to evaluate the performance of various aspects of the supply system, currently has 137 items, which are too many in number for the small utilities to adopt because of resource and financial constraints. The objective of this study is to, thus, revise the existing PI system to arrive at a reduced, relevant and practical structure that provides enough information to rationally evaluate small water supply systems in Japan. Principal Component Analysis was used to reduce the dimensionality of the original data. The results suggest that only nine components, consisting of 33 items (called 9-cPIS), are sufficient for evaluating the small water utilities. The effectiveness of the 9-cPIS in benchmarking, evaluating business models, and the planning and management of the water utilities has been discussed further.

A survey on levels and seasonal changes of assimilable organic carbon (AOC) and its precursors in drinking water

In Japan, customers’ concerns about chlorinous odour in drinking water have been increasing. One promising approach for reducing chlorinous odour is the minimization of residual chlorine in water distribution, which requires stricter control of organics to maintain biological stability in water supply systems. In this investigation, the levels and seasonal changes of assimilable organic carbon (AOC) and its precursors in drinking water were surveyed to accumulate information on organics in terms of biological stability. In tap water samples purified through rapid sand filtration processes, the average AOC concentration was 174 µgC/L in winter and 60 µgC/L in summer. This difference seemed to reflect the seasonal changes of AOC in the natural aquatic environment. On the other hand, very little or no AOC could be removed after use of an ozonation–biological activated carbon (BAC) process. Especially in winter, waterworks should pay attention to BAC operating conditions to improve AOC removal. The storage of BAC effluent with residual chlorine at 0.05–0.15 mgCl2/L increased AOC drastically. This result indicated the possibility that abundant AOC precursors remaining in the finished water could contribute to newly AOC formation during water distribution with minimized residual chlorine. Combined amino acids, which remained at roughly equivalent to AOC in finished water, were identified as major AOC precursors. Prior to minimization of residual chlorine, enhancement of the removal abilities for both AOC and its precursors would be necessary.

Effect of operating conditions in soil aquifer treatment on the removals of pharmaceuticals and personal care products.

Soil aquifer treatment (SAT) is an alternative advanced treatment for wastewater reclamation, and it has the potential to control micropollutants including pharmaceuticals and personal care products (PPCPs). However, the relationship of operating conditions in SAT and removals of micropollutants was not clear. In this study, the effects of operating conditions on the removals of PPCPs were evaluated by using lab-scale columns and plant pilot-scale reactors under different operating conditions. Firstly, weathered granite soil (WGS), standard sand (SAND) and Toyoura standard sand (TS) have different soil characteristics such as total organic carbon (TOC) and cation exchange capacity (CEC). In the columns with these packing materials, the removals of carboxylic analgesics and antilipidemics were effective regardless packing materials. The removals of antibiotics were more effective in WGS than in TS and SAND, indicating high TOC and CEC enhance the sorption in SAT. Secondly, with the extension of hydraulic retention time (HRT), the removals of sulfamethoxazole, acetaminophen, crotamiton, and antipyrine were improved in WGS columns, and adaptable biodegradation for moderately removable PPCPs was formed. Thirdly, the removal efficiencies of sulfamethoxazole and crotamiton were higher in the WGS column under vadose condition than in the WGS column under saturated condition, because of aerobic condition in WGS column under vadose condition. Though long HRT and vadose condition had positive influence on the removals of several PPCPs such as sulfamethoxazole, WGS column with an HRT of 7days under saturated condition removed most PPCPs.

Inflammatory responses and potencies of various lipopolysaccharides from bacteria and cyanobacteria in aquatic environments and water supply systems

Inflammatory substances derived from indigenous bacteria in aquatic environments or water systems are of great concern. Lipopolysaccharides (LPSs), one of the major inflammatory substances in water, are usually identified using Limurus amoebocyte lysate (LAL) assay on the basis of their endotoxic activity, but endotoxin levels do not accurately represent their inflammatory potency in humans. In this investigation, the cellular endotoxin contents of pure-cultured bacteria/cyanobacteria, which are frequently detected in water sources and distribution systems, and of indigenous bacteria in a river and in biologically activated carbon (BAC) effluent, were investigated. The indigenous bacteria showed the highest endotoxin contents exceeding 10(-3)EU/cell. The LPSs were then purified from those samples, and their inflammatory potencies were examined using a human monocytic cell line. The LPSs from Acinetobacter lwoffii culture, the river water, and the BAC effluent sample revealed a unique cytokine secretion pattern; they induced both IL-8 and TNF-α more strongly than the other tested bacterial LPSs. These results suggest that natural bacterial/cyanobacterial flora in aquatic environments and water distribution systems have the potential to induce relatively strong inflammatory responses in humans; therefore, further accumulation of data on water quality from the perspective of not just endotoxins but inflammatory potency is needed.

Simultaneous Control of Bromate Ion and Chlorinous Odor in Drinking Water Using an Advanced Oxidation Process (O3/H2O2)

Simultaneous control of chlorinous odor and bromate ion formation was attempted by using an advanced oxidation process (AOP, O3/H2O2). Also, the relationship between trichloramine (NCl3, a suspected odor compound in drinking water) and chlorinous odor in drinking water was studied through a headspace GC-MS analysis and the triangle sensory test. Odor strength after chlorination decreased by more than 50% for the samples pretreated with conventional ozonation and AOP. The change of hydroxyl radical exposure (•OH-ct) when AOP was applied did not show the clear difference in terms of the removal of chlorinous odor compared with conventional ozonation, but AOP was better for the control of bromate ion. Trichloramine seemed not to be a major odor compound in the chlorinated water of this experiment. The change of ammonium ion, bromide ion, and ozone dose did not clearly affect the efficiency of odor removal.

Changes of activity inducing chromosomal aberrations and transformations of chlorinated humic acid.

The change of the toxicity of chlorinated water after chlorine injection was examined. For the measurement of toxicity, chromosomal aberration test and transforming test were carried out as indexes to initiating activity and to promoting activity in the carcinogenesis process, respectively. Activity inducing chromosomal aberrations of chlorinated humic acid gradually decreased with time after chlorination. In contrast, activity inducing transformations measured by the two-stage assay gradually increased. Thus, the toxicity that decreases or increases is present in chlorinated water. Furthermore, activity inducing transformations measured by the non-two-stage assay gradually decreased. This direction of change was reverse to that of activity inducing transformations by the two-stage assay and consistent with that of activity inducing chromosomal aberrations. It is speculated that the main reason of decreasing activity inducing transformations by the non-two-stage assay is because initiating activity detected as activity inducing chromosomal aberrations in chlorinated water decreases drastically. Directions of changes of total organic halogen and carbonyl group were qualitatively consistent with that of activity inducing chromosomal aberrations. Directions of changes of chloroform and dichloroacetic acid were qualitatively consistent with that of activity inducing transformations by the two-stage assay. Findings of this study suggest that further research is necessary to compare carcinogenicity of tap water near water purification plant and distant tap water.

Comparison of inflammatory responses in human cells caused by lipopolysaccharides from Escherichia coli and from indigenous bacteria in aquatic environment.

The endotoxic activities of lipopolysaccharides (LPSs) in water samples are usually determined using a Limulus amoebocyte lysate (LAL) assay, but it is known that the determined activities do not always represent their inflammatory potency in humans. In this investigation, the inflammatory responses in three different human cells stimulated with Escherichia coli LPS, keratinocyte, CD14+ monocyte, and THP-1, were compared using cytokine secretion as biomarkers to develop novel in vitro assay systems for detecting changes in inflammatory potencies of endotoxins in aquatic environment. Only THP-1 with 6-h stimulation showed dose-dependent responses in the range of normal endotoxin levels in aquatic environment. Then, the inflammatory potency of environmental LPS, which was purified from river water, was tested using THP-1. The levels and patterns of cytokine secretion after the environmental LPS stimulation were completely different from E. coli LPS. Interleukin 8 (IL-8) secretions after the environmental LPS stimulation were approximately 10-fold higher than those after E. coli LPS stimulation. The environmental LPS also induced much higher levels of TNF-α secretions in THP-1. These results suggest that a diversity of LPS structures in aquatic environment could contribute to stronger and different inflammatory responses. This investigation indicated that the proposed THP-1 assay system could be useful for detecting the changes in inflammatory potencies caused by aquatic bacteria.

Relative source allocation of TDI to drinking water for derivation of a criterion for chloroform: A Monte-Carlo and multi-exposure assessment

Drinking water quality standard (DWQS) criteria for chemicals for which there is a threshold for toxicity are derived by allocating a fraction of tolerable daily intake (TDI) to exposure from drinking water. We conducted physiologically based pharmacokinetic model simulations for chloroform and have proposed an equation for total oral-equivalent potential intake via three routes (oral ingestion, inhalation, and dermal exposures), the biologically effective doses of which were converted to oral-equivalent potential intakes. The probability distributions of total oral-equivalent potential intake in Japanese people were estimated by Monte Carlo simulations. Even when the chloroform concentration in drinking water equaled the current DWQS criterion, there was sufficient margin between the intake and the TDI: the probability that the intake exceeded TDI was below 0.1%. If a criterion that the 95th percentile estimate equals the TDI is regarded as both providing protection to highly exposed persons and leaving a reasonable margin of exposure relative to the TDI, then the chloroform drinking water criterion could be a concentration of 0.11mg/L. This implies a daily intake equal to 34% of the TDI allocated to the oral intake (2L/d) of drinking water for typical adults. For the highly exposed persons, inhalation exposure via evaporation from water contributed 53% of the total intake, whereas dermal absorption contributed only 3%.