Recovery of coagulant from water supply plant sludge and its effect on clarification

Spent coagulant in water supply plant sludge was extracted with H₂SO₄ and the efficiency of the reused coagulant was studied. The optimum pH values for coagulant extraction and clarification with the reused coagulant were 3.0–4.0 and about 6, respectively. In treating raw influent obtained from a sewage treatment plant and wastewater from a coastal landfill site, the removal of chemical oxygen demand (COD), total nitrogen, and total phosphorous with the recovered coagulant was higher than that with commercial aluminum sulfate or polyaluminum chloride. In addition, the sludge settling properties, the extra sludge mass formation, the supernatant quality, and the cost of reagents were also studied. The coagulant recovered from water supply plant sludge by H₂SO₄ extraction could be successfully reused for the clarification of domestic and food industry wastewaters.     

Report on hazardous household waste generation in Japan.

Surveys of over 2000 households in Japan were conducted to investigate the characteristics of hazardous household waste (HHW) generation. In Japan, about 2.5 to 4.3 kg of HHW are produced per tonne of the residential waste stream. The percentage of used batteries in HHW was over 50%. Every household using spray (aerosol) cans had more than seven cans on average. The generation of HHW, in terms of both quantities and type of waste produced, appeared to vary with dwelling type. Detached dwelling residents tended to store HHW such as used batteries, whereas apartment residents tended not to store waste. The amounts of discarded HHW were larger at the end of the year in comparison with other months. The data accumulated were used to estimate the quantities of HHW disposed off annually, and the quantities and type of waste that might be received by a typical depot collection programme in Japan.     

Evaluation of the effect of automotive bumper recycling by life-cycle inventory analysis

This paper describes a case study of the application of life-cycle inventory analysis to automotive bumper recycling. Two scenarios of bumper recycling are compared. One is “bumper-to-bumper recycling,” in which we recycle bumpers into more bumpers. The other is “cascade recycling,” in which bumpers are recycled into different parts of a car with a lower function. Inventory analysis is applied to both these recycling scenarios by analyzing the stages of acquiring natural resources, manufacturing materials, and parts, disposal, and recycling. We chose air emission, solid waste, and fossil fuel resources as items of the inventory analysis. We quantified the effect of reductions in the environmental load by recycling bumpers, and found that reductions in the environmental load were larger with cascade recycling than with bumper-to-bumper recycling based on current conditions. Received: February 2, 2000 / Accepted: April 21, 2000     

Photocatalytic mineralization of hydroperfluorocarboxylic acids with heteropolyacid H₄SiW₁₂O₄₀ in water

The decomposition of hydroperfluorocarboxylic acids [H-PFCAs; HC_nF_2nCOOH (n = 4 and 6)] induced by heteropolyacid photocatalyst H₄SiW₁₂O₄₀ in water was investigated, and the results are compared with the results for the corresponding perfluorocarboxylic acids (PFCAs; C_nF_2n+1COOH). This is the first report on the photochemical decomposition of H-PFCAs, which are being developed as alternative surfactants to environmentally persistent and bioaccumulative PFCAs. H-PFCAs were not decomposed by irradiation with UV-Visible light (>290 nm) in the absence of H₄SiW₁₂O₄₀. In contrast, UV-Visible light irradiation of H-PFCAs in the presence of H₄SiW₁₂O₄₀ efficiently decomposed H-PFCAs to F⁻ and CO₂. The decomposition reactions showed pseudo-first-order kinetics, and the decomposition rate constants were 1.8-2.5 times higher than those for the corresponding PFCAs. The reaction mechanism can be explained by elimination of H⁺ from the ω-H atom of the H-PFCAs by the excited catalyst, followed by formation of perfluorodicarboxylic acids.     

Effect of polyethylene addition to coal on hydrogasification enhancement

Hydrogasification of a coal/polyethylene mixture was carried out using a low concentration of polyethylene in the samples with the aim of industrial application. Coal/polyethylene mixtures in the ratio of 90:10 and 75:25 were used in this study. A hydrogasification experiment was conducted using a unique batch reactor at 1073 K under a 7.1 MPa hydrogen atmosphere. The reaction time varied from 1 to 80 s. The results revealed a methane yield from the mixtures that was noticeably greater than the values calculated from experimental results obtained from coal and polyethylene respectively, assuming no mutual influences. A significant synergistic effect was observed even when the polyethylene content was as low as 10 %. It is suggested that there might be an advantage in hydrogasification processes if waste plastics are mixed with coal, such content being practically assumed.     

Negatively-charged air conditions and responses of the human psycho-neuro-endocrino-immune network

BACKGROUND: Against increasing environmental adverse effects on human health such as those associated with water and ground pollution, as well as out- and indoor air conditions, trials were conducted to support and promote human health by improving the indoor air atmosphere. This study was performed to estimate the effect of negatively-charged air conditions on human biological markers related to the psycho-neuro-endocrino-immune (PNEI) network. OBJECTIVES: After construction of negatively-charged experimental rooms (NCRs), healthy volunteers were admitted to these rooms and control rooms (CTRs) and various biological responses were analyzed. METHODS: NCRs were constructed using a fine charcoal coating and applying an electric voltage (72 V) between the backside of walls and the ground. Various biological markers were monitored that related to general conditions, autonomic nervous systems, stress markers, immunological parameters and blood flow. RESULTS: Regarding the indoor environment, only negatively-charged air resulted in the difference between the CTR and NCR groups. The well-controlled experimental model-room to examine the biological effects of negatively-charged air was therefore established. Among the various parameters, IL-2, IL-4, the mean RR interval of the heart rate, and blood viscosity differed significantly between the CTR and NCR groups. In addition, the following formula was used to detect NCR-biological responses: Biological Response Value (BRV)=0.498+0.0005 [salivary cortisol]+0.072 [IL-2]+0.003 [HRM-SD]-0.013 [blood viscosity]-0.009 [blood sugar]+0.017 [pulse rate]. CONCLUSIONS: Negatively-charged air conditions activated the immune system slightly, smoothened blood flow and stabilized the autonomic nervous system. Although this is the first report to analyze negatively-charged air conditions on human biological responses, the long-term effects should be analyzed for the general use of these artificial atmospheres.     

Simulation of long-term environmental dynamics of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans using the dynamic multimedia environmental fate model and its implication to the time trend analysis of dioxins

Long term environmental fate of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) were studied using the fugacity-based dynamic multimedia environmental fate model. New formulation about soil wind erosion into air was included into the model. Effect of process assumption, sensitivity analysis for parameters, and tentative validation against the measured sediment core analysis was performed. Mass fluxes between compartments were estimated by the dynamic modeling. From the model estimates, major mass fluxes coming from emission source were shown to go to the soil and water through wet/dry deposition, then go to degradation mainly in the soil and sediment. Major mass fluxes of TCDD and OCDD come from the impurities in CNP (Chlornitrofen) and PCP (Pentachlorophenol) directly into the soil. Consideration about multimedia environmental dynamics using the modeled mass fluxes was shown in the discussion.     

Separate estimation of N export into baseline N leakage without disturbance and N loss due to insect defoliation in a pine forest watershed in central Japan

Pine wilt disease (PWD) is caused by a non-native pest that has spread extensively throughout Japan. Previous research has indicated that most infected trees have died and the litter deposited has resulted in changes to stream-water chemistry, particularly increased nitrate (NO ₃ ^? ) concentrations. In this study, we divided stream nitrogen (N) export into N loss due to PWD and baseline N leakage without disturbance based on long-term monitoring. The annual N export was 110.0 mol N ha^?1 year^?1 in 1990 and 749.8 mol N ha^?1 year^?1 in 1997, and had decreased to 37.0 mol N ha^?1 year^?1 in 2005. N export under PWD influence was estimated to be 3697 mol N ha^?1, and N loss due to PWD was 2810 mol N ha^?1. N loss due to PWD was three times larger than baseline N leakage for the disturbed period. These changes in plant–herbivore relationships could affect N status in a forest ecosystem. So-called “semi-natural” disturbances related to non-native species invasion and increases of atmospheric N deposition caused by human activity will increase. Long-term monitoring studies of various aspects are necessary to offer insight into this ecosystem.