Since most dioxins produced by the incineration process are deposited in incineration residues, MSW landfill can be a possible dioxin source to the environment through the dispersion of residues. In this study, the possibility of residue dispersion was studied by using a lab-scale wind chamber. An operational target to prevent dispersion was then proposed.
Incineration ashes from four different MSW incinerators were used in the experiment. To simulate dumping residues in a landfill, ash was charged from the top upstream of the chamber. Only fine particles of less than 250 micro-meters are able to disperse, although minus 125 micro-meter size particles have a high dispersion rate. Increased moisture content (MC) was found to reduce dispersion rate considerably. The minimum MC needed to prevent dispersion of ash was determined to be 50-70% of the initial MC as discharged from the incinerators. Fly ash treated for stabilization was also examined in terms of its fraction of fine particles.

View full abstract

Chlorine sources and forms are considered to be the most important factors in the formation of Dioxins/Furans (Dioxins) due to the fact that Dioxins are organochlorine compounds. In the present work, effects of chlorine sources and forms on the formation of Dioxins in the combustion process have been investigated, mainly through combustion experiments and also through thermodynamic evaluations on the formation of Dioxins in the combustion furnace of a laboratory scale at 800°C.
Dioxins are formed even at the combustion temperature of 800°C by the existence of four constituents, i. e. C, H, O and Cl. The formation concentration of Dioxins is nearly proportional to the chloride concentration of combustion materials under the conditions of the same chlorine sources and forms, and is significantly influenced by chlorine sources, i. e. organochlorine compound or inorganic chloride. Even in the case of inorganic chloride, Dioxins of high concentration are shown from combustion experiments to be formed by the existence of an active chlorine such as the hydrate, made from salt and flour.

View full abstract

A public space at a university was the scene for this living experiment on decreasing the incidence of littering. Every morning the space was cleaned up and every evening at 6 : 00 pm litter was gathered and analyzed. People who spent time in the space or passed through it were counted every ten minutes using a camera. In the first experiment, the amount of litter found for the reference period when there were no trash bins or a warning signs was compared to the observation period when trash bins were placed along with signs saying“Put trash in the trash bins.”Results showed that the littering ratio of cans and bottles was below 10% during the observation period, and that the presence of signs and trash bins had an observable effect. In the second experiment, a comparison was made for the amount of cigarette waste generated in a reference period when there were no ash trays or signs in place, and an observation period when signs saying“Put cigarette butts in the ash trays”and accompanying ash trays were set up. Results showed that the littering ratio of cigarette butts was 61-67% in the observation period, and that there was little effect observed in the decrease of littered cigarette butts when signs and ash trays were in place. The tendency observed was that while smokers will put butts into an ash tray if it is placed right next to them, they do not put the butts in if the ash tray is not right there. It is necessary to study intervention methods such as awareness campaigns and appeals for getting smokers to not litter their cigarette butts, and put them in ash trays in public spaces.

View full abstract

Alkali decomposition of poly (ethylene terephthalate) (PET) with sodium hydroxide in ethylene glycol (EG) revealed to be an efficient method for the reproduction of pure terephthalic acid (TPA) and EG from recovered PET plastic wastes. This was done under mild conditions at 180°C for 15min. The recovered TPA and EG contain no impurities such as dyes or metals.
In this study, both the environmental loading (using inventory analysis) and cost charge concerning the reproduction of PET resin from the monomers recovered from this monomer recycling method were estimated. In comparison with the production of virgin PET resin from crude oil, this monomer recycling process can reduce environmental loading, such as energy consumption and pollution, to the extent that it can be used as a practical method for the recycling of PET plastics.

View full abstract

Porous materials with a high adsorption ability were synthesized by the simultaneous calcination of a mixture of inorganic and organic industrial solid wastes. The microstructure, mechanical strength, and adsorption characteristics were investigated. Sludge and Rasping were mixed with clay minerals and water, and then mulled and extruded to form a green rod. Porous materials were synthesized by calcination in air at 850°C. SEM observation of the porous material exhibited the honeycomb sectors originated from the fibrous structure of rasping, and the macro-pores formed by a foam-evaporating calcination of the sludge and clay. Analysis of the microstructures and mechanical properties of the porous materials prepared with different mixing ratios, revealed that each raw material played an important role in the feature of the material, i. e, (1) sludge contributed to the high mechanical strength of the bulk, and (2) clay particles inhibited the combustion of rasping, which led to the carbonization of rasping. Synthesized porous materials were found to have a high adsorption ability for methylene blue. It was demonstrated from the adsorption measurements for the porous materials with different mixing ratios, that the adsorption ability was greatly affected by the structure and properties of the calcined clay minerals.

View full abstract

An adsorption gel for lead (II) ion was prepared by milling still wet mandarin orange residue just after juicing with some calcium hydroxide. A previous experimen had shown that pectic acid which is present in orange juice residue gives rise to a very stable complex with lead (II) ion. The effects of the amount of added calcium hydroxide, the ratio of the weight of the adsorption gel to the volume of aqueous solution containing lead ions, contact time and pH of the aqueous solution were examined. The adsorption behavior of dry orange juice residue powder that has been prepared by drying the wet residue with lime at high temperature using a rotary kiln, a product commonly as cattle feed, was also examined and compared with the gel prepared in the present work. The following results were obtained.
(1) Nearly perfect removal of lead was achieved over the wide pH range of 4-7 by using the gel prepared from wet orange juice residue.
(2) The removal of lead decreased greatly when the gel was used with aqueous solution of a pH greater than 8 or when using a gel prepared with too much calcium hydroxide.
(3) The dry orange juice residue powder was found to be not very effective for the removal of lead because the adsorption of lead was much lower at low solid/liquid ratios.
Although the gel prepared from wet orange juice residue was found to be very effective for the removal of lead, it suffers from a degradation problem and, consequently, it seems to be difficult to preserve. The dry orange juice residue powder, however, is free from this problem. A new adsorption gel with high efficiency for lead removal and free from the degradation problem needs to be developed from orange juice residue in the future.

View full abstract

The environmental impact of the curbside collection of garbage was simulated using a modified“Grid City”model and NOx, CO and THC emissions from collection trucks were colculated. The important results are: (1) inter-collection station distances of 50-100 m maximizes collection efficiency and minimizes environmental impact, (2) increase of the velocity of collection truck increases collection efficiency and decreases environmental impact and (3) a small collection area is favorable in respect to collection efficiency and environmental impact. Comparisons of simulated and estimated emissions of the three pollutants indicates that the“velocity”method gives satisfactory results, while assumptions about gas mileage can signicanfly influence the estimate of the environmental impact.

View full abstract

Generation and management systems for infectious hospital wastes (IHW) at five hospitals in Osaka were studied. All hospitals interviewed agreed that medical waste, including IHW, should not be incinerated on site, so as to avoid generation of pollution. Wastes should be treated by licensed waste management companies even if the cost of treatment would be significantly more expensive than self-treatment practices. The generation rate of IHW (L/year) was expressed by an exponential function of number of beds N, 2, 350 exp (6.95×10^-3N) . Treatment of IHW cost the hospitals 40-70 yen/L. A case study on one hospital that generated medical waste at 498 m³/year was performed for estimating percentages of IHW by divisional generation, by categories of medical supplies, and by materials used for medical supplies. IHW occupied 1.5% (v/v) of the total medical waste and generation of IHW from wards was highest. Latex was used as the main medical supply material, and showed 51% (w/w) . Other major materials used as medical supply materials were cotton, felt, and polyvinylchloride, percentages being 23%, 12%, and 7%, respectively. This basic data will be in the area of risk management and in developing appropriate treatments for IHW.

View full abstract