Masahiro Osako

Identification of junk buyers’ contribution to recycling of household waste in Hanoi, Vietnam, through a physical composition analysis

Even in developing countries, the amount of containers and packaging waste are increasing in line with population concentration and lifestyle changes in urban areas. This can cause serious problems for the disposal of municipal solid waste. Through a physical composition analysis of household waste in Hanoi, the capital of Vietnam, this study aimed to identify the contribution made by junk buyers to recycling. Interviews on the handling of recyclable waste by households were conducted. About 232 kg of recyclable waste was sampled from a total of 115 households, and about 230 kg of municipal solid waste was sampled from a total of 101 households and sorted into 69 categories for measurement by volume and weight. The interview survey revealed that a high proportion of households tended to routinely store recyclable waste for sale or donation to junk buyers. Junk buyers accounted for 8.8% of recycling by weight or 26.0% by volume according to the results of the physical composition analysis. In addition, the results suggested that containers and packaging waste accounted for the largest proportion of household waste by volume. Junk buyers recycled 25.5% by weight of containers and packaging waste. In the formulation of new plans for municipal solid waste management to improve the current situation and handle future challenges, the role of the informal sector should be monitored carefully and reliable data on recyclable waste should be collected continuously.

Adsorbent characteristics of hydrogen sulfide and methyl mercaptan in single and mixed systems

The paper reports the results of an experimental study made on the changes in gas concentration and adsorption quantity, and in breakthrough (leakage of gas through broken adsorbent) curve at time of dynamic adsorption for the typical malodorous gases; hydrogen sulfide and methyl mercaptan co‐existing in the exhaust gas in many waste treatment facilities both for single system (when these two gases exist independently) and mixed system (when these two gases co‐exist), respectively. The dynamic adsorption test of the mixed gas suggested the significantly different characteristics of activated carbon adsorption of hydrogen sulfide and methyl mercaptan. The presence of hydrogen sulfide was also proved to greatly affect the breakthrough of methyl mercaptan and to shorten the breakthrough time. The test proved it necessary to consider fully the influence of co‐existing components upon the adsorption when designing the adsorption/stripping apparatus for malodor of mixed system.

The flow rate of test odor spouting into the mask in the dynamic odor test

The adoption of the sensory odor test will prevail widely in many local self governments in Japan in order to evaluate and regulate the complex odor in fields. This is also done by the tri‐angle choice bag test. However, this procedure has several problems in the reliability and reproducibility of the results obtained. It is desired to solve these problems by the mechanization of the method. From this point of view, an experimental study on the flow rate of test odor has been carried out and the results obtained are described in this paper. It is confirmed that the optimum flow rate of test odor is about 41/min at the inlet of the mask in the dynamic sniffing method.

Studies on the elimination of gaseous pollutants by plants: adsorption on the surface of plant leaves

In Report 1, a model was proposed for the elimination of air pollutants by plant layers. This has implications to overcome air pollution using road‐side trees and forests because plant layers act as a chemical reactor. In discussing the model, some of the elimination factors were investigated and the diffusion coefficients of flow direction were obtained. In the present experiment, we have packed plant leaves in a glass column and have passed gaseous pollutants through it in order to obtain quantitative formulae for adsorption rates.

Dynamic adsorption characteristics (breakthrough curve) of methyl mercaptan

This study was made on methyl mercaptan for dynamic characteristics using activated carbon. The representative substance of a conventional adsorption model was investigated for adaptability on the basis of actual measurement values. A new model was introduced to verify the model for adaptability. The study found that the Bohart‐Adams formula could not be applied to the explanation of experiment results and, further, that the method developed by Eaglton et al. was not suitable as a method to predict the breakthrough curve. Consequently, the authors proposed a method to find the minimum packed bed length required for formation of constant shape breakthrough curve. This investigation has demonstrated that the method proposed would be effective.

Optimum design method for an adsorber of composite odor

The purpose of the study is to examine the influences which affect adsorbent of acid gas and neutral gas in the case of composite adsorption, to investigate the adsorption contact sequence, and further to express the required thickness of adsorbent by the sum of the saturation zone and adsorption zone. This makes it possible to establish experimentally the expression for calculation of the equilibrium adsorption amount and adsorption zone. As a result, the authors introduce the design procedure for practical adsorption system against the composite system odor in the sewage treatment plant. This has led to the specific design factor for treatment gas amount of 100 m3/min.

Studies on the elimination of gaseous pollutants by plants. Sorption model and diffusion coefficients

The effectiveness of essential oil to eliminate odorants has been shown by many studies. On this basis, the present research has been undertaken to develop a technique using road‐side plants for eliminating gaseous pollutants. A model for the sorption of pollutants by plants has been developed and diffusion coefficients in the plant layer have been experimentally investigated. As a result, diffusion coefficients of flow direction in the plant layer (Ez ) with a gas velocity of 0.68 m/s were obtained as follows: Ez = 0.0207 · LAI1 + 0.107 where LAI’ is the Leaf Area Index of flow direction.

Characteristics of raw kitchen refuse odor and removal of the odor with activated carbon fider

本研究では, 生ごみ臭の臭気特性を把握するとともに, 活性炭素繊維による除去効果を実験的に検討した.得られた結果を要約して示すと次の通りである.1) 生ごみ臭の臭気強度I (6段階表示) と閾希釈倍数D (臭気濃度) の関係式は次式で与えられる.I=1.60 log10D+0.848 (r=0.730, n=84)2) 生ごみ臭における閾希釈倍数Dと不快申告率PU (不快度尺度: 9段階快・不快度尺度) の関係式は, 次式で与えられる.In [P-1.0/ (100-P-1.0) ] =3.54 log D-1.60In [P-2.0/ (100-P-2.0) ] =2.25 log D-1.863) 生ごみ臭においては, 臭気濃度と全炭化水素濃度, においセンサー値およびアミン濃度 (アンモニア換算) との間に比例関係は認められないが, 各指示値は, 103倍以上の臭気濃度に対しては, 大まかな指標になり得る.4) 活性炭素繊維は, 生ごみ臭中のアミン系臭気物質に対する除去能は十分ではないが, 臭気濃度を決定する成分に対しては高い除去効果と持続性を持つと考えられる.5) 生ごみ臭に対しては, 活性炭素繊維フィルターのあとに, アミン系物質の除去装置を付加することにより, 有効な脱臭システムの開発が可能である.

Theoretical and experimental aspects of the tri‐angle choice bag test of odor

Many problems caused by unpleasant odors from industries in Japan have not been solved in spite of the passage of the Japan Odor Control Act in 1977. This Act was made up as the limitation of the concentration of only eight odorants individually, and the evaluation of odor based on the concentration of each odorant is very different from that based on the sensory measure of residents in the damaged districts. From this point of view, many local self‐governments, such as Tokyo metropolis, Saitama and Kanagawa prefectures, are achieving steady results due to the enactment of regulations for odor control based on the sensory evaluation of odor by a method called tri‐angle choice bag test.1 However, the conventional sensory odor tests have some important unsolved problems, such as complicated procedure of sample preparation, treatment of accidental correct answers in the procedure of tri‐angle choice test, standardization to the odorless point for the panel and making the personal fluctuations of measured val...

Survey on the emission factors of air pollutants and odor contained in the smoke during the field burning of Iumbered woods (I)

本調査では, 山林や廃河川敷などの開発に先立って行われる伐採樹木の焼却の際に発生する大気汚染物質について, その発生原単位に関する基礎資料を得るために, 実際の焼却作業に類似した条件でモデル実験を行った.推定の対象とした物質は, 粉塵, タール, 全炭化水素 (THC: Total Hydro Carbon) , 二酸化炭素 (CO2) , 一酸化炭素 (CO) および臭気で, まず本報では, それぞれの汚染物質濃度の計測と, 焼却煙量および気象因子等の観測を行った.本焼却実験の結果, 焼却煙中の各汚染物質の濃度および焼却煙の発生量が各RUNごとに明らかとなり, また, 拡散モデルに摘用される有効煙突高, 初期拡散幅および拡散パラメータがVTR画像解析により把握された.