Hiroshi Asakura

Experimental study of behavior of endocrine-disrupting chemicals in leachate treatment process and evaluation of removal efficiency.

An experimental study of the behavior of endocrine-disrupting chemicals (EDCs) in leachate treatment processes (aeration, coagulation and sedimentation, activated carbon adsorption, and advanced oxidation) was conducted and removal efficiencies were evaluated. Among target EDCs, concentrations of BPA (1800 times), DBP (10 times), BBP (40 times), and DEHP (30 times) in leachate are more than ten times higher than those in surface water. BPA, DBP, and BBP can be treated by aeration and DEHP, by advanced oxidation processes. BPA could not be effectively removed by coagulation and sedimentation because most of BPA partitioned in the supernatant. DEHP could hardly be treated by aeration. The removal ratios of DEHP were approximately 50-70% if the generated sediment was removed completely. The removal ratios of DEHP in leachate of 100 m(3)/d with 100 kg of activated carbon were 50-70%, assuming a complete mixing model. The concentration of DEHP was decreased to below one-tenth in 120 min by advanced oxidation processes.

Improvement of permeability of waste sludge by mixing with slag or construction and demolition waste

To determine the allowable ratio of waste sludge required to ensure an aerobic zone in the landfill, we investigated sludge permeability, which involved mixing sludge, the major landfill waste in Japan, at different mixing ratios with other wastes (slag and construction and demolition waste (C&D)). We measured parameters of sample permeability and analyzed parameters that exert a large influence on oxygen penetration depth with a simulation model accounting for both diffusion and convection driven by temperature gradients. We also determined the critical volumetric contents in which gas and/or water permeability change significantly when sludge is mixed with sand or gravel. From the results of the simulations, gas permeability of the layer, the difference between inside and outside temperatures and the oxygen consumption rate exert a large influence on the resulting oxygen penetration depth. The allowable ratio of sludge required to ensure an aerobic zone in the landfill was determined by considering the balance of the above three parameters. By keeping volumetric sludge content to below 25%, air convection and oxygen penetration depth of several meters were achieved in the modeling.

Gypsum and organic matter distribution in a mixed construction and demolition waste sorting process and their possible removal from outputs

With insufficient source separation, construction and demolition (C&D) waste becomes a mixed material that is difficult to recycle. Treatment of mixed C&D waste generates residue that contains gypsum and organic matter and poses a risk of H(2)S formation in landfills. Therefore, removing gypsum and organic matter from the residue is vital. This study investigated the distribution of gypsum and organic matter in a sorting process. Heavy liquid separation was used to determine the density ranges in which gypsum and organic matter were most concentrated. The fine residue that was separated before shredding accounted for 27.9% of the waste mass and contained the greatest quantity of gypsum; therefore, most of the gypsum (52.4%) was distributed in this fraction. When this fine fraction was subjected to heavy liquid separation, 93% of the gypsum was concentrated in the density range of 1.59-2.28, which contained 24% of the total waste mass. Therefore, removing this density range after segregating fine particles should reduce the amount of gypsum sent to landfills. Organic matter tends to float as density increases; nevertheless, separation at 1.0 density could be more efficient.

Characteristics of fine processed construction and demolition waste in Japan and method to obtain fines having low gypsum component and wood contents

A method to obtain processed residue from mixed construction and demolition waste (mixed C&D-W) — free from environmental pollutants — for deposition in landfill is discussed. In particular, additional sieving, the presence of gypsum board in mixed C&D-W at the first stage of manual presorting, and the color of processed residue were studied for the basic characterization of the different fractions. Considerable precautions should be taken to prevent leaching of hazardous substances, such as T-Hg, Pb, Cr6+, As, and fluoride and its compounds, when processed residue, particularly in crushed fraction at an intermediate treatment facility, is used as construction material. A relatively high content of gypsum was noted in processed residue generated at demolition work compared to that generated at construction work in processed residue from mixed C&D-W in which the presence of gypsum board was observed at the first stage of manual presorting, and in white processed residue. Additional sieving for removal was ineffective because gypsum and wood have wide particle size distributions. To obtain processed residue having low gypsum and wood contents, white processed residue should be removed to eliminate gypsum (content, 59% of initial sample), and brown or brown and yellow processed residue should be removed to eliminate wood (content, 32% of initial sample) without mixing with processed residue containing other colors at stockyards. The removed residue should be deposited in a controlled-type landfill site.

Influence of oxygen flow rate on reaction rate of organic matter in leachate from aerated waste layer containing mainly incineration ash.

It is known that aeration reduces rapidly the concentration of organic matter in leachate. However, the oxygen flow rate required to attain a certain reaction rate of organic matter should be carefully estimated. In this study, using the oxygen ratio (the ratio of oxygen flow rate by aeration to oxygen consumption rate of waste layer) as a parameter, the reaction rate of organic matter in leachate from landfilled incineration ash and incombustible waste upon aeration was evaluated. Total organic carbon (TOC) in the leachate was reduced rapidly when the oxygen ratio was high. The decomposition rate exceeded the elution rate of TOC in the leachate from the waste layer for several days when the oxygen ratio was above 10(2). The results indicate that the oxygen ratio can be used as a parameter for the aeration operation in actual landfill sites, to rapidly stabilize organic matter in leachate.

Adopted technologies and basis for selection at municipal solid waste landfill facilities constructed in recent years in Japan

In Japan, as the construction of new landfill facilities has become extremely difficult and the number of sites procured for landfill construction has decreased due to the ‘not in my back yard’ (NIMBY) syndrome, it has been assumed that the adoption of new technologies has increased. As the performance of new technologies exceeds that of conventional technologies, it is also assumed that residents would prefer the use of these new technologies and therefore any construction plans should be devised to ensure their use to ensure residents’ satisfaction. In the present study, the technologies adopted for municipal solid waste landfill facilities constructed in recent years (2000 to 2004) in Japan and the bases for their adoption were investigated by means of a questionnaire survey. One of the main bases for the adoption of new technologies was the request by residents for new technology for roofing, rather than the other for new technologies for barrier systems, leachate treatment, and monitoring. In addition, it is possible that the municipalities did not recognize the difference between conventional and new technologies as defined in this study. The roof-type landfill that isolates waste from the surrounding environment was one of the requirements for the construction of new landfill facilities identified in the present investigation, and in this regard waste isolation should be required in all circumstances.

Investigation on the components removed in loss on ignition test of sandy crushed construction and demolition waste

Processed sandy residue generated from mixed construction and demolition waste (mixed C&D-W) was investigated for possible deposition in landfill. The basic properties and the components removed in the loss on ignition (LOI) test were examined. The target material for decreasing LOI was elucidated and the validity of LOI used as landfill standard for inert industrial solid waste was discussed. LOI of most of the samples was above 5% and therefore, in principle, processed sandy residue should not be deposited in inert-type landfill. As LOI of sandy residue was mainly due to bound water, the LOI could not be decreased to below 5% even if wood, which is the major organic matter in the sandy residue, was removed. However, decreasing the amount of wood could lead to a subsequent decrease in the amount of dissolved organic matter. Therefore, the LOI of processed mixed C&D-W used as landfill standard for inert industrial solid waste should be re-evaluated.

Grouping by Visual Appearance of Construction and Demolition Waste forSorting Time Reduction with the Aim of Removing Asbestos-ContainingMaterials

As asbestos-containing waste from building demolitions has to undergo special treatment prior to recycling or final disposal, the demolition of buildings and the sorting of waste materials are conducted after checking for asbestos content in the construction materials (according to ISO, EPA or JIS). However, as solid waste is usually a mixture, it is possible that asbestos-containing material (ACM) is present in construction and demolition waste (CDW) that is transported to an intermediate treatment facility for CDW. In addition, the presence of ACM in disaster waste cannot be avoided. Therefore, a rapid method for the determination of asbestos at an intermediate treatment facility for CDW is required. In this study, the separation efficiency and the sorting time of CDW particles by grouping by visual appearance (GVA) were determined. In the case that the separation efficiency by GVA in this study was equivalent to that by visual observation with a loupe (DVL) in a previous study, the reduction of sorting time by GVA was evaluated. Newton’s separation efficiency by GVA and recovery rate were equivalent to that by DVL for 5.1 cm2 observation. In this case, the sorting time by GVA was 1/7 of that by DVL. Therefore, sorting time could be shortened by GVA under the condition of equivalent separation efficiency. In order to reduce the sorting time per worker to less than 1 h/t, only CDWPs having particle size larger than 12 cm for GVA or 20 cm for DVL for 5.1 cm2 observation should be subjected to sorting. Aiming to avoid diffusion of asbestos-containing waste, the authors suggest that grouping by visual appearance as a primary sorting step is effective to reduce sorting time of CDW from disaster waste or unknown origin.

Alkaline solution neutralization capacity of soil

Alkaline eluate from municipal solid waste (MSW) incineration residue deposited in landfill alkalizes waste and soil layers. From the viewpoint of accelerating stability and preventing heavy metal elution, pH of the landfill layer (waste and daily cover soil) should be controlled. On the other hand, pH of leachate from existing MSW landfill sites is usually approximately neutral. One of the reasons is that daily cover soil can neutralize alkaline solution containing Ca(2+) as cation. However, in landfill layer where various types of wastes and reactions should be taken into consideration, the ability to neutralize alkaline solutions other than Ca(OH)(2) by soil should be evaluated. In this study, the neutralization capacities of various types of soils were measured using Ca(OH)(2) and NaOH solutions. Each soil used in this study showed approximately the same capacity to neutralize both alkaline solutions of Ca(OH)(2) and NaOH. The cation exchange capacity was less than 30% of the maximum alkali neutralization capacity obtained by the titration test. The mechanism of neutralization by the pH-dependent charge can explain the same neutralization capacities of the soils. Although further investigation on the neutralization capacity of the soils for alkaline substances other than NaOH is required, daily cover soil could serve as a buffer zone for alkaline leachates containing Ca(OH)(2) or other alkaline substances.