Eubacterial communities and bacterial pathogens occurring in the leachates collected from three full-scale landfills in mesothermal area of Japan were analyzed using DNA microarrays targeting approximately a thousand eubacterial and pathogen species/groups. The leachate samples showed almost similar eubacterial compositions with marginal variations. Comparison of the results with precedents suggested that the predominant eubacterial populations in the landfills may be generally similar in East and Southeast Asia, irrespective of the climate zone. Analysis of the bacterial pathogens showed that the three leachates included a total of 44 species/groups of bacterial pathogens and 26 species/groups including Francisella, a frank zoonotic pathogens causing a serious health risk, and other high-risk pathogens were commonly found. In addtion, the 2 leachate samples from the landfills, where organic wastes such as sludge and raw garbage were mainly disposed, had 15 specific pathogens. It was suggested that sludge can increase the variation of the pathogens occurring in landfill leachates. Overall, results of this study posed some insights into the underlying microbial ecology in the landfill and the possible microbiological health risks associated with the landfill leachate.
This study is an attempt at development of low-cost and effective technologies for leachate treatment using cover soil. A mixture of Andisol and waste iron powder was selected as cover soil for adsorption of heavy metals in landfill leachate. Batch adsorption experiments were performed to assess the performance of Andisol and waste iron powder for heavy metal adsorption under various conditions (pH, temperature, etc.). The adsorption of heavy metals on both adsorbents was well described using the Freundlich isotherm equation model. Andisol and waste iron powder have high adsorption capability. For pH 4-6, the Freundlich constant KF of both adsorbents remained almost constant. The Freundlich constant KF, which reflects the adsorption capacity, increased with increasing temperature to 35, 3 K. Thermodynamic parameters were calculated. The thermodynamic parameters of both adsorbents showed the endothermic and spontaneous nature of the process. Using these results, it was concluded that the mixture is useful as cover soil for removal of heavy metals from leachate under oxidative condition. Column adsorption experiments were performed using the mixture for determination of kinetic parameters under a dynamic adsorption process. The Bohart and Adams model showed a better fit for Cu, Pb, and Zn. In the bed depth service time (BDST) model, the adsorption capacity N0 and rate constant k are obtainable.
The final disposal ratio of mixed construction and demolition waste (MCDW) remains high in Japan, while progress has been made in the recycling of other construction and demolition waste. Sorting facilities are expected to play an important role in better management of MCDW. In this study, the feasibility of sorting facilities for the separation of material and of pretreatment for fmal disposal was investigated by conducting a batch experiment at a real operational facility. The material flow of each output fraction was determined based on the mass distribution and on analysis of the ignition loss and metal content. The separation of organic matter and ferrous metal achieved by the sorting process was excellent; almost 70% was separated out for recycling and did not go for disposal. Although the distribution ratios of heavy metals, such as Pb and Zn, sent to landfill were still high, their content little changed from the condition of the original mixed waste. The process of sorting MCDW achieved reduction of mass for disposal, reduction of the organic load directed to the landfill, and the diversion of iron from MCDW to recycling.
Palygorskite, which is one of magnesium aluminum silicate, was investigated as adsorbent to adsorb ammonia gas in this study. The palygorskite was pretreated with HCl, HNO3 or NaOH with different concentration, temperature and reaction time. Raw palygorskite and pretreated ones were characterized with specific surface area by Brunauer-Emmett-Teller method, crystal structure by X-ray diffraction and metal dissolution by inductively coupled plasma-optical emission spectroscopy. Adsorption experiments were carried out at room temperature with an initial ammonia concentration in the range of 150-3000 ppm in nitrogen carrier gas. The adsorption capacity of ammonia was investigated by the 10% breakthrough time. The results showed that palygorskite had excellent adsorption property for adsorbing ammonia. The sample HCl-352 pretreated with 3 mol/l of HCl at 50°C for 24 hours had the highest adsorption capacity of 17.2mg/g.
Biowaste, the separately collected organic fraction of municipal solid waste, can be reused for soil conditioning after composting. In this study, a series of field investigations was conducted on human health essential minerals, Ca, Fe, Mg, Mn, Zn, Cu and toxic heavy metals, Pb, Cr, Cd in soil which have been amended with biowaste composts only or amended with chemical fertilizer plus lower composts. The results show that the biowaste compost applications likely led to the increases of mineral elements in soils for Ca, Mg, Mn and Zn excluding some exception. It was also found that biowaste compost applications have shown the tendency of the increases of bio-available forms of Fe, Mn and the reverse situation for Mg. Comparison of supply ratios (SR = bio-available content/total content×100%) of all elements in compost-amended and no amended soils showed that the leachability of Fe, Mn, Zn, Pb was slightly increased by biowaste compost application, and less changed for other elements.