Removal of insoluble chloride from bottom ash for recycling

In order to recycle bottom ash and use it as raw material for cement production, the removal of insoluble chloride was investigated by testing various washing techniques. The present work is also focused on investigating the properties of insoluble chlorides and determining the conditions for dissolving these compounds in order to reduce the chlorine content to the required level, i.e., less than 0.1 wt%. Within this framework, the effect of washing with water and CO2 bubbling was investigated, because the main insoluble chloride found in bottom ash, i.e., Friedel's salt, can be dissolved by CO2. Then, in order to better understand the removal of Cl, Friedel's salt was artificially synthesized by hydration and then the effect of CO2 bubbling was investigated. If all chlorides in the ash are converted into Friedel's salt by hydration, all chlorides can then be dissolved by CO2 bubbling. In addition, the effect of pH on removing the remaining insoluble chlorides was investigated by washing the ash with sulfuric acid solution. It was found that the most effective technique to reduce the Cl content to less than 1000 ppm was washing with sulfuric acid solution, while keeping the pH value at less than 4. By using this method, Friedel's salt and other insoluble chlorides were dissolved.     

Comprehensive temperature monitoring in an in-vessel forced-aeration static-bed composting process

Comprehensive temperature monitoring was done in an in-vessel forced-aeration static-bed composting process using sewage sludge. The three layers that divided the compost pile horizontally showed different temperature distributions. The temperature of the top layer appeared not to be influenced by the ambient temperature. The temperature of the center area of the top layer was taken to be the representative temperature for evaluating composting start-up performance. The temperature of the bottom layer was strongly influenced by the ambient temperature, and the temperature of the center area of the bottom layer was taken to be the representative temperature for pathogen control as it was the minimum temperature in the reactor. Composting start-up performance was influenced by several factors when the ambient temperature was either below or above 20°C. When the ambient temperature was below 20°C, the time taken to reach 65°C (T ₆₅) was influenced by the temperature of inflowing air, but when the temperature was higher than 20°C, it was influenced by the ratio of sewage sludge to seed compost (F/S). T ₆₅ was least when F/S was 1–2. Received: January 9, 2001 / Accepted: October 10, 2001     

Bioleaching of metal from municipal waste incineration fly ash using a mixed culture of sulfur-oxidizing and iron-oxidizing bacteria

We investigated the behavior and characteristics of metal leaching from municipal solid waste incineration (MSWI) fly ash among pure cultures of a sulfur-oxidizing bacterium (SOB) and an iron-oxidizing bacterium (IOB) and a mixed culture. The IOB has a high metal-leaching ability, though its tolerability against the ash addition is low. The SOB might better tolerate an increase in ash addition than the IOB, though metal leaching ability of the SOB is limited. Mixed culture could compensate for these deficiencies, and high metal leachability was exhibited in the 1% ash culture, i.e., 67% and 78% of leachabilities for Cu and Zn, respectively, and 100% for Cr and Cd. Furthermore, comparably high leachabilities such as 42% and 78% for Cu and Zn were observed even in the 3% ash cultures. Characterization of metal leaching by the mixed culture revealed that the acidic and oxidizing condition had remained stable thorough the experimental period. Ferric iron remained in the mixed culture, and the metal leaching was enhanced by redox mechanisms coupling with the leaching by sulfate. An increase of ferrous iron enhanced the Cr, Cu, and As leaching. The optimum concentration of sulfur existed for As and Cr (5 gl(-1)) and Cu (2 gl(-1)). The presence of the degradable and non-degradable organic compound that must be existed in the natural environment or waste landfills made no significant change in the leachability of metals other than Zn. These results suggested that bioleaching using a mixed culture of SOB and IOB is a promising technology for recovering the valuable metals from MSWI fly ash.     

Adsorption and desorption characteristics of several herbicides on sediment

The objective of this study was to clarify the adsorption and desorption characteristics of several herbicides in sediment. Five herbicides, esprocarb, thiobencarb, dimethametryn, pretilachlor, and simetryn were examined in this study. The adsorption ratio on the sediment increased in the following order: pretilachlor < dimethametryn < simetryn < thiobencarb < esprocarb. On the other hand, the adsorption ratio on the sediment without organic matter increased in the following order: thiobencarb < esprocarb < pretilachlor < dimethametryn < simetryn. Furthermore, the amounts of simetryn, dimethametryn, and pretilachlor adsorbed on the sediment without organic matter increased, while those of esprocarb and thiobencarb decreased in comparison to the original sediment. These results strongly suggested that the mineral surface in the sediment was very important as the adsorption site for the herbicide, especially in the case of simetryn, dimethametryn, and pretilachlor. All the adsorption and desorption data fitted well with the Freundlich equation. The hysteresis in the adsorption-desorption phenomena in the sediment was observed for all the herbicides, and it was affected by the organic matter in sediment, especially in the case of dimethametryn and pretilachlor.     

A quantitative water resource planning and management model for an industrial park level

This paper introduces an integrated water management model at the industrial park level. It suggests four approaches to water management: first, direct water reuse among users; second, water reuse among users by blending with freshwater; third, water reuse between users and a wastewater treatment plant; and fourth, groundwater recharge by reclaimed wastewater or other feasible applications in order to optimize the overall water efficiency. The model results in a comprehensive management methodology for optimizing water resources within an industrial park, seeking potential water reuse among industries, and incorporating the size and cost of reclaimed wastewater delivery systems. A case study is employed to test the model’s feasibility. An economic analysis of the optimized water use network is also carried out, showing the potential water and cost savings.     

The degradability of biodegradable plastics in aerobic and anaerobic waste landfill model reactors

Degradabilities of four kinds of commercial biodegradable plastics (BPs), polyhydroxybutyrate and hydroxyvalerate (PHBV) plastic, polycaprolactone plastic (PCL), blend of starch and polyvinyl alcohol (SPVA) plastic and cellulose acetate (CA) plastic were investigated in waste landfill model reactors that were operated as anaerobically and aerobically. The application of forced aeration to the landfill reactor for supplying aerobic condition could potentially stimulate polymer-degrading microorganisms. However, the individual degradation behavior of BPs under the aerobic condition was completely different. PCL, a chemically synthesized BP, showed film breakage under the both conditions, which may have contributed to a reduction in the waste volume regardless of aerobic or anaerobic conditions. Effective degradation of PHBV plastic was observed in the aerobic condition, though insufficient degradation was observed in the anaerobic condition. But the aeration did not contribute much to accelerate the volume reduction of SPVA plastic and CA plastic. It could be said that the recalcitrant portions of the plastics such as polyvinyl alcohol in SPVA plastic and the highly substituted CA in CA plastic prevented the BP from degradation. These results indicated existence of the great variations in the degradability of BPs in aerobic and anaerobic waste landfills, and suggest that suitable technologies for managing the waste landfill must be combined with utilization of BPs in order to enhance the reduction of waste volume in landfill sites.     

Potential application of high pressure carbon dioxide in treated wastewater and water disinfection: Recent overview and further trends

Recently emerging disadvantages in conventional disinfection have heightened the need for finding a new solution. Developments in the use of high pressure carbon dioxide for food preservation and sterilization have led to a renewed interest in its applicability in wastewater treatment and water disinfection. Pressurized CO₂ is one of the most investigated methods of antibacterial treatment and has been used extensively for decades to inhibit pathogens in dried food and liquid products. This study reviews the literature concerning the utility of CO₂ as a disinfecting agent, and the pathogen inactivation mechanism of CO₂ treatment is evaluated based on all available research. In this paper, it will be argued that the successful application and high effectiveness of CO₂ treatment in liquid foods open a potential opportunity for its use in wastewater treatment and water disinfection. The findings from models with different operating conditions (pressure, temperature, microorganism, water content, media …) suggest that most microorganisms are successfully inhibited under CO₂ treatment. It will also be shown that the bacterial deaths under CO₂ treatment can be explained by many different mechanisms. Moreover, the findings in this study can help to address the recently emerging problems in water disinfection, such as disinfection by-products (resulting from chlorination or ozone treatment).     

Sorption of biodegradation end products of nonylphenol polyethoxylates onto activated sludge

IntroductionRecently ,nonylphenolpolyethoxylates (NPnEO (n :numberofethoxyunits(EOs) )havebecomeaproblematicissueforthereasonthatthesecompounds,animportantgroupofnonionicsurfactants ,havebeenusedwidelyinvariousindustriesasflocculants,dispersants,emulsifie…     

Two-step accelerated mineral carbonation and decomposition analysis for the reduction of CO2 emission in the eco-industrial parks

Carbon dioxide（CO2） emissions are a leading contributor to the negative effects of global warming. Globally, research has focused on effective means of reducing and mitigating CO2 emissions. In this study, we examined the efficacy of eco-industrial parks（EIPs） and accelerated mineral carbonation techniques in reducing CO2 emissions in South Korea.First, we used Logarithmic Mean Divisia Index（LMDI） analysis to determine the trends in carbon production and mitigation at the existing EIPs. We found that, although CO2 was generated as byproducts and wastes of production at these EIPs, improved energy intensity effects occurred at all EIPs, and we strongly believe that EIPs are a strong alternative to traditional industrial complexes for reducing net carbon emissions. We also examined the optimal conditions for using accelerated mineral carbonation to dispose of hazardous fly ash produced through the incineration of municipal solid wastes at these EIPs. We determined that this technique most efficiently sequestered CO2 when micro-bubbling, low flow rate inlet gas, and ammonia additives were employed.