Material and monetary flows of construction and demolition waste and assessment on physical and environmental properties of illegally dumped construction and demolition waste in Hanoi.

The main aim of this study is to investigate the material and monetary flows of CDW management and to characterize the distribution of illegally dumped CDW in Hanoi. Construction and demolition waste management has become a source of much concern to the urban authorities and citizens of big cities in Vietnam. It is estimated that 3000 t of CDW were generated per day from construction and demolition activities in Hanoi, but only 45% of the CDW was received at official landfills, while 55% of the CDW was disposed of elsewhere. The consequences of improper waste management are potentially alarming. The study conducted interviews to identify the material and cash flow associated with licensed and unlicensed contractors in CDW classification, transportation, treatment, and disposal, to characterize the distribution of illegally dumped CDW in two districts in Hanoi (urban and suburban districts), and to assess the composition of dumped CDW and environmental assessment of illegally dumped CDW by chemical analyses such as leaching and content tests. The study concluded that illegal dumping was performed mostly by unlicensed private companies. The illegally dumped CDW was mostly composed of mixed materials such as concrete, bricks, stones, and some hazardous materials such as asbestos and gypsum were found. The environmental concern of illegally dumped CDW was mostly dust, blockage of water ways, and inundation of increased suspended solids, whereas the heavy metal leaching concentration of all samples was below the environmental standards in Vietnam.

Current state of building demolition and potential for selective dismantling in Vietnam.

In Vietnam, an increase in construction activities together with the absence of recycling-oriented demolition techniques is giving rise to an alarming generation of construction and demolition waste. This study scrutinized the current state of building demolition approaches in Hanoi, Vietnam and evaluated the potential for the selective dismantling, or deconstruction, of reinforced-concrete (RC) houses. Site observations, direct measurement, and interviews were conducted to obtain information on technical, environmental, and economic characteristics of three residential housing sites, each representing a typical current demolition technique (manual, hybrid, and mechanical demolition). A selective dismantling site is proposed based on the collected survey data and published case studies. Our findings confirmed the unsustainability of RC-building demolition practices in Hanoi, which have an average reuse/recycling rate of roughly 3%. The application of selective dismantling will boost the recycling rate to a remarkable 90%, associated with a 55% decrease in greenhouse gas emissions. Even though selective dismantling is more time-consuming and therefore more costly, it results in double the resale value and an eight-fold decrease in disposal costs. The results of a sensitivity analysis indicate that increasing the current disposal fee will significantly improve the feasibility of selective dismantling, suggesting a need for stricter disposal charging mechanisms along with other interventions such as the development of recycling facilities to promote the introduction of this building removal alternative in Vietnam.

Impact of diatomite addition on lead immobilization in air pollution control residues from a municipal solid waste incinerator.

Air pollution control (APC) residues, which are known to be the byproducts of incineration treatment, exhibit a high leaching potential of toxic metals. Calcium silicate hydrate (C-S-H), which is a major hydration product of hardened cement and immobilizes toxic metal, can be formed by the reaction of Ca with pozzolanic Si in a highly alkaline environment. Toxic metals might be immobilized by the addition of pozzolanic material to APC residues (instead of using cement), which is a Ca source and provides an alkaline condition. In this study, diatomite, which mainly comprises amorphous silica (SiO2·nH2O), was investigated as a pozzolanic material for Pb immobilization in APC residues obtained from a municipal solid waste incinerator. APC residues were cured with and without the addition of diatomite at different temperatures. When diatomite was added to APC residues, pozzolanic phases such as C-S-H gel were formed via the consumption of Ca(OH)2 and CaClOH. Compared to APC residues cured without diatomite, the leaching of Pb decreased by 99% for APC residues cured for 14 days with 10% diatomite at 70 °C. The results of sequential chemical extraction showed that water-soluble Pb in APC residues was reduced from 10.3% to nearly zero by the pozzolanic reaction. Consequently, the leaching amount of Pb dropped below 0.3 mg/L (Japanese criteria for landfill disposal). Overall, these experiments provide promising results regarding the possibility of using diatomite for pretreating APC residues.

Personality traits affect critical care nursing competence: A multicentre cross-sectional study.

OBJECTIVE: To investigate the relationship between personality traits and critical care nursing competence among critical care nurses. RESEARCH METHODOLOGY/DESIGN: Multicentre cross-sectional survey using a self-report questionnaire and path modelling, from August 2017 to December 2018. SETTING: Six intensive care units in Japan. MAIN OUTCOME MEASURES: We assessed relationships among the Big Five personality traits and four critical care nursing competencies in nurses. FINDINGS: We included 211 nurses (77.7% women, 59.2% in their 20 s); 62.6% had 1-5 years' critical care nursing experience. Among the four competencies, principles of nursing care had a direct positive effect on decision-making (0.77, p < 0.001); decision-making had a direct positive effect on collaboration (0.74, p < 0.001) and nursing interventions (0.77, p < 0.001). The personality traits openness to experience, agreeableness, and extraversion had a significantly positive effect (0.17, p < 0.05; 0.43, p < 0.001; 0.29, p < 0.01; respectively) on principles of nursing care, the key competency. The personality trait neuroticism had a direct or indirect negative effect on all four nursing competencies. CONCLUSION: Nursing competence in the critical care setting is affected by personality traits. Our findings can be applied in nursing education to improve competence based on individual personality traits.

Financial and economic evaluation of construction and demolition waste recycling in Hanoi, Vietnam.

Increasing waste generation and the absence of a formal recycling industry are exacerbating the inadequacy of Construction and Demolition Waste (CDW) management in Hanoi, Vietnam. This study assesses potential CDW recycling in Hanoi by estimating the prospective supply of and demand for CDW recycling plants and evaluating their likely costs and benefits. Supply of concrete waste was calculated based on the weight-per-construction-area method whilst demand for recycled concrete aggregates (RCA) was determined by estimating the amount of aggregates for road construction in Hanoi from 2013 to 2017. Two potential models of CDW recycling plants were considered: a stationary plant and a mobile plant, with capacities of 1,000 and 360 tons/day, respectively. Our findings reveal that demand for RCA exceeds waste concrete supply, suggesting a promising market for RCA. Positive Net Present Value and Internal Rate of Return values of the stationary plant indicate its feasibility as an investment option. Meanwhile, the introduction of mobile recycling plants might require governmental intervention to internalize recycling positive externalities. Supporting policies might include a combination of a virgin material tax, green public procurement, and quality standard development.

Waste generation, composition, and handling in building-related construction and demolition in Hanoi, Vietnam.

This study conducted a survey at 15 building construction and demolition sites in Hanoi, Vietnam in order to identify waste generation rates (WGR), composition, and current handling practices of construction and demolition waste (CDW). Waste quantification based on CDW layout, image analysis to identify CDW components, and face-to-face interviews with construction and demolition contractors to reveal CDW flows were performed. WGRs of 79.3 kg/m2 and 1,030 kg/m2 were determined in small- and large-scale construction sites, respectively, whilst WGRs at small and large demolition sites were 610 kg/m2 and 318 kg/m2. The composition analysis identified soil, concrete, and brick as the major CDW components, consistent with building structures in Vietnam. The interviews discovered that merely 10% of total CDW flows was from recycled and reused CDW. Reuse and recycling rates were most significant for metal and were lower (in descending order) for brick, concrete, and soil. These findings raise a need for aggressive and integrated strategies to promote more sustainable CDW management in the country, including the development of recycled CDW product standards, policies that facilitate recycling, and more importantly, a sustainable business model for CDW recycling, for which future evaluations of economic feasibility are of great importance.

Low fraction of methane in landfill gas emissions in an industrial waste landfill containing incineration ash and gypsum board waste under anaerobic conditions.

The behaviour of carbon dioxide (CO2) and methane (CH4) emissions at the surface and below the soil cover in an industrial waste landfill under anaerobic operating conditions was evaluated for six years. This landfill contained gypsum board waste and incineration ash - a practice currently allowed because of a change in Japanese regulations. The CO2 and CH4 fluxes decreased throughout the six years of the survey. Almost all of the survey points exhibited fractions of CH4 in landfill gas emissions of <0.5 (mean values: 0.0-0.1 [surface], 0.0-0.3 [subsurface]) under anaerobic conditions. In addition, a relatively high first-order reaction rate constant for the landfill gas emissions (0.3 year-1) was observed. The landfill leachate showed a relatively high sulphate ion (SO4 2-) concentration, although other environmental conditions, such as the pH, oxidation-reduction potential and ammonium concentration, were not at levels that could have inhibited CH4 production. These findings suggest that the low fractions could have been related to the lower amounts of CH4 generation caused by competition between methanogens and sulphate-reducing bacteria (SRB). Therefore, SRB could play a major role in the degradation of organic carbon in the landfill.

Long-term removals of organic micro-pollutants in reactive media of horizontal subsurface flow constructed wetland treating landfill leachate.

In this work, the removals of organic micro-pollutants (OMPs), i.e. DEP, DBP, 2,6-DTBP, BHT, and DEHP in sand, clay and iron powder mixed media of horizontal subsurface flow constructed wetland (HSSF) from landfill leachate were investigated over 3 years period. The biodegradation was mainly responsible for the removals of DEP, DBP, 2,6-DTBP and BHT whereas DEHP was initially removed through adsorption and formation of iron-organic complex and then subsequently biodegraded during long-term operation as OMP degrading microbial consortium attached to the reactive media was enriched. This study demonstrates that an application of reactive HSSF system can be a viable option for advanced landfill leachate treatment to meet ecological safety level.

Development of an easy-to-use questionnaire assessing critical care nursing competence in Japan: A cross-sectional study.

BACKGROUND: Critical care nurses need a high level of medical competence, especially with regard to patient safety. There are several tools to measure general and critical care nursing competence, but the usability of these tools is inadequate because they include large numbers of questions. To maintain quality and safety in intensive care units (ICUs), it is necessary to be able to easily measure and evaluate critical care nursing competence. The purpose of this study was to develop an easy-to-use questionnaire assessing critical care nursing competence related to patient safety. METHODS: A cross-sectional, descriptive, explorative study was designed to collect data from nurses working in six ICUs in tertiary hospitals in Japan. Data were collected from August 2017 to December 2018. The Critical Care Nursing Competence Questionnaire for Patient Safety (C3Q-safety) is a 22-item instrument designed to assess nursing competence related to patient safety in ICUs. Items were developed based on previous work related to critical care nursing competence and were adjusted based on a pilot study. RESULTS: A total of 211 nurses working in ICUs participated in this study. Through descriptive statistics and factor analysis, the number of questions was reduced from 24 to 22. The C3Q-safety had four factors: decision making, collaboration, nursing intervention, and principles of nursing care. Cronbach's alpha ranged from 0.73 to 0.83. The four factors showed positive correlations with each other (0.47 to 0.72). Nurses licensed as certified nurses in intensive care and those with longer ICU work experience showed significantly higher scores on all four factors. CONCLUSIONS: We developed an easy-to-use questionnaire to assess critical care nursing competence related to patient safety. The C3Q-safety was able to detect four areas of competence. The C3Q-safety will make it possible to easily measure critical care nursing competence and can be utilized for efficient education.

The effectiveness of passive gas ventilation on methane emission reduction in a semi-aerobic test cell operated in the tropics.

Two landfill test cells, with and without gas vents, were used to investigate the effectiveness of passive aeration, through basal leachate pipes, in mitigating methane emissions from municipal solid waste disposal in the tropical climate of Thailand. Surface methane emission rate, as well as methane content in the landfill gas, were determined for a period of three years. The results indicate that the average methane emission rate from the test cell with passive gas vents (42.13 g/t dry wt./d) was about half of that from the test cell without gas vents (90.33 g/t dry wt./d). Methane emission rates from both test cells fluctuated and were influenced by precipitation. The emission rate during the wet period in the test cell with gas vents (61.67 g/t dry wt./d) was 3 times as much as that observed during the dry period (20.95 g/t dry wt./d). The emission rate during the wet period in the test cell without gas vents (120.33 g/t dry wt./d), was twice the value of that observed during the dry period (60.32 g/t dry wt./d). The measurements also revealed the formation of methane hotspots in the test cell with passive vents after rainfall events, leading to higher localized surface emissions. Introduction of gas vents helped reduce methane emissions from solid waste landfills in a tropical region. However, rainfall should be limited to avoid turning semi-aerobic conditions into anaerobic conditions.

Removal of heavy metals from synthetic landfill leachate in lab-scale vertical flow constructed wetlands.

Synthetic landfill leachate was treated using lab-scale vertical flow constructed wetlands (CWs) in sequencing batch modes to assess heavy metal removal efficiencies. The CWs filled with loamy soil and pumice stone were unplanted or planted with common reed (Phragmites australis) (Reed-CW) or common rush (Juncus effusus) (Rush-CW). Synthetic leachate contained acetate, propionate, humate, ammonium, and heavy metals. Common reed grew almost vigorously but common rush partly withered during the 8-month experiment. The CWs reduced the leachate volume effectively by evapotranspiration and removed easily degradable organic matter, color, and ammonium. Furthermore, the CWs demonstrated high removal amounts for heavy metals such as Zn, Cr, Ni, Cd, Fe, and Pb, but not Mn from leachate. The metal removal amounts in the CWs were low for high-strength leachate (influent concentration increased from one time to three times) or under short retention time (batch cycle shortened from 3days to 1day). The Rush-CW showed slightly lower removal amounts for Cr, Ni, Mn, and Cd, although the Reed-CW showed lower Mn removal amounts than the unplanted CW did. However, Cd, Cr, Pb, Ni, and Zn were highly accumulated in the upper soil layer in the planted CW by rhizofiltration with adsorption compared with unplanted CW, indicating that the emergent plants would be helpful for decreasing the dredging soil depth for the final removal of heavy metals. Although the emergent plants were minor sinks in comparison with soil, common rush had higher bioconcentration factors and translocation factors for heavy metals than common reed had.

Characterization of temporal variations in landfill gas components inside an open solid waste dump site in Sri Lanka.

A long-term monitoring of composition of landfill gases in the region with high rainfall was conducted using an argon assay in order to discuss air intrusion into the dump site. Gas samples were taken from vertical gas monitoring pipes installed along transects at two sections (called new and old) of an abandoned waste dump site in Sri Lanka. N2O concentrations varied especially widely, by more than three orders of magnitude (0.046-140 ppmv). The nitrogen/argon ratio of landfill gas was normally higher than that of fresh air, implying that denitrification occurred in the dump site. Argon assays indicate that both N2 and N2O production occurred inside waste and more significantly in the old section. The Ar assay would help for evaluations of N2O emission in developing countries. IMPLICATIONS: A long-term monitoring of composition of landfill gases in the region with high rainfall was conducted using an argon assay in order to discuss air intrusion into the dump site. Argon assays indicate that both N2 and N2O production occurred inside waste and more significantly in the old section.

Effect of increasing salinity on biogas production in waste landfills with leachate recirculation: A lab-scale model study.

The effects of salinity on anaerobic waste degradation and microbial communities were investigated, in order to propose an appropriate leachate recirculation process in a waste landfill in a tropical region. A salt concentration of 21 mS cm-1 of electrical conductivity (EC) did not affect waste degradation, but a salt concentration of 35 mS cm-1 of EC inhibited CH4 generation. A higher salt concentration of 80 mS cm-1 of EC inhibited not only CH4 and CO2 generation, but also degradation of organic compounds. The bacterial and archaeal community compositions were affected by high salinity. High salinity can exert selective pressure on bacterial communities, resulting in a change in bacterial community structure. Ammonium caused strong, dominant inhibition of biogas production in the salt concentration range of this study. Quality control, especially of ammonium levels, will be essential for the promotion of waste biodegradation in landfills with leachate recirculation.

Water reduction by constructed wetlands treating waste landfill leachate in a tropical region.

One of the key challenges in landfill leachate management is the prevention of environmental pollution by the overflow of untreated leachate. To evaluate the feasibility of constructed wetlands (CWs) for the treatment of waste landfill leachate in tropical regions, water reduction and pollutant removal by a CW subjected to different flow patterns (i.e., horizontal subsurface flow (HSSF) and free water surface (FWS)) were examined in both rainy and dry seasons in Thailand. A pilot-scale CW planted with cattail was installed at a landfill site in Thailand. With HSSF, the CW substantially removed pollutants from the landfill leachate without the need to harvest plants, whereas with FWS, it only slightly removed pollutants. Under both flow patterns, the CW significantly reduced the leachate volume to a greater extent than surface evaporation, which is regarded as an effect of the storage pond. Additionally, water reduction occurred regardless of season and precipitation, within the range 0-9 mm d(-1). In the case of low feeding frequency, water reduction by the CW with HSSF was lower than that with FWS. However, high feeding frequency improved water reduction by the CW with HSSF and resulted in a similar reduction to that observed with FWS, which exhibited maximum evapotranspiration. In terms of water reduction, with both HSSF in conjunction with high frequency feeding and FWS, the CW provided a high degree of evapotranspiration. However, pollutant removal efficiencies with HSSF were higher than for FWS. The present study suggested that CWs with HSSF and high frequency feeding could be useful for the prevention of uncontrollable dispersion of polluted leachate in the tropical climate zone.

Factors affecting the adsorptive removal of bisphenol A in landfill leachate by high silica Y-type zeolite.

Although bisphenol A (BPA), a representative endocrine-disrupting compound, has been detected frequently in landfill leachate, effective technologies for BPA removal from landfill leachates are limited. We used high silica Y-type zeolite (HSZ-385) for the selective adsorption of BPA from landfill leachate, and factors affecting this adsorption are discussed. Higher removal efficiencies at pH 5.0-9.0 imply that neutral BPA is adsorbed more easily onto HSZ-385 than monomeric or divalent BPA anions. An increase in ionic strength and sodium acetate concentration did not affect BPA adsorption significantly, while the removal efficiency decreased slightly when more than 50 mgC/L of humic acid was added. HSZ-385 was applied to synthetic leachates that simulate the composition of landfill leachate at various degradation stages. In young acidic leachates that contain sodium acetate, the use of HSZ-385 for the adsorptive removal of BPA appears to be more effective than in old alkaline leachates, which contain large amounts of humic acid. In addition, 82 % BPA removal was achieved from young raw leachates using HSZ-385, which demonstrates that selective BPA removal from actual landfill leachate has been achieved.

Microorganisms in landfill bioreactors for accelerated stabilization of solid wastes.

Landfill bioreactors (LBRs) with management of leachate and biogas have presented numerous advantages such as accelerated stabilization of solid wastes, reduced amount of leachate, and in situ leachate treatment. Such advantages have minimized environmental risks, have allowed extension of the useful life of the landfill site, and have fostered cost reduction. LBRs of three types have been developed using both anaerobic and aerobic modes: anaerobic, aerobic, and hybrid. Microorganisms in landfills cause various reactions related with organic fractions and heavy metals. Such functions have been stimulated in LBRs by recirculation of leachate with or without aeration. To date, most studies of microorganisms in LBRs have analyzed bacteria and archaea based on 16S rRNA genes and have analyzed fungi based on 18S rRNA genes from a taxonomical viewpoint. Indicator genes for specific functions in LBRs such as nitrification, denitrification, and methane production have also been monitored. The population dynamics of microorganisms in LBRs have been partially clarified, but the obtained data remain limited because of highly heterogeneous features of solid wastes inside LBRs. Systematic monitoring of microorganisms should be established to improve LBR performance.

Characterization of microorganisms at different landfill depths using carbon-utilization patterns and 16S rRNA gene based T-RFLP.

A borehole core from 20 m depth of a Japanese landfill was characterized chemically and microbially. The borehole core sample was typically divided into 5 waste layers; 2.4-4.0 m, 5.7-8.5 m, 9.25-9.6 m, 9.77-14.9 m, and 15.9-17.86 m depths. The waste layers' ages spanned about 14 years between the bottom and top. Archaeal 16S rRNA gene and eubacterial 16S rRNA gene in the waste samples at their respective levels were 9.8 x 10(5)-7.2 x 10(7) and 1.2 x 10(7)-7.2 x 10(9) copy/g-wet. Similar to populations of viable and culturable bacteria, those populations were high at 7.0 m and 17.5 m depth, but low at 3.0 m depth. The microorganisms' phenotypes and genotypes were evaluated, respectively, using carbon-utilization tests and by eubacterial 16S rRNA gene based T-RFLP. Low dominance of the VFA-utilizing bacteria in samples and low concentrations of VFAs in all waste layers suggest that the organic decomposition in this landfill site remained. Gamma-proteobacteria dominated the microbial community at 17.5 m depth. Clostridia were detected at 7.0, 11.5, and 17.5 m depths, suggesting strict anaerobic conditions in these deep layers. The Shannon-Weaver diversity index showed lower values at 3.0 m and 11.5 m depth with a T-RF pattern. The diversity index calculated from the carbon-utilization pattern increased slightly with depth at the landfill site. The landfill-site waste layers are expected to be mutually isolated and to form unique microbial communities depending on the buried wastes' composition, temperature, moisture content, and pressure inside the landfill.

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.

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.