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The incineration of municipal solid waste has been important in waste management, but it raises another environmental issue concerning residue treatment. This study describes an innovative use of naturally aged incineration bottom ash (AIBA) as an alternative substrate for horizontal subsurface flow (HSSF) constructed wetlands (CW). Although experimental results from a period lasting for 396 days only revealed slightly higher removal ratios in HSSF with AIBA (HSSF-E) than in HSSF-traditional pebble beds (HSSF-C), increasing from 67% to 76% for BOD, 44%-51% for TKN, 47%-54% for NH

To investigate the impact of salinity on the pollution removal performance of constructed wetlands (CWs), four sets of hybrid CWs (HCW) were considered herein. The HCWs were composed of free water surface flow (FWS) and subsurface flow (SSF) CWs that were planted with cattail (Typha orientalis Presl.) and reed (Phragmites communis Trin.), respectively. After a preliminary experiment of almost seven months with influent fresh wastewater, NaCl was added at concentrations of 5 ppt, 10 ppt, and 20 ppt to simulate the impact of salinity. The removal performance was compared with that of the control CWs, and the impact of salinity on FWS CWs, SSF CWs, and HCWs were investigated. According to the experimental results, the biochemical oxygen demand (BOD) removal ratio in FWS CWs decreased from 70.3% to 58.3% as salinity increased from 0 ppt to 20 ppt, while that in SSF CWs fell significantly from 53.5% to 36.9% as salinity increased to ≧10 ppt. However, hybrid CWs offered more stable BOD removal and ammonia-nitrogen (NH3-N) removal under salinity impact. Salinity≧10 ppt stimulated the removal performance of NH3-N in FWS CWs to 19.4% while salinity≦5 ppt had no significant effect. In SSF CWs, a linear relationship was observed between removal loading and salinity, and NH3-N removal completely ceased at a salinity of 30.6 ppt. All removal ratios of NO3─-N>94.9% in FWS CWs revealed that salinity had almost no impact because the environment was anaerobic and contained sufficient organic carbon. The TP removal ratio in FWS CWs decreased from 14.7% to 9.2% as salinity increased from 0 ppt to 20 ppt and that in SSF CWs decreased monotonically from 7.2% to −0.2%. The impact period of salinity showed versatile reaction patterns of pollution removals in FWS CWs, SSF CWs, and HCWs. It distributed from 28 days to 186 days, after which the removal performance of CWs was restored.

An external aeration and intermittent circulation were used to improve the nitrogen removal performance of subsurface flow constructed wetland (SSF CW) in landscape garden ponds. Nitrification was the main mechanism of ammonium–nitrogen ( N H 4 + N ) removal and partial nitrification/anaerobic ammonia oxidation was a minor process. Field measurements yielded a removal rate of N H 4 + N of 0.266–0.566 g N/d m2 and a corresponding temperature-dependent rate constant of 0.184 d−1 to 0.377 d−1 representing an improvement over nitrogen removal. The nitrate–nitrogen ( N O 3 − N ) removal was degraded to the background level of N O 3 − N concentration in an environment with a high concentration of dissolved oxygen. The N O 3 − N removal rate ranged from 0.0393 g N/d m2 to 0.0825 g N/d m2 and resulted from aerobic denitrification, indicating that external aeration and intermittent circulation effectively improved oxygen transportation in SSF CW. This could remove N O 3 − N of the effluent of SSF CW when using in-tank aeration to improve the nitrogen removal performance of SSF CW.

Selective reduction of nitrate over nanoscale zero–valent iron (nFe0) modified metals (Pd and Cu) was investigated. Parameters of modified metal loading, metallic ratio (Pd:Cu), and H2 gas supplying were investigated on the influence of nitrate reduction. Metal (Cu, Pd) deposited onto nanoiron was proven to be effective in promoting the formation of nitrogen gas and, on the other hand, suppressing the NH4+ formation. Hydrogen gas feeding appeared to have a synergistic effect on nitrate removal and on nitrogen gas selectivity in all types of catalytic reductants. A catalyst with a loading of 10% of (Pd–Cu)–nFe0 with a ratio of Pd:Cu of 2:1, and H2 feeding showed the highest selective to N2: NH4+ formation (51:42), compared to the others ((Cu–Pd)–nFe0, Cu–nFe0, Pd–nFe0 and nFe0). The significant improvement in initiating the formation of N2, on the other hand suppressing the formation of NH4+, was referred to an indirect electron–transferring process of nFe0 to Cu and to Pd, consequently. In addition, kinetic evaluations on each catalyst was evaluated and used to postulate the selective reduction of nitrate phenomena.

The pollutant removal performance of traditional horizontal subsurface flow (HSSF) constructed wetlands (CWs) is limited because of the dissolved oxygen (DO) supply is insufficient. The aeration of HSSF CWs usually improves their pollutant removal performance, but a high DO induces the accumulation of nitrate-nitrogen (NO3−-N) and suppresses the improvement of total nitrogen (TN) removal. In this study, an integrated solution that involved in-tank front aeration and internal recirculation (FAIR) was used to improve the pollutant removal performance of HSSF CWs. Based on the experimental results, the FAIR system significantly increased the removal efficiencies of biochemical oxygen demand (BOD) from 53.8–76.0% to 82.0–91.7% and reduced the BOD concentration in the effluent to below 10 mg L−1. The removal efficiency of ammonia-nitrogen (NH3–N) increased from 15.1–78.3% to 98.5–98.6% while the removal efficiencies of the total Kjeldahl nitrogen (TKN) of the control and FAIR HSSF CWs were 18.2–77.1% and 93.5–94.3%, respectively. HSSF CWs with FAIR outperformed aerated HSSF CWs in the removal of NH3–N and TKN. The effects of two recirculation flow ratios (Rr = recirculation flow rate/influent flow rate), 14.3 and 3.0, on the improvement of pollutant removal performance were investigated. The lower Rr did not significantly affect the improvement of BOD, NH3–N, and TKN, but a higher Rr resulted in more severe accumulation of NO3−-N. The removal efficiency of TN in control HSSF CWs ranged from 20.4% to 75.5%, and in the FAIR HSSF CW was 71.6% for Rr = 14.3 and 81.3% for Rr = 3.0. However, the FAIR system did not enhance the removal performance of total phosphorus, suggesting that the DO level and internal recirculation were not dominant mechanisms for the removal of phosphorous. The easy maintenance of the FAIR system made it a superior modification for improving the pollutant removal performance of HSSF CWs.

Despite the widespread use of constructed wetland, the parameters of its design and their operational related parameters have not yet been clearly defined. In free water surface (FWS) flow constructed wetland (CW), emergent vegetation is a primary component in pollutant removals that alters the porosity and flow pattern of water. Based on tracer experiments in a physical model, this study investigates how porosity affects hydraulic performance parameters. Experimental results indicate that, at a rather low hydraulic loading rate (HLR), the mean residence time () decreases with decreasing porosity (ϵ). When the static and dynamic effects are balanced, the relation between ϵ and becomes neutral at a high HLR. However, the Reynolds number (NR) can accurately predict . A rather high coefficient of multiple determination for the proposed model is 0.985. This study also investigates, how the number of tanks-in-series (N) under various porosities influences the flow pattern. When vegetation is lacking, N...

To establish an empirical model for predicting a lower heating value (LHV) easily and economically by multiple regression analysis. A wet-based physical components model (WBPCM) was developed and based on physical component analysis without dewatering. Based on 497 samples of municipal solid waste (MSW) gathered from 14 incinerators in western parts of Taiwan from 2002 to 2009. The proposed model was verified by independent samples from other incinerators through parameters multiple correlation coefficients (R), relative percentage deviation (RPD) and mean absolute percentage error (MAPE). Experimental results indicated that R, RPD and MAPE were 0.976, 17.1 and 17.7, respectively. This finding implies that LHV predicted by the WBPCM could well explain the LHV characteristics of MSW. The WBPCM was also compared with existing prediction models of LHV on a dry basis. While more accurately predicting LHV predicting than those models based on proximate analysis, the WBPCM was comparable with models based on physical component analysis in term of RPD and MAPE. Experimental results further indicated that the prediction accuracy of the WBPCM varied with MSW moisture parabolically. No specific relation was observed in the results of the previous prediction model. The accuracy of the WBPCM was almost approached to that of ultimate analysis in moisture ranging from 40% to 55%. The model was applicable within this moisture range. We conclude that the WBPCM is a faster and more economical model for LHV predictions with comparable accuracy than those models based on physical component analysis. The proposed WBPCM is highly promising for use in designing and operating incinerators.

This study attempted to purify eutrophic landscape water under a low pollutant concentration and high hydraulic volume loading using an embedded subsurface flow (SSF) constructed wetland (CW). Three species of aquatic plants (i.e., Cyperus alternifolius subsp. flabelliformis, Canna indica, and Hydrocotyle verticillata) were found to be conducive to the requirements of purifying the low-polluted water. Field results of nearly 2 years of experiments showed that SSF CW purified the eutrophic water and maintained the landscape water in a visibly clear condition. In an environment approaching the SSF CW background concentration, pollutant removal processes were divided into modulation and optimum performance periods. Average concentrations of biochemical oxygen demand (BOD), ammonium–nitrogen (NH4 +–N), and total phosphorous (TP) in the optimum performance period were 0.69–1.00, 0.35–1.42, and 0.19–0.23 mg/L, respectively. Almost 500 days of BOD and NH4 +–N removals were necessary to perform optimally. A shorter period, 350 days, was required for TP optimum removal. This feature of two stage removals was not found in chlorophyll-a (Chl-a) and suspended solids (SS), whose averages were 11.86–17.98 and 13.30 μg/L, respectively. Filter cleaning and water replacement were unnecessary, while only water recharging was needed to compensate for the water lost by evapotranspiration. The field SSF CW has maintained its performance level for over 7 years.

This paper uses the Singapore and the Thailand's stock prices of material from January 4, 2000 to July 20, 2007, discussing the model construction and their associations of between Singapore and Thailand's stock markets, and also uses Student's t distribution to analyze the proposed model. The empirical results show that the mutual affects of the Singapore and the Thailand's stock markets may construct in bivariate IGARCH (1, 1) model with a DCC. The empirical result also shows that between Singapore and Thailand's stock market returns exists the positive relations- namely two stock market return's volatility are synchronized influence, the average estimation value of the DCC coefficient of two stock market returns equals to 0.3876. Also, Singapore and Thailand's stock markets do not have the asymmetrical effect in the research data period. These evidences may suggest stock market investors or international fund managers- before investing in Singapore must consider the Thailand stock price return's volatility risk and its connection. Therefore, in the stock market, investors and managers may not neglect the influence of the foreign country's stock market return volatility behavior; otherwise, his decision will not achieve the anticipated effect.

A multiple regression analysis was used to develop two predictive models of lower heating value (LHV) for municipal solid waste (MSW), using 180 samples gathered from cities and counties in Taiwan during 2001-2002. These models are referred to as the original proposed model (OPM) and the simplified model (SM). The coefficients of multiple determinations for the OPM and SM were 0.983 and 0.975, respectively. To verify the feasibility of the models, a demonstration program based on sampling of MSW in Kaohsiung City was conducted. As a result, the OPM showed superior precision in terms of relative percentage deviation (RPD) and mean absolute percentage error (MAPE), when compared to the conventional models based on the proximate analysis, physical composition and ultimate analysis. The SM was derived by neglecting the three minor physical components used in the OPM. The resulting SM was less precise when compared to the OPM, but it was still acceptable, with a precision level better than the conventional models. It was concluded that the predictability of empirical models could be improved significantly through selection of the appropriate physical components and multiple regression analysis.

Taiwan is a densely populated and developed country with more than 97% of energy consumption supplied by imported fuels. Greenhouse gas emissions are thus becoming significant environmental issues in the country. Using the Intergovernmental Panel on Climate Change (IPCC) recommended methodologies, anthropogenic emissions of nitrous oxide (N 2 O) in Taiwan during 2000–2003 were estimated to be around 41 thousand metric tons annually. About 87% of N 2 O emissions come from agriculture, 7% from the energy sector, 3% from industrial processes sector, 3% from waste sector. On the basis of N 2 O emissions in 2000, projections for the year 2010 show that emissions were estimated to decline by about 6% mainly due to agricultural changes in response to the entry of WTO in 2002. In contrast to projections for the year 2020, N 2 O emissions were projected to grow by about 17%. This is based on the reasonable scenario that a new adipic acid/nitric acid plant will be probably started after 2010.