Influences of adding easily degradable organic waste on the minimization and humification of organic matter during straw composting

To find a better composting process with low greenhouse gas emission and high humus production, the effect of adding kitchen waste on reduction and humification of organic matter during straw composting was studied. Three processes were compared, consisting of different ratios of straw and kitchen waste (1:2, 1:1, and 2:1). At four time points over a 62-d incubation, the reduction and humification of compost was evaluated by measuring the total mass, carbon content, and humic material content of the compost. Treatment 1 (straw/kitchen waste ratio of 1:2) reduced the total mass of compost the most. Treatment 2 (straw/kitchen waste ratio of 1:1) reduced the total carbon content the most, reflecting the highest emission of greenhouse gas. Treatment 3 produced the most humic acid material and released the lowest amount of carbon. Hence, from the point of view of reducing greenhouse gas emissions and increasing stable organic matter such as humus and humic acid during composting, treatment #3 was optimal. The three treatments resulted in significant differences in microbial biomass and enzyme activity during composting. The highest amount of active microbial biomass was associated with the largest reduction in compost mass (treatment 1). Higher proportions of straw (treatments 2 and 3), which contains more lignin, were associated with greater β-glycosidase activity, which may generate more humus that can improve soil quality. Dehydrogenase activity seemed to be the most important microbial factor in organic carbon catabolism or humification.     

Exceedances of the National Ambient Air Quality Standard for Ozone Occurring at a “Pristine” Area Site

Abstract

This paper presents a comparative study of the biodegradation of three aromatic volatile compounds in a compost-based biofilter: toluene, xylene, and 1,2,4-trimethyl-benzene, used in the course of this work for the first time in the field of biofiltration. Hence, three identical biofiltration units have been operated at the laboratory scale. During the experiments, nitrogen (as urea) was supplied at various concentrations to each reactor, via irrigated nutrient solutions. A comparative analysis of the results showed that the biodegradability scale followed the degree of substitution around the aromatic ring: toluene > xylene > trimethylbenzene, with 95, 80, and 70% maximum conversions, respectively. In addition, and despite the different removal levels achieved in the three biore-actors, it was established that from a reaction viewpoint, the degradation of the three compounds seemed to follow similar metabolic pathways involving methylcatechol isomers. Finally, by varying the nitrogen input concentrations in the three reactors, three degradation regimes have been highlighted: an N-limitation regime and an N-optimum regime, common to the three solvents, and an N-excess regime, favorable to the colonization of the filter beds by nitrifying species, which particularly affected the xylene and trimethylbenzene biodegradation.     

NOx Removal with Combined Selective Catalytic Reduction and Selective Noncatalytic Reduction: Pilot-Scale Test Results

Pilot-scale tests were conducted to develop a combined nitrogen oxide (NO_x) reduction technology using both selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR). A commercially available vanadium- and titanium-based composite honeycomb catalyst and enhanced urea (NH₂CONH₂) were used with a natural-gas-fired furnace at a NO_x concentration of 110 ppm. Changes in SNCR chemical injection temperature and stoichiometry led to varying levels of post-furnace ammonia (NH₃), which acts as the reductant feed to the downstream SCR catalyst. The urea-based chemical could routinely achieve SNCR plus SCR total NO_x reductions of 85 percent with less than 3 ppm NH₃ slip at reductant/NO_x stoichiometries ranging from about 1.5 to 2.5 and SCR space velocities of 18,000 to 32,000 h^?1. This pilot-scale research has shown that SNCR and SCR can be integrated to achieve high NO_x removal. SNCR provides high temperature reduction of NO_x followed by further removal of NO_x and minimization of NH₃ slip by a significantly downsized (high-space velocity) SCR.     

The Relationship between the Quantity of Heavy Metal and PAHs in Fly Ash

ABSTRACT

Heavy metal and polycyclic aromatic hydrocarbons (PAHs) in flue gas have received considerable attention in recent years due to their mutagenic or carcinogenic properties. The present study is carried out to investigate the influence of the quantity of heavy metals on PAHs formation in fly ash.

A fluidized bed incinerator was used in this experiment to obtain fly ash of chemical similarity by incinerating various compositions of waste. The obtained fly ash, both with and without heavy metal, were used to adsorb the PAHs in the flue gas and to investigate the formation of PAHs in fly ash. The results indicate that carbon and heavy metals most greatly influence the formation of PAHs in the fly ash. Carbon is absorptive; heavy metals encourage not only absorption of PAHs but also catalyze PAHs formation.     

Inorganic Acid Emission Factors of Semiconductor Manufacturing Processes

Abstract

A huge amount of inorganic acids can be produced and emitted with waste gases from integrated circuit manufacturing processes such as cleaning and etching. Emission of inorganic acids from selected semiconductor factories was measured in this study. The sampling of the inorganic acids was based on the porous metal denuders, and samples were then analyzed by ion chromatography. The amount of chemical usage was adopted from the data that were reported to the Environmental Protection Bureau in Hsin-chu County according to the Taiwan Environmental Protection Agency regulation. The emission factor is defined as the emission rate (kg/month) divided by the amount of chemical usage (L/month). Emission factors of three inorganic acids (i.e., hydrofluoric acid [HF], hydrochloric acid [HQ], and sulfuric acid [H₂SO₄]) were estimated by the same method. The emission factors of HF and HCl were determined to be 0.0075 kg/L (coefficient of variation [CV] = 60.7%, n = 80) and 0.0096 kg/L (CV = 68.2%, n = 91), respectively. Linear regression equations are proposed to fit the data with correlation coefficient square (R²) = 0.82 and 0.9, respectively. The emission factor of H₂SO₄, which is in the droplet form, was determined to be 0.0016 kg/L (CV = 99.2%, n = 107), and its R² was 0.84. The emission profiles of gaseous inorganic acids show that HF is the dominant chemical in most of the fabricators.     

Analysis of a Summertime PM2.5 and Haze Episode in the Mid-Atlantic Region

Abstract

Observations of the mass and chemical composition of particles less than 2.5 μm in aerodynamic diameter (PM_2.5), light extinction, and meteorology in the urban Baltimore-Washington corridor during July 1999 and July 2000 are presented and analyzed to study summertime haze formation in the mid-Atlantic region. The mass fraction of ammoniated sulfate (SO₄ ^2-) and carbonaceous material in PM_2.5 were each ～50% for cleaner air (PM_2.5 < 10 μg/m³) but changed to ～60% and ～20%, respectively, for more polluted air (PM_2.5 > 30 μg/m³). This signifies the role of SO₄ ^2- in haze formation. Comparisons of data from this study with the Interagency Monitoring of Protected Visual Environments network suggest that SO₄ ^2? is more regional than carbonaceous material and originates in part from upwind source regions. The light extinction coefficient is well correlated to PM_2.5 mass plus water associated with inorganic salt, leading to a mass extinction efficiency of 7.6 ± 1.7 m²/g for hydrated aerosol. The most serious haze episode occurring between July 15 and 19, 1999, was characterized by westerly transport and recirculation slowing removal of pollutants. At the peak of this episode, 1-hr PM_2.5 concentration reached ～45 μg/m³, visual range dropped to ～5 km, and aerosol water likely contributed to ～40% of the light extinction coefficient.     

The Reuse of Biosludge as an Adsorbent from a Petrochemical Wastewater Treatment Plant

Abstract

Biosludge was obtained from a petrochemical industry’s biological wastewater treatment plant. Zinc chloride (ZnCl₂) was used as a sludge activation agent during the pyrolytic process. Scanning electron microscope (SEM) image photographs, element composition, surface functional group, and pore structure were analyzed for the sludge adsorbent characteristics. Results indicated the proper ZnCl₂-immersed concentration, pyrolytic temperature, and time could produce adsorbent from the bio-sludge. The optimal conditions for a larger surface area adsorbent were 3 M ZnCl₂-immersed sludge pyrolyzed at 600 °C for 30 min and washed with 3 N hydrochloric acid (HCl) solution and distilled water. The predominant pore size of the sludge adsorbent was the mesopore.     

Decomposition of SF6 in an RF Plasma Environment

Abstract

Sulfur hexafluoride (SF₆)-contained gas is a common pollutant emitted during the etching process used in the semiconductor industry. This study demonstrated the application of radio-frequency (RF) plasma in the decomposition of SF₆. The decomposition fraction of SF₆ [η_SF6 (C_in–C_out)/C_in x 100%] and the mole fraction profile of the products were investigated as functions of input power and feed O₂/SF₆ ratio in an SiO₂ reactor. The species detected in both SF₆/Ar and SF₆/O₂/Ar RF plasmas were SiF₄, SO₂, F₂, SO₂F₂, SOF₂, SOF₄, S₂F₁₀, S₂OF₁₀, S₂O₂F₁₀, and SF₄. The results revealed that at 40 W, η_SF6 exceeded 99%, and the reaction products were almost all converted into stable compounds such as SiF₄, SO₂, and F₂ with or without the addition of oxygen. Sulfur oxyfluorides such as SO₂F₂, SOF₂, SOF₄, S₂OF₁₀, and S₂O₂F₁₀ were produced only below 40 W. The results of this work can be used to design a plasma/chemical system for online use in a series of a manufacturing process to treat SF₆-containing exhaust gases.     

Hydrothermal treatment for inactivating some hygienic microbial indicators from food waste–amended animal feed

To achieve the hygienic safety of food waste used as animal feed, a hydrothermal treatment process of 60–110 °C for 10–60 min was applied on the separated food waste from a university canteen. Based on the microbial analysis of raw waste, the inactivation of hygienic indicators of Staphylococcus aureus (SA), total coliform (TC), total aerobic plate counts (TPC), and molds and yeast (MY) were analyzed during the hydrothermal process. Results showed that indicators' concentrations were substantially reduced after hydrothermal treatment, with a greater reduction observed when the waste was treated with a higher temperature and pressure and a longer ramping time. The 110 °C hydrothermal treatment for 60 min was sufficient to disinfect food waste as animal feed from the viewpoint of hygienic safety. Results obtained so far indicate that hydrothermal treatment can significantly decrease microbial indicators' concentrations but does not lead to complete sterilization, because MY survived even after 60 min treatment at 110 °C. The information from the present study will contribute to the microbial risk control of food waste–amended animal feed, to cope with legislation on food or feed safety.

Implications: Reduction of microbial indicators at ramping time and holding time during the hydrothermal process showed that hydrothermal treatment is an effective method to achieve hygienic feed from food waste to a certain extent, but the conditions researched in this study were not enough for the complete sterilization of food waste, because of the different heat resistance of bacteria and spores.