The reuse of biosludge as an adsorbent from a petrochemical wastewater treatment plant

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 biosludge. The optimal conditions for a larger surface area adsorbent were 3 M ZnCl2-immersed sludge pyrolyzed at 600 degrees 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.     

Seasonal source-receptor relationships in a petrochemical industrial district over northern Taiwan

This study investigated the relationships between meteorological data, pollution sources, and receptors over northern Taiwan. During the intensive sampling period in summer 1992, the weather was controlled predominantly by a Pacific subtropical high and by Typhoon Mark. During the other intensive sampling period in winter 1993, while a cold frontal system approached Taiwan, the northeasterly winds prevailed most of the time. The local circulation such as land-sea breeze only developed under weak synoptic environment. Particle concentrations and element composition in winter were higher than in summer. This can be attributed to the high convection of air mass, which leads to the vertical dispersion of pollutants in summer. In addition to the subtropical high pressure, typhoons are frequently accompanied with high-wind speeds and unstable weather conditions that also dilute and eliminate the pollutants. In winter, the prevailing northeasterlies might carry pollutants from Midland China. Furthermore, the anticyclone system develops a stagnant condition that easily leads to pollutant accumulation. In this case, the wind direction affected the source contribution of the receptor and the PM10 displays a higher correlation with coarse and fine particulate than meteorological parameters in summer. In addition, the mixing height shows a high correlation with PM10 in winter.     

Abundance and sources of ambient dioxins in Hong Kong: a review of dioxin measurements from 1997 to 2001

Ambient measurements of seventeen 2,3,7,8-polychlorinated dibenzo-p-dioxin/dibenzofuran congeners (2,3,7,8-PCDD/Fs) have been taken in a number of monitoring programs or ad-hoc studies in Hong Kong. The longest monitoring program started at two locations in the territory in July 1997. The other monitoring efforts are ad-hoc studies, varying from a few coordinated sampling events at multiple sites to a year-long monitoring project that targeted suspected local dioxin sources. In this paper, we examined these measurements to understand the ambient levels, temporal and spatial variation, and possible sources of the 2,3,7,8-PCDD/Fs in Hong Kong. The territory-wide annual average concentration of the dioxins was 0.052 pg I-TEQ/m3 measured at the regular monitoring stations in the most recent annual cycle of 2000/2001. This level fell at the lower end of the range of dioxin concentrations measured at other urban locations around the world. The dioxin levels showed a clear seasonality in that elevated concentrations were observed in the winter and lower concentrations in the summer at all monitoring sites with one year or more regular measurements. The measurements indicated that the few known local dioxin sources, including a major chemical waste incinerator facility, landfill sites, and vehicular traffic, are not important contributors to ambient dioxins in Hong Kong. On days of high dioxin concentrations, the 2,3,7,8-PCDD/F congeners were observed to have almost identical compositions with a north-northwest to south-southeast spatial gradient in concentrations at different sampling locations in Hong Kong. This observation, along with other collaborative evidence, established a strong link between high dioxin concentration days in Hong Kong and regional transport of the polluted air masses from the north.     

Investigation of Mtbe and Aromatic Compound Concentrations at a Gas Service Station

Methyl tert-butyl ether (MTBE) has been used as a fuel additive at levels of 2–11% in Taiwan for the past decade. The purpose of this additive is to enhance the octane, replace the use of lead-based anti-knock gasoline additives and reduce aromatic hydrocarbons. However, it is possible that oxygenated fuel has a potential health impact. To determine the air quality impact of MTBE, measurements were made of ambient MTBE and other gasoline constituents at a service station. Additionally, environmental conditions (wind speed, wind direction, and temperature, etc.) that could affect concentrations of emission constituents were measured. Gas samples were analyzed for target MTBE and volatile organic compounds, e.g., benzene and toluene. Ambient samples were collected using Tenax adsorbent tubes for mass spectrometric analysis at a service station located in Changhua County, Taiwan. The resulting measured ambient air concentrations were compared with Taiwans regulatory standards for hazardous air pollutants. Subsequently, the factors controlling the formation of high-VOC levels at the service station and in the residential neighborhoods were identified. Additionally, the results can provide the Environmental Protection Agency (EPA) of Taiwan with useful information and prompt them to mandate this gas service station to install a refueling vapor recovery system.     

Respirometric Evaluation by Graphical Analysis for Microbial Systems

Analysis of respirometric graphs for system diagnosis has recently drawn much attention due to the nature of the test being a fast method with reliable oxygen uptake (Ou) data. In this study, a new graphical analysis procedure is proposed, using the oxygen uptake rate (OUR) vs. Ou respirogram because of its distinct characteristics that provides easy visual inspection. The OUR plot is typically divided into two respiration phases, and each one of these phases can be simulated by a previously derived analytical equation. Based on the 2-phase model, five characteristic parameters (CPs) were derived for the OUR respirogram. Mathematically the 5 CPs can be related to the system parameters (SPs), including the four Monod kinetic parameters and two operating conditions (initial substrate and biomass concentration). Sensitivity analyses were then conducted to assess the 5 CPs for the level of effect caused by system parameters (SPs). This study also conducted respirometric tests under batch operation to evaluate the applicability of the graphical analysis method. Based on the 5 CPs estimated from the OUR respirogram of the tests, it can be concluded that respirometric tests normally experience the problems associated with initial lag, non-uniform seeding, and inadequate mixing.     

The adsorption of benzene and methylethylketone onto activated carbon: thermodynamic aspects.

The adsorption of volatile organic compounds (VOCs), exemplified by benzene and methylethylketone (MEK), onto seven different types of activated carbon was investigated. Results show that for benzene adsorption the adsorption characteristic energy, enthalpy, free energy and entropy are in the range 17.12-36.86, -20.8 to -44.7, -11.89 to -16.22 kJ/mole and -29.4 to -85.3 J/mole/K, respectively. For the adsorption of MEK, the adsorption characteristic energy, enthalpy, free energy and entropy are in the range 14.47-32.34, -18.3 to -40.8, -10.78 to -15.56 kJ/mole and -24.8 to approximately -60.3 J/mole/K, respectively. The adsorption enthalpy can be calculated indirectly from statistical thermodynamic method and directly from the immersion enthalpy method. The adsorption characteristic energy is calculated by the Dubinin-Astokhov equation. The free energy is calculated by the measured equilibrium adsorption constant.     

Monitoring spatio-temporal variation in molluscan grazing pressure in seasonal, tropical rock pools

In Hong Kong, low-shore rock pools support a patchy mosaic of different successional stages of crustose coralline algae. Echinoid and molluscan grazers are abundant in these low-shore rock pools and spatial and temporal variation in grazing pressure is thought to play an important role in structuring these assemblages. Direct records of graze marks using a modified wax-disc method were used to monitor spatial (different pools) and temporal (periods, 3 or 4 days each; spring vs. neap tides; summer vs. winter) variations in grazing pressure. Radula marks of Chlorostoma argyrostoma, Lunella coronata and Nerita albicilla were common in all pools. Grazing pressure was highly variable with tidal state and season but also within these two factors. Lunella and Nerita exerted highest grazing pressure at neap tides during summer, whilst Chlorostoma exerted highest grazing pressure in winter. Although overall patterns of temporal variation were similar and consistent in all pools, there was between pool variation in grazing pressure and individual species showed different patterns. Within the seasonal and tidal variations, large period-to-period differences were found for all species, illustrating small-scale temporal variation. Fine-scale spatial and temporal patterns of variation in grazing pressure of different species, therefore, contribute to the highly dynamic nature of these low-shore rock pools.     

Microbial dechlorination of 2,4,6-trichlorophenol in anaerobic sewage sludge

The dechlorination of 2,4,6-trichlorophenol (TCP) in municipal sewage sludge with a chlorophenol (CP)-adapted consortium was investigated. Results show that dechlorination rates differed according to the source of the sludge samples used in the batch experiments. No significant differences in 2,4,6-TCP dechlorination were observed following treatment with inoculum at densities ranging from 10% to 50% (V/V), but a significant delay was noted at 5% (V/V) density. Overall, results show that the higher the 2,4,6-TCP concentration, the slower the dechlorination rate. The addition of acetate, lactate, pyruvate, vitamin B12 or manganese dioxide did not results in a significant change in 2,4,6-TCP dechlorination. Data collected from a bioreactor experiment revealed that pH 7.0 and a total solid concentration of 10 g/L were optimal for dechlorination. Dechlorination rates decreased significantly at higher agitation speeds. 2,4,6-TCP dechlorination was enhanced under methanogenic conditions, but it was inhibited under denitrifying and sulfate-reducing conditions.     

Reusing pretreated desulfurization slag to improve clinkerization and clinker grindability for energy conservation in cement manufacture

The purpose of this study was to combine the physical pretreatments of grinding, sieving, and magnetic-separation processes to reclaim iron-rich materials from the desulfurization slag, and to use the remainder for cement clinker production. The iron-rich materials can be separated out efficiently by grinding for 30 min and sieving with a 0.3 mm mesh. The non-magnetic fraction of the particles smaller than 0.3 mm was in the majority, and proved to be suitable for use as a cement raw material. The raw mixes prepared with a pretreated desulfurization slag had a relatively high reactivity, and the temperature at which alite forms was significantly reduced during the clinkerization process. The clinkers produced with 10% desulfurization slag had a high level of alite and good grindability. Generally, the improvements in clinkerization and clinker grindability are beneficial to energy conservation in cement manufacture.