Preparation, characterisation and testing of photocatalytic polymeric membranes with entrapped or suspended TiO2

Various cellulose triacetate (CTA) or polysulfone (PSf) membranes with entrapped polycrystalline TiO₂ were prepared by using different methods of the so-called phase inversion process. Porosity and permeability of the membranes increased by increasing the amount of entrapped TiO₂ while rejection decreased. The photoactivity of entrapped TiO₂ for the degradation of congo-red was compared with that of the same quantity of suspended TiO₂ and the results indicated that TiO₂ was always more efficient when used in suspension. A hybrid configuration consisting of a continuous membrane photoreactor with the photocatalyst in suspension showed to be the most promising one.     

Nitrification of centrate from dewatering of anaerobically digested sludge

Nitrification of anaerobically digested sludge centrate was studied in bench-scale suspended growth and fixed film enhanced suspended growth systems at temperatures of 10.5-28.5°C and pH values of 6.0-9.1. Nitrification followed zero-order kinetics in both systems, and ammonia removals in excess of 99% were observed. The temperature dependency of the suspended growth nitrification rate observed under not fully acclimated biomass conditions at pH between 6.8 and 8.5, was expressed as k_T = k₂₀θ^T-20where k₂₀ and θ were found to be 0.34 mg NH₃-N/MLVSS-d and 1.033, respectively. The nitrification rate in the fixed film enhanced suspended growth system involving styrofoam pads ranged from 0.11 to 0.13 mg NH₃-N/mg MLVSS-d at temperatures of 21.5-25°C and pH values of 7.8-8.6. The process contained suspended solids in the range of 10-20 mg/l.     

Total scatter-to-backscatter ratio of aerosol derived from aerosol size distribution measurement

Based on in-situ aerosol size-distribution measurements and Mie scattering theory, total scattering coefficients and backscattering coefficients were calculated to derived wavelength dependent lidar ratio S for 355 nm and 532 nm. Effective radius and C/F ratio of aerosol are also calculated to study the relationships between lidar ratio and particle size dependences. The results show backscatter-related scattering properties are more sensitive to coarse mode particle than total scattering. The mean values of lidar ratio for 355 nm and 532 nm are 31.9 ± 6.2 sr and 40.5 ± 6.1 sr respectively, and S₃₅₅ and S₅₃₂ are linear correlated for S₃₅₅ < 50 sr. S₃₅₅ is highly correlated with effective radius of aerosol, and S₅₃₂ is highly correlated with volume C/F ratio.     

Sampling errors in the study of acid gases and anion species in atmospheric aerosols

Atmospheric acid aerosols were sampled by two annular denuder systems (ADS) and a micro-orifice uniform deposit impactor (MOUDI) at a traffic site in central Taiwan. Theoretical analysis showed that the relative artifact for HNO₃ gas sampling was about 0.53 when the initial HNO₃ concentration was under 0.2 µg/m³ and should be considered carefully. The concentrations of gaseous acid at the traffic sampling site were higher than those in the other study. The size distributions of acid aerosols were unimodal for Cl^-, NO₂^-, and NO₃^-, and bimodal for SO₄^2-. The dominant acid ions in particles less than 18 µm were SO₄^2-, NO₃^-, NO₂^- and Cl^-.     

Air pollution at the Bily Kriz mountains in the Czech Republic

An evaluation of air pollution at the Bily Kriz mountains in the Czech Republic is given. Annual daily concentrations of sulphur dioxide (SO₂), nitrogen oxides (NO_x), particulate matter of size 10 mm (PM₁₀) and ozone (O₃) measured in the years 1994–2000 are presented. Air pollution at Bily Kriz is assessed with the reference to the European Union Directives and the standards adopted by the Czech Republic. In general, the concentrations of air pollutants were lower in 1996 for ozone and decreased for SO₂, NO_x and PM₁₀ from 1994. The daily values of SO₂ and PM₁₀ exceeded the European Union limits in approximately 0.0% and 5.5% of cases, respectively. The values of ozone exceeded the limits for the considered period.     

An ozone climatology: relationship between meteorology and ozone in the Southeast USA

A statistical analysis of ozone (O₃) concentrations and meteorological parameters was performed to determine the relationship between meteorological changes and ambient O₃ concentrations in the Southeast United States. The correlation between average daily maximum O₃ concentration and various meteorological variables was analysed on a monthly basis from April through October during 1980-1994. The correlations were strongest during the summer months, particularly June, July, and August. Analysis of long term O₃ concentration trends indicates increasing trends during the 1980s and decreasing trends during the early 1990s.     

Biodegradation of hydrogen sulphide by inoculated Rhodococcus sp.zw11 in a pilot-scale biotrickling filter

A strain of autotrophic micro-organism, Rhodococcus sp.zw11, was isolated from pharmaceutical wastewater containing hydrogen sulphide (H₂S). The shape, physiological and biochemical characteristics and oxidation capacity of Rhodococcus sp.zw11 were studied, and the effect of inlet concentration and volumetric loading of H₂S on the removal efficiency was evaluated by the biotrickling filter inoculated with Rhodococcus sp.zw11. The results suggested that the optimal temperature of Rhodococcus sp.zw11 (aerobic bacilli, short rod and gram-negative) was from 20°C to 28°C and the optimal pH was from 5.5 to 6.5. The criteria necessary for a scale-up design of the biotrickling filter were established, and pressure drops at the start and end of the experiment were investigated. The optimal inlet loading could be noted as 180 g/m³h, corresponding to H₂S removal efficiency close to 100%. Furthermore, the inoculated biotrickling filter had good ability to resist shock loading, which was a potential industrialisation method to control H₂S emissions.     

The effects of different aeration patterns on aerobic granulation

In this study, the effects of aeration patterns in terms of intra- (S1) and extra- (S2) aeration on aerobic granulation were investigated. Granules developed in S1 were retarded due to the high shear force of highly mixed air bubbles, and they were more solid while the S2 granules were porous with many distinct pores and channels. Mature granules in two series had comparable specific oxygen uptake rate and ammonium-nitrogen uptake rate, which were 37.57 and 39.64 mg O₂/(gMLSS ⋅ h), 6.44 and 4.03 mg NH₃-N/ (gMLSS ⋅ h) respectively. Moreover, S1 granules contained more extracellular polymeric substances and higher exopolysaccharide content, which resulted higher negative charges.     

Annual simulation of secondary pollution over northern Italy

A secondary pollution modelling system for simulating airborne dispersion and chemical reactions is applied over a regional scale domain located in the North-West of Italy, where urban and industrial areas are present. It was found an overestimation of NO₂ in the urban areas, probably due to an underestimation of the vertical diffusivity; the analysis of O_X confirms that the discrepancies in O₃ and NO₂ are mainly due to local scale effects; the model shows a general underestimation of the observed PM10 concentrations due to the uncertainties in the emission inventories, spatial resolution, and the adopted aerosol modelling approach.     

Treatment of reactive dyes and textile finishing wastewater using Fenton's oxidation for reuse

Fenton's oxidation (FO) was used to decolourise and degrade some reactive dyes (Remazol Black 5, Remazol Red, Remazol Blue, Remazol Yellow) and raw textile finishing industry effluents (S1, S2, S3) containing mainly reactive dyes. The operational conditions for pH varied between 2.5 and 4.0 while temperature ranged from 30°C to 50°C. The concentrations of FeSO₄ and H₂O₂ varied to a wide range (200–600 mg/l of FeSO₄, 300–1000 mg/l of H₂O₂) depending on the type of the dyes and their mixture and textile additives used in the process. FO is highly effective for colour removal (>99%) for reactive dyes and (87–94%) for textile finishing wastewater. It can be applied as a pretreatment and the remaining total dissolved solids (TDS) can be removed by an additional advanced process, e.g. membrane process.     

Synthesis and characterisation of new cationic polyelectrolytes by inverse emulsion polymerisation and their application in activated sludge dewatering

Water soluble hydrophobically associated polyelectrolytes were copolymerised with dimethyl- [2-(2-methyl-acryloyloxy)-ethyl]-alkyl ammonium bromide (alkyl: propyl, hexyl, dodecyl) (DEAC_n) and acrylamide (AM) in inverse emulsion. Cationic hydrophobically modified polyacrylamides having different molecule weight and cationic degree were obtained by varying the total monomer concentration and DEAC_n/AM mole ratio. Polyelectrolytes were characterised by ¹H-NMR and ¹³C-NMR. The dewatering indexes, such as CST, settling rate and water content in sludge cake were investigated and used to evaluate the dewaterability and settleability of activated sludge conditioned by these polyelectrolytes. Afterwards, some characteristics of sludge floc, such as: floc size, sludge viscosity and floc strength were measured. The function of hydrophobic association in sludge conditioning was elucidated by comparing dewatering performances with these polyelectrolytes     

Measurement of atmospheric particles and anionic species across central Taiwan

The ambient air concentrations and fluxes of various anionic species were sampled by MOUDI, TSP and dry deposition plates at a traffic sampling site in Taichung, central Taiwan. In the sampling period, from September to December 2000, the ambient air particle concentrations (PM₁, PM_2.5, PM₁₀ and TSP) were lower in the September than in the other three months (October to December). The reason is that the northwest wind brought more particles (diameter less than 10 μm) and the higher wind speed caused higher dry deposition fluxes and TSP concentrations in the last three months. The anion species percentages of TSP were 0.24%, 13.7%, 0.52%, 12.0%, 18.9'% and 54.6% for F^-, Cl^-, Br^-, NO₂^-, NO₃^- and SO₄^2-, respectively. The results revealed that SO₄^2-, NO₃^-, Cl^- and NO₂^- were the dominant species at the traffic sampling site. The ion-size distributions of Cl^-, NO₂^- and NO₃^- were unimodal, the main peak being between 3.2 and 5.6 μm. In contrast, the size distribution of SO₄^2- was bimodal, with the main peaks in the particle size ranges 0.32.0.56 μm and 3.2.5.6 μm. The ambient average particle dry deposition flux was 6.28 μg/m2/s, and the dry deposition fluxes were 0.01, 94.6, 0.05, 34.7, 72.2 and 376.4 ng/m2/s for F^-, Cl^-, Br^-, NO₂^-, NO₃^- and SO₄^2-, respectively. The dry deposition velocities were 3.10, 0.03, 3.67, 0.05, 1.54, 2.03 and 3.67 cm/s for F^-, Cl^-, Br^-, NO₂^-, NO₃^- and SO₄^2-, respectively.     

Nutrient mobilisation and losses related to the groundwater level in low peat soils

The changes in dissolved organic carbon (DOC), N-NO₃, N-NH₄ and P-PO₄ concentrations in response to fluctuations in the groundwater table were investigated in the peatlands of Biebrza National Park and some of its surrounding sites. The lowering of the groundwater table during summer time was accompanied by an increase in P-PO₄ and N-NH₄ concentrations, and in some cases they were exceptionally high compared with undisturbed water. Concentrations of both nutrients correlated with groundwater levels. Decreasing the groundwater level promoted higher concentrations of both nutrients. Nevertheless, elevated concentrations of P-PO₄ and N-NH₄ occurred in groundwater during the summer months when the outflow of water from peatland was slow. The N-NO₃ and DOC concentrations did not change markedly with the lowering of groundwater table or during different seasons.     

Metallic elements in particulates released during incense-burning at Tzu Yun Yen temple, Taichung, Taiwan

Concentrations of ambient suspended particulates were measured at Tzu Yun Yen temple (120°, 34′ 10”E; 24°, 16′, 12”N), using a Universal sampler and dry deposition plates. The temple is a characteristic incense-burning and semi-open sampling site. PM_2.5 concentrations for Period 1 (average 901μg/m3) were higher than those for Period 2 (average 701μg/m3). Results for average PM_2.5-10concentrations showed equal distributions in Period 1 and Period 2. Average ratios of PM_2.5/ PM₁₀ were higher in Period 1 (74%) than Period 2 (71%). In addition, the suspended particulate (PM₁₀) elements concentrations during Zhong Yuan Jie, and the first and 15th days of nong li for each month (Chinese lunar calendar) were all higher than during non-Zhong Yuan Jie and non-first and non-15th days. Furthermore, the dry deposition velocities of manganese in fine particulates (PM_2.5) and suspended particulates (PM₁₀) were 1.43 and 0.751cm/s, respectively, and the dry deposition velocities of cadmium in fine particulates (PM_2.5) and suspended particulates (PM₁₀) were 1.86 and 0.991cm/s, respectively.     

A statistical model for predicting carbon monoxide levels

This paper presents a statistical model that is able to predict carbon monoxide (CO) concentrations as a function of meteorological conditions and various air quality parameters. The experimental work was conducted in an urban atmosphere, where the emissions from cars are prevalent. A mobile air pollution monitoring laboratory was used to collect data, which were divided into two groups: a development group and a testing group. Only the development dataset was used for developing the model. The model was determined by using a stepwise multiple regression modelling procedure. Thirteen independent variables were selected as inputs: non-methane hydrocarbon (NMHC), methane (CH₄), suspended dust, carbon dioxide (CO₂), nitrogen oxide (NO), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), wind speed, wind direction, temperature, relative humidity and solar energy. It was found that NO has the most effect on the predicted CO concentration. The contribution of NO to the CO concentration variations was 91.3%. Adding in the terms for NO₂), NMHC and CH₄ improved the model by only a further 2.3%. The derived model was shown to be statistically significant, and model predictions and experimental observations were shown to be consistent.     

Influence of meteorological factors on air pollution concentration for a coastal region in India

A long-term study of measurement of concentration of NO_x, SO₂ and TSP pollutants have been done in a port and harbour region in India. Monthly measurements of gaseous and particulate pollutants were made at six monitoring stations from January 1997 to December 2000. Meteorological data was also simultaneously collected. In this study, the relationship between monitored ambient air quality data and meteorological factors, such as wind speed, temperature, is statistically analysed, using the SPSS package. The monthly mean concentrations of NO_x, SO₂ and TSP were in the range of 19.5–59.0 μg/m3, 8.6–51.3 μg/m3 and 88.2–199.3 μg/m3, respectively. The results show that TSP is strongly correlated with NO_x and SO₂ with a correlation coefficient of 0.83 and 0.82, respectively. The correlation coefficients for TSP, NO_x, and SO₂ with wind are –0.78, –0.78, and –0.88, respectively.     

Wastewater treatment using bioreactor with dual functional ceramic membrane

A novel bioreactor including a group of dual functional ceramic membranes was developed and used for wastewater treatment. The ceramic membranes could be used for both aeration and filtration alternately, so fouling to ceramic membrane would be palliated effectively as its dual functions. For 100 days operation, COD removal ratio was 88∼97% for influent COD of 154∼1389 mg/L, and NH₄⁺-N removal ratio was 98% for influent NH₄⁺-N of 7.52∼51.35 mg/L. Some washing methods aiming at foul were discussed, experimental results indicated that surface foul is main factor to ceramic membrane and NaClO is better washing agent for the flux recover.     

Monitoring of phytoplankton biomass and nutrients in a polluted stream

The spatial and temporal variations in the concentrations of nutrients (NH₄⁺, NO₂⁻, PO₄³⁻, SiO₄⁻) and chlorophyll a were monitored simultaneously in a slow-flowing watercourse (Saricay Stream, Turkey), which runs in a rural–urban gradient. Chlorophyll a concentrations ranged between 0.044 μg l^-1 and 206.15 μg l^-1 and, in general, the higher concentrations of chlorophyll a and ammonium were measured downstream of the raw sewage outfalls. Nitrate was by far the most abundant form of inorganic nitrogen, and its concentration ranged between 411.71 μM and 87.25 μM. Silicates and phosphates were always potentially limiting to biomass relative to nitrogen. Agricultural run-off and point discharges from urban sources greatly affected the chemical composition of the water in the Saricay Stream and drove the system towards eutrophication.     

Effect of leachate recirculation on refuse decomposition rates at landfill site: a case study

In this study, a comparison of methane (CH₄) generation rates for two test cells, one operated with (enhanced) and another without leachate recirculation at Odayeri Sanitary Landfill were compared using their bio-chemical methane potentials (BMP). Initial methane potential is approximately 34.5 m3 CH₄/wet ton of solid waste. The remaining methane potential for the control (C1) and the enhanced (C2) cells are 32.6 m3 CH₄/wet ton and 31.1 m3 CH₄/wet ton of refuse after eight months of operation, respectively. The produced CH₄ quantities for C1 and C2 after eight months of operation are 1.9 m3 CH₄/wet ton and 3.4 m3 CH₄/wet ton, respectively. On the other hand, 5.5% and 9.9% of the total potential are generated in eight months. However, the CH₄ generation rates for the first year are determined as 2.85 and 5.10 m3/ton/year for C1 and C2 test cells, respectively. Due to the appropriate conditions such as moisture content, solid waste decomposition rate is enhanced at a rate of 79% at C2 test cell relative to C1 test cell. Hence, C2 test cell shows more decomposition relative to the C1 test cell.     

Analysis and interpretation of the monitoring data for C2–C11 hydrocarbons in the atmosphere of a rural Portuguese site

This paper focuses the application of a measurement technique for determining atmospheric C₂–C₆ hydrocarbons after canister sampling and analysis by gas chromatography/flame ionisation detection (GC/FID), as well of an adsorption-sampling technique for C₆–C₁₁ compounds and GC/FID analysis after thermal desorption and cryogenic concentration. Tens of samples collected at Giesta, a rural area located 20 km to the SE of the coastal Portuguese city of Aveiro, were analysed. The characterisation of C₂ C₁₁ hydrocarbons is presented, considering seasonal variations, diurnal cycles, the influence of air masses and different photochemical conditions. Ratios between hydrocarbons and principal components analysis were applied to differentiate between biogenic and anthropogenic sources.