Environmental Technology

Falcon, M.; Fajerwerg, K.; Foussard, J. N.; Puech-Costes, E.; Maurette, M. T.; Debellefontaine, H.

doi: 10.1080/09593330.1995.9618251pmid: N/A

The wet peroxide oxidation process (WPO®) which was developed at the laboratory uses the Fenton's reagent at high temperature. But the reaction efficiency is limited by the accumulation of volatile fatty acids such as oxalic, malonic, succinic and acetic acids (hereafter OMSA). In order to improve the efficiency of the original process, different transition metal ions are tested as catalyst. The experimental results indicate that the system using homogeneous Fe, Cu, and Mn is a promising one. The oxidation of carboxylic acids is quite completed under mild working conditions (T < 100°C, pH = 3, p = 1 atm, reaction time = 1 h, stoichiometric quantity of H2O2 = 1.5). Optimal design methodology is applied to the catalytic mixture Fe:Cu:Mn in order to determine the optimal proportions of each metal. This results in the determination of an important synergistic effect between the metals and an optimal zone. Cu(II), Mn(II) or Fe(II) alone have a slight catalytic effect while the association is very effective on the oxidation of the mixture of carboxylic acids (OMSA). This apparent synergetic effect existing among them can be explained by the main specific roles of Cu(II) and Mn(II) ions. They respectively enhance significantly the oxidation rate of acetic and oxalic acids.

Cousins, Ian T.; Watts, Chris D.; Freestone, Richard

doi: 10.1080/09593331608616293pmid: N/A

The application of models to predict the behaviour of chemicals in the aquatic environment will assume increasing importance as the sophistication of river pollution management increases. A field validation of a model which enables such predictions, the US EPA EXAMS II model, is reported. The study was carried out on a stretch of a UK lowland river, the River Calder in West Yorkshire, and utilised a sewage treatment works (STW) effluent discharge as a point source of the two chemicals, aniline and lindane, modelled. Concentrations of aniline and lindane were measured in samples of water, suspended particulates and sediments taken from the river and STW effluent and the measured results compared with those predicted by the EXAMS model. Good agreements were generally obtained between the model predictions and the measured values for the water and bed sediment, but the levels measured in the suspended particulates were significantly higher than those predicted. The most likely explanation for this discrepancy was that the equilibrium partitioning approach employed by EXAMS was inappropriate for the suspended particulate associated chemicals. However, since the majority (>>95%) of both aniline and lindane in the water column was in the dissolved phase, this was not a significant drawback to the use of EXAMS for the prediction of fate and behaviour.

Wong, J.W. C.; Li, S.W. Y.; Wong, M. H.

doi: 10.1080/09593331608616294pmid: N/A

Coal fly ash has a strong alkaline buffering capacity which may render heavy metals in sewage sludge unavailable and the aim of this project is to study the potential of coal fly ash as a co-composting material for sewage sludge by evaluating its effect on the microbial decomposition of sewage sludge. Lagoon ash and fly ash at 0, 2.5, 5, 10, 20, and 50% w/w were mixed with dewatered sewage sludge and incubated at 25°C for 3 months. Carbon dioxide evolution for all treatments followed the same trend except 50% w/w amendment for both ash residues. When compared with the control (sludge only), higher levels of ash amendments had a lower CO2 evolution which may be due to the high entrained salt content and pH in both ash residues. The present results indicate that fly ash has a more pronounced inhibition on sewage sludge decomposition while 2.5% w/w and 5% w/w lagoon ash amendments demonstrate no significant inhibition. Therefore, lagoon ash would be a more suitable co-composting candidate for sewage sludge and the suitable amendment rate should be < 10%.

Pinochet, H.; De Gregori, I.; Delgado, D.; Gras, N.; Muñoz, L.; Bruhn, C.; Navarrete, G.

doi: 10.1080/09593331608616295pmid: N/A

Samples of bivalves mussels Tagelus dombeii and Semelle solida (Navajuelas and Almejas Chilenas respectively) were collected at Corral Bay-Chile. Simultaneously, samples of water and sediments from the same site were collected. Seven sampling were carried out between July 1990 and July 1993. The total metals concentration in whole tissue of molluscs, sediment and the dissolved metals in water were determined. For Tagelus dombeii, the Cd concentrations ranged between 2.9 to 6.4 µg g−1 and for Cu between 2.2 to 3.6 µg g−1. For Almejas Cd concentrations ranged between 0.6 – 1.2 µg g−1 d.w. while Cu levels ranged from 4.8 to 11 µg g−1. The Cd/Cu ratio Tagelus dombeii was around 5, while for Semelle solida it was always lower than 1. The results show that Tagelus dombeii is a more effective bioaccumulator of Cd than Semelle solida. A comparison between the metal levels in sediment and water samples taken in Pacific coastal areas, from four rivers surrounding the Corral Bay sampling site shows that the partition coefficient at Corral bay (ratio of Cd concentrations in sediments and water) was lower than those found in the Pacific coastal areas and increased in rivers, indicating an influence of low salinity in the Cd levels found in Tagelus dombeii; this trend is not observed for Cu.

Humphreys, P. N.; Banks, C. J.

doi: 10.1080/09593331608616296pmid: N/A

Four identical laboratory scale sequencing batch activated sludge plants were used to carry out comparative performance evaluations of nitrification and denitrification, and to obtain an accurate nitrogen balance for the system. In the first instance the plants were run under identical operational conditions to ensure that results were statistically valid. Ten performance parameters were compared and no significant differences at 95% confidence limits were found. A nitrogen mass balance, considering dissolved nitrogen species, waste biomass and denitrification losses during settlement, accounted for 87.4% of known inputs. On the introduction of denitrification periods, nitrate and total nitrogen removal increased with increasing anoxic period up to a maximum of 74% and 71% respectively. The inclusion of anoxic periods reduced total organic carbon (TOC) removal by as much as 19%. These losses are a consequence of maximising nitrate removal when the cycle duration is fixed. This is due to differences in efficiency between aerobic and denitrifying activity. Good linear relationships were shown between % nitrogen removal (r=0.93), effluent nitrate concentration (r=−0.94), T.O.C. removed (r=−0.99) and the ratio of anoxic to aerobic retention times; this was providing the anoxic period was taken to be the period of nitrate removal. These relationships may provide a guide for designing sequencing batch nitrification /denitrification systems. Some enhancement of nitrification was also evident at short denitrification phases.

Alhaddad, Amir A.; Salman, Mohammed; Alyahya, Fatma

doi: 10.1080/09593331608616297pmid: N/A

One of the major concerns after the Iraqi invasion to Kuwait is the possibility of air pollution due to massive oil spillage on land and water. Experimental studies were performed to determine factors affecting the rate of evaporation of two different crude oils of API 28 & 38 on a laboratory scale. Factors like API, environmental temperature, depth of the crude oil, exposed surface area and wind speed on the rate of evaporation of these crude is reported. Predetermined experiments were carried out to study the above factors. Quantitative estimation of each component in the crude, ranging from C5 to C16 was done. Based on these estimations, the mole fraction of each component remaining with time was obtained. An analysis of different factors, based on the experimental data indicate that surface area and API of the crude oil has no influence on the rate of evaporation.

Surmacz-Gorska, J.; Gernaey, K.; Demuynck, C.; Vanrolleghem, P.; Verstraete, W.

doi: 10.1080/09593331608616298pmid: N/A

A method, based on oxygen uptake rate measurements combined with the application of selective nitrification inhibitors, is presented which allows monitoring nitrifying activities of activated sludge samples. Nitrification activity measurements, only requiring a dissolved oxygen probe, can yield information on NH4 + and NO2 − concentrations in mixed liquor samples. In this way, oxygen uptake rate measurements are a helpful tool to monitor the completion of the oxidation of NH4 + and NO2 − in activated sludge processes. Some examples, demonstrating the value of alternate oxic and anoxic periods for nitrogen removal during sequencing batch reactor processes, also indicate the value of activity measurements for nitrification control purposes. The presented method offers a possibility to optimise the length of oxic-anoxic sequences in sequencing batch reactors which results in a better effluent quality of the treatment plant.

Gavin, M.; Crump, D. R.; Brown, V. M.

doi: 10.1080/09593331608616299pmid: N/A

Active and passive sampling methods are available for the determination of maximum formaldehyde concentrations and average formaldehyde concentrations respectively. The present work compares the performance of an active cartridge type sampler with an impinger method and a diffusive monitor which have previously been used at the Building Research Establishment. Good agreement between the three methods was found in a comparison at two formaldehyde concentration levels. The sampling strategy required to obtain a representative reading of the formaldehyde concentration in an indoor atmosphere was investigated using a commercially available diffusive sampler. An investigation of spatial variation in five rooms suggests that sampling in one location should give a representative reading of the formaldehyde concentration in a room, providing the sampler is not placed near a major source of formaldehyde. An initial investigation of temporal variation in six rooms found that one three day sampling period was sufficient to obtain a representative reading of the mean monthly formaldehyde concentration. Between month variation was found to be higher than within month variation although no strong seasonal effects were observed. The results suggest that more than one three day sampling period should be used to estimate the annual mean formaldehyde concentration and two measurements (summer and winter) may be a reasonable approach. Further work in a larger number of homes is in hand to verify the effectiveness of this sampling strategy.

Xu, J. G.; Feng, Y.; Johnson, R. L.; McNabb, D. H.

doi: 10.1080/09593331608616300pmid: N/A

Soil pore structure is one of the most important characteristics which influence the biodegradation of hydrocarbons in soil. The objective of this study was to quantify and compare the inter- and intra-aggregate pore structures of oil-contaminated, aggregated oil-contaminated and uncontaminated soils and their effects on microbial biomass and activities. The inter-aggregate and intra-aggregate porosity of the untreated oil-contaminated soil was less than that of the uncontaminated soil indicating the oil-contaminated soil was more compacted, which reduced the microbial activity. The microbial biomass and activity in the aggregated oil-contaminated soil was greater than in the untreated oil-contaminated soil indicating the aggregation process improved the physical environment for microorganisms and enhanced the biodegradation of hydrocarbons in soil.

Elektorowicz, Maria; Konyukhov, Boris

doi: 10.1080/09593331608616301pmid: N/A

The theory of seismic surface Stoneley/Scholte wave modulation method was developed in order to characterize the dynamic properties of the uppermost layer of soft contaminated sediments in rivers and the sea. The theory is based on acoustoelasticity models of high-saturated porous media. The results for surface Stoneley/Scholte wave-modulation index were shown to depend on the physical, and chemical properties of suspension-like sediment, contaminant concentration, and interaction forces between solid particles and contaminated liquid.