Environmental Technology

Shi, J. P.; Harrison, R. M.; Evans, D. E.; Alam, A.; Barnes, C.; Carter, G.

doi: 10.1080/09593332508618430pmid: 11918399

Earlier research has demonstrated that the conditions of dilution of engine exhaust gases profoundly influence the size distribution and total number of particles emitted. Since real world dilution conditions are variable and therefore difficult to simulate, this research has sought to develop and validate a method for measuring particle number emissions from vehicles driving past on a road. This has been achieved successfully using carbon dioxide as a tracer of exhaust gas dilution. By subsequent adjustment of data to a constant dilution factor, it is possible to compare emissions from different vehicles using different technologies and fuels based upon real world emission data. Whilst further optimisation of the technique, especially in terms of matching the instrument response times is desirable, the measurements offer useful insights into emissions from gasoline and diesel vehicles, and the substantial proportion of particles emitted in the 3-7 nanometre size range.

Wong, J.W. C.; Wan, C. K.; Fang, M.

doi: 10.1080/09593332508618438pmid: 11924580

Pig manure at three different ratios of 12.5%, 25% and 50% (w/w dry weight basis) was amended with a soil spiked with 100 mg kg−1 each of three polycyclic aromatic hydrocarbons (phenanthrene, anthracene, and pyrene) to investigate its effect on the biodegradation of these PAHs in a bench-scale composting system. An increase in pig manure amendment was effective in enhancing the amounts of soluble organic carbon, ammoniacal nitrogen, and soluble phosphorous in the composting mass. It could also increase the populations of total thermophilic and mesophilic bacteria as well as PAH-degrading bacteria, but this pattern was restricted only to the early stage of the composting process. High amounts of pig manure in the composting mass reduced the seed germination or root growth of cress seeds, but the composting process was effective in reducing the phytotoxic effects of the compost. Amendment of pig manure was beneficial to PAH removal during composting treatment and maximum removal rate at the end of composting accounted for 90% of the initial concentrations of PAHs. A pig manure application rate of 25% showed the most efficient removal of 3-ringed PAHs (phenanthrene and anthracene), while no significant difference in pyrene removal for those receiving 25 or 50% pig manure amendment. Taking into consideration the effects of pig manure on seed germination and available nutrients in the composting mass, this study suggested that a pig manure amendment of 25%, i.e., 3:1 ratio of contaminated soil: pig manure, is recommended to co-compost with PAH-contaminated soil.

Droppo, I. G.; Irvine, K. N.; Jaskot, C.

doi: 10.1080/09593332508618433pmid: 11918400

The urban continuum, as it applies to sediments and associated contaminants, represents the area over/through which sediments are conveyed from a depositional or eroded surface to a treatment system and/or receiving water body. This study has focused on the changing physical characteristics of the sediment, with an emphasis on flocculation/aggregation, as it progresses through the urban continuum. The sediments of the urban continuum are found to change from an unflocculated state on the street, to a flocculated state in the surface runoff to a very large floc form in the sewer system. The high organic content in the sewers contributes to the large floc size. The structure of the flocs and the flow regime of the receiving water will dictate the fate of the sediment following a combined sewer overflow. Probability distributions fitted to the distributions of each sediment type (compartment) confirmed significant differences in the sediment population sizes. Bulk and individual particle settling velocity experiments also revealed substantial differences between compartments. Sewer flocs were found to be of low density, with high porosity, water and organic content and with settling velocities which increase with floc size.

Shang, N.-C.; Yu, Y.-H.

doi: 10.1080/09593332508618432pmid: 11918401

This research investigates the aqueous toxicity occurring during color formation due to ozonation in a semi-batch reactor. The tested mono-substituted aromatic compounds were aniline, phenol (-NH2, -OH, electron-donating group), nitrobenzene and benzoic acid (-NO2, -COOH, electron-withdrawing group). The results revealed that the aqueous toxicity of the Microtox assay from oxidized samples during the early stage of ozonation increased when the color formation was observed, except in the case of nitrobenzene under high pH conditions. Toxicity typically reached a peak at or near the moment of maximum color intensity. Ozonation of these aromatic compounds showed a large increase in toxicity, and the 50% effective concentration (EC50) expressed as chemical oxygen demand (COD) (mg l−1) decreased to 1.4 (aniline), 1.2 (benzoic acid), 0.8 (phenol) and 0.6 (nitrobenzene) orders-of-magnitude. Moreover, the aromatic compounds with an electron-donating group promoted color formation more than did the electron-withdrawing group substituted compounds.

Park, J.-H.; Shin, H.-S.; Lee, I.-S.; Bae, J.-H.

doi: 10.1080/09593332508618431pmid: 11924581

The effects of both concentration and loading rates of nitrate on denitrification efficiency and N2O production during the autotrophic denitrification with elemental sulfur were evaluated. Experiments were conducted with three continuously fed sulfur packed bed reactors (SPBRs) with different influent nitrate concentrations. The loading rate at which nitrate removal efficiency was greater than 95% decreased from 2.46 to 1.64 kg NO3 −-N m−3 day−1 as the influent NO3 −-N concentration increased from 175 to 700 mg l−1. The nitrate removal rate per unit volume of sulfur layer can be expressed as α (ALR)n, where ALR is the applied loading rate. The range of α and n values were 0.72-0.83 and 0.91-0.94, respectively. The maximum nitrate removal rate was estimated as 3.9 to 4.5 kg NO3 −-N m−3 day−1 depending on the influent NO3 −-N concentration. The loading rate for complete denitrification without N2O production was 1.37 kg NO3 −-N m−3 day−1 at the influent NO3 −-N concentration of 175 mg l−1. N2O production became significant when the influent nitrate concentration increased while the loading rate remained the same. The batch test indicated that the amount of N2O production per unit mass of nitrogen was greater with nitrite than with nitrate showing that N2O production was directly related to the concentration of nitrite and nitrate.

Seka, M. A.; Van De Wiele, T.; Verstraete, W.

doi: 10.1080/09593332508618434pmid: 11918402

A multi-component additive formulated for a more efficient control of activated sludge filamentous bulking was evaluated at a full-scale treatment plant experiencing severe filamentous bulking. It was found that, besides offering an immediate improvement of sludge settling, the multi-component additive was able to eliminate the filamentous bacteria causing the bulking. Hence, contrary to ordinary additives, this novel additive yielded immediate as well as long-term improvements in sludge sedimentation upon a few additions. Preliminary lab-scale toxicity tests showed that the treatment of the sludge by the additive should not impart any toxicity to the resulting effluent.

Battistoni, P.; Boccadoro, R.; Pavan, P.; Bolzonella, D.

doi: 10.1080/09593332508618435pmid: 11918403

The paper presents the results of a one-year study of the performance of a full scale plant for the treatment of industrial liquid wastes adopting the alternate cycle process. The carbon and nitrogen removal performances were discussed according to the experimental measurements of maximum nitrification and denitrification rates. It was demonstrated that the nitrification process was the limiting step: it worked with a rate in the range 0.002 - 0.02 KgNH4-N kg−1VSS d−1 at 20°C. This was because of inhibition phenomena due to the presence of both complex organic compounds and heavy metals which were not removed by the chemical-physical pre-treatment step. The denitrification process was characterized by a maximum rate ranging from 0.015 to 0.056 Kg NO3-N kg−1VSS d−1 at 20°C, according to the available amount of readily biodegradable COD in the treated wastes. The reliability of the aerobic-anoxic process was determined on the basis of the percentage of successful cycles compared with the performed ones. It was shown that the actual cycles ranged from 50 to 100% of the expected ones, while effective cycles were up to 84% in the first step and up to 60% in the second one. These were related to the carbon to nitrogen ratio. Even if at times the nitrogen and carbon removal yields were not satisfactory, the two step aerobic-anoxic process operated in the alternate cycle mode seems a successful solution for the treatment of liquid industrial wastes.

Singh, I. B.; Singh, D. R.

doi: 10.1080/09593332508618436pmid: 11918404

In this study, iron-bearing industrial solid wastes iron filings, ETP sludge of steel and red mud of aluminium industries; were used for Cr(VI) removal at pH 3. A complete removal of Cr(VI) was found for initial 10 mg l−1 of 100 ml solutions in the presence of 2.5 g iron filings, 8 g ETP sludge and 10 g red mud for up to one hour of shaking at room temperature. After Cr(VI) removal, inclusion of chromium on the reacted iron filing surface was demonstrated by EDAX analysis. Leachability of chromium and iron from the reacted wastes was determined by using Toxicity Characteristics Leaching Procedure (TCLP). This test showed a very low level of leachability of chromium as Cr(III) and iron from the reacted wastes. To minimise their leachability further, Cr(VI)-reacted solid wastes were stabilised with Portland cement in their 3:1 ratio. Leachability tests of stabilised wastes by TCLP indicated a considerable decrease in leachability of chromium and iron compared with the that of reacted wastes alone. To explore the possibility of utilisation in building materials, bricks of cement-mixed Cr(VI)-reacted wastes were made and their comprehensive strength, durability and leachability under immersion conditions were measured.

Yedla, S.; Dikshit, A. K.

doi: 10.1080/09593332508618437pmid: 11918405

In this paper an attempt was made to develop and evaluate the performance of a fixed bed adsorber (FBR) column to remove endosulfan, an organochlorine pesticide from the water environment using wood charcoal as an adsorbent. The FBR column design parameters were evaluated using the column breakthrough data at different bed depths. The Bohert and Adams model was used with bed depth-service time (BDST) approach for the design of the adsorber. Similarity in service time values estimated from BDST approach and experimental curves revealed that BDST approach could be adapted for the design of this system. Desorption of the exhausted column with 10% methanol solution took 1hr with maximum desorption occurring at 0.5 hrs with a maximum endosulfan concentration of 47 mg l−1. A laboratory column study for 3 successive cycles of operation (adsorption-desorption) revealed that the column could treat 47.27 bed volumes of endosulfan-contaminated water up to breakthrough and 158.45 bed volumes up to exhaustion. It showed a promising performance with more than 89% of its original efficiency even after the 3rd cycle of operation. It clearly demonstrates adaptability of the present study in developing adsorber columns for rural areas.

Tseng, H.-H.; Wey, M.-Y.; Lu, C.-Y.

doi: 10.1080/09593332508618439pmid: 11924579

The primary objective of the present work is to use additives to extend the sulfation reaction of the calcium hydroxide (Ca(OH)2) used to control SO2 emission from incineration processes. There are two reasons for adding surfactants (surface-active agent): (1) to provide an appropriate dispersion of the Ca(OH)2, thus preventing particle agglomeration due to humidity; (2) to alter the sulfation reaction environment by adsorbing heterogeneous materials on the surface of the Ca(OH)2 to extend the adsorption equilibrium. A dry scrubber integrated with a fabric filter was employed to study the effect of surfactants on the removal efficiency of acid gas in the flue gas with Ca(OH)2 as the sorbent. The operating parameters evaluated include: (1) the different surfactants (calcium lignosulfonate, sodium lignosulfonate, alkyl naphthalene sodium sulfonate and β-naphthalene sodium sulfonate condensates) and (2) the composition of acid gas (i.e. sulfur dioxide (SO2), nitrogen oxide (NO) and hydrogen chloride (HCl)). The results show that modified Ca(OH)2 with surfactants could effectively decrease the emission of acid gas during incineration. Different additives had individual absorption efficiencies on different acid gases. On the whole, sodium lignosulfonate and β-naphthalene sodium sulfonate condensates had better sorption capacity for SO2 and NO, but not for HCl. In addition, when SO2 coexisted with NO and HCl, the concentration of NO and HC1 will result in decrease or increase of the removal efficiency of SO2.