Environmental Technology

Prasher, S.O.; Beaugeard, M.; Hawari, J.; Bera, P.; Patel, R.M.; Kim, S.H.

doi: 10.1080/09593332508618378pmid: 15551823

The biosorption of heavy metals from aqueous solutions was investigated, using a cheap and abundant dry biomass of red algae P. palmata. The Freundlich, Langmuir and Brunauer Emmer and Teller (BET) models were used to describe the uptake of lead (Pb2+), copper (Cu2+), nickel (Ni2+), cadmium (Cd2+) and zinc (Zn2+) on P. palmata. The good fits of the Langmuir and BET models to the experimental data reflected that the sorption on P. palmata was a multi-layer sorption, in which a Langmuir equation could be applied to each layer. The highest maximum sorption capacity qmax, derived from the Langmuir model was 15.17 mg g-1 for lead and 6.65 mg g-1 for copper (dry weight metal/dry weight biosorbent) at a pH of 5.5-6. The affinity of metals for P. palmata was found to decrease in the order: Pb2+ > Cd2+ > Cu2+ > Ni2+. The factors influencing copper and lead uptake were found to be contact time, pH, initial concentration and temperature. Biosorption of copper and lead was a rapid process, with 70% and 100% of the respective uptakes occurring within the first 10 minutes.

Gulsen, H.; Turan, M.

doi: 10.1080/09593332508618388pmid: 15551824

Anaerobic treatment of the young landfill leachate in a pilot-scale fluidized bed reactor was performed to observe the effects of startup on COD removal, biogas production and biomass attachment. During the experiments, the organic loading rate (OLR) was increased gradually from 2.5 to 27 g COD l -1 day -1 with varying the feed rate and the hydraulic retention time in the range of 5.5-13 l day -1 and 1-2.35 days, respectively. The anaerobic fluidized bed reactor (AFBR) showed an excellent performance and attained steady state conditions with COD removal of 90% after 80 days. Biogas production in the reactor continuously increased and its average yield (Ygas) was defined as 0.53 l biogas g-1 CODrem -1 with a correlation of 99%. Greater microbial attachment was found at the increased loading rates and the attached biomass concentration (Xattach) consisted of about 90% of the total biomass concentration. In addition, the substrate utilization rate indicated a linear increase as a function of time during the process.

Mustafa, S.; Naeem, A.; Rehana, N.; Hamid, A.; Dilara, B.

doi: 10.1080/09593332508618383pmid: 15551825

The sorption behaviour of phosphate on strong basic anion exchanger, Amberlite IRA-400 (SO4 2- form) is studied as a function of pH (3-11) at two different initial concentration ranges (0.161 - 0.807 mmol l-1, 3.874 - 6.134 mmol l-1) at 25 °C. The stiochiometry of the exchange reactions is observed to be dependent upon concentration and pH of the solutions. It is suggested that the sorption of phosphate takes place initially as PO4 3- followed by HPO4 2-/H2PO4 -. The data obtained is explained with the help of a modified Langmuir and mass law action equations.

Green, M.; Gidron, E.; Beliavski, M.; Lahav, O.; Tarre, S.

doi: 10.1080/09593332508618389pmid: 15551826

The aim of this research was to investigate the feasibility of treating liquid dairy wastes by a vertical bed equipped with an innovative passive aeration system. The vertical bed (32 liter) was operated by recirculating consecutive batches of liquid waste in the column. Batches of liquid waste were applied at two different rates: 1) each batch was recirculated for 72 hours, and 2) each batch was recirculated for 24 hours. Settled liquid dairy wastes (5000 mg l-1 COD, 2000 mg l-1 BOD and 2500 mg l-1 TSS) were used in the experiments. When the reactor operated with each batch recirculating for 72 hours, the BOD and COD reduction were 66% and 40%, respectively. The vertical bed operated successfully without the need for an additional rest period. The main removal was observed to take place during the first 20 hours. No biomass or solids accumulation was observed indicating that the remaining 52 hours of recirculation were actually used for bed regeneration, i.e.integrated rest period. When the reactor operated with each batch recirculating for 24 hours, the system clogged after 21 days. An additional 24 day rest period was needed in order to free 94% of the initial void space. In this mode, the BOD and COD reduction were 67% and 47%, respectively. The overall COD removal in a complete operational cycle (feeding period followed by a rest period) was 467 g COD m-3 d-1 (996 g COD m- 2 d-1). This value is 1.4 higher than the COD removal obtained in the 72 hour per batch mode and shows the advantage of conventional vertical bed operation of intensive feeding followed by rest period rather than a rest period integrated into the feeding cycle.

Udrea, I.; Avramescu, S.

doi: 10.1080/09593332508618379pmid: 15551827

Oxidation of inorganic contaminants, such as thiocyanate and cyanide ions, by ozone in water has improved significantly in the presence of solid catalysts based on nickel and cobalt oxides supported on alumina. It can be considered that the hydroxyl radical produced by catalytic decomposition of ozone over the catalyst's surface was responsible for the oxidation of the adsorbed ions. Ozonation efficiency was increased by 20% in the presence of catalytic systems in particular for those systems containing both nickel and cobalt oxide.

Ahmad, S.R.

doi: 10.1080/09593332508618380pmid: 15551828

A new technology for automatic sorting of plastics, based upon optical identification of fluorescence signatures of dyes, incorporated in such materials in trace concentrations prior to product manufacturing, is described. Three commercial tracers were selected primarily on the basis of their good absorbency in the 310-370 nm spectral band and their identifiable narrow-band fluorescence signatures in the visible band of the spectrum when present in binary combinations. This absorption band was selected because of the availability of strong emission lines in this band from a commercial Hg-arc lamp and high fluorescence quantum yields of the tracers at this excitation wavelength band. The plastics chosen for tracing and identification are HDPE, LDPE, PP, EVA, PVC and PET and the tracers were compatible and chemically non-reactive with the host matrices and did not affect the transparency of the plastics. The design of a monochromatic and collimated excitation source, the sensor system are described and their performances in identifying and sorting plastics doped with tracers at a few parts per million concentration levels are evaluated. In an industrial sorting system, the sensor was able to sort 300 mm long plastic bottles at a conveyor belt speed of 3.5 m. sec-1 with a sorting purity of ~95%. The limitation was imposed due to mechanical singulation irregularities at high speed and the limited processing speed of the computer used.

Alcántara, S.; Velasco, A.; Revah, S.

doi: 10.1080/09593330.2004.9619409pmid: 15551829

The elemental sulfur formation by the partial oxidation of thiosulfate by both a sulfoxidizing consortium and by Thiobacillus thioparus ATCC 23645 was studied under aerobic conditions in chemostat. Steady state was attained with essentially total conversion to sulfate when the dissolved oxygen concentration was 5 mgO2 l-1 and below a dilution rate (D) of 3.0 d-1 for the consortium and 0.9 d-1 for T thioparus. The consortium formed elemental sulfur in steady state under oxygen limitation. Fifty percent of the theoretical elemental sulfur yield was obtained with a dissolved oxygen concentration of 0.2 mgO2 l-1. Growth of T thioparus was negatively affected with a concentration below 1.9 mgO2 l-1. Consortium yield from batch cultures was 2.1 g-1 proteinmol-1 thiosulfate, which was comparable with the values obtained in the chemostat at dilution rates of 0.4 d-1 and 1.2 d-1. The consortium showed a maximum degradation rate of 0.105 gthiosulfate g-1 proteinmin-1 and a saturation rate for S2O3 2-of 1.9 mM.

Cheng, K.Y.; Zhao, Z.Y.; Wong, J.W.C.

doi: 10.1080/09593332508618382pmid: 15551830

Surface-active agents (surfactants) can enhance bioremediation of soils contaminated with PAHs by reducing sorption of PAHs or increasing desorption rates. The effectiveness of nonionic surfactant (Tween 80) and biosurfactants to enhance the solubilization and desorption of phenanthrene (Phe) and pyrene (Pyr) in soil-aqueous systems under thermophilic conditions was investigated using batch studies. Tween 80 and biosurfactants produced from Pseudomonas aeruginosa strain, ATCC 9027 and a strain isolated in our laboratory, P-CG3 were tested in this study. The results showed that all the surfactants could effectively enhance the solubility of both Phe and Pyr under thermophilic condition (55°C), which was linearly proportional to the concentrations of surfactants at concentrations above their respective critical micelle concentration (CMC). When the surfactants' concentrations in aqueous phase were above their respective CMCs, substantial amounts of PAHs were desorbed from soil into the aqueous phase. Among the three surfactants used, the biosurfactant produced from our own isolate, P-CG3 was more effective in enhancing the solubilization and desorption of PAHs, implying that it might have the potential to be further applied in the bioremediation of PAH contaminated soils.

Li, J.G.; Lalman, J.A.; Biswas, N.

doi: 10.1080/09593332508618384pmid: 15551831

Batch tests were employed to investigate the effects of aerobic and anoxic conditions on the biodegradation of Red B dye by Bacillus OY1-2. Results from batch experiments demonstrated anoxic conditions were beneficial for rapid biodegradation of Red B dye in comparison to aerobic conditions. Biodegradation is a major mechanism in the decolorization of Red B dye in comparison with biosorption, which accounted for only 8% of the total decolorization efficiency. Reactors packed with granular activated carbon (GAC) and inoculated with Bacillus OY1-2 were investigated to treat a synthetic wastewater under anoxic conditions. In the absence of cosubstrates, Red B dye was degraded; however, a significant improvement in degradation resulted with the addition of cosubstrates.

Zhu, K.; Gamal El-Din, M.; Moawad, A.K.; Bromley, D.

doi: 10.1080/09593332508618385pmid: 15551832

A physical/chemical treatment train, that included 24-hour preliminary settling followed by coagulation/flocculation and sedimentation, was tested at a laboratory bench scale to treat liquid swine manure for the removal of total suspended solids (TSS) and total phosphorus (TP). Preliminary (i. e., natural) settling time had an effect on TSS removal within only the first 24 hours. TSS removal efficiency reached 75% (TSS concentration was reduced from 5,800 to 1,450 mg l-1) after 24 hours of preliminary settling. Also, as a result of the 24-hour preliminary settling, TP concentration was reduced from 533 to 318 mg l -1, thus leading to a TP removal efficiency of 40%. When compared to ferric chloride, alum was more effective in reducing both TSS and TP. At a 95% confidence interval, alum dose, coagulation Gt (coagulation velocity gradient * rapidmixing time), and flocculation Gt (flocculation velocity gradient * slow-mixing time) were not significant for TSS removal while alum dose was the only significant factor for TP removal. For the 24-hour settled liquid manure that had a TP concentration in the range of 362 to 401 mg l-1 and as alum dose increased up to 1,600 mg l-1, TP removal efficiency increased up to 70%. Then, the rate of increase in TP removal efficiency per increase in alum dose started to decrease and TP removal efficiency reached about 93% at an alum dose of 3,000 mg l-1. Sequential alum dosing improved the TSS removal efficiency while it had no effect on TP removal efficiency. The mass ratio of removed TSS/applied alum increased from about 0.38, during a one-step dosing of alum at a concentration of 1,600 mg l-1, to about 0.58 during a two-step dosing of alum at a concentration of 1,600 mg l-1 (i. e., 800 mg l-1 followed by another 800 mg l-1).