Quick vaporization of sprayed sodium hypochlorite (NaClO(aq)) for simultaneous removal of nitrogen oxides (NOx), sulfur dioxide (SO2), and mercury (Hg0)

Sodium hypochlorite (NaClO) has been widely used as a chemical additive for enhancing nitrogen oxide (NO_x; NO + NO₂), sulfur dioxide (SO₂), and mercury (Hg⁰) removals in a wet scrubber. However, they are each uniquely dependent on NaClO_(aq) pH, hence making the simultaneous control difficult. In order to overcome this weakness, we sprayed low liquid-to-gas (L/G) ratio (0.1 L/Nm³) of NaClO_(aq) to vaporize quickly at 165 °C. Results have shown that the maximized NO_x, SO₂, and Hg⁰ removals can be achieved at the pH range between 4.0 and 6.0. When NO_x and Hg⁰ coexist with SO₂, in addition, their removals are significantly enhanced by reactions with solid and gaseous by-products such as NaClO_(s), NaClO_2(s), OClO, ClO, and Cl species, originated from the reaction between SO₂ and NaClO_(aq). We have also demonstrated the feasibility of this approach in the real flue gases of a combustion plant and observed 50%, 80%, and 60% of NO_x, SO₂, and Hg⁰ removals, respectively. These findings led us to conclude that the spray of NaClO_(aq) at a relatively high temperature at which the sprayed solution can vaporize quickly makes the simultaneous control of NO_x, SO₂, and Hg⁰ possible.

Implications: The simple spray of NaClO_(aq) at temperatures above 165 °C can cause the simultaneous removal of gaseous NO_x, SO₂, and Hg⁰ by its quick vaporization. Their maximized removals are achieved at the pH range between 4.0 and 6.0. NO_x and Hg⁰ removals are also enhanced by gaseous and solid intermediate products generated from the reaction of SO₂ with NaClO_(aq). The feasibility of this approach has been demonstrated in the real flue gases of a combustion plant.     

Effect of surfactant alkyl chain length on soil cadmium desorption using surfactant/ligand systems

The effect of surfactant alkyl chain length on soil Cd desorption was studied using nonionic surfactants of polyethylene oxide (PEO) of PEO chain lengths of 7.5 (Triton X-114), 9.5 (Triton X-100), 30 (Triton X-305), or 40 units (Triton X-405) in combination with the I- ligand. Triplicate 1 g soil samples were equilibrated with 15 ml of surfactant-ligand mixture, at concentrations of 0.025, 0.50 or 0.10, and 0.0, 0.168 or 0.336 mol/l, respectively. After shaking the samples for 24 h, the supernatant fraction was analyzed for Cd content to determine the percent of Cd desorbed from the soil. After five successive washings, 53%, 40% and 25% of Cd had been desorbed by 0.025, 0.050 or 0.10 mol/l of Triton X-114, respectively, in the presence of 0.336 mol/l of I-, whereas with the same conditions, Triton X-100 desorbed 61%, 57% and 56% Cd and either Triton X-305 or Triton X-405 desorbed 51, 40 and 14 to 16% Cd. The most efficient Cd desorption was obtained using 0.025 mol/l Triton X-100 in admixture with 0.336 mol/l I-. Increased surfactant concentration was detrimental to Cd desorption consistent with a process that blocked ligand access to the soil particle surface. After 5 washings,the cumulative cadmium desorption decreased with increasing surfactant alkyl chain length, indicating that the metal-ligand complexes are preferably stabilized by the micelles' hydrophobic octyl phenyl (OP) group rather than by the hydrophilic PEO group. In the absence of ligand, the surfactants alone desorbed less than 1% Cd from the contaminated soil, suggesting that the ligand, rather than the surfactant, extracts the metal, to be subsequently stabilized within the surfactant micelles.     

Performance of an innovative two-stage process converting food waste to hydrogen and methane

This study was conducted to evaluate the performance of an innovative two-stage process, BIOCELL, that was developed to produce hydrogen (H2) and methane (CH4) from food waste on the basis of phase separation, reactor rotation mode, and sequential batch technique. The BIOCELL process consisted of four leaching-bed reactors for H2 recovery and post-treatment and a UASB reactor for CH4 recovery. The leaching-bed reactors were operated in a rotation mode with a 2-day interval between degradation stages. The sequential batch technique was useful to optimize environmental conditions during H2 fermentation. The BIOCELL process demonstrated that, at the high volatile solids (VS) loading rate of 11.9 kg/m3 x day, it could remove 72.5% of VS and convert VS(removed) to H2 (28.2%) and CH4 (69.9%) on a chemical oxygen demand (COD) basis in 8 days. H2 gas production rate was 3.63 m3/m3 x day, while CH4 gas production rate was 1.75 m3/m3 x day. The yield values of H2 and CH4 were 0.31 and 0.21 m3/kg VS(added), respectively. Moreover, the output from the post-treatment could be used as a soil amendment. The BIOCELL process proved to be stable, reliable, and effective in resource recovery as well as waste stabilization.     

Kinetics of soil ozonation: an experimental and numerical investigation

This study investigates the use of ozone for soil remediation. Batch experiments, in which ozone-containing gas was continuously recycled through a soil bed, were conducted to quantify the rate of ozone self-decomposition and the rates of ozone interaction with soil organic and inorganic matter. Column experiments were conducted to measure ozone breakthrough from a soil column. Parameters such as ozone flow rate, soil mass, and ozonation time were varied in these experiments. After ozone concentration had reached steady state, the total organic carbon concentration was measured for all soil samples. The ozonation efficiency, represented by the ratio of soil organic matter consumed to the total ozone input, was quantified for each experiment. Numerical simulations were conducted to simulate experimentally obtained column breakthrough curves. Experimentally obtained kinetic rate constants were used in these simulations, and the results were in good agreement with experimental data. In contrast to previous studies in which soil inorganic matter was completely ignored, our experiments indicate that soil inorganic matter may also promote depletion of ozone, thus reducing the overall ozonation efficiency. Three-dimensional numerical simulations were conducted to predict the efficacy of ozonation for soil remediation in the field. These simulations indicate that such ozonation can be very effective, provided that effective circulation of ozone is achieved through appropriately placed wells.     

Contamination of butyltin compounds in Malaysian marine environments

Concentration of butyltin compounds (BTs), including tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) and total tin (SigmaSn) were determined in green mussel (Perna viridis), 10 species of muscle fish and sediment from coastal waters of Malaysia. BTs were detected in all these samples ranging from 3.6 to 900 ng/g wet wt., 3.6 to 210 ng/g wet wt., and 18 to 1400 ng/g dry wt. for mussels, fish and sediments, respectively. The concentrations of BTs in several locations of this study were comparable with the reported values from some developed countries and highest among Asian developing nations. Considerable concentration of BTs in several locations might have ecotoxicological consequences and may cause concern to human health. The parent compound TBT was found to be highest than those of its degradation compounds, DBT and MBT, suggesting recent input of TBT to the Malaysian marine environment. Significant positive correlation (Spearman rank correlation: r2=0.82, P<0.0001) was found between BTs and SigmaSn, implying considerable anthropogenic input of butyltin compounds to total tin contamination levels. Enormous boating activities may be a major source of BTs in this country, although aquaculture activities may not be ignored.     

Antifouling activity of six nontoxic chemicals on spore attachment of Ulva fasciata

Marine biofouling cause severe damage to all marine technologies. Indiscriminate use of toxic metallic antifouling (AF) chemicals (cuprous oxide and TBT) to control the biofouling in turn greatly affects the flora and fauna of the marine ecosystem. In search of environmentally safe and effective AF agents, six nontoxic AF candidates were studied against the spore attachment of Ulva fasciata. Spore attachment was inhibited at 100 microg of trans-cinnamic acid (TCA) and benzoic acid (BA). Sulfate-coumaric acid (SCA) had no significant effect on the spore attachment. The release rate of BA exhibited a constant release flow. Varied response of U. fasciata spores to AF chemicals and release rate to the surrounding medium are discussed.     

Morphological and molecular comparisons of dominant amphioxus populations in the China Seas

The amphioxi Branchiostoma belcheri, Branchiostoma japonicum and Branchiostoma malayanum are recorded from the coast of China Seas. Six amphioxus populations comprising three Branchiostoma species collected from Hong Kong (southern China), Xiamen (south-eastern China) and Qingdao (northern China) were compared at the morphological and molecular levels. Phylogenetic separations among the species and geographic populations were evaluated by the analysis of 12S ribosomal RNA gene sequences and amplified fragment length polymorphism (AFLP) markers. From morphological characters, B. belcheri is more closely related to B. japonicum than to B. malayanum. However, phylogenetic affinities indicated by both 12S rRNA gene sequences and AFLP analysis showed a more recent phylogenetic splitting of B. belcheri and B. malayanum than that of B. belcheri and B. japonicum. In the AFLP similarity tree, geographic populations of B. japonicum were clustered into different clades. The AFLP data also showed that both B. belcheri and B. japonicum populations in Hong Kong have the highest levels of within-population genetic diversity as compared to that in Xiamen and Qingdao, suggesting that genetic diversity of Branchiostoma decreases from low to high latitudes. Results of hierarchical analysis of molecular variance (AMOVA) also revealed a high level of genetic diversity either for the three B. japonicum populations or the two B. belcheri populations in China Seas. However, genetic variation among the three B. japonicum populations was insignificant, indicating that these populations are genetically connected.     

Sediment characteristics and colonization of soft-bottom benthos: a field manipulation experiment

A field manipulation experiment was carried out to test the effects of sediment characteristics (particle size and organic content) on colonization of soft-bottom benthos. Defaunated mud and sand in experimental trays were exposed at sub-tidal levels of two sites with sandy and muddy sea bottom, and retrieved monthly for examination of benthic composition. Seventy-eight out of the 107 species recorded, and 50% of the dominant species identified in the present study, were common in both the sand and mud trays. Classification analysis revealed higher faunal similarity of benthic composition in both sediment types within each of the two study sites. Results of three-way ANOVA (Sediment, Site and Time) showed that sediment effect was only significant for colonization of bivalves and gastropods, but not for polychaetes, amphipods, total species and individual numbers, or overall benthic diversity and evenness. This suggested that many of the benthic species can colonize both sediment types, and that factors other than sediment particle size and organic content may play a significant role in determining colonization of these species. The faunal composition of the same sediment type between sites was found to be different, indicating that the availability and abundance of benthic larvae/adults may be more important than sediment characteristics in determining benthic settlement. An increase in faunal similarity between mud and sand was observed over the study period, implying that the importance of sediment characteristics to benthic colonization decreased with exposure time. Received: 29 November 1996 / Accepted: 16 January 1997     

Debromination of 1,4-Dibromobenzene and 4,4′-Dibromobiphenyl: A Model for Cleansing of PCBs

The aim of this study is to develop a catalytic method which has advantages over current method to detoxify and degrade environmentally harmful polychlorinated biphenyls (PCBs). A variety of catalysts have been employed in a preliminary study on 1,4-dibromobenzene and 4,4-dibromobiphenyl which may be considered to represent simple analogues of PCBs. The most satisfactory catalysts are those involving [Pd(dppf)] [dppf = 1,1-bis(diphenylphosphino)ferrocene], generated in situ from PdCl2(dppf) or Pd(dppf)2. In the presence of the reducing reagent, namely NaBH4, debromination has been achieved at relative mild conditions with high product yields (> 70%). Thus, our results indicate the possibility of dechlorination of PCBs with such catalysts.     

Practical field application of a novel BOD monitoring system

A biochemical oxygen demand (BOD) monitoring system, based on electrochemically-active bacteria in combination with a microbial fuel cell, has been developed for the purpose of on-site, on-line and real-time monitoring of practical wastewater. A microbial fuel cell that had been enriched with electrochemically-active bacteria was used as the basis of the measurement system. When synthetic wastewater was fed to the system, the current generation pattern and its Coulombic yield were found to be dependent on the BOD5 of the synthetic wastewater. A linear correlation between the Coulombic yields and the BOD5 of the synthetic wastewater were established. Real wastewater obtained from a sewage treatment plant also produced a highly linear correlation between the Coulombic yield and BOD5 in the system. To examine on-site, on-line and real-time monitoring capability, the BOD monitoring system was installed at a sewage treatment plant. Over 60 days, the measurement system was successfully operated with high accuracy and good stability with the measuring period for a sample being 45 min. This application showed that the application of the measurement system was a rapid and practical way for the determination of BOD5 in water industries.