An advanced oxidation process using ionized gas for wastewater treatment.

This study on removing non-degradable materials in wastewater focused primarily on advanced oxidation methods such as ozone, ozone/UV and ozone/H2O2. Wastewater treatment using an ionized gas from plasma has been actively progressing. The ionized gas involves reactive species such as O2+, O2- cluster, O radical and OH radical. Since the ionized gas method has such outstanding characteristics as relatively simple structures, non-calorification, non-toxicity and low electricity consumption, it evidently of interest as a new process. A series of experiments were conducted to demonstrate the feasibility of ionized gas as a useful element for the diminution of nondegradable organic matters. On the other hand, a large amount of organic matters were changed to hydrophilic and the compounds containing aromatic functional group gradually decreased. The results implied that the ionized gas has been able to degrade the non-biodegradable organic matters. Therefore, the oxidation process by using an ionized gas process could be considered as an effective alternative unit in water and wastewater treatment plants.

Combined effect of biopesticides on the digestive enzymatic profiles of Cnaphalocrocis medinalis (Guenée) (the rice leaffolder) (Insecta: Lepidoptera: Pyralidae).

Plant extracts, especially botanical insecticides, are currently studied more and more because of the possibility of their use in plant protection. Many of the natural plant compounds and organic compounds used in the control of insect pests are known to affect digestive enzymes. When fed a diet of rice leaves treated with botanical insecticides and bacterial toxins in bioassays, activities of the digestive enzymes protease, amylase, and lipase in the rice leaffolder larvae are affected. Digestive enzyme activities were affected by botanical insecticides and bacterial toxins individually and in combination. When combined, the effect was more severe at low concentration. There were statistically significant differences (P < or = 0.05) in enzyme activities in combined and individual treatments. The combination of Btk and botanical insecticides caused a two-fold decrease in enzyme activity even at reduced concentration. Clear dose-response relationships were established with respect to enzyme activity. A synergistic effect of botanical insecticides and bacterial toxins was found when combined in low doses. These effects are most pronounced in early instars.

Efficacy of Melia azedarach L. extract on the malarial vector Anopheles stephensi Liston (Diptera: Culicidae).

Methanolic extracts of leaves and seeds from the chinaberry tree, Melia azedarach L. (Meliaceae) was tested against mature and immature mosquito vector Anopheles stephensi Liston (Diptera) under laboratory condition. The extract showed strong larvicidal, pupicidal, adulticidal, antiovipositional activity, repellency and biting deterency. The M. azedarach seed and leaf extracts were used to determine their effect on A. stephensi adults and their corresponding oviposition and consequent adult emergence in comparison with the control. The seed extracts showed high bioactivity at all doses, while the leaf extracts proved to be active, only in the higher dose. Results obtained from the laboratory experiment showed that the seed extracts suppressed the pupal and adult activity of A. stephensi even at low dose. In general, first and second instar larvae were more susceptible to both leaves and seed extracts. Clear dose-response relationships were established with the highest dose of 2% plant extract evoking 96% mortality. Entire development of A. stephensi was inhibited by M. azedarach treatment. Less expensive (less than 0.50 US dollars per 1 kg seed), naturally accruing bio-pesticide could be an alternative for chemical pesticides.

Effect of neem limonoids on lactate dehydrogenase (LDH) of the rice leaffolder, Cnaphalocrocis medinalis (Guenée) (Insecta: Lepidoptera: Pyralidae).

Neem is derived from the neem tree Azadirachta indica A. Juss. (Meliaceae), and its primary insecticidal component is the tetranortriterpenoid azadirachtin and other limonoids. The effect of neem limonoids azadirachtin, salannin, deacetylgedunin, gedunin, 17-hydroxyazadiradione and deacetylnimbin on enzyme lactate dehydrogenase (LDH) activity of the rice leaffolder (RLF) Cnaphalocrocis medinalis (Lepidoptera: Pyralidae) larvae was investigated. There was a decrease in enzyme activity relative to the control at all concentrations tested. When fed a diet of rice leaves treated with neem limonoids in bioassays, gut tissue enzyme, LDH levels in rice leaffolder larvae are affected. These results indicate neem limonoids affect LDH activity. These effects are most pronounced in early instar larvae. Azadirachtin was the most potent in of all the limonoids in all experiments indicating strong enzyme inhibition. Clear dose-response relationships were established with respect to LDH activity.

Adsorption of dichloromethane from water onto a hydrophobic polymer resin XAD-1600.

Dichloromethane is one of the chlorinated volatile organic compounds (CVOCs) that contaminate the waters. Especially, the dichloromethane used as a solvent in polycarbonate synthesis, is dissolved in wastewater with the saturated solubility of 17,220 mg L(-1), which is several times that of other CVOCs. Thus, it is reasonable to recover the dichloromethane dissolved in water instead of destruction based on the economic point of view. To study on the recovery of the dichloromethane, adsorption equilibrium and column dynamics were investigated using a hydrophobic polymer resin (XAD-1600) without the ion-exchange functional groups. In addition, a hydrophilic polymer resin (XAD-7) and an activated carbon (DY-GAC) were chosen for comparison. Conventional two- or three-parameter models such as the Langmuir, Freundlich, or Sis equations could not fit the adsorption equilibrium data of two polymer resins obtained over the entire range of concentration (1-200 mol m(-3)). They were well fitted by a hybrid model consisting of Langmuir and BET (Brunauer-Emmett-Teller) equations. The adsorption amount at high concentration was in the order of XAD-1600>XAD-7>DY-GAC on a mass basis. To confirm the possibility of using resin as a sorbent for the removal of dichloromethane, adsorption breakthrough curves were measured under key operating conditions such as the concentration, the flow rate, and the column length. Moreover, desorption from polymer resins adsorbed with dichloromethane was conducted by using pure water only as a desorbate. A simple dynamic model was also formulated to describe the adsorption breakthrough curves of dichloromethane from XAD-1600, XAD-7 and DY-GAC columns.

Removal of residual COD in biologically treated paper-mill effluent and degradation of lignin using nonthermal plasma unit.

This manuscript focused on the degradation behavior of lignin and the reduction of residual COD in the biologically treated paper-mill effluent by means of ionized gas from nonthermal plasma unit. The removal efficiencies of COD, lignin, and color after treated with ionized gas were over 95, 93, and 97%, respectively. It has been found that the degradation of aromatic ring has been proved by FTIR, 1H NMR and UV spectra. The degradation of lignin through ionized gas was accompanied with the increase of SO4(2-) and the decrease in pH. The results show that the residual COD in the biologically treated paper-mill effluent contains NBD matter with aromatic ring compounds. Also NBD organic matter such as aromatic ring in effluent treated with ionized gas was degraded. The residual COD declined by 60% at the ionized gas flow rate 5 L/min and HRT 30 min.