Improvement of Physico-mechanical Properties of Chitosan Films by Photocuring with Acrylic Monomers

Natural polymer, chitosan was obtained from dried prawn shell waste through the preparation of chitin and was characterized. Thin film of chitosan was prepared by casting method from its 2% chitosan solution. Mechanical properties like tensile strength (TS), elongation at break (Eb) of chitosan film were studied. Five formulations were developed with 2-ethyl-2-hydroxy methyl-1,3-propandiol trimethacrylate (EHMPTMA), a trifunctional monomer and 2-ethylhexyl acrylate (EHA), a monofunctional monomer in the presence of photoinitiator Darocur-1664 (2%). The film was soaked in those monomer formulations in dissimilar soaking times and irradiated under UV-radiation at different radiation intensities for the improvement of the properties of chitosan film. The cured films were then subjected to various characterization tests like TS, Eb, polymer loading (PL), water absorbency, gel content etc. The formulation, containing 25% EHMPTMA and 73% EHA showed the best performance at 10th UV passes of UV radiation for 4 min soaking time.     

The Effectiveness of Aeration Recirculation in Controlling VOC Emissions from Publicly Owned Treatment Works

Abstract

The effects of aeration recirculation on oxygen transfer and the fate of five volatile organic compounds (VOCs) commonly found in publicly owned treatment works (POTWs) influent are studied using various modeling approaches. The five compounds are benzene, chloroform, methylene chloride, toluene, and trichloroethylene. The models predict that the overall oxygen transfer efficiency can be increased by 96.7% at 50% aeration recirculation with only a 9.6% drop in oxygen transfer rate. The emission reductions and biodegradation improvements are compound specific; for the compounds investigated here, about 40% emission reductions and 16% biodegradation increases can be achieved at 50% aeration recirculation. The temperature effect on the VOC fate mechanisms is also investigated. Overall, the model predictions reveal that up to 50% aeration recirculation is effective in controlling VOC emissions.     

Nutritional assessment of transgenic sweetpotato on body weight, lipid, and protein status in hamsters

The objectives of the present study were to evaluate the nutritional quality of genetically modified sweetpotato (genotype PI318846-3) on growth, lipid metabolism, and protein metabolism of hamsters. Three different diets made with transgenic and nontransgenic sweetpotato protein flour including a control diet with casein were fed to male Golden Syrian hamsters for 28 days. The protein efficiency ratio (1.35 +/- 0.01) of the transgenic sweetpotato protein diet was significantly higher (p<0.05) than the nontransgenic sweetpotato and control diets. Plasma albumin and plasma total protein concentrations of hamsters fed the sweetpotato diets were significantly lower (p<0.05) than that of the control. The casein diet (control) produced hypercholesterolemia in hamsters, whereas sweetpotato diets maintained lower plasma and liver total and LDL-cholesterol concentrations in hamsters. Sweetpotatoes contain less amount of protein to maintain the normal animal growth; however, transgenic sweetpotato has good quality protein that supported the growth of hamsters better than nontransgenic sweetpotato.     

A technical and economic comparison of biofiltration and wet chemical oxidation (scrubbing) for odor control at wastewater treatment plants

An economic and technical comparison of two odor control systems, a biofilter and a chemical wet scrubber, was conducted over a 1-year time period at a large municipal wastewater treatment plant. The biofilter system was designed to remove hydrogen sulfide gas and other oxidizable sewage odors from four covered gravity sludge thickeners, a gravity sludge thickener effluent channel and an influent splitter box for the gravity sludge thickeners. The sodium hypochlorite/sodium hydroxide wet scrubber was designed to control hydrogen sulfide gas and other oxidizable sewage odors from the covered primary settling tanks, influent distribution channels and effluent channel, and the mixing tank effluent channel. The technical comparison comprised their overall removal rates and efficiencies based on inlet H₂S concentrations and other operating variables. The economic comparison was designed to provide the cost per cubic meter of H₂S removed for each system. Influent and effluent gas samples were collected on a weekly basis. H₂S concentration levels were determined through the use of gas chromatography with a flame photometric detector. The results showed that the H₂S inlet gas concentration has a seasonal change with a maximum value occurring in August and September. The effluent H₂S concentration was lower than 2 ppm_v for both systems for most of the samples. The efficiency for both the biofilter and wet scrubber was above 95%, and was related to the operating and ambient conditions. The economic comparison revealed that the actual unit cost for the biofilter was higher than for the wet scrubber (U.S.160 /m < SUP > 3 < /SUP > H < SUB > 2 < /SUB > S removed versus U.S.160 /m³ H₂S removed versus U.S.131 /m³ H₂S removed). For both the biofilter and the wet scrubber, the investment costs are affected by the size/scale of the system, the design flow and other factors. For these systems, the mulch change costs, chemical usage costs, maintenance costs and power usage costs were mainly dependent on the actual odor gas loadings which showed substantial seasonal fluctuations as a function of the seasonal temperature. The worst case conditions reported here indicate that the H₂S concentrations generated during the summer months should be used to determine the design load.