The effects of carbon dioxide on neutralization process of acid precipitation by soil have been investigated. In order to estimate the contribution of carbon dioxide contained in soil on the neutralization, a soil sample and an acid solution were shaken in an atmosphere of high concentration of carbon dioxide. Higher concentration of carbon dioxide was, larger amounts of cations were liberated from soil phase. Thus, it was suggested that both oxonium ions originated from dissolution of carbon dioxide in aqueous solution and originally existed in an acid solution might contribute to the cation exchange reaction. Furthermore, in order to estimate the amounts of cation to be liberated by ion-exchange from soil, a constant ‘γ’ was presented instead of the conventional lime-potential. By using ‘γ’, it was able to simply and quantitatively express a cation exchange potential for cations of any oxidation states. Based on both equilibria for cation exchange reaction and for dissollution of carbon dioxide into the solution, the changes of pH value of the solution was simulated under high concentration of carbon dioxide in gas phase, and the simulated values agreed well with the measured ones.

View full abstract

Acetylcholine sensor based on ISFET as a pH sensor, using the immobilized acetylcholine esterase (AChE) in the BSA membrane are reported for the characteristics and for measuring chemicals. We attempted the application of an enzyme sensor based on ISFET as an effective and simple potentiometric sensor for the detection of chemicals, as irreversible and reversible inhibitors. New data on the analysis of chemicals are reported using the present acetylcholine sensor based on the inhibition of the immobilized AChE. Reactivation of immobilized AChE after inhibition with reversible and irreversible inhibitors, was carried out using a mixture of acetylcholine and pyridine-2-aldoxime methiodide (PAM). The detection for PHC and Nicotine as reversible inhibitors, and Malathion and Dimethoate as irreversible inhibitors was found to be in the ranges of 5×10^-5-5×10^-4 M, 10^-5-10^-4 M, 10^-6-10^-4 and 2.5×10^-5-10^-3 M, respectively.
The present study was also developed for an electrochemical sensor for toxic substances which works by measuring the inhibition of the enzyme activity. We suggested that these inhibition rates (e.g., I₅₀) by the biosensor may be important as a biological index to biological systems with regard to toxic matters.

View full abstract

Benthiocarb was detected in raw water but not in processed tap water. This was attributed to chlorination in the filtration process at water purification plants. A study was conducted to identify the degradation products and to elucidate the degradation characteristics. Concentrations of the degradation products in tap water were also determined.
The degradation products identified in the regions of differents pH values, i.e. acidic, neutral and basic, were p-chlorotoluene, p-chlorobenzaldehyde, p-chlorobenzyl chloride, p-ethyl chlorobenzoate, p-chlorobenzyl acetate, p-chlorobenzyl alcohol, p-chlorobenzoic acid and three other products. The difference in the amount of products was large when compared among the regions of different pH values. A small quantity of benthiocarb remained intact in the basic region when compared to the acidic or neutral region.
The total amount of identified degradation products was about 3% at the acidic region, but the amount gradually increased with the rise of pH value, amounting to about 20% at the basic region. The products other than those identified were assumed to be aliphatic fatty acids, carbon dioxide, water and cyclic molecular sulfur. The more acidic region of pH value became, the more degradation to carbon dioxide, water and cyclic molecular sulfur proceeded. Chlorination for benthiocarb included mainly oxidization reaction and partly chlorine addition reaction, chlorine substitution reaction and reaction with fellow degradation products.
Among the identified degradation products, p-chlorotoluene, p-chlorobenzaldehyde, p-chlorobenzyl chloride, p-chlorobenzyl alcohol, p-chlorobenzoic acid were detected in the tap water at our research laboratories. p-Chlorobenzaldehyde, p-chlorobenzyl chloride, p-chlorobenzyl alcohol in the order of ng·l^-1 were detected in the tap water during the months when benthiocarb was being used. Among degradation products, p-chlorobenzyl chloride in the tap water was derived from benthiocarb chlorination.

View full abstract

In this study, characteristics of bacterial affinity to activated carbon (AC) and removal potentiality of TOC by biological activated carbon (BAC) were examined in batch culture experiment. With the desorption procedure of bacteria, ultrasonication for 3 min at 40W followed by vortexing for 10 sec was the favorable condition. The strength of bacterial affinity was estimated by enumeration of the desorbed bacteria from the AC with fluorescense microscope and the residual bacteria on the AC was certified with scanning electron microscope. The order of strength was as follows. Pseudomonas ovalis > Eschrichia coli > Acinetobacter calcoaceticus > Bacillus subtilis > Micrococcus luteus.
In the study of TOC removal, removal efficiency by the five kind of BAC was quite different in the peptone-culture broth as a substrate for bacteria. The removal without BAC system with M. luteus was over 18% . The maximum removal of 43% was obtained from the BAC system with B. subtilis, while in case of the system with M. luteus the minimum removal of 2% was observed.

View full abstract

Effects of upflow velocity on the biofilm physical properties in items of biofilm thickness, biofilm density and biomass per unit surface area of support particles were investigated by using lab-scale anaerobic fluidized bed reactors fed with a synthetic wastewater (a mixture of skimmilk and sucrose ; 2,000 mg-COD·l^-1). Four identical reactors were operated for a period of 100 days in parallel at different upflow velocities, i. e., 4, 7, 14 and 25m·hr^-1. The initial biofilm formation process was categorized into three types.
For the runs at 14 and 25m·hr^-1, direct adhesion of inoculum sludge onto the carrier surface took place promptly, and the biofilm thickness developed up to 200 μm within only 1 to 2 days, and then decreased eventually to 100 μm. On the contrary the biofilm density increased consistently up to 10.2 mg·cm^-3 and 4.4, respectively.
As for the run at 7m·hr^-1, the biofilm thickness increased gradually to 100 μm with an increase in the biofilm density up to 14.4mg·cm^-3. Granulated sludge in the size ranging 1 to 5mm and containing several carriers was formed at the lowest upflow velocity of 4m·hr^-1.
The occurrence of initial adhesion led to shorten the period for which the biomass per unit surface attained the saturation values. The biofilm density was a more useful factor to determine the biomass per unit surface.

View full abstract