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Water purification system by using the biofilter for long-term experiment equipment with aquatic animals for the space station.

We have developed a water purification system that enables long-term experiment with aquatic animals for 90 days or more on the space station. We designed the system that combined a biofilter for ammonia removal (nitrification) with another for nitrate removal (denitrification). The experiment with goldfish was for 90 days with an aquatic animals' examination device. The equipment consists of a fish tank, a filter module, pumps, and an artificial lung for gas exchange. The goldfish were kept in the tank without any water replacement throughout the experiment. When a filter module consists of adsorbents without bacteria, the concentration of the nitrite and ammonia begin to increase so that the goldfish die. On the contrary, neither ammonia nor nitrite accumulated throughout the experiment, and the concentration of T-N also maintained 30 ppm or less when the combined biofilter was used. Moreover, no fish died throughout the period. The water purification system with biofilter enabled us to examine the long-term life support testing. We also report a new denitrification (correction of dentrification) method for the life support system.

Animals↗

Application of toxicity monitor using nitrifying bacteria biosensor to sewerage systems.

Toxic substances may be included in wastewater influent and can damage biological processing of wastewater treatment, therefore continuous toxic-monitoring of wastewater influent is needed. This paper describes the potential toxic-monitoring applications of the toxicity monitor using a nitrifying bacteria biosensor to sewerage systems. The results of sensitivity tests show that aspects of wastewater do not affect the sensor sensitivity and confirm that the sensor can be applied to wastewater monitoring as it is. The monitor with a prototype of filtration system installed in a wastewater treatment plant is able to operate continuously for one month at least after the modification of filtration system and the optimization of operation conditions.

Biosensing Techniques↗

Toxicity assessment of 255 chemicals to pure cultured nitrifying bacteria using biosensor.

The bioassay has been attracting attention as a method of toxicity assessments of micropollutants in the environment. In this study, we report the characteristics (selectivity and sensitivity) of the nitrifying bacteria biosensor for 255 kinds of chemicals as a model of chemical contaminant in the environment and the results of evaluation of mixed samples of several substances. In the nitrifying bacteria respiration inhibition test using the biosensor, 56 chemicals were detected. It was found that this biosensor is especially sensitive to seven chemicals that have a thiocarbonyl functional group (>C=S), such as a thioamide group of thiocarbamate group. These chemicals are considered to specifically inhibit AMO by chelation of copper. The samples consisted of a mixture of seven types of anilines that inhibit respiration in the bacteria, a mixture of five types of chlorophenols, and a mixture of eight types of substances that contain thiocarbonyl groups were examined. All of the mixed samples inhibited the respiration of the nitrifying bacteria more than 10% by the inhibition rate, and observed a synergistic effects of the substances in the samples.

Aniline Compounds↗

[Effect of fertilizers on the number of bacteria involved in the turnover of nitrogen in pond water of the Astrakhan Region].

The type of intensification affects the distribution of bacteria involved in turnover of nitrogen in pond water. Green fertilizers (reed) stimulate the number of nitrogen-fixing bacteria, and the number and activity of nitrifying bacteria, to a higher degree than nitrogen and phosphorus fertilizers. Reed is recommended as the main means for intensification of spawning ponds of the Astrakhan Region.

Azotobacter↗

Effects of seawater salinity on nitrite accumulation in short-range nitrification to nitrite as end product.

The effect of seawater salinity on nitrite accumulation in short-range nitrification to nitrite as the end product was studied by using a SBR. Experimental results indicated that the growth of nitrobacteria was inhibited and very high levels of nitrite accumulation at different salinities were achieved under the conditions of 25-28 degrees C, pH 7.5-8.0, and the influent ammonia nitrogen of 40-70 mg/L when seawater flow used to flush toilet was less than 35% (salinity 12393 mg/L, Cl- 6778 mg/L) of total domestic wastewater flow, which is mainly ascribed to much high chlorine concentration of seawater. Results showed that high seawater salinity is available for short-range nitrification to nitrite as the end product. When the seawater flow used to flush toilet accounting for above 70% of the total domestic wastewater flow, the removal efficiency of ammonia was still above 80% despite the removal of organics declined obviously (less than 60%). It was found that the effect of seawater salinity on the removal of organics was negative rather than positive one as shown for ammonia removal.

Ammonia↗

Development of nitrogen-removal bioreactor using poly(lactic acid) as an energy source.

To control nitrogen such as ammonia in a rearing water of aquatic animals, we developed new bioreactor capable of both nitrification and denitrification. It was consisted of gel-plate immobilized microorganisms and a biodegradable plastic plate composed of three kind of poly(lactic acid) as an energy source of denitrification. When batch treatment experiment by the bioreactor was continuously carried out with an artificial rearing water containing ammonia, nitrogen-removal rate of the bioreactor was approximately 3 g-N/d/m2-gel surface and the activity was maintained for over 3 month without additional energy source. Therefore, the bioreactor would be effective to control nitrogen concentration in rearing water of a closed water circulating system for aquatic animals.

Ammonia↗