Application and microbial ecology of psychrotrophs in domestic wastewater treatment at low temperature.

The feasibility of a bunch of screened psychrotrophs being applied to low-temperature wastewater treatment was investigated. The screened psychrophillic strains are capable of growth at a broad temperature-range from 0 to 40 °C and exhibit a preferable TTC-dehydrogenase activity at low temperature (4-10 °C). Along the sharply fluctuant temperatures (25-4-25 °C), the screened psychrotrophs (compared with the indigenous mesophiles) demonstrate less fluctuations of COD removal and more rapid recovery after temperature shocks. COD removal of approximate 80% was recorded by single psychrotrophs (while only 10% by single mesophiles) at low temperature (4 °C). Soft polyurethane foam showed better performance for psychrotrophs immobilization, with the optimal filling rate of 30% (v/v) in the bioreactor. The observation shows that the immobilized psychrotrophs demonstrated a relatively high performance on both conventional and emerging organic contaminants removals at low temperature. In order to check the feasibility of the screened psychrotrophs in treating actual domestic wastewater, a pilot-scale ICABR bioreactor was operated firstly at low temperature (4 °C) and then at seasonal varying temperatures (0-30 °C) for one year, the influent COD of 150-600 mg L-1 was efficiently reduced to 40 ± 18 mg L-1 under the conditions of an overall hydraulic retention time of 10 h. Furthermore, psychrotrophs performed stably as the predominant bacteria family during the whole operation. This study provides evidence that microbial intensification with psychrotrophs was a feasible strategy to improve the efficiency of conventional wastewater treatment process at low temperature.

Study on the removal of indoor VOCs using biotechnology.

With the improvement of living standard and civil building innovation, large numbers of building materials and decoration are being used. The emission of gaseous organic pollutants such as formaldehyde, benzene, toluene and xylene from these materials may trigger immediate or persistent potential harm to human health. In this study, with the combination of bake-out exhaust, biological treatment was applied to deal with volatile organic compounds (VOCs). Four bacterial strains were isolated from the biotrickling filter and were identified according to physiological and biochemical tests as well as bacterial fatty acids. As a result, they were characterized as Pseudomonas sp., Kocuria sp., Arthrobacter sp. and Bacillus sp. Under the conditions of gaseous flow rate of 600 L/h, surface liquid velocity of 3.14 m/h, pH 6-7 and temperature of 30 degrees C, VOCs could be degraded by using biological method before they were exhausted to the environment. For formaldehyde, benzene, toluene and xylene in the air stream with the concentration of 0-6.5 mg/m(3), 2.2-46.7 mg/m(3), 0.5-28.2 mg/m(3) and 4.1-59.0 mg/m(3), VOCs removal efficiencies of biotrickling filter ranged in about 100%, 65-70%, 93% and 85-90%, respectively.

[Selection and kinetic mechanism of psychrotrophs in low temperature wastewater treatment].

A study was carried out taking low temperature domestic wastewater as target in laboratory, the composition of bacteria in activated sludge was analyzed and the degradation kinetics of organics was investigated. Six preponderant psychrotrophs were selected out, belonging to Zoogloea, Aeromonas, Flavobacterium, Micrococcus, Bacillus and Pseudomonaus, respectively. Results show that TTC-dehydrogenase activity of the psychrotroph is 25.44 mg/(L x h) which is 20.5 times more than that of ordinary activated sludge at 4 degrees C. The efficiency of COD biodegradation by psychrotrophs at low and normal temperature is 80.9% and 73.4%, respectively. Mesophilic bacteria almost lost their activity at low temperature. Kinetic analysis shows that biodegradation of organics by psychrotrophs at low and mesothermal temperature as well as mesophilic bacteria at mesothermal temperature are in accordance with the model of first-order reaction. Psychrotrophs, which assure the removal efficiency of organic pollutants at low and normal temperature, could keep the uniform reaction velocity as the mesophilic bacteria and also adapt wide ecological amplitude of temperature. Efficient psychrotrophs were immobilized on soft polyurethane foams which acted as carriers in the experiment at 4 degrees C, as a result of that, the removal efficiency of COD was increased about 18% higher than that of mobilized ones at low temperature, the biodegradation kinetics of COD by immobilized psychrotrophs also followed the first-order reaction model. With glucose in water as the source of nutriment, the reaction velocity of immobilized bacteria is 2.35 times higher than that of the mobilized ones. By the immobilized psychrotrophs biodegradation of varied nutriment, the effluent could achieve the first-degree B of pollutants discharge standard for municipal wastewater treatment plant.

Gridded inventories of historical usage for selected organochlorine pesticides in Heilongjiang River Basin, China.

The use of technical HCH (1, 2, 3, 4, 5, 6-hexachlorocyclohexane), DDT (dichlorodiphenyltrichloroethane) and lindane in Heilongjiang River Basin (HRB) of China was studied. Between 1952 and 1984 the total usage in the HRB was 108900 t for technical HCH, and 4900 t for DDT, respectively, and the use of DDT due to dicofol application in the HRB was 220 t from 1984 to 2003. The usage of lindane in HRB was 109 t from 1991 to 2000. The results show that the highest technical HCH use (41800 t) in HRB was on maize, accounting for 38.3% of the total usage on all crops, followed by the use on wheat (28000 t, 25.7%) and on soybean (26600 t, 24.4%). The highest DDT use (2300 t) was on soybean, accounting for 46.8% of the total usage on all crops, followed by the use on maize (1500 t, 31.3%) and on sorghum (600 t, 13.2%). The major use of lindane was mainly on wheat. Gridded usage inventories of these three OCPs (organochlorine pesticides), in HRB with a 1/6 degrees latitude by 1/4 degrees longitude resolution have been created by using different gridded cropland as surrogates. Some soil samples have also been collected in HRB. Data of usage and soil concentrations of sigma HCH in HRB match quite well to those in Shanghai region, and much higher soil concentration of sigma DDT in Shanghai region could be due to much heavier dicofol use in this region.

Isolation and characterization of deodorizing bacteria for organic sulfide malodor.

Strain JII screened out from different odor origins can efficiently degrade methyl mercaptan and ethanethiol whereas has no ability to remove dimethyl sulfide. The results indicated that the strain JII breaks only the C-SH bond. The optimum temperature and pH of JII are 20-30 degrees C and 6.0-8.3 respectively. A systematic identification method-16S rDNA gene sequence comparison, for deodorizing bacteria was carried out. The 16S rDNA gene sequence analysis of strain JII showed the highest level of 97% homology to Rape rhizosphere.