Meteorological factors and water quality changes of Plateau Lake Dianchi in China (1990-2015) and their joint influences on cyanobacterial blooms.

Cyanobacterial blooms (CBs) in eutrophic lakes can cause various harmful issues to both humans and animals, disturb drinking water supply, and devastate lake ecosystems. Although great progresses have been made in many lakes from China and abroad on CBs prevention, mitigation and control, systematic research on the influencing factors of CBs in hypereutrophic plateau Lake Dianchi over a long time span is so far unavailable. This study comprehensively generalized both meteorological and water quality changes in Lake Dianchi during 1990-2015 on both yearly and monthly basis, separated Caohai from Waihai of Lake Dianchi regarding water quality variations, and investigated the individual and joint influencing meteorological and water quality factors on CBs using Spearman correlation, principal component analysis, and multivariate linear stepwise regression. Four specific lake regions, i.e. Caohai, northern Waihai, central Waihai, and southern Waihai, were respectively analyzed due to significant water quality heterogeneity. Results indicated that mild temperatures, low wind velocities, and hypereutrophic water conditions all favor CBs in Lake Dianchi, and the significant temperature rising trend may exacerbate severer CBs in the future. Despite configuration differences, the first principal components on CBs in the four sub-regions of Lake Dianchi were all consisted of meteorological factors, while water quality parameters especially total phosphorus concentrations contributed to the second principal component. Quantification of joint meteorological and water quality influencing factors on CBs needs further improvement, and largely relies on the accuracy of future weather forecasts, in order to set the goal of water quality improvement in each specific lake region for effective CBs management.

[Color and Nitrogen Removal from Synthetic Dye Wastewater in an Integrated Hydrolysis/Acidification and Anoxic/Aerobic Process].

Azo dye is a type of reactive dyes with a stable structure. Its discharge into the environment affects the human health and growth of aquatic organisms. The color and nitrogen removal through an integrated hydrolysis/acidification and anoxic/aerobic (AO) process for the treatment of wastewater containing reactive red 2 (RR2) was investigated. The color, chemical oxygen demand (COD), and ammonia nitrogen were removed efficiently, with removal efficiencies of 71.0%, 92.2%, and 83.5%, respectively. The dominant azo dye degradation bacterium in the hydrolysis/acidification reactor was Desulfovibrio. The dominant nitrifying bacterium in the AO reactor was Nitrospira, while the denitrifying bacteria were Thauera and Dechloromonas. When increasing the hydrolysis/acidification temperature from 25℃ to 35℃, the color removal efficiency improved by 141.2%. When the concentration of COD increased from 200 mg·L-1 to 800 mg·L-1 at 25℃, the color removal efficiency improved by 208.9%. Nitrite accumulation occurred in the AO reactor with a nitritation efficiency of 73.8%. The RR2 did not inhibit the nitrification, while aniline inhibited the nitrification. At an aniline concentration of 6 mg·L-1, the ammonia oxidation was the slowest.

Enhanced growth and fatty acid accumulation of microalgae Scenedesmus sp. LX1 by two types of auxin.

Microalgae are potential candidates for the production of valuable products, such as renewable biodiesel, health products and pigments. However, low biomass productivity has restricted their large-scale applications. In this study, the effects of two auxins (one natural type of indole-3-acetic acid (IAA) and the other synthetic type of 2,4-dichlorophenoxyacetic acid (2,4-D)) on the growth and fatty acid methyl esters (FAMEs) production of a freshwater microalgae Scenedesmus sp. LX1 were investigated. Both auxins showed a "low dosage-promotion and high dosage-inhibition" effect on the growth and FAMEs accumulation. The optimum dosage of IAA and 2,4-D were 1mgL-1 and 0.1mgL-1, respectively. Moreover, the IAA could increase the monounsaturated fatty acid content. The auxins may promote the growth by enhancing the photosynthetic activity through increasing chlorophyll contents. Therefore, auxin significantly enhanced microalgal growth and FAMEs accumulation, and has a potential for application in developing efficient microalgal cultivation.

Using straw hydrolysate to cultivate Chlorella pyrenoidosa for high-value biomass production and the nitrogen regulation for biomass composition.

Heterotrophic cultivation of Chlorella pyrenoidosa based on straw substrate was proposed as a promising approach in this research. The straw pre-treated by ammonium sulfite method was enzymatically hydrolyzed for medium preparation. The highest intrinsic growth rate of C. pyrenoidosa reached to 0.097h-1 in hydrolysate medium, which was quicker than that in glucose medium. Rising nitrogen concentration could significantly increase protein content and decrease lipid content in biomass, meanwhile fatty acids composition kept stable. The highest protein and lipid content in microalgal biomass reached to 62% and 32% under nitrogen excessive and deficient conditions, respectively. Over 40% of amino acids and fatty acids in biomass belonged to essential amino acids (EAA) and essential fatty acids (EFA), which were qualified for high-value uses. This research revealed the rapid biomass accumulation property of C. pyrenoidosa in straw hydrolysate medium and the effectiveness of nitrogen regulation to biomass composition at heterotrophic condition.

[Nitrous oxide emission during denitrification for activated sludge acclimated with methanol as the organic carbon].

Denitrification of wastewater is one of the important sources of nitrous oxide (N2O). In this study, denitrifies were acclimated in a sequencing batch reactor with methanol and nitrate (NO3(-) -N) as the electron donor and acceptor, respectively. N2O emission during denitrification was examined both in typical cycles and in batch experiments under conditions of different electron acceptors, carbon/nitrogen (C/N) ratios and initial nitrite (NO2(-)-N) concentrations. With methanol as the organic carbon, the N2O emission was high with NO2(-)-N as the electron acceptor and the N2O emission was low with NO3(-) -N as the electron acceptor. The C/N ratios affected the emission of N2O by affecting activities of denitrifiers, and both the activity of denitrifiers and the emission of N2O decreased with decreasing C/N ratios. The N2O emission increased with increasing initial NO2(-) -N concentrations, and a certain range of NO2(-) -N concentrations enhanced the activity of denitrifiers. The N2O emission could be correlated very well with initial NO2(-) -N concentrations.

[Effects of SRT and carbon concentration on the PHB in the anaerobic/aerobic alternative operating SBR process].

Effects of SRT and carbon concentration on the PHB of the anaerobic/aerobic SBR process are studied. The results show that by the order of SBR51,SBR10 and SBR52,the maximum PHB content of MLVSS were 9.8%, 5.72% and 18.89%, respectively, while carbon translating ratios were 46%, 34% and 36.3% during the first 20min of aerobic phase and PHB forming rate were 196.6mg/(L x h), 140mg/(L x h) and 295.35mg/(L x h). PHB degradation rate can be described with a first order degradation rate with respect to the PHB content of the cells. Reclamation of PHB should consider from several factors. Carbon concentration gradient is the main factor influencing PHB formation under batch experiment.

[Effect of carbon and nitrogen sources on the accumulation of poly-beta-hydroxybutyrate by purple non-sulfur photosynthetic bacteria].

The effect of carbon and nitrogen sources on the accumulation of Poly-beta-Hydroxybutyrate (PHB) by purple non-sulfur photosynthetic bacteria (PNSB)was investigated. The results showed that ammonia nitrogen and organic nitrogen could benefit the PNSB accumulating PHB; under certain ratio of carbon and nitrogen low carbon concentration can accumulate more PHB, but high carbon concentration is better for PNSB accumulating PHB with the growth of PNSB. As to different substrates, butyrate is the best for accumulating of PHB, but acetate is better and propionate is the poorest. Mixed substrate with butyrate as the main content are better than single substrate; carbon dioxide have certain effect on the PNSB accumulating PHB, and high carbon dioxide concentration can improve PHB content when using acetate or butyrate as substrate.