[Distribution Characteristics of Soil Phosphorus Forms and Phosphatase Activity at Different Altitudes in the Soil of Water-Level-Fluctuation Zone in Pengxi River, Three Gorges Reservoir].

Phosphatases play important roles in converting organic phosphorus into inorganic phosphorus in soil. However, studies from this perspective on the water-level-fluctuation zone (WLFZ) of the Three Gorges Reservoir are limited. In this study, phosphatase activity and the forms of phosphorus were analyzed. Soil samples were collected in the river basin of the Penxi River in the WLFZ during a drying period. The correlation between phosphatase activity and phosphorus forms and the impacts of phosphatase activity on the phosphorus forms were analyzed. The results showed that the contents of H2O-Pi, NaHCO3-Pi, and NaOH-Pi in the soils of the WLFZ were higher than those in the soils by the river. In addition, a higher altitude resulted in higher contents of bio-enzymatically hydrolysable phosphorus and NaOH-Po. Furthermore, redundancy analysis (RDA) showed that the contents of organic matter and amorphous Fe and Mn were the main factors affecting soil organic phosphorus forms. The average activities of acid phosphomonoesterase (ACP), alkaline phosphomonoesterase (ALP), phosphodiesterase (PDE) (all in p-NP), and phytase (PAE) (in P) in the soils of the WLFZ were 1.40, 2.60, 0.44, and 11.43 µmol·(g·h)-1, respectively. Moreover, the activities of different phosphatases increased with altitude. Soil plant biomass and microbial biomass were important reasons for the difference in spatial distribution of phosphatase activity in the soil of the WLFZ. Phosphatase activities were significantly positively correlated with the contents of organic phosphorus forms but negatively correlated with the content of bioavailable phosphorus. A higher soil phosphatase activity and a lower content of bioavailable phosphorus were usually detected in soil samples taken at a higher altitude. In the early stage of flooding, phosphatase converted organic phosphorus into inorganic phosphorus at a relatively high rate, and the risk of phosphorus release to the overlying water body was also high. This study contributed to a comprehensive understanding of the geochemical cycle of soil phosphorus in the soil of the WLFZ.

Bioavailability of organic phosphorus in the water level fluctuation zone soil and the effects of ultraviolet irradiation on it in the Three Gorges Reservoir, China.

Ultraviolet (UV) irradiation is an abiotic pathway for the transformation of complex phosphorus (P) components into inorganic P in ecosystems. To explore the effect of UV irradiation on organic P (OP) bioavailability in the water level fluctuation zone (WLFZ) soil, we collected representative soil samples from WLFZ of the Pengxi River, a tributary of the TGR, China. We determined the contents of different forms of OP in the WLFZ soil through sequential extraction. The bioavailability of different forms of OP and the effect of UV light were characterised using a combination of enzymatic hydrolysis and UV irradiation. The OP contents of the different extracts (Po) were ranked as NaOH-Po > NaHCO3-Po > H2O-Po, whereas those of enzymatically hydrolysable organic P (EHP) were ranked as NaOH-EHP > NaHCO3-EHP > H2O-EHP. UV irradiation was found to improve OP bioavailability, as demonstrated by increased levels of UV-sensitive P (UV-P) and EHP in the extracts after irradiation. The total contents of bioavailable Po in extracts were 5.6-35.3% higher after UV irradiation than before irradiation. Thus, the effect of UV irradiation on the OP bioavailability and release activity cannot be neglected in TGR WLFZ soil.

Enhanced excess sludge hydrolysis and acidification in an activated sludge side-stream reactor process with single-stage sludge alkaline treatment: a pilot scale study.

A pilot-scale side-stream reactor process with single-stage sludge alkaline treatment was employed to systematically investigate characteristics of excess sludge hydrolysis and acidification with alkaline treatment and evaluate feasibility of recovering a carbon source (C-source) from excess sludge to enhance nutrient removal at ambient temperature. The resulting C-source and volatile fatty acid specific yields reached 349.19 mg chemical oxygen demand (COD)/g volatile suspended solids (VSS) d-1 and 121.3 mg COD/g VSS d-1, respectively, the process had excellent C-source recovery potential. The propionic-to-acetic acid ratio of the recovered C-source was 3.0 times that in the influent, which beneficially enhanced biological phosphorus removal. Large populations and varieties of hydrolytic acid producing bacteria cooperated with alkaline treatment to accelerate sludge hydrolysis and acidification. Physicochemical characteristics indicated that recovered C-source was derived primarily from extracellular polymeric substances hydrolysis rather than from cells disruption during alkaline treatment. This study showed that excess sludge as carbon source was successfully recycled by alkaline treatment in the process.

Investigation into cyclic utilization of carbon source in an advanced sludge reduction, inorganic solids separation, phosphorus recovery, and enhanced nutrient removal (SIPER) wastewater treatment process.

An advanced wastewater treatment process (SIPER) was developed to simultaneously reduce sludge production, prevent the accumulation of inorganic solids, recover phosphorus, and enhance nutrient removal. The ability to recover organic substance from excess sludge to enhance nutrient removal (especially nitrogen) and its performance as a C-source were evaluated in this study. The chemical oxygen demand/total nitrogen (COD/TN) and volatile fatty acids/total phosphorus (VFA/TP) ratios for the supernatant of the alkaline-treated sludge were 3.1 times and 2.7 times those of the influent, respectively. The biodegradability of the supernatant was much better than that of the influent. The system COD was increased by 91 mg/L, and nitrogen removal was improved by 19.6% (the removal rate for TN reached 80.4%) after the return of the alkaline-treated sludge as an internal C-source. The C-source recovered from the excess sludge was successfully used to enhance nitrogen removal. The internal C-source contributed 24.1% of the total C-source, and the cyclic utilization of the system C-source was achieved by recirculation of alkaline-treated sludge in the sludge reduction, inorganic solids separation, phosphorus recovery (SIPER) process.

[Effect of light and temperature on growth kinetics of Anabaena flosaquae under phosphorus limitation].

Phosphorus, light and temperature are the key environmental factors leading to algae growth. But the effects of interaction between light and temperature on the growth of Anabaena flosaquae under phosphorus limitation were not well documented in literature. Anabaena flosaquae was selected for the study and lab-scale experiment and simulation were carried out. The results showed that the optimal temperature of Anabaena flosaquae was 20 degrees C under phosphorus limitation when the light intensity was constant, and the optimal light intensity (illuminance) of Anabaena flosaquae was 3 000 lx under phosphorus limitation when the temperature was constant. Based on model fitting and parameter calibration, the optimal temperature and light intensity of Anabaena flosaquae were 21.03 degress C ± 1.55 degrees C and 2 675.12 lx ± 262.93 lx, respectively. These data were close to the actual water environmental condition at the end of spring. Results of this study will provide important foundation for prediction of Anabaena blooms.

Enhanced nitrogen and phosphorus removal by an advanced simultaneous sludge reduction, inorganic solids separation, phosphorus recovery, and enhanced nutrient removal wastewater treatment process.

An advanced wastewater treatment process (SIPER) was developed to simultaneously decrease sludge production, prevent the accumulation of inorganic solids, recover phosphorus, and enhance nutrient removal. The feasibility of simultaneous enhanced nutrient removal along with sludge reduction as well as the potential for enhanced nutrient removal via this process were further evaluated. The results showed that the denitrification potential of the supernatant of alkaline-treated sludge was higher than that of the influent. The system COD and VFA were increased by 23.0% and 68.2%, respectively, after the return of alkaline-treated sludge as an internal C-source, and the internal C-source contributed 24.1% of the total C-source. A total of 74.5% of phosphorus from wastewater was recovered as a usable chemical crystalline product. The nitrogen and phosphorus removal were improved by 19.6% and 23.6%, respectively, after incorporation of the side-stream system. Sludge minimization and excellent nutrient removal were successfully coupled in the SIPER process.

[Seasonal succession of phytoplankton function groups in the Xiaojiang (Pengxi) River backwater area, Three Gorges Reservoir].

Phytoplankton function classification came from the physiological characteristics and habitat adaption of specific phytoplankton species, matching the growth strategy of the species with the habitat template. The phytoplankton functional groups were classified based on the C-R-S growth strategy and its favored habitat. Phytoplankton function classification was applied in this study to the backwater area of Xiaojiang (Pengxi) River (XBA) of the Yangtze in the Three Gorges Reservoir. 26 functional groups were classified based on the phytoplankton species data from May, 2007 to April, 2009. J/F/H1/P/Lo/LM/B/Y/G/C was the major functional groups in the 2-year survey, while functional groups of MP/D/X1/X2/W1/W2 were also dominant and frequently detected. The succession traits among 5 sampling spots were generally the same. Succession series of the functional groups between the 2 years showed distinct. However, seasonal succession of functional groups based on the C-R-S strategy showed to have some in common: S/CS type dominated in the spring, while in the summer flood season a co-occurrence of S/CS type and R/CR type was evident. From autumn, the succession from S/CS type to R/CR type which dominated in winter was remarkable. In the February to March, the shift from R/CR type in winter to S/CS type in the early spring was completed in a relatilve short time span.

[Applicability study of CRI treating sewage in the Three-Gorges Reservoir Region].

The present domestic study on CRI mainly focuses on the cold and dry northern areas of water deficit. Aiming at the Three Gorges Reservoir Region featured with mild and wet climate and amethyst soil, We make a pilot study on the construction of CRI and its sewage disposal effects, and explores the applicability of CRI to the Three-Gorges Reservoir Region. The findings show that the infiltration coefficient of amethyst soil is small--0.1m(3) x (m2 x d)(-1) when converted into hydraulic loading rate, and the CRI can obtain preferable sewage disposal effects with the mentioned hydraulic loading rate and 1d:3d wet/dry (W/D) ratio. Climate and soil features are the main factors to W/D ratio and 1d:3d W/D ratio is applicable to the region, which indicates CRI is feasible in sewage disposal in the Three-Gorges Reservoir Region.