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Lakes in cold zones have common characteristics of long frozen periods and fragile water ecosystems. More and more lakes in cold zones have been experiencing water quality deterioration due to eutrophication with climate change and human activities. Lake Hulun is located in the cold zone of northern China, in which Cyanobacterial blooms frequently occur. The excessive nutrient input with inflowing river water and the change in lake hydrodynamic condition might be the main factors affecting this. To obtain a better understanding of the effects, the input loads of nutrients from the inflowing rivers were analyzed. A field test of freezing concentration combined with microbial activity regulation was carried out at a river–lake confluence. The results showed the following: (1) Lake Hulun receives a large amount of nitrogen and phosphorus pollutants from river runoff every year, and the water quality of these river is inferior Grade V, which greatly increases the difficulty in ecological purification of cold zone lakes. (2) The microbial activity control technology has a high purification rate for water during the unfrozen period. The order of purification rates for each hydrochemical index was TP > TN > COD > NH4+-N, and the purification rates of TN and COD were between 35% and 36%. Compared with the water before purification, the water quality grade improved from Grade V to Grade III. (3) The composite technology of freezing concentration–microbial activity regulation has a general water purification rate during the frozen period. Under the low-temperature condition, the TN and COD nutrient fluxes in the water were reduced by 9.38% and 9.36%, respectively. After purification, the water quality grade of the ice body was above Grade II, and the water under the ice layer was above Grade IV, which was one grade higher than the water quality grade of the original lake water. This water treatment and purification process is a green, low-energy consumption, and low-cost technology. This study can provide reference for the integration and demonstration of lake water ecological governance and water resources security technology in cold and arid regions. It is beneficial to the sustainable development of the lake. [ABSTRACT FROM AUTHOR]

Lycium chinense juice is rich in a variety of nutrients and ingredients for health, and concentrated juice is its important circulation type. In order to explore the effect of concentration methods on the quality characteristics of Lycium chinense juice, the heating concentration (HC), vacuum concentration (VC), secondary freezing concentration (SFC), heating-assisted primary freezing concentration (HAPFC), and vacuum-assisted primary freezing concentration (VAPFC) were applied in the present work, and the color, reducing sugar, sugar fraction, organic acid fraction, total phenols, total flavonoids, carotenoids, DPPH and FRAP of Lycium chinense juice before and after concentrated were measured. The results showed that VC treatment showed better color protection than the other treatment groups, as well as retained higher reducing sugar in concentrated juice, and less effect on malic acid and tartaric acid degradation. The total phenols and total flavonoids of Lycium chinense juice concentrated by VC were higher 8.76%~21.40% and 5.41%~13.77% than other groups, respectively. The DPPH free radical scavenging capacity and ferric ion reducing capacity of Lycium chinense juice concentrated by VC owed higher 6.98%~29.77% and 5.97%~26.76% when compared with the other groups, beside lower carotenoids degradation. Therefore, VC showed the best protection effects on the quality characteristics of Lycium chinense juice during concentration and it is a suitable way to concentrate Lycium chinense juice.

• Energy efficiency in 6 % to 13 % concentration and 4 m3/h to 7 m3/h flow rate was studied. • The high-volumetric flow rate had the minor influence on the ice formation stage. • Energy consumption was primarily dependent on separation effect. • Increase in segregation efficiency corresponded to an increase in COP. • Effective utilization heat rate was related to the proportion of latent heat. Freezing concentration has a good energy efficiency during regeneration operation. Under the variational regeneration conditions, the icing and melting operation has direct influence on the overall system performance. In this study, a solution regenerator unit using freezing concentration with a heat pump system was built to test the heating performance and energy efficiency under varied concentrations and volumetric flow rates. Results showed that the energy efficiency was inversely proportional to the latent heat ratio. With the growth of ice layers, the influence of volumetric flow rates on heat capacity decreased. At the ice thickness was 0.6 cm, the heat capacity was consistent at all volumetric flow rates. Under the melting process, the effect of melting ratio on energy efficiency under the low concentration was more significant. The average effective utilization heat rate which concentration was 6 %, 8 %, 10 % and 13 % was 0.63, 0.67, 0.70, and 0.74, respectively. The relationship between the effective heat utilization and the distribution of the ice layer was studied. Results showed that the energy efficiency performance was directly proportional to average percentage slopes. [ABSTRACT FROM AUTHOR]