Special attention has been paid to three types of processes, that is, source process, removal process and internal cycling. Through the summary of literatures, the mechanisms of typical cycling processes, such as sediment release and denitrification, were discussed. The comparison of contributions of different cycling processes was listed as well. Moreover, the main research approaches of experiment and modeling in this field were well summarized and compared, raising a general framework for the study of nutrients cycling in lakes. With the purpose of looking into the cycling of nutrients, different approaches should be combined together. For example, mechanism models and observation for the mass balance of nutrients, then the microcosmic experiments for the impact factors of cycling processes. It is an efficient way to explore the cycling of nutrients in lakes.

The spatial distribution of microbial biomass and activity in pilot-scale two-stage up-flow BAC filters were studied using lipid-P, plate colony count (HPC) and specific oxygen uptake rate (SOUR). Meanwhile, water qualities of the effluent were analyzed to evaluate the performance of BAC units. The results indicated that BAC filters could remove pollutants effectively, with the average removal efficiencies of 43.3 % for COD_Mn, 45.7% for UV₂₅₄, and 92.9 % for ammonia nitrogen, respectively. Furthermore, the removal of pollutants mainly occurred in of the top 400-mm GAC layer in the first-stage BAC filter. The content of lipid-P per unit volume media decreased from 7.49 to 4.86 nmol/cm³ and colony counts decreased from 2.26×10⁷ to 1.12×10⁷ CFU/cm³, indicating that the amount of biomass decreased along flow path. The SOUR per unit volume media was around 10^-2 mg / (cm³?h) and had a different pattern of spatial distribution. In addition, the water quality of the effluent of up-flow BAC filters was biologically safe.

Terminal restriction fragment length polymorphism (TRFLP) was used to investigate the change of bacterial and archaeal communities in leachate-contaminated aquifer in response to anaerobic phenanthrene biodegradation. Results show that a great change in bacterial community occurred with phenanthrene biodegradation. The ribotype and Shannon-Weiner index increase from 15 to 23, and 2.39 to 2.88 respectively. However, archaeal community only shows an insignificant change with phenanthrene biodegradation, and ribotype and Shannon-Weiner index vary slightly.

The bacterioplankton community structure in Wujin River was investigated by terminal restriction fragment length polymorphism (T-RFLP) technique in combination with 16S rRNA clone library analysis. The T-RFLP fingerprints analysis shows high diversity and low evenness among the bacterioplankton community. A 16S rRNA gene clone library was also constructed. The results based on Ribosomal Database Project Ⅱ show that there were relatively abundant bacterial species in Wujin River and the predominant bacteria belonged to the genera of Proteobacteria. The BLAST results indicate the proportion of clones with middle or high similarity to known sequences in GenBank was high, while many unknown microorganisms were also present. Moreover, the possible environmental links of known genera were also discussed.

The Daqing River is the most seriously polluted river in the Dianchi Lake watershed. A bypass demonstration work of step-feeding biological contact oxidation process ( SBCOP), with the treatment scale of 1000 m³day and the hydraulic retention time (HRT) of 4.75 hours, was built aroundthe river bank to purify the river water. During the winter dry seasonfrom Nov. 2007 to Mar. 2008, three sets of parameters of the demonstration work were operated by regulating step-feeding ratio and air-water rate according to the influent qualities and climatic conditions. The results show that the SBCOP demonstration work kept good removal efficiencies for COD and NH⁺₄ - N, and the averager emoval rates were 37.3% and 32.9% each. The step-feeding ratio of 1∶1∶1 was beneficial for removing COD and NH⁺₄ - N. The removal rate of NH⁺₄ - N decreased when the concentration of NH⁺₄ - N increased. The average removal rate of TN was as lowas 10.5%, owing to the negative impacts of low temperature, carbon source shortage, high DO level of the influent, and loose and porous bio film. Theremoval of TP depended on the deposition of sludge and adsorption of Spirogyra sp., and the average removal rate of TP was 13.7%. To avoid the minus removal rate of TP, sludge discharge and removing of dead Spirogyra sp. were needed. The air-water rate of 2 ∶1 was suitable when influent was Dianchi Lake water.

Bio-ceramic filter is one of the most widely used surface water treatment units in China. However, there is no simple and practical model to guide engineering design or aid the investigation of feasibility. According to the inner characteristics of fluid motion of bio-ceramic filter, plug-flow reactor model was applied to simulate organic removal of surface water. Moreover, the model was verified using the experimental data, based on the treatment of two surface waters with greatly different degree of organic pollution using pilot-scale bio-ceramic filter. The result indicates that plug-flow reactor model with first-order reaction could ideally simulate the COD_Mn removal using bio-ceramic filter.

Due to heavy pollution in Yellow River water, the finished water quality of most dinking water works taking Yellow River water as source water but using conventional treatment process, is not ideal. In this study the combined process was applied for the purification of Yellow River water, including biological pretreatment using moving bed biofilm reactor, conventional treatment unit, ozonation activated carbon advanced treatment unit. The results indicated each unit of the combined process could effectively reduce total organic carbon (TOC) in waters and the average of total removal rate was 42.2%. Moreover, the combined process performed well in reduction of UV₂₅₄, algae, assmilable organic carbon (AOC), biodegradable dissolved organic carbon (BDOC), and the trihalomethane precursors. The combined could effectively reduce mutagencity in waters and the moving bed biofilm reactor played a significant role, although the mutagencity in raw water was low.

The conventional treatment followed by Ozonation-BAC treatment was used for the treatment of polluted Yellow River water. The result indicated the conventional treatment unit performed well in reduction of COD _Mn, UV₂₅₄, chloroform precursors, algae and 2-methylisobornel, and Ozonation-BAC treatment unit could further effectively reduce these organic matters. The water quality of conventional treatment effluent could meet current Chinese drinking water criteria and thus subsequent advanced treatment was necessary. When the ozone dosage was 1mg/L the bromate ion in the finished water of the combined process was more than 10μg/L.

The effect of temperature on nitrification in a two-stage BAF system used for the treatment of ammonia-rich river water was investigated. The rapid increase of water temperature in spring induced a decrease of the ammonia removal efficiency. However, when the water temperatures were equal to or above 5℃, there was no sign of adverse effect of temperature rise on nitrification. The short-term temperature effects on the activity of nitrifying biofilm acclimated to very cold temperature (about 0.5℃) and to moderate temperature (15℃) were also investigated. The results indicated the former activity was seriously affected by the increase of temperature, but the latter activity was not thermo-labile. The cold-adapted response should be seriously considered to model the temperature effect on nitrification in a BAF system. Temperature effect on nitrification became more profound at lower temperature.

The changes of attached heterotrophic and nitrifying biomass in biological aerated filter (BAF) at low temperatures were investigated. At low water temperatures, even below 1℃, heterotrophic biomass could incre ase greatly, however, the increase was inhibited by the availability of biodegradable organic substrate. For nitrifying biomass in BAF the ammonia concentration was not inhibitory, but its increase was seriously hampered by low temperature. The inhibitory effect of low temperature on nitrifying biomass was more pronounced than that on heterotrophic biomass.