In order to study the relationship between nutrient pollutants and suspended sediments (SS) in the upper reaches of the Yangtze River and two tributaries, water samples were collected from at the Zhutuo, Cuntang, Beibei, Wulong, Qingxichang, Wanxian, and Fengjie cross-sections. In the laboratory, the SS concentration and the concentration of SS whose particle size was smaller than 0.02 mm were measured. The phosphorus (P), nitrogen (N), and permanganate index (COD Mn ) concentrations in the natural water sample, the settled water sample, and two types of filtered water samples obtained through filter membranes with pore sizes of 0.02 mm and 0.45 mm were monitored synchronously. The results show that there are strong relationships between the P and COD Mn concentrations and the SS concentration. P mainly exists in particulate form, while N mainly exists in dissolved form. SS whose particle size is smaller than 0.02 mm accounts for a high proportion of sediments in the Yangtze River and has a strong effect on water quality. At the seven cross-sections, the amounts of P, N, and COD Mn in particulate form in the wet season are higher than in the dry season and the adsorption amounts of P, N, and COD Mn per unit mass of sediment are higher in the dry season than in the wet season.

By researching the influence of sludge age (SRT) on phosphorous removal and sludge characteristics in the HA-A/A-MCO (hydrolysis-acidification-anaerobic/anoxic-multistep continuous oxic tank) process, which has the effect of simultaneous phosphorous and nitrogen removal and sludge reduction, it is found that extended SRT is helpful for improving the ability of anaerobic phosphorous release and chemical recovery of phosphate, but the hosphorous removal efficiency is not affected. Extended SRT causes the system to have even more active sludge; it can also lead to the system having a powerful ability of biochemical reaction by using superiority of concentration. Meanwhile, extended SRT can still reduce sludge yield. Extended SRT cannot make soluble metabolic product (SMP) accumulate in the reactor, so that the pollutant removal power is reduced; it also cannot affect the activity of the sludge. However, extended SRT is able to make the coagulation of the sludge hard, and cause the sludge volume index value increase, but cannot cause sludge bulking.

An advanced sludge reduction process, i.e. sludge reduction and phosphorous removal process, was developed. The results show that excellent sludge reduction and biological phosphorous removal can be achieved perfectly in this system. When chemical oxygen demand /)(COD) is 332 -420 mg/L, concentration of ammonia p(NH3-N) is 30 -40 mg/L and concentration of total phosphorous p(TP) is 6.0 -9.0 mg/L in influent, the system still ensures p(COD)~23 mg/L, p(NH:N)~3.2 mg/L and p(TP)~0.72 mg/L in effluent. Besides, when the concentration of dissolved oxygen p(DO) is around 1.0 mg/L, sludge production is less than 0. 140 g with the consumption of 1 g COD, and the phosphorous removal exceeds 91%. Also, 48.4% of total nitrogen is removed by simultaneous nitrification and denitrification.

In order to explore methods of improving phosphorous and nitrogen removal in sludge reduction technologies, an advanced process combining sludge reduction and phosphorous and nitrogen removal was developed, for short, HA-A/A-MCO Process (Hydrolysis-Acidogenosis -Anaerobic/Anoxic-Multistep Continuous Oxic tank). Under the condition of this process achieving favorable effect of phosphorous and nitrogen removal and sludge reduction, test results of the process treating campus wastewater showed that when influent COD was 316-407mg/L, effluent COD was lower than 18mg/L, and COD removal rate exceeded 96%. When return ratio of anaerobic P-release sludge entering into hydrolysis-acidification tank was about 2% of influent flow, most anaerobic P-release sludge was translated into organic matter and it mainly contained VFA(about 275mg/L), which was 4.74 times as much as that(58mg/L) in original sewage. Supernatant which was rich in VFA from hydrolysis-acidification tank entered into subsequent A2/O cells, which could provide affluent carbon source for phosphorous and nitrogen removal.

When organic load of mixed liquid is up to a certain value, organic matter content is not the restrictive factor of phosphorus release any more. Optimum organic load for phosphorous anaerobic release in HA-A/A-MCO process is 0.141gCOD/gMLSS.d. Sufficient phosphorus release in anaerobic phase is the premise that high efficiency phosphorus absorption can be obtained in anaerobic phase. The maximum of releasable phosphorus sludge per unit weight (Pm/M) in HA-A/A-MCO process is 5.7mgP/gMLSS