[Dissolved silicon, inorganic nitrogen and phosphorus in the stream water of two small watersheds in Three Gorges area].

By using the method of fixed-pointed monitoring in streams of two small watersheds in Three Gorges Reservoir Area, the contents of dissolved silicon (DSi), dissolved inorganic nitrogen (DIN) and dissolved phosphorus (DP) are analyzed. The seasonal variation, the content ratio of DSi, DIN and DP, and the potential environmental problems are also discussed. The results indicate that: (10 In the two rivers, DSi content ranges from 0.18 to 19.89 mg x L(-1), DIN from 0.39 to 6.85 mg x L(-1) , and both are higher in the dry period than in the wet period; (2) DP content is from 0.01 to 0.08 mg x L(-1), which shows no significant difference between the dry and wet period; (3) The contents of DSi and DIN in Quxi River are higher than in Baota River, which may relate with the local agricultural activities, land use/land cover, fertilizer and so on; (4) The contents of DSi, DIN and DP in two small watersheds are all higher than in Three Gorge Reservoir, and the content ratio of DSi, DIN, DP is about 138 : 81 : 1 in Baota River, and 500 : 350 : 1 in Quxi River, which suggests that more attention should be paid to a potential threat to water environment such as Water-bloom.

Determination and discussion hydraulic retention time in membrane bioreactor system.

Based on the microorganism kinetic model, the formula for computing hydraulic retention time in a membrane bioreactor system (MBR) is derived. With considering HRT as an evaluation index a combinational approach was used to discuss factors which have an effect on MBR. As a result, the influencing factors were listed in order from strength to weakness as: maximum specific removal rate K, saturation constant Ks, maintenance coefficient m, maximum specific growth rate mu m and observed yield coefficient Yobs. Moreover, the formula was simplified, whose parameters were experimentally determined in petrochemical wastewater treatment. The simplified formula is theta = 1.1(1/beta-1) (Ks + S)/KX0, for petrochemical wastewater treatment K and Ks equaled 0.185 and 154.2, respectively.