The relationship between the automatic control method and the stability of the open canal is studied by means of numerical simulation of unsteady flow in an open canal under different methods of control. It is found the Proportional-Proportional plus Reset （P＋PR） control is more reliable than the Linear Quadratic Regulator （LQR） control. Moreover, for the P＋PR control, the hydraulic response of the constant volume method of operation is better than that of the constant downstream depth method in the type of centrally controlled canal. Therefore, an appropriate flow change rate should be chosen instead of shortening the pool length to reach an acceptable drawdown rate. For the canal with a bottom width of 40 m, side slope of 3, Manning n of 0.015, bottom slope of 0.000 04, and design flow of 600 m3/s, the pool length of more than 30 km can provide acceptable drawdown rates of 0.2 m/h when a proper flow change rate is chosen.
As the bioelectrochemical system, the microbial fuel cell （MFC） and the microbial electrolysis cell （MEC） were developed to selectively recover Cu^2＋ and Ni^2＋ ions from wastewater. The wastewater was treated in the cathode chambers of the system, in which Cu^2＋ and Ni^2＋ ions were removed by using the MFC and the MEC, respectively. At an initial Cu^2＋ concentration of 500 mg· L^-1, removal efficiencies of Cu^2＋ increased from 97.0%±1.8% to 99.0%±0.3% with the initial Ni^2＋ concentrations from 250 to 1000 mg· L^-1, and maximum power densities increased from 3.1±0.5 to 5.4±0.6W.m-3. The Ni^2＋ removal mass in the MEC increased from 6.84-0.2 to 20.54-1.5 mg with the increase of Ni^2＋ concentrations. At an initial Ni^2＋ concentration of 500 mg· L^-1, Cu^2＋ removal etticiencies decreased from 99.1%±0.3% to 74.2%±3.8% with the initial Cu^2＋ concentrations from 250 to 1000 mg -L1, and maximum power densities increased from 3.0±0.1 to 6.3±1.2W.m^-3. Subsequently, the Ni^2＋ removal efficiencies decreased from 96.9%-4-3.1% to 73.3%4-5.4%. The results clearly demonstrated the feasibility of selective recovery of Cu2~ and Ni2~ from the wastewater using the bioelectrochemical system.
Haiping LUO Bangyu QIN Guangli LIU Renduo ZHANG Yabo TANG Yanping HOU
