Modification of Grey Water Treatment Using Combination of Cascade Aeration and Biofiltration

A combination of cascade aeration and biofiltration systems is one of the available ecological treatments to reduce the concentration of pollutants in grey water and resolve the problem of acute water crisis supply in Iraq. An experimental constructed grey water treatment system has been installed at AI-Mustansiriya University, College of Engineering during the period from January to December 2012. The performance of the treatment schemes has been evaluated by monitoring the quality of the raw grey water and effluent on these samples which are： pH, COD （chemical oxygen demand）, TSS （total suspended solids）, TDS （total dissolved solids）, PO43 （phosphates）, NO32 （nitrates）, NO （nitrites）, oils ＆ grease, NH3-N （ammonia-nitrogen） and some anions and cations. The average removal rate of COD was more than 60% that of NH3-N, NO3-N, NO2-N, TDS and TSS that were 55%-89%, 59%-74%, 79%-98%, 17%-52% and 51%-87%, respectively. Also the results indicate that the removal efficiency of ions concentrations such as Ca2＋, Mg2＋, Na＋, K＋ were 78%-96%, 73%-97%, 14%-47% and 44%-64%, respectively, while for cations such as SO42, Cl and PO43-, the removal efficiencies were 33%-79%, 27%-61% and 81%-99%, respectively. Finally oils ＆ grease was 79%-88%.

Optimizing the aeration performance of a perforated pooled circular stepped cascade aerator using hybrid ANN-PSO technique

Artificial aeration system for aquaculture ponds becomes essential to meet the oxygen requirement posed by the aquatic species.The performance of an aerator is generally mea-sured in terms of standard aeration efficiency(SAE),which is significantly affected by the different geometric and dynamic parameters of the aerator.Therefore,to enhance the aer-ation performance of an aerator,these parameters need to be optimized.In the present study,a perforated pooled circular stepped cascade(PPCSC)aerator was developed,and the geometric and dynamic parameters of the developed aerator were optimized using the hybrid ANN-PSO technique for maximizing its aeration efficiency.The geometric parameters include consecutive step width ratio(W_(i-1)/W_(i))and the perforation diameter to the bottom-most radius ratio(d/R_(b)),whereas the dynamic parameter includes the water flow rate(Q).A 3–6-1 ANN model coupled with particle swarm optimization(PSO)approach was used to obtain the optimum values of geometric and dynamic parameters correspond-ing to the maximum SAE.The optimal values of the consecutive step width ratio(W_(i-1)/W_(i)),the perforation diameter to the bottom-most radius ratio(d/R_(b)),and the water flow rate(Q)for maximizing the SAE were found to be 1.15,0.0027 and 0.0167 m^(3)/s,respectively.The cross-validation results showed a deviation of 3.07%between the predicted and experimen-tal SAE values,thus confirming the adequacy of the proposed hybrid ANN-PSO technique.

自由流线问题有限元分析

在文 ［７］ ［８］ ［９］ 的基础上，研究自由流线问题有限元解的通用计算方法。将各结点的坐标，代替流函数值，定义为有限元方程的广义坐标，使自由流线理论中对应于正、逆问题以及空腔流动问题的有限元方程有相同形式。用 Ｇａｌｅｒｋｉｎ 方法构成关于流速的变分方程，解决了弱解求导的困难。给出二种类型的空腔流动及机翼逆问题三个典型算例，表明方法有较好的适应能力。

基于广义预测控制的除氧器水位快速控制方法仿真

凝结水节流技术利用低压加热器系统蓄热辅助响应一次调频、变负荷的功率需求,提高汽轮机稳态高调门开度,降低节流损失,提高机组运行经济性。该项技术应用时,受常规PID(proportional, integral and differential)除氧器水位控制响应相对较慢的约束,凝结水节流动作幅度较小,辅助负荷响应作用难以充分发挥。针对该问题,通过深入分析广义预测控制算法,提出一种基于广义预测控制的除氧器水位快速控制方法,用于在凝结水节流响应过程中出现过高或过低水位时,快速恢复水位,保障凝结水节流系统运行安全。仿真试验表明,该方法能够快速平抑除氧器水位扰动,在确保凝结水节流系统安全运行的前提下提高凝结水节流动作幅度。该方法可作为凝结水节流技术应用时的一种除氧器水位快速控制方法。