Yi Xing Yuan

The Disinfection Efficacy of Chlorine on Sulfate-Reducing Bacteria and Iron Bacteria in Water Supply Systems

Sulfate reducing bacteria (SRB) and iron reducing bacteria (IRB) that widely exist in water supply networks are the main microorganisms leading to metal corrosion in pipelines. Chlorine is widely used in drinking water supply systems. The concentration of chlorine with SRB declined rapidly after 10 mins and reached 0 mg/L finally whereas it decreased more slowly with IRB. If the concentration of chlorine is lower than 0.2mg/L, IRB cannot be sterilized. It indicates that at the end of water pipes where the concentration of chlorine is required to be 0.05mg/L, chlorine is not effective since the concentration is below the minimum requirement of removing IRB

Two-Step Optimization for the Design of Water Distribution Networks

Genetic algorithms (GA) are currently one of the state-of-the-art techniques for the optimization of engineering systems including water distribution networks design and rehabilitation. They are capable of finding near optimal cost solutions to these problems when certain cost and hydraulic parameters are given. Since many forms of GAs rely on random starting points, that is to say, the poor solutions, it has become an ongoing research topic how to efficiently provide good initial estimates of solution sets automatically. A novel method is proposed in this paper, known as two-step optimization, which uses a heuristic-based, Dijkstra arithmetic to optimize network topology to obtain the layout of main pipes. The first step provides a good pattern for subsequent GA runs. Two-step optimization is applied to a network.. The result shows that the proposed approach consistently outperforms the traditional design and the conventional non-heuristic-based GA approach in terms of convergence and calculation efficiency.

Microbial Community Dynamics and Nutrient Removal Performances in A2O System Using Ultrasonic-Disintegrated Sludge Supernatant as Internal Carbon Source

Ultrasonic-disintegrated sludge supernatant was supplemented into A2O system to assess the effects on nutrient removal performances and microbial community changes. In this experiment, easily biodegradable organics accounted for 50.6% of sludge supernatant, indicating its potential for biological nutrient removal. Simultaneously, during two-month operational period, the ammonia nitrogen (NH4+-N) and total phosphorus (TP) removal efficiencies improved to 92.3% and 93.5% from75.6% and 53.4%. Duo to the application of sludge supernatant, two microbial phyla, Proteobacteria and Actinobacteria, were primarily responsible for the biological nutrient removal. In particular, the sludge supernatant was selective for ammonia oxidizing bacteria Comamonas sp. and denitrifying phosphate accumulating organisms Sphingobacterium.

Microwave Pre-Treatment of Corn Straw and its Enzymatic Hydrolysis

To enhance enzymatic hydrolysis efficiency of the corn straw, a process microwave pretreatment of corn straw was optimized using response surface methodology (RSM). Estimated optimum parameters were as follows: water to corn straw ratio is 58:1, microwave power is 640w and processing time is 5 minutes. Under these conditions, a maximum enzyme hydrolysis ratio of corn straw (49.25%) after microwave pretreatment was reached.

Comparative Study on Two Ways of the Saturated SiC Regeneration with Mn2+ Adsorption

Abstract. The saturated SiC with the adsorption of Mn2+ was regenerated dynamically by water backwashing and NaOH, and the Mn2+ removing effect was compared by the two ways .The results showed that on the condition of Mn2+ concentration at 1.7～2.2 mg/L ,flowing speed at 7.8 m/h, the regeneration rate of saturated SiC was only 49.8% after the first regenerated by backwashing .As for the second time ,the rate was less than 15%,which had lost Mn2+ removing ability .But by NaOH, the regeneration rate was more than 100% after the fifth regenerated ,which was obviously better than that of backwashing .And further study was conducted on Mn2+ removing mechanism by SiC through SEM figures.

Comparative Study on the Mn2+ Removing Performance of Several Filters

The Mn2+ removing effect from groundwater by four kinds of filters——Zeolites ,Activated Carbon ,Manganese Sand and a new filter ANJ.SiC, were comparatively studied and analyzed respectively .The results show that, the Mn2+ removing effect of ANJ.SiC is significantly better than the other three .It is an ideal filter in Mn2+ removing ,which can be reused for a long time .These filters’ surface characteristics before and after saturation were compared through their SEM figures ,and the Mn2+ removing mechanism were further studied.

Flow Pattern and Pressure Drop in Highly Concentrated Slurries Transportation Pipelines

Flow pattern and pressure drop in highly concentrated slurries transportation pipelines were discussed. The particles are settling, and tend to settle down to the bottom of pipes due to the action of gravity force forming different flow patterns which can be indicated by particle concentration profile. Three distinct flow patterns can be observed for different particle size distribution at different velocities: fully stratified, partially stratified and fully suspended flow patterns. As for pressure drop, it is well known that pressure drops in pipeline flows of slurries are strongly dependent on the flow pattern developed in a pipeline. Furthermore, fine particles suspended in water make the water more viscous, and increase the friction. In case of coarse particles, having larger volume, they have the tendency to contact with the pipe wall and with the other coarse particles more times, which increase the friction of flow. Meanwhile, coarse particles are lifted by the pressure difference generated as they rotate in the liquid preventing the coarse particles from settling down which results in less friction. The mixture of particles of different sizes is helpful to reduce pressure drop in pipeline flow slurries. Narrow grading particles tend to have high frictional losses, while broad grading particles have low frictional losses at high concentrations.

Influence of Chlorination Conditions on Amount of Trihaloacetic Acids Formation

Experiment was made，in which Harbin reservoir water was taken as source water to observe the influence of chlorination conditions such as chlorine dosage，reaction time，pH value，organics concentration and varieties of disinfectant on the amount of trihaloacetic acids formation．Based on the experiment results，control measures were proposed for the formation of disinfection byproducts such as trihaloacetic acids through optimizat ion of disinfection．

Effect of Chlorination Conditions on Amount of THMs

Experiment was made，in which Harbin reservoir water was taken as source water to observe the influence of chlorination conditions such as chlorine dosage，reaction time，pH value，organics concentration and varieties of disinfectant on the amount of THMs formation．Based on the experiment results，control measures were proposed for the formation of disinfection byproducts such as THMs through optimization of disinfection．