Research On Oxidative Inactivation And Removel Technology Of Limnoperna Fortunei In Long-distance Water Pipelines

Deterioration of water quality and biofouling problems on water pipelines caused by Limnoperna fortunei are new problems in southern water supply system. On the basis of the survey of Limnoperna fortunei, their biological characteristics were explored further. This paper studied the inactivation and removal effect and the dissolution of foot wire to Limnoperna fortunei by oxidants commonly used in water treatment, including potassium permanganate, sodium hypochlorite, chlorine dioxide, chloramines and hydrogen peroxide. And the role of inactivating Limnoperna fortunei by combined using of oxidants was investigated. In addition, the effects of combining oxidants and the water erosion were also discussed.The results show that the growth of Limnoperna fortunei was mainly four periods: trochophore, veliger, juvenile and adult. And there were two breeding season each year. Adult freshwater mussels usually adhere together through foot wires, and many impurities were attached on the surface, not falling. Low pH and DO could seriously affect the survival of Limnoperna fortunei.Five oxidants could all play a role of inactivating Limnoperna fortunei. Among them, chloramines, chlorine dioxide, potassium permanganate were better, and sodium hypochlorite was the second, but it could dissolve the byssuses. The effect of hydrogen peroxide was not very good. Because the freshwater mussel could close their shells in the harsh environment for self-protection, there was a most suitable concentration when each oxidant killed the mussels. By a large number of tests, the author concluded that the optimal dosage were as follows: Potassium permanganate 1.2～1.5mg/L, Chlorine dioxide 3～5mg/L, Sodium hypochlorite 4～5 mg/L, Hydrogen peroxide 4～5mg/L, Chloramine 1～3mg/L. Studies found that combined using the oxidants, not only could reduce each dosage, but combined effect was better.An appropriate increase in flow rate when using the oxidant could significantly improve the removal efficiency of freshwater mussel.At last, through comprehensive analysis and comparison,the writer proposed four optimum technical methods for practical application. These methods could reduce dosage and remove Limnoperna fortunei completely, preventing their secondary adhesion in the pipeline in order to reduce the damage to the pipeline.