Studies On Excessive Propagation And Inactivation Experiment Of Small Aquatic Animals In Surface Water Resources

Due to the deterioration of ecology, surface water in China has been badly polluted in recent years. Then tolerance species such as Limnodrilus, Water flea and Chironomid larvae are propagating out of control in the polluted surface water. While this kind of water is used as sources for the drinking water, these small animals can get into the water supply systems and lead to severe pollution.It was found that the dominant organisms in the surface water resources in Xi'an were Tubifex, Cladocera and Chironomid larvae. Through artificial breeding in the lab, habits and features of these worms were found. In favorable condition, Tubifex needs 52~69d for fully development, which involves three phases. The development in cocoon needs 10~14d, and the youth phase lasts 37~45d, and more 5-10d was needed for the development in maturity phase. The growth of Cladocera needs at least 6d. A generation of Chironomid lasts at least 30d in the lab, and the larva stage covers about 25d. Cladocera could adapt quite well to the change of temperature, dissolved oxygen as well as pH value. Tubifex can endure low content of dissolved oxygen, but it couldn't survive in the weak acidity and weak basicity solutions.A comparision was made on the inactivation efficiency of Tubifex killed by five oxidants. The sequence of killing rate for different chemical agents wasxhlorine dioxide≈liquid chlorine>ozone>potassium permanganate>hydrogen peroxide. The extension of contact time contributes to the exaltation of oxidants' effect to the worms, and the inactivation efficiency of potassium permanganate was intensively affected by contact time. The sequence of adaptive capacity to PH value from high to low respectively was chlorine dioxide, liquid chlorine, potassium permanganate. At about 25℃, chlorine dioxide reached its optimal inactivation, while the optimal temperatureof inactivation for liquid chlorine and potassium permanganate were 26 °C and 30 °C respectively. Only when the CT value reached ISOmgTnin'L"1, could chlorine dioxide kill all the Tubifex thoroughly. Chlorine dioxide, liquid chlorine and potassium permanganate could adapt to the change of organic content in water to some extent. Both chlorine dioxide and liquid chlorine could kill the young Tubifex well. Different oxidants have different inactivation mechanisms.A comparision was made on the inactivation efficiency of Cladocera killed by five oxidants. The sequence of the chemical agents' killing rate on Cladocera from high to low respectively was ozone, chlorine dioxide, liquid chlorine, potassium permanganate and hydrogen peroxide. Except hydrogen peroxide, the extension of contact time could contribute to the exaltation of oxidants' killing effect to the animals. It was showed by our experiment that pH value exerted less influence on the inactivation of chlorine dioxide than on the inactivation of liquid chlorine and potassium permanganate. As a whole, with the rising of concentration of organic matters in the water, the inactivation efficiency of Cladocera killed by any kind of oxidant would go down, because organic matters comsumed part of the oxidant. The killing process of ozone to Cladocera follows a first-order mode.