Study About The Influences On Degradation Processes Of Ammonia Nitrogen And The Water Quality Index By Sediment Concentrations In Lanzhou Reach Of Yellow River

The suspended sediment in the river has small particle diameter and great specific surface area. A great deal of clay minerals and organic or inorganic colloids are absorbed on the surface of sediment. Some complicated interfacial effects will take place on the surface of sediment when the pollutants and sediment come into contact with each other in water. As a result, the physical, chemical characteristics of water body are different from the one without sediment. On the one hand, the pollutants can be degraded by the adsorption of active materials on the surface of sediment. On the other hand, as the carrier of pollutants, it will contaminate the water environment again.Based on the reviewing the previous research works, with the research object of the sediment in Lanzhou reach of Yellow River, the degradation process of ammonia nitrogen under different characteristics of sediment and different environmental factors are studied by laboratory experiments in this paper. Furthermore, the influences on water quality index by sediment concentrations are studied.The experiments contents and research results are as followed:(1) The degradation processes of ammonia nitrogen under different sediment concentrations and different particle size are studied, and the results showed that under the laboratory conditions, the rate of degradation would increase with the growth of sediment concentrations; and when the sediment concentrations is constant, the rate of degradation would increase with the decrease of particle size; removing the active materials also promoted the degradation rate of ammonia nitrogen.(2)The degradation data of ammonia nitrogen under different sediment concentrations are fitted by reaction kinetics, and the results showed that when the sediment concentrations bellowed 0.5g/L, the degradation process fitted the zero order reaction, and the logarithm of ammonia nitrogen concentration had obvious linear relationship with time which fitted the one-order reaction kinetics.(3) The influence factors on degradation of ammonia nitrogen were studied by changing temperature, pH, agitation conditions and initial ammonia nitrogen concentrations. The results showed that, under the experiment conditions, the highest rate of degradation occurred under temperature of 28°C,pH=7, fully mixing conditions and lower the initial concentration of ammonia nitrogen. The principal factor influenced the degradation of ammonia nitrogen is pH which determined by Orthogonal experiment.(4)The testing values of ammonia nitrogen, COD_Mn, BOD₅ under different sediment concentrations were studied; the results indicated that with pre-treatment of acid, the values of ammonia nitrogen, COD_Mn, BOD₅ in muddy water is higher than branch water, they increased with the increase of the sediment concentration, and the testing data in acid water are higher than the water without pre-treatment.