Contamination Mechanism & Mathematical Simulation Of Dispersed-water Supply In Karst Areas Of Southwest China

This research studies the contamination feature, contamination mechanism, and water quality changing model in the course of storage and utilization aiming at the ubiquitous water contamination of dispersed water supply in Southwest China.There are three major dispersed-water supply modes in southwest karst area, they are water cistern, water tank and natural well, which source comes from rainwater, spring and subterranean river separately. Based on a great deal of investigation and factual engineering, the applicability of three modes is analyzed in the article by summarizing modes of dispersed-water supply in Southwest karst area. And then, the design thought, the design parameter and the adverting proceedings of each mode are discussed particularly.Through the investigation, monitoring and synthetic analysis of water quality of three primary dispersed water supply, it is considered that the water contamination comprises recharging water contamination and supplying water contamination, belonging to contamination over a plane and dot shaped contamination separately. There are three types of contamination, the main one is bio-contamination such as visible matter and invisible animalculum, the second is physical contamination such as high chromaticity and turbidity, and the last is chemical contamination such as mild POPs and the exceptional ion concentration resulted from refuse and excrement. There are three main contaminative approaches also. They are contamination during rainfall, contamination during runoff containing surface runoff and underground runoff, contamination during water leading, and contamination in water storage and utilization.Experimental results show most bacterium transport in water by attaching on suspend granules whenever before, in and after rain. The amount of free bacterium relates to not only the sort of bacteria but also hydrodynamic condition. The amount of free bacterium decreases with the increase in karst water velocity. Thus, the faster karst water velocity is the easier karst water is to be contaminated by free bacterium.The effect of storage time on water quality is obvious in different hydrodynamic conditions. Water flowing rotation can strongly restrain the growth of microorganism. While the motionless water can facilitate the growth, which is the main reason resulting the contamination in storage and utilization. Moreover, the effect of different sorts of material on water quality is obvious as well.The hydrodynamic mathematical model is constructed by analyzed the change law of water quality in water storage and utilization of dispersed-water supply. The parameters of the model have been defined and approved by experimental research. CODMn is selected as an indicator to estimate the contamination degree of dispersed-water supply and to control the water quality. And the model is proved by field test in Guilin. It shows the mathematical model can exactly simulate the contamination.The research results in the article open out the contamination feature and contamination mechanism which may be helpful to design the water treatment engineering.