Pilot-Scale Study On Polluted River-Net Raw Water With Combined Potable Water Treatment Process

As the degree of water pollution is aggravating and the water quality standards for fine drinking water are becoming stricter, the research and application of biological pretreatment technology, enhanced conventional process and advanced treatment process in water supply engineering have been increasingly emphasized. According to the characteristics of the polluted river-net water, a pilot-scale process combined with biological pretreatment technology, conventional treatment and advanced treatment process, which could treat5m3water every hour, were studied to discuss the removal efficiency of typical pollutants (such as ammonia nitrogen, organic matter, iron, manganese, etc) and problems encountered during the operation from the perspective of management.As the time sequence and the water quality characteristics, the test procedures (from Sep.2010to Aug.2011) was divided into7stages to discuss the mechanism and removal efficeiency of raw water pollutant characteristics of each procedure and processing unit respectively. Conclusion based on analyzing the operation data of the potable water treatment process are as follows.(1) Through synergism of the each unit of biological pretreatment, conventional treatment and ozone-biology activated carbon advanced treatment, the process was effective for the removal of ammonia-nitrogen, organic matter, iron and manganese contained in raw water of the contaminated river-net. In addition, as a barrier process, two filtration processes could respectively ensure the removal effieciency of coagulation-settlement process and ozone-biology activated carbon process to typical pollutants, which effectively ensured that the water quality of process effluent stably achieve national and local standards.(2) Ammonia nitrogen in the potable water was mainly removed by biological pretreatment technology, and the removal efficiency was greatly influenced by temperature. As a result, the change of water temperature made the removal efficiency was different in every processing unit of different test stage.(3) By studying CODMn, TOC and UV-254(characterization parameters of organic pollutants), it was found that the potable water treatment process could degrade most organic pollutant in the raw water efficiently and lower water temperature also had a certain influence on removal of organic pollutants. Coagulation/sedimentation unit and ozone-biological activated carbon unit had the highest removal efficiency.(4) The process could degrade iron ion and manganese ion in the raw water efficiently. Iron ion concentration was between0.06～0.09mg/L in the effluent, and manganese ion could not detected (which means below0.05mg/L).Conclusion and suggestion on operation management include:being restarted as the ammonia nitrogen in the water source varied from2.35mg/L to4.22mg/L and the water temperature from8.4℃to13.0℃, the removal efficiency of NH44+-N could achieve more than50%, which suggested that it should avoid operation pause to bio-contact oxidation tank at low temperature; there were mainly three reasons for periodic floating of floc in inclined-tube sedimentation tank, and low temperature further caused floating; it was proposed that effection of ozone on water quality indexes such as ammonia nitrogen, CODMn and UV-254could be used as indicator parameters to determine the effect of adding ozone; since the second sand filter did not work well when influent turbidity was below0.5NTU, relevant managing measures on the basis of micro expansion backwashing way was used to solve that problem. And the research also suggested the significance of micro expansion water backwashing method in water saving.