| Due to low vegetation coverage in some parts of northwestern China,the turbidity of river water sources suddenly rises during spring snowmelt and summer rainstorms;Many water sources,especially lake water,are characterized by low temperature and low turbidity owing to climate impact in winter;In addition,some groundwater sources still have problems with excessive manganese.These water quality problems make the treatment of drinking water more difficult,especially for rural water supply with relatively low technical and management levels,the conventional treatment process cannot effectively guarantee the safety of water supply.This paper takes three kinds of refractory water sources in the northwestern region as the research object,includes high turbidity water,low-temperature and low-turbidity water,high manganese groundwater,and we proposed targeted processes: pellet flocculation blanket process,synergistic circulate pellet flocculation blanket process,manganese removal by active filter media catalytic oxidationrespectively,and optimize technical conditions for the purpose of improving the applicability of the process in rural areas in the northwest.The main research contents and conclusions are as follows:(1)Simulating high turbidity runoff water with turbidity of 3000-9000 NTU,which is prepared from dry mud taken from the Xinachuan water source Area,Qinghai Province,and optimize pellet flocculation blanket process operating parameters.Determination of Polyaluminum chloride(PAC)and anionic polyacrylamide(APAM)as preferred coagulants by beaker experiments;The optimal operating parameters of the system were determined under pilot scale experiment: PAC dosage 30 mg/L,APAMdosage 1 mg/L,tubular flocculator length 30 m,forced agitation intensity 12 r/min,safe rising flow rate 50 cm/min;the system can be quickly started up at an upward flow rate of no more than 30 cm/min after the system is shut down.(2)Using sludge and micro-sand as flocculating carrier to analyze the influencing factors of low-temperature and low-turbidity by synergistic circulate pellet flocculation blanket process respectively,determine the primary and secondary order of each influencing factor and optimize the parameters.The dosage of PAC and the dosage of APAM are the main influencing factors of sludge carrier system and micro-sand carrier system respectively,the forced stirring intensity has little effect on the treatment effect of the system.The highest ascending flow rates for the sludge carrier system and the micro-sand carrier system can reach 90 cm/min and 120 cm/minrespectively.The test results show that no acrylamide residual monomer was detected in the continuous run of the system for a long time.(3)Exploring the effect of influent dissolved oxygen(DO)on the preparation of catalytic oxidation active filter media,and selecting a groundwater manganese exceeding the standard village in the northwest for technical application.Increasing the influent DO by falling water aeration can reduce the filter start-up time from 36 days to14 days and improve the manganese removal capacity of the active filter media.The active filter media prepared under submerged anaerobic environment is more suitable for the natural anoxic environment of groundwater,and can remove 4 mg/L manganese at 6 m/h filtration rate.The distinction in morphology of the active filter media prepared with different influent DO conditions is not obvious,and the variant capability may be due to the divergence in surface manganese oxide structure and composition.Small active filter mediacatalytic oxidation water purification equipment has excellent applicability in a groundwater manganese exceeding standard village in rural areas of Northwest China,when the influent manganese concentration is 4.5 mg/L,the maximum filtration rate can reach 4 m/h.The manganese removal activity of the active filter media did not decrease when the equipment was restarted after a certain period of time(30 day). |
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