| The surface drinking water resource in rural districts of China has been pollutedin many ways, especially in some poor districts. Due to the limit of economy,technology and management level, there is some critical risk for the drinking watersafety in rural districts, especially for some scattered drinking water facilities Drinkingwater treatment technology on micro-polluted water resources was studied in thisarticle, whose key technology was immersed ultrafiltration(UF) membrane with thepretreatments of coagulation, powder activated carbon (PAC) adsorption and biologicalpretreatment.The removal rate of organic matter in the water by solo UF was lower than20%.Enhanced coagulation as pretreatment could increase the removal rate of humic acid inthe water by hybrid process of UF efficiently, and10mg/L dosage of coagulant couldmake the removal rate of UV254and DOC up to85.7%and69.0%, respectively.Coagulation and PAC adsorption could improve the removal rate of pollutant led bysewage in the water resource by hybrid process efficiently. It is suitable, economicaland effective for transverse flow and water-dropping aerated biological filter to beadopted as pretreatment of immersed UF, biological filter could achieve high ammonianitrogen removal(>90%), decrease the organic matter load of UF, and increase thebiological stability of pipeline through removing AOC and BDOC. The effectivenessof water-dropping aeration was fine and the hydraulic retention time (HRT) should belonger than1hour. The relationship between ammonia nitrogen removal velocity andwater temperature followed the equation asr=r (T-20)20.The turbidity of the mixed liquid in the reactor of immersed UF could reach20,000NTU through enhanced washing, which could offer reference for short-processdrinking water treatment technology of UF membrane being applied more widely. Therelationships between the normalized permeate flux (J/J0) and filtration time could befitted to the simple equation of J/J0a exp(kt), and coefficient k in the equationand DOC of humic acid in influent could be fitted to the square equation. Coagulationand PAC adsorption could remove hydrophobic matter in the water which mostly leadsto membrane fouling, and flocs caused by coagulation could make filter cake layer on the membrane surface loose, PAC could act as skeleton of the cake layer, then, themembrane flux would decline slower during the process. Continuous dosing coagulantand batch dosing PAC had better results on increasing the membrane flux. During theapplication of the hybrid process of UF, coagulation reaction tank was not necessary.Shorter backflushing period and greater aeration intensity could increase the membraneflux; chemical washing and in-line chemical washing in low alkali solution could makethe membrane flux revive efficiently.With the co-existence of particles and NOM, NOM will adsorb onto the surface ofthe particles, make the particles more stable, decrease the agglomerate size and smoothout the surface heterogeneity of kaolinite. Porous polyhedral structure would not beformed on the membrane surface easily, which was an additive effect on membraneflux during solo UF. Coagulation could eliminate the additive effect led by NOM andparticles and make the membrane flux decline slower with the co-existence of particleand NOM, than with the existence of NOM alone, because the particles improved thestructure of filter cake layer.The process and equipment in the demonstration project could work stably in along period. In this demonstration project, the water production ratio was93.8%, andthe ratio between air and water was0.31:1. The unit cost of water production was0.36RMB yuan/m~3, including0.02RMB yuan/m~3of power fee, and0.01RMB yuan/m~3of medicament expense. In the unit cost of water production, depreciation cost ofmembrane and other equipments (0.19RMB yuan/m~3) and payment for the workerswere the main cost (0.07RMB yuan/m~3).
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