Study On The Bio-slow Sand Filters Aided With Non-woven Synthetic Fabric For Rural Micro-polluted Source

Since the start of the rural drinking water safety construction project in 2005,it has solved the problem of drinking water suffering and instability of more than 400 million rural population,and has made remarkable achievements.However,in recent years,with the accelerated development of China's rural economy,people's living standards improved significantly.At the same time,the rural ecological environment has been greatly affected,especially,in accounting for the hilly areas,where the terrain is complex and the farmers live scattered.Water supply guarantee rate and water quality pass rate are low.Drinking water safety is still a big hidden danger.Bio-slow sand filtration has a good removal effect on bacteria and viruses,and is simple in technology and operation and low cost treatment technology,and is suitable for small centralized and decentralized water supply projects in rural areas.However the filtration rate of Bio-slow sand filtration is low.After a period of time,there is need to clear the upper filter material.Cost of mechanical removal investment is high and artificial technology is not easy to master.Non-woven synthetic fabric?NWF?aided bio-slow sand filter changes removal mode.In this study,performance of Non-woven synthetic fabric aided bio-slow sand filter for rural micro-polluted source was evaluated in a laboratory scale setup.The results revealed that:NWF captured most of the particles.When the thickness is 1.4².4cm and the turbidity of raw water is 10 NTU,the removal of turbidity is 50%⁶3% in NWF.With the increase of thickness of NWF,the performance of filtration was better.NWF significantly protected the sand beds from particle deposition,dropped the rate of head loss increase and lengthened the filter run time.When the thickness of NWF is 24 mm,the protection time is 17 days.When the thickness of NWF is 19.2mm,the protection time is 14 days.When the thickness of NWF is 14.4mm,the protection time is 10 days.When the thickness is 1.4².4cm,the thickness of NWF is increaser,the protection time is longer.When the turbidity of water was about 10 NTU,the turbidity of filtered water was improved by less than 1NTU,which reached the national hygienic standard for drinking water.NWF is a fibrous network structure,which provides a good habitat for microbial growth.When the temperature was 24.7²6.3 and filtration rate was 0.2m/h,the ammonia nitrogen removal rate 60% taken as a parameter indicating whether the biomembrane was successful,the time of the natural biomembrane was 20 days.Then,when ammonia nitrogen concentration of the raw water is 0.98¹.13mg/L,and COD_Mn concentration is 6.5⁷.9mg/L of the raw water,and filtration rate was 0.2m/h,the elimination rate for ammonia nitrogen was 67.6% and the elimination rate for COD_Mn was 33.6%.The concentration of ammonia nitrogen and COD_Mn reached the national hygienic standard for drinking water.When the thickness is 1.4².4cm,the thickness of NWF is increaser,the turbidity removal effect is better.The thickness of non-woven fabric has not significant effect on the removal efficiency of ammonia nitrogen and COD_Mn.Microbial membrane mainly grows on the surface of non-woven fabrics,and ammonia and COD_Mn removal depends on biological effects.emperature is one of the important factors influencing the performance of SSF.When the temperature was 20²6?,the elimination rate for ammonia nitrogen and COD_Mn were above 25% and 60%,respectively.When the temperature was 11.4?,the elimination rate for ammonia nitrogen and COD_Mn dropped to 21.9% and 12.2%.The filtration rate has important effects on the performance of SSF.When the filtration rate was above 0.4m/h,the turbidity cannot meet drinking water requirements and the elimination rate for ammonia nitrogen and COD_Mn declined rapidly.The filtration rate of biological slow filter was increased to 1.0m/h.When the filtration rate is greater than 0.4m/h,the turbidity of water starts to increase.When the filtration rate is1.0m/h,the turbidity of effluent is 4.7NTU,which can not meet the requirement of drinking water.With the increase of filtration rate,the removal efficiency of ammonia nitrogen and COD_Mn decreased,and the removal efficiency decreased obviously when the filtration rate was over 0.4m/h...