Study On The Treatment Of Micro-Polluted Water By The Micro-Sand Coagulation And Micro-Flocculation Filtration

Garnet and omphacite are the main components of eclogite.In the field of sewage treatment,garnet is widely used as high-density filter material(Heavy media filter material)with its large specific density,hardness,abrasive resistance,acid and alkali resistance,porosity and other characteristics.In the garnet sorting process,about 15 to 20%of micro-omphacite will be generated by magnetic separation.There is no proper utilization of this tailings slag.With the rapid growth of the global population,the intensification of domestic activities and the expansion of industrial and agricultural production,water pollution is one of the major challenges facing the global environment in the 21st century.This study uses omphacite as water treatment material.The physicochemical properties of omphacite were analyzed to provide basis for the follow-up study.Omphacite is used as an additive for accelerating precipitation in coagulation treatment,and micro-sand intensified coagulation process is used in the treatment of the micro-polluted water.Through single-factor experiments and multi-factor response surface analysis,we examined the effect of coagulants types(PAC,aluminum sulfate,and ferric chloride)and the dosing amount,pH,water temperature,particle size of micro-sand,and the dosage of micro-sand on condensing.Moreover,omphacite is uses as filter material,and micro-flocculation filtration process is used in the treatment of the micro-polluted water.This paper is studied on the effect of the factors to the filtration,which includes the filtration rate,particles of the omphacite,modified and double-layer filter(silica+omphacite).Effects of coagulation and filtration are represented by the removal rates of turbidity,UV254,and ammonia-nitrogen.The main results are as follows:(1)The mineral composition of the omphacite is very complex.The main mineral is the quartz,and the main content of SiO2 is 39.3%.When it is magnified 30000 times,there are some bumps on the surface and some particles stacked on the surface.It has strong acid and alkali resistance,and the specific gravity is 3.34.After leaching toxicity experiment,the content of heavy metals in leaching solution was lower than that of surface water ?standard limit.It can be considered as a safe material.(2)Omphacite is used as ballasting agent,and the micro-sand enhanced coagulation process is used in the treatment of the micro-polluted water.PAC coagulation effect is best,and the best dosage is 50 mg/L.At pH 6,the coagulation effect is best.The coagulation effect is also significantly affected by temperature,and ambient temperature(20?25?)is better than low temperature(0?5?).When the particle size is smaller than 60um,and its optimal dosage range is from 0.1 g/L to 0.3 g/L,the coagulation works best.We established a response surface model for response with the removal rate of turbidity,ammonia,and UV254 by the Design-expert software.The model is significant and the degree of fit is high,which can better analyze and predict the coagulation effect.The optimum conditions for the enhanced coagulation of omphacite micro-sand are:50 mg/L PAC,40-60 ?m micro-sand,0.27 g/L micro-sand dosage.The experimental results show that the application of micro-sand enhanced coagulation is shorter and more effective than conventional coagulation.(3)For micro-polluted water,we use omphacite as filter material for micro-flocculation filtration.The filtration is carried out by means of isobaric filtration,which keeps the water level in the filter column constant.The filtration cycle is long with high water level and big pressure.The removal rates of turbidity and organic matter(UV254)are in 98%and 45%in different water level filtration,respectively.The effect of ammonia nitrogen is better when the water level is lower.The larger particle size leading to longer filtration cycle,and the removal rates of turbidity and UV254 is 98%and 40%with different particle size.The removal effect of ammonia nitrogen is better when the size of the filter is small.When omphacite is treated by sulfuric acid,sodium hydroxide and hydrogen peroxide respectively,the removal effect of ammonia nitrogen was significantly elevated comparing to filter material treated by pure water.The filter cycle is longer with double-layer filtration compared to previous monolayer filtration.The filtering effect is best when the ratio of quartz and omphacite is 1:1.Compared with the previous monolayer filter material,the filtration cycle of double-layer filter material has been greatly improved,and the turbidity removal effect is more ideal.When the organic and ammonia nitrogen removal best,quartz sand and omphacite ratio is 1:1.Compared with the conventional quartz sand filtration,the removal rate of turbidity and ammonia nitrogen increased by 15%and 18%according to our omphacite filtration,but there was no significant difference in organic removal effect.