Removal Of High Iron, Manganese And Ammonia Nitrogen From Low Temperature Groundwater By Bio-filter

The Songhua River Basin in northeastern China is the concentrated area of groundwater containing iron?Fe?and manganese?Mn?.It has been discovered that the iron content of groundwater in the area is up to 60 mg/L,and the maximum manganese content is up to 5 mg/L.The regional groundwater water temperature that affected by cold continental climate only 5-10?all the year round,and the groundwater temperature in some areas is as low as 3-5?.What's more,the ammonia nitrogen?NH₄⁺-N?pollution in the groundwater in the region has become increasingly serious and has increased year by year due to the influence of industrial and agricultural development.Based on the above reasons,the water quality of the water plants in many areas of the Songhua River Basin has declined,and the manganese and ammonia nitrogen produced by the A and B water plant have exceeded the standards.This indicated that the traditional chemical contact oxidation technology failed to removal of iron,manganese and ammonia nitrogen in the area.Therefore,bio-filtration technology was studied for treatment of low temperature?5-10??groundwater containing high concentration of iron,manganese and ammonia nitrogen."One-stage aeration combined with one-stage filtration"process and"two-stage aeration combined with two-stage filtration"process were carried out.Start-up cycle,purification efficiency,the oxidation-removal active sites?ORAS?of iron,manganese and ammonia nitrogen and kinetics were investigated.In addition,in order to solve the problem of the lack of dissolved oxygen?DO?for the purification of high iron,manganese and ammonia nitrogen,"Biological Aerated Filter"and"Biological Aerated Filter and Bio-filtration"process were carried out.What's more,A pilot-scale bio-filter coupled nitrification and completely autotrophic ammonium removal over nitrite?CANON?was started up in A plant,and the main removal route of ammonia nitrogen was analyzed based on quantitative relationship between nitrogen conservation and DO measurement.A new idea for the removal of high concentration iron,manganese and ammonia nitrogen from low temperature groundwater was provided.A pilot-scale bio-filter was constructed to removal of high concentration of iron?TFe 9.0-12.0 mg/L,Fe???6.5-8.0 mg/L?,manganese?Mn 1.9-2.1 mg/L?and ammonia nitrogen?NH₄⁺-N 1.4-1.7 mg/L?simultaneously from low temperature?5-6??groundwater in A plant.The results showed that iron can be removed at the beginning of the bio-filter start-up,and manganese and ammonia nitrogen were removed on 72 day and 75 day,respectively.The higher the filtration rate,the lower the removal of manganese.Manganese was the limiting factor for the increase of filtration rate,and the maximum filtration rate of the single bio-filter was 4.5 m/h.When the filtration rate was less than 6.0 m/h,the removal of ammonia nitrogen was about 1.5 mg/L,which was not affected by the filtration rate.DO deficiency lead to failure on more removal of ammonia nitrogen.The thickness of the bio-filter required for purification will increase as the concentration of manganese and ammonia nitrogen increased when DO is sufficient.The removal of iron,manganese and ammonia nitrogen will move to the depth of the filter layer,and there will be manganese?IV?"dissolution"when the filtration rate increased.Iron and ammonia nitrogen in the filter layer could be oxidized and removed simultaneously.Manganese is oxidized and removed after iron and ammonia nitrogen,the effective oxidation and removal section of manganese,iron and ammonia nitrogen are obviously graded.Due to the limited removal capacity for low temperature?5-7.8??groundwater containing high iron,manganese and ammonia nitrogen contents?TFe 12 mg/L,Fe???8.0-11.0 mg/L,Mn???3.0-3.5 mg/L,NH₄⁺-N 3.0-3.5 mg/L?in"One-stage aeration combined with one-stage filtration"process,and to improve the purification efficiency,the start-up of"two-stage aeration combined with two-stage filtration"purification process and the ORAS of iron,manganese and ammonia nitrogen were investigated.It turned out that two-stage bio-purification process could be started successfully after133 days and the start-up period was mainly related to the manganese content.The results showed that the removal capacity of ammonia nitrogen and manganese was29.66 g/?m²?h?and 27.08 g/?m²?h?respectively,and the water yield was double of one-stage bio-purification process.According to the ORAS,iron was removed to trace levels in the 0-50 cm section of the primary filter column,and the ammonia nitrogen was removed by 55.23%and 44.10%respectively in the 0-135 cm segment of the primary filter column and 0-50 cm segment of the secondary filter column.There was a significant classification between manganese and ammonia nitrogen during the oxidation-removal process.The activity of Mn-oxidizing bacteria?MnOB?was significantly inhibited by ammonia nitrogen in concentration greater than 2.25 mg/L.The removal ratio and ORAS of manganese in both filter columns were affected by the concentration of ammonia nitrogen in raw water as well as the filtration rate.After a successful start-up,the manganese was removed by 5.53%and 89.34%respectively in the primary and secondary filter columns.The experiments turned out that high concentrate iron,manganese and ammonia nitrogen?8-10?,TFe 17.66 mg/L,Mn1.71 mg/L,NH₄⁺-N 3.37 mg/L?can be successful to removal from low temperture groundwater by"two-stage aeration combined with two-stage filtration",and the maximum filter rate of the first stage and the second stage were 13.25 m/h and 12.75m/h.The amount of water produced was 1.59 times that of the B water plant where the test was conducted.In order to solve the problem of inadequate DO in the"One-stage aeration combined with one-stage filtration"process of removal of high iron,manganese and ammonia nitrogen from low tempreture groundwater.A pilot-scale bio-filter of CANON,"Biological Aerated Filter"and"Biological Aerated Filter and Bio-filtration"was started up to remove iron,manganese and ammonia nitrogen from groundwater.The experiments showed that the bio-filter could be started up successfully and stable operation after 98 days of culture.The purification of the water inlet Fe????9.87±1.17 mg/L?at the beginning of the biological filter started up can remove to 98%,the oxidation and removal of Mn???and NH₄⁺-N were2.25±0.06 mg/L and 1.51±0.06 mg/L,respectively.The calculation based on quantitative relationship between nitrogen conservation and DO measurement indicated that the contribution of CANON to NH₄⁺-N removal was 33.48%-38.87%.Value of?NH₄⁺-N/?NO₃^--N was 1.49.13.79%to 18.16%of dissolved oxygen can be saved compared to the"One-stage aeration combined with one-stage filtration"."Biological Aerated Filter"failed to removal of high concentration of iron,manganese and ammonia nitrogen from low temperature groundwater due to aeration on the water flow turbulence.It turned out that"Biological Aerated Filter and Bio-filtration"process could be started successfully after 42 days.The purification of the iron at the beginning of the biological filter started up can meet the standard.The standard purification of ammonia nitrogen can be achieved after 32 days of domestication and cultivation,and the oxidation and removal of NH₄⁺-N were 2.0-2.5 mg/L.The purification of manganese can meet the standard after 35 days of domestication and cultivation,and the oxidation and removal of manganese were 0.9-1.2 mg/L.The max filter rate of"Biological Aerated Filter and Bio-filtration"process was only 7.0 m/h due to aeration on the water flow turbulence.The oxidation kinetics demonstrated that iron was oxidized and removed followed the first-order chemical oxidation kinetics,and the oxidation kinetics constant was 1.02-1.18×10,and the removal of manganese and ammonia nitrogen followed the kinetic law of zero-order enzymatic reaction,and the oxidation kinetics constant were 0.15-0.83×10^-1 and 0.31-1.20×10^-1.The oxidation rate of iron was the fastest and was removed firstly.The order of oxidation and removal of manganese and ammonia nitrogen was greatly affected by substrate concentration.