Research On Treatment Of Groundwater Containing Iron And Manganese Contaminated By Ammonia Nitrogen And Organic Matter

Water is one of the essential resources for the survival of humanity.Water resources are not only essential for human life,but also play a decisive role in the evolution of human species.Groundwater is often used as a source of drinking water,but due to natural causes or human-induced pollution,groundwater often needs to be treated before it can be used as drinking water.This experiment studied a stable pumice biological aerated filter?BAF?process coupled with NaOCl oxidation-manganese sand filtration?MSF?technique.Under the condition of the process unit inlet flow rate of 294.12 m L/min,a simulated groundwater containing iron and manganese;iron,manganese and ammonia nitrogen;iron,manganese and organic matter were treated respectively.The influent concentrations of iron,manganese,ammonia nitrogen and humic acid in the simulated groundwater were varied between 0.3 and 6.0,0.1 and 3.0,0.5 and 2.0,1.0 and 6.0mg/L respectively.In this paper the removal effects and interactions between the different pollutants in the biological aerated filter and manganese sand filter were studied respectively as well as the effect of NaOCl dosage on the removal of the pollutants.It was found that when the raw water contain simultaneously and respectively,Fe²⁺=1.5mg/L,Mn²⁺=0.5mg/L;Fe²⁺=1.0mg/L,Mn²⁺=0.3mg/L,NH₄⁺-N=2.0mg/L and Fe²⁺=1mg/L,Mn²⁺=0.3mg/L,COD_Mn=7.89mg/L,UV254=0.113cm^-1 the BAF effluent can't meet the water quality standards anymore.When both iron and manganese are present in the BAF influent the high removal zone for iron is situated in the low part?0-10cm?of the filter and the higher removal zone for manganese is the upper part of the filter.When iron,manganese and ammonium are present simultaneously in the BAF influent raw water the high removal zone for Fe²⁺ and Mn²⁺ is situated in the 0-40 cm layer of the filter column and the high removal zone for NH₄⁺-N is situated in the upper part of the filter column.When iron,manganese and organic matter are present simultaneously in the BAF influent water the removal zone of iron is at the lower part of the pumice BAF?0-30cm?,while the removal zone of manganese is in the middle and the removal zone of the organic matter is at the top of the BAF filter column.The increase of ammonia nitrogen concentration in the BAF influent affects more manganese removal than it affects iron removal.The increase of organic matter in the influent affects iron ferrous,manganese,COD_Mn and UV254.Iron ferrous is slightly affected and UV254 is the most affected,its lower removal rate was 19.82%.Fe²⁺ removal is the ideal;it was always over 80%.The high and low ammonia removal rate was 82%and 33% respectively,for Mn²⁺ it was 90% and 41.93% respectively,for COD_Mn it was 51.64% and 31.76% respectively at p H=7.5.BAF process has excellent removal efficiency of iron ferrous,a good removal for manganese and ammonia nitrogen,but the removal rate of COD_Mn and UV254 was low.This is because the concentration of readily biodegradable organic matter in the raw water is very low,and it is an oligotrophic water source,which is not conducive to the growth and reproduction of microorganisms.The dissolved oxygen?DO?has a certain effect on the biological removal of the pollutants.When DO is insufficient,the concentration of ammonia nitrogen,manganese and COD_Mn of the BAF effluent increased and the dissolved oxygen gradually decreased along the filter column towards BAF outlet.The BAF pumice material has a bad effect on the turbidity removal and the high turbidity removal rate obtained was 55.4%.The amount of oxidant is a key factor in the removal of the pollutant.The increase of NaOCl dosage increases the removal rate of the pollutants.NaOCl reacts with Mn²⁺ and Fe²⁺ to form Mn and Fe oxides which coat the surface of the manganese sand material allowing the manganese sand filter to have a good absorbance effect on the pollutant.When both iron and manganese are present in the raw water iron is removed first followed by manganese,when iron,manganese and ammonia nitrogen are present simultaneously in the raw water iron is removed first followed by manganese and ammonia nitrogen,when iron,manganese and organic matter are present simultaneously in the raw water iron is removed first followed by manganese,COD_Mn and UV254.When MSF influent was Fe²⁺=0.23mg/L Mn²⁺=1.57mg/L it required 5.48mg/L of NaOCl dosage to remove completely iron and manganese from the water,the removal rate for Fe²⁺ and Mn²⁺ both was 100%.When Fe²⁺=0.12mg/L,Mn²⁺=0.14mg/L,and NH₄⁺-N=1.34mg/L,it required 11.0mg/L of NaOCl dosage to reach the water quality standard and the removal rate was 100% for Fe²⁺ and Mn²⁺ and 77.61% for NH₄⁺-N.When TFe=0.58mg/L,Fe²⁺=0.20mg/L,Mn²⁺=0.18mg/L,COD_Mn=4.08mg/L and UV254=0.083mg/L are present simultaneously in the MSF influent it required 8.0mg/L of NaOCl to meet the water quality standard and the removal rate was 74.13%,95.0%,77.78%,31.64% and 23.44% respectively under 8.0mg/L NaOCl dosage.This BAF NaOCl oxidation-MSF combined process has obvious advantages in water purification because it ensures good water quality,lessens the formation of disinfection by products and reduces water treatment costs.It can be used in water treatment plant where groundwater is used as water source.