[Hongjie Water Service] Iron and manganese removal filter

1、 Introduction to Iron and Manganese Removal Equipment

Iron and manganese exist almost simultaneously in underground (well) water. When the iron content in the water is high, the water has a fishy smell, which affects the taste of the water. As a production water for papermaking, textiles, printing and dyeing, chemical industry, and leather refinement, it can reduce product quality. Iron containing water can cause rust spots on production tools, yellow or brownish yellow stains on washing clothes, and iron precipitate Fe2O3 can grow iron bacteria, block pipelines, and sometimes produce red water. Water with high manganese content is similar to water with high iron content, such as coloring, smelling, and smelling the water, damaging the quality of industrial products such as textiles, papermaking, brewing, and food. Household appliances will be contaminated with brown or black, and washing clothes will have slight black or light gray stains. Therefore, according to the "Hygienic Standards for Drinking Water in China" (GB5749-85), the iron content is ≤ 0.3 Å/L, and the manganese content is ≤ 0.1 Å/L. Raw water that exceeds the standard must be treated with a filter to remove iron and manganese. Drinking water with high levels of iron and manganese for a long time can seriously affect physical health and have a strong corrosive effect on production equipment.

Some well water with a general salt content within the range of brackish water is in a reduced state. The typical feature of this type of water source is the presence of divalent iron ions and manganese ions. If chlorine treatment is applied to such water sources, iron and manganese removal filters can be used to effectively treat the iron and manganese in groundwater.

2、 Overview of water quality containing iron and manganese

Surface water contains abundant dissolved oxygen, and iron and manganese mainly exist in the form of insoluble Fe (OH) 3 and MnO2. Therefore, the content of iron and manganese is not high and can be removed in pre-treatment processes. The iron and manganese content in groundwater in China is generally less than 5-10mg/L, and the manganese content is about 0 5-2mg/L, iron and manganese can coexist in groundwater, with iron content often higher than manganese content. For production water, exceeding the standards for iron and manganese content will reduce product quality; There are specific requirements for the iron content in the influent of ion exchange resin and membrane treatment.

3、 Iron manganese filter

After inflating or adding oxidants to groundwater containing iron (manganese), the iron (manganese) ions in the water begin to oxidize. When the water flows through the iron and manganese removal filter, contact oxidation reactions occur in the filter layer, as well as biochemical and physical retention adsorption reactions on the filter material surface, causing the precipitation and removal of iron (manganese) ions in the water. Especially in the process of treating micro polluted manganese containing groundwater, iron bacteria can not only effectively remove iron and manganese, but also use ammonia as a nutrient source in the water for metabolism. With the participation of other bacteria, they can also achieve the effect of removing ammonia nitrogen.

4、 Iron and manganese removal process

（1） Iron removal from groundwater

Generally, contact oxidation or aeration oxidation methods are used. When affected by silicates, contact oxidation method should be used.

The process of contact oxidation method: raw water aeration one → contact oxidation one → filtration. After contact oxidation aeration, the pH value of water should reach 6.0 or above.

The process of aeration oxidation method: aeration of raw water → oxidation → filtration. After aeration with the aeration oxidation method, the pH value of the water should reach 7.0 or above.

（2） Manganese removal from groundwater

The contact oxidation method should be used, and its process flow should be determined based on the following conditions: when the iron content in the raw water is less than 2 When the manganese content is less than 1.5mg/L and 0mg/L, the following methods can be used: primary aeration of raw water → single stage filtration for iron and manganese removal.

When the iron or manganese content of the raw water exceeds the above values, it should be determined through experiments. If necessary, the following methods can be used: aeration of the raw water ->oxidation ->secondary filtration to remove iron ->secondary filtration to remove manganese.

When iron removal is affected by silicates, it should be determined through experiments. If necessary, the following methods can be used: primary aeration for iron removal (contact oxidation), secondary aeration for manganese removal.

Note (1) The pH value of the water before filtration in the manganese removal filter should reach 7.5 or above.

(2) The iron content in the pre filtration water of the secondary manganese removal filter should be controlled at 0 Below 5mg/L.

（3） Removal of iron and manganese from brackish water

Some well water with a general salt content in the range of brackish water is in a reduced state. The typical feature of this type of water source is the presence of divalent iron ions and manganese ions. If chlorination treatment is carried out on such water sources, followed by dechlorination treatment, or if the oxygen content in the water reaches 5 X 10-6 or more, divalent iron will be converted into trivalent iron and form insoluble colloidal hydroxide particles. Below is the oxidation reaction of ferrous and manganese

4Fe (HCO3) 2+O2+2H20- → 4Fe (OH) 3+8CO2

4Mn (HC03) 2+O2+2H20- → 4Mn (OH) 3+8CO2

Because the pH value of iron oxidation is lower, the frequency of iron pollution blockage is much higher than that of manganese pollution blockage. Even SDI,. Less than 5, the ferrous content in the influent of reverse osmosis and nanofiltration is less than 0 1mg/L, there will still be pollution and blockage problems. Due to the extremely low solubility of FeCO3, the concentration of Fe+is constrained by the solubility of FeCO3. Generally, water sources with low alkalinity have higher iron concentrations than those with high alkalinity.

The possible scenarios that can cause soluble divalent iron and related trivalent iron pollutants to deposit on the membrane surface in a membrane treatment system are:

(1) Oxygen enters the water containing divalent iron;

(2) High alkalinity water sources form FeC03;

(3) Iron reacts with silicon to form insoluble ferrosilicon salts;

(4) Affected by the oxidation of iron reducing bacteria, it will intensify the growth of biofilms and the deposition of iron scale;

(5) Colloidal iron caused by the transformation of iron containing flocculants;

(6) Sediments generated from corrosion of steel pipes or other components;

(7) Mixing water sources containing divalent iron with water sources containing H2S forms black insoluble iron sulfide.

One method of dealing with such water sources is to prevent the entire system from coming into contact with air or any oxidant (such as chlorine). A low pH value is beneficial for inhibiting the oxidation of Fe2+, and when pH<6, oxygen is less than 0 At a concentration of 5mg/L, the maximum allowable concentration of Fe2+is 4mg/L.

Shenzhen Hongjie Water Technology Co., Ltd. is an integrated high-tech enterprise specializing in product research and development, production, sales, engineering design, installation and commissioning, technical consulting, and sales of supporting materials in the fields of industrial water treatment and drinking water treatment. Main products: A high-tech manufacturer specializing in the design, manufacturing, installation, commissioning, and maintenance of water treatment equipment, including pure water equipment, ultra pure water equipment, reverse osmosis equipment, GMP purified water equipment, EDI deionized water equipment, domestic sewage equipment, industrial wastewater equipment, softened water equipment, and reclaimed water reuse equipment.