Nitrate is one of the important indicators that cause eutrophication of water bodies and affect the quality of drinking water. According to relevant data, nitrate is the most common pollutant in groundwater pollution sources.
Nitrate itself is not harmful, but in an oxygen-deficient environment (such as the human body, and water purifiers that have not been replaced for a long time, etc.), it may become nitrite through the action of nitrate-reducing bacteria, and nitrite will cause "blue water". Infant syndrome and the incidence of gastric cancer, colorectal cancer, lymphoma and other diseases have increased.
It can be seen that it is particularly important to solve the problem of nitrate in drinking water, and the concentration of nitrate in drinking water needs to be limited. According to the relevant regulations in the national "Drinking Water Hygienic Standards" GB5749-2006 Water Quality Routine Indicators and Limits, it is stipulated that nitrate (calculated as N) is limited to 10mg/L, and groundwater sources are limited to 20mg/L. So, what are the effective solutions for this at present?
Currently, methods for treating nitrate in drinking water are divided into three categories: biological denitrification, chemical denitrification, and physicochemical methods.
1. Biological denitrification method
It uses denitrifying bacteria to reduce nitrate to nitrogen under anoxic conditions. This method is considered to be the most potential method for denitrification of drinking water because of its high efficiency and low consumption.
No waste liquid, low cost, suitable for large-scale production scenarios
Selective removal of nitrate and conversion into harmless nitrogen; no waste liquid generation, low treatment costs; suitable for large-scale production of drinking water scenarios.
The process is complicated and easy to cause secondary pollution
The process is complicated and the requirements for operation and management are high; it is easy to cause secondary pollution (dosing organic matter, such as methanol, etc.), but subsequent treatment is required to remove excess organic matter, the process is complicated and the cost is high; at the same time, the denitrification speed is slow and the required reaction The volume of the device is large and the construction cost is high, so it is not suitable for small-scale and decentralized water supply treatment of rural drinking water.
2. Chemical denitrification method
Chemical denitrification is a process in which nitrate in groundwater is reduced to nitrogen or ammonium ions using a certain reducing agent. There are active metal (iron, aluminum, cadmium, etc.) denitrification and catalytic denitrification (H2 as reducing agent, precious metal as catalyst).
Cost-effective and low requirements
Compared with biological denitrification, chemical denitrification has faster reaction speed, lower management and operation requirements, potential economy and adaptability to small or dispersed water supply treatment. Catalytic denitrification method is also because of its unique efficiency and thoroughness. attention to advantage.
Affected by mass transfer factors, the practicality is limited
The selectivity and activity of the chemical denitrification method are greatly affected by mass transfer factors during the reaction process, which limits the practicability of the method.
3. Physical and chemical method
Physicochemical methods include reverse osmosis, electrodialysis, and ion exchange.
Reverse osmosis + electrodialysis: the follow-up process is complicated and the practicability is poor.
It is mainly suitable for water with high TDS content and seawater desalination. For water with low TDS content, the treatment cost is much higher than that of ion exchange method. Since the membrane has no selectivity for nitrate, it is "one membrane removes all" for inorganic ions. This not only produces concentrated inorganic salt wastewater, but also has wastewater discharge problems, while changing the composition of the water. No matter in terms of drinking water health or cost, the practicability of membrane technology is poor.
4. Ion exchange method
This method belongs to process innovation and concept upgrade, which can perfectly solve inherent problems. The processing precision is high, and nitrate nitrogen (nitrite nitrogen, nitrate nitrogen) can be achieved below 1ppm, which is stable to the third category on the surface. It is a high-quality selection process for standard upgrading and transformation projects; The saturated adsorption capacity can reach more than 10g/l; the resin preferentially exchanges nitrate, and the exchange capacity of nitrate is not affected by the sulfate content in water; food-grade materials can be used for drinking water, groundwater, mineral water and other nitrate Deep removal of nitrogen; modular component form, high degree of automation and simple operation.
Type macroporous strongly basic anion exchange resin A-62MP (food grade)
functional group type I quaternary ammonium functional group
treatment accuracy 0.1mg/l
regeneration agent sodium chloride (about 10% concentration)
regeneration agent dosage 1BV-2BV
regeneration flow rate 2BV/ H
regeneration time 30-60 minutes
backwash water pure water/soft water/tap water
backwash flow rate 5-10BV/H
backwash time 30 minutes
Advantages of ion exchange technology for nitrate removal:
1. The treatment accuracy of nitrate resin, the total nitrogen content in all kinds of wastewater can reach 1ppm, which is stable and up to the standard;
2. The adsorption capacity is large, and the saturated adsorption capacity for nitrate (calculated as N) can reach more than 10g/l ;
3. The resin preferentially exchanges nitrate, and the exchange capacity of nitrate is not affected by the sulfate content in water;
4. It is a food material and can be used for deep removal of nitrate nitrogen in drinking water, ground water, mineral water, etc.;
5. It can carry out advanced treatment of low-concentration wastewater, and the concentration ratio can solve the problem of low-concentration wastewater treatment;
6. Modular component form, automatic degree, and simple operation.
Nitrate removal for drinking water;
nitrate removal for mineral water;
nitrate removal for groundwater ; deep treatment of total
nitrogen in coal mine water; deep treatment of nitrate in landfill leachate; deep treatment of nitrate nitrogen in electroplating wastewater; deep treatment of total nitrogen in photovoltaic pickling wastewater; Advanced treatment of total nitrogen in slaughter wastewater; nitrate removal in domestic sewage; nitrate removal in fertilizer manufacturing wastewater; nitrate removal in iron and steel production wastewater; nitrate removal in livestock feed farm wastewater; nitrate removal in electronic component production wastewater; oxidation of organic and fuel production wastewater In addition to nitrates, etc.