Wastewater treatment process

1. Overview of sewage

1.1 Characteristic factors of sewage

The sewage discharge of nitrogen fertilizer enterprises has always been high concentration ammonia nitrogen wastewater, which has a certain impact on human health and aquatic organisms. The main characteristic factors in wastewater discharge are pH, ammonia nitrogen, petroleum, chemical oxygen demand, suspended solids, etc. Among them, PH、 Ammonia nitrogen and chemical oxygen demand are in a relatively high concentration range, and the main reason for the high pH and ammonia nitrogen content is due to the leakage of condensate; The high concentration of chemical oxygen demand is mainly caused by domestic sewage and surrounding commercial water. The main pollutant discussed in this article is ammonia nitrogen in wastewater.

1.2 Hazards of Ammonia Nitrogen Wastewater

Low concentration ammonia nitrogen wastewater can be used as agricultural fertilizer, but high concentration ammonia nitrogen wastewater is harmful to human and biological health. High concentrations of ammonia nitrogen can cause eutrophication of water bodies, decrease in dissolved oxygen concentration, adverse effects on downstream fishery water use, and on human and aquatic organisms.

1.3 Source of Ammonia Nitrogen Wastewater

Ammonia nitrogen wastewater comes from the leakage of condensate wastewater in the production process and equipment maintenance discharge. Due to the different process equipment and processes of nitrogen fertilizer enterprises, the discharge of ammonia nitrogen content in wastewater also varies. Old nitrogen fertilizer companies, due to outdated process equipment and normal wastewater discharge during parking and maintenance, can cause high concentrations of ammonia nitrogen in the wastewater. Therefore, in recent years, more and more nitrogen fertilizer enterprises have paid attention to the pollution control of ammonia nitrogen wastewater, and have carried out ammonia nitrogen wastewater treatment projects of different scales and technical methods, significantly reducing the concentration and discharge of ammonia nitrogen in the wastewater, achieving both standard discharge and energy conservation and emission reduction, achieving a win-win situation of economic and environmental benefits.

2. Common ammonia nitrogen wastewater treatment technologies

With the development of China's economy and the fact of the Western Development Strategy, more and more nitrogen fertilizer enterprises are building new ones in Xinjiang, which has had a certain impact on the environmental carrying capacity of Xinjiang. With the new construction and implementation of these enterprises, sewage discharge has become a difficult problem, so sewage treatment projects have been given more attention. With the continuous development of the environmental protection industry, more and more sewage treatment technologies are being developed and implemented. How to choose suitable sewage treatment technologies for nitrogen fertilizer enterprises requires nitrogen fertilizer enterprise personnel to constantly update, understand and learn about sewage treatment technologies. At present, there are several main technologies for treating ammonia nitrogen wastewater, including:

2.1 Ammonia Blowoff (Stripping) Denitrification Technology

Ammonia stripping technology is applied to the treatment of various concentrations of ammonia nitrogen wastewater, mainly used for the treatment of medium and high concentration ammonia nitrogen wastewater. The main mechanism is to first add alkaline solution to the wastewater to make it alkaline, and then blow off ammonia through a blow off tower (with air and steam introduced). The main advantages are simple process flow, low infrastructure and operating costs, stable effects, and strong practicality. The disadvantage is high energy consumption, high ammonia nitrogen content in the effluent, which can easily cause secondary pollution, low removal efficiency, and requires adding acid solution for acid-base neutralization before biological treatment to achieve ideal removal efficiency and discharge concentration.

2.2 Electrodialysis denitrification technology

Electrodialysis technology is applied to the treatment of high concentration ammonia nitrogen wastewater. The main mechanism is the physical and chemical process of transferring ions from one end to the other using the selective permeability of ion exchange membranes under the action of DC power plants. The main advantages are mature technology, high removal efficiency, low material consumption, compact equipment, small footprint, simple operation, and easy implementation of mechanization and automation. The disadvantage is that certain ions and pollutants in the wastewater can contaminate the membrane, resulting in high power consumption, complex installation, and easy scaling during operation. It must be prevented by frequent machine operation, and the water recovery rate is low.

2.3 Deep hydrolysis technology of urea

Deep hydrolysis technology is mainly used to recover high concentration ammonia nitrogen wastewater for comprehensive utilization, achieving the goal of treating ammonia nitrogen wastewater. The main mechanism is the reverse reaction of urea synthesis, which utilizes high-temperature steam to decompose urea solution in wastewater into ammonia and carbon dioxide, which are then returned to the device for comprehensive utilization. The main advantages are simple equipment, easy operation, low operating costs, low wastewater discharge, low discharge concentration, and high removal efficiency. The disadvantage is that it is greatly affected by operating temperature, residence time, and concentration.

2.4 Biological denitrification method

The technology of biological denitrification (i.e. short-range nitrification denitrification) is to oxidize ammonia nitrogen in wastewater into nitrite or nitrate under the action of well nourished nitrifying bacteria. Then, under the action of anaerobic nitrifying bacteria, the nitrifying products of nitrifying bacteria, nitrite and active nitrate, are reduced to nitrogen and discharged. The advantages of this technical method are stable performance, high removal efficiency, low investment, and low operating costs. The disadvantages are large footprint, low efficiency at low temperatures, susceptibility to toxic substances, and high requirements for ammonia nitrogen concentration.

2.5 Chemical precipitation method

The chemical precipitation method for treating ammonia nitrogen wastewater is to add a certain chemical raw material based on the properties of ammonia nitrogen in the discharged wastewater, and carry out chemical reactions under certain process conditions such as temperature, pressure, pH value, etc., to generate insoluble or poorly soluble precipitates or polymers, thereby achieving the goal of water purification. The advantages of this technology method are small footprint, low investment, low operating costs, and stable efficiency. The disadvantage is that the removal efficiency is low, and there is a lot of sediment that needs to be cleaned regularly.

3. The connection between sewage treatment and environmental protection

With the continuous development of the economy, China's nitrogen fertilizer industry has also shown a trend of continuous growth and expansion. Nitrogen fertilizer enterprises have evolved from using heavy oil as raw material to using coal and natural gas as raw materials. Due to different energy structures, the pollution to the environment has also varied. Some nitrogen fertilizer enterprises, due to their long establishment time, outdated process equipment, frequent equipment leakage, and negligence of management personnel, can cause environmental pollution and material waste. In the wastewater discharge of nitrogen fertilizer enterprises, the main pollutant is ammonia nitrogen. Therefore, the pollution control of ammonia nitrogen wastewater is particularly important. Only by treating ammonia nitrogen well can it not have adverse effects on the surrounding environment. To meet environmental protection requirements, it is necessary to start from the following points:

(1) Intensify efforts in pollution control. By monitoring the pollution factors at each discharge outlet and identifying the sources of pollution, timely rectification can be carried out for those that can be achieved through environmental management measures; For those who can only achieve environmental goals through environmental governance projects, on-site research and investigation can be conducted on multiple companies in the same industry to understand suitable environmental governance technologies for the companies, select appropriate environmental governance plans, and carry out phased environmental governance projects to ensure emissions meet standards and achieve energy conservation and emission reduction.

(2) Strengthen publicity and effectively raise employees' awareness of sewage treatment and environmental protection. Utilize various forms such as radio, television news media, bulletin boards, and promotional brochures to promote and educate all employees to start from themselves and enhance their awareness of environmental governance.

(3) Enhance employees' initiative in environmental behavior through a monthly reward assessment system. By monitoring data from each discharge outlet on a monthly basis, conducting irregular inspections, and reviewing online monitoring data of wastewater on an irregular basis, the pollution discharge behavior of each workshop is ranked, rewarded, and assessed. Through economic means, the enthusiasm of employees is mobilized, and their environmental awareness is continuously improved, achieving timely detection of problems and reporting for rectification.

(4) Develop a comprehensive environmental management system. By referring to the systems of the same industry and combining them with the operational status of the enterprise itself, a sound environmental management system can be developed to ensure that rewards and punishments are based on each other.

(5) Strengthen employee training. Regularly organize training on the process system of environmental protection facilities for employees, understand the operating parameters of environmental protection facilities, wastewater discharge indicators, troubleshooting requirements, etc., strengthen training for employees, and enable them to handle and solve emergencies in a timely manner.

4 Conclusion

In short, actively treating ammonia nitrogen wastewater in nitrogen fertilizer enterprises is a noteworthy issue. By implementing sewage pollution prevention and control projects for nitrogen fertilizer enterprises, the simultaneous promotion of environmental protection and pollution control can be achieved. Specifically:

(1) Intensify theoretical experimental research on advanced ammonia nitrogen wastewater treatment technologies, and encourage scholars and experts to develop new technological methods and achieve new breakthroughs in the field of ammonia nitrogen wastewater treatment through a series of measures.

(2) Intensify the introduction of advanced international and domestic ammonia nitrogen wastewater treatment technologies, actively learn from advanced foreign technologies, and combine them with the actual situation in China to truly apply advanced technologies to actual ammonia nitrogen wastewater treatment work, achieving new breakthroughs in wastewater treatment work.

(3) Intensify the cultivation of professional talents in the construction of high-quality and high-quality ammonia nitrogen wastewater treatment, work with a high sense of responsibility, and improve work efficiency.