Operating costs and sales market for the magnesium ammonium phosphate method for treating ammonia nitrogen in water
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Our company’s wastewater contains a certain amount of ammonia nitrogen. Through online research, I found that phosphates and magnesium salts can be used to react with the wastewater, resulting in the formation of a white precipitate of ammonium magnesium phosphate. The purpose of this is to remove the ammonia nitrogen. It is also said that ammonium magnesium phosphate can be sold as a pesticide. I would like to ask whether there is a market for such a pesticide that is not easily soluble in water. Additionally, I want to know if this process is feasible and what its operating costs are
The magnesium ammonium phosphate method is feasible for treating ammonia nitrogen, but the treatment cost is high; it is suitable for wastewater with high concentrations of ammonia nitrogen, and the treatment process is mature and easy to operate. The main requirements for such a process are maintaining a pH level of 10–10.5, as well as using magnesium; the ratios of nitrogen to phosphorus are roughly 1.3:1:1. The compound produced is ammonium magnesium phosphate, which is not a pesticide but rather a compound fertilizer that contains both nitrogen and phosphorus. It is generally used as a fertilizer for flowers. Ammonium magnesium phosphate breaks down over time in the environment, releasing ammonia and phosphorus – making it a good type of fertilizer. Since it costs over ten yuan to process one kilogram of nitrogen, while the magnesium ammonium phosphate produced can only be sold for 1-2 yuan per kilogram, it’s not cost-effective; therefore, it’s impossible to make a profit from this process. Selling magnesium ammonium phosphate is merely to reduce processing costs.
I’ve learned something new; when working on engineering commissioning in the past, I encountered shock loads related to NH3-N, which made it impossible to meet the required standards in a short period of time, and I didn’t know what to do. That makes it easy now. At that time, I also thought of increasing the amount of Cl to react and form chloramine, but I gave up on that idea. Fortunately, the system recovered in time during the acceptance process. Thank you to the original poster for the topic and to those who replied above.
It seems that maintaining a pH level of 10–10.5 during the precipitation process is problematic; under these conditions, ammonia exists mainly in gaseous form, while there is less ammonium ion present, which is necessary for precipitation. As a result, most of the precipitate will be magnesium phosphate. The phosphates, magnesium ions, and ammonium ions required for struvite precipitation are best obtained under slightly alkaline conditions; a pH range of 8 to 9 should work well.
There is another issue: when using ammonium precipitates, the addition of magnesium salts and phosphates may introduce a large number of unwanted ions, thereby increasing the salt content. Therefore, careful selection of reagents is necessary; it might be better to use soluble magnesium phosphates. I’m not very familiar with the economic value of struvite; I think it isn’t very valuable, and its level of acceptability is also unknown.
Thank you to everyone who replied above. I once conducted pilot tests in the laboratory, using a molar ratio of magnesium:nitrogen:phosphorus of 1.05:1:1, with the pH level kept around 9. However, the results I achieved were not as good as those described in various studies; my removal rate of ammonia nitrogen was only about 50%, whereas studies claim that a removal rate of 90% is generally achievable. I was wondering if anyone with experience in this area could help me analyze the situation. At the same time, I wonder if there are any industrialized companies; I’d like to learn more about them.
Using the same method to process one kilogram of nitrogen, the cost of the experiment is around 30 yuan. Why is your cost so low?
I just checked an article by a teacher from Tongji University regarding a previous meeting; the molar concentration ratio of magnesium:nitrogen:phosphorus is 1.25:1:1, and this can improve the removal rate of ammonia nitrogen. You might want to give it a try; I haven’t heard of any industrial installations using this method in China yet.
There is another issue: struvite is a real problem as it can clog pipes, so it is generally tried to be avoided. If this method is used to remove ammonia nitrogen, how can the lifespan of the equipment and pipelines be ensured? Let an expert with practical experience in this process answer
I agree with what was said above; we are also concerned about this issue, as well as questions such as whether stirring is necessary when responding. I hope there are professionals who understand this field, and I also hope there are existing industrialized cases that can serve as a reference. Last edited by Seeking help on 2009-2-13 08:13.]