Treating wastewater from fertilizer production is one of the major environmental challenges in the agricultural industry today. The process of manufacturing chemical fertilizers often generates wastewater polluted with ammonia, phosphate, heavy metals, and many other toxic substances, posing serious risks to the environment and human health if not thoroughly treated. Depending on the scale of the enterprise, fertilizer wastewater treatment involves various methods. Let's explore them below.
1. Characteristics of Fertilizer Production Wastewater
Wastewater in the fertilizer production industry arises from various sources such as raw material washing, equipment cooling, facility cleaning, as well as chemical reactions during the production of urea, DAP, NPK, etc. These activities typically generate a large volume of wastewater with high pollution characteristics, notably the presence of difficult-to-decompose inorganic and organic substances. In particular, the wastewater contains compounds such as ammonia (NH₃), nitrate (NO₃⁻), phosphate (PO₄³⁻), heavy metals, and industrial cleaning agents, resulting in strongly fluctuating pH levels and a high risk of pipeline corrosion if not properly controlled.
Incorrect wastewater treatment procedures can cause numerous negative environmental impacts. Specifically, discharging nitrogen and phosphate-rich compounds can lead to eutrophication of water bodies, fish deaths, and biodiversity loss. Furthermore, the presence of heavy metals and toxic substances threatens human health through the food chain and domestic water supply. This is why investing in a standardized wastewater treatment system is essential for every modern fertilizer manufacturing plant.
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Key Information on Current Fertilizer Production Wastewater
2. Top 7 Parameters That Must Be Treated in Fertilizer Wastewater
In fertilizer production wastewater treatment, accurately identifying the pollution parameters is crucial for selecting effective treatment technologies and methods. Below are the 7 most important parameters that must be closely monitored:
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Ammonia Nitrogen (NH₄⁺): A common component in fertilizer production wastewater, especially during urea manufacturing. When discharged into the environment, this compound can cause eutrophication, reduce dissolved oxygen in water, and harm aquatic life.
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Total Suspended Solids (TSS): Generated from dust, lime-neutralized sludge, or contaminants from equipment cleaning. TSS increases water turbidity and affects the efficiency of biological treatment.
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pH (Acidity/Alkalinity): Often unstable due to the use of H₂SO₄, H₃PO₄ (acidic) or NH₄OH, NaOH (alkaline). pH adjustment is vital to protect microorganisms and wastewater treatment equipment.
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Arsenic (As): Found in wastewater due to CO₂ absorption system leaks or pipe failures. This highly toxic heavy metal requires separate treatment.
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Chromate and Phosphate: Present in cooling system wastewater due to the use of anti-scaling and corrosion inhibitors. Treatment mainly involves reducing hexavalent chromium (Cr⁶⁺) to trivalent chromium (Cr³⁺), followed by precipitation as hydroxides.
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Cyanide (CN⁻): May appear due to raw material components or specific processes. Low concentrations can be diluted to permissible limits. For high concentrations, separate treatment is required using steam and acid gases to neutralize cyanide.
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Fluoride and Phosphate (F⁻, PO₄³⁻): Emerge from gas scrubbing, floor washing, and phosphate fertilizer production activities. Fluoride often exists as hydrofluoric acid, while phosphate appears as phosphoric acid or dissolved calcium phosphate salts.
3. Methods of Treating Fertilizer Production Wastewater
3.1 Physical Treatment Method
The physical method removes insoluble solid impurities from fertilizer production wastewater. The main goal is to separate large particles, sand, grease, and suspended solids from the water stream. Although it does not reduce the concentration of organic or toxic chemicals, this step helps reduce the load on subsequent treatment stages and protects pipelines and equipment from clogging or corrosion.
3.2 Chemical Treatment Method
Chemical treatment focuses on using chemical reactions to transform or precipitate hazardous pollutants. In fertilizer wastewater, substances such as ammonia, phosphate, heavy metals, and acid-base compounds are treated through neutralization, oxidation-reduction, coagulation, and flocculation. The use of chemicals such as lime, aluminum sulfate, or polymers helps precipitate toxic ions into sludge for easier separation. This method is particularly effective for pH adjustment and removing inorganic compounds that are difficult to handle biologically.
3.3 Biological Treatment Method
The biological method is applied to treat organic compounds based on the activity of microorganisms. In aerobic environments, microbes use oxygen to break down organic matter into CO₂ and water; while in anaerobic environments, treatment occurs without oxygen, producing CH₄ and CO₂. For fertilizer manufacturing, activated sludge systems, oxidation ditches, or UASB reactors are commonly used to optimize treatment efficiency. This method has the advantages of low operating costs, easy maintenance, and significant reduction of organic matter before discharge or advanced treatment.
Effective Fertilizer Wastewater Treatment Parameters
Accurate and comprehensive identification of pollution parameters in fertilizer production wastewater is the first and most critical step in designing an efficient treatment system. Each pollutant—such as ammonia nitrogen, TSS, pH, heavy metals, or toxic compounds like cyanide, sulfide, and fluoride—has unique properties and impacts on the environment and human health. Therefore, choosing the right treatment methods—ranging from physical to chemical and biological—is essential to ensure that the final effluent meets environmental technical standards. Investing in advanced treatment technology not only helps businesses comply with regulations but also contributes to water resource protection and sustainable development in the fertilizer industry.
