How to treat the leachate from phosphogypsum piles after storage
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Our company’s phosphate ammonium fertilizer plant was established in 1991. The phosphogypsum generated during phosphate ammonium fertilizer production is stored in piles; to date, more than 3 million tons of this phosphogypsum has been accumulated. The leakage fluid from this phosphogypsum ends up in rivers, causing the phosphorus concentration in those waters to exceed normal levels by more than 20 times. Now, the local environmental protection authorities are demanding that this issue be addressed. Due to historical reasons, the phosphogypsum storage areas have not been equipped with any anti-leakage measures. After discussions and evaluations by relevant experts, no effective solution has yet been found for dealing with this leakage fluid. We invite everyone to share their opinions and suggestions on how to address this problem.
It’s completely possible to go back to the workshop for re-sizing.
Only by digging a drainage trench around the piled phosphogypsum can the leaked liquid be collected for treatment. Phosphogypsum can definitely be used as a raw material for cement, which would also serve as an example of a circular economy. However, by exposing it to the air without any protective measures, you are causing pollution. At present, this is just an issue of river pollution; but if it turns into a public safety hazard, it will become a serious problem. Act quickly – there’s still time to address it.
It indeed needs to be dealt with promptly; such a large volume should ideally be recycled. Ditches for collecting runoff water should be dug around the storage area to gather that water for treatment.
Phosphogypsum refers to the solid waste generated during the treatment of phosphate rocks with sulfuric acid in phosphate production, and its main component is calcium sulfate. The main component of phosphogypsum is CaSO4•2H2O; in addition, it contains various other impurities. Meanwhile, during the production process, HPO4-2 ions in the solution replace some of the SO4-2 ions in the gypsum lattice. Phosphogypsum impurities can be divided into two main categories: Insoluble impurities: such as quartz, undecomposed apatite, insoluble P2O5, eutectic P2O5, fluorides, and phosphates and sulfates of aluminum, magnesium, and fluorine. Soluble impurities: such as water-soluble P2O5, and fluorides and sulfates with lower solubility. In addition, phosphogypsum also contains arsenic, copper, zinc, iron, manganese, lead, cadmium, mercury, and radioactive elements. They are all present in extremely trace amounts, and most are insoluble solids; their hazard is negligible. Impurities in phosphogypsum such as fluorides, free phosphoric acid, P2O5, and phosphates are the main factors responsible for environmental pollution caused by phosphogypsum during storage. The massive accumulation of phosphogypsum not only occupies land resources unjustly but also causes pollution of the atmosphere, water systems, and soil due to wind and rain erosion. Prolonged exposure to phosphogypsum can certainly lead to death or illness in humans.
I wonder if your factory uses dry discharge or wet discharge? In the case of wet discharge, the water returned from the slag dump is always sent back for re-slurrying during design ； For dry drainage, it is recommended to establish isolation ditches around the perimeter of the slag site to collect leached rainwater and infiltrated wastewater. A passive approach is to send the excess water to wastewater treatment facilities, while a more proactive method is to reuse it in phosphate production, which not only eliminates pollution but also recovers phosphorus from it, yielding significant benefits.