What is the form of phosphorus in wastewater?
Phosphorus is an active element that does not exist in a free state in nature, but exists in three states: phosphorus-containing organic matter, inorganic phosphorus compound, and reduced PH3. Phosphorus compounds in sewage can be divided into organic phosphorus and inorganic phosphorus.
Almost all inorganic phosphorus exists in various phosphate forms, including orthophosphate, metaphosphate, hydrogen phosphate, dihydrogen phosphate, and polyphosphates such as pyrophosphate, triphosphate. Organophosphates are mostly organophosphorus pesticides, such as dimethoate, methyl parathion, ethyl parathion, malathion, etc. Most of them are colloidal and granular, insoluble in water, and easily soluble in organic solvents. Soluble organic phosphorus only accounts for about 30%, mainly in the form of glucose-6-phosphate, 2-phospho-glyceric acid, and creatine phosphate. Dissolved phosphorus accounts for about 1/3 of the total phosphorus, and the macromolecular phosphorus in PO4ˉ-P phosphorus accounts for 40%.
How is phosphorus transformed? What are the influencing factors?
The soluble phosphorus in water can quickly form insoluble precipitates with Ca2+, Fe3+, Al3+ plasma, AIPO4, FePO4, etc., deposited at the bottom of the water body as bottom sludge. The form and quantity of phosphorus accumulated in the bottom sludge are determined on the one hand by pollutant input and discharge through the surface and underground runoff; on the other hand, it is determined by the exchange of phosphorus in the water and phosphorus in the bottom sludge. Phosphorus in the sediments is again diluted into the upper water body through the suspension of particulate phosphorus and the turbulent diffusion of the water flow. The soluble phosphorus in the sediments greatly exceeds the phosphorus concentration in the water body, and it may be re-released into the water body.
In water, whether phosphorus ions exist in the form of HPO42ˉ or H2PO4ˉ depends on the pH value. When the pH value is 2-7, most of the phosphate ions in the water exist in the form of H2PO4ˉ, and when the pH value is 7-12, it is the phosphate in the water. Most of the ions exist in the form of HPO42ˉ. All phosphorus-containing compounds are first converted to orthophosphate (PO43ˉ) and then converted to other formats. At this time, measuring the content of PO, and the result of the measurement is the content of total phosphorus.
What are the sources of phosphorus?
Part of the phosphorus in sewage comes from chemical fertilizers and agricultural wastes. Simultaneously, the extensive use of phosphorus-containing detergents in daily life also significantly increases the phosphorus content in domestic wastewater. The wastewater discharged from the chemical, paper, rubber, dye and textile printing and dyeing, pesticide, coking, petrochemical, fermentation, pharmaceutical and medical, and food industries often contain organophosphorus compounds.
What is the harm of phosphorus?
(1) The harm of phosphorus to the human body
High-phosphorus washing powder directly affects the skin and can severely cause contact dermatitis, baby diaper rash, and other diseases. At the same time, phosphorus can cause harm to the nerve center, especially since some organophosphorus pesticides have poor biodegradability and are easy to remain in the environment，it is highly toxic to humans, livestock, and other vertebrates. They can inhibit the action of cholinesterase and affect the nervous system function, causing poisoning and even death.
(2) The harm of phosphorus to marine life
Currently, organophosphorus pesticides widely used are harmful to marine life, and organophosphorus can activate latent pathogens in shrimps. The deaths of fish and shrimps have emerged one after another, posing a threat to the maritime aquaculture industry.
(3) Phosphorus pollution to soil
Phosphorus pollution to the soil mainly comes from excessive use of pesticides, fertilizers, and sewage irrigation. Excessive phosphorus will exceed the self-purification capacity of the ground, causing undesirable changes in the soil and causing the natural, normal function of the environment to malfunction.
More severely, it will poison air and water quality, absorb through plants, reduce the physical quality of agricultural and sideline products, and cause residual toxins to pass through the plant chain and ultimately endanger human life and health.
(4) Excessive phosphorus has excellent harm to water bodies, causing eutrophication of water bodies
For triggering eutrophication of water bodies, the role of phosphorus is far more significant than that of nitrogen. When phosphorus concentration in the water body is not very high, it can cause eutrophication of water bodies.
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