磷酸盐是磷酸的盐类. Phosphorus is derived from the Greek “phōsphoros,” meaning “morning star” or “bringer of light.” It is the 15th element in the periodic table and is essential to all life, 人体平均含有25个.6盎司(751美元).3 g). It is found in products ranging from kitchen matches to conversion coatings for corrosion resistance (as phosphates).
Phosphate conversion coatings on metals are used to impart corrosion resistance and lubricity, or to serve as a base layer for subsequent coatings, 比如油漆, 染料等. In simple terms, the process solution consists of a phosphate salt in a solution of phosphoric acid. The immersion process is commonly applied to steel parts, but is also applicable to other metallic substrates, 包括锌, 镉和锡, 等. The conversion coating consists of a phosphate of the substrate metal (for example, 磷酸铁(以钢为例).
除了表面处理应用, 磷酸盐化学在商业上有广泛的应用, 包括农业和其他领域. 相应的, phosphates in process wastewater can produce serious problems in the environment, 最有害的是富营养化.
Eutrophication is caused by excessive phosphorus in water. 在河流和小溪中, eutrophication can result in serious algae blooms, 从中产生有害的毒素. A few of the more serious consequences are fish kills, 气味, 饮用水供应有恶臭味, visual unpleasantness and closed public lakes in recreation areas.
1972年的《澳门威尼斯人网上赌场》赋予了美国.S. Environmental Protection Agency (EPA) permission to establish guidelines for water and wastewater, 包括磷酸盐. The EPA established standards for the wastewater discharge of phosphates to receiving bodies of water as follows:
• 小溪和河流- 0.1 ppm
•溪流进入湖泊- 0.05年ppm
•湖泊和水库- 0.025 ppm
The EPA guidelines for nutrient management recommend that publicly owned treatment works (POTWs) charge surcharges whenever the following limits are not met:
• Biochemical oxygen demand (BOD) limit of 210 ppm with a surcharge of $0.每磅232元
• Total suspended solids (TSS) limit of 230 ppm with a surcharge of $0.每磅186
• Total nitrogen limit of 30 ppm with a surcharge of $1.每磅17英镑
• Total phosphorus limit of 12 ppm with a surcharge of $1.每磅32
An industry is given a permitted amount of phosphorus they can discharge (for example, 15 lbs./day with a total discharge flow of 150,000 gal/day (GPD)). To convert pounds to parts per million (ppm): ppm = lbs. 化学/ 8.34 × MGD(百万加仑/天). 例如，15磅./天，15万GPD, 1 /8.34 x 0.15 MGD = 11.99 ppm. This means that 12 ppm of phosphorus can be discharged to meet the permit. Anything more can carry a surcharge per EPA recommendations.
除磷: There are today two primary technologies for phosphate removal from wastewater — chemical and biological.
化学去除: A number of chemical agents have been used to remove phosphorus from wastewater. In an alkaline solution, calcium reacts to form calcium carbonate. At pH ≥ 10, the excess calcium bonds with phosphorus to precipitate as a hydroxyapatite. 例如，Copperas, ferrous sulfate) or iron bonds with phosphorus to form iron phosphate, 哪些容易沉淀出来. 明矾, 或者更常见的明矾钾, 大韩航空(SO4) 2•12水), 就像钙一样, but its usage will be based upon removal requirements. Current research in our laboratory is underway involving new technology. This technology has a long track record of proven success and is readily available, 成本效益高，易于操作.
生物去除: Certain bacteria are capable of storing phosphorus as a polyphosphate and are referred to as polyphosphate-accumulating organisms (PAO). These systems involve different setups, depending on the type of bacteria. In industrial applications, biological removal is used as a “Final Polish” to achieve permit limits. Research is also being done on biological phosphate removal. This technology has been shown to be an efficient means of phosphate removal. There are multiple types of systems to choose from and training is readily available to new operators.
The ultimate goal of all of these efforts is a clean environment. 例如, a Hypoxia Task Force currently involves 11 states and the EPA working together to reduce the size of the Gulf of Mexico’s dead zone. This zone comprises the largest hypoxia zone in the United States. The task force was established in May 1998 with a charter. 成员包括联邦, 州和部落代表, and they are diligently working to solve this serious problem.
在其他地方, industries are driving research for better practices from non-phosphate cleaners to alternatives to phosphate coatings. Non-phosphate cleaners are being developed and widely used. Zirconium is replacing phosphate in paint preparation lines. Phosphate recovery systems are being utilized and new technologies for phosphate lines are close to industrial use.
除了这些努力之外, each state is working on a tailored nutrient management plan for recovery of impaired waters.
