Phosphorus and nitrogen are known causes of eutrophication in rivers, lakes streams and estuaries. The sources of these nutrients are diverse and they include chemical fertilizers, CAFOs (Confmed Animal Feeding Opera...Phosphorus and nitrogen are known causes of eutrophication in rivers, lakes streams and estuaries. The sources of these nutrients are diverse and they include chemical fertilizers, CAFOs (Confmed Animal Feeding Operations), land application of animal and municipal as well as industrial wastewaters. Application of manure slurries to crop land beyond allowable limits could result in high levels of phosphorus and nitrogen in runoff that negatively impact aquatic animals. Municipal wastewater treatment plants are setup to remove these nutrients from domestic and industrial wastewater through a network of treatment processes. Controlling the discharge of phosphorus and nitrogen in wastewater is a key factor in preventing eutrophication. This paper presents work done to enhance a chemical precipitation process that removes over 90% of dissolved phosphorus and nearly 20% of dissolved nitrogen from both synthetic and municipal wastewaters. The objective of the study is to remove nitrogen and phosphorus from wastewater as dittmarite, a value-added mineral fertilizer found in nature. A laboratory procedure was developed that generated significant quantities of dittmarite from various wastewaters. Pure dittrnarite contains nitrogen, phosphorus and magnesium in approximate molar ratios of 1:1.2:1.2 that can support plant growth. It is produced as a wet precipitate from chemical reactions that occur in the wastewater treatment process; it can be dried for proper handling and utilization. Municipal wastewater treatment plants, high volume fish producers, CAFOs and individual rural homeowners could all benefit from this technology for on-site removal of nitrogen and phosphorus from produced wastewaters.展开更多
Dittmarite is a naturally occurring mineral which is also produced by municipal wastewater treatment processes.It contains ammonium:magnesium:phosphate in molar ratios of 1:1.25:1,respectively.Dittmarite(MgNH4PO4·...Dittmarite is a naturally occurring mineral which is also produced by municipal wastewater treatment processes.It contains ammonium:magnesium:phosphate in molar ratios of 1:1.25:1,respectively.Dittmarite(MgNH4PO4·H2O)has a very stable crystalline structure,its solubility constant(Kso)is a product of the activity coefficient(?)and the activity of the individual species that make up the compound.The conditional solubility product,PS=CT,Mg CT,NH4 CT,PO4=Kso/αMgαNH4αPO4?Mg?NH4?PO4.A theoretical plot of-log Ps vs.pH gives a pH of 10.7 for maximum dittmarite precipitation,albeit precipitation may begin at lower pH values.The pKso for dittmarite at 25°C is determined to be 13.359 from the final equilibrium pH values taking all relevant magnesium,phosphate and ammonium species into account.The geochemical speciation model,MINTEQA2 was used to verify the optimum conditions for the precipitation of dittmarite.Such theoretical predictions allow the control of phosphorus and nitrogen discharges from animal and municipal wastewaters and serve as key factors in preventing surface water eutrophication and groundwater pollution.展开更多
文摘Phosphorus and nitrogen are known causes of eutrophication in rivers, lakes streams and estuaries. The sources of these nutrients are diverse and they include chemical fertilizers, CAFOs (Confmed Animal Feeding Operations), land application of animal and municipal as well as industrial wastewaters. Application of manure slurries to crop land beyond allowable limits could result in high levels of phosphorus and nitrogen in runoff that negatively impact aquatic animals. Municipal wastewater treatment plants are setup to remove these nutrients from domestic and industrial wastewater through a network of treatment processes. Controlling the discharge of phosphorus and nitrogen in wastewater is a key factor in preventing eutrophication. This paper presents work done to enhance a chemical precipitation process that removes over 90% of dissolved phosphorus and nearly 20% of dissolved nitrogen from both synthetic and municipal wastewaters. The objective of the study is to remove nitrogen and phosphorus from wastewater as dittmarite, a value-added mineral fertilizer found in nature. A laboratory procedure was developed that generated significant quantities of dittmarite from various wastewaters. Pure dittrnarite contains nitrogen, phosphorus and magnesium in approximate molar ratios of 1:1.2:1.2 that can support plant growth. It is produced as a wet precipitate from chemical reactions that occur in the wastewater treatment process; it can be dried for proper handling and utilization. Municipal wastewater treatment plants, high volume fish producers, CAFOs and individual rural homeowners could all benefit from this technology for on-site removal of nitrogen and phosphorus from produced wastewaters.
文摘Dittmarite is a naturally occurring mineral which is also produced by municipal wastewater treatment processes.It contains ammonium:magnesium:phosphate in molar ratios of 1:1.25:1,respectively.Dittmarite(MgNH4PO4·H2O)has a very stable crystalline structure,its solubility constant(Kso)is a product of the activity coefficient(?)and the activity of the individual species that make up the compound.The conditional solubility product,PS=CT,Mg CT,NH4 CT,PO4=Kso/αMgαNH4αPO4?Mg?NH4?PO4.A theoretical plot of-log Ps vs.pH gives a pH of 10.7 for maximum dittmarite precipitation,albeit precipitation may begin at lower pH values.The pKso for dittmarite at 25°C is determined to be 13.359 from the final equilibrium pH values taking all relevant magnesium,phosphate and ammonium species into account.The geochemical speciation model,MINTEQA2 was used to verify the optimum conditions for the precipitation of dittmarite.Such theoretical predictions allow the control of phosphorus and nitrogen discharges from animal and municipal wastewaters and serve as key factors in preventing surface water eutrophication and groundwater pollution.