Desalination processes and fertilizer production methods

Abstract

A multistage desalination process for treatment of seawater or salt wastewater. During initially processing the seawater or salt wastewater is treated to precipitate scaling minerals as phosphates including magnesium ammonium phosphate useful as a fertilizer. During the initial phase, ammonium phosphate and sodium phosphate are added to the seawater or salt wastewater followed by an addition of ammonia and a water-based charged solvent. After separating the precipitated solids, the cleaned seawater or salt wastewater is aerated and filtered to produce potable or otherwise usable water.

What is claimed: 
     
         1 . A seawater or salt wastewater desalination process comprising:
 performing a phosphate precipitation process, the phosphate precipitation process including adding a first mixture comprising ammonium phosphate and sodium phosphate to seawater or salt wastewater and mixing the first mixture and the seawater or salt wastewater;   after mixing the first mixture and the seawater or salt wastewater, adding a second mixture comprising ammonia and a water-based charged solvent to the seawater or salt wastewater and mixing to produce a seawater or salt wastewater mixture having a pH of greater than or equal to about 8.5;   performing a solids collection process to collecting precipitated solids from the seawater or salt wastewater mixture, the solids including, magnesium ammonium phosphate;   after performing the solids collection, performing an oxidation process comprising aeration of the seawater or salt wastewater mixture, followed by filtration removal of solids produced during the oxidation process; and   performing a final filtration process comprising microfiltration followed by nano-filtration of the seawater or salt wastewater to produce potable or usable water.   
     
     
         2 . The desalination process of  claim 1  further comprising filtering the seawater or salt wastewater mixture after the solids collection process. 
     
     
         3 . The desalination process of  claim 2  wherein the filtration comprises filtration through sand followed by carbon filtration or the like. 
     
     
         4 . A fertilizer production process comprising:
 providing seawater or salt wastewater;   performing a phosphate precipitation process, the phosphate precipitation process including:   adding a first mixture comprising ammonium phosphate and sodium phosphate to the seawater or salt wastewater and mixing the first mixture and the seawater or salt wastewater;   after mixing the first mixture and the seawater or salt wastewater, adding a second mixture comprising ammonia and a water-based charged solvent to the seawater or salt wastewater and mixing to produce a seawater or salt wastewater mixture having a pH of greater than or equal to about 8.5; and   performing a collection process to collect a fertilizer product comprising precipitated solids from the seawater or salt wastewater mixture, the solids including magnesium ammonium phosphate.   
     
     
         5 . The fertilizer production process of  claim 4  wherein the fertilizer product further comprises organic matter. 
     
     
         6 . The fertilizer production process of  claim 4  wherein the solids additionally contain potassium, calcium and other mineral salts. 
     
     
         7 . The fertilizer production process of  claim 4  wherein a seawater or salt wastewater is selected for processing such that the solids contain from about 8 to 20% by weight magnesium. 
     
     
         8 . The fertilizer produced by the process of  claims 4 - 7 .