Systems and methods for removing phosphorus from water

Abstract

A water treatment system includes a coagulating and flocculating system, an ultrafiltration membrane, and a fluid driver. The coagulating and flocculating system includes a first inlet for receiving water and a second inlet configured to receive a coagulating and flocculating agent. The coagulating and flocculating system is configured to precipitate dissolved phosphorous from the water, and to provide a flocculated effluent at an outlet of the coagulating and flocculating system. The ultrafiltration membrane includes an inlet that is fluidly coupled to an outlet of the coagulating and flocculating system. The ultrafiltration membrane is configured to separate the precipitated phosphorus from the flocculated effluent. The fluid driver is adapted to transfer the flocculated effluent from the outlet of the coagulating and flocculating system to the inlet of the ultrafiltration membrane at sustained flux rates of at least 150 LMH.

What is claimed is: 
     
         1 . A water treatment system, comprising:
 a coagulating and flocculating system comprising a first inlet for receiving water and a second inlet configured to receive a coagulating and flocculating agent, wherein the coagulating and flocculating system is configured to precipitate dissolved phosphorous from the water using the coagulating and flocculating agent, and to provide a flocculated effluent at an outlet of the coagulating and flocculating system, wherein the flocculated effluent comprises precipitated phosphorus solids;   an ultrafiltration membrane comprising an inlet, a first outlet, and a second outlet, wherein the inlet of the ultrafiltration membrane is fluidly coupled to the outlet of the coagulating and flocculating system; and   a fluid driver adapted to transfer the flocculated effluent from the outlet of the coagulating and flocculating system to the inlet of the ultrafiltration membrane at sustained flux rates of at least 150 LMH, wherein the ultrafiltration membrane is configured to separate the precipitated phosphorus solids from the flocculated effluent to provide a low-phosphorus stream at the first outlet and a high-phosphorus stream at the second outlet.   
     
     
         2 . The water treatment system of  claim 1 , wherein the coagulating and flocculating system is fluidly coupled to one of a potable water supply or a portion of a wastewater treatment system, and wherein the coagulating and flocculating system is configured to increase a concentration of undissolved solids in the water to approximately 0.5 mg/L or greater. 
     
     
         3 . The water treatment system of  claim 1 , wherein the fluid driver is adapted to transfer the flocculated effluent from the outlet of the coagulating and flocculating system to the inlet of the ultrafiltration membrane at a sustained flux rates of at least 250 LMH. 
     
     
         4 . The water treatment system of  claim 1 , wherein the ultrafiltration membrane is a tubular crossflow membrane. 
     
     
         5 . The water treatment system of  claim 4 , wherein the tubular crossflow membrane comprises a plurality of cylindrical tubes defining channels, and wherein the coagulating and flocculating system is fluidly coupled to the channels such that the effluent is directed radially outward through cylindrical tubes. 
     
     
         6 . The water treatment system of  claim 1 , wherein the ultrafiltration membrane is configured to reduce an amount of precipitated phosphorus in the effluent to approximately 0.075 mg/L or less. 
     
     
         7 . The water treatment system of  claim 1 , wherein the fluid driver is adapted to transfer the flocculated effluent across an inner wall of the ultrafiltration membrane at velocities within a range between approximately 0.5 and 5 meters per second. 
     
     
         8 . The water treatment system of  claim 1 , wherein the coagulating and flocculating agent is an aluminum salt, iron salt and/or rare earth metal salt. 
     
     
         9 . The water treatment system of  claim 8 , wherein the coagulating and flocculating agent is at least one of alum, a ferric or ferrous salt, poly aluminum chloride, aluminum chlorohydrate (ACH), or a rare earth material. 
     
     
         10 . The water treatment system of  claim 1 , further comprising one of an intermediate thickening system or a pre-filtration system that is fluidly coupled to the first inlet of the coagulating and flocculating system and configured to separate biodegradable organics from the water. 
     
     
         11 . The water treatment system of  claim 10 , wherein the intermediate thickening system comprises a fluid driver and one of a filtration membrane, a clarifier, or a dissolved air floatation sludge dewatering system. 
     
     
         12 . A method, comprising:
 receiving water;   adding a coagulating and flocculating agent to the water to provide a flocculated effluent comprising precipitated phosphorus solids; and   passing the flocculated effluent through an ultrafiltration membrane at sustained flux rates of at least 150 LMH to separate the precipitated phosphorus solids from the flocculated effluent and to provide a low-phosphorus stream at a first outlet of the ultrafiltration membrane and a high-phosphorus stream at a second outlet of the ultrafiltration membrane.   
     
     
         13 . The method of  claim 12 , further comprising receiving one of a potable water supply or an at least partially treated wastewater, and adding a coagulating and flocculating agent to the water to increase a concentration of undissolved solids in the water to approximately 0.5 mg/L or greater. 
     
     
         14 . The method of  claim 12 , wherein passing the flocculated effluent through the ultrafiltration membrane comprises increasing the concentration of recirculating solids within the membrane to at least 1% total suspended solids. 
     
     
         15 . The method of  claim 12 , wherein the flocculated effluent is passed through the ultrafiltration membrane at sustained flux rates of at least 250 LMH. 
     
     
         16 . The method of  claim 12 , wherein the ultrafiltration membrane is a tubular crossflow membrane, and wherein passing the flocculated effluent through the ultrafiltration membrane comprises passing the flocculated effluent from an inside to an outside of the tubular crossflow membrane. 
     
     
         17 . The method of  claim 12 , further comprising introducing one of an acid or a base to the water via pH control system to adjust the pH of the water to within a range between approximately 5 and 8. 
     
     
         18 . The method of  claim 12 , wherein adding the coagulating and flocculating agent comprises adding one of alum, ferric salt, poly aluminum chloride, ACH, or a rare earth material to the water. 
     
     
         19 . The method of  claim 12 , further comprising passing the water through one of an intermediate thickening system or pre-filtration system to separate biodegradable organics from the water. 
     
     
         20 . The method of  claim 12 , wherein passing the flocculated effluent through the ultrafiltration membrane comprises passing the flocculated effluent across an inner wall of the ultrafiltration membrane at velocities within a range between approximately 0.5 and 5 meters per second.