Method of monitoring treating agent residuals and controlling treating agent dosage in water treatment processes

Abstract

Methods of monitoring residual treating agent in treated water wherein the fluorescence intensity of the water at at least two different dosages of treating agent tagged or traced with fluorescent tracers are correlated with the residual concentration of treating agent. The fluorescence response at the different treating agent dosages is also used to automatically determine an optimal treating agent dose on a continuous basis and to control treating agent dose accordingly.

1 . A method of monitoring residual treating agent and determining optimal treating agent dosage in process water treated with the treating agent comprising sequentially 
 i) adding a first dose of the treating agent traced or tagged with a fluorescent tracer to the process water,    ii) measuring the fluorescence intensity of the process water,    iii) adding a second dose of the treating agent traced or tagged with the fluorescent tracer the process water;    iv) measuring the fluorescence intensity of the process water; and    v-a) correlating the change in measured fluorescence intensity of the process water at the first and second treating agent doses to the residual concentration of the treating agent; or    v-b) correlating the change in the measured fluorescence intensity of the process water at the first and second treating agent doses with a non-proportional change in measured fluorescence intensity, wherein the non-proportional change in measured fluorescence intensity of the process water is used to determine a set point corresponding to the optimal treating agent dosage.    
     
     
         2 . The method of  claim 1  wherein the residual concentration of the treating agent is correlated with the change in measured fluorescence intensity of the process water at the respective treating agent doses using a function of the difference between molecules of fluorescent tracer added to the process water and molecules of fluorescent tracer detected in the process water.  
     
     
         3 . The method of  claim 1  wherein the residual concentration of the treating agent is correlated with the change in measured fluorescence intensity of the process water at the respective treating agent doses using a function of the difference between the fluorescence quenching expected and the fluorescence quenching detected.  
     
     
         4 . The method of  claim 1  wherein the residual concentration of the treating agent is correlated with treating agent dosage.  
     
     
         5 . The method of  claim 1  wherein the residual concentration of the treating agent is used to determine an upper limit of treating agent dosage.  
     
     
         6 . The method of  claim 5  wherein the treating agent dosage is automatically maintained below the upper limit.  
     
     
         7 . The method of  claim 1  wherein the set point is automatically changed to account for fluctuations in the process water quality.  
     
     
         8 . The method of  claim 2  wherein the treating agent dosage is automatically maintained at the set point.  
     
     
         9 . The method of  claim 1  wherein the treating agent is tagged with a fluorescent tracer.  
     
     
         10 . The method of  claim 1  wherein the treating agent is traced with a fluorescent tracer.  
     
     
         11 . The method of  claim 1  wherein the water treatment process is a solid-liquid separation process.  
     
     
         12 . The method of  claim 11  wherein the solid-liquid separation process comprises treatment of the water with one or more coagulants or flocculants, or a combination thereof, to form a mixture of water and coagulated and flocculated solids and separation of the coagulated and flocculated solids from the water.  
     
     
         13 . The method of  claim 12  wherein the solid-liquid separation process is a membrane separation process wherein the coagulated and flocculated solids are separated from the water by filtration through a membrane.  
     
     
         14 . The method of  claim 13  wherein the membrane separation process is a reverse osmosis pretreatment program wherein the water is treated with one or more filter aids to form a mixture of coagulated and flocculated solids and at least a portion of the coagulated and flocculated solids are removed from the water prior to filtration of the water through a reverse osmosis membrane.  
     
     
         15 . The method of  claim 13  wherein the portion of coagulated and flocculated solids is removed from the water by filtration through a media filter.  
     
     
         16 . The method of  claim 13  wherein the filter aid is one or more coagulants selected from alum, polyaluminum chloride, ferric chloride, ferric sulfate, poly(diallyldimethylammonium chloride) and Epi-DMA.  
     
     
         17 . The method of  claim 13  wherein the fluorescent tracer is selected from fluorescein, rhodamine B, and rhodamine WT.  
     
     
         18 . The method of  claim 13  wherein the filter aid tagged with a fluorescent tracer is poly(diallyldimethylammonium chloride) tagged with luminol, rhodamine or fluorescein.