Method of Raising the pH of Acidic Bodies of Water

Abstract

The invention relates to a method of raising the pH of a body of water having a pH of less than 4.5 by introducing neutralizing agent, the raising of the pH taking place in at least two stages thus: at pH levels below 4.5, a first neutralizing agent having a final conductivity of not more than 100 .mu.S/cm, and, after attainment of a pH of at least 4.5, a second neutralizing agent, having a final conductivity of more than 100 .mu.S/cm, is introduced into the body of water, the final conductivity of the neutralizing agents being defined as the conductivity of an aqueous suspension or solution of neutralizing agent in solution equilibrium at 25.degree. C., having a neutralizing agent content of 0.015% by weight.

The invention claimed is: 
     
         1 . A method for raising the pH of a body of water, wherein said body of water has a pH of less than 4.5 comprising introducing a neutralising agent, such that raising the pH takes place in at least two stages; wherein at pH values of less than 4.5, a first neutralising agent with a final conductivity of at most 100 μS/cm is introduced into the water and, after the body of water reaches a pH of at least 4.5, a second neutralising agent comprising materials originating from lime with a final conductivity of more than 100 μS/cm is introduced into the body of water, wherein the final conductivity of the neutralising agents being determined as the conductivity of an aqueous neutralising agent suspension or solution in solution equilibrium at 25° C. with a neutralising agent content of 0.015% by weight introduced into the body of water at pH values of less than 4.5 as a suspension at a concentration of 2 to 15% by weight and, when the pH values are at least 4.5, said neutralising agent is introduced into the body of water as a suspension at a concentration of 0.05 to 2% by weight. 
     
     
         2 . The method according to  claim 1 , wherein the pH of a body of water with a water volume of more than 500,000 m 3  is raised. 
     
     
         3 . The method according to  claim 2 , wherein the pH of the body of water is raised to a value of at least 5, preferably to at least 6. 
     
     
         4 . The method according to  claim 3 , wherein the method is carried out as an in-lake method. 
     
     
         5 . The method according to  claim 4 , wherein the neutralising agent is introduced as a suspension into the body of water. 
     
     
         6 . The method according to  claim 5 , wherein the materials originate from lime, preferably chalk, lime, limestone slurry, carbokalk, half-burnt dolomite, and/or dolomite rock meal, are used as the neutralising agent with a final conductivity of at most 100 μS/cm. 
     
     
         7 . The method according to  claim 6 , wherein burnt lime, lime hydrate, slaked burnt lime, dolomite burnt lime and/or dolomite lime hydrate is used as the neutralising agent with a final conductivity of more than 100 μS/cm. 
     
     
         8 . The method according to  claim 7 , wherein at pH values of the body of water of less than 4.5, a neutralising agent is used with a solution affinity, measured as the sulphuric acid consumption in a pH stationary titration of 0.5 g neutralising agent in 100 ml deionised water at 20° C., by means of 0.5 mol/l sulphuric acid at a pH of 6 and for a period of 30 minutes, of less than 6.5 ml, preferably of less than 5 ml and, in particular, of less than 2 ml. 
     
     
         9 . The method according to  claim 8 , wherein at pH values of the body of water of at least 4.5, a neutralising agent is used with a solution affinity, measured as the sulphuric acid consumption in a pH stationary titration of 0.5 g neutralising agent in 100 ml deionised water at 20° C., by means of 0.5 mol/l sulphuric acid at a pH of 6 and for a period of 30 minutes, of more than 6.5 ml, preferably of more than 8 ml and, in particular, of more than 10 ml. 
     
     
         10 . The method according to  claim 9 , wherein at pH values of the body of water of less than 4.5, materials originating from lime with a particle size distribution D50 of at least 7.4 μm, preferably of more than 9 μm, and in particular of more than 11 μm, are used. 
     
     
         11 . The method according to  claim 10 , wherein at pH values of the body of water of at least 4.5, materials originating from lime with a particle size distribution D50 of less than 7.4 μm, preferably of less than 5 μm, and in particular of less than 3 μm are used. 
     
     
         12 . The method according to  claim 1 , wherein the pH of the body of water is raised to a value of at least 5, preferably to at least 6. 
     
     
         13 . The method according to  claim 1 , wherein the method is carried out as an in-lake method. 
     
     
         14 . The method according to  claim 1 , wherein the neutralising agent is introduced a suspension into the body of water. 
     
     
         15 . The method according to  claim 1 , wherein the materials originate from lime, preferably chalk, lime, limestone slurry, carbokalk, half-burnt dolomite, and/or dolomite rock meal, are used as the neutralising agent with a final conductivity of at most 100 μS/cm. 
     
     
         16 . The method according to  claim 1 , wherein burnt lime, lime hydrate, slaked burnt lime, dolomite burnt lime and/or dolomite lime hydrate is used as the neutralising agent with a final conductivity of more than 100 μS/cm. 
     
     
         17 . The method according to  claim 1 , wherein at pH values of the body of water of less than 4.5, a neutralising agent is used with a solution affinity, measured as the sulphuric acid consumption in a pH stationary titration of 0.5 g neutralising agent in 100 ml deionised water at 20° C., by means of 0.5 mol/l sulphuric acid at a pH of 6 and for a period of 30 minutes, of less than 6.5 ml, preferably of less than 5 ml and, in particular, of less than 2 ml. 
     
     
         18 . The method according to  claim 1 , wherein at pH values of the body of water of at least 4.5, a neutralising agent is used with a solution affinity, measured as the sulphuric acid consumption in a pH stationary titration of 0.5 g neutralising agent in 100 ml deionised water at 20° C., by means of 0.5 mol/l sulphuric, acid at a pH of 6 and for a period of 30 minutes, of more than 6.5 ml, preferably of more than 8 ml and, in particular, of more than 10 ml. 
     
     
         19 . The method according to  claim 1 , wherein at pH values of the body of water of less than 4.5, materials originating from lime with a particle size distribution D50 of at least 7.4 μm, preferably of more than 9 μm, and in particular of more than 11 μm, are used. 
     
     
         20 . The method according to  claim 1 , wherein at pH values of the body of water of at least 4.5, materials originating from lime with a particle size distribution D50 of less than 7.4 μm, preferably of less than 5 μm, and in particular of less than 3 μm are used.