Patent Publication Number: US-4253958-A

Title: Method of treating polluted aqueous media

Description:
The present invention relates to a method of treating polluted aqueous media, in particular domestic waste water, and municipal and industrial effluent. In the method according to the invention, a lignin sulphonate-containing product is used. The use of this product also falls within the spirit and scope of the present invention. 
     It is well known in this art that many different factors must be taken into account in the purification of domestic waste water, municipal effluent and industrial effluent, these factors rendering the installation and operation of sewage treatment plants extraordinarily complicated. For example, both the chemical and physical compositions of the water which is to be purified must be taken into account. Furthermore, it is necessary during the operation of the sewage treatment plant to check variations in the disclosed composition, as well as in the amount of water which is to be treated. In this context, particular emphasis should be placed on those problems which occur in conjunction with the use of, for example, cleaning agents and solvents which give rise to emulsions. The processes involved in separating, breaking down and eliminating these emulsions result in increased problems for the sewage treatment plants. An increased use of phosphates and metal ions further exacerbates waste disposal problems. A further essential and well-documented disadvantage inherent in sewage treatment plants which are currently in operation is that the water which leaves the treatment plant is unusable as drinking water. 
     The above-presented problems and disadvantages clearly show the need within the art for a method which makes for a simple, effective and high-grade purification of different types of polluted aqueous media. 
     It has now most surprisingly proved that if a polluted aqueous medium is mixed with a product of the type disclosed below, and is subjected to agitation, there will obtained a pure aqueous phase and a flocculated, water-insoluble sludge phase in which substantially all of the pollutant substances in the water are collected. 
     The product with which the aqueous medium is treated according to the present invention may be prepared in that a lignin sulphonate is dissolved in water and mixed with a predetermined amount of a cerium salt. The thus obtained aqueous product of lignin sulphonate and the above-mentioned salt is mixed with aluminium sulphate. A product produced in a similar manner is described in Swedish patent specification No. 7416261-1. This patent specification describes the accelerating effect of the lignin sulphonate product in the biological degradation of hydrocarbons. At the time of inception of the invention described in the above-disclosed patent specification, there were no signs which indicated that the lignin sulphonate preparation could make a contribution in the purification of different types of pulluted aqueous media. Neither was there the slightest hint that the prepation would prove to have superior purification effects. 
     The contents of the different components included in the above disclosed product vary, naturally, in dependence upon the type of medium which is to be treated. Consequently, the optimum composition may be established by testing in each particular case. 
     According to the present invention, use may advantageously be made of a product which is prepared in the following manner: 
     100 g of calcium lignin sulphonate with a standardized iron content of from 0.05 to 0.15% is dissolved in 1 liter of water and mixed, preferably at elevated temperature such as from 50° to 100° C., preferably from 60° to 90° C., to a predetermined amount of cerium salt, such as from 0.5 to 10 g, preferably from 1 to 8 g of ceric sulphate. An amount of from 0.1 to 1.0, preferably from 0.3 to 0.7 cm 3  of this solution is withdrawn and mixed with a suitable amount, such as from 5 to 15, preferably from 8 to 12 cm 3  of a 10 to 30%, preferably 20% aluminium sulphate solution at a temperature ranging from room temperature to approximately 50° C., preferably from 25° to 45° C. 
     According to the present invention, the lignin sulphonate is added in the form of a slurry in water at any optional stage in the purification process. Hence, the actual method of operation according to the invention is very simple. The dosage of the above-described preparation varies in dependence upon the type of water which is to be treated and the concentration of the included pollutants. On this point it might be mentioned that the lignin sulphonate preparation may suitably be conveyed to the site of use in pulverulent form in order, thereafter, to be mixed with water so as to realize a slurry of suitable concentration. The operative solution which is to be added to the waste water may suitably have a product to water concentration ratio of 0.8-1.2:5, preferably 1:5. 
     In order that the treatment according to the invention give the desired result, the aqueous medium which has been admixed with the lignin sulphonate product is subjected to agitation. On this point, both mechanical agitation and air agitation may come into question. At the present time, air agitation is to be preferred because of its clearly improved purification effect. 
     The method according to the present invention is clearly superior to conventional methods for the purification of different types of waste water, since a purified water will be obtained which, in many cases, may directly be used as drinking water. 
     As regards the presence of heavy metals, it should be emphasized that, in conjunction with the flocculation according to the present invention, insoluble complexes of the heavy metals will be obtained and these substances may be easily be removed. 
     Another advantage inherent in the present invention is that, in those methods which are based on purification by activated slurry, the formed slurry amounts may be restricted in that the slurry is broken down because of the accelerating effect on the oxidation process which is realized by utilization of the above-defined lignin sulphonate-containing product. 
    
    
     The invention will be further illustrated by means of the following Examples: 
     100 g of a calcium lignin sulphonate with a standardized iron content of 0.1% was dissolved in 1 liter of water. The solution, heated to 75° C., was mixed with 4.4 g of ceric sulphate under continuous agitation. The thus obtained solution was used as a starting material for the continuation of the experiment. 
     An amount of 0.5 cm 3  of the above-disclosed solution was mixed with 10 cm 3  of an absorptively active 20% aluminium sulphate solution at a maximum temperature of 35° C. The thus obtained product was used in laboratory and field experiments. 
     This product was preferably used for purifying effluent water in sewage treatment plants, the best results being obtained in preliminary experiments (laboratory experiments) in the use of 0.005 vol%, which corresponds to a cerium oxide content of 0.000005 g of cerium oxide/100 cm 3  effluent and, thus, a concentration of from 10 -6  to 10 -7 . 
     The following table shows the results which were obtained in analysis of the water which had been purified according to the present invention. In this case the untreated water consisted of municipal effluent. 
     
                       TABLE                                                       
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1          2       3            4                                         
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pH 8.15    8.1     8.1          8.0                                       
A 0.0025   0.005   0.01         0.03                                      
PO.sub.4 : 0.22                                                           
           0.18    0.6          0.5                                       
BSB.sub.5 : 65                                                            
           14      85           120                                       
Metal ions:                                                               
Traces of less                                                            
           --      Traces of less                                         
                                Traces of lead,                           
than 3 mg          than 4 mg    copper and mer-                           
                                cury                                      
Drop test:                                                                
less than 4 mg                                                            
           --      less than 4 mg                                         
                                far too high alu-                         
                                minium values,                            
                                no typical water                          
                                droplet crystal-                          
                                lization                                  
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 A = content in the effluent water of a working solution of the lignin    
 sulphonate preparation according to the invention (working solution = 1  
 part by weight of active substance slurried in 5 parts by weight of water
                                                                          
 
    
     Examination methods 
     Total determination according to Otto Klee, German unit method 
     PO 4  according to Medinger 
     BSB 5  according to Winkler 
     Drop test according to Schwenk as a supplement to the drop test according to Klee 
     Literature reference 
     Indication of O 2  traces with methylene blue Leukomethylene blue Redox indicators, see Sansoni in &#34;Naturwissen&#34; 1954, p. 213; or colorimetric O 2  determinations in aqueous solution (with O-tolidine), see Freier in &#34;Chemie-Zeitung&#34; 1952, pp. 340-343 and 844-847. 
     For O 2  determination in water 
     O 2  is allowed to react at pH 7.5 with Fe(OH) 2  and the thus formed ferric ions were titrated complexometrically with ethylene diamine tetraacetic acid (Beilstein), Vol. 20; E 1, 6; II. 6; E III, 18. 
     In the following analyses I-IV will be shown the results which were obtained on the treatment and purification of different types of leachate with compounds of the type disclosed in the claims. Particular attention should be paid to the good purification effect as regards heavy metals, for example iron. 
     
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Analyses of untreated sample of bark leachate (Analysis                   
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I)                                                                        
Temperature:        18° C.                                         
pH:                 7.8                                                   
Colour:             Greenish (cloudy)                                     
Smell:              Resin like                                            
                    (terpene derivatives)                                 
Iron:               20 mg/l (ferrous and                                  
                    ferric oxide)                                         
Permanganate consumption:                                                 
                    143.54 mg/l                                           
Phenolic acid:      200 mg/l                                              
Water-soluble substances in                                               
the form of hemicellulose,                                                
pectin, tanning substances                                                
and lignin:         240 mg/l                                              
Spec. conductivity: 9.900 μS/cm                                        
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Analysis of sample precipitated with a working solution                   
(granulate: H.sub.2 O = 1:5) of a compound according to the               
invention                                                                 
(test carried out on filtered aqueous phase)                              
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pH:                 7.1                                                   
Colour:             Pale yellow                                           
Smell:              Resin like                                            
                    (terpene derivatives)                                 
Iron:               1.5 mg/l                                              
Permanganate consumption:                                                 
                    47.51 mg/l                                            
Phenolic acid:      Non-existant                                          
Hemicellulose, pectin, tanning                                            
substances and lignin convert-                                            
ed by precipitation to phloba-                                            
phenes and lignin:  &gt;1/mg/l                                               
Specific conductivity                                                     
                    1.666 μS/cm                                        
The precipitated slurry was water-insoluble (complex-bonded).             
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 Note:                                                                    
 The smell of the filtered aqueous phase disappears by oxidation after    
 about 1 day, the dosage was 1 vol %, flocculation occurred immediately an
 the settling rate was good.                                              
 
    
     
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Analysis of leachate from refuse tip in Harnosand (Analysis               
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II)                                                                       
Untreated sample:                                                         
Test temperature:   20° C.                                         
Colour:             Yellowish, translucent                                
                    with sedimentation                                    
Smell:              Sweetish, perfume smell                               
pH:                 7.2                                                   
Iron:               Total 3 mg/l                                          
Phosphorus:         Total 15 mg/l                                         
Ammonium, NH.sub.4 :                                                      
                    5 mg/l                                                
Nitrates:           25 mg/l                                               
Sulphate:           0 mg/l                                                
Chlorides:          12 mg/l                                               
Organic substances: 52 mg/l                                               
Animal and vegetable                                                      
fatty substances:   80 mg/l                                               
Metal ions:         9 mg/l (Lead approx. 6                                
                    mg/l, traces of                                       
                    cadmium)                                              
                    Tests for copper,                                     
                    zinc and mercury                                      
                    were negative.                                        
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Sample precipitated with a working solution (granulate:                   
H.sub.2 O = 1:5) of a compound according to the present                   
______________________________________                                    
invention                                                                 
Test temperature:   20° C.                                         
Dosage:             0.2 vol % (100 ml sample)                             
                    dosed with 0.2 ml of                                  
                    the compound                                          
Flocculation:       Immediate                                             
Settling rate:      85% within 5 min                                      
Aqueous phase:      pH 6.2                                                
Colour:             Crystal clear with some,                              
                    slight floating floc                                  
Test on filtered aqueous phase:                                           
Iron:               0 mg/l                                                
Phosphorus:         Total 0 mg/l                                          
Ammonium NH.sub.4 : Unchanged 5 mg/l                                      
Nitrates:           0 mg/l                                                
Sulphate:           20 mg/l (Aluminium sul-                               
                    phate occurred as a re-                               
                    sult of overdosing)                                   
Chlorides:          12 mg/l                                               
Organic substances: 0 mg/l                                                
Animal and vegetable fatty                                                
substances:         0 mg/l                                                
Metal ions:         0                                                     
Smell:              Perfume-like                                          
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 Analysis of leachate from rubbish tip (Analysis III)                     
Examination results:                                                      
Sample              1         2                                           
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Lead, Pb       mg/l     &lt;0.10     &lt;0.10                                   
Cadmium, Cd    &#34;        &lt;0.02     &lt;0.02                                   
Cobalt, Co     &#34;        &lt;0.05     &lt;0.05                                   
Copper, Cu     &#34;         0.06      0.05                                   
Chromium, Cr   &#34;        &lt;0.05     &lt;0.05                                   
Nickel, Ni     &#34;         0.25      0.12                                   
Zinc, Zn       &#34;         0.84      0.20                                   
Mercury, Hg    μg/l  &lt;0.10     &lt;0.10                                   
Arsenic, As                                                               
Beryllium, Be                                                             
The precipitation agent is a 0.4% solution of a compound                  
according to the invention.                                               
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  1 Leachate rubbish tip prior to precipitation                           
  2 Leachate rubbish tip after precipitation with a compound according to 
 the invention.                                                           
 
    
     
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Analysis of leachate (Analysis IV)                                        
                     sample treated with a                                
                     compound according to                                
         untreated sample                                                 
                     the invention                                        
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pH             6.9           6.4                                          
Fe    mg/l     28            0.42                                         
Mn    &#34;        1.2           1.2                                          
Zn    &#34;        0.06          0.03                                         
Pb    &#34;        &lt;0.1          &lt;0.1                                         
Cd    &#34;        &lt;0.02         &lt;0.02                                        
Cu    &#34;        &lt;0.04         &lt;0.04                                        
COD   &#34;        180           140                                          
BOD.sub.7                                                                 
      &#34;        61            45                                           
SO.sub.4                                                                  
      &#34;        14            11                                           
C1    &#34;        114           115                                          
F     &#34;        ˜0.1    ˜0.1                                   
NH.sub.4 -N                                                               
      &#34;        50            52                                           
Kj-N  &#34;        74            70                                           
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 Note:                                                                    
 The samples were too small for determining other nutrient salts.