Abstract:
A wastewater treatment process, and related computer program, where wastewater processing decisions are to be taken based on the real-time oxidation-reduction potential (ORP) of the wastewater. ORP is a broad-ranged index and effectively indicates the biological status of water. A computer software program appropriately adds chemicals and controls aeration based on the real-time status of ORP.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims priority based on U.S. patent application Ser. No. 10/421,916, now issued as U.S. Pat. No. 7,141,175, which, in turn, claimed priority from Provisional Patent Application 60/375,525 filed Apr. 25, 2002. The disclosures of these priority documents is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a process for efficiently treating wastewater, based on the oxidation-reduction potential of water followed by need-based chemical treatment guided by knowledge of chemistry of one or more chemicals to be added at an appropriately selected oxidation-reduction potential. The present invention also relates to a computer program for monitoring and automatically controlling such wastewater treatment.  
       BACKGROUND OF THE INVENTION  
       [0003]     Most existing wastewater facilities are designed to collect all the influents in a preliminary treatment area, where large debris and solids are screened out of the wastewater. The remaining water is allowed to pass through a primary treatment area where it is subjected to chemical treatments (for example, addition of ferrous chloride for phosphate removal and some polymers to facilitate floc formation). The water is then mixed with a bacterial biomass, and passes through an aeration phase. The movement of water is then slowed down in large tanks called secondary clarifiers to allow settling of sludge, and the decanted water is subsequently disinfected by various means.  
         [0004]     Wastewater treatment decisions currently are mainly based on parameters like pH, Dissolved Oxygen (DO), Biological Oxygen Demand (BOD) etc which are, in fact, contributing partners to a single and superior parameter called Oxidation-Reduction Potential (ORP), which has not been understood and exploited properly. Moreover, the former parameters have a narrow range and do not clearly reveal the precise biological status of the water.  
       REFERENCES  
       [0000]    
       
          1) Daniel O., and F. James, Practical Engineering combined with sound operations optimize phosphorus removal. Water Engineering Mgt., April 2002, p 22-27  
          2) Khalil Atasi, Fate and Effects of Iron and Heavy Metals on the Activated Sludge Process, A Process Engineering Literature Review prepared for the Iron Assessment Project Committee, August 1985.  
       
     
       SUMMARY OF THE INVENTION  
       [0007]     The efforts of the present inventor provide the first attempt to highlight the potential commercial importance of Oxidation-Reduction Potential (ORP). So far, ORP has been measured as a routine, and decisions have been made based on operators&#39; past experience and ‘gut feeling’ without involving any scientific logic. ORP can be logically incorporated into processing decisions thereby sensibly saving money. This patent teaches that the wastewater processing decisions, especially the chemical additions and oxygenation, be based on observation and interpretation of ORP values on a daily basis.  
         [0008]     More specifically, this invention relates to a process where wastewater treatment or processing decisions, like what, when, where and how much of chemicals, oxygen, air or other ingredients are to be added, are made after assessing oxidation-reduction potential status of water at the point of use. Its understanding not only provides an important guide for managing any biological system (including the human body), but also can be used as a resource management tool for processes like wastewater treatment, where it can bring about significant procedural improvements with real cost savings.  
         [0009]     A computer-software program can also be prepared, according to the present invention, to manage the input of wastewater resources based on real time status of ORP.  
         [0010]     Specifically, Oxidation-Reduction Potential (ORP) is a measure of accumulation or deficiency of charged molecules, particularly electrons, in the biological system. In simple words, it is a measure of electron pressure (or concentration) in a solution or system. During microbial metabolism, electrons are produced, which must preferably be removed by oxygen to produce energy by a process called oxidative-phosphorylation. In an absence of oxygen, these electrons accumulate or react with other ions to impart a negative charge, resulting in a negative ORP, measured in millivolts (mV). Thus, a negative ORP is a clear indication that the system is anaerobic, and needs oxygen on a priority basis rather than any other chemical.  
         [0011]      FIG. 1  shows a schematic overview of a wastewater treatment facility operating with ORP based management of wastewater treatment, in which numeral  50  represents an ORP based FeCl 3  release mechanism including online flow meter, phosphate analyzer, ORP measuring probe, FeCl 3  releasing mechanism, and related computer software/hardware, linked to a central data control room; and numeral  60  represents ORP based cationic chemical or polymer release mechanism including online flow meter, ORP measuring probe and polymer release mechanism and related computer software/hardware, linked to a central data control room.  
         [0012]     It is an object of the present invention to highlight the commercial importance of ORP and its use in decisions for cost efficient processing of wastewater. A computer software program is also proposed, according to the present invention, to manage the resources in the wastewater treatment plant, based mainly on in-line ORP measurements at various points. It is also proposed to precondition the influents by mixing the unprocessed wastewater with high ORP water, such as water from a spring, fountain or mountainous stream, followed by a well-calculated addition of chemical to achieve the desired objective. This could conceivably lead to serious cost savings.  
         [0013]     For a more complete understanding of the present invention, the reader is referred to the following detailed description section, which should be read in conjunction with the accompanying drawings. Throughout the following detailed description and in the drawings, like numbers refer to like parts. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is an overview of ORP based management of wastewater treatment.  
         [0015]      FIG. 2  is a flowchart showing steps involved in wastewater treatment.  
     
    
     DETAILED DESCRIPTION  
       [0016]     Specifically, Oxidation-Reduction Potential (ORP) is a measure of accumulation or deficiency of charged molecules, particularly electrons, in the biological system. In simple words, it is a measure of electron pressure (or concentration) in a solution or system. During microbial metabolism, electrons are produced, which must preferably be removed by oxygen to produce energy by a process called oxidative-phosphorylation. In an absence of oxygen, these electrons accumulate or react with other ions to impart a negative charge, resulting in a negative ORP, measured in millivolts (mV). Thus, a negative ORP is a clear indication that the system is anaerobic, and needs oxygen on a priority basis rather than any other chemical.  
         [0017]     Every molecule, has specific ORP (pK ORP , a new term designed by the present inventor), around which it exists in different forms in differing proportions. For example, iron is 50% ferrous and 50% ferric at an ORP of approximately +120 mV (i.e. the pK.sub.ORP iron is +120 mV). Above +120 mV, ferric ion is in dominating proportion.  
         [0018]     The effectiveness of a molecule, therefore, will much depend upon ORP status of the solution to which it is being added. In other words, if ORP is not appropriate, the treatment may not only be ineffective, but may cause adverse effects. Similarly, the use of an anionic polymer at the negative ORP to obtain polymerization, would be ineffective.  
         [0019]     In addition to the information provided above and based on the laboratory observations laid out in tables below, the ORP values change with time and weather conditions of the day. Influents to a wastewater facility are usually in the negative range in summer and sunny days presumably due to relatively high metabolic activity as compared to amount of oxygenation of influents. ORP of influent sewage is generally positive during winter months, cold as well as wet weather and few days thereafter, presumably be due to lesser metabolic activity during winter months and/or significantly higher oxygenation of water due to rain, fog or snowfall.  
         [0020]     Addition of any negatively charged chemical or any chemical capable of releasing electron at a negative ORP would be ineffective till the ORP rises to a desired level. For example, an ORP of +120 mV is necessary to assure maximum benefit of any iron salt to be added with an aim of reducing phosphate concentration in wastewater.  
         [0021]     These facts can be better interpreted if explained with an example from Detroit Wastewater Treatment Plant (DWWTP).  
         [0022]     During the period between January-June 2000, the plant had numerous problems like high Settled Volume Index (SVI) and low sludge thickening. The present inventor found that Pickle liquor (ferrous chloride) had been constantly added to the primary influents to the extent of 10 ppm, with an idea of reducing the phosphate levels in the final effluent.  
         [0023]     According to the present inventor, not only is the approach discussed in the previous paragraph wrong, but also such a high dose is toxic to microbes ( 2 ), thereby killing the microbes and resulting in a high amount of ‘chemical sludge’. The operators and the management thought that this way they are cleaning the water faster. The influent to DWWTP had shown negative ORP (avg. −180 mV) for a significant number of days in that period. Pickle liquor (3 ppm) further lowers the ORP by 80 mV.  
         [0024]     The addition of ferrous salts under such conditions would be of little value because a significant proportion of iron will continue to exist as ferrous and results in carryover of soluble ferrous phosphate to the secondary system.  
         [0025]     Even if the ferrous chloride is added after the sewage attained an ORP of +120 mV, the final ORP would be around +40 mV, where only negligible portion of it would be converted to ferric to form insoluble ferric phosphate. Therefore, when pickle liquor is added, more time and work is needed to bring the water back to the desired +120 mV ORP range.  
         [0026]     Additionally, since ferrous ions are ready to release the extra electron on them, it adds to the electron pressure (i.e. lesser ORP and higher chemical oxygen demand). It takes us away from proper conditions for floc formation, as there is more dispersal due to additional excessive charge. This was the cause of high SVIs and low sludge thickening.  
         [0027]     On the other hand, 3 ppm of ferric chloride raises the ORP by 30 mV. If ferric chloride is added after the waters have attained nearly +90 mV (possible mostly in the aeration basins), the resultant ORP would be near +120 mV, where almost 50% of the iron added to the sewage will remain as Ferric and insoluble ferric phosphate is formed. Therefore, it is easy to calculate how much iron compound should be added, just to remove the excess phosphate.  
         [0028]     As water moves ahead, the ORP rises itself, more and more ferric is formed and the phosphate is complexed and gets settled in secondary clarifiers. In this approach, lesser oxygenation (up to +90 mV only) and significantly less iron salts are needed, without violating any permit or causing any side effects.  
         [0029]     The laboratory data indicates that aeration first followed by ORP based ferric chloride addition results in more phosphate removal with significantly lower dose of iron salt needed. One plant has shown significant cost savings with better phosphorus removal by shifting the point of addition of ferric chloride from primary treatment to a location in aeration basin of the activated sludge (without any knowledge or mention of ORP (1).  
         [0030]     Iron salts, as being added currently to the primary influents with a wrong notion of removing phosphate, have historically lead to a number of problems at DWWTP like high Settled Volume Index (SVI)s and low sludge thickening. There appears to be clear and manageable relationship between mixed liquor suspended solids, oxidation-reduction potential of influents, type of iron salt and point of its addition.  
         [0031]     If managed properly, NPDES permissible limits of phosphate levels in effluent can be met at least cost. This patent is the first attempt to highlight the importance of ORP in general and its use in making the processing decisions based on the continuous monitoring of the Oxidation-Reduction Potential (ORP) status of wastewater as this is the proper and economic way of managing this business.  
         [0032]     Tests indicate that if three waters having different ORPs are mixed in equal ratio, the final ORP is that of the water with higher value. That means if the wastewater influent streams in any plant are mixed and then merged with a water of Higher ORP, the resultant ORP would be of that of the water added later. This would precondition the wastewater sufficiently for processing at significant savings of resources, time and money.  
         [0033]     3 ppm of Pickle liquor (ferrous chloride) lowers the ORP by about −80 mV, taking us away from the target. Its use at negative ORP values is simply illogical in primary sedimentation as it increases the amount of work needed to bring the wastewater to the previous state.  
         [0034]     Ferric chloride (3 ppm) raises ORP by about +30 mV.  
         [0035]     Aeration (10 psi, 45 min) raises ORP by about +200 mV. Aeration alone, in other words, helps us reach the target value of +120 mV. If this is followed by a calculated amount of ferric chloride, phosphate removal can be effective and economical.  
         [0036]     When Fecl3 is added after aeration, there is at least 26% more reduction in soluble phosphate and 26% additional reduction in turbidity.  
         [0037]     When Pickle liquor (ferrous chloride) is added before or after aeration, there is relatively lesser reduction in soluble phosphate and practically no reduction in turbidity, because the gains in ORP due to aeration are negated by ferrous chloride.  
         [0038]     Based on the current information, the aeration of sewage to at least +90 mV followed by addition of ferric chloride and polymer, will reduce iron requirement and will afford better effluent with lesser phosphate. However, on many days, depending on the type of influent, it may not be possible to reach +90 mV. Practically, to maximize the effective use of resources, an ORP of at least +50 mV must be achieved before adding any chemical.  
         [0039]     According to this observations, some design changes can be proposed. For example, there should be at least three ports in each aeration basin where FeCl3 can be released. The nearest FeCl3 port where ORP has reached at least +50 mV, be opened and the dosage just sufficient to neutralize the soluble phosphates in excess of NPDES allowable limits, be added. The resulting insoluble ferric phosphate will settle later in secondary clarifiers.  
         [0040]     This way, not only an optimum amount of chemicals are used, but also regulatory requirements are met without contaminating the final product.  
         [0041]     There are several ways to increase the ORP value or neutralize the charge of water, few of them being:  
         [0042]     i) aeration,  
         [0043]     ii) acidification,  
         [0044]     iii) induction of conditions to cause ion exchange with microorganisms, where microorganisms absorb electrons or negatively charged molecules and/or release positively charged molecules,  
         [0045]     iv) addition of adsobants of electron or negatively charged molecules and the like.  
         [0046]     The terms oxidation-reduction potential and zeta potential have overlapping meanings depending upon the situation. For wastewater when one raises the ORP, one is also simultaneously changing the zeta potential. Since the flocs start forming near zero zeta potential, the expression of optimizing or raising ORP may also be considered as optimizing or raising the zeta potential of wastewater.  
         [0000]     Supporting Data  
         [0047]     Now I present empirical laboratory data to support the above discussion:  
         [0048]     Table I shows that the ORP of the plant influents samples collected for March 30-April 26 were positive for 40% of the time during the cold months. During the warmer months of June and July the plant influents ORP is always negative. Of note is the increase in ORP values of the sewage as the sewage flows thorough the treatment process.  
         [0049]     These seasonal changes must be factored-in while considering aeration as well as chemical addition, because during cold as well as after wet weather lesser aeration and less chemical treatment would be needed. On the other hand, more emphasis should be put on aeration of influent sewage during sunny and hot weather to adjust ORP to a suitable level.  
                                                                                                             TABLE 1                       PLANT DATA AND ORP VALUES AT VARIOUS POINTS AT DWWTP                                                        Primary   Secondary                   Ambient               Feed site   influent   effluent           Air       Precipitation   Feed =   pickel highs   sol. P   sol. P   P   Total Plant       Date   Temp. F.   Weather   (inches)   Fe++/Fe+++   (ppm)   (ppm)   (ppm)   removed %   inflow (mgd)               Mar. 30, 2000   41   Part cloudy   0   Fe++   2.9   1.2   0.28   76.7   525       Apr. 19, 2000   35   Cloudy   0   Fe++   2.8   1.0   0.15   85.0   615       Apr. 13, 2000   44   Sunny   0   Fe++   2.9   1.0   0.20   80.0   576       Apr. 24, 2000   57   Sunny (4 d after rain)   0   Fe++   2.8   0.3   0.05   83.3   797       Apr. 26, 2000   60   Sunny   0   Fe++   2.9   0.8   0.09   88.8   695       Jun. 10, 2000   64   Sunny   0   Fe++   1.9   0.8   0.22   72.5   596       Jun. 16, 2000   67   Sunny (3 d after rain)   0   Fe++   2.0   1.0   0.27   73.0   598       Jun. 26, 2000   72   Sunny (1 d after rain)   0   Fe++   2.2   0.2   0.05   75.0   1261       Jun. 29, 2000   78   Part cloudy   0   Fe++   2.0   0.7   0.44   37.1   684       Jul. 06, 2000   72   Part cloudy   0   Fe++   1.9   0.8   0.24   70.0   726       Jul. 07, 2000   74   Clear sunny   0   Fe++   2.8   0.6   0.20   66.7   680       Jul. 11, 2000   67   Clear sunny   0   Fe++   1.9   0.8   0.20   75.0   663       Jul. 13, 2000   76   Part cloudy   0   Fe++   2.0   1.0   0.20   80.0   573                        ORP Values                                PS2A, 500 ft                                       Away from           Jeff.   Oak.   NIEA   mixing point   PEAS 1   C2E3   C2E4   Tap water               Mar. 30, 2000            190   205   165           Apr. 19, 2000             −116     74   17       Apr. 13, 2000             −81     65   22   144   152   452       Apr. 24, 2000            110   119   107   152   149   444       Apr. 26, 2000             −112     136   48       Jun. 10, 2000             −115         Jun. 16, 2000     −158       −155       −152         Jun. 26, 2000     −48       −22       −113         Jun. 09, 2000     −118       −116       −123         10       Jul. 06, 2000     −173       −105       −170           −12         Jul. 07, 2000     −63       −191       −201         21   65       Jul. 11, 2000         −90       −157         62       Jul. 13, 2000     −140       −137       −174     102   14       Average ORP −&gt;   −117   −117    −93.4                 Negative ORPs are shown in bold             
 
         [0050]     Table 2 confirms that aeration alone raises the ORP of influent sewage by about 195.+/−.29 units, depending upon quality of the influent each day.  
                                                                     TABLE 2                           Effect of Aeration on ORP            Date of   Initial   Aeration   Final   Change in       Experiment   ORP (mV)   time 10 psi   ORP (mV)   ORP (mV)                    Sep. 03, 2000   −185.4   30 min   37.7   223.1       Sep. 07, 2000   −187   15 min   15.0   202       Oct. 31, 2000   −186.3   30 min   22.7   209       Nov. 02, 2000   −164.5   45 min   19.5   184       Nov. 09, 2000   −192.1   45 min   45.2   237.3       Jan. 15, 2002   −7.2   15 min   133.5   140.7       Jan. 18, 2002   −122.6   15 min   75.9   198.5       Jan. 24, 2002   −136.1   15 min   33.3   169.4       Feb. 08, 2002   −110.1   15 min   77.0   187.1            Average change in ORP   194.6       Standard Deviation →   28.8                  
 
         [0051]     Table 3 indicates that:  
         [0052]     a) When waters with different ORP values are combined in equal ratio, the final ORP is equal to that of having highest value. This fact is of high commercial value.  
         [0053]     b) Just as protons are added through acidification, the electron concentration is reduced and ORP rises. This proves that it is mainly the electron concentration that is indicative of ORP status of water. The rise in pH due to aeration is unique and has not been described in literature and as such cannot be explained at this time.  
         [0054]     c) The pH of influents was around 7.4 and the ORP is negative. As per our experience, nothing should happen if iron and polymers are added at this stage. It appeared that attainment of an optimum ORP is essential to wastewater processing as the turbidity (NTU) got lowered only when ferric chloride and polymer were added near +122 mV. This confirms that decisions based solely on pH may not yield the desired results.  
                                                   TABLE 3                           THE EFFECT OF COMBING SAMPLES, AERATION       &amp; POLYMER ADDITION ON pH AND ORP                ORP   pH   NTU                        OAKWOOD INFLUENT   −157.5   7.45   NA       JEFFERSON INFLUENT   −186.1   7.20   NA       OAKWOOD + JEFF 1:1   −158.0   7.44   NA       NIEA INFLUENT   −192.1   7.34   NA       ORP AFTER COMBINING OAKWOOD,   −155.2   7.44   49.0       JEFFERSON, &amp; NIEA 1:1:1       AFTER AERATION 45 MINUTES, 10 psi   45.2   8.63   45.9       AFTER POLYMER 250 ul   45.2   8.63   NA       AFTER POLYMER, additional 250 ul   45.0   8.63   43.5       10% HCl to pH 7.00 (1100 ul was needed)   122.7   7.00   44.0       Fe+++ 50 ul   118.3   NA   50.0       PS2A, polymer, additional 250 ul   105.7   NA   18.3                  
 
         [0055]     Table 4 indicates that limited aeration is better than excessive turbulence. Too much aeration might worsen the quality of effluent. Also it shows that excessive ferric chloride is of no additional use.  
                                                                                     TABLE 4                           EXPERIMENT TO SEE HOW MUCH AERATION IS REQUIRED       Dated Sept. 03, 2000                These three were additionally blended at high speed for 1 min                    Beaker 2   Beaker 3   Beaker 4   Beaker 5   Beaker 6           Beaker 1   Aerated 30 min 10 psi   Aerated 30 min 10 psi   Aerated 30 min 10 psi   Aerated 30 min 10 psi   Aerated 30 min 10 psi           Raw Sample   FeCl3 300 μl   FeCl3 150 μl   none   FeCl3 100 μl   FeCl3 150 μl           Undisturbed   PS2A Polymer 250 μl   PS2A Polymer 250 μl   none   PS2A Polymer 250 μl   PS2A Polymer 250 μl                        ORP (mV)   −156.5   −43.1   −47   23   67.3   36.2       Turbidity   83.5   6.7   6.5   109*   18.7*   41.4*                 *The turbidity is high after blending probably due to the microbubbling during high turbulence of the blender. An impractical situation             
 
         [0056]     Tables 4 and 5 show that there is significant rise in ORP by aeration alone. In this sample, only the ferric chloride and polymer addition was enough to get an effluent with a low turbidity (Beaker 1.2 &amp; 3). This is, however, not always true, as effluents on some days will not yield at all (see Table 6). This experiment also indicates that, aerate or not, the excessive amount of ferric has a non-significant effect on ORP or turbidity.  
                                                                           TABLE 5                           EXPERIMENT TO SEE IF AERATION FIRST IS REALLY BENEFICIAL       Sept. 07, 2000                    Beaker 2   Beaker 3   Beaker 4   Beaker 5   Beaker 6               Raw Sample   Raw Sample   Aerated 15 min   Aerated 15 min   Aerated 15 min           Beaker 1   FeCl3 50 μl   FeCl3 100 μl   none   FeCl3 50 μl   FeCl3 100 μl           Raw Sample   PS2A Polymer 250 μl   PS2A Polymer 250 μl   none   PS2A Polymer 250 μl   PS2A Polymer 250 μl                        ORP   −187   −131   −110   15   32   42       Turbidity   95   24.5   13.7   85   23.5   11.4                 Phosphates were not studied             
 
         [0057]     Tables 2, 4, 5, 6, 7, 8 &amp; 9 establish that the aeration alone raises the ORP sufficiently enough to prepare conditions for ferric chloride to work.  
                                                                           TABLE 6                           THE EFFECT OF AERATION FIRST ON PHOSPHATES       Jan. 15. 2002                Beaker 1   Beaker 2   Beaker 3                       Raw sample   Raw sample   Raw sample   Beaker 4   Beaker 5   Beaker 6           Undisturbed   Undisturbed   Undisturbed   Aerated 15 min   Aerated 15 mm   Aerated 15 min           none   FeCl3 50 μl   FeCl3 100 μl   none   FeCl3 50 μl   FeCl3 100 μl       Chemical addition   Wait 5 min   Wait 5 min   Wait 5 min   Wait 5 min   Wait 5 min   Wait 5 min                    ORP (mV)   −7.7   26.5   ND*   ND   133.5   ND       Turbidity   96.5   95.2   ND   ND   93.5   ND       Total P   0.12   0.06   ND   ND   0.04   ND                 The starting ORP was already high as expected because the sample was not brought air tight.            ND* = Not determined, because the sample was highly colloidal and no physical change was observable.             
 
         [0058]     Table 7 represents a sample where phosphates were lowered just by addition of ferric chloride and that aeration after this has a cumulative effect and phosphates are lowered further. This supports the hypothesis that given a fixed iron dose, more ferric ions are made available as a result of increase in ORP. In the non-aerated samples, ORP is raised just by addition of ferric salts.  
                                                                   TABLE 7                           ROLE OF FERIC CHLORIDE, WITH OR WITHOUT AERATION       Jan. 18, 2002                Beaker 1   Beaker 2   Beaker 3                   none   FeCl3 50 μl   FeCl3 100 μl   Beaker 4   Beater 5       Chemical addition   Raw sample   Raw sample   Raw sample   FeCl3 50 μl   FeCl3 100 μl       Action   Undisturbed   Undisturbed   Undisturbed   Aerated 15 min   Aerated 15 mm       ORP = −122.6 mV   Wail 10 min   Wait 10 min   Walt 10 min   Wait 10 min   Wail 10 min                    ORF   −117.3   −82   38.5   75.9   91.8       Sol. P (Avg. of 2)   0.11   0.09   0.06   0.045   0.035       Calculated sol P (×51)   5.61   459   3.06   2.295   1.785       Turbidity (NTU)   51.5   47.1*   19.2*   13.3   7.2                 *floc like ppts were settling 5 min after addition of FeCl3            Contractor supplied FeCl3 solution was used (PVS Tech PJST #28358-4 dtd 1-/31/00 stored at RT)             
 
         [0059]     Table 8 confirms that if ferric chloride is added after aeration  
         [0060]     a) Lesser amount of FeCl3 is needed to remove phosphate and that the excessive use is unnecessary; and  
         [0061]     b) ORP is additionally increased by a significant amount, while soluble Phosphate and turbidity are reduced.  
                                                                                             TABLE 8                           EFFECT OF REVERSING THE SEQUENCE OF IRON ADDITION AND AERATION       Feb. 19, 2002                IN DUPLICATE   IN DUPLICATE                    Beaker 1   Beaker 2   Beaker 3   Beaker 4   Beaker 5               BLANK   IRON FIRST   IRON FIRST   AERATION FIRST   AERATION FIRST           None   FeCl3 30** μl   FeCl3 30** μl   AIR 10 psi 30 min   AIR 10 psi 30 min           stirred slowly 30 min   AIR 10 psi 30 min   AIR 10 psi 30 min   FeCl3 30** μl   FeCl3 30** μl       Initial ORP = −119.6 mV   290 μl   290 μl   290 μl   290 μl   290 μl       PS2A POLYMER   Wait 1 hr   Wait 1 hr   Wait 1 hr   Wait 1 hr   Wait 1 hr   Change                    ORP after 1 hr   −45.3   101.8   111.5   134.6   134.2    26%       Sol. P (Avg. of 2)   0.825   0.54   0.53   0.41   0.38       Calculated sol P (×7)   5.775   3.78   3.71   2.87   2.66   −26%       Turbidity after 1 hr   51.1   30.7   35.1   22.6   26.4   −26%                 Aeration was done through four new ceramic filter cartridges, so that the other two beakers do not have to wait for 30 min.            All the beakers got similar treatments w          to          .            Contractor supplied (FRESH) FeCl3 solution was used (PVS TECH #39433-1 of Feb. 04, 2002)            Exactly 1 ml sample was filtered through .45 μm syringe filters and all was added so tube for sol P determination.             
 
         [0062]     Table 9. This table represents the effect of adding pickle liquor before and after aeration. Normally, pickle liquor has often been seen to lower the ORP by approximately 80 units but in this sample it didn&#39;t. However, the relative gain in ORP by aeration was lesser than that with FeC13 in table 8 above. The phosphorus got removed possibly due to small portion of ferric formed at specified ORP, but it does not reduce the overall turbidity of the resulting solution. Even aeration didn&#39;t have any effect. Again, excessive use of pickle liquor had no additional benefit.  
                                                                   TABLE 9                           ROLE OF PICKEL LIQUOR, WITH OR WITHOUT AERATION       Jan. 24, 2002                Beaker 1                           Raw sample   Beaker 2   Beaker 3   Beaker 4   Beaker 5       Chemical addition   None   Pickel Liqor 50 μl   Pickel Liqor 100 μl   Pickel Liqor 50 μl   Pickel Liqor 100 μl       Action   Undisturbed   Undisturbed   Undisturbed   Aerated 15 min   Aerated 15 min       Initial ORP = −136.1   Wait 10 min   Wait 10 min   Wait 10 min   Wait 10 min   Wait 10 min                    ORP   −121.2   −127.6   −130.5   3.3   −37.5       Sol. P (Avg. of 2)   0.14   0.12   0.07   0.075   0.07       Calculated Sol P (×14)   1.96   1.68   0.98   1.05   0.98       Turbidity   87.1   86.3   92.6   86.1   88.5                 Contractor supplied Pickel liqor solution was used (PVS Tech T/T 109 24A DTD            Exactly 1 ml sample was filtered through .45 μm syringe filters and 500 μl of filterate was taken for sol P determination.             
 
         [0063]     Although the present invention has been described herein with respect to a limited number of presently preferred embodiments, the foregoing description is intended to be illustrative, and not restrictive. Those skilled in the art will realize that many modifications of the preferred embodiment could be made which would be operable. All such modifications, which are within the scope of the claims, are intended to be within the scope and spirit of the present invention.