GB2035814A - Removing contaminants from waste liquid - Google Patents

Abstract

A process for removing contaminants from waste liquid e.g. water comprises removing contaminants such as benzene, toluene, chlorobenzene, methyl chloride, trichloroethane, vinyl chloride and xylene from waste liquid by stripping the waste liquid gas e.g. air, nitrogen, carbon dioxide, propane. The gas may be passed into an incinerator for combusting the contaminants. The stripping of the waste liquid preferably takes place in a packed column.

Description

SPECIFICATION Process for removing contaminants from waste water Background of the Invention The present invention relates to a process for stripping contaminants from water with a gas and more particularly the present invention relates to a process for stripping contaminants from waste water by contacting or stripping the waste water with the air in a packed column.

In a chemical plant, water is utilized in many of the processes for producing chemicals or polymers. Thus, water is utilized as a reactant in hydrolysis operations, as a separation media, as a washing media and as a transportation media for the various chemicals and solvents that are utilized in chemical processes. Also, numerous organic compounds are used for a variety of purposes. Thus, chlorobenzene is utilized in the process for forming the phenyl-containing intermediates that are utilized to produce polymers containing phenyl radicals therein. Benzene is produced as a by-product in this reaction. Toluene is utilized in many resin hydrolysis processes. Vinyl chloride is a reactant in the process for producing vinyl polymers.In silicone plants, methyl chloride is utilized in the basic process for producing methyl chlorosilanes by the reaction of methyl chloride with silicon metal in the presence of a copper catalyst. Xylene is utilized as a solvent for silicone resins and other silicone compounds and, thus, is frequently present in the silicone plant as well as in other plants.

It should be understood that for most of such compounds and ingredients utilized in chemical processes, the bulk of such compounds are removed or separated from the products, if desired, by decantation or distillation separation techniques. However, by the nature of the water which is utilized in these processes and as a washing medium in the manufacturing plant, small amounts of such compounds such as benzene, chlorobenzene, methyl chloride, toluene, vinyl chloride and xylene as well as other intermediates become solubilized in the water and cannot be removed from the water except with extreme difficulty. There are, of course, other compounds in chemical plants which become solubilized in the waste water and, thus, cannot be removed from the water except by impractical procedures or with extreme difficulty.

Examples of solubilized contaminants that are found in waste water of the chemical plants are, for instance, allyl bromide, allyl chloride, amyl chloride, amylene, butene, dibutyl ether, etc.

Prior to the present time, it was common to treat the waste water from the chemical plant in accordance with the following exemplary procedure prior to returning it to the environment. The water was passed into a flotation tank where all floating impurities were removed. It is to be understood that prior to this time all contaminants in the water that could be removed by decantation had already been removed. Then the waste water was passed to a series of tanks in which a mild base was added to the water so as to increase the pH and, thus, cause precipitation of some contaminants. The water was then subsequently passed to a tank or a purifier tank where any precipitate that was formed as the result of the base addition was removed. The clear water was then passed to the second pH adjustment tank area where it was neutralized with acid.The clear water after it had been allowed to settle for a while and undergo biological purification was allowed to pass into the environment.

Such water was pure except for the fact that it contained minor amounts of solubilized contaminants. Initially, such contaminants were permissible in waste water that was returned to the environment. However, new regulations have limited the concentrations of contaminants, such as benzene, in waste water that is passed back to the environment to a few parts per million or even a few parts per billion level.

Accordingly, it became necessary to find a procedure for treating waste water so as to eliminate most or all of the contaminants in such waste water such that the amount of impurities which are harmful to the environment would be reduced to a few parts per million or, for instance, to a few parts per billion by a simple and economic process. Such a simple and economic process has not been found up to the present time. Attention should be directed to the patent application of Harry McEntee, Serial No. 828,367, entitled "Process for Removing Biphenyls from Chlorosilanes". This patent application discloses a novel process for removing polychlorinated biphenyls from silanes and siloxanes by adsorbing the polychlorinated biphenyls on a bed of activated carbon or molecular sieves.After the adsorption bed gets saturated with biphenyls then it is treated with a desorption solvent such as chlorobenzene which absorbs the polychlorinated biphenyls from the activated carbon bed permitting the bed to be utilized once more in the process of treating streams of silanes and siloxanes.

While such a process is expensive (a costly plant facility, the cost of the activated carbon, and the high operating costs), nevertheless, it can be tolerated since the activated carbon can be rejuvenated; since the amount of silanes and siloxanes containing polychlorinated biphenyls in them are not very large, and since the product has a high commercial value. Accordingly, in principle, an adsorption bed could be utilized to remove any of the above impurities which are adsorbed onto activated carbon, molecular sieves or some other type of adsorbent.However, to treat waste water in this manner, it would be necessary to utilize beds of adsorbent that are very large compared to the ones discussed above (100-1000 times as large) and there, accordingly, would have to be utilized very large streams or quantities of rejuvenation solvent which must then be purified by distillation and/or burned in an incinerator which would make the process unbearbly expensive.

Further, some of the impurities can be removed from waste water by biological degradation, but this biological degradation process is expensive; is subject to poisoning due to some of the contaminants, and is ineffective for many organic contaminant compounds.

Another process that can be used to separate small quantities of impurities or contaminants from waste water would be distillation, but such distillation processes would be very expensive due to the high energy requirements and the substantial capital investment for distillation facilities.

Accordingly, it was highly desirable to find an inexpensive method of removing solubilized contaminants or impurities from waste water emanating from any type of manufacturing plant and more specifically a chemical plant.

Strippers are known in chemical plants. An example of a steam stripper for utilization in the chemical plant is, for instance, to be found in the article entitled "Choosing a Process for Chloride Removal" by M.F. Nathan, appearing in the January 30, 1978 issue of Chemical Engineering. Steam stripping, as disclosed by the above article, is also well known where steam is utilized to strip a solvent or a compound in solution so as to separate the compound or solvent from the solution by passing the steam vapor through the solution and then taking the steam that is received therefrom and selectively cooling it so as to separate the stripped compound from the condensed water.For instance, a stripping technique may be utilized in a silicone manufacturing plant to strip with steam alone or in combination with an inert gas, the solvent from a silicone resin solution so as to remove completely all the solvent and leave behind the solid or liquid resin. In such a procesure, stripping is utilized as a separation technique to recover a compound which is dissolved in a solution.

Accordingly, it was highly unexpected that low concentration contaminants ( < 1 ppm to > 1000 ppm) could be very effectively and almost totally removed from waste water by simply contacting the water with a relatively small quantity of a gas, preferably air and subsequently separating the liquid and gas phases.

Summary of the Invention General Description of Invention There is provided by the present invention a process for removing contaminants from waste water comprising (1) passing a first stream of a gas into contact with a second stream of waste water having therein as contaminants a compound selected from the class consisting of allyl bromide, allyl chloride, amyl chloride, amylene, benzene, butadiene, butene, butyl bromide, butyl chloride, butyl iodide, butyl methacrylate, butylene, chlorobenzene, cyclohexyl amine, dibutyl ether, dimethyl carbonate, dimethyl sulfide, furfuran, heptane, hexane, isoprene, methyl chloride, octene, pentane, pyrrole, tetrachloroethane, tetrachloroethylene, toluene, trichloroethane, trichloroethylene, vinyl chloride, xylene and mixtures thereof for a sufficient amount of time and (2) separating a third stream of said waste water from said gas which has a smaller amount of contaminants than said second stream and removing a fourth stream of said gas from said waste water having said contaminants therein. By reason of this process, any amount of the above contaminants may be removed although for most purification techniques it is desirable that at least 40% of the contaminants be removed. It should be noted, as will be disclosed below, that the above list of contaminants is a preferable list. There are other solubilized contaminants that may be removed from the waste water. As stated above, it is preferred that the contact between the gas and the waste water take place in a packed column.

In addition, it is preferred that the gas be air, such that the air emanating from the packed column contain the contaminantsror impurities therein can be passed to an incinerator wherein the impurities or contaminants are combusted to carbon dioxide and water which can be safely vented to the atmosphere. If needed, the combustion gases can be further treated to remove Qbjectionable products, such as halogen containing compounds.

Description of the Preferred Embodiment In order to fully appreciate the significance of the invention herein disclosed, and to recognize its impact in practical operations, it is important to develop a clear understanding of a few terms and characteristics associated with stripping columns.

In the design and operation of a stripping column, one of the most basic factors is the equilibrium distribution of the chemical compound of interest (contaminant) between the liquid phase and the gas phase. There are various ways in which this distribution may be expressed.

One common way (the one used in this discussion) is by use of the term "relative volatility", which is frequently denoted by the Greek letter a. A simple illustration will assist in understanding the meaning of relative volatility. Consider a small glass bottle to which is added a liquid mixture of water and contaminant "A", and then it is sealed with a suitable inert cap so there can be no gain or loss in the amount of material contained in the bottle. The quantity of liquid added is sufficient to only partially fill the bottle. The liquid phase is composed of water and contaminant "A" (with a negligible amount of dissolved air), and the gas phase is composed of air, water vapor, and "A" vapor. It is assumed that the total pressure and the temperature remain constant.The contents of the bottle are assumed to be intimately mixed for a long period of time so that there are no continuing changes in liquid or the gas phase. Now, without otherwise disturbing the system, a very small sample of the liquid phase and a very small sample of the gas phase are removed. (This can be accomplished by using micro syringes with needles that can pass through a rubber cap seal on the bottle. When the needles are withdrawn the cap maintains the bottle in a sealed condition). Each of the samples is analyzed for "A" and water. From the results, the following quantities are readily determined: (1) the concentration of water in the liquid phase, (2) the concentration of "A" in the liquid phase, (3) the concentration of water vapor in the gas phase, and (4) the concentration of "A" vapor in the gas phase.For the present illustration, assume the following values are obtained: concentration of water in liquid phase 0.99 g/cc concentration of "A" in liquid phase 0.01 g/cc concentration of water vapor in gas phase 2 X 10-5 g/cc concentration of "A" vapor in gas phase 2 X 10-6 g/cc By definition, as used here, the relative volatility, , is: (conc. "A" vapor/conc. water vapor) in gas phase a= (conc. "A" liq./conc. water liq.) in liq. phase By insertion of the above values in the equation for a it is found that, (2X 10-6/2 x 10-5) a =9.9 0.01/0.99 In words, this expression states that, relative to the water in the two phases there is 9.9 times as much "A" in the gas phase as in the liquid phase.

The value of a represents the thermodynamic equilibrium for this combination of components and is independent of the relative size of the two phases. It is, however, a function of the temperature and in some cases a function of the concentration. In many instances, the variations with concentration level may be ignored without serious effects.

The significance of a in stripping operations may now be examined. If the value of a is exactly one (1.0) then the relative composition of the vapor is identical to the liquid. However, if the value is greater than one (1.0) then there is a potential for preferentially removing one component from the liquid into the gas phase. The greater the value of a the greater the potential. This concept can be demonstrated by comparing three cases wherein the a values are 5, 10 and 100, respectively. In each case, a two component liquid (water and component "A") is contained in a flask. The flask is immersed in a heat source so that the temperature remains constant. The liquid is vigorously agitated while dry air is passed through the system at a constant rate of 1 liter per minute. The air leaves the flask containing the equilibrium concentrations of the vapors of the two liquid components.Under these circumstances, it is desired to reduce the concentration of "A" in the liquid from an initial value (1 percent by weight) to a preselected final value (0.1 percent by weight) in the remaining liquid. The temperature of the entire system is maintained at 20 C throughout the operation, and the total pressure is 1 atmosphere.

Case No. 1 a = 5 Initial conditions: 1 kg of liquid 99% wt H20 1% wtA Vapor pressure of H20 at 20"C = 18 Torr Dry air flow rate = 1 liter/min Weight in Flask, g WA Time, min WH20 WA WH2O + WA 0 990 10 0.01 10,000 808 3.62 0.0045 20,000 626 1.01 0.0016 23,500 562.3 0.591 0.0010 So, to reduce the concentration of A to 10% of its original value (1 % to 0.1 %) would require: 23,500 minutes, or 23,500 liters of air 427.7 g H20 evaporated 9.41 g A evaporated 231 kilocalories of energy Case No. 2 o~ = 10 Initial conditions: 1 kg of liquid 99% wt H20 1% wt A Vapor pressure of H20 at 20 C = 18 Torr Dry air flow rate = 1 liter/min Weight in Flask, g WA Time, min WH2o WA WH20 = WA 0 990 10 0.01 5,000 899 3.81 0.0042 10,000 808 1.31 0.0016 12,000 771.6 0.827 0.0010 So, to reduce the concentration of A to 10% of its original value (1 % to 0.1 %) would require: 12,000 minutes, or 12,000 liters of air 218.4 g H20 evaporated 9.17 g A evaporated 118 kilocalories of energy Case No.3 a=100 Initial conditions: 1 kg of liquid 99% wt H20 1% wtA Vapor pressure of H20 at 20 C = 18 Torr Dry air flow rate = 1 liter/min Weight in Flask, g WA Time, min WH20 WA WA + WH2o 0 990 10 0.01 1,000 971.8 1.56 0.0017 1,250 967.25 0.0978 0.0010 So, to reduce the concentrations of A to 10% of its original value (1 % to 0.1 %) would require: 1 ,250 minutes, or 1,250 liters of air 22.75 g H20 evaporated 9.02 g A evaporated 12.3 kilocalories of energy.

Summary Table Characteristic a = 5 a = 10 a= 100 Time required, min 23,500 12,000 1,250 Total quantity of air required, l 23,500 12,000 1,250 Quantity of H20 427.7 218.4 22.75 evaporated from flask, g Quantity of A 9.41 9.17 9.02 evaporated from flask, g Energy required 231 118 12.3 for evaporation, kilocalories Thus, it is seen that as the value of a increases the operating characteristics such as, time required, quantity of air required, energy required, etc., all decrease. In general, as a increases the stripping operation becomes easier and less expensive. High values of a are also reflected in smaller equipment sizes, or greater removals for a given size system.In summary, it is apparent that a is a principal determinant as to whether or not it is practical to remove a specific component by stripping.

In the foregoing examples it was assumed that the entering air was dry (zero moisture content). As the moisture content in the entering air increases, the amount of water evaporated during stripping decreases and the energy required decreases. However, the time required to achieve a specified degree of removal of contaminants (or the required quantity of air) changes relatively little, unless the a value is very low (less than 5, for example).

Most stripping operations of engineering and commercial value have a continuous flow of the stripping gas and of the liquid. This type of operation may be represented, for the convenience of analysis, as one or more tanks in series with countercurrent flow of the two streams. To illustrate the effect of this type of arrangement, four cases will be considered which have one, two, four and an infinite number of tanks in series. The a value is assumed to be 100, the liquid flow rate through the system is 0.1 liters per minute, the gas flow rate is 30 liters per minute, the temperature is 20 C throughout and the total pressure is 1 atmosphere. The entering liquid is 99% by weight water and 1 % by weight component "A". The gas and liquid leaving each tank are assumed to be in equilibrium in reference to the distribution of component "A". Under these conditions each tank is termed an "equilibrium stage" in the technical literature.

Case No. 4 1 Stage a 100 Liquid Flow Rate 0.1 I/min (-100 g/min) Gas Flow Rate 30 I/min (- 36 g/min) Vapor Pressure H20 at 20 C 18 Torr Entering Gas Composition Dry Air Entering Liquid Composition 99% wt H20 1% wt "A" Quantity of "A" Leaving in Gas Stream per Minute 0.354 g Quantity of "A" Leaving in Liquid Stream per Minute 0.646 g Percent Removal of "A" From Liquid 35.4% Case No. 5 2 Stages a = 100 Liquid Flow Rate 0.1 I/min (-100 g/min) Gas Flow Rate 30 I/min (- 36 g/min) Vapor Pressure H20 at 20"C 18 Torr Entering Gas Composition Dry Air Entering Liquid Composition 99% wt H20 1% wt "A" Quantity of "A" Leaving in Gas Stream per minute 0.459 g Quantity of "A" Leaving in Liquid Stream per minute 0.541 g Percent Removal of "A" From Liquid 45.9% Case No. 6 4 Stages a= 100 Liquid Flow Rate 0.1 1/min (-100 g/min) Gas Flow Rate 30 I/min (- 36 g/min) Vapor Pressure H20 at 20 C 18 Torr Entering Gas Composition Dry Air Entering Liquid Composition 99% wt H20 1% wt "A" Quantity of "A" Leaving in Gas Stream per Minute 0.524 g Quantity of "A" Leaving in Liquid Stream per Minute 0.476 g Percent Removal of "A" From Liquid 52.4% Case No. 7 Infinite Number of Stages a= 100 Liquid Flow Rate 0.1 I/min (-100 g/min) Gas Flow Rate 30 I/min (- 36 g/min) Vapor Pressure H20 at 20"C 18 Torr Entering Gas Composition Dry Air Entering Liquid Composition 99% wt H20 1% wt "A" Quantity of "A" Leaving in Gas Stream per Minute 0.548 g Quantity of "A" Leaving in Liquid Stream per Minute 0.452 g Percent Removal of "A" From Liquid 54.8% From the examination of cases number 4 through 7 it is seen that having several stages in series increases the removal of the contaminant from the liquid stream. However, there is a fixed limit for removal even with an infinite number of stages, for the given operating conditions.It should be recognized that the a value used in these cases is quite high (100) in comparison to most industrial situations encountered, and there is a low ratio of liquid to gas flow rates required to achieve approximately fifty percent removal of the contaminant from the liquid stream. (Liquid to gas flow rate ratio is 0.1/30 on a volumetric basis and 1/0.36 on a mass basis). Decreasing the liquid to gas flow rate results in greater removal of the contaminant from the liquid stream, but increases the problems of handling and disposing of the larger gas volumes for a specified quantity of liquid to be treated.

In the course of studying this concept, a major discovery was made that completely changes the apparent value of the concept. It was found that the liquid contaminant combination (waterbenzene, water-toluene, etc.) of prime interest exhibit extremely high values of a. Values ranging from 6,000 to 60,000 depending on the particular combination and the temperature have been found.

A re-evaluation of the above example (1.5 million pounds of waste water and 50,000 pounds per hour of air) with an a value of 10,000 shows that an infinitely high column would remove 100 percent of the contaminant from the water. More important, a column approximately 20 feet high can remove 99 percent of the contaminant under the same flow conditions. So, the unanticipated discovery of the high a values has changed an apparently worthless concept into a very valuable and practical one.

The inter-relationships among the variables of a, L/G, temperature, and percent removal are illustrated by Figs. 1 and 2. In each case a column equivalent to seven equilibrium states in series is assumed, one at 20 C and the other at 0 C. A comparison of the two figures shows that the amount of a contaminant that can be removed for a given set of conditions decreases as the temperature decreases. The importance of a and L/G in obtaining high removal of a contaminant from water is clearly evident from the curves.

In determining the size of the packed column, for carrying out such separation, the following factors are pertinent. In said packed column there must be a liquid rate into the packed column of 5,000 to 30,000 pounds per square foot per hour of waste water where the L/G ratio varies from 5 to 100, where L is pounds of liquid going into the column per square foot per hour and G is pounds of gas going into the column per square foot per hour where the contact between the waste water and gas takes place at a temperature of at least 0 C, and there is at least 40% by weight removal of the contaminants in said waste water and wherein the a of the system is at least 200 for an L/G ratio 5, and is at least 3000 for an L/G ratio of 100, where a is defined by the equation (1) but may also be defined less accurately by (2) a= kM FV where V = mass of vapor in Ibs. per cubic foot of gas M = mass of waste water being stripped in Ibs.

F = air flow rate cubic feet/hr.

where the constant k is defined by the equation k= 1 - 1n - t Cf wherein the above equation t = time in minutes ci = initial concentration of contaminant in waste water, parts per million Cf = final concentrations of contaminant in waste water, parts per million where k and a are defined by the above equation; (3) for a particular gas and for a particular contaminant.

The constant k is determined by the above equation for a particular contaminant and for a particular gas such as, air in a small sample which is run in the laboratory stripper. However, the value of may also be determined by the equation (1) by impractical methods. This k can then be utilized in the equation for calculating the a value. With the a value and the other quantities set forth above the particular packed column for a particular separation of contaminants from waste water can then be calculated.

It should be noted that as the L/G ratio varies from 5 to 100, the contaminant water system would have to have an a value varying from at least 200 to at least 3000, so as to be able to be separated at the desirable level from the waste water in a temperature of 23 C. For other temperatures the minimum value for a would vary from the above. It should be noted that if the a value is not at least 200 at 235C, then the contaminant cannot be removed by the instant process. In addition, if the a value of the contaminant is between 200 and 3000 at 23 C, then the L/G ratio will be between 5 to 100, so as to design a specific column so as to carry out the necessary separation. Thus, for an L/G ratio of 10, the minimum value can be calculated. Then, if the particular contaminant has at least that size a value then it can be removed by the instant process. Otherwise, the L/G ratio has to be reduced or the contaminant can not be removed appropriately by the instant process. A packed column designed in accordance with the above limitations is able to remove 99.99% by weight of the contaminates from waste water.

It should be noted that while the concepts of the instant invention may be utilized as separation techniques for separating different compounds from each other, the concepts of the instant invention are more preferably utilized in removing small quantities of compounds from a common solvent by a cheap and inexpensive method.

The method of the present invention is preferably utilized to decrease the amount of contaminants in solvents where they may be present at concentrations of a few percentage points or less and decrease such concentration of materials to the range of parts per million or parts per billion in the solvent.

It should also be noted that the gas that may be utilized in the instant invention in the stripping technique of the instant invention need not be limited to air. However, air is most preferably used since it is readily available and then the contaminants that are present in the air can be rendered harmless by utilizing the air for combustion in an incinerator. With respect to the liquid, the concepts of the instant invention are also applicable to liquids other than water in removing contaminants or minor amounts of compounds dissolved in such liquids by passing a suitable gas in contact with such liquids.It should be noted that the principles for determining the separation of the contaminants from the liquid in accordance with the above discussion will have to be applied in determining the amount of separation that is possible between a specific liquid and a specific gas and for determining the dimensions of the apparatus to carry out such a separation.

It should be noted, and specifically with respect to water, that the determination whether the separation of the contaminants or impurities from the water is possible is determined by the value of a. However, as seen from equation (1), a is defined as the grams of contaminant per gram of water vapor in vapor phase divided by the grams of contaminant per gram of water in liquid phase.

It is necessary to have the a value for a particular contaminant solvent system to calculate the size of the packed column.

It should be noted that while the separation technique of the instant case can be accomplished in apparatuses other than a packed column, such as stirred tanks, it is preferable in accordance with the instant invention to carry out the separation technique in a packed column. Preferably, the column is packed with plastic packing and the column is constructed such that the packing can be removed and cleaned or replaced periodically.

in the design of such columns or other separation equipment, it has been found the liquid or water flow rate through the column would in all cases most probably vary within the range of 5000 to 30,000 pounds per square foot, per hour. In the design of such packed column, it is also necessary to know the liquid to air ratio going into the column.

In accordance with the instant invention, for the necessary separation of the contaminants from the waste water it is desirable to have a liquid or air ratio of 5, varying up to 100. In order, also, to determine the minimum value of a that is necessary in such a column in order to carry out the necessary separation there must be also specified the amount of separation necessary of the contaminant, that is, percentage removal of the contaminant from the liquid into the gas.

Accordingly, carrying out a material balance on a column where L is equal to pounds per water, per hour flowing through the column; x is equal to pounds of contaminant per pound of water; G is pounds of dry air per hour flowing through the column and y is pounds of contaminant per pound of dry air leaving the column, and setting up a material balance with 40% removal of the contaminant and none of the contaminant in the entering air there is obtained an equation y Gy = .4 Lx where - = .4 L/G = 40 for L/G = 100 or is = .2 for L/G = 5.

x Rather than use the empirical method for calculating a, the slightly less accurate equation (2) may be used to arrive at a value of a that is needed for a certain contaminant as will be explained below.

At this point, it is necessary to go through the derivation of the equation (2) for a before calculating the value of a for a particular contaminant. For very low concentrations of organics in water and a given batch quantity of water, air flow rate temperature in a liquid air contacting system the rate change of concentrations can be given by dc --kc.

dt Expansion of this change of concentration rate in the form of a material balance in a particular system on the organic in the waste water and the air gives the equation: kM FV where M = mass of solution that is to be stripped in pounds F= air flow rate in cubic feet per hour V= mass of water vapor in the air per cubic foot of air and the quantity can be given in Ibs. of vapor per cubic foot of air and the constant k is 1 c.

1n In - t Cf where t = time in hours to carry out a certain amount of separation cj = concentration of contaminant in liquid at the initial point in parts per million Cf = concentration of contaminant in liquid at the final point of determination given in parts per million.

As can be seen a will vary depending on the temperature on which the stripping technique is carried out.

The value for k is determined from the foregoing equation by making a plot for a particular contaminant in water over a time period in terms of the logarithmic of the fraction of the initial concentration of contaminant in the waste water versus the time as the water is being stripped with the air and also at a particular temperature. A plot of such determination on semi-log paper yields a value for k which can be inserted into the equation.

With respect to the value for V, this is the pounds of water vapor per cubic foot of air.

The pounds of water vapor per pound of air can be determined for air by multiplying the vapor pressure, divided by the partial pressure of the air, times 18/29, 18 being the molecular weight of water and 29 being the average molecular weight of air. Accordingly, for vapor pressure of water at 23 C of 22 mm of Hg, there is obtained .0185 and there is obtained a value for a = 1/0.0185 times L/G times 0.4. Accordingly, going back to the material balance for an L/G ratio of 100 inserted into the material balance, you obtain an a of 2162, and in the same equation for L/G ratio of 5, you obtain an a of 108.It should be noted that two basic assumptions were made in the above calculations for the specific a value, besides the setting of the L/G rate and the liquid rate going into the column, that is, the temperature at which the separation was being carried out, that is, 23 C, and secondly, that there was set into the equation that there would be at least 40% removal of the contaminant from the water into the air.

Accordingly, the minimum a that is necessary for a particular column will also vary depending on the variation in the temperature and depending on the variation in the minimum removal that is desired in the setting of the equations. However, in the calculations of the instant case, it has been assumed in order to set some limits on the design of the column that there must be at least 40% removal of the contaminants from the water in order to get any substantial removal of such contaminant and the other assumption, of course, is not as valid since the 23 C temperature range can vary.Accordingly, it is envisioned that the separation in the instant case can take place in the temperature range of anywhere from 0 to 95 C, for water and air and more preferably take place at a temperature range of 0 to 60 C in the system of water and air.

Since the above calculations of the minimum of a for the L/G ratio of 100 is 2162, a minimum value of a for such an L/G ratio of 3000 would be approximated since the value of a for 2162, assumes that the gas and the water come to a thermodynamic equilibrium at the top of the packed column. Since this would take only in an infinite column then it is assumed that a more finite column be utilized in which the a value is slightly higher, that is, the value of 3000.

In the same way for the ratio of L/G equal to 5, there is obtained the value of 108. Since the value of a 108 could be for an infinitely tall column in which the liquid entering the column would be in equilibrium with the air leaving the column, the minimum value of a is assumed at 200, such that the required amount of separation of L/G ratio of 5, would take place in a finite column.

It should be noted that the a value at 23 C is also given in the above calculations. A higher value of a would be obtained at 0 C as the absolute minimum that is necessary to carry out 40% removal of the contaminant from the water for the given L/G ratios.

It should be noted that the a at 0 C with the same for the L/G ratio of 100 is equal to 10,600 and the a value for L/G ratio of 5 at 0 C = 530.

It should be also noted that the minimum a that the contaminant must have in the water and air in order to be removed at O to 95 C under the above conditions, is 0.64. All these a values are at atmospheric pressure. At other pressures the a values will vary.

Accordingly, the a minimum value of 0.64 is at 1 atmospheric pressure at 95 C, at an L/G ratio of 5, with 40% removal of the contaminant. It is to be noted that this minimum value of a is obtained either where the air introduced into the packed column is saturated with water vapor or where the entering air is completely free of water vapor. It is to be noted that if the entering air is completely free of water vapor it will be saturated with water vapor. Air entering the columns between the above extremes will evaporate the necessary water so as to be saturated when it leaves the column using the necessary heat.

As can be appreciated it is difficult to operate a packed column at 95 C. Accordingly, it is desirable to operate the column at or near room temperature, that is, 23 C or lower, such that values of the contaminants are considerably larger at the lower temperature and further the air doesn't hold as much water vapor so that the air can set more efficiently in stripping contaminants. Also, at lower temperatures heat for water evaporation is negligible.

Accordingly, the a value for 95 C is given above as the absolute minimum needed for a contaminant to be reported by the process of the instant case by a packed column. Further, as noted previously this minimum a value is for a L/G of 5, and a 40% minimum removal of the contaminants. As can be appreciated from the previous discussion, the minimum a values at lower temperatures are considerably higher. However, the value of 0.64 is the minimum a that can be tolerated for a temperature variation of O to 95% and an L/G ratio varying from 5 to 100, and to obtain at least a 40% removal of the contaminant from the water stream entering the packed column.

The above calculations and values state that in order to obtain 40% removal of the contaminant from the water into the air for a column in which the liquid rate varies from 5000 to 30,000 pounds per square foot, per hour in which the L/G ratio is 100 at 23 C, the a value of the contaminant as determined empirically has to be at least 3000 and for the same conditions for an L/G ratio of 5, the a value of the contaminant has to be at least 200 in order to obtain the desired separation. To determine if the contaminant has the desired a value for the above conditions or the minimum value for the above conditions, a is determined empirically in the laboratory from equation (1).If the minimum value of a at 23"C is at least the minimum value of a given above, that is, 200 for L/G ratio of 5, and 3000 for an L/G ratio of 100, then the contaminant can be separated from the water with air in accordance with the invention of the instant case. The above analysis is for 23 C and is exemplary only. It is, of course, noted that the minimum value of a as calculated from equation (2) will differ at different temperatures.

It should be noted that the following compounds have been found to have suitable a values for separation from water with air in accordance with the instant invention; allyl bromide, allyl chloride, amyl chloride, amylene, benzene, butadiene, butene, butyl bromide, butyl chloride, butyl iodide, butyl methacrylate, butylene, chlorobenzene, cyclohexyl amine, dibutyl ether, dimethyl carbonate, dimethyl sulfide, furfuran, heptane, hexane, isoprene, methyl chloride, octene, pentane, pyrrole, tetrachloroethane, tetrachloroethylene, toluene, trichloroethane(1, 1, 1), trichloroethylene, trifluorotrichloroethane, vinyl chloride and xylene.

Other compounds that have suitable a values for separation in accordance with the instant invention from waste water utilizing the air and in accordance with the parameter set forth previously are as follows: 1, 1 dibromoethylene; 1, 2 dibromoethylene (cis 8 Trans); allyl acetate; iso amyl ether; 3bromo-propene-1; diallyl ether; allyl formate; 3-iodo-propene-1; triuretdiamidine; 2-bromo-2methyl butane; 1 -bromo-2, 2-dimethyl propane; 1-bromo-2-methyl butane; n-butyrate (n); ncaproate (iso); 1-chloropentane; 2-chloropentane; 3-chloropentane; 4-chloro-2 methyl butane; 3chloro-2 methyl butane; 2-chloro-2 methyl butane; 1-chloro-2 methyl butane; 2-iodopentane; 2iodo-2 methyl butane; 4-iodo-2 methyl butane; 1 -iodopentane; pentanthiol-1; pentanthiol-3; 2methyl butanthiol-4; pentene-1; 2-methyl-butene-3; 2-methyl-butene-1; benzene; phenacyl bromide; butadiene (1, 2); butadiene (1, 3); butane (n); butane (iso); butyl acetate (tert); 1-bromobutane; 2-bromo-butane; 1-bromo-2 methyl propane; 2-bromo-2 methyl propane; 1-chloro butane; 2-chloro butane; 1-chloro-2 methyl propane; 2-chloro-2 methyl propane; 2-iodo-2 methyl propane; butene-1; butene-2 (cis 8 trans); butyne-2; dimethyl chloroarsine; carbon disulfide; carbon monoxide; tetrachloromethane; tetrafluoromethane; tetraiodomethane; chloroethyne; phenylchloride (chlorobenzene); chlorobromoethane (1, 1); chlorobromoethane (1, 2); chlorobromomethane; 1 -chloro-2 butanone; 1, 1 chloronitroethane; crotyl chloride; isocrotyl chloride; cyclobutane; cycloheptane; cycloheptene; cyclohexadiene (1, 3); cyclohexadiene (1, 4); cyclohexane; cyclopentadiene (1, 3); pentane; propane; 1, 1 dibromoethane; 1, 2 dibromoethane; 2, 2 dichloroethanol; 1, 1 dichlorobutane (n); 1, 1 dichloroethane; 1, 2 dichloroethane; 1, 1 dichloroethene; dichloroiodomethane; 1, 1 dichloro-1 -nitromethane; 1, 1 dichloro-1 nitrosoethane; 2, 3 dichloropentane; 2, 4 dichloropentane; 2, 3 dichloro-2 methylbutane; 4, 4 dichloro-2 methylbutane; 1, 2 dichloropropane; 1, 3 dichloropropane; 2, 2 dichloropropane; 1, 1 dichloropropionitrile; 1, 1 dichloropropene-1; 1, 2 dichloropropene-1; 1, 2 dichloropropene-2; 1, 3 dichloropropene-1; 2-ethylbutyraldehyde; diethyl carbonate; diethyl monoselinide; diethyl sulfide; diethyl telluride; 1, 1 difluoro-1, 2 dibromoethane; 1, 1 difluoro-2, 2-dichloroethane; 1, 1 difluoro-2 iodoethane; 1, 1, 1, 2 tetrachloro-2, 2-difluoroethane; 1, 1, 2, 2 tetrachloro-1, 2 difluoroethane; dimethylcyclohexane (o); dimethylcyclohexane (m); dimethylcyclohexane (p); 1, 5 dimethyl-2, 5 hexadiene; dimethylphosphine; dimethyl selenide; dimethyl sulfide; di-isopropyl ether; n-iso-propyl ether; ethane; ethyl allyl ether; ethyl amyl ether; ethyl arsine; ethyl benzene; n-butyl ethyl ether; iso-butyl ethyl ether; tert-butyl ethyl ether; ethyl n-butyrate; chloroethane; ethylhydroselenide; iodoethane; ethyl methyl acrylate; ethyl thioacetate; ethyl isothiacetate; ethyl isovalerate; fluorobenzene; fluorodichloromethane; o fluorotoluene; m fluorotoluene; p fluorotoluene; 1, 1, 2 trichloro-l -fluoroethane; trichlorofluoromethane; furan; glycol dinitrile; 2-methyl hexane; n heptane; 3-methyl hexane; 2, 2 dimethyl pentane; 2, 4 dimethyl pentane; 3, 3 dimethyl pentane; 3 ethyl pentane; 2, 2, 3 trimethyl pentane; heptene-1; 2, 4 dimethyl pentene-2; 2, 4 hexadiene; 1, 5 hexadiene; n hexane; 2 methyl pentane; 2, 2 dimethyl butane; 2, 3 dimethyl butane; 3 methyl pentane; hexyl alcohol; 1 chlorohexane; 2 chlorohexane; n hexyl nitrate; 1 hexene; 2, 3 dimethyl butene 1; 3, 3 dimethyl butene 1; n butyl methyl ether; isobutyl methyl ether; isopropyl acetylene; methyl crotonate; ethyl cyclohexane; methyl cyclohexene; methyl cyclopentane; methyl cyclopropane; 2-methyl butanol-1; methyl ethyl carbonate; methyl ethyl sulfide; methyl phosphine; methyl propionate; methyl pyrrole (1); all octane isomers; all octene isomers; n pentane; 2 methyl butane; 2, 2 dimethyl propane; pentyne-1; pentyne-2; 1 -chloro propene-1; 2-chloro propene-1; 1-bromopropane; 2-bromopropane; isopropyl chloroformate; n propyl cyanide; isopropropyl cyanide; n propropnyl chloroformate; tetramethyl silicon; 1, 1, 2, 2 tetrachloroethane; 1, 1, 1, 2 tetrachloroethane; tetrachloroethylene; tetranitromethane; thiophene; toluene; 1, 1, 1 trichloroethane; 1, 1, 2 trichloroethane; trichloroethylene; triethyl silicon hydride; 1, 1, 2 trichloroethane; trimethyl phosphine; vinyl bromide; vinyl chloride; vinyl fluoride; m xylene; p xylene; o xylene; chloromethane; dichloromethane; trichloromethane; 1, 1, 1, 2, 2 pentachloroethane; hexachloroethane; 1, 2 dichloroethylene (cis 8 trans); 1, 1, 2 trichloroethylene; 1, 1, 2, 3 tetrachloropropane; 1, 2, 2, 3 tetrachloropropane.

It should be noted that other compounds in addition to the ones noted above can be separated in accordance with the instant process and in accordance with the above parameters.

The above list is not and cannot be exhausted without carrying out calculations on every possible conceivable organic compound that may be found in water. However, utilizing the above principles a worker skilled in the art may calculate the a value for a particular compound and determine if it is separable in accordance with the disclosure of the instant invention in a column or in a stirred tank.

It should be noted that separation or the removal of organic contaminants from water utilizing air can take place in a packed column where the water is passed or inserted into the column overhead and the air passed at the bottom allowing the air to come in contact with the water in the column and thus strip off most of the contaminants from the waste water in accordance with the principles that were discussed above.

It should be noted that utilizing the above principles there can be obtained or devised a packed column in which 99.99% by weight of the organic contaminants in the water are removed by the air.

It should be noted that some common organics cannot be removed from water to a desired extent because of their small values. Accordingly, most aliphatic alcohols and particularly low molecular weight aliphatic alcohols and ketones such as, acetone, are not removable by the process of the instant invention since such compounds do not have a sufficient a value to be removed in sizeable quantities from water utilizing the invention of the instant case. However, there are many, many organics which do have an appropriate a values such that they can be removed in sizeable quantities from water utilizing the novel stripping technique in accordance with the invention of the instant case.

As has been noticed previously, the removal or stripping of the contaminants from the waste water need not take place in a packed column. It, for instance, can take place in a stirred tank where the water is passed from one tank to another and into which stirred tanks there is passed air countercurrently to the passage of the water and over the body of the water such that with the stirring there is obtained intimate contact between the air and the water. The number of tanks required in such a stirring method, would be the number of stages that would be calculated for a packed column as being required to carry out the necessary separation of the contaminants from the waste water. It is now necessary to go into the procedure for determining the size of the packed column.

It should be noted that the diameter of the packed column is independent of the a value and is determined by the pressure drop that is desired between sections of the column, and the type of packing that is desired in the packed column. As the diameter of the column increases, the pressure drop decreases. However, the contact between the liquid and the gas may not be as good. On the other hand as the diameter of the column decreases the pressure drop increases and for a given liquid flow rate the diameter of the column might be so small that the rate of flow of liquid is very small through the column due to the gas holding the liquid up as it passes through the column. Generally, it has been found for water and air that there be picked a pressure drop across the column of 0.2 to 0.5 inches of water per foot of packing height.

Given the particular liquid flow rate and the gas flow rate the diameter of the column is picked and a particular packing is picked so as to give a pressure drop within a foot of packing height within the above range.

The next step is to determine the height of the column and this is done by mathematically calculating the number of states necessary to accomplish the necessary separation in the given packed column.

Assuming the concentration of the contaminant in the initial air is zero and applying a material balance equation over a section of the column comprising a point in the column, indicated by stage i, and the bottom of the column, there is obtained the following equation: G M=L(C+1-C) where G is the pounds of dry air per hour going to the column initially; My is the pounds of contaminant per pound of dry air coming from stage i;L is the liquid flow rate to the column, C + 1 is the concentration of the contaminants in the liquid coming from stage L + I; and C, is the concentration of contaminants in the liquid leaving the bottom of the column, where a in the English system is again defined as pounds of contaminant per pound of water vapor in the vapor phase divided by the pounds of contaminant per pounds of water in the liquid phase.The value of a written in terms of the material balance for a section of a column is then translated into the following representative values: G Mi/Ww (#) (L) (Ci + I - C Cj (Ww) (8) (ci) where in the above equations, Ci is the concentration of the contaminant in water at the end of the ith stage;Ww is equal to pounds of water vapor per hour in the air coming from the column and is equal to Pv 760 - times G, times ~8/29; where G is pounds of dry air per hour flowing through the column; 18 is the molecular weight of water; 29 is the average molecular weight of air; Pv is the vapor pressure of water at the existing temperature; and 760 is the total pressure in the column.

Accordingly, assuming a, L, Ww are all constant for a particular contaminant, for a particular liquid, for a particular temperature, and for a particular liquid flow rate, you get the following equation from the above: Ci + I - C, = = constant = k' Cj It should be noted the difference in concentration of the contaminant in the water between the Cj + I stage and C, stage divided by the concentration in the Cj stage is constant.This equation can be used to express the concentration on each successive stage from the first at the bottom of the column to the concentration on the Cj + I stage and finally the concentration of the contaminant in the liquid stream entering the top of the column, designated by C=+l. The equation results in a finite geometric series which can be summed up by the expression: I - k'n+l n I 1l~k' n+l - k1 wherein the concentration of the contaminant in the entering liquid stream, Cn+ll divided by the concentration of the contaminant in the liquid stream leaving the bottom of the column, C1, can be determined by the equation above where k' is as defined in the equations.

It should be noted that k' is not the same as k given previously in the equations for the a that were discussed in the earlier part of this specification. At any rate, as defined above, k' is equal as follows: k' = (a) (Ww) L 18 G Pv k' =~(a)~ 29 L 760- Accordingly, having the values a, G and L the temperature at which the system is being run and giving you the value of , where Pv is the vapor pressure of water at this temperature, then the value of k' can be determined, where G is gas rate and L is the liquid rate. With the value of k' then the concentration of the contaminant at each theoretical stage can then be determined by utilizing the above equation.

Accordingly, having the particular a, that is, an a for a particular contaminant solvent combination and having a particular gas rate and liquid rate and a particular temperature, there can be determined the k' value for the system and then there can be determined how many theoretical stages are necessary in the packed column to obtain the desired removal of the contaminant from the waste water. A worker skilled in the art can then refer to Perry Chilton's Chemical Engineer's Handbook-Fifth Edition published by McGraw Hill Company, to determine the height of one theoretical stage in the stripper. After this calculation has been completed then the height of the packed column can be determined to give the desired separation of the contaminant from the liquid or water utilizing the number of theoretical stages necessary to carry out the appropriate separation.A theoretical stage would be equal to a certain height in a packed column or approximately equal to one stirred tank or equal to one, whatever means is utilized to contact the water with the air. Then utilizing well known engineering principles, a worker skilled in the art can determine the amount of height in the theoretical stage in the packed column so that the overall height of the packed column is determined or can determine the size and agitation necessary in the stirred tank and/or determine the configuration of other type of means for bringing the air into contact with the water.

It can be appreciated that the above is a specific method for determining the configuration of a packed column for carrying out a certain amount of separation or the desired amount of separation of a contaminant from water. These calculations will vary depending on the contaminant and depending on the gas and liquid system. There may also be variations in the calculations in the column determinations as being necessitated by a particular system and as is well known to a worker skilled in the art.

It should be noted that one advantage of the instant case is that when air is utilized to strip the waste water, the contaminants in the air, as well as the air can be taken and be utilized in an incinerator as the air of combustion. This is, of course, possible if there is an incinerator in the facility. The air may also be utilized as furnace air if the furnace is of sufficient dimensions and in this way the contaminants can be combusted to harmless products, thus, avoiding contamination to the environment.

It should be noted that other gases besides air may be utilized in the process, thus, for instance, there may be utilized an inert gas for the stripping such as, nitrogen or carbon dioxide and the organics recovered from the gas by low temperature condensation of the gas or by absorption of the organics in the low volatile solvent by passing the inert gas through the solvent or by passing the inert gas to an adsorption medium so as to adsorb the organics in the gas on the medium. However, all such processes are more expensive to carry out than, of course, the simple step where the gas is air and the gas is then incinerated, thus, incinerating also the contaminants and effectively rendering them harmless.

Another type of gas that could be utilized as combustible gas, such as natural gas and propane, might then be used as a primary fuel in incinerator or other furnace. One disadvantage of such combustible gas is, of course, that it has to be handled very carefully because of its combustion characteristics.

It is desirable that the air and whatever contacting apparatus is used to contact the air with the water, that the air contact the water for at least 0.5 seconds to carry out the necessary separation of the contaminant from the water into the air. However, generally it is preferred that the liquid have a residence time in the packed column of anywhere from 0.5 to 5 minutes and said gas have residence time in the packed column of from 5 seconds to one minute.

It should be noted that there is nothing critical about the above limitations, they are very general and can vary considerably. The above are given as preferred values for a column in which water is contacted with air to remove a small amount of contaminants from the water in which the pressure drop through the column varies from 0.2 to 0.5 inches of water per foot of packing height.

It should be noted that all of the above values can be changed as desired to build a particular type of column and to separate the desired quantities of contaminants from the water or from any other liquid. For instance, it was said in the above calculations that there be at least 40% removal of contaminants from the waste water. This value does not have to be set at this level.

It could have been set at 60%, 70% or more. The liquid rate was also set as well as the L/G ratio of the above calculations. Any of these values can be changed as desired as well as the temperature at which the stripping is carried out. As these values change, the minimum a value necessary to carry out a specified amount of removal of the contaminant would change and the dimensions of the column, of course, would change.

Accordingly, it is not desirable to hold any of these limitations as being critical in the instant invention. The instant invention being based on the broad disclosure of the invention of the instant case in the showing of the way and means to a worker skilled in the art as to how he may design a column to strip contaminants from a liquid for separation or for purification of the liquid.

There is no criticality in the limits specified above as will be discussed, but the gist of this invention lies in the separation of contaminants from a liquid by stripping the liquid with a gas by the determination of the a value of the contaminant. With the value of the contaminant then the desired column for carrying out the necessary separation can be calculated utilizing the above equations and standard chemical engineering procedures.

Enclosed with this specification is Fig. 3. Fig. 3 is a schematic diagram of a process for purifying waste water utilizing an air packed column in the process. Accordingly, waste water is passed from line 10 into flotation tank 12. Flotation tank 12 has a skimmer 14 with arm 16.

The skimmer arm 16 passes over the surface of the liquid in the flotation tank 12 and skims off any floating dirt into conduit 18, which is passed through line 22 to a suitable receptacle. In flotation tank 12, the water passes through submerged opening 24 of line 28. From line 28, the waste water goes successively through pH adjustment tank 32, then through line 36 to pH adjustment tank 40, then through line 44 to pH adjustment tank 48. The pH adjustment tanks 32, 40 and 48 contain stirrers 50, 54 and 60, respectively.

Into each tank from lime slurry tank 66, passed a neutralizing lime slurry through line 68 into tank 32, through line 72 into tank 40 and through line 76 into tank 48. The lime slurry is added to the pH adjustment tank so as to neutralize as closely as possible the acidity of the waste water. From tank 48, the neutralized waste water is then passed through line 80 into clarifier tank 82. The agitators 50, 54, 60 in tanks 32, 40 and 48, respectively, are used to insure complete mixing of the line slurry with the waste water so as to obtain complete neutralization. It should be noted that a lime slurry need not be utilized. Any other mild base may be added to the waste water that is not deleterious to the environment. A lime slurry is preferred since it is economic and is not deleterious to the environment.Clarifier tank 82 comprises a cone-shaped frame 84, underflow line 86 and weir flanges 90. As a result of a neutralization any sediment that forms in the clarifier tank 82 settles to the bottom of the clarifier tank and is passed out through line 86.

The clarified water passes over weir flange 90 into line 94, where it is transferred into sump tank 96. Sump tank 96 is connected through line 98 to overflow pond 100. From sump tank 96, the cleared waters pass through line 102 through pump 104, through line 106 to the top of stripper column 110. Stripper column 110 comprises an upper section 112, a packing 114 and a bottom reservoir section 118. Clean air passes through line 120, through pump 124, through line 128 into the bottom reservoir, section 118, of packed column 110. The air leaves packed column 110, through line 132, and proceeds to the incinerator to be combusted along with the contaminants therein. The purified water passes out of bottom reservoir, section 118, of packed column 11 0, through line 136 into the back neutralizer tanks 138, 142 and 146.

Acid and specifically, hydrochloric acid is passed through line 150 to back neutralizer tank 138 (the first tank) so as to take care of any alkalinity in the purified water.

As a result the acid preferably HCI is passed from a tank through line 150 to back neutralizer tank 138, so as to completely neutralize the purified water so as to take care of any possible alkalinity in the water as the result of the addition of the lime slurry in pH adjustment tanks 32, 40 and 48. The purified water is then passed through line 154 into a very large tank or pond where the water is allowed to stand for some time so as to allow biological degradation of any remaining impurities in the water as well as to allow sufficient time for precipitation of any other minor amounts of impurities that may be in the water. The water is then ready to be reused or recycled into the environment.

It should be noted that the overflow pond 100 is utilized in case there are at times insufficient amounts of water in sump tank 96. In that case rather than let the stripper column 110 shut down, water will be transferred from the overflow pond 100 into sump tank 96, so as to keep the water going into the stripper column 110, and keep it continuously operating which is more efficient in the instant process.

It should be noted that the process of Fig. 1 for purifying waste water, in addition to the use of the stripper column, is not critical in the instant invention and may be varied as desired. The process of Fig. 1 is the preferred process within the scope of the instant invention, but variations may be made as desired to suit a specific need.

The basic invention of the instant case lies not in an overall process for purifying water, but as has been disclosed in Fig. 1, lies in the definition of a method for removing contaminants from a liquid by stripping the liquid with a gas and more specifically removing contaminants from waste water by stripping the waste water with a gas such as clean air. It should also be noted that the present process is for the purifying of waste water from any chemical plant and not only silicone plants.

The examples below are given for the purpose of illustrating the present invention. They are not given for any purpose of setting limits or definitions to the instant invention.

EXAMPLE 1 Relative volatilities (a) were determined for low concentration aqueous solutions of benzene, toluene, chlorobenzene and m-xylene by the following procedure: (1) An organic solution was prepared in å 161 ml bottle and sealed with a Teflon septum. The quantities used in preparing the solution were: Benzene 35.5 9 Toluene 35.5 g Chlorobenzene 35.5 g m-xylene 35.5 g (2) Measured quantities of distilled water and of the above prepared organic solution were added to a series of 161 ml bottles. Each bottle was then sealed with a Teflon (Registered Trade Mark) septum. After the bottles were shaken for a period of time to promote mixing between the liquid and available gas phase, a 10 microliter sample of the liquid phase was obtained with a micro syringe and immediately injected into a prepared gas chromatograph. The concentrations of each organic component in the liquid sample was determined.

(3) The relative volatility for each component was then calculated from the measured liquid sample concentration with the use of the equation,

C, = initial prepared concentrations of a particular organic specie in the aqueous solution, ppm.

C,, = final measured concentration of a particular organic specie in the aqueous solution, ppm.

V, = volume of liquid in the bottle, ml.

T = temperature of the aqueous solution in the bottle, K.

VPH20 = vapor pressure of water at the temperature of the aqueous solution, Torr.

(4) The following data were recorded in the determination of values: Sample Temperature = 23 C Sample Bottle Volume~161 ml Sample Amount Amount Measured No. H2O, g. Organic Solution, g. C", ppm 1 15.0 1.8X1O-3 9.61 Benzene 9.51 Toluene 13.50 Chlorobenzene 9.83 m-xylene 2 15.0 8 x 10-4 4.68 Benzene 4.90 Toluene 6.51 Chlorobenzene 4.67 m-xylene 3 30.0 9X10-4 4.07 Benzene 4.89 Toluene 5.1 6 Chlorobenzene 4.27 m-xylene 4 30.0 2.1 x10-3 7.78 Benzene 7.94 Toluene 10.15 Chlorobenzene 8.37 m-xylene (5) The average a values calculated from the recorded data were:: Component a (Average of 4 Samples) Benzene 10800 Toluene 10 000 Chlorobenzene 6 100 m-Xylene 10000 EXAMPLE 2 A 6-inch diameter column was packed with 1-inch polypropylene Pall Rings~ to a height of 9 feet 3 inches. A liquid distributor head was placed 2 inches above the top of the packing so that liquid could be uniformly fed to the column cross section. The packing was supported on an open grid structure, near the bottom of the column, that allowed free passage of air up the column and liquid out of the bottom of the packed section. Water with low concentrations of several contaminants was fed at known flow rates to the top of the column and air at known flow rates to the bottom of the column. When steady state was reached samples of the water were taken at the top and bottom of the column simultaneously.These samples were analyzed for the concentration of several contaminants by gas chromatographic techniques. Direct comparison of the sample values allowed the determination of the percent removal for each contaminant for the specific operating conditions in effect at the time of the sampling.

Condition No. 1 Water Temperature 12 C Water Flow Rate 45.1 Ibs/min.

Air Flow Rate 0.86 Ibs/min.

L/G 52.4 Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 17.59 17.28 1.8 Acetone 13.08 12.81 2.1 Benzene 1.64 0.30 81.7 Chlorobenzene 1.35 0.44 67.4 Toluene 3.54 0.64 81.9 m, p Xylene ND* ND o Xylene 0.22 ND *Non Detected (less than 0.05 ppm) Condition No. 2 Water Temperature 12 C Water Flow Rate 45.1 Ibs/min.

Air Flow Rate 1.54 Ibs/min.

L/G 29.3 Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 15.80 15.80 0 Acetone 11.86 11.56 2.5 Benzene 1.49 0.16 89.3 Chlorobenzene 1.28 0.22 82.3 Toluene 3.22 0.37 88.5 m, p Xylene 0.64 0.07 89.1 o Xylene 0.10 ND Condition No. 3 Water Temperature 12 C Water Flow Rate 18.8 Ibs/min.

Air Flow Rate 1.54 Ibs/min.

L/G 12.2 Top Conc. . Bottom Conc.

Component ppm ppm Percent Removal Methanol 41.52 41.17 1.0 Acetone 31.35 30.05 4.0 Benzene 3.93 0.13 96.7 Chlorobenzene 3.45 0.18 94.8 Toluene 8.37 0.32 96.2 m, p Xylene 1.13 0.06 94.7 o Xylene 0.28 ND The foregoing three conditions show the effectiveness of the column for removing the specified organic compounds (benzene, chlorobenzene, toluene, xylene) and the very small removal of methanol and acetone. These data also illustrate the effect of the liquid-to-air flow rate ratio, i.e.

higher removals with lower L/G value. All of these effects are in accordance with the invention disclosed in this application.

EXAMPLE 3 A 6-inch diameter column was packed with 1-inch polypropylene Pall Rings to a height of 5 feet 3 inches. The physical structure and experimental procedure were as described in EXAMPLE 2.

Condition No. 1 Water Temperature 10 C Water Flow Rate 45.1 Ibs/min.

Air Flow Rate 0.86 Ibs/min.

L/G 52.4 Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 7.76 7.20 7.2 Acetone 6.20 5.67 8.5 Benzene 0.88 0.27 69.3 Chlorobenzene 1.49 1.26 56.4 Toluene 3.85 0.65 67.3 m, p Xylene 0.10 0.02 80 o Xylene 0.03 ND Condition No. 2 Water Temperature 10 C Water Flow Rate 18.8 Ibs/min.

Air Flow Rate 1.54 Ibs/min.

L,G 12.2 Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 15.49 14.81 4.4 Acetone 13.26 12.55 5.4 Benzene 1.97 0.23 88.3 Chlorobenzene 3.07 0.58 81.1 Toluene 8.78 1.19 86.5 m, p Xylene 0.25 0.02 92.0 o Xylene 0.10 ND Condition No. 3 Water Temperature 10 C Water Flow Rate 18.8 Ibs/min.

Air Flow Rate 0.86 Ibs/min.

L/G 21.9 Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 16.81 16.76 0.3 Acetone 13.51 13.18 2.4 Benzene 2.04 0.33 83.8 Chlorobenzene 3.54 0.84 76.3 Toluene 8.86 1.57 82.3 m, p Xylene 0.25 0.04 84.0 o Xylene 0.10 ND Condition No. 4 Water Temperature 10 C Water Flow Rate 45.1 Ibs/min.

Air Flow Rate 1.54 Ibs/min.

L/G 29.3 Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 6.91 7.06 - Acetone 6.64 6.45 2.9 Benzene 0.92 0.22 76.1 Chlorobenzene 1.41 0.47 66.7 Toluene 3.66 0.97 73.5 m, p Xylene 0.08 ND o Xylene ND ND **Negative numbers due to small experimental errors.

Condition No. 5 Water Temperature 10 C Water Flow Rate 57.6 Ibs/min.

Air Flow Rate 0.86 Ibs/min.

LIG 67 Top Conc. ~ Bottom Conc.

Component ppm ppm Percent Removal Methanol 7.90 8.07 - 2.2* Acetone 6.24 6.25 - 0.2* Benzene 0.94 0.44 53.2 Chlorobenzene 1.46 0.91 50.7 Toluene 3.85 1.90 37.7 m, p Xylene 0.09 0.04 55.6 o Xylene 0.02 ND **Negative numbers due to small experimental errors.

Condition No. 6 Water Temperature 40 C Water Flow Rate 45.1 Ibs/min.

Air Flow Rate 1.54 Ibs/min.

LIG 29.3 Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 11.10 11.02 0.5 Acetone 9.27 8.49 8.4 Benzene 1.41 0.04 97.2 Chlorobenzene 1.49 0.04 96.5 Toluene 4.26 0.15 97.3 m, p Xylene 0.10 ND o Xylene ND ND Condition No. 7 Water Temperature 40"C Water Flow Rate 45.1 Ibs/min.

Air Flow Rate 0.43 Ibs/min.

LIG 105 Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 23.81 23.37 1.9 Acetone 15.61 15.03 3.7 Benzene 1.55 0.20 89.9 Chlorobenzene 1.42 0.22 84.5 Toluene 3.27 0.30 90.8 m, p Xylene 0.12 0.03 75 o Xylene ND ND EXAMPLE 4 A 6-inch diameter column was packed with 1-inch polypropylene Intalox Saddles to a depth of 9 feet 2 inches (total number of pieces in column was 2,923). The physical structure and experimental procedure were as described in EXAMPLE 2.

Condition No. 1 Water Temperature 5 C Water Flow Rate 25.1 Ibs/min.

Air Flow Rate 0 Ibs/min.

LIG Co Pressure Drop 0 across Column Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 18.90 19.23 ~0.33 Acetone 16.89 15.76 6.69 Benzene 1.73 1.76 -1.73 Chlorobenzene 1.75 1.76 -0.94 Toluene 4.26 4.30 - 0.57 m, p Xylene 0.47 0.46 2.13 o Xylene 0.19 0.19 This experiment, with zero air flow, demonstrates the reliability of the procedures and analyses.

Theoretically, the percent removal should have been zero for all components. The slight deviations from zero attest to the reliability of the study.

Condition No. 2 Water Temperature 5 C Water Flow Rate 25.1 Ibs/min.

Air Flow Rate 0.43 Ibs/min.

L/G 58.4 Pressure Drop < 0.1 inches H2O across Column Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 20.38 20.19 0.9 Acetone 17.79 17.86 -0.4 Benzene 1.94 0.65 66.5 Chlorobenzene 1.92 1.00 47.9 Toluene 4.79 1.74 63.3 m,pXylene 0.51 0.19 62.8 o Xylene 0.21 0.08 61.9 Condition No. 3 Water Temperature 5 C Water Flow Rate 25.1 Ibs/min.

Air Flow Rate 1.54 Ibs/min.

L,G 16.3 Pressure Drop 0.45 inches across Column Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 19.71 19.40 1.6 Acetone 17.82 16.86 5.4 Benzene 2.00 0.30 85.0 Chlorobenzene 1.98 0.42 78.8 Toluene 4.91 0.82 83.3 m, p Xylene 0.52 0.08 84.6 o Xylene 0.22 0.03 86.4 Condition No. 4 Water Temperature 5 C Water Flow Rate 25.1 Ibs/min.

Air Flow Rate 3.4 Ibs/min.

L,G 7.4 Pressure Drop 3.4 inches H2O across Column Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 19.28 18.75 2.8 Acetone 18.38 16.69 9.2 Benzene 2.21 0.16 92.8 Chlorobenzene 2.18 0.22 89.9 Toluene 5.48 0.47 91.4 m, p Xylene 0.55 0.04 92.7 o Xylene 0.23 ND EXAMPLE 5 A 6-inch diameter column was packed with 8 feet 2 inches of number 1 polypropylene Telleretleso (1582 pieces) plus 1 foot (366 pieces) of 1-inch polypropylene Intalox Saddles on the top. The physical structure and experimental procedure were as described in EXAMPLE 2.

Condition No. 1 Water Temperature 10 C Water Flow Rate 41.8 Ibs/min.

Air Flow Rate 0.43 Ibs/min.

LIG 97.2 Pressure Drop 0.1 inches H20 across Column Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 18.56 17.98 3.1 Acetone 12.28 11.79 4.0 Benzene 1.74 0.61 64.9 Chlorobenzene 1.85 0.92 50.0 Toluene 4.96 1.86 62.5 m, p Xylene 0.59 0.21 64.0 o Xylene 0.26 0.08 69.0 Condition No. 2 Water Temperature 10 C Water Flow Rate 25.1 Ibs/min.

Air Flow Rate 1.13 Ibs/min.

LIG 22.3 Pressure Drop 0.2 inches H2O across Column Top Conc. Bottom Conc.

Component ppm ppm Percent Removal Methanol 11.77 12.15 - 3.2 Acetone 7.81 7.59 2.8 Benzene 0.92 0.12 87.0 Chlorobenzene 1.41 0.24 83.0 Toluene 3.35 0.49 85.4 m, p Xylene 0.42 0.06 85.7 o Xylene 0.18 ND

Claims (22)

1. A process for removing contaminates from waste water comprising (1) passing a first stream of a gas into contact with a second stream of waste water having therein as contaminants, a compound selected from the class consisting of: allyl bromide; allyl chloride; amyl chloride; amylene; benzene; butadiene; butene; butyl bromide; butyl chloride; butyl iodide; butyl methacrylate; butylene; chlorobenzene; cyclohexyl amine; dibutyl ether; dimethyl carbonate; dimethyl sulfide; furfuran; heptane; hexane; isoprene; methyl chloride; octene; pentane; pyrrole; tetrachloroethane; tetrachloroethylene; toluene; 1, 1, 1trichloroethane; trichloroethylene; vinyl chloride; xylene; 1, 1 -dibromoethylene; 1, 2-dibromoethylene (cis 8 trans); allyl acetate; iso amyl ether; 3-bromo-propene-1; diallyl ether; allyl formate; 3-iodo-propene-1; triuretdiamidine; 2-bromo-2-methyl butane; 1 -bromo-2, 2-dimethyl propane; 1-bromo-2-methyl butane; n-butyrate (n); n-caproate (iso); 1-chloropentane; 2-chloropentane; 3chloropentane; 4-chloro-2-methyl butane; 3-chloro-2 methyl butane; 2-chloro-2 methyl butane; 1-chloro-2 methyl butane; 2-odopentane; 2-iodo-2 methyl butane; 4-iodo-2 methyl butane; 1iodopentane; pentanthiol-1; pentanthiol-3; 2-methyl butanthiol-4; pentene-1; 2-methyl-butene-3; 2-methyl-butene-1; benzene; phenyacyl bromide; butadiene (1, 2); butadiene (1, 3); butane (n); butane (iso); butyl acetate (tert); 1-bromo-butane; 2-bromo-butane; 1-bromo-2 methyl propane; 2-bromo-2 methyl propane; 1-chloro butane; 2-chloro butane; 1-chloro-2 methyl propane; 2chloro-2 methyl propane; 2-iodo-2 methyl propane; butene-1; butene-2 (cis 8 trans); butyne-2; dimethyl chloroarsine; carbon disulfide; carbon monoxide; tetrachloromethane; tetrafluorometh ane; tetraiodomethane; chloroethyne; phenylchloride (chlorobenzene); chlorobromoethane (1, 1); chlorobromoethane (1, 2); chlorobromomethane; 1-chloro-2 butanone; 1, 1 chloronitroethane; crotyl chloride; isocrotyl chloride; cyclobutane; cycloheptane; cycloheptene; cyclohexadiene (1, 3); cyclohexadiene (1, 4); cyclohexane; cyclopentadiene (1, 3); pentane; propane; 1, 1 dibromoethane; 1, 2 dibromoethane; 2, 2 dichloroethanol; 1, 1 dichlorobutane (n); 1, 1 dichloroethane; 1, 2 dichloroethane; 1, 1 dichloroethene; dichloroiodomethane; 1, 1 dichloro-1 nitromethane; 1, 1 dichloro-1 -nitrosoethane; 2, 3 dichloropentane; 2, 4 dichloropentane; 2, 3 dichloro-2 methylbutane; 4, 4 dichloro-2 methylbutane; 1, 2 dichloropropane; 1, 3 dichloropropane; 2, 2 dichloropropane; 1, 1 dichloropropionitrile; 1, 1 dichloropropene-1; 1, 2 dichloropropene-1; 1, 2 dichloropropene-2; 1, 3 dichloropropene-1; 2-ethylbutyraldehyde; diethyl carbonate; diethyl monoselinide; diethyl sulfide; diethyl telluride; 1, 1 difluoro-1, 2 dibromoethane; 1, 1 difluoro-2, 2-dichloroethane; 1, 1 difluoro-2 iodoethane; 1, 1, 1, 2 tetrachloro-2, 2difluoroethane; 1, 1, 2, 2 tetrachloro-1, 2 difluoroethane; dimethylcyclohexane (o); dimethylcyclohexane (m); dimethylcyclohexane (p); 1, 5 dimethyl-2, 5 hexadiene; dimethylphosphine; dimethyl selenide; dimethyl sulfide; di-isopropyl ether; n-iso-propyl ether; ethane; ethyl allyl ether; ethyl amyl ether; ethyl arsine; ethyl benzene; n-butyl ethyl ether; iso-butyl ethyl ether; tert-butyl ethyl ether; ethyl n-butyrate; chloroethane; ethylhydroselenide; iodoethane; ethyl methyl acrylate; ethyl thioacetate; ethyl isothioacetate; ethyl isovalerate; fluorobenzene; fluorodichloromethane; o fluorotoluene; m fluorotoluene; p fluorotoluene; 1, 1, 2 trichloro-l4luoroe- thane; trichlorofluoromethane; furan; glycol dinitrite; 2-methyl hexane; n heptane; 3-methyl hexane; 2, 2 dimethyl pentane; 2, 4 dimethyl pentane; 3, 3 dimethyl pentane; 3 ethyl pentane; 2, 2, 3 trimethyl pentane; heptene-1; 2, 4 dimethyl pentene-2; 2, 4 hexadiene; 1, 5 hexadiene; n hexane; 2-methyl pentane; 2, 2 dimethyl butane; 2, 3 dimethyl butane; 3 methyl pentane; hexyl alcohol; 1 chlorohexane; 2 chlorohexane; n hexyl nitrate; 1 hexene; 2, 3 dimethyl butene 1; 3, 3 dimethyl butene 1; n butyl methyl ether; isobutyl methyl ether; isopropyl acetylene; methyl crotonate; methyl cyclohexane; methyl cyclohexene; methyl cyclopentane; methyl cyclopropane; 2-methyl butanol-1; methyl ethyl carbonate; methyl ethyl sulfide; methyl phosphine; methyl propionate; methyl pyrrole (1); all octane isomers; all octene isomers; n pentane; 2 methyl butane; 2, 2 dimethyl propane; pentyne-1; pentyne-2; 1-chloro propene-1; 2-chloro propene-1; 1-bromopropane; 2-bromopropane; isopropyl chloroformate; n propyl cyanide; isopropropyl cyanide; n propropnyl chloroformate; tetramethyl silicon; 1, 1, 2, 2 tetrachlorethane; 1, 1, 1, 2 tetrachloroethane; tetrachloroethylene; tetranitromethane; thiophene; toluene; 1, 1, 1 trichloroethane; 1, 1, 2 trichloroethane; trichloroethylene; triethyl silicon hydride; 1, 1, 2 trichloroethane; trimethyl phosphine; vinyl bromide; vinyl chloride; vinyl fluoride; m xylene; p xylene; o xylene; chloromethane; dichloromethane; trichloromethane; 1, 1, 1, 2, 2 pentachloroethane; hexachloroethane; 1, 2 dichloroethylene (cis 8 trans); 1, 1, 2 trichloroethylene; 1, 1, 2, 3 tetrachloropropane; 1, 2, 2, 3 tetrachloropropane.

and mixtures thereof, and (2) separating a third stream of said waste water from said gas which has a smaller amount of contaminants than said second stream and removing a fourth stream of said gas from said waste water having said contaminants therein.

2. The process of Claim 1 wherein said gas is air.

3. The process of Claim 1 wherein said gas is contacted with said waste water at a temperature in the range of 0 to 95 C.

4. The process of Claim 1 wherein said gas is contacted with said waste water for at least 5 seconds.

5. The process of Claim 3 wherein said gas is contacted with said waste water at a temperature in the range of O to 60do.

6. The process of Claim 1 wherein said gas is contacted with said waste water in a packed column.

7. The process of Claim 6 wherein said packed column is defined by the fact that there is a rate in said column of'5,000 to 30,000 pounds per square foot per hour of waste water wherein the L/G ratio varies from 5 to 100, where L is pounds of liquid going into the column per square foot per hour and G is pounds of gas going into the column per square foot per hour wherein the contact between the waste water and gas takes place at a temperature of at least 0 C and there is at least 40% by weight removal of the contaminants in said waste water and wherein the a of the contaminant is at least 0.64 where the minimum a is for a temperature of 95 C, and 1 atmosphere pressure and an L/G ratio of 5, and a is defined by the equation: : (concentration of contaminant vapor/conc. of water vapor) in gas phase (conc. of contaminant liquid/concentration of water liquid) in liquid phase

8. The process of Claim 7 wherein said residence time for said waste water in said column varies from 0.5 to 5 minutes and said gas varies from 5 seconds to 1 minute.

9. The process of Claim 8 wherein the removal of the contaminant from said waste water is 99.99% by weight.

10. The process of Claim 8 wherein said second stream of waste water is first passed into a flotation tank to remove floating impurities and is then passed into pH adjustment tanks where a mild base is added to neutralize any acid in the waste water.

11. The process of Claim 10 wherein after said pH adjustment tanks said second stream of waste water is passed into a precipitation tank wherein any precipitation that is formed from the addition of the base is deposited and then the second stream of waste water is passed into said packed column.

12. The process of Claim 11 wherein after said third stream of waste water is removed from said packed column, it is passed into a neutralizer tank wherein it is neutralized with an acid and then can be passed back into the environment.

13. A process for removing contaminants from waste water comprising (1) passing a first stream of a gas into contact with a second stream of waste water containing the contaminant in a packed column where the packed column is defined by that there is a flow rate of said second stream of waste water of 5,000 to 30,000 pounds per square foot per hour wherein the L/G ratio values from 5 to 100, where L is pounds of liquid going into the column per square foot per hour and G is pounds of gas going into the column per square foot per hour wherein the temperature of said packed column is maintained at least at 0 C and there is at least 40% by weight removal of the contaminants in said waste water in said packed column, and wherein the a of the contaminant is determined from:: (concentration of contaminant vapor/conc. of water vapor) in gas phase a (conc. of contaminant liquid/concentration of water liquid) in liquid phase and from the foregoing value of a the size of the packed column can be determined wherein the value of a must be at least 0.64 where the minimum value of a is for a temperature of 95 C, and 1 atmosphere pressure and an L/G ratio of 5, and (2) removing a third stream of said waste water from said packed column from which at least 40% of the contaminants have been removed and removing a fourth stream of said gas from said column, said gas having said contaminants therein.

14. The process of Claim 13 wherein said gas is air and wherein said fourth stream of air is passed into an incinerator as air of combustion.

15. The process of Claim 13 wherein the contaminant is selected from the class consisting of allyl bromides, allyl chloride, amyl chloride, amylene, benzene, butadiene, butene, butyl bromide, butyl chloride, butyl iodide, butyl methacrylate, butylene, chlorobenzene, cyclohexyl amine, dibutyl ether, dimethyl carbonate, dimethyl sulfide, furfuran, heptane, hexane, isoprene, methyl chloride, octene, pentane, pyrrole, tetrachloroethane, tetrachloroethylene, toluene, 1, 1, 1-trichloroethane, trichloroethylene, trifluorotrichloroethane, vinyl chloride, xylene and mixtures thereof.

16. The process of Claim 15 wherein said residence time for said waste water in said column varies from 0.5 to 5 minutes and said gas varies from 3 seconds to 1 minute.

17. The process of Claim 13 wherein the removal of said contaminant from said waste water is 99.99% by weight.

18. The process of Claim 13 wherein said second stream of waste water is first passed into a flotation tank to remove floating impurities and is then passed into pH adjustment tanks where a mild base is added to neutralize any acid in the waste water.

19. The process of Claim 18 wherein after said pH adjustment tanks said second stream of waste water is passed into a precipitation tank wherein any precipitate that is formed from the addition of the base is deposited and then the second stream of waste water is passed into said packed column.

20. The process of Claim 19 wherein after said third stream of waste water is removed from said packed column, it is passed into a neutralizer tank wherein it is neutralized with an acid and then can be passed back into the environment.

21. A process for removing contaminants from waste water comprising (A) passing a first stream of waste water into a flotation tank to remove floating impurities and then transferring said first stream into a pH adjustment tank where a mild base is added to neutralize any acid in the waste water; (B) then transferring said first stream of waste water into a precipitation tank wherein any precipitate that is formed from the addition of the base is deposited; (C) transmitting said first stream of waste water to a packed column and passing a second stream of air into said packed column in contact with said waste water where in said packed column it is defined that there is a rate of said first stream into said column of 5,000 to 30,000 pounds per square foot per hour wherein the L/G ratio varies from 5 to 100, where L is pounds of liquid going into the column per square foot per hour, and G is pounds of gas going into the column per square foot per hour wherein the temperature of said column is maintained at least at O C, and there is at least 40% by weight removal of the contaminants in said waste water in said packed column and wherein the a of the system is determined by the equation:: (concentration of contaminant vapor/conc. of water vapor) in gas phase (conc. of contaminant liquid/concentration of water liquid) in liquid phase and from the foregoing value of a the size of the packed column can be determined wherein the value of a must be at least 0.64 where the minimum value of a is for a temperature of 95 C, and 1 atmosphere pressure and an L/G ratio of 5; (D) removing a third stream of said waste water from said packed column wherein from which at least 40% of the contaminants have been removed; (E) removing a fourth stream of air from said column, said air having said contaminants therein and passing said air into an incinerator, and (F) transferring said third stream of waste water into a neutralizer tank and neutralizing it with an acid.

22. A packed column for removing contaminants from waste water comprising a packed column of sufficient diameter and height capable of removing contaminants from waste water wherein there is passed a first stream of gas into contact with the second stream of waste water containing the contaminant in the packing of the packed column where the packed column is defined by the fact that there is a flow rate of said second stream of waste water into and out of the packed column of from 5,000 to 30,000 pounds per square foot per hour where the L/G ratio varies from 5 to 100, where L is pounds of liquid going into the column per square foot per hour, and G is pounds of gas going into the column per square foot per hour wherein the temperature of said packed column is at least at 0 C, there is at least 40% by weight removal of the contaminants in said waste water in said packed column, and wherein the a of the contaminant that is removed from the waste water is determined from the equation: (concentration of contaminant vapor/conc. of water vapor) in gas phase (conc. of contaminant liquid/concentration of water liquid) in liquid phase and from the foregoing value of the a, the size of the packed column can be determined, wherein the value of a must be at least 0.64 which is the minimum value of a for a temperature of 95% and 1 atmosphere pressure and an L/G ratio of 5; and the packed column operates such that there is removed from the packed column a third stream of waste water from said packed column from which at least 40% of the contaminants have been removed and removing a fourth stream of said gas from said packed column wherein said gas contains the contaminants that have been removed from the waste water.