WO2009131615A2 - Process for decontamination of inorganic hazardous components from a waste stream - Google Patents

Abstract

Organic material containing waste streams are treated to remove inorganic hazardous components. Waste volumes generated from laboratory procedures are collected and amassed. The collected volume is treated with ozone in a manner and at conditions capable of reducing the concentration of the hazardous inorganic components to or below a required concentration.

Description

PROCESS FOR DECONTAMINATION OF INORGANIC HAZARDOUS COMPONENTS FROM A WASTE STREAM

Cross Reference to Related Application and Priority Claim

This application claims the benefit under 35 U. S. C. § 119(e) of copending U.S. Provisional Application Serial No. 61/047175, entitled SODIUM AZIDE REMOVAL FROM LAB WASTEWATER filed on April 23, 2008, which is hereby incorporated by reference in its entirety.

Field of the Invention

The present invention relates to a method of removing an inorganic hazardous component from a waste solution. More specifically, but without limiting the teachings of this invention, the present invention is directed to removal of sodium azide from laboratory waste solutions such as those resulting from diagnostic testing of blood serum.

Background of the Invention

Sodium azide is a common preservative used in laboratories for stock solutions and samples. Manufacturers use sodium azide in many in vitro diagnostic products. It can be found in the diluents used for automatic blood cell counters, for example, in concentrations up to about 0.1%.

Sodium azide, NaN3, CAS number 26628-22-8 is a colorless, odorless, crystalline solid, a salt, that is highly toxic and a severe explosive risk if shocked or heated. Sodium azide and hydrazoic acid (HN3, formed from NaN3 in water) are hazardous because they produce hypotension (low blood pressure) in laboratory animals and humans. In addition, they form strong complexes with hemoglobin and block oxygen transport to blood.

Acute inhalation of HN3 vapor by humans results in lowered blood pressure, bronchitis, eye, nose, throat, and lung irritation, headache, weakness, and collapse. A skin designation has been assigned to the OSHA PEL due to the ability of NaN3 to readily penetrate intact skin, and any dermal exposure can significantly contribute to the overall exposure to sodium azide. Target organs are eyes, skin, lungs, central nervous system, cardiovascular system and kidneys. Sodium azide has high toxicity to bacteria is water treatment plants.

Many regulatory agencies prefer that sodium azide be deactivated at the location of use, rather than be transported to another location. This minimizes chances of human or environmental exposure by spillage during transport, aerosol formation, or incomplete deactivation. It also will reduce the risk of damage to water treatment facilities.

Treatment of azide waste is described in US patent 5,073,273, where an alkaline slurry of gas producing azide particles used in automobile air bags is treated by ozone.

Summary of the Invention

In an embodiment, the method provides for the decontamination of a liquid waste solution by the degradation of one or more hazardous components in the solution by contact with ozone. The liquid waste solution can be, but is not limited to, one of the following examples; laboratory stock solutions, waste from in vitro test kits, diluents used for automatic blood cell counters, or other biological laboratory solutions.

In an embodiment, the hazardous component is an azide of the formula, XN3, where X is an alkali metal. In an embodiment, the hazardous component is sodium azide.

In an embodiment, the method comprises collecting waste solutions from one or more laboratory procedures in a holding tank. The tank has a level sensor or other device that is preset to a value which when attained sends a signal to a programmable logic controller, which in turn initiates a transfer pump to transfer the composite waste solution of the various additions to a treatment tank. Once the treatment tank has reached a preset level, a recirculation pump is started to continuously recirculate the waste solution and ozone is added at a predetermined rate and concentration.

In a version of the embodiment, the ozone addition to the treatment tank at a predetermined rate and concentration is started when the transfer pump starts adding waste solution to the treatment tank, or at some intermediate time between start of that transfer and start of the recirculation.

In an embodiment, the method as described additionally comprises an oxidation reduction potential (ORP) sensor, which provides for measurement of ORP, either continuously, or at intervals, or at a predetermined end of cycle time. If the ORP measurement shows that the hazardous component or components are below a desired concentration, preferably reduced to or below a non-detectable level, the contents of the treatment tank are diverted to a waste disposal stream.

Brief description of the Drawings

The features and advantages presented in the full description will be more apparent with respect to the following drawing, which are presented by way of example and not to be taken as limiting the description. The figure are simplified illustrations of the equipment, instrumentation, etc., used to perform the described method, and are not to scale, and are meant to illustrate the main features of the method.

Figure 1 illustrates a simplified process flow for the method of the current invention.

Detailed Description of the Invention

The following description uses as an example the degradation of the hazardous chemical sodium azide using ozone injection to decontaminate a composite waste solution comprising multiple volumes of waste resulting from multiple diagnostic tests of blood serum. The descriptive example is provided to give a clear and understandable depiction of the method and not to limit any embodiment of the invention. It is to be expected that one skilled in the art of waste removal, remediation or decontamination will be able to adapt the teachings provided herein to other cases in order to effect removal of one or more inorganic hazardous components or materials.

Inorganic refers to chemicals generally classified as inorganic chemicals. These are chemicals or compounds that are not hydrocarbons and their derivatives, or are not compounds of carbon disulfide. Although there is some overlap between inorganic and organic chemicals, one skilled in the chemicals arts will understand the meaning of inorganic as used here.

Any regulatory agencies want compounds such as sodium azide disposed of where they are used rather than shipping waste solutions to an off-site disposal facility. In the case of substances such as sodium azide, it is preferred that handling and transfer by personnel be minimized. For this reason, a closed, automated system or process is preferred. Organic matter in the waste stream increases the difficulty of decontamination and destruction of the sodium azide or other hazardous inorganic components of the waste stream. Organic matter includes natural and synthetic organic chemicals, proteins, cells and cell debris, DNA molecules and other components of blood or bodily fluids. These organic materials are variable in type and amount from batch to batch, and among different operating sites. Competition between the hazardous component and the organic matter for ozone reduces the effectiveness of inorganic destruction. This effect is accentuated by the discrepancy in concentration, since the organic matter is usually in much higher concentration. Further, as the concentration or the inorganic component is reduced, the law of mass action dictates that the ozone is more likely to react with the organic matter. This effect increases the time needed for the reaction and destruction of the last vestiges of the hazardous component. Given enough time and ozone, the reaction with the inorganic hazardous component would go to completion, i.e., to non-detectable levels. However, for practical and economic reasons, a preferred processing time is in the range of 30 - 120 minutes, more preferably 60 - 75 minutes after the treatment tank is filled, or at the point where no further waste solution is added.

In the case of sodium azide and similar materials, organic materials in the waste stream pose an additional problem. Reaction of organic materials with ozone may generate organic acids, which may reduce the alkalinity of the waste solution. It is well known that it is preferable to maintain the pH of sodium azide solutions above 9, more preferably above 10 to prevent the formation of dangerous hydrazoic acid vapors.

For these reasons, it was necessary to develop a process that would allow destruction of the hazardous inorganic component in the presence of excess organic materials in the desired process time.

In facilities that use sodium azide as a preservative for test samples, such as diluents used for automatic blood cell counters, the test volumes generated are sent to a container, such as a closed tank, to be collected and amassed until an efficient and economical decontamination can be done. It is further preferable that the decontamination be as benign as possible; at the least, not to add substances that require further treatment over what the waste solution after removal of the hazardous component of interest. The embodiments described herein provide several variations of a solution to this problem.

A decontamination process for a hazardous component of a waste stream removes, degrades, decomposes or otherwise renders the hazardous component(s) innocuous or sufficiently safe for handling or transfer so that the waste stream can be safely sent to a waste disposal facility. In this context, decontamination, degradation, removal, or similar terms refers to changing the hazardous component to an innocuous or relatively harmless substance. The resultant concentration of hazardous component remaining after such treatment will vary with the danger posed by the component, and the requirements of the controlling agency. In many cases, such as with sodium azide, removal to below detectable limits is required or preferred.

Waste disposal facility includes as examples contained landfills, solid waste incinerators, waste-to-energy facilities, or hazardous waste incinerators, landfills, or other sites or facilities for the land disposal of hazardous waste.

The terms "below detectable limits" or 'non-detectable" or similar terms refer to the results of analytical tests or method in which the results are at or below the lowest concentration of the component being measured by the analytical method that can be confirmed by approved methods.

Figure 1 illustrates an embodiment of the process. Holding tank 1 serves to collect and amass the samples or other volumes of solution to be decontaminated sent from one or more test facilities, laboratories or other sources. The source volumes can be piped from the various sources, as shown by inlet 2, or collected at the source in a container and carried to tank and emptied therein. While not required, Tank 1 will normally be sized to contain the volume generated in a day, with a suitable safety factor, so that decontamination can be done once a day, usually when there is an ebb in the activity of the facility.

The holding tank has a level sensor 3 which is connected to a programmed logic controller (PLC). In the description herein, the terms " connected" or "connection" used with sensors and PLCs means that the devices and instruments can communicate via the connection and send signals and instructions between them. Tank 1 has an optional agitator or other stirring device 4 to keep the waste solution homogeneous, and if solids are present, to prevent sludge formation which could impede transfer. The device can be any suitable, as known to those skilled in the art, such as propeller or other stirrers, perpendicular or slanted as desired, with or without baffling, A recycling pump may also be used, either a separate pump, or the transfer pump 6. Gas bubbling may also be used, particularly if anaerobic, or aerobic disposal of a portion of the waste solution is desired to be accomplished prior to other process steps.

Level monitoring device 3 is connected to a common programmable logic controller 5 (PLC), which in turn is connected to send a signal to transfer pump 6. When the level of waste solution in Tank 1 reaches a preselected level, i.e., "Full", the level sends a signal to the PLC which signals the pump to start and to transfer the waste solution to Treatment Tank 8. The level monitor 4 will send a signal when the level has reached a low level, i.e., "Empty", to prevent cavitation, foaming or other deleterious effects. Tank 1 may have a quick-start feature, which allows the operator to transfer the waste solution before filling. For example, on a day where there is a low amount sent to Tank 1 and the protocols requires a daily transfer and decontamination.

Tank 8, the treatment tank, contains a level monitor 9 connected to PLC 10. This can be set to send a signal to PLC 10 when the level has reached a preselected level. PLC 10 then sends a signal to initiate the ozone injector. In practice, the injector can start when the treatment tank is full, or when the level has reached some minimum value so that the reaction can occur while filling continues. The level sensor also sends a signal to initiate the recycle pump. This pump can start with the ozone injection, or before injection to help disperse the ozone, or can be initiated after injection commences, in order to prevent cavitation, foaming, etc.

The injector 11 is shown entering the tank. An alternative position is to have the indictor located at the exit of the recycle pump 16, in order to maximize initial dispersion of the ozone.

Tank 8 may have an optional agitator or stirrer 12 or other device or method to maintain the waste solution homogeneous, as was described for Tank 1. An oxidation reduction sensor 13 is located in tank 8. This sensor measures the oxidation reduction potential (ORP) of the waste solution. The ORP is related to the amount of sodium azide in the waste solution, as will be described in the Experimental section below. In an optional step of the process, once the ORP reaches a preselected value indicating the decontamination has reached a desired level, preferably to a non-detectable level of the hazardous component; valve 15 is switched to divert the pump output to a waste disposal facility, or a storage facility for further processing or transport.

An alternative method is to have the source volumes go directly to Tank 8. The process would be as described, except the tank will be preferably filled before injection starts. The advantage of this method is to reduce capital equipment and process steps. A possible disadvantage is that sending source volumes to the tank will be curtailed during processing. This may be overcome by operating on off-shifts, or other operational planning.

It will be apparent to those skilled in the art of waste decontamination and disposal that the conditions required to decontaminate a waste stream will depend on the specific process being considered. Among the process variables to be considered, the type and concentration of contaminant, the amount and variety of organic material, the volume of the tanks and the throughput (i.e., volumes per time) will all determine the exact conditions needed. The description given and the examples described are meant to be guidelines for those skilled in the art, and are not meant to be limiting in any manner.

Examples

Waste solutions were collected from an Advia 1800 automated chemical system and a Centaur immunoassay instrument, both products of Siemens Medical Solutions. The instruments were being operated in a hospital laboratory. After 1.25 hours, seventeen (17) liters of waste were collected from the Advia, and one (1) liter from the Centaur. These were combined and treated in a two tank system as described. The ozone generator supplied 1.5 gram/hour/liter ozone for all tests. Sodium azide concentrations were analyzed by ion chromatography.

ORP is the value reported by a Siemens High Resolution Redox® (HRR®) oxidation reduction sensor. This sensor is used to measure the oxidation reduction potential (ORP) of the waste stream solution. Before ozone addition, the ORP is usually under 100. As oxidation proceeds, the value rises.

COD stands for chemical oxygen demand, which is a measure of the amount of oxygen consumed when organic matter is decomposed and inorganic material such as azides are oxidized. It is a common test to indirectly indicate or measure the amount of organic matter in water.

A one liter sample was treated and the conditions and results are shown in Table 1 below.

TABLE 1

*Non-detectable

In this small volume test, sodium azide was removed to below detection limits in 15 minutes. The decrease in COD and the associated decrease in pH indicate the destruction of organic matter, presumably forming organic acids which reduce pH.

A second test was done with a 17 liter volume being treated. The conditions and results . are shown in Table 2 below. TABLE 2

These results show the same trends as for the smaller volume test, but azide removal was not to non-detectable limits in 180 minutes.

Further experimentation was done with a 400 liter system at a different location. Initial trials on waste water streams containing organic matter and sodium azide showed that sodium azide was removed as expected, but non-detectable levels were not reached in 60- 75 minutes, the preferred time. Considerable analysis of operating conditions led to increasing oxygen flow to the ozone generator in order to raise ozone output. Even so, until the oxygen pressure was adjusted, the ozone content was not high enough to reach the desired results. Further experimentation on control of the water flow rate to the injector also increased effectiveness of the process.

Ozone was generated with a Guardian PB (Cocoa, FL) corona discharge generator. Ozone generating capacity in the range of about 36 to 72 gram per hour was preferred. Oxygen feed to the ozone generator of about 95% or greater was preferred for this process. Oxygen flow rates of about 12 scfm (standard cubic feet per minute) (339 liters/minute) at about 7-8 psi (48.2 - 55.2 KPa) were found to be preferred after experimentation.

Ozone was injected into the treatment tank using a Mazzei 584 injector. These injectors are high-efficiency, venturi-type, differential pressure injectors with internal mixing vanes. They comprise an in-line liquid inlet and outlet and a second inlet (suction port) perpendicular to the liquid inlet and outlet and located between them. When a sufficient pressure difference exists between the inlet and outlet ports of the injector, a vacuum is created inside the injector body, which initiates suction of a liquid or gas, here the ozone generated, through the suction port, and provides mixing with the liquid flowing from inlet to outlet. For the 400 liter treatment tank, a recycle flow of 4 gallons per hour (15.2 liters/hour) was found to be satisfactory.

In order to maximize the effectiveness of the ozone addition, the ozone injection was started approximately coincident with the transfer of the waste from the holding tank to the treatment tank. This increased the ratio of ozone concentration to sodium azide for the initial portion of the treatment, and gave a "head start" to the overall process. Results are shown in Tables 3 and 4 below.

TABLE 3

TABLE 4

The result in Tables 3 and 4 show that sodium azide is removed in the preferred treatment time of 60 -75 minutes from the filling of the treatment tank. One can infer from the varying ORP starting values that the initial feed streams differ in type and amount of organic waste. This is to be expected, as the number and type of tests run in hospital and life science laboratories will vary from day to day and from one laboratory to another. Despite the interference of varying organic matter, the process can provide for removal of sodium azide to below detection limits. Furthermore, the ORP values where sodium azide is not detected is approximately 50 -70 for the tests shown in Tables 1 and 2, and 129 to 177 for those in Tables 3 and 4. It should be possible therefore, to set an upper ORP value that will within a safety limit, provide a quick and efficient to determine when a non-detectable level of sodium azide has been reached. This could be used to stop the process and transfer the treated stream to disposal, or to signal for an analytical test to determine sodium azide presence. One skilled in the art will be able with routine experimentation to adapt these findings to other analogous situations for sodium azide removal, or to removal of oxidizable inorganic components from an organic matter containing waste stream.

A practitioner skilled in the art of waste removal, remediation, disposal or decontamination will be able to discern the advantages of the present invention. It is not the intent of the discussion of the present invention to exhaustively present all combinations, substitutions or modifications that are possible, but to present representative methods for the edification of the skilled practitioner. Representative examples have been given to demonstrate reduction to practice and are not to be taken as limiting the scope of the present invention. The inventor seeks to cover the broadest aspects of the invention in the broadest manner known at the time the claims were made.

Claims

What is Claimed Is:

1. A process for decontaminating an organic material containing waste of hazardous inorganic components comprising the steps of:

collecting one or more waste volumes to amass a treatment volume; and

injecting the amassed waste with ozone in a manner and at conditions capable of reducing the concentration of said hazardous inorganic components to at or below a required concentration.

2. The process of Claim 1 wherein the hazardous inorganic components is an azide having the formula XN₃, where X is an alkali metal.

3. The process of Claim 2 wherein the hazardous inorganic components is sodium azide.

4. The process of Claim 1 wherein the waste is collected from laboratory stock or testing solutions, in vitro diagnostic products, from blood testing, or from other laboratory test procedures containing inorganic preservatives.

5. The process of Claim 1 wherein concentration of the hazardous inorganic components is reduced to non-detectable levels.

6. A process for decontaminating an organic material containing waste of hazardous inorganic components comprising the steps of: a. collecting one or more waste volumes to amass a treatment volume in a holding tank having a first sensing device; b. sending a signal from the first sensing device to a programmable logic controller (PLC) when a first preset parameter is attained, wherein said PLC initiates transfer of the collected waste in the holding tank to a treatment tank having second sensing device; c. said sensing device sending a signal to the PLC when a second parameter is attained to initiate a recirculation of the waste; and d. injecting a stream of ozone into the tank in a manner and at conditions capable of reducing the concentration of said hazardous inorganic components to at or below a required concentration.

7. The process of Claim 6 wherein the hazardous inorganic components is an azide having the formula XN₃, where X is an alkali metal.

8. The process of Claim 7 wherein the hazardous inorganic components is sodium azide.

9. The process of Claim 6 wherein the waste is collected from laboratory stock or testing solutions, in vitro diagnostic products, from blood testing, or from other laboratory test procedures containing inorganic preservatives.

10. The process of Claim 6 wherein concentration of the hazardous inorganic components is reduced to non-detectable levels.

11. The process of Claim 6 further including an oxidation reduction potential (ORP) sensor in the treatment tank, said sensor connected to a PLC, wherein a signal is sent to the PLC when a preselected ORP value is reached, whereupon the PLC causes the ozone injection to be stopped.

12. The process of Claim 6 wherein the treated waste is transferred to a waste disposal facility.

13. A process for decontaminating an organic material containing waste of hazardous inorganic components comprising the steps of: a. collecting one or more waste volumes to amass a treatment volume in a treatment tank having a level sensing device; b. sending a signal from the sensing device to a programmable logic controller (PLC) when a preset height or volume is attained; c. said treatment tank level sensor sending a signal to the PLC when the level or volume reaches a preselected level to initiate a recirculation of the waste; d. injecting a stream of ozone into the tank in a manner and at conditions capable of reducing the concentration of said hazardous inorganic components to at or below a required concentration.

14. The process of Claim 13 wherein the hazardous inorganic components is an azide having the formula XN₃, where X is an alkali metal.

15. The process of Claim 14 wherein the hazardous inorganic components is sodium azide.

16. The process of Claim 13 wherein the waste is collected from laboratory stock or testing solutions, in vitro diagnostic products, from blood testing, or from other laboratory test procedures containing inorganic preservatives.

17. The process of Claim 13 wherein concentration of the hazardous inorganic components is reduced to non-detectable levels.

18. The process of Claim 11 further including an oxidation reduction potential (ORP) sensor in the treatment tank, said sensor connected to a PLC, wherein a signal is sent to the PLC when a preselected ORP value is reached, whereupon the PLC causes the ozone injection to be stopped.

19. The process of Claim 11 wherein the treated waste is transferred to a waste disposal facility.