Abstract:
A method for pathogen destruction in dilute sewage sludge or other dilute streams containing pathogens, including Helminth ova, while minimizing vapor generation and atmospheric emissions. In addition to conventional waste treatment steps, including grit removal, clarification, and concentration of waste material, vaporized waste treatment compounds are recycled to treat divert untreated waste in a scrubber. In the scrubber, waste material is treated while also acting as a reactive agent to scrub potentially hazardous or noxious gas, particularly gaseous MITC, from the treatment system. Recycling of vaporized treatment compounds provides a reduction of potentially toxic emissions and increased efficiency during treatment.

Description:
BACKGROUND 
       [0001]    The present disclosure relates to a process for treating organic sludge to remove viable pathogenic organisms and reduce vector attraction while significantly reducing residual toxic vapors. 
         [0002]    As human population continues to increase, the amount of solid waste generated by human activities also increases. Dealing with this increase in waste has put stress on waste treatment facilities, and new or improved methods of treatment are necessary. Treating solid waste can generate byproducts that are detrimental to the environment, thus, negating the benefits achieved by treatment. 
         [0003]    Pollution control authorities such as the Environmental Protection Agency, require that sewage be treated to remove pathogens prior to utilization or disposal of the waste. Sewage is often disposed of in land fills, surface sites, incineration or application to land. Land fill and surface sites are rapidly filling. Incineration requires the use of expensive fuel and contributes to air pollution. A more productive use of waste involves application to land in agricultural production due to the beneficial organic and mineral components of the waste. However, treated waste must be of low toxicity, or non-toxic, to be used in agriculture; as well as being essentially pathogen free. Chemical treatment of organic sludge to destroy microbial pathogens is known in the art. Treatment may be in the form of chemical addition or temperature elevation. Many chemical treatment processes rely on treating sludge a batch at a time or require additional treatment at remote locations due to insufficient on-site equipment. 
         [0004]    Chemical treatment of waste often generates toxic byproducts, rendering the treated was inapplicable for use in agriculture. Additionally, toxic vapors may result in areas near treatment facilities experiencing problems with the pollution, including health and unpleasant odors. 
         [0005]    Chemical treatment of sewage sludge often produces toxic gases that are difficult to manage and dispose of. While automated processes of chemical treatment of sewage sludge are known in the art, a more efficient and clean process for destroying pathogens and reducing pest attraction is desirable. The use of MITC generating compounds for pathogen reduction and vector-attraction reduction in sewage sludge is known in the art. U.S. Patent Application 2007/0084804 discloses a method for treating sewage sludge with MITC for pathogen reduction. U.S. Patent Application 2014/0290318 discloses a method for treating sewage sludge with MITC for vector-attraction reduction. While both the &#39;804 and ‘&#39;318 applications claim the use of MITC for sewage sludge treatment, neither discloses a method to improve efficiency of MITC use in waste treatment, or discloses a method to use MITC in heavily populated areas without allowing MITC to enter the atmosphere. 
         [0006]    Control of toxic gases in sewage treatment systems has been a long-standing problem. Odorous and toxic gases may escape into the environment in proximity to a sewage system which can result in unhealthy and dangerous for those living in the vicinity of such a system. U.S. Pat. No. 4,208,383 relates to the scrubbing of acids and pre-acids such as SO2. The &#39;383 application also relates to the scrubbing of CO2 to generate carbonates and bicarbonates. Scrubbing of toxic gaseous or liquid material from treated waste is not a new concept. However, minimizing additional materials and cost from the process is an ongoing need in the field. Reducing or destroying pathogen content without adding unnecessary toxic material to the process is a goal of research in this area. 
         [0007]    Patents in the literature have described numerous methods of dealing with high pathogen containing waste, such as sewage sludge; and the toxic fumes that may result. U.S. Pat. No. 5,422,015 relates to a waste treatment system for removing pathogens from sewage sludge. In the &#39;015 patent, a method of treatment of sludge with an acid, along with a material that will react exothermically with the acid, generate heat to destroy pathogens in the waste. The gases generated by this process may be absorbed by a liquid, rather than exhausted into the atmosphere. 
         [0008]    U.S. Pat. No. 4,208,383 relates to a process and apparatus for the absorptive removal of pollutants from waste gases. The &#39;383 patent describes a process whereby gas containing a contaminant is passed from supply tanks into an absorber. The &#39;383 patented process neutralizes the pollutant in the gas through the use of lime, sodium hydroxide or other neutralizing agent. 
         [0009]    U.S. Pat. No. 4,793,927 relates to a method for chemically disinfecting sewage with an ammonia source and converting it into an impermeable, friable mass with cement and silicate. A strongly alkaline environment kills bacteria and viruses. While effective, the method of the &#39;927 patent, does not leave the soil in a condition for beneficial agricultural use in many areas. 
         [0010]    The expansion of sewage treatment systems into new developments or heavily populated environments can be limited due to real estate unavailability, neighbor aesthetic complaints, zoning restrictions, lack of capital availability or the use of potentially toxic treatment chemicals that may enter the atmosphere or water supply to remove pathogens. These factors can result in the need for sewage to be transported from the source of treatment to a remote location. This process requires additional expense. The alternative, adding air treatment equipment such as conventional scrubbers, as described in the patent literature included above, also requires substantial maintenance effort and expense. However, the present disclosure provides a method and system that improves efficiency when toxic chemicals produce gases that may be detrimental to the surrounding environment, thereby overcoming the above listed problems. 
       SUMMARY OF THE INVENTION 
       [0011]    The present disclosure relates to a process for treating sludge that improves efficiency and reduces toxic emissions. The present disclosure provides a method for minimizing the number of steps required to destroy pathogens during sludge treatment. Additional benefit of the process is to reduce pollution of the environment. Additional features and advantages of the present disclosure will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present disclosure. 
         [0012]    To achieve these and other advantages and in accordance with the purposes of the present disclosure, as embodied and broadly described herein, the present disclosure relates to a method to destroy pathogens in sewage sludge comprising admixing sewage sludge with a pathogen destroying chemical in an amount effective to destroy pathogens while recycling and reusing, rather than discharging, excess pathogen destroying chemicals. 
         [0013]    In accordance with one important aspect of the invention, a method is provided for, preparing sewage sludge, which, for the purposes of the present system may be up to about 10% solids, for treatment by conventional means then conducting it to a reactor tank where it is mixed with an appropriate amount of metam sodium. The metam sodium reacts with the sludge to generate methyl isothiocyantate (MITC) at a level adequate to eliminate pathogens. The treated sludge is then sent to a hold tank for a predetermined time. The method contemplates the introduction of an alkali, such as sodium hydroxide. The use of an alkali is beneficial to augment the metam sodium in destroying pathogens by raising the pH to a suitable level. In one aspect of the present disclosure, in the hold tank, sodium hydroxide is added to raise the pH of the sludge to a level effective in further reducing pathogens and vector attraction in accordance with existing regulations sufficient for discharge of the treated sludge. 
         [0014]    The treated sludge is then conducted to a MITC removal tank. MITC is toxic and a lacrymator and may be detrimental to the environment; therefore, MITC removal is often required prior to sludge leaving the treatment system. However, rather than removing MITC from vapors generated during treatment via adsorption or chemical destruction, excess MITC can be put to further use by applying it to untreated sludge. The preferred embodiment of the present disclosure reuses MITC vapor by reintroducing it to heretofore untreated sludge in a scrubber tank. The preferred embodiment incorporates untreated sludge material into the scrubber, thereby utilizing untreated sludge material to replace traditional scrubbing chemicals or absorbants. This method of scrubbing improves efficiency over existing systems and reduces cost. A further objective of the scrubber is to reduce MITC released to the atmosphere to non-detectable levels. 
         [0015]    The preferred embodiment of the present disclosure incorporates a scrubber in fluid communication with the hold tank and the MITC removal tank. Rather than dispose of the excess MITC or release it into the environment, the MITC vapor is conducted to a scrubber. The MITC vapor filters through the sludge and destroys pathogens. 
         [0016]    The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate some of the embodiments of the present disclosure and together with the description, serve to explain the principles of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    In the description which follows, like elements are marked throughout the specification and drawing with the same reference numerals, respectively. The drawings are not to scale and at least certain conventional elements are shown in schematic form using conventional symbols for same. The present disclosure and the manner in which it may be practiced is further illustrated with reference to the accompanying drawings wherein: 
           [0018]      FIG. 1  shows a schematic view of the process  100 . 
           [0019]      FIG. 2  shows a schematic view of an alternative embodiment of process  100 . 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0020]    Referring to  FIG. 1 , a sludge treatment system  100  is provided according to an embodiment of the present disclosure. The sewer system illustrated and described is exemplary and the system and method of the invention may be carried out in a wide variety of sewage handling and treatment systems as well as other structures having a contaminated vapor space requiring treatment in accordance with the invention. The system is generally designated by the numeral  100 . Certain conventional components such as certain shut-off valves, check valves and take-off valves, pressure gauges, vents, connectors and other devices used in a test system are illustrated in  FIG. 1  but may not be described in detail herein in the interest of clarity and conciseness. Sludge treatment system  100  preferably includes a grit chamber  20  having a sludge input  80  and a sludge output  90 . Between the input and the output are receptacles serving different purposes in sludge treatment system  100 . One or more sludge sources  12  is connected to sludge treatment system  100 . To add metam sodium, sludge treatment system  100  is equipped with metam sodium input  28 . Preferably, metam sodium input  28 , sludge input  80  and sludge output  90  each comprise a rigid connector, for example, a stainless steel pipe. These rigid connectors are preferably welded or otherwise connected at one end to an outlet or inlet of a treatment unit or other device as described below. The other end of each rigid connector preferably extends to or into a source or receptacle. 
         [0021]    After input into the grit chamber  20 , the sludge is conducted to a clarifier  22 , where it is further concentrated to approximately 2-4% solids. Any excess clarified water from clarifier  22  is conducted to clarifier overflow  24  where it is oxidized with chlorine or the like and discharged. Sludge is generally transferred from clarifier  22  to a reactor  26  equipped with a means of agitating  36  the sludge, as would be known to one of ordinary skill in the art. In reactor  26 , settled sludge from the bottom of the clarifier is mixed with an appropriate amount of metam sodium, as supplied from metam sodium input  28 . Addition of metam sodium is proportionate to the total incoming sludge dry solids content and is charged to the reactor by means of a metering pump  30 . 
         [0022]    In the preferred embodiment of the present disclosure, it has been found that the most convenient form for exposing said sludges to an effective amount of MITC is to thoroughly mix said sludge with a liquid having at least one MITC releasing chemical dissolved therein. In the preferred embodiment thorough mixing is readily accomplished by a turbine or propeller-type mixer, however, any apparatus capable of intimately commingling a wet, cohesive mass (types of sludges as would be appreciated by one of skill in the art) with liquids or gases would be satisfactory as well. Once mixed, metam sodium reacts with the sludge to generate MITC at a level proportional to eliminate certain pathogens. 
         [0023]    The concentrations of the preferred chemicals for use in the method of the invention contemplate between 3 to 12 gallons metam sodium per dry ton of sewage solids (7.3 pounds of MITC to 29.3 pounds of MITC generated by the cited gallons) and between a pH of 10.2 and 12 generated by sodium or potassium hydroxide in hold tank  34 . Preferred concentrations of metam sodium is about 5 to 7 gallons of metam sodium per dry ton of sewage solids and between a pH of 11.o to 12.0 for sodium hydroxide or potassium hydroxide. 
         [0024]    The choice of concentrations and pH of the reactive agents depend on the optimum operating range of the system, which may vary depending on the nature of the waste material and the particular configurations of the system. 
         [0025]    The treated sludge is then sent to a hold tank  34  for a predetermined time. In the hold tank, sodium hydroxide is added to raise the pH of the sludge to a level effective in further reducing pathogens in accordance with existing regulations sufficient for discharge of the treated sludge and reducing vector attraction. Sodium hydroxide or other alkaline material such as potassium hydroxide are fed to the hold tank  34  preferably from a sodium hydroxide storage tank  82  by means of a variable speed pump  84  controlled by the pH of hold tank  34  contents. 
         [0026]    Following treatment in hold tank  34 , the sludge is conducted through appropriate pipes and fittings to an MITC removal tank  70 , where it is contacted with recycle gas from a scrubber  32 . 
         [0027]    Prior to entering reactor  26 , a fraction of the clarified sludge is diverted to scrubber  32  through a diversion pipe  50 . The treatment system  100  preferably contains a single scrubber  32 , although a plurality of scrubbers  32  may also be used. The scrubber  32  removes residual amounts of MITC which may be present in the vapor space in the MITC removal tank  70 . 
         [0028]    Scrubbers are generally well-known in the art. Scrubbers may contain a reagent or treating solution for neutralizing or otherwise treating the hazardous gas, such as MITC, or other waste. In the arrangement provided in  FIG. 1 , the scrubber  32  may be charged with untreated sludge, although other solutions may be contemplated. For example, in alternative embodiments of the present disclosure scrubber  32  may be further charged with an alkaline or caustic solution, scrubber  32  may be further charged with an acid reagent or solution, or an oxidizing solution. If sludge treatment system  100  has multiple scrubbers  32 , the treating solutions in any two of the scrubbers  32  may be the same or different. 
         [0029]    Scrubbers  32  are preferably designed to work over a range of pressures and should be able to treat concentrations of waste gas up to 100%. Moreover, scrubber  32  preferably comprises an inlet or inlets near the bottom thereof. This placement of the inlet preferably allows the waste gas to be received by the scrubber underneath the sludge in the preferred embodiment. 
         [0030]    Scrubber  32  preferably incorporates a mixing means that facilitates mixing of the MITC vapor with the sludge or treating solution of scrubber  32 . A swirling motion of the MITC vapor and sludge is preferably obtained, thereby increasing residence time and efficiency of treatment. As the scrubber  32  receives untreated sludge the volume increases in the tank, whereupon overflow is discharged to the hold tank  34  through appropriate pipes and fittings. The scrubber  32  is replenished with untreated sludge periodically or on a continuous basis to insure that there is sufficient untreated material to react with and remove MITC. 
         [0031]    In the preferred embodiment of the present disclosure, a vapor circulation means  42  is preferably provided for conducting MITC containing vapor from MITC removal tank  70  to scrubber  32  through suitable pipes and fittings. The hold tank  34  is also in fluid communication with vapor circulation means  42  to conduct any MITC vapor through a check valve  40  preferably to the inlet of a blower as part of the vapor circulation stream conducted to the scrubber  32 . The MITC vapor preferably enters scrubber  32  beneath the sludge and filters upward. Once passed through scrubber  32 , vapor scrubbed of MITC is returned to the MITC removal tank  70 . Any excess air built up after scrubbing may escape through a vent  72 . An additional line from the MITC reactor  26  to hold tank  34  allows vapors to pass from the reactor  26  to the hold tank where it can be ultimately sent to the scrubber  32 . Without the additional line, vapors may build up in the MITC reactor. 
         [0032]    After treatment in MITC removal tank  70 , sludge may be filtered in filter tank  92 . Optionally, treated sludge may be neutralized in neutralization tank  94 . In one aspect of the present disclosure, the filtrate from tank  92  is sent to clarifier  22 . A combination of these two ancillary steps may also be practiced. 
         [0033]    Sludge treatment system  100  may be monitored and controlled remotely by an operator. In an embodiment of the present disclosure, a control room may be provided with a control panel which may be capable of selectively and remotely controlling inputs and outputs as well as measuring and monitoring within the system as appropriate. These connections may be achieved by any appropriate method, whereby inputs and outputs receive electronic signals from control panel. These signals would preferably control the flow levels and amounts entering and leaving the respective inputs and outputs, in one embodiment through opening or closing of valves or adjusting pressure. 
         [0034]    In an alternative embodiment shown in  FIG. 2 , there is no additional line from the MITC reactor  26  to hold tank  34  allows vapors to pass from the reactor  26  to the hold tank. 
         [0035]    In an embodiment of the present disclosure, the control room is provided with remote viewing devices. Further, the control room contains sampling panel, which is operatively linked to a remote valve actuation mechanism to measure concentrations of chemicals within elements of treatment system  100 . 
         [0036]    Experiments were performed demonstrating that sewage sludge was effective at scrubbing MITC from air. 
       Example 1 
     Experiment B 
     Pilot Scale of Class B Process 
       [0037]    Data acquired from the Class B process is summarized in Table 1. Data is reported in ppm (vol./vol.) applying the universal gas law under STP conditions for MITC. Data shows that MITC concentration appears to have maximized between 3-4 ppm after 6-hours of mixing. At the maximized air concentration, all scrubber effluent results were near detection limits.  FIG. 3  shows GC chromatograms of a NIOSH tube extract from a 2-L air influent and effluent air sample from the scrubber. MITC is reduced from 2.34 to 0.04 ppm in this example. The largest volume of air measured was the overnight sample at 84-L. The influent extract sample from this measurement was examined by GC-MS.  FIGS. 4 and 5  show the GC-MS chromatograms/results for a MITC standard and the 84-L extract sample. MS spectral search shows a good match for MITC with the NIST library. This work confirms our GC/FID analysis for the identification of MITC in air from this study. In addition, sulfides were also tentatively identified in this sample. Quantitatively the GC-MS result for this sample are in good agreement with the GC/FID findings for this sample (930 vs. 900-μg, respectively). 
       Experiment C 
     Pilot Scale of Class A Process 
       [0038]    Data acquired from the Class A process is summarized in Table 2. 
         [0039]    Following the 14-hour static (no airflow) time of this experiment it was noted that the sparge tube into the scrubber clogged. This resulted in reduced flows for the first hour of sampling (˜20-mL/min.). Data at these reduced flows are not presented since the rates were considered inconsistent and the results suspect. The sparge tube was cleaned and the experiment proceeded at normal flow rate (100-mL/min.) resulting in the remainder of the data set. MITC concentration in air reached its highest level at 13-ppm. Effluent from the scrubber at this influent level showed 0.2-ppm for a 98% removal. 
       Experiment D 
     Pilot Scale of Class B Process—Sampling Sludge Suspension 
       [0040]    Data in Table 3 summarizes the quality control measurements and sample results for the determination of MITC content in sludge. Data show that at the conclusion of experiment D, 93.4-μg/g of MITC remained in the sludge. Considering 1.6-mL of Rid-A-Vec™ is added to the suspension, Metam sodium can generate 0.45-g MITC. This is in 1500-g of sludge suspension, which can generate a concentration of 300-μg/g. 
         [0041]    Close batch reactor samples from experiments from B and C were also examined for MITC content. Results are included in the table. It should be noted that for these two samples measurement was conducted 22 and 14 days following sample generation for experiments B and C, respectively. Samples were stored in zero headspace vials at 4° C. prior to analysis. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Experiment B - Class B Process 
               
               
                 Results Summary 
               
             
          
           
               
                   
                 MITC Content 
                   
               
             
          
           
               
                   
                 Elapsed 
                   
                 Influent 
                 Effluent 
               
               
                   
                 Time 
                 Vol. 
                 (ppm) 
                 (ppm) 
               
             
          
           
               
                   
                 ID 
                 (min.) 
                 (L) 
                 (vol./vol.) 
               
               
                   
                   
               
             
          
           
               
                   
                 1022-104- 
                 10 
                 1.0 
                 0.92 
                 ND0.03 
               
               
                   
                 C/D 
               
               
                   
                 1022-104- 
                 20 
                 1.0 
                 1.25 
                 ND0.03 
               
               
                   
                 E/F 
               
               
                   
                 1022-104- 
                 30 
                 1.0 
                 0.96 
                 ND0.03 
               
               
                   
                 G/H 
               
               
                   
                 1022-104- 
                 40 
                 1.0 
                 1.31 
                 ND0.03 
               
               
                   
                 I/I 
               
               
                   
                 1022-104- 
                 50 
                 1.0 
                 1.19 
                 0.03 
               
               
                   
                 K/L 
               
               
                   
                 1022-104- 
                 60 
                 1.0 
                 1.43 
                 0.04 
               
               
                   
                 M/N 
               
               
                   
                 1022-104- 
                 70 
                 1.0 
                 2.67 
                 0.04 
               
               
                   
                 O/P 
               
               
                   
                 1022-105- 
                 90 
                 2.0 
                 1.20 
                 0.02 
               
               
                   
                 A/P 
               
               
                   
                 1022-105- 
                 110 
                 2.0 
                 2.34 
                 0.04 
               
               
                   
                 C/D 
               
               
                   
                 1022-105- 
                 130 
                 2.0 
                 1.70 
                 0.03 
               
               
                   
                 E/F 
               
               
                   
                 1022-105- 
                 250 
                 6.0 
                 0.83 
                 0.02 
               
               
                   
                 I/J 
               
               
                   
                 1022-105- 
                 310 
                 6.0 
                 2.24 
                 0.03 
               
               
                   
                 K/L 
               
               
                   
                 1022-105- 
                 370 
                 6.0 
                 3.27 
                 0.02 
               
               
                   
                 M/N 
               
               
                   
                 1022-105- 
                 430 
                 6.0 
                 0.91 
                 0.02 
               
               
                   
                 O/P 
               
               
                   
                 1022-105- 
                 1270 
                 84.0 
                 3.62 
                 0.01 
               
               
                   
                 Q/R 
               
               
                   
                 1022-105- 
                 1405 
                 13.5 
                 3.83 
                 0.02 
               
               
                   
                 S/T 
               
               
                   
                 1022-105- 
                 1645 
                 24.0 
                 4.07 
                 0.01 
               
               
                   
                 U/V 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Experiment C - Class A Process 
               
               
                 Results Summary 
               
             
          
           
               
                   
                 MITC Content 
                   
               
             
          
           
               
                   
                 Elapsed 
                   
                 Influent 
                 Effluent 
               
               
                   
                 Time 
                 Vol. 
                 (ppm) 
                 (ppm) 
               
             
          
           
               
                   
                 ID 
                 (min.) 
                 (L) 
                 (vol./vol.) 
               
               
                   
                   
               
             
          
           
               
                   
                 1022-106B 
                  30 
                 0.5 
                 3.11 
                 0.50 
               
             
          
           
               
                 14-HOUR STATIC PERIOD 
               
             
          
           
               
                   
                 1022-106G 
                     930 a   
                 0.5 
                 9.07 
                 0.24 
               
               
                   
                 1022-106H 
                  960 
                 0.5 
                 10.6 
                 0.23 
               
               
                   
                 1022-106I 
                 1020 
                 1.0 
                 10.0 
                 0.23 
               
               
                   
                 1022-106J 
                 1080 
                 1.0 
                 9.37 
                 0.17 
               
               
                   
                 1022-106K 
                 1200 
                 2.0 
                 13.4 
                 0.21 
               
               
                   
                 1022-106L 
                 1320 
                 2.0 
                 13.4 
                 0.22 
               
               
                   
                   
               
               
                   
                   a After the static period of 14-hours the sparge tube in the scrubber was clogged. Flow was discontinued and the sparger cleaned. Thus this samples was taken after a duration of 15:30 hours (930 min.). 
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Experiment D - Sludge Water Suspension from Close Batch Reactor 
               
               
                 Analysis for MITC 
               
             
          
           
               
                   
                   
                 MITC 
               
               
                   
                 Sample 
                 (μg/g) 
               
               
                   
                   
               
             
          
           
               
                   
                 1022-109I Exp. D 
                 93.4 
               
               
                   
                 Spiked at 324-μg/g % Recovery = 83% 
               
               
                   
                 1022-109E Exp. B 
                 85.2 a   
               
               
                   
                 Spiked at 334-μg/g % Recovery = 86% 
               
               
                   
                 1022-109E Exp. C 
                 85.2 a   
               
               
                   
                   
               
               
                   
                   a Note samples analyzed several days after generation. 
               
             
          
         
       
     
         [0042]    Although exemplary embodiments have been shown and described, it will be clear to those of ordinary skill in the art that a number of changes, modifications, or alterations to the disclosure as described may be made. All such changes, modifications, and alterations should therefore be seen as within the scope of the disclosure.