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Chemical cleaning of "Special Waste" conveyance piping system has only been performed under laboratory conditions. A Pipe Cleaning Protocol "Protocol" was developed for the Medical, Academic and Scientific Community Organization, Inc. (MASCO) to determine if there were any chemicals which would, without employing mechanical agitation, remove, dissolve, disperse and/or eliminate biological growth within "Special Waste" conveyance piping. A copy of the MASCO Pipe Cleaning Protocol is presented in Appendix D. This protocol testing procured "Special Waste" plumbing samples from several host institutions and subjected them to eight different types of cleaning chemicals and combinations of these chemicals.
Several institutions volunteered to serve as a host for the Protocol testing, as follows:
The cleaning protocol evaluated several different chemicals. The cleaning chemicals consisted of acids, bases and wetting agents. The following is a list of the concentrated cleaning chemicals evaluated:
All of these stock chemicals were diluted to a 5 to 40 percent working strength range, in accordance with procedures defined by the Protocol.
| Institution | Date Samples Provided | Number of Samples | Sample types |
|---|---|---|---|
| Beth Israel | March 28, 1995 | 2 | 2" glass P-trap |
| 1 | 24"- piece of 3" dia. glass pipe | ||
| Saint Elizabeth's | March 1, 1995 | 4 | 2" polypro P-trap |
| March 15, 1995 | 6 | 2" polypro P-trap (no biomass) | |
| April 6, 1995 | 2 | 2" polypro P-trap | |
| 2 | 12" piece of 2" dia. polypro pipe | ||
| Lahey Clinic | April 10, 1995 | 4 | 12" pieces of 4" dia polypro pipe |
All samples generated via Protocol testing at the Deer Island Classic Laboratory were received by Deer Island New Central Laboratory. A summary of the samples obtained by the Central Laboratory is as follows:
| Chemical Evaluated | Number of Samples | Date Samples Received | Date of Results |
|---|---|---|---|
| Sulfuric Acid | 8 | 3/10/95 | 4/25/95 |
| Hydrogen Peroxide | 24 | 3/29/95 | 4/25/95 |
| Hydrogen Peroxide / Sulfuric Acid Etch | 7 | 3/29/95 | 4/25/95 |
| Sodium Hydroxide | 15 | 4/7/95 | 4/25/95 |
| Potassium Hydroxide | 15 | 4/7/95 | 4/25/95 |
| Nitric Acid | 14 | 4/14/95 | 5/26/95 |
| Nitric Acid /Triton X-100 | 30 | 4/14/95 | 5/26/95 |
| 113 |
Figure 8.2 provides a summary of the MWRA/MASCO Pipe Cleaning Protocol analytical results performed at the MWRA's Deer Island Laboratory. Columns A through E are chemical identification and testing concentrations. Specifically, Column D is the concentrated chemical concentration, and Column E is the testing concentration after being diluted with deionized water. The remaining columns, F through M, are mercury analytical results from treatment chemicals, dilution water, biomass solids and rinsing water during various phases of the protocol testing. The following is a brief explanation of the columns from F through M:
The Protocol procedure that generated the results in Column L was intended to remove the dislodged or dissolved biomass and, the next step that generated results for Column M, represented normal effluent conditions. All of the "Special Waste"
plumbing samples containing representative biomass did not achieve complete biomass removal after chemical cleaning with the chemicals and procedures presented in the Protocol. Detailed observations and data interpretations are presented in the individual chemical sections presented below.
On March 10, 1995, protocol testing began at the Deer Island's Old Laboratory (Classic Lab) using sulfuric acid and plumbing samples obtained from Saint Elizabeth's Hospital. The samples consisted of 4 - 2" polypropylene P-traps. Only one of these traps was observed to contain substantial biomass which EARTH TECH interpreted to be representative. The biomass in the remaining three samples had little or very loose biomass with no skeletal remains.
A five percent dilution was prepared using the original 97 percent concentrated chemical. This concentration was used because a higher concentration evolved heat when diluting from concentrate. The representative plumbing sample had approximately 1/4" of biomass buildup that was adhered securely to the wall of the plumbing trap. The five percent solution of acid was allowed to soak inside the plumbing sample for approximately 1-1/2 hours. At the end of that soaking time, the solution appeared to have had little or no effect on the biomass within the plumbing sample.
The sample containing large amounts of representative biomass had an unexpected concentration of mercury of approximately 550,000 parts per billion (ppb). The analytical data indicates that the biomass mercury concentration was reduced to approximately 10 ppb but, as previously mentioned, the chemical cleaning did not remove all of the biomass.
Based on visual observations and data interpretations, it appears that this concentration, and possibly higher concentrations, of sulfuric acid will not achieve the goal for biomass removal within hospital conveyance plumbing. Furthermore, any concentration higher than this would not be recommend due to safety and conveyance piping ventilation concerns.
Samples for the March 29, 1995, testing were obtained from Beth Israel Hospital. The samples consisted of 2 - 2" glass P-traps and one 24" piece of 3" diameter glass pipe. All the samples contained some visable amount of biomass and skeletal remains. Only one of the traps had dark brown heavy biomass buildup that EARTH TECH interpreted to be representative. Hydrogen peroxide was diluted, from the original 40 percent, to create 20 and 40 percent solutions. A third solution consisting of 20 percent hydrogen peroxide and 10 percent sulfuric acid was also mixed.
The trap that contained the heavy representative biomass was subjected to the 20 percent hydrogen peroxide diluted solution. Immediately upon addition of the 20 percent solution, the sample began reacting aggressively with a foaming and bubbling action. As the solution was allowed to soak, most of the heavy built up biomass was up lifted and began floating on the surface. But, as the built up biomass was being lifted, it appeared that small amounts of the skeletal biomass remained unaffected. The solution continued to react for three hours with almost the same intensity. During these three hours of chemical soaking, it appeared that the solution had a minimal effect on the remaining skeletal biomass. Although the solution was reacting with the same initial intensity, after three hours EARTH TECH decided to remove the solution and continue with the protocol. When the solution was removed, there appeared to be some type of silvery metallic substance at the bottom of the trap. This metallic material appeared to be the cause of the vigorous reaction that had been observed. At the end of the Protocol rinsing steps, all of the large built up biomass was removed and only scattered small amounts of skeletal biomass remained.
The three inch diameter pipe also contained large amounts of dark biomass build up that seemed to be very loose. Unlike the trap exposed to the 20 percent hydrogen peroxide solution, however, this sample did not contain very much skeletal biomass. When the 40 percent solution was added, once again the sample began reacting very aggressively with foaming and bubbling. Unlike the first time this was witnessed, however, this time it only lasted for approximately 20 - 30 minutes. After 45 minutes the chemical reaction appeared to be complete, so EARTH TECH decided to remove the chemicals and proceed with the remaining protocol steps. At the completion of the testing, the piping sample was relatively clean with most of the biomass removed.
The overall performance of the 20 and 40 percent solutions was fairly successful, but complete biomass removal was not accomplished. The 20 percent solution contains 8 percent hydrogen peroxide by volume which is a strong oxidizer and potentially hazardous material. During the reactions, there was significant fuming, probably hydrogen and oxygen gases. Given the amount of gassing and safety hazards associated with hydrogen peroxide, it would not be recommended for use in large volumes and/or in poorly designed conveyance piping and venting systems.
The third sample, a three inch glass P-trap, was exposed to a 20 percent hydrogen peroxide and 10 percent sulfuric acid etch solution. Of the three samples obtained from BI, this one contained the least amount of biomass. The biomass was a golden-light brown with small areas of skeletal remains. During chemical addition and throughout the soaking periods, the chemical reactions appeared slow and subdued. After 90 minutes, it was determined that the reaction was complete and the trap appeared to be clean except for small orange spots distributed over the lower portion of the trap. These orange spots may have been skeletal remains that were not removed.
The hydrogen peroxide / sulfuric acid etch solution removal capability appears to be unsatisfactory. Also, this material would have the same safety and conveyance piping concerns mentioned previously, which would preclude widespread use.
The plumbing samples contained expected mercury concentrations which were in the range of 550 to 2,300 ppb. All of the third rinsing samples resulted in less than 0.22 ppb, but complete removal of biomass, once again, was not achieved. Although the biomass that remained was that of an adhered or skeletal form, it can not be assumed that hydrogen peroxide will consistently yield effluent results below one ppb. This skeletal biomass probably contains high levels of mercury concentration as well and when the skeletal remains eventually break off that will result in effluent with elevated levels of mercury.
On April 7, 1995, protocol testing was performed on the third set of plumbing samples provided by St. E's. These samples were divided in half; two samples for potassium hydroxide testing and two samples for sodium hydroxide testing. Observations on the internals of these samples were hard to obtain, because the plumbing material was schedule 40 polypropylene. Two of the samples were observed to contain substantial biomass growth, but how much of it was skeletal could not be determined. Potassium hydroxide was added to two 12" pieces of 2" piping, at a 15 and 30 percent dilution.
The two piping samples had different amounts of biomass, one sample had heavy grayish-white buildup of biomass, while the other had a small amount of brown biomass that was very loose. The 30 percent solution was allowed to soak for approximately 90 minutes in the sample with the grayish-white biomass. Slight foaming and floating of the biomass was all that was able to be observed (internal observation could not be made as previously mentioned). After 90 minutes of soaking, the chemical was removed but a majority of the biomass still remained although it appeared to be looser. With minimal scouring, the remaining biomass was easily removed.
The 15 percent solution had little or no effect on the piping sample with the brown biomass. During 90 minutes of chemical soaking, there was no foaming or floating of the biomass. It appears that this was a different type of biomass from all the others we had encountered. It is possible that this material may have been some type of an adhesive or cement. We had expected the biomass to be loosened similarly to that of the 30 percent solution sample.
The performance of the 15 percent solution was unsatisfactory. Although the 30 percent solution did not achieve the Protocol removal goals, it did reveal that this chemical may be used as a softening or loosening agent to assist some type of physical cleaning procedures. However, there are still several safety and plumbing concerns with the use of this material. A 30 percent dilution, of 45 percent concentrated potassium hydroxide, contains approximately 13.5 percent, by volume, of potassium hydroxide. At these concentrations, it is not recommended for use, based on the previously mentioned safety and conveyance piping concerns.
The two remaining samples, on April 7, 1995, were exposed to a 20 and 40 percent diluted solution of sodium hydroxide. One of the samples was a 12" piece of 2" polypropylene pipe and the other was a 1-1/2" P-trap. The trap had heavy build up of dark brown biomass while the piping had a thin film of gray-black biomass.
The 20 percent solution was added to the piping sample with no initial reaction. After 90 minutes, very few changes or reactions occurred. At the end of the protocol testing, hardly any biomass remained. It was difficult to determine the capabilities of this chemical, because the amount of biomass contained in the sample was so small.
However, the 40 percent solution was exposed to heavy dark brown representative biomass. The initial reaction with the biomass was a slight foaming action followed by a large amount of the biomass being dislodged and floating. This reaction continued until EARTH TECH decided to remove the chemicals approximately 90 minutes later. At the end of the testing, most of the biomass was removed though a thin film of biomass remained.
Sodium hydroxide, at a 40 percent strength, yielded similar results to the potassium hydroxide. The biomass appeared loose and with minimal scouring the remaining biomass was easily removed. This chemical would also require that all the previously mentioned safety and piping concerns be evaluated.
Another problem associated with the use of these chemicals is that potassium and sodium hydroxide were the first reagent grade treatment chemicals found to contain mercury. The levels of mercury for potassium and sodium hydroxide were 11.5 ppb and 3.68 ppb respectively (which for reagent grade chemistry was unexpectedly high). Samples KOH-1 and NaOH-4 both had some biomass removal success. But, after the third rinsing step, the analytical results indicate that the remaining biomass bits were still breaking off and causing elevated mercury concentrations very similar to the results with all the previously tested chemicals.
Samples obtained from Lahey Clinic were tested on April 14, 1995 and contained very heavy amounts of black biomass. The samples included four 12" pieces of 4" schedule 40 polypropylene. The four samples were exposed to two combinations of chemicals. The first set were 10 and 20 percent diluted solutions of concentrated 70 percent nitric acid while the second set was the same, except that a 2 and 5 percent Triton X-100 soaking solution, respectively, was introduced. The Triton X-100 is a wetting agent or dispersant which is intended to help soften and loosen the biomass before an acid solution is introduced.
The 10 percent nitric acid solution had minimal effect on the sample over a 90 minute soaking period. The only observation was a strong pungent smell upon addition of the solution. At this concentration, only very small amounts of biomass were removed.
The 20 percent solution produced slight foaming reaction which caused large pieces of biomass to float to the surface. After 90 minutes of soaking, large amounts of biomass were dissolved and removed. It appears the biomass that remained after removing these testing chemicals was much looser. This solution achieved significantly better results than the 10 percent solution.
In both cases, there were strong odors and gases being evolved during chemical soaking. In addition, the concentration of nitric acid that was used would not be recommended for large volume applications. Furthermore, it appeared as though the addition of Triton X-100 had little or no effect on the biomass.
During the period of March 10, 1995 through April 14, 1995, EARTH TECH performed chemical testing on plumbing samples from three (3) different medical institutions using eight (8) different chemicals and/or combinations of these chemicals. Plumbing sample materials consisted of polypropylene and glass and, in every instance, these samples confirmed the existence of biomass containing mercury. The different types of chemicals evaluated were acids, bases, oxidizers and dispersants. All of the chemicals evaluated were unsuccessful in obtaining the Protocol's objective of removing biomass completely using only chemical methods. Some of the chemicals were successful in removing bulky biomass, while others were successful in softening and loosening the biomass. Not one chemical alone or in combination appeared to remove all of the biomass solids. In addition, use of some of the chemicals might pose some significant health, safety and\or hazardous waste disposal issues if employed in full-scale use within a facility. Consequently, none of the chemicals evaluated in this Protocol would be recommended for in situ pipe cleaning.
Although the data presented in Column M of Figure 8.3 indicates that four chemicals tested were successful in producing effluent concentrations of mercury below 1 ppb, it should not be assumed that application of these chemicals constituted a viable solution to the problem. The documented presence of residual biomass containing mercury following these chemical applications means that the potential exists for higher concentrations of mercury to be detected at any time, due to the tendency of this material to slough off and enter the wastewater stream. If additional rinsing was performed on these samples, the analytical results of the rinse water could easily have been greater than one ppb.
The Protocol was developed with the assumption that the support laboratory would generate testing results immediately or as soon as the analytical equipment could produce them. This assumption was made to allow EARTH TECH time to evaluate the efficiency or inefficiency of each chemical and adjust the testing as needed. Since analytical results were not available soon after testing, EARTH TECH modified the testing to establish baseline testing for all the suggested Protocol chemicals.
The concentrations of the diluted chemicals used in the Protocol were much higher than recommended concentrations for full-scale cleaning. Even after being diluted, some of these cleaning chemicals were still very reactive or corrosive. Considering the amount of "Special Waste" piping requiring cleaning in most facilities, employee exposure to hazardous chemicals would be a serious concern even with the utilization of isolation valves. Employees involved with such chemical cleaning operations would almost certainly require health and safety training. Of additional concern is the fact that most of the chemicals evaluated in the Protocol would likely be characterized as hazardous waste for either reactivity, corrosivity or content. Two of the chemicals tested, sodium and potassium hydroxide, were even found to contain, themselves, concentrations of mercury in excess of 1 ppb.
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