It is so easy to flush waste down the drain without giving it a second thought

It is so easy to flush waste down the drain without giving it a second thought. We all do it, but the reason not to do it is quite profound.

Who would have thought 30 years ago that the retro-virus responsible for AIDS would have such a devastating worldwide socioeconomic impact, affecting all walks of life and straining country medical systems? Speculation is that this adaptive and deadly virus may have been manmade, an experiment gone wrong. Will we ever know for sure? Ask yourself about Legionnaire’s Disease, SARS, the new Super E-coli drug resistant strain, BSE (Mad Cow Disease), and what about the effects of the ancient nano-bacteria? The avian flu, responsible for the deaths of millions of birds in China, is now fatal to people. Will this trans-species, mutated viral pathogen become the Black Plague of the 21st Century? The World Health Organization is predicting a flu-like pandemic soon. Is this the one? Are we ready for it? Laboratories seeking solutions to eradicate these pathogens are strengthening laboratory bio-containment to protect the staff and their facilities. The question is; are the waste streams being discharged into the public domain free of pathogens and is the public being adequately protected?

National regulators, responsible for human and animal safety, have imposed enhanced precautionary waste discharge procedures at specified levels of animal research, agricultural research, and at all levels of genetic research in government, hospital, animal, pharmaceutical, and private laboratories. Given the extent to which new biological o ccurrences are increasing in number, all facilities disposing potentially infectious solid and liquid waste streams should have zero-tolerance, mandatory protocols for wastes discharged.

These measures will ensure that known or unknown agents will not enter the public domain by any entry point. Currently, the strictest measures are imposed on BSL-3 and BSL-4 facilities. What about unknown agents being developed? Regulators that prescribe the level for waste sterilization required have been slow to react to change in accordance with these new hidden biological threats. It, therefore, makes sense that all laboratories and corporations, and not the regulators, proactively seek solutions beyond the baseline regulatory requirements. They should ensure that all infectious solid and liquid waste effluents are completely sterilized at the source as a preventative measure. Biological contaminants should not enter the environment in any viable form in order to ensure public safety. This must apply to all discharges from biological and animal laboratories, public and private, regardless of their certification level. WHY? We are an out of sight out of mind society.

An EPA study prepared in 20001 sheds some light on national sanitary sewer infrastructure failure because of increased exfiltration rates. This supports the argument for “treat before discharge.”

Figure 1:
Sanitary sewer systemcomponents and exfiltration
sources. (Source: EPA/600/R-01/034, December 2000. Courtesy
of USEPA's National Risk Management Research Laboratory.)

Potential for Exfiltration of Biohazardous Waste Water Effluents

With the exception of new construction that incorporates PVC piping for sanitary sewer systems, the majority of the national sanitary sewer infrastructure in the country is aging (Figure 1). Even with new construction, these pipelines discharge into much older existing systems before they reach the local sewerage treatment plant. In many regions of the country, the sanitary sewerage piping had been installed above the groundwater table and in these instances there is a documented exfiltration rate of up to 40%. Exfiltration means that the contents of the pipe carrying sewerage would exit the system and could potentially contaminate the groundwater (aquifer).

Many of the older wastewater pipeline systems are open channel, dual service sewers that also handle storm water. In a heavy rain situation, the storm water flow discharges and mixes with the sanitary sewerage flow. This results in the cross-contamination of the storm water. The mixed wastewater effluent eventually discharges into a river, lake, or stream carrying with it a combination of storm water and sewage. Transport of the sewage and pollutants leaking into the subsurface/groundwater depends on a variety of factors including but not limited to:

• the difference in hydraulic head between the sewer surface and the groundwater table level

• the substrate physical/chemical/
biological characteristics (which determines the attenuation potential)

• the sewage pollutants and their concentrations

Fecal bacteria contamination is the most serious risk associated with domestic sewage exfiltration. Contamination by viruses, protozoa, and other microorganisms characteristic of untreated laboratory discharge increases that risk. Indicators such as boron and phosphate are used to determine sewage pollution since they are not naturally occurring in groundwater.

Most animal and biological research laboratories discharge their liquid wastes into the local sanitary sewage system and only BSL-3 and 4 labs sterilize their liquid waste effluents. What we don’t know about are the potential hazards of discharging blood and lower end bacterial and viral spores from BSL-1 and 2 facilities into the sewerage systems. Do we know the risks?

With the ever-increasing potential threat to public health from unknown sources, research facilities that handle any infectious viral and/or bacterial agents must mitigate these risks with proactive in-house wastewater containment and sterilization measures. Advanced technology is available that will ensure a biological pathogen-free discharge.

Microwave Solutions from the Kitchen
One technological solution incorporates the use of microwave energy for sterilization. The development of microwave technology has evolved as an environmentally clean solution that meets or exceeds the needs of this industry. When applied to solid and/or liquid waste effluents, the unique properties of microwaves serve to:

• effectively sterilize solid organic wastes through drying and complete carbonization

• sterilize liquid wastes through both heating and microbial cellular disintegration

In a simplified version, it works like this: A man comes home from work and throws a couple of potatoes into the microwave oven, sets the timer, and goes outside to cut the lawn. He gets distracted talking to the neighbor and only notices something is amiss when white smoke starts billowing out of the kitchen window. He runs inside only to find that the contents of the microwave oven are on fire. He quickly turns it off. After it has had time to cool off, he removes two pieces of charred carbon, no longer resembling potatoes. What happened? He mistakenly set the timer to one hour rather than ten minutes and overcooked the potato to a char. The fire was caused by the breakdown of the organic material in the potato that retained sufficient internal heat to ignite. In a very rudimentary way, the potato was sterilized and disintegrated by direct microwave application.

About Microwave Energy
Microwaves are electromagnetic waves in the frequency band from 300MHz to 300GHz, but industrial microwave processing is usually accomplished at frequencies of 2450MHz. When an electric field interacts with a material, a number of responses can take place:

• In a conductor, electrons move freely in the material in response to an electric field, and an electric current results. Here, the flow of electrons will heat the material through resistive heating.

• In an insulator, electrons do not flow freely, but re-orientation or distortions of induced or permanent dipoles can give rise to heating.

Microwaves are largely reflected from metallic conductors but interact well with dipoles, such as water, and are an efficient way of heating non-conducting materials. Microwaves generate rapidly changing electric fields and dipoles rapidly change their orientations in response to the changing fields. If the field change is occurring near the natural frequency at which re-orientation occurs, then a maximum utilization of energy is realized and optimum heating occurs.

Microwaves penetrate materials and release their energy in the form of heat as the polar molecules (ones with a positively and a negatively charged end) vibrate at high frequency to align themselves with the frequency of the microwave field. Because microwaves interact directly with the object being heated, and because the interaction is related to the chemical properties of the object, it is possible to apply heat in ways that are not achievable by conventional means. It is also possible to preferentially heat up specific layers within a material according to their chemical composition.

Figure 2:
A Three-step Microwave Processor System

Animal Waste and Microwave Reduction/Sterilization
This microwave process uses the direct application of multiple, high-energy microwave generators to a nitrogen rich, oxygen-depleted processing chamber environment (Figure 2). The organic components of the animal and animal laboratory-related waste stream are effectively dried. Then the organic material is broken down into simpler gaseous molecules. The remaining waste is a sterilized, non-toxic carbonized residue.

At the molecular level, direct microwave energy is absorbed by the organic material, causing rotation of inter-molecular bonds. This leads to the generation of narrow band infra-red energy. The narrow band infra-red energy is re-adsorbed by surrounding material, increasing the amount of energy (strain) in the C-C bonds until the bonds break. The breaking of the bonds results in the conversion of complex organic compounds into simpler compounds of lower molecular weight (gases). The nitrogen-rich atmosphere inhibits formation of products of combustion and therefore eliminates the risk dioxin formation.

A low flow of clean gases is exhausted through an ancillary environmental treatment system. The treated gases may be used to help fuel the co-generation of electricity. The chamber temperature does not exceed 250º F, however, the material temperature reaches plasma temperatures ensuring complete sterilization of all solids and evolved gases.

Direct microwave application in this manner provides a solution for the disposal of animal wastes and other biohazardous effluents linked to animal research. It reduces the mass of the waste stream by up to 85% and sterilizes all biological and animal laboratory-related pathogens with a biological efficacy exceeding 6log10. The design of equipment may include single or multiple processing chambers depending on site-specific throughput requirements. This process achieves enhanced destruction results without process ignition or flame. The mechanism of organic molecular dissection, hence lyses and carbonization, of complex temperature resistant bacteria and proteins by direct microwave application supports its destructive and protein denaturing capability.

It is believed that prions, responsible for what we now call “Mad Cow Disease,” are just complex, folded, temperature resistant proteins. It is expected that they too will be denatured and fully carbonized through molecular dissection by the direct microwave process.

Solid Waste Microbiological
Efficacy Tests
In tests2 conducted on bacterial cultures injected into bone marrow and animal tissue along with simulant waste mixes of bacterial broths, sharps, fabrics, and blood products, the reduction and sterilization process achieved:

• 6 log10 sterilization efficacy

• mass and volume reduction of up to 85%

• co-generation of electricity

• non-detectable concentrations of B.Subtilis, B.Stearothermophilus, E.Coli, Staphylococcus Aureus, Candida Albicans, Pseudonamas Aeureg., Penicillium Chryosogenum, and Mycobacteriumterrae

This method of animal waste mitigation allows the facility to completely sterilize and reduce lab wastes such as contaminated sharps, plastic tubing, glass, and linens, etc. The resulting carbonized residue is ground to a fine powder in the last stage of the process rendering all sterilized wastes processed and unrecognizable (Figure 3). The cost of operation including labor and maintenance for this process is about $ 0.16/pound U.S., when the system off-gases are used for the co-generation of electricity.

Figure 3:
Carbonization of an animal carcass in a batch processor
and the final ground carbon residue.

The process is automated, and therefore reduces the risk of worker exposure to infectious materials handling. It requires minimal manpower to operate and processes all types of waste without the need for waste segregation. The carbonized residue can bypass landfills and be shipped to a local cement kiln or mini steel mill for fuel value.

Microwave Sterilization of Liquid Biological Wastes for All BSL Levels
In addition to solid waste sterilization and reduction, the direct microwave process can be adapted to mitigate the liquid waste discharge risks from labs of all biosafety levels. This includes all domestic sewerage together with biohazardous clinical effluents. With this system (Figure 4), wastewater sterilization is executed on-site prior to being discharged into the domestic sanitary sewage system.

Figure 4:
Example of a waste water sterilization system.

The direct microwave process incorporates two methods of sterilization, applied simultaneously:

• the direct application of high-energy microwaves to affect organism cellular wall and chemical bond cleavage; and

• an applied and sustained temperature above atmospheric pressure within a pressure vessel for a predetermined waste batch DWELL time.

All liquid wastes derived from the facility washrooms and the biocontainment lab drain into a sealed holding tank or sump equipped with a grinder pumping system. The wastewater containing suspended solids is ground and then batch fed, first through a heat exchanger for preheating by the treated waste from the previous batch. The batch is then transferred to the processing chamber where the temperature is elevated by both emersion heaters and microwave energy to 285°F. This temperature is sustained under a pressure of 60psig for the prescribed dwell time and agitated to ensure uniform heating throughout. Together, super-heating the waste stream and applying direct microwave energy, ensures that all pathogens and spores are deactivated not only in free suspension, but also those pathogens attached to solids in the suspension matrix. Agitation within the pressurized sterilization vessel optimizes uniform heat distribution for pathogen heating and microwave contact that ultimately ensures deactivation. The batch then exits through a discharge tank prior to being released through the heat exchanger for release to a sanitary drain. The final effluent is a sterilized drain permissible discharge.

The EWI direct microwave process has recently been installed as a biological liquid waste deactivation system for the APHIS Center in Beltsville, MD, a BSL-3 Ag lab operated by the USDA. The system performs pre-programmed thermal deactivation of aqueous biological waste that may contain suspended solids. This specific batch system incorporates user definable operating parameters and cycles at prescribed temperatures, pressures, and batch retention times. Daily throughputs are variable. System start-up, operation, and shutdown are completely automatic. The system is designed to minimize heat loss through an enhanced energy recovery module. The process deactivates all pathogens in biological liquid waste streams including those attached to or forming the suspended solids.

Conclusion
Given the extent to which new biological occurrences are increasing in number, all facilities disposing of potentially infectious solid and liquid waste streams should have on-site, zero tolerance protocols for solid and liquid waste discharges. The “out-of-sight, out-of-mind mentality” can lead to crisis events. Someone else cannot look after responsible waste sterilization because the public infrastructure to treat many of the waste streams is failing and, in many cases, is not sophisticated enough to handle potentially hazardous discharge from lab facilities. There are many operational and public safety benefits resulting from responsible waste disposal methods.

On-site treatment of infectious waste streams through a direct microwave application process is an environmentally sound remedy for both solid and liquid laboratory waste discharges. Reducing and sterilizing laboratory waste can protect both the lab facility and the general public.

References
1. Amick, RS and Burgess, EH. EPA Study: Exfiltration in Sewer Systems. EPA/600/R-01/034, December 2000.

2. Tests were based an independent laboratory study for certification in the UK. Precision Analysis June 6, 2002. Similar tests were conducted by the University of Toronto Microbiology Dept. in 1997 by Patricia L. Seyfried, Ph.D. at Probit Laboratories, Inc.

Other References
• Im-Sun Woo, In-Koo RHee and Heui-Dong Park. Differential Damage in Bacterial Cells by Microwave Radiation on the Basis of Cell Wall Structure. Applied and Environmental Microbiology. May 2000, p.2243-2247.

• F. Celandroni, I. Longo, N. Tosoratti, F. Giannessi, E. Ghelardi, S. Salvetti, A. Baggiani, and S. Senesi. Effect of microwave radiation on Bacillus subtilis spores. Journal of Applied Microbiology, 2004, 97, p.1220-1227.

Michael G. Vocilka, BSc. Chem, is Director of Marketing and Sales for Environmental Waste International, Inc., 283 Station Street, Ajax, Ontario, Canada L1S 1S3; (905)686-8689; www.ewi.ca; Michael.Vocilka@ewmc.com.