BSL-3,Decontamination,Waste Management

A waste treatment system was designed and built to process liquid effluent from a laboratory/vivarium working with human pathogenic viruses. The laboratory/ vivarium must operate in accord with the requirements of Biological Safety Level 3 Enhanced (BSL3+) and ABSL-3. The paramount design criterion for the treatment system is that no viable virus may escape the treatment system into the municipal sewage system serving the lab/vivarium. The treatment process is based on the fact that human pathogenic viruses are susceptible to de-activation by exposure to aqueous solutions of sodium hypochlorite, the same chemical found in household bleach.

The treatment system adapts a protocol commonly employed in chemical crystallizers and mammalian cell bioreactors to transform a batch process into a quasi-continuous operation. In the chemical industry, this technique is called maintenance of a “reactor heel.” The “heel” is maintained by never completely emptying the treatment “reactor.”

The combination of chlorine chemical treatment with the “heel” control scheme results in a system comparable in containment security to more traditional systems at substantially reduced cost. Therefore, this Bio-hazardous Liquid Effluent Treatment System (BLETS) represents a useful solution to the particular problems presented by BSL3+ containment requirements for viruses.

Laboratory Operations,Waste Streams, and the BLETS
The virus lab and vivarium both generate liquid waste. This waste is mostly water, containing the various salts, sugars, proteins, DNA, and viruses that such a facility will produce. Even though validated methods for de-activating the virus present in the laboratory and vivarium will be employed to prevent entry of live virus into the BLETS, the BLETS stands between the operations of the lab and the sanitary sewage system as the “last line of liquid defense.”

The BSL3+/ABSL-3 standards require all categories of discharges from the lab to be properly treated. This is a multistream, multi-phase problem because air, water, and solids are involved.The BLETS treats only one waste stream, aqueous liquid effluent.

There are five categories of effluent directed into to the BLETS:

1. Personnel shower effluent: This is presumed to be a nonpathogenic water stream by virtue of the procedures employed to prevent and rectify contamination of lab staff. The methods employed to de-contaminate should not result in contaminated liquid effluent introduction into the BLETS.
2. Treated biosafety cabinet liquid waste: This consists of dilute aqueous solutions to be de-contaminated (using chlorine bleach solutions) before removal from a biosafety cabinet. This waste is then introduced into the BLETS via the lab sink drains.
3. Autoclave condensate: Only the autoclave jacket condensate is directed to the BLETS; this means that contaminated effluent from the autoclave can only arise upon failure of the autoclave vessel/jacket system.
4. Liquid effluent waste: This is waste from the animal holding and procedure rooms.
5. Solid waste: Solids from the lab and the vivarium are decontaminated by a steam heated sterilizing/maceration system(SSM). The pressure vessel of the SSM is equipped with an over-pressure relief valve. In the event of discharge from this relief valve, a stream of potentially contaminated air and/or steam will be directed into the BLETS. This discharge should occur only when the SSM process vessel pressure-relief valve fails because the process vessel is rated for approximately four times the pressure normal operating pressure of the SSM. In the event of discharge from the SSM process vessel, treatment of the effluent (an air, steam, and liquid water mixture) will be passed through the BLETS and then into the building HEPA vent system, which serves as a “last-line of gas defense” for containment of lab gas discharges.