Ariz. Admin. Code § R18-13-1415 - Treatment Standards, Quantification of Microbial Inactivation and Efficacy Testing Protocols

A. A treater using an alternative treatment technology shall ensure that treatment achieves either of the following treatment standards:

1. A 6 log₁₀ inactivation in the concentration of vegetative microorganisms.

2. A 4 log₁₀ inactivation in the concentration of Bacillus stearothermophilus or Bacillus subtilis as is appropriate to the technology.

B. A treater utilizing an alternative treatment method shall conduct efficacy studies to demonstrate that the treatment mechanisms are capable of achieving the standards in subsection (A) through either of the following:

1. Mycobacterial species used as indicators of vegetative microorganisms:

a. Mycobacterium phlei, or

b. Mycobacterium bovis (BOG) (ATCC 35743)

2. Spore suspensions of one of the following two bacterial species, as appropriate to the technology, used as biological indicators in efficacy tests of thermal, chemical, and irradiation treatment systems. Studies shall demonstrate a 4 log₁₀ reduction in the concentration of viable spores, through the use of an initial inoculum suspension of 5 log₁₀ or greater of:

a. Bacillus stearothermophilus (ATCC 7953), or

b. Bacillus subtilis (ATCC 19659).

C. A treater utilizing an alternative treatment method shall quantify microbial inactivation as follows:

1. Microbial inactivation, or "kill" efficacy is equated to "Log₁₀ Kill" that is defined as the difference between the logarithms of the number of viable test microorganisms before and after treatment. This definition is stated as:

Log₁₀ Kill = Log₁₀ (cfu/g "I") - Log₁₀ (cfu/g "R")

where:

Log₁₀ Kill is equivalent to the term Log₁₀ reduction,

"I" is the number of viable test microorganisms introduced into the treatment unit,

"R" is the number of viable test microorganisms recovered from the treatment unit, and

"cfu/g" are colony forming units per gram of waste solids.

2. For those treatment processes that can maintain the integrity of the biological indicator carrier of the desired microbiological test strain, biological indicators of the required strain and concentration may be used to demonstrate microbial inactivation. Quantification is evaluated by growth or no growth of the cultured biological indicator.

3. For those treatment mechanisms that cannot ensure or provide integrity of the biological indicator, quantitative measurement of microbial inactivation requires a two-step approach: Step 1 "Control" and Step 2 "Test". The purpose of Step 1 is to account for the reduction of test microorganisms due to loss by dilution or physical entrapment.

a. Step 1:

i. Use microbial cultures of a predetermined concentration necessary to ensure a sufficient microbial recovery at the end of this step.

ii. Add suspension to a standardized medical waste load that is to be processed under normal operating conditions without the addition of the treatment agent (that is, heat, chemicals).

iii. Collect and wash waste samples after processing to recover the biological indicator organisms in the sample.

iv. Plate the recovered microorganism suspensions to quantify microbial recovery. The number of viable microorganisms recovered serves as a baseline quantity for comparison to the number of recovered microorganisms from wastes processed with the treatment agent.

v. The required number of recovered viable indicator microorganisms from Step 1 must be equal to or greater than the number of microorganisms required to demonstrate the prescribed Log reduction, either a 6 Log₁₀ reduction for vegetative microorganisms or a 4 Log₁₀ reduction for bacterial spores. This can be defined by the following equation:

Log₁₀ RC = Log₁₀ IC - Log₁₀ NR

or

Log₁₀ NR = Log₁₀ IC - Log₁₀ RC

where:

Log₁₀ RC is greater than 6 for vegetative microorganisms and greater than 4 for bacterial spores and where:

Log₁₀ RC is the number of viable "control" microorganisms in colony forming units per gram of waste solids recovered in the non-treated, processed waste residue;

Log₁₀ IC is the number of viable "control" microorganisms in colony forming units per gram of waste solids introduced into the treatment unit;

Log₁₀ NR is the number of "control" microorganisms in colony forming units per gram of waste solids which were not recovered in the non-treated, processed waste residue. Log₁₀ NR represents an accountability factor for microbial loss.

b. Step 2:

i. Use microbial cultures of the same concentration as in Step 1.

ii. Add suspension to the standardized medical waste load that is to be processed under normal operating conditions with the addition of the treatment agent.

iii. Collect and wash waste samples after processing to recover the biological indicator organisms in the sample.

iv. Plate recovered microorganism suspensions to quantify microbial recovery.

v. From data collected from Step 1 and Step 2, the level of microbial inactivation, "Log₁₀ Kill", is calculated by employing the following equation:

Log₁₀ Kill = Log₁₀ IT - Log₁₀ NR - Log₁₀ RT

where:

Log₁₀ Kill is equivalent to the term Log₁₀ reduction;

Log₁₀ IT is the number of viable "Test" microorganisms in colony forming units per gram of waste solids introduced into the treatment unit. Log₁₀ IT = Log₁₀ IC;

Log₁₀ NR is the number of "Control" microorganisms in colony forming units per gram of waste solids which were not recovered in the non-treated, processed waste residue;

Log₁₀ RT is the number of viable "Test" microorganisms in colony forming units per gram of waste solids recovered in treated, processed waste residue.

D. A treater shall employ the appropriate methodology to determine efficacy of the treatment technology following the protocols in subsection (C) that are congruent with the treatment method.

Notes

Ariz. Admin. Code § R18-13-1415

New Section adopted by final rulemaking at 5 A.A.R. 3776, effective September 17, 1999 (Supp. 99-3). Amended by final rulemaking at 27 A.A.R. 2801, effective 1/4/2022.