Heurtistics for Medical Waste Treatment Design


Elements of the process

Think about

  • Expected rate of generation of waste – both average over time and peaks
  • Space for storage of medical waste
  • Will waste be treated on-site or sent elsewhere for treatment
  • Even if main treatment will be off-site will you have a pre-treatment process?
  • What is your procedure for protecting employees and other humans – protective clothing, masks, etc.
  • Are you needlessly generating extra waste by diluting your true medical waste with non-medical waste? This will result in higher treatment and disposal costs
  • Record keeping

autoclave

1) Avoid creation of hazardous or toxic materials in the treatment process, If there are hazardous materials in your waste stream and you can transform them to something not hazardous with a reaction, use an excess of non-hazardous reactants to completely consume the hazardous material.

2) Consider purge streams to avoid build up of inert materials. Be careful to avoid purging of hazardous materials.

3) Use a jaw crusher to reduce lumps of hard, abrasive, or sticky materials to slabby materials of 1 to 4 inches
Gyratory crusher to pieces 1 to 10 inches
Cone crusher to 0.2 in to 2 inches.
Rod mill takes particles as large as 20 mm and grinds to 10 to 35 mesh
Ball mill take particles 1 to 10 mm and reduces to 140 mesh.

4) The stoichiometric temp of a flame from natural gas combustion is 3500 F. In practical operation with excess air to be achieve complete combustion, temp is more like 2000 F. Stack gas is 650 to 950 F so as to avoid condensation.

5) An autoclave is a vertical cylindrical stirred tank reactor. Can be operated continuously or batchwise, rates of temperatures, pressures, and rates. Internal agitators (propellors or turbines) or forced circulation with external pump. Autoclaves can be rocked or tumbled to stir the contents. Heat from jacket, internal coil.

Cost estimates

A useful cost estimation trick: If you know the cost of a waste treatment system, the cost of a smaller or larger system can be estimated using the 0.6 exponent. You have to know the capacity of the two systems, and then the cost varies as the ratio of the capacities to the 0.6 power.

If C1 = known cost of existing system
And
X1 = capacity of existing system
And
X2 = capacity of new system,

Then C2, estimated cost of new system is

C2 = (X2/X1)^0.6

Note this works for capital cost. Operating cost is more likely to scale linearly with capacity.