What is the Janicki Omni Processor?

a computerized prosthetic that enables its wearers to mentally control artificial limbs

a mechanical device that converts sewer sludge into potable water and electricity

a department chief who oversees a manufacturer's human resource operations

a miniaturized mechanism that can scan a printed page from over 25 feet away

A mechanical device which converts sewer sludge into potable water and electricity, is the correct answer.

Explanation:

The name Omni processor was proposed by the Bill and Melinda Gates Foundation. It refers to a group of biological, physical and chemical treatment process to process the fecal sludge in developing countries. The main aim of this treatment is to remove pathogens to stop the spread of fecal sludge. The staff at Bill and Melinda gates foundation coined this term. It's not a trademark. Different Omni processors are being developed by the research teams, Bill and Melinda gates foundation is funding this researches.

It is a couple of a 3 so the answer will be 4