Nairobi, Feb. 2 -- If there is one mistake that shaped the entrepreneurial journey of Samuel Kinyanjui, a 39-year-old mechanical engineer who runs a solar water treatment company, it is engaging in deals that he had no expertise in.

"When I started, I engaged in contracts that I'm not a professional in, and I lost money. I also engaged with unclear business people who were after their selfish interests," he says.

But years later he mastered the skill of "sticking to his line of expertise, verifying before engaging into contracts and also seeking advice from those with more experience."

And his line of business is water desalination, a process that takes away mineral components from saline or borehole water.

Mr Kinyanjui started WaterK...