According to Roberto, the wastewater starts with about 35, 000 parts per million (ppm) of gunk and junk.

FORBES: DONQ: LEADING LIQUOR TO SUSTAINABILITY

We would need atmospheric CO2 levels of around 500 parts per million (ppm) to kill off the process of calcification completely, reports Mother Jones.

CNN: All About: Coral Reefs

Concentrations of CO2 in the atmosphere currently stand at 385 parts per million (ppm) and are rising at a rate of two ppm per year.

CNN: Carbon dioxide levels already a danger

Using a technique called secondary ion mass spectrometry, the team determined that the mantle from which the meteorites derived contained between 70 and 300 parts per million (ppm) of water.

MSN: Scientists say parts of Mars interior are as wet as Earth's

Before we started torching carbon stored in forests and then carbon stored underground as coal and oil, the carbon dioxide concentration of our atmosphere was about 280 parts per million (ppm).

FORBES: Global Warming: Hotheads, Flatliners and Lukewarmers, Part One

That safety assessment has concluded that, based on the scientific evidence available today, 20 parts per million (ppm) of gluten is a safe level for those with celiac disease, supporting the proposed law.

FORBES: The FDA Gets Serious About Gluten-Free Labeling Laws

Despite a lingering economic downturn in much of Europe and North America, CO2 levels climbed to 394.97 parts per million (PPM) last week, marking an increase of nearly 1.6 ppm compared to last year and the highest level on record.

FORBES: Atmospheric Carbon At All-Time-High

The highly toxic H2S (hydrogen sulfide) and CO2 (carbon dioxide) are removed along with excess water to get the gas below 7 ppm (parts per million).

FORBES: We're Headed To $8 Natural Gas

The phosphate rock industry there (extracted to use in fertilisers) leaves a waste called phosphogypsum. this is around and about 30 parts per million (ppm, and normal soil is about 3 ppm) uranium and it can most certainly be processed to extract that.

FORBES: Iran Announces New Uranium Deposits: Don't Panic!