For the huge number of motor vehicles, the flow of traffic is hampered, causing environmental pollution and numerous difficulties for the citizens.

The change from three-stage to two-stage process was introduced in some countries in the nineties due to the fact that the water waste product is difficult to dispose of without causing environmental pollution.

Pit latrine users from Nairobi, Kisumu and Mombasa indicated that some wastewater empties into storm sewers, soak-aways and cess pits designed for kitchen waste, thus causing environmental pollution.

Each year, just in Wuhan, an industrial central city with seven million people, "more than 200 million of the containers are estimated to be thrown away, causing environmental pollution and strong opposition from the citizens," the official New China News Agency reported in August.