The wastewater of 2 million of the 2.8 million people living in Jerusalem and the West Bank is not treated, according to a new report.

The human rights group B'Tselem on Sunday released its report "Foul Play: Neglect of Wastewater Treatment in the West Bank."

While the organization laid much of the blame on Israel, it said the Palestinians also were at fault.

The report said the failure to treat the Israeli and Palestinian wastewater could result in the permanent contamination of the mountain aquifer, a main source of water for both Israelis and Palestinians.

Only 81 of the 121 West Bank Jewish settlements are connected to wastewater treatment facilities, many of which are outdated and not able to handle the full load of sewage, according to the report.

The Palestinians suffer the most from the untreated sewage, which flows down from the settlements, mostly built on top of hills, to the Palestinian villages located in the valleys below, the report said. The villages also depend on springs and wells for their water, which become contaminated by the wastewater.

Some 95 percent of Palestinian wastewater is not treated, and the Palestinians have resisted attempts by Israel to join together to treat the wastewater, saying it would legitimize the settlement enterprise, according to the report.

B'Tselem called on Israel to treat all wastewater from the settlements in the same advanced way as within the Green Line, and demanded that Israel and the Palestinian Authority cooperate in cleaning up wastewater, even if it means using the same treatment plants.