Emmons County ND Uses Ozone Pretreatment for a UF/RO Drinking Water Treatment Plant

The South Central Regional Water District utility knew that water from these wells contained high levels of dissolved solids, hardness, and sulfates, as well as arsenic content beyond the safety standards established by the Environmental Protection Agency (EPA).

A treatment solution was developed ozone pretreatment, ultrafltration (UF) and reverse osmosis (RO) to treat nearby Missouri River water. In operation since May 2012, the new Emmons County Water Treatment Plant demonstrates the successful use of ozone as a primary disinfection and pretreatment for the downstream UF and RO membrane technologies with no compatibility issues.

Ozone is finding wide application in surface water treatment because it is economical and effective. Over 1.5 billion gallons of drinking water is treated with ozone every day.

Ozone is a stronger oxidizer than other water treatment chemicals, potentially creating challenges for UF and RO membranes. The new Emmons County water treatment plant validates ozone pretreatment for UF and RO membranes with good operating performance and membrane stability.

The new water treatment plant draws raw water from the Missouri river. Ozone is the primary disinfectant for removal of organics. Ozone is generated on site with a high degree of automation making it a safe and low maintenance treatment option.
Ozone-oxidized water enters sedimentation basins with coagulant dosage.

The water settles for 30 minutes before passing through screen flters to the ultrafltration systems for pathogen and solids removal down to the 0.03 micron level. DOW™ Ultrafltration SFD-2860 membranes were used due to their ozone-resistant PVDF chemistry and fber integrity.

The ultrafltered water then enters the RO system to remove tastes and odors, followed by chloramines dosing prior to distribution. The RO system provides a ratio of 60% permeate to 40% UF fltrate to meet the hardness target of six grains per gallon.

The residual ozone dosage shows no compatibility issues on the UF membrane, and RO performance is stable with minimal pressure drop.