The place to start when talking about Newark drinking water is at the source.  The City of Newark obtains its drinking water from 3 sources:  surface water, ground water and purchase water.  Last year, 40% was surface water obtained from White Clay Creek, 31% was ground water obtained from the Laird Tract Wells and the South Well Field and the remaining 29 % was purchased from United Water of Delaware during periods of low base flow.
The Newark Water Treatment Facility is located north of Newark off of Paper Mill Road.  The water is pumped directly from White Clay Creek.  During times of drought or flood levels when the flow rate is too high or too low to use the treatment facility, water is purchased from United Water of Delaware which has their own treatment facility in Stanton, DE.
Aluminum Sulfate and Polymer are added to create "floc" in the water. Floc is tiny sticky particles that attract dirt in the water and the conglomerate settles out to the bottom where it is removed.  Mixed media filtration is used to remove even smaller particles.  Here in Newark, a mixture of anthracite coal, manganese green sand, and high density sand are used.  Chlorine is used to kill bacteria and other microorganisms, Calcium Hydroxide adjusts the pH of the water, and fluoride is added to promote strong teeth among comsumers.
A Corrosion Inhibitor is used in Newark due to the age and quality of area plumbing.  This inhibitor helps prevent copper and iron from leaching into the drinking water as it travels from the treatment plant to the tap. Sometimes powdered activated carbon is also added to remove organic contaminants as well as color-, taste- and odor-causing components.