Water Treatment Process

Water Treatment at the Dodd Water Treatment Plant

This slideshow provides an overview of how water is treated at our Dodd Plant.

Treatment Process

Treatment Process Overview: From beginning to end, including intake, debris removal, rapid mix, flocculation, sedimentation, filtration, disinfection, and finally distribution.

Rapid Mix

Chemicals are added at the base of the rapid mix basin. The raw water enters the rapid mix basin, and flows over the open weir gates into two pretreatment trains.


The flocculation basins consist of two trains, each with a total design capacity of 8.25 million gallons per day. Each train has three flocculation stages, each with a successively decreasing velocity gradient, as shown in the slide. This allows for the formation or larger floc particles.


Again, there are two trains in which the water can flow, each with a 8.25 million gallon per day capacity. The plate settlers remove the floc partiles, iron, and manganese. The residuals settle to the floor of the basin and are then removed with a hoseless vac system that moves along the floor.  

Membrane Filtration

The membrane filtration system consists of four rows, each containing four racks each of membrane modules. The capacity per row is 3.3 MGD, allowing for 10 MGD firm capacity with one row to be redundant. The membranes achieve a 3 log removal of Giardia lamblia and Cryptosporidium. 

Chemical Addition

Sodium is added for disinfection, Caustic Soda is added for pH and distribution system corrosions control. Fluoride is also added at this point to promote dental health. Before distribution, the pH, temperature, free chlorine, and fluoride are analyzed as well as the already existing turbidity.


Clearwell Pumps to Distribution System: The high service pump station consists of five pumps, each with a 2.67 million gallon per day capacity. One pump is redundant. The pump speed is controlled via variable frequency drives. Here the water is pumped into the distribution system, completing the treatment and distribution process at the Dodd Water Treatment Plant


Water Quality

Water Treatment




Water Service

Annual Water Quality Report

Left Hand Water District