Drinking Water Treatment involves the removal of pathogens and other contaminants from source water in order to make it safe for humans to consume. Treatment of public drinking water is mandated by the Environmental Protection Agency (EPA) in the U.S. Common examples of contaminants that need to be treated and removed from water before it is considered potable are microorganisms, disinfectants, disinfection byproducts, inorganic chemicals, organic chemicals and radionuclides.

There are a variety of technologies and processes that can be used to decontaminate or treat water in a drinking water treatment plant before the clean water is pumped into the water distribution system for consumption.

Drinking Water Treatment Plant

The first stage in treating drinking water is often called pretreatment and involves screens to remove large debris and objects from the water supply. Aeration can also be used in the pretreatment phase. By mixing air and water, unwanted gases and minerals are removed and the water improves in color, taste and odor.

The second stage in the drinking water treatment process involves coagulation and flocculation. A coagulating agent is added to the water which causes suspended particles to stick together into clumps of material called floc. In sedimentation basins, the heavier floc separates from the water supply and sinks to form sludge, allowing the less turbid water to continue through the process.

During the filtration stage, smaller particles not removed by flocculation are removed from the treated water by running the water through a series of filters. Filter media can include sand, granulated carbon or manufactured membranes. Filtration using reverse osmosis membranes is a critical component of removing salt particles where desalination is being used to treat brackish water or seawater into drinking water.

Following filtration, the water is disinfected to kill or disable any microbes or viruses that could make the consumer sick. The most traditional disinfection method for treating drinking water uses chlorine or chloramines. However, new drinking water disinfection methods are constantly coming to market. Two disinfection methods that have been gaining traction use ozone and ultra-violet (UV) light to disinfect the water supply.

Introduction to drinking water treatment

A Guide to Drinking Water Treatment Technologies for Household Use

This document is designed as a guide for household water treatment, not a recommendation. Before installing a household water treatment system, contact your local health department’s environmental health group for consultation.

Treatment technologies for small drinking water systems

Water Supply – Part 3 of 3: Water Treatment

Drinking Water Treatment Technology Unit Cost Models and Overview of Technologies

Drinking water treatment technology unit cost models
Federal laws and executive orders require EPA to estimate compliance costs for new drinking water standards. The three major components of compliance costs are:

Treatment
Monitoring
Administrative costs

Treatment technologies remove or destroy pollutants (such as arsenic, disinfection byproducts, and waterborne pathogens).

To estimate treatment costs, EPA developed several engineering models using a bottom-up approach known as work breakdown structure (WBS). The WBS models:

Derive system-level costs
Provide EPA with comprehensive, flexible and transparent tools to help estimate treatment costs
Each WBS engineering model contains a work breakdown for a particular treatment process.

Engineering equations estimate equipment requirements given user-defined inputs such as design and average flow. Each model has many design assumptions (such as redundancy requirements). The models provide unit cost and total cost information by component.

Intake for drinking water treatment

Coagulation and Flocculation

Sedimentation

Filtration

Membrane Filtration

Reverse Osmosis

Adsorption and Ion Exchange

Disinfection

Water Distribution

Sustainable Water Treatment Concepts

The Genifuel system combines two separate processes to transform wastewater sludge into fuel. The first step produces a type of oil called biocrude, while the second creates methane, the main component of natural gas. The two techniques are specific types of a procedure called hydrothermal processing, which uses high temperatures and pressures to produce useful products from wet materials that contain organic compounds, or substances made up of carbon. While hydrothermal processing has been around since the 1930s, recent improvements have made it potentially cost-competitive for the first time, said Corrine Drennan, who oversees PNNL’s bioenergy technology research.