1. VI. Purpose of Water Treatment
A. Objectives,
B. Regulatory approaches, and
water quality standards

2. Learning Objectives:
List and describe some of the main objectives of drinking water and wastewater treatment.
Distinguish between two primary approaches to water quality regulation.

3. Goals of Water Treatment:
To Protect the health of community (Portability, or primary drinking water standards).
To supply water that is aesthetically desirable (Palatability, or secondary drinking water standard).
To protect the property of the consumers
All the above criteria should be achieved at a reasonable cost.

4. Potability of water:
Microorganisms (pathogens) can contaminate water and make it unsafe for drinking (transmit infectious diseases).
Surface sources of drinking water require disinfection, as well as some groundwater sources.
Chemical contaminants (such as Arsenic, Mercury, Chromium, Cadmium, Aluminum) can also make water unsafe for drinking purposes.

5. Palatability of water:
Palatability is related to several factors:
Color,
Taste,
Odor,
Sediments,
Cloudiness (turbidity), etc.
These may indicate chemical or micro-biological contaminants (potability).

6. Regulatory Approaches - for Drinking Water
Drinking water standards for a variety of potential contaminants are set by the EPA to protect public health.
The 1974 Safe Drinking Water Act established Maximum Contaminant Levels (MCL’s) for water contaminants.

7. Water quality criteria (MCLG)
Evidence of human exposure
Threshold levels determined for long-term exposure (“No Observed Adverse Effects Levels”, or NOAEL’s)
Educated guess
Application of mathematical models
Maximum Contamination Level GoaL (MCLG) established.

8. How water quality standards (MCL) are established:
Standards are established on the basis of one or more of the following:
Scientific evaluation (Criteria); MCLG
Technical attainability;
Economic attainability;
Legal enforceability;
Established on ongoing practice,...

9. Regulatory Approaches for wastewaters
No-Degradation Principle (including effluent standards and stream standards)
This is an attempt to meet the “no-pollutant discharge” (NPDES) objective of the Clean Water Act.

10. Summary:
Water treatment has two primary objectives: to make water potable (safe to drink) and palatable (aesthetically acceptable for drinking).
Water quality regulations for drinking water are primarily based on MCL, while wastewater standards are primarily based on minimum degradation.