Ambiental

INCI 4008 Lectures (spring semester, 2009)

4. Water Quality Management (Chapter 5, textbook)
Dr. Yang Deng
Dept of Civil Engineering and Surveying, University of Puerto Rico at Mayaguez Mayaguez, PR, USA

INCI 4008 Lectures (spring semester, 2008)

4. 1 Water Pollutants and Their Sources

Dr. Yang Deng
Dept of Civil Engineering and Surveying, University of Puerto Rico at MayaguezMayaguez, PR, USA

Sources of Water Pollution
• Point sources • Non-point sources

Point sources
• Point sources -defined as localized discharges of contaminants • Include:
o o o o domestic wastewater discharge combined-sewer overflow Industrial discharge Animal feeding operation (AFOs)

Point sources – 1. domestic wastewater discharge
Domestic wastewater treatment plants discharge theireffluents into rivers, lakes, and oceans (receiving water bodies).
You should consider: • for river/lake discharge, dissolved oxygen depletion and nutrient; • for ocean discharge, pathogen and heavy metals

Point sources – 1.domestic wastewater discharge
• Septic tanks: Septic tanks are on-site domestic wastewater treatment system. The dissolved organics in the effluents are greatlydecreased.
However, the effluents still contains a number of pathogenic microorganisms, e.g viruses. As a result, they contaimiante the groundwater

Point sources – 1.domestic wastewater discharge
• Septic tanks: 50 million residents of the US (29% of population) are using septic tanks now.

Point sources – 2. combined-sewer overflow (CSOs)
• CSOs: - a sewer system that collects domestic sewage,rianwater runoff, and industrial wastewater into the SAME pipe.

Question: what is the problem if we use CSOs?

Point sources – 2. combined-sewer overflow (CSOs)
Dry weather (most of time), CSOs transport their wastewater to a sewage treatment plant for treatment Wet weather (during the periods of heavy rain or snowmelt), the volume of wastewater excesses the capacity of sewer or treatmentplant, so CSOs are designed to overflow occasionally and discharge excess wastewater directly to nearby streams

Point sources – 2. combined-sewer overflow (CSOs)

CSOs

Separate system

Point sources – 2. combined-sewer overflow (CSOs) So CSOs design has been banned in the US!

However, the old CSOs are still existing in old cities and towns of US

Point sources – combined-seweroverflow (CSOs) CSOs distribution in the US!

Point sources – 3. industrial discharge
What may be contained in industrial discharge?

Nutrients, heavy metals, toxic organic chemicals, heat……

Point sources – 3. industrial discharge
Full treatment Sewage Pre-treatment treatment plant

Industrial discharge

River, lake, etc

Point sources – 4. Animal Feeding Operations (AFOs)
AFOs -the facilities (1) where animals are fed and confined for 45 days or more in any 12 consecutive months; (2) Where crops, vegetation, forage growth, or postharvest residues are not sustained in the normal growing season over any portion of the lot

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Point sources – 5. spill
Accidental or intentional release
e.g. • transportation accidents;
Oil leaks from anoil tanker ship that collided with another ship at in the Pacific Ocean

Point sources – 5. spill
Accidental or intentional release
e.g. • Leakage and spill from underground storage tanks (UST)

• •

LUST - Leaky Underground Storage Tanks 22% of the 1.2 million UST are LUST

Nonpoint sources
Nonpoint sources -defined as pollution sources that are distributed over large areas or arecomposite of many point sources Include:
• Agricultural runoff; • Urban runoff; • Livestock, landfills, etc

Nonpoint sources
Most widespread nonpoint-sources contaminants in the US are:
Eroded sediments; Fertilizers; Pesticides.

Pollution caused by nonpoint sources >> caused by point sources !!!

Nonpoint sources – 1. agricultural runoff
Agricultural runoff: Pesticides Herbicides;...