Environmental Health X. Rodents and Insects

Shu-Chi Chang, Ph.D., P.E., P.A.Assistant Professor1 and Division Chief2

1Department of Environmental Engineering2Division of Occupational Safety and Health,

Center for Environmental Protection and Occupational Safety and Health

National Chung Hsing University

Friday, May 11, 2007

Outline

Introduction

Introduction

Deuteronomy 32:12-13 (1500 B.C.)

Pit privy Sewage

treatment (2800 B.C.)

Water closet evolution

Individual household disposal systems

30-35% of Americans depend on on-site subsurface disposal system

Septic tank Process Drain field

Aerobic system Others: biological toile,

composting toilet, incinerating toilet, oil-flushed toilet, and vacuum toilet.

Liquid wastes – a broader perspective

Point sources Non-point sources Effects

Drinking water pollution DO consumption Fish and shellfish may be injurious Eutrophication Can block sunlight and destroy coral reef

An oxygen sag curve

Anticipated national-level priorities

Water pollution regulations

Federal Water Pollution Control Act (1956) Best available control technology Secondary sewage treatment standards EPA can enter and inspect industrial sources of pollution

Water Quality Act (1987) Permits

Measurement Quantity of contaminants

SS Nutrients Chlorine Acidity and alkalinity

Treatment indicators Organic matter: oxygen demand Nutrients and toxic chemicals

Other measurements DO BOD and COD

Treatment of municipal sewage

Three stages Primary

Settling tank to remove sand, grit, and small rocks

Remove 50% of solids and 30-50% BOD Secondary

Trickling filter (70-80%BOD removal), activated sludge process (90%BOD removal), or biological stabilization pond

Tertiary Coagulation, flocculation, sand filter, and

disinfection

Municipal sewage treatment

Trickling filter

Treatment of industrial wastes

Physical processes Remove suspended oils, greases, and emulsified

organics Remove dissolved materials Recover acid

Chemical processes Addition of acids Addition of coagulants Ion-exchange resin Oxidants

Biological processes Predigestion Oxidation

Others Deep-well injection Non-point sources

Land disposal of treated wastewater

Advantages Returning nutrients back to soil Reclamation and preservation of open space or

wetland. Allows development of new wetlands Creating an ideal environment in which natural

biological, physical, and chemical processes can stabilize the wastes

Recharging the groundwater Saving

Standards for wastewater for recycling and reuse.

Sludge disposal: fertilizers or landfill. Heavy metals tend to be concentrated.