Wastewater Treatment

Water Pollution

Water Pollution Any chemical, biological, or physical change in

water quality that has a harmful effect on living organisms or makes water unsuitable for desired uses Point source

Specific location (ex. drain pipes, ditches, sewer lines) Non-point source

Cannot be traced to a single site of discharge (ex. atmospheric deposition, agriculture/industrial/residential runoff)

Laws

Clean Water Act 1972 – Federal Water Pollution Control Act

Amendments EPA required technology-based effluent standards and

permits for all discharges from point sources 1977 – Clean Water Act Amendments

New technology based program for toxic pollutants 1987 – Water Quality Act

Control toxic hot spots and non-point sources

Laws Major Provisions of the CWA

National Goals Elimination of pollution discharges

Research and Grant Programs Clean up for Chesapeake Bay and Great Lakes

Construction Grants Sewage treatment plants

Standards and Enforcement Effluent limitations

Permits and Licenses National Pollutant Discharge Elimination System permit

General Provisions Citizen suits and judicial review

Prevention and Reduction

Prevent groundwater contamination Reduce non-point runoff Reuse treated wastewater for irrigation Find substitutes for toxic pollutants Work with nature to treat sewage Monitoring Separate sewage and storm lines Proper disposal of waste materials Practice four R’s of resource use (refuse, reduce,

recycle, reuse)

Water Treatment

Why treat water? To eliminate organic and inorganic wastes Organic

Fecal matter – coliform test (bacteria found in intestines in warm blooded animals, ex. E. coli) Drinking water 0 colonies / 100 mL Water treatment 2000 colonies / 100 mL Swimming 200 colonies / 100 mL

Inorganic Mercury and phosphates

Water Treatment Water comes from watersheds, lakes, streams,

rivers, etc. 1. Sedimentation

Sediments out only large particles 2. Flocculation

Flocculation chemicals are added Aluminum sulfate (alum) Bind organic matter – form clumps called flocs

3. Filtration Typically made of sand blocks organic matter Over 99% of microbes now removed

4. Chlorination Kills any remaining microbes Less than 30 minutes Treats pipes from water treatment storage home

Prevents biofilms from forming

Sewage Treatment Removes organic matter and is measured by

Biochemical Oxygen Demand (B.O.D.) How much B.O.D. is needed to break down organic matter More sewage means more B.O.D.

Primary Sewage Treatment Physical process

Secondary Sewage Treatment Biological process

Tertiary (Advanced) Treatment Series of specialized chemical and physical processes to

remove specific pollutants left in the water after primary and secondary treatment.

Sewage Treatment

Primary Treatment Screening and Grit Chamber

Remove large floating objects and allow solids such as sand and rock to settle out

Primary Settling Tank Suspended organic solids settle out as sludge

What is removed? Removes 60% of suspended solids Removes 30-40% of the B.O.D. organic wastes Pathogens, phosphates, nitrates, salts, pesticides, and

radioactive isotopes remain

Sewage Treatment

Secondary Treatment Aerobic

1. Activated Sludge Aeration Oxygen pumped in; more oxygen means more

breaking down B.O.D. decreases 75-95%

2. Trickling System Round vats with rotating sprayers Decreases B.O.D. 85%

Anaerobic 1. Sludge tank/bioreactors/anaerobic sludge

digestor Comes in layers (gas, scrum, supernatant, actively

digesting sludge, stabilizing sludge) Anaerobic microbes digest solid portion and give

off methane and carbon dioxide Stabilized sludge can be used as fertilizer 30 days

Primary and Secondary Sewage Treatment

http://www.youtube.com/watch?v=GV-DoisLwm0

Sewage Treatment

Primary and Secondary Treatment Overview 95-97% B.O.D. removed 70% of most toxic metal compounds and synthetic

chemicals removed 50% of nitrogen removed 5% of salts dissolved Radioactive isotopes, organic substances

(pesticides), and pathogens remain

Sewage Treatment Tertiary (Advanced) Treatment

Special filters to remove phosphates and nitrates Chlorination

Bleaching to remove water coloration and disinfect to kill disease-carrying bacteria and some viruses

May have harmful health effects such as the increase risk of cancer, miscarriages, and damage to the nervous, immune, and endocrine systems

Ozone and ultraviolet (UV) light may be used, but cost more and are not as effective

Ex. Peru stopped chlorination, but resumed after a 1991 cholera outbreak which infected more than 300,000 people and caused at least 3,500 deaths

Sewage Treatment Overview

Greensburg Sewage Treatment http://www.ggsa.us/ Greater Greensburg Sewage Authority (GGSA) Greater Greensburg Wastewater Treatment Plant

(WWTP) Treats 6.75 million gallons of wastewater per day Preliminary screening, grit removal, primary sedimentation

combined carbonaceous and nitrogenous BOD5 removal in a conventional activated sludge system, final sedimentation, chlorination, and dechlorination.

Gravity thickening for primary sludge, mechanical concentrators for waste activated sludge, two-stage anaerobic digestion, and mechanical dewatering.

Approximately 9,800 customers

Overview

U.S. Federal Law Requires primary and secondary treatment for all

municipal sewage treatment plants Exemptions from secondary treatment possible if there

is an excessive financial burden According to EPA, two-thirds of sewage treatment plants

have violated water pollution regulations, many of them minor

500 cities failed to meet federal standards for sewage treatment plants

34 East Cost cities only screen out large floating objects from their sewage before discharging into coastal waters

Overview

Network of Pipes Some cities have separate pipes for carrying runoff of

storm water 1,200 U.S. cities have combined sewer lines for these two

systems (cheaper) Heavy rains or too many users can cause Combined Sewer

Overflow (C.S.O.) Discharge untreated water directly into surface water According to EPA, at least 40,000 overflows per year in the

United States EPA estimate that 7.1 million get sick each year from

swimming in CSO or storm-water runoff contaminated waters

Sludge

Sewage Treatment produces Sludge Contains bacteria-laden solids and toxic chemicals and

metals 9% is placed in digesters and converted to compost 36% fertilizes farmland, forests, degraded land, etc. 55% dumped in conventional landfills

Solutions? Ban release of toxic and hazardous wastes from water Eliminate the use and waste of toxic chemicals Waterless composting toilet systems Wetlands to treat sewage