Wastewater Treatment

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 

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 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