Chapter 31 Water and Waste Treatment. Consequences of Water Pollution Disease Epidemics Early...

Chapter 31

Water and Waste Treatment

Consequences of Water Pollution

Disease EpidemicsEarly 1800’s - industrial revolution

Outbreaks of typhoid fever, cholera, TB & dysentery

1842 - Edwin Chadwick1965 - Riverside, California

16,000 cases of Salmonellosis (70 serious, 3 deaths) Unusual because pathogen out numbered coliform

indicator (E. coli)


1993 - Milwaukee, Wisconsin 400,000 cases of cryptosporidium

1998 74 athletics from triathlons in Wisconsin and Illinois

with evidence of infection three (3) hospitalized

Leptospirosis - waterbirne disease

July 2000 10 cases of hemolytic-uremic syndrome (HUS)

caused by E. coli. Came from contaminated ice


Acid-Rain Trash Littered Beaches, Dead Fish Unsightly, foul-smelling odors Accelerated Eutrophication

Consequences of Water Pollution Two (2) Important Micro Factors

Pollution problems caused by pathogenic bacteria

Pollution leading to Eutrophication Most Commonly Added Material to

Aquatic EnvironmentTreated Sewage

High in Nutrients & Phosphates

Myth vs. Fact

Streams, lakes and oceans are natural waste disposal units - WRONG

Most naturally occurring substances can be recycled, but systems can be overwhelmed

Microbial degradation is 10-100 times slower in oceans

Waste Water Treatment Definitions

Mineralization (Stabilization) Conversion by microorganisms or organic

materials into inorganic materials

Biochemical Oxygen Demand (BOD) Oxygen consuming property of a wastewater

sample Roughly proportional to the amount of degradable

organic material present in water sample Effective treatment decreases the BOD of sewage

Waste Water Treatment Definitions

Aerobic Treatment Microbial oxidation of organic compounds to yield

CO2 and inorganic nitrogen-containing nutrients for plants

Anaerobic Decomposition Similar except anaerobic microbes ferment organic

compounds Products of fermentation utilized through aerobic

respiration

Waste Water Treatment Definitions con’t

Anaerobic Decomposition, Methanogens are Important

Transforming small products from other bacteria into CO2 and CH4 (methane)

In presence of hydrogen, remaining CO2 can be metabolized by photosynthetic organisms and plants

CH4 can be discarded, conserved for fuel (perspective 33.1), or oxidized to CO2 by methane-oxidizing bacteria

Waste Water Treatment Consumption in U.S.

Every day the average American uses: 150 gallons of water 4 lbs. of food 19 lbs. of fossil fuels

Converted into: 120 gallon sewage 5 lbs. Trash 2 lbs. Air pollutants

Municipal Waste Water Treatment Primary Treatment

Removal of large objects and much of the particulate matter through the physical processes of screening and sedimentation

Sedimentation Tanks ALUM often added to aid in sedimentation Water held 90 minutes to 2 hours Effluent water is sent to secondary treatment

Municipal Waste Water Treatment

Suspended solids settling to the bottle form a mass called raw primary biosolids (formerly Sludge)

Biosolids are sent to an anaerobic digester or incinerated

Waste Water Treatment Anaerobic Digesters

Biosolids from primary sedimentation tanks Utilize Anaerobic Decomposition Following decomposition final Biosolids –

commonly burned to ash Lime is recovered and recycled if used is process

Municipal Waste Water Treatment Secondary Treatment

Designed to stabilize most of the organic material in sewage and reduce the BOD of the sewage.

Removes about 85% of organic matter

A biological process Effluent from primary treatment is pumped to a

trickling filter system then/or to an aeration tank for further stabilization.


Activated Biosolids Process (formerly Aerated Activated Sludge Process)

Sewage serves as a nutrient source for mixed populations of aerobic organisms.

Aerated to increase the oxygen levels End result - a small increase in microbial mass and a

decrease in degradable organic material Aerated activated sludge now called activated biosolids

Municipal Waste Water Treatment Secondary Treatment

Effluent from secondary treatment moves on to tertiary treatment process

Sludge moved to activated sludge digester or incinerated

Waste Water Treatment Trickling Filters

Sewage is sprayed over a bed of coarse to fine gravel and sand (3 to 6 feet deep)

Newer systems may use interlocking pieces of corrugated plastic or other synthetic material

A film of organisms comprised of fungi, algae, cyanobacteria and some protozoa cover the gravel and sand.

Organisms aerobically stabilize the wasteCan be used individually or as part of a large

system


Tertiary TreatmentChemical precipitation of phosphates and

biological removal of nitrates Lime added to coagulate and precipitate phosphate

containing particles - allowed to settle out in a clarification tank.

Certain bacteria may be used to reduce nitrates (NO3

-) to N2 or Gaseous ammonia in water may be removed by

passing water through a stripping tower

Municipal Waste Water Treatment Tertiary Treatment

Water then passes through a series of activated carbon filter units

Removes detergents, pesticides and other toxic materials

Municipal Waste Water Treatment Chlorination

Final step in waste water treatment processes Can kill more than 99% of the harmful bacteria in

effluent. Municipal treatment

Primary - chlorination Primary/Secondary - chlorination Primary/Secondary/Tertiary - chlorination


Many states now require the removal of excess chlorine before discharging to receiving waters by a process called dechlorination.

Accomplished with granulated activated carbon filtration

Alternatives to chlorination include ultraviolet light or ozonation

Small Scale Waste Water Treatment

LagooningSewage channeled into a series of small

ponds (lagoons) Remains in each lagoon for several hours to

several days or more Sedimentation occurs and waste materials are

stabilized by both aerobic and anaerobic processes.

Pathogens are usually eliminated by competition

Small Scale Waste Water Treatment Septic Tanks (Anaerobic)

Sewage is collected in a large tank where solids settle to the bottom and are stabilized anaerobically

Liquid outflow is run through a distribution box then out to a drainage field (finger system)

Liquid filters down through a gravel base and then into the surrounding soil

Works well in theory


• Septic Tanks – Anaerobic– Possible Problems

• Washing machines are leading cause of septic system failure

• Clay soil types decrease effectiveness• Toxic materials in the waste water decrease

effectiveness• Need to periodically reseed septic tank with

appropriate bacteria• Pathogens can sometimes survive process


• Septic Tanks – Aerobic

– Pretreatment• May include a traditional septic tank, a primary

settling compartment or a trash trap (screening)• To reduce greases, oils, toilet paper and other

solids.• Optional on various systems


– Aerobic Treatment Units• Main function is to collect and treat household

wastewater• Suspended Growth Units

– Main compartment called an aeration chamber. – Air mixed with wastewater (wastewater mixture called

mixed liquor).– Some units have a secondary settling chamber or

clarifier. Sediment returns to the aeration chamber as bacterial seed for growth of organisms.


• Attached Growth Units– Treat wastewater by taking a surface made of material

bacteria can attached to, then exposing surface alternately to wastewater then air.

– Requires a pretreatment component.– Example: trickling filter.

• Final Treatment and Disposal– Includes chlorination or discharge to a soil absorption

field, sand filter or evapotranspiration bed (drip irrigation).


• Septic Tanks – Aerobic– Limitations

• Regulatory regulations• High cost• Maintenance requirements

– Aerobic units are required to have two (2) year manufacturer maintenance service and renewal options.


• Septic Tanks – Aerobic– Do’s and Don’ts

• Maintain service contract• Avoid water overloading• Don’t allow anyone to drive over or park on system• Don’t use harmful chemicals• Avoid using garbage disposal• Do not dispose of coffee grounds, kitty litter, fat or

grease down drains

Small Scale Waste Water Treatment Artificial Wetlands

Sewage pumped into initial pondHeavy material settles to the bottom where it

undergoes anaerobic digestion (stabilization), water in the pond is aerated to promote aerobic stabilization of organic materials

The length of time the water stays in the pond is dependent on the design of the system


Artifical WetlandsWater is pumped from the pond into a marsh

where additional stabilization takes placeFrom the marsh water flows into another pond

where algae can transform harmful nutrientsThe water then flows into a meadow where

remaining pollutants can be trapped, water flows from the meadow into area ground or surface waters

Treated Waste Residue Problems Receiving waters can be changed if

insufficient treatment has taken place causing increased BOD & temperature, pH changes, or introduction of toxic materials

Biosolids (Sludge) - if burned produces polluting gases; can only be used as a fertilizer if no toxic compounds are present

Water Treatment (Purification) Sedimentation

Addition of either (alum) aluminum sulfate or iron sulfate to cause flocculation to occur

Flocculation Forms jelly like masses of coagulated material - Flocs

Water remains in sedimentation tank for 1 - 10 hrs.

Water flows from sedimentation tank to filtration process

Water Treatment

Filtration (2 Types of Filters)Slow Sand Filters

Fine particles of sand, several feet deep Schmutzdecke (dirty) layer forms within system to

aid in trapping organisms Can purify ~ 3 million gallons/acre/day When system efficiency decreases sand has to be

replaced

Water Treatment Filtration (2 types)

Rapid Sand Filters Coarse gravel to fine sand No dirty layer Rate of filtration is over 200 million gal/acre/day Easily cleaned by backwashing

Both filter types are effective at removing ~99% of microorganisms present in the water

Water Treatment Chlorination

Normally use Chlorine gas Water held in storage tanks for 90 minutes to

several hours.

Free residual chlorine 0.2-1.0ppm (0.5ppm)Favored in U.S. because residual chlorine will

kill organisms entering system following treatment

Can check safety level based on residuals

Water Treatment Chlorination

Can react with naturally occurring or pollution related organic materials to form chlorinated hydrocarbons

Can avoid problem by reducing organic material found in water

Granulated active carbon filters can be used to remove chlorinated hydrocarbon compounds

Water Treatment Ozonation

Ozone acts as an oxidizing agent to kill bacteria and inactivate viruses

Can also destroy some hydrocarbon compounds by oxidation

Leaves no undesirable taste or odor Removes color

Safety check requires an 18 hour delay before water is pumped out to communities

Water Treatment

OzonationUsed in several European citiesUsed by many bottled water companies in the

U.S. but few cities.

Water Testing Membrane Filter Technique

100ml water samplepassed through a membrane filter

cellulose acetate or polycarbonate

Filter placed on appropriate medium & incubated for 24 hours

Count colonies - calculate number of bacteria in original sample

Water Testing Most Probable Number Technique (MPN)

Presumptive Test Inoculate water in 10ml, 1ml and 0.1ml amounts

into lactose broth tubes Incubate 24 hours, interpret for (+) gas Use MPN table to determine number of coliform

bacteria present in sample This number is used to determine if water is safe to drink,

swim in, etc. It does not detect total number of bacteria in the water

Water Testing Most Probable Number (MPN)

Confirmed Test Transfer sample from (+) gas lactose tube to EMB plate Incubate 24 hours If coliform colonies form (+)

Completed Test Select an isolated colony from EMB plate and inoculate

a lactose broth tube Incubate & check for gas production

Solid Waste Treatment The U.S. creates more than 150 million

tons of solid waste material per year Solid Waste Sanitary Landfills

Each days waste is covered with a layer of dirtWhen landfill becomes full it is generally made

into a meadow areaConcept is to have the land used for

recreational purposes and then later as construction sites

Solid Waste Treatment

Sanitary Landfills - DisadvantagesLimited number of sites availableOrganic content degraded slowly anaerobically

can take 50 years or more

Methane gas is a by-product, can be explosiveHeavy metals and pesticides leach into

surrounding groundwater


Some cities are beginning to charge based on the size of trash container picked up

Recycling is becoming more and more important

Solid Waste Treatment Backyard and Commercial Composting

Involves mixing garden debris with organic kitchen wastes (excluding meats & fats)

Requires periodic mixing to maintain even temperature (best temp range 100-150oF)


Will reduce the bulk by 2/3s over a period of several months

Pathogens are killed but beneficial thermophils survive

Bioremediation

PollutantsTraditionally degraded and removed through

natural recycling. Most natural organic compounds can be degraded

by one or more species of soil or aquatic organisms Industrially synthesized chemicals slowly degraded

or nonbiodegradable Adds thousands of tons of pesticides, herbicides,

detergents and plastics to the environment

Bioremediation Pollutants

Biological Magnification

Continuing ingestion and reingestion of a compound accumulating in fat resulting in an increasing concentration of the compound as it is passed up the food web.

Example: DDT

Bioremediation Changing biodegradability

Herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-

trichlorophenoxyacetic acid (2,4,5-T) Only difference is the additional chlorine atom on

2,4,5-T When 2,4-D applied to soil it disappears

completely in a matter of weeks while 2,4,5-T remains more than one year later

Therefore 2,4-D more biodegradable

Bioremediation Increasing microorganisms will also increase rate of

degradation Raising temperature, maintaining pH near neutral and

providing optimal moisture will likely increase the rate of degradation of most materials added to the soil

Polychlorinated biphenols (PCBs) Aromatic molecules Not biodegradable Concentrations increasing steadily for several years Banned in U.S. in 1978 1/3 of the U.S. population is estimated to contain PCBs in

concentrations greater than 1 ppm in their tissues

Natural Materials – Petroleum Oil

Bioremediation

Means of BioremediationMicroorganisms

Large scale inoculation of polluted areas or introduction of the necessary degradative capabilities into the natural population of a given area.

Dual cultures of Acinetobacter and Pseudomonas can degrade PCBs

Chapter 31 Water and Waste Treatment. Consequences of Water Pollution Disease Epidemics Early...

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