Waste and wastewater produced by residential and commercial users that is discharged into sewersEx: Human waste, soaps, paints, oils

Storms intensify spread->wash off into drainage systems

MicroorganismsViruses, bacteria, protozoa and parasitesCan spread waterborne diseases via fecal-oral

transmission

PathogensMicroorganisms that can cause diseaseCan cause diarrhea, schistosomiasis (disease

caused by parasitic worms), intestinal worms, and river blindness

• Eliminates up to 99.99% of microorganisms– Drinking water: Chlorine- kills

microorganisms Filtration- removes particulate

matter• Collected and transported via a network

of pipes and pump stations to a municipal treatment plant

Primarysolids are separated

Secondarydissolved biological matter is converted

into a solid mass by using water-borne bacteria

95% of the suspended molecules should be removed

Tertiarybiological solids are neutralized then

disposed, and treated water may be disinfected chemically or physically

Mechanical treatment Influx (Influent) Removal of large objects Removal of sand and grit Primary Sedimentation

Biological treatmentTrickling bed filterActivated sludge

Chemical treatmentDisinfection

Remove large objects Ex: sticks, rags, toilet paper, tampons

Raked screen Clog equipment in sewage treatment plant

Typical materials that are removed during primary treatment include fats, oils, and greases (aka FOG) sand, gravels and rocks (aka grit) larger settleable solids including human waste floating materials

Primary Sedimentation TankRemove grease, oilFecal solid settle, floating material rise to the

surfaceProduce a homologous liquid for later biological

treatmentFecal sludge are pumped to sludge treatment

plant

Degrade biological content (dissolved organic matter) of the sewageEx: human waste, food waste, soaps,

detergent Added bacteria and protozoa into

sewage 3 different approaches

Fixed film systemSuspended film systemLagoon system

1. Fixed Film Systems– grow microorganisms on substrates such as

rocks, sand or plastic – wastewater is spread over the substrate– Ex: Trickling filters, rotating biological contactors

Trickling Filter BedsSpread wastewater over microorganismmade of coke (carbonized coal), limestone chips or

specially fabricated plastic mediaOptimize their thickness by insect or worm grazing

2. Suspended Film Systems stir and suspend microorganisms in wastewater settled out as a sludge pumped back into the incoming wastewater Ex: Activated sludge, extended aeration

Mixed community of microorganisms Both aerobic and anaerobic bacteria may

exist Biological floc is formed (bacteria and

protozoa)

1. Aeration tank oxygen is introduced into the system

2. Aeration source – ensure that adequate oxygen is fed into the tank – provided pure oxygen or compressed air

3. Secondary clarifiers – activated-sludge solids separate from the

surrounding wastewater

4. Activated sludge outflow line– Pump activated sludge back to the aeration tank

5. Effluent outflow line– discharged effluent into bay or tertiary treatment plant

Sewage Treatment

Remove disease-causing organisms from wastewater

3 different disinfection processChlorinationUV light radiationOzonation

Most common Advantages: low cost & effective Disadvantages: chlorine residue could be harmful to

environment

• Damage the genetic structure of bacteria, viruses and other pathogens.

• Advantages: no chemicals are used• water taste more natural• Disadvantages:

high maintenance

of the UV-lamp

Oxidized most pathogenic microorganisms Advantages: safer than chlorination

fewer disinfection by-product Disadvantage: high cost

Measures the number of coliform bacteria per 100 milliliters

Coliform lives in guts of most mammals Do not usually cause disease->used as

proxy for presence of other microorganisms that can cause diseaseWater should have a count of 0Swimming or “full body contact”-count

<200

Not available in many developing nations

250 million cases of waterborne disease each year killing 5-100 million people

Children highly susceptibleDiarrheal disease->underweight,

mental/physical hanidcaps, vulnerable to other diseases

Discharging too much into surface waters can cause eutrophication (decreases oxygen levels)Microorganisms metabolize organic wastes-

>use oxygen faster than it can reenter atmosphere

If water becomes anoxic, decomposition proceeds anaerobically, and releases noxic gases

Increase in algae growth Increase in zooplankton

Even more eutrophicationOxygen depletionZooplankton and fish suffocate or are

poisoned by toxinsWater has a foul taste and odor

***Focus on Phosphorus•Waste water treatment•Ban on Phosphorus containing detergents•Reduce use of fertilizers•Control agricultural runoff•Reduce use of phosphorus in animal feed ->less phosphorus in manure

Sediments, heavy metals, xenobiotics (organic compounds that are synthesized by humans and are resistant to organic decay)Heavy metals->greatest threat: cancer,

damage to nervous system, birth defectsHighest concern: lead, mercury, cadmium,

and arsenic

Point: directly discharged into a body of waterEx: Pipe or smokestackEx: GE and Hudson River->PCB’s

Nonpoint: not discharged from a specific pointEx: pesticides and herbicides

Leach through soil and contaminate ground water

Runoff from farms into other bodies of water