Sewage Sewage We all know what we flush down the toilet or what - PowerPoint Presentation

Slide1

SewageSlide2

Sewage

We all know what we flush down the toilet or what

we pour

down the drain. What happens to all that stuff?

In

answering the above question, keep in mind the

first law

of thermodynamics, the bit about neither

being created

nor destroyed but changing from one form

to another

.

Just

because you flush it doesn’t mean that it

disappears forever

.Slide3

Historical Context of Sewage

Important note: prior to the 1970’s most of

the raw

sewage, the stuff coming out of the

houses, was

simply dumped into the environment

– usually

within rivers or oceans.

The book mentions

that the mistreatment of sewage is

one of

the main instigators of the Clean Water

Act (1972

).

The

Clean Water Act (CWA) helped

establish modern

sewage treatment by

appropriating funds

to local and state governments to build

or revise

existing plants.Slide4

Sewage Treatment

Modern Sewage Treatment = based on

the filtration and biological decomposition.Slide5

Sewage Treatment

The raw sewage contains at least these

four components:

–

Debris

(toilet paper, feminine products, other things that get

flushed)

–

Particulate organic mater

–

Colloidal dissolved organic mater

(things in solution or partial

solution, like urine

–

Dissolved inorganic mater

–

Misc. ChemicalsSlide6

Sewage Treatment

Preliminary = the raw sewage flows out of

your house to a sewer line, which eventually

leads to a municipal treatment plant.

In the preliminary

stage the raw sewage is filtered

through a 1” mesh. The solids and paper that

accumulates on the mesh screen is raked off

and transported to an incinerator or taken to a

landfill.Slide7

Sewage Treatment

Primary Stage = after passing through the

preliminary filtration, the raw sewage flows to a

circulation chamber.

Here

the sewage is slowly

circulated – the change in the velocity causes

the

courser materials, such as grit and other bits

of organics, to settle out. The stuff that settles at

the bottom is referred to as sludge; it is removed

and taken to a landfill by dump trucks. In

addition, grease, fats, and oils will float on the

surface. These fatty materials are siphoned off

and merged with the sludge.Slide8

Sewage Treatment

Secondary Treatment = in this stage of sewage

treatment the remaining dissolved organics and

nutrients are

broken down via aerobic

and anaerobic decomposition

.

The sewage

is aerated with oxygen and

decomposing bacteria

are added. The bacteria “feed” on the

organic materials

left in the water and utilize the

remaining nutrients

.Slide9

Sewage Treatment

After biological decomposition, the water is

then sterilized

, by either chlorine or ozone

gas, or ________.

Then it

is released

back into the environment.

Usually municipal treatment

facilities pump the treated sewage into a

river or

pump it out into the ocean. Water exiting the

sewage treatment

facility (gray water) in many places is

cleaner than

that which comes out of your tap.Slide10
Slide11
Slide12

Secondary TreatmentSlide13

Processing of sludgeSlide14

Gray Water

In many cities the water exiting

the sewage

treatment plant is reused.

Some cities

use gray water to water lawns..

However in major metropolitan

areas where

water is scarce – the desert west

– gray

water might be an option for

drinking water

?Slide15

Septic System

Waste leaving the home flows through a

septic tank

. In the tank the solids settle towards

the bottom

.

Here

the organics breakdown

through aerobic

and anaerobic decomposition.

The colloidal

and dissolved

in-organics

flow out

into the

yard via a drain field.

The

effluent

is supposedly

filtered naturally by the

lawns, gardens

, and soil microbes.Slide16
Slide17

Septic Tank Problems

Septic tanks have to be cleaned out about

every 5

years depending on usage. If there are

more solids

than the system can handle, the tank

will backflow

and the sewage treatment

becomes ineffective

.

Leaking

septic

systems,

or

poorly working ones,

can leak too much raw

sewage into

the environment.

If

too much water

passes through

the septic system, it will turn the yard

all mushy.

Slide18

Septic Tank Problems

Also if there are too many septic systems

built within

too small of an area, the sewage will

not be

properly filtered or broken down. The

excess nutrients

and organics will contaminate

the groundwater

.Slide19

Sewage Ponds

Many

newer communities are

using sewage

ponds to treat their waste.

The sewage

ponds also employ

biological decomposition

.

In

this case the

raw sewage

is pumped into a containing pond.

The solids accumulate at the bottom of

the pond

.

The

organic materials are

feasted on

by decomposers.

Aquatic

vegetation

is also

planted. The vegetation uses

theorganics

and nutrients as fertilizers.Slide20

Clean Water Act 1972

The Clean Water Act is the sister of

the Clean

Air Act. It was the first legislation

of its

kind to protect the Nation’s waters

and to

create safe drinking water

.

During the Environmental Movement

there was

a push to clean up polluted water.Slide21

Clean Water Act

This was in large part due to:

– Accumulating sewage

– Factory

effluents (discharge)

from the

Chemical Revolution

– People getting sick from polluted water (

see the

movie A Civil Action).

– The Cuyahoga River caught fire in 1967Slide22

Clean Water Act 1972

The Clean Water Act:

–Gave

the EPA the power to set regulations

on sewage

effluent

–Appropriated

funds to local governments to

retool poorly

working sewage treatment

– Gave power to the EPA to regulate the amount

of pollutants

emitted by factories

– Protected the US waterways (“Navigable

Waterways”). Under this definition wetlands

are designated

“navigable waterways”, and the

CWA gave

power to the Army Corp of Engineers to

protect wetlands

.Slide23

Clean Water Act 1972

The Safe Drinking Water Act 1974 (from the same

vein as

the CWA) authorized EPA to regulate the quality

of public

drinking water and to set drinking water standards