Treatment of Waste H2O

b.stev

the USED H2O of a COMMUNITY

ie: kitchen sink/ tub/ toilet shower/ laundry/ industry

o CORRECT treatment is necessary

to health

o SAVES exposure to infectious

organisms

THEN the H2O is returned to

waterways

PRIMARY: infiltration/ screening/ grit removal/

sedimentation

SECONDARY: anaerobic digestors (organic waste)

activated sludge/ trickling filters/

oxidation ponds (H2O) TERTIARY: disinfection/ wetlands/ irrigation

WASTEWATER system starts as

a complex network of pipes &

junctions that feed the material

and fluid to the treatment plant

PIPES last 20-50yrs:dependent upon material used

THE SYSTEM EXPERIENCES LOAD INCREASE FROM:

tree roots cracks

poor design installation

deterioration flood

PRIMARY TREATMENT

This load increase is known as,”INFILTRATION,”.

Maintenance is constant to :- mend

ruptures

- install new

seals

- check

apparatus

-- upgrade

areas

PREVENTS SEWER overflow and seeping

into the soil/ drains and the environment

SCREENINGFINE SCREENS intercept :

o solids plastics

o paper

o leaves

o wood

DRUM SHAPE revolves: 3 mm screens

of stainless steel that catches the debris

DEBRIS is transported offsite to a landfill

Arrival at the treatment plant :

PUMPED AIR in the FLUID

generates motion This reduces density & allows grit to settle

in HOPPERS

GRIT REMOVAL TANKS

This: GRIT, is removed offsite

ORGANIC SOLIDS ORGANIC SOLIDS remain suspended

(Water Care Services Ltd, 2008)

AUTOMATIC scrapers collectthis from a slopedsloped floorfloor removed offsite

SEDIMENTATION

FLUID & ORGANIC SOLIDS slowlyslowly

flow within big tanks, this

settles the “organic solids”

SEDIMENTATION

ANAEROBIC DIGESTORS

ACTIVATED SLUDGE

Process of Separation

[organic waste]

[wastewater]

37.5C & acid forming bacteria

breakdown organic materials

organic acids

ANAEROBIC DIGESTORS

BIOGAS: collected to generate POWER,POWER, contributes to the electricity demand in the plant

THE GAS is collected – called,”BIOGAS,”

(Water Care Services Ltd, 2008)

NEXT: methane forming bacteria utilise acids

produce methane & CO2 gas

Activated sludge

Trickling filters

Oxidation ponds

Polishing ponds

DISINFECTION

Irrigation

Wetlands

Outlet

THE PROCESS

bacteria strip out, organic

pollutants

This DECREASESDECREASES the

concentration

of pollutants in the ,”

WASTEWATERWASTEWATER,”.,”.

ACTIVATED SLUDGE

wastewaterwastewater after

the,”sedimentation,”

: aeratedaerated with O2 & saprotrophic

bacteria

(Water Care Services Ltd, 2008)

An example of an activated sludge tank:

TRICKLING FILTERS

ALGAE & BACTERIA mature the H2O

and an anaerobic sludge layer settles

OXIDATION PONDS

MOST COMMON SYSTEM used in NZ4 – 6 week stage

of treatment Large pond/s

where the H2O is,”settled

out.”

(Water Care Services Ltd, 2008)

Most effective method is to utilise, SERIES of cells, in the process

ALSO: remaining time it takes for the

human intestinal bacteria to die off

POLISHING PONDS

5 -10 day process: settles the algalalgal solids

left in the H2O after having,”settled out.”

UV gives high quality product the harbour

first: the H2O passes through sand filters

that extract particles to:

DISINFECTION

15 microns

254nm quartz tube lamp of 300W is used

Mangere Site has 7776 UV LAMPS

(Water Care Services Ltd, 2008)

CHLORINE

destroys many microbes

O2 & electricity are used = O3

removes colour from the H2O

NOT used in NZ

easy & effective

in disuse over UV - due to

the environmental impacts

OZONE

(American Chemistry Council, 2005)

ALSO:

USED FOR:

septic tank & oxidation pond effluent

&, secondary/tertiary stages of

treatment

WETLANDS5 – 10 day flow through a ,”wetland,” -

plants rooted in soil of a shallow pond

BACTERIA settle to plant stems and aeration of H2O transfers the process

IRRIGATION

H2O from the treatment plant can be used for IRRIGATION purposes

THOUGH much care is needed to ensurethe soil & vegetation is not suscepted

to microbial contamination from this.

VERY dependent: toxcity

hazard

involved with the use of land &

timing of the crops to be

grown

Bibliography

Disinfection of wastewater. (n.d). Retrieved September 18, 2008, from http//: www.me.vccs.edu/courses/ENV149/disinfectionb.htm - 5k

American Chemistry Council.Inc. (2007). Chlorine chemistry division- wastewater disinfection. Retrieved September 18, 2008, from http//: www.americanchemistry.com/s chlorine/sec content.asp?CID=1198& DID=4534&CTYPEID=107Science Learning Hub. (2008). Disinfection of wastewater.sciencelearn.hub. Retrieved September 18, 2008, from http//:www.sciencelearn.org.nz /contents/you_me_and_uv/nz_research/disinfecting_wastewater-25k

Ministry of Environment. (2005). Client. Retrieved September 18, 2008, from http//:www.nzwwa.org.nz/Guideline%20for%20Oxidation %20Ponds%202005%20Final…-

Global Water Instrumentation.Inc. (2007). Inflow and infiltration of sanitary sewer systems. Retrieved September 18, 2008, from http//:www. globalw.com/support/inflow.html – 33k

Natural Resource Management and Environmental Department. (2007). Retrieved September 18, 2008, from http//:www.fao.org/docrep/t0 551e07.htm – 129k