Wastewater Treatment

Sources of Wastewater :

1. 
   
2. Wastewater (W/w)
   

•Is water used

•Includes substances such as human waste, food scraps, oils, soaps, and chemicals

•Also includes stormwater runoff

2.  W/w is describe by its flow (volume) and quality of characteristics.

3.  Flow rates:

ØDomestic w/w

ØIndustrial w/w

ØInfiltration & inflow into sewer lines

ØStormwater runoff

4.  Quality of characteristics:

ØCan be defined by physical, chemical and biologicalcharacteristics

Sources of contaminants :

1. 
   
2. Contaminants in municipal w/w are introduced as a result of water usage for:
   

ØDomestic, commercial, or institutional purposes

ØWater usage for product processing or cooling purposes within industries discharging liquid effluent into municipal sewerage systems

ØAnd infiltration/inflow and/or stormwater runoff

2. There are 2 sources of water pollutants:

ØPoint sources

ØNon-point sources

3. Industrial w/w can affect w/w treatment plants if such w/w is introduced into municipal sewerage systems

4. The pollution characteristics of industrial w/w with definable effect on sewer and treatment plants include:

ØBOD (High BOD = organic overload)

ØSuspended solids (Can create operational problems due to excess sludge and solid production)

ØFloating & colored material (related to visible pollution)

ØVolume (High volume = hydraulic overload)

ØOther harmful constituents includes: toxic metal ions, acid and alkalis, detergents.

Wastewater Minimization :

1. 
   
2. W/w minimization can be considered in term of:
   

ØVolume (or flow) reduction

ØStrength (or pollutant concentration) reduction

ØOr combination of these reductions

2. Emphases on flow rate reductions = involved both municipal and industrial w/w

3. Emphases on pollutant concentration reduction = are the focus attention within industries

4. Municipalities also emphasize decrease in pollutant concentration via pretreatment ordinances for industries discharging w/w into municipal sewerage system

5. Benefits resulting from w/w minimization include the following:

•Reductions of flow and w/w loadings on existing plants with finite available capacities

•Minimization of hydraulic or organic overloads and toxicity effects on existing treatment facilities

•Reductions in operation and maintenance costs for wastewater treatment

•Reductions in energy requirements within municipalities and industries

•Reductions in water usage demands on limited water supplies in specific areas

•Reduction in undesirable impacts on receiving water quality and aquatic ecology

Wastewater treatment Plant:

1. 
   
2. Sewage treatment
   
3. W/w treatment:
   

•Is a process of removing contaminants from w/w, both runoff (effluents) and domestic

•It includes physical, chemical and biological processes to remove physical, chemical and biological contaminants

•The w/w must be treated before release back to the environment

3. Purpose of wastewater treatment:

•To produce a waste stream (or treated effluent) & a solid waste/sludge suitable for discharge or reuse back into the environment

Indoor Wastewater Treatment Plant

1. 
   
2. Ecological engineering
   
3. 1st introduced by Howard Odum & others
   
4. 5 concepts key to ecological engineering:
   

•It is based on the self designing capacity of ecosystems

•It can be a field test of ecological theory

•It relies on integrated system approaches

•It conserves non-renewable energy

•It supports biological conservation

4. This system is combination of diff. plants & animals, including algae, rooted aquatic plants, clams, snails and fish.

5. Technically the H2O that has flowed through a such system is drinkable, although few people feel comfortable to do so. Plus, the final effluent is used to flush toilets or for irrigation (pengairan)

Septictank Disposal System :

1. 
   
2. Apply in rural areas = becoz no central sewage systems facilities are available
   
3. Septic system allow:
   

ØSolids to settle in a tank, where bacteria decompose them

ØLiquids percolate through soil, where soil bacteria presumably purity them

3. The term septic = refers to the anaerobic bacterial environment that develops in tank which decomposes or mineralizes the waste discharged into the tank

4. This system may fail because of failure to pump out the septic tank when it is full of solids, and poor soil drainage which allows the effluent to rise to the surface in wet weather

5. Description of this system:

1. 
   
2. The sewer line from the house leads to an underground septic tank in the yard
   
3. The tank is designed:
   

to separate solids from liquids

digest (biochemically)

store organic matter

through a period of detention

allow the clarified liquid to discharged into the drain field (absorption field) fromsystem of piping through which the treated sewage seeps into surrounding soil

c. As the wastewater moves through the soil, it is further treated by the natural processes of oxidation and filtering

d. By the time the water reaches any fresh water supply, it should be safe for other uses

Wastewater Treatment Plant:

1. 
   
2. Apply in urban areas
   
3. Is the site where the raw wastewater is processed before it is discharged back to the environment
   
4. Occurs at specially designed plants that accept municipal sewage from homes, businesses and industrial sites
   
5. Functions of this system: provide human health, ecosystem stability, and water quality
   
6. Main purpose of this system: to breakdown & reduce BOD as well as kill bacteria with chlorine
   
7. Generally, there are 3 stages of treatment in w/w treatment plant:
   

Primary Treatment (Mechanical Treatment)

1. 
   
2. Physically separate large solids from the waste stream with bar screen and settling tanks
   
3. The sewage next enters the grit chamber, where sand, small stones and grit are removed and disposed off
   
4. The sewage then enters the primary sedimentation tank, where particulate matter settles out to form a sludge
   
5. The sludge is incinerated (bakar habis), composted or used as soil amendment
   
6. In some cases, the sludge can’t be used to improve soil if the sludge contains heavy metals and toxic chemicals
   
7. The primary treatment remove 30-40% of BOD by volume from the wastewater
   

Secondary Treatment (Biological Treatment)

1. 
   
2. The w/w from the primary sedimentation tank, which carry pathogens and organics, enter aeration tank
   
3. In the aeration tank, the effluent is aerated, in which air is pumped through the microorganism-rich slurry
   
4. The microorganisms are aerobic bacteria which breakdown dissolved organic compounds in the waste
   
5. The wastewater the enters the final sedimentation tank, where sludge settles out
   
6. Some of the sludge which is rich in bacteria, is recycle and mixed again in the aeration tank
   
7. W/w from final sedimentation is the disinfected, usually by chlorination, to kill harmful bacteria before it is released to a nearby water way.
   

The effluent can also be disinfected by UV light or ozone

Tertiary Treatment (Chemical Treatment)