BY: Sheama Farheen Savanur

WASTE WATER TREATMENT

Introduction Definition and classes Characteristics Hazards Treatment

Single dwelling unit Municipal treatment process

Definition:

Sewage is the waste water of community. It also consists of: Domestic water borne wastes: human

excrement, wash waters. Industrial water borne wastes: acids, oils,

greases. Ground, surface and atmospheric waters

that enter the sewage system.

There are two classes of sewage 1) Domestic sewage: Human wastes,

laundry, food preparation etc., Grey, turbid liquid with earthy odour 2) Industrial sewage: organic and

inorganic compounds. type of product produced and

nature of process involved.

Reduce the spread of pathogenic micro organisms.

Prevent the pollution of ground and surface water.

Maintain the oxygen balance. Avoid health and aesthetic hazards. Prevent development of objectionable

conditions. Prevent damage to concrete structures.

Due to Biological agents: contamination of food and water,

vector mediated disease.

Due to chemicals present in wastes: solids, liquids or gases which are

relatively toxic or non toxic can pose a serious danger to life

Waste water is carried through pipes known as sewers from its place of production to place of treatment and disposal.

Types of sewers• Sanitary sewers: domestic and industrial

sewage.• Storm sewers: dumping storm and surface

waters.• Combined sewers: carry all the sewage

• Adequate treatment is necessary to prevent contamination of receiving waters. • Wastewater treatment consists of applying known technology to improve or upgrade the quality of a wastewater.

Factors :•Quality and nature•Cost of the plant•Sanitary requirements•circumstances

Wastewater treatment is categorized by the nature of the treatment process being used as physical, chemical and biological.

Physical process involve Degasification  and Equalization  

Chemical process involve chlorination, ozonation, neutralization, coagulation, adsorption and ion exchange.

Biological methods are activated sludge process, trickling filter and oxidation ponds.

1. Single dwelling units It is a method of treatment of sewage

of individual or unit structures. EX: septic tank

They are small rectangular chambers sited below ground level.

It is designed to retain the solids of the sewage entering the tank.

Sedimentation and the biological degradation is involved.

Anaerobic digestion of sewage by the micro organisms.

1. Primary treatment: to remove coarse solid particles.

2. Secondary treatment: oxidation of organic compounds

3. Advanced treatment: removes objectionable substances .

4. Final treatment: disinfection and disposing.

5. Sludge processing: stabilize the sludge.

Sedimentation : most of the settle able solids are separated

or removed from the wastewater by the physical process of sedimentation

physical phenomena relating to the settling of solids by gravity are allowed to operate. 

To remove larger entrained objects . Concentration and collection of particulate

matter referred to as sludge.

• Secondary treatment depends primarily upon aerobic organisms which biochemically decompose the organic solids to inorganic or stable organic solids

• The devices used in secondary treatment may be divided into four groups: 

Trickling filters with secondary settling tanks

Activated sludge and modifications with final settling tanks

Intermittent sand filters Stabilization ponds

• It consists of a bed of coarse pieces of stone ,gravel and slag.

• The depth is 1 to 3 inches. The tank is equipped with drains underneath.

• The surface of the filter is applied with mixed population of micro organisms.

• Passage of wastewater through the filter causes the development of a gelatinous coating of bacteria, protozoa and other organisms on the media.

In the absence of oxygen, anaerobic decomposition becomes active near the surface of the media.  ◦ Settled waste+o2=oxidized fluid+ new cells

The new cells exert high BOD and must be removed before effluent is discharged tp a natural water body.

For greater efficiency biofilters recirculation of sewage, plastic media etc., are employed.

Activated sludge process•It is based on vigorous aeration of sewage resulting in formation of floccules. •The floc particles i.e activated sludge contain large number of microbes .•These carry out oxidation of organic matter and thus BOD is reduced.•Due to the growth of filamentous micro organisms flocs settle poorely and effects performance of sewage treatment.

Activated sludge plant

Advantages :Requires a small land areaHas a low BOD & therefore doesn’t require dilution.Reduction of suspended solids.

Disadvantages:Detergents possess a major problem.Foam formation takes place

They are also known as oxidative ponds or stabilizing ponds

It is most important method of sewage treatment in hot climates where sufficient land is normally available

The sewage effluent are been dumped into large pond of depth 2- 4feet

It is natural process of sewage purification because oxidation of matters occur through symbiotic action of algae and aerobic bacteria

Aerated lagoon Treatment plant

• The putrecible matter is stabilized and thus BOD is reduced.

• 6CO2+12H2O=C6H12O6+6H20+6O2.ADVANTAGES:1.Any degree of purification at lowest cost.2.Removal of pathogens is greater.3.Wide variety of industrial waste.4.The algae produced are potential source of

high protein food.5.They can be easily designed.

DISADVANTAGES Large land space. Inefficient for removing fecal bacteria Algae may die, & if not removed may

become organic matter of sewage effluent.

• The solids accumulated during sedimentation are pumped into separate tank for digestion of sludge under controlled condition.

• The microbial action on sludge is known as sludge digestion.

• Anaerobic and facultative bacteria degrade the solids to methane and co2 and traces of nitrogen and hydrogen.

• This gas mixture is used as fuel for heating and for operating power

Sludge digestion Energy consumption

Composting:• It is a process where dewatered sludge

undergoes decomposition within thermophilic temperature range.

• The dewatered sludge is mixed with a bulking agent such as wood chips and kept in aerated piles.

• The mixture is allowed to cure for a period of time(21 days)

• It is finally transformed to humus type material and used soil conditioner.

Thank you