WASTE WATER

MANAGEMENT AND

TREATMENT

JIJEESH V

WASTEWATER

Wastewater is a mixture

of sewage; water from

household use; water

used in commercial and

industrial applications

etc…

Wastewater contains a

variety of biological and

chemical pollutants which

make it unsafe for

humans and the

environment.

WASTEWATER TREATMENT

The objective of wastewater treatment is to remove

or modify these pollutants, so that it can be safely

discharged into the environment.

Wastewater treatment uses microbes to

decompose organic matter in sewage.

If too much untreated sewage or other organic

matter is added to a lake or stream, dissolved

oxygen levels will drop too low to support sensitive

species of fish and other aquatic life.

Wastewater treatment systems are designed to

digest much of the organic matter before the

wastewater is released so that this will not occur.

Treatment of wastewater typically involves primary,

secondary, and sometimes tertiary steps.

Secondary treatment is entirely dependent upon

the activity of microbes such as Acidovorax.

Wastewater treatment Processes

Wastewater treatment methods

Chemical

Sedimentation Gas

Transfer

FiltrationFlocculation FlotationMixingScreening

BiologicalPhysical

Aerobic Anaerobic

Precipitation Adsorption Disinfection

1. Primary treatment

Physically removes large solids using grates, screens,

and settling tanks.

Large pieces of debris are removed by screening, and

suspended particles are removed from the water

through settling processes.

2. Secondary treatment

Elimination of organic and inorganic contaminants,

through the effect of microbiological activity upon

wastewater material.

The most widely used and effective methods of

secondary treatment involve activated sludge

treatment.

3. Tertiary treatment

Removal of further nutrients and pathogens, using

methods such as filtration, passage through

wetlands, or disinfection by treatment with chlorine,

ozone or ultraviolet light.

Tertiary treatment is not always included in

wastewater treatment systems.

PRELIMINARY TREATMENT

It removes all materials that can be easily collected from

the raw sewage before they damage or clog the pumps

and sewage lines of primary treatment clarifiers.

Objects that are commonly removed during

pretreatment include trash, tree limbs, leaves, branches,

and other large objects.

The influent in sewage water passes through a bar

screen to remove all large objects like cans, rags, sticks,

plastic packets etc. carried in the sewage stream.

This is most commonly done with an automated

mechanically raked bar screen in modern plants

serving large populations, while in smaller or less

modern plants, a manually cleaned screen may be

used.

The raking action of a mechanical bar screen is

typically paced according to the accumulation on

the bar screens and/or flow rate.

The solids are collected and later disposed in a

landfill, or incinerated.

Bar screens or mesh screens of varying sizes may

be used to optimize solids removal.

If gross solids are not removed, they become

entrained in pipes and moving parts of the

treatment plant, and can cause substantial damage

and inefficiency in the process

1. PRIMARY TREATMENT( PHYSICAL OR

MECHANICAL)

Typical materials that are removed during primary

treatment include

fats, oils, and greases

sand, gravels and rocks

larger settleable solids including human waste

floating materials

Screening : to remove large objects, that could plug

lines or block tank inlets

Grit chambers : slows down the flow to allow grit to fall

out. (horizontal, aerated and vortex).

Sedimentation tank ( settling tank or clarifiers) :

Settleable solids settle out & are pumped away,

while oils float to the top & are skimmed off.

Settleable solids are then passed for aeration

in aeration tanks.

BAR SCREEN & SEDIMENTATION TANK

Sewage is held in sedimentation tanks for 2-10

hours.

Greasy material, fats, oils etc..rise to the surface,

forming scum which is skimmed off.

The organic matter which settle down is called

primary sludge.

30-40% BOD removal- treatment efficiency.

Sedimentation is enhanced by the addition of alum

at the treatment plant which produces a sticky

flocculant precipitate.

Settleable solids are then passed for aeration in

aeration tanks

AERATION TANKS

The effluents from primary

treatment are then carried to

aeration tanks.

Continuously aerated for the

growth of aerobic m.os.

Flocculation occurs.

These m.os degrade the

organic matter present in the

effluents.

2. SECONDARY TREATMENT ( BIOLOGICAL

TREATMENT)

Typically uses biological treatment processes, in

which microorganisms convert non- settleable solids to

settleable solids. Sedimentation process follows,

allowing the settleable solids to settle out.

4 methods include :-

1) Activated sludge

2) Trickling filters

3) Oxidation ponds or lagoons

4) Biological contractor system/ Rotating disc

1) ACTIVATED SLUDGE SYSTEM

. Aerobic sewage

treatment in which

flocculated biological

growth is circulated &

in contact with organic

waste in oxygen

presence is called

activated sludge

process

The activated sludge process is usually

employed following primary sedimentation.

The wastewater contains some suspended

and colloidal solids and when agitated in the

presence of air, the suspended solids form

nuclei on which biological life develop and

gradually build up to larger solids or gelatinous

masses which are known as activated sludge.

Activated sludge is a brownish floc-like substance

consisting of organic matter obtained from the

wastewater and inhabited by myriads of bacteria

and other forms of biological life.

Activated sludge with its living organisms has the

property of absorbing or adsorbing colloidal and

dissolved organic matter.

The biological organisms utilize the absorbed

material as food and convert it to inert insoluble

solids and new bacterial cells.

Much of this conversion is a step-by-step process.

Some bacteria attack the original complex substances

to produce simpler compounds as their waste products.

Other bacteria use the waste products to produce still

simpler compounds and the process continues until the

final waste products can no longer be used as food for

bacteria

The generation of activated sludge or floc in

wastewater is a slow process and the amount so

formed from any volume of wastewater during its

period of treatment is small and inadequate for the

rapid and effective treatment of the wastewater

which requires large concentrations of activated

sludge.

Such concentrations are built up by collecting the

sludge produced from each volume of wastewater

treated and re-using it in the treatment of

subsequent wastewater flows

The sludge so re-used is known as returned

sludge.

This is a cumulative process so that eventually

more sludge has been produced and is available to

maintain a viable biological population of organisms

to treat the incoming wastes.

The surplus, or excess activated sludge, is then

permanently removed from the treatment process

and conditioned for ultimate disposal.

ACTIVATED SLUDGE ORGANISM

Particles of the flock inactivated sludge consist of

mixed species of bacteria.

They embed themselves in a mass of

polysaccharide gum called zooglea.

Zooglea ramigera

Z. ramigera & related organisms need complex

nutrient requirement.

Oxidize sewage rapidly ; active in floc formation

Other m.os in zooglea are Escherichia, sps of

Pseudomonas, Alkaligens, Bacillus, Sphaerotilus,

several protozoans etc.

Different flora act in antagonism & synergism.

Bacterial population increases

Free swimming ciliates & flagellates increases

Protozoans increases

Rotifiers & nematodes increases

End result is mineralization of C,N & P

Complete mixing, rigorous aeration – efficientoxidation & reduction

Fluid part passed- final settling tank

Part of activated sludge retained – seed toreinoculate new sewage

BOD reduction – 80-95%

Most of settled sludge moved-aeration stopped-settling stops- bulging process- to anaerobicsludge digestor.

ANAEROBIC SLUDGE DIGESTORS

These can be used to further treat aerobically treated

sewage or for very highly concentrated sewage.

Vats have heating, venting, mixing, sludge seeding,

draw-off.

Protozoa and fungi are insignificant.

3 step process:

faculatively or obligately anaerobic.

organic acid and CO2.

H2, CO2, Acetate

Methanogens-

Get methane. Products are methane and CO2.

Opt temp 35-37C and pH 6-8.

Get a better reduction in volume of sludge.

2. TRICKLING FILTERS

Sewage is sprayed or drained over a rock bed or molten plastic.

Rocks large- air penetrates

Small- increased surface area for microbial activity

No filtration action

Slimy gelatinuous film of aerobes (zoogleal slime, a biofilm) grow on bed

Envelop- Exopolysacc.-gum

M.os oxidizes organic matters trickling over the surfaces

to CO2 & water.

As the biofilm layer thickens, it eventually sloughs off

into the treated effluent and subsequently forms part of

the secondary sludge.

Typically, a trickling filter is followed by a clarifier or

sedimentation tank for the separation and removal of the

sloughing

80-85 % BOD removal.

The underdrain system in trickling filters serves two

purposes:

(a) to carry the wastewater passing through the filter and

the sloughed solids from the filter to the final clarification

process, and

(b) to provide for ventilation of the filter to maintain

aerobic conditions.

3. BIOLOGICAL CONTRACTOR SYSTEM/

ROTATING DISC

A biofilm – based design.

Series of disc of several diameters are mounted on a shaft.

Disc rotates slowly ; their lower part(40%) submerged in waste water.

Aeration provided.

Rotation causes accumulated biofilm to slough off when thick

Equivalent to flocaccumulation.

4. OXIDATION PONDS OR LAGOONS

Sewage pond is deep-entirely anaerobic.

2 stages:

Sludge settles out

Effluent pumped to an adjoining pond or system of shallow ponds enough to aerated by wave action

Algal growth is encouraged ; since difficult to manage aerobic condition.

Bacterial action – decomposing organic matter &

generate CO2

Algae use CO2- photosynthesis- produce O2-inturn

encourage aerobial activity in the sewage.

Considerable amount of organic matter in the algal

form accumulates ; not a problem ; since pond is

nutrient-rich.

MICROBIAL PROCESSES IN WASTEWATER

TREATMENT

Many microbial activities are observed.

Microorganisms associated, do not persist long

(fragile).

Secondary treatment is entirely

dependent upon the activity of microbes.

Eg: Biofilters (Trickling filters) , Activated sludge etc..

Microbes frequently present in activated

sludge:

Achromobacter, Flavobacterium,

Nitrosomonas, Beggiatoa, Thiothrix, Nocardia,

Mycobacterium, Geotrichum, Nitrobacter.

Biofilters hosts :

Nematodes, insect larvae, microfungi, algae,

small worms and freshwater leech.

MICROORGANISMS

Microorganisms are present in sewage water

treatment vats well throughout the entire process.

Microorganisms encompassing: bacteria,

protozoa, and viruses, in the treatment vats, exist

and grow in the sewage water and are transferred

throughout the vats with the movement of sewage

water.

Some microorganisms are used during the

secondary treatment to remove pollutants.

However, most microorganisms will be removed

from the wastewater during the disinfection stage of

the treatment.

There are some microorganisms that continue on to

the tertiary treatment to utilize removal of other

pollutants like nitrogen, but will later be disinfected

and killed.

BACTERIA

Wastewater treatment vats are inhabited by varied

and broad strains of bacteria like Escherichia coli

, Vibrio cholerae ,Helicobacter pylori etc ..

BENEFICIAL BACTERIA

1) Biofilm forming bacteria

Are present in the trickling filter phase of the secondary treatment process, considered to be beneficial in the removal of organic materials.

Pseudomonas, Zooglea,Chromobacter, and , namelya few of whom are aerobicheterotrophic organisms.Flavobacterium Such bacteriaare exposed to oxygen duringthe treatment to break downthe organic molecules.

2.NITROGEN REMOVING BACTERIA

Nitrogen removing bacteria (nitrifiers and

denitrifiers) -

Nitrifiers include strains Nitrosomonas

europaea as well as Nitrobacter hamburgensis.

Denitrifiers include strains Thiobacillus

denitrificans.

BDELLOVIBRIO BACTERIOVORUS

Traces of Gram-negative bacteria

can also be found in the

wastewater treatment vats, such

as Bdellovibrio bacteriovorus,

which penetrate and lyses other

gram-negative bacteria within

sewage water.

obligate aerobic, parasitic

bacterium

able to replicate on the aerobic

filter film but is unable to live in

anaerobic sludge.

main function of this bacterium is

to purify waste water by reducing

gram-negative bacteria with the

ability to survive within sewage.

penetrate a host, replicate, and

finally lyses the host’s cell.

BROCADIA ANAMMOXIDANS

anaerobic

chemolithoautotrophic

bacteria and is one of several

oxidizers of ammonia.

Take in ammonia from the

sewage water, by the

release hydrazine (rocket

fuel) via an enzyme called

hydroxylamine

oxidoreductase.

clarifying wastewater of

forms of ammonia.

Nitrogen removal from wastewater is carried out

through the: oxidation of ammonia to nitrite, the

oxidation of nitrite to nitrate, and finally, the

conversion of nitrate to nitrogen gas.

There are several other bacteria, in addition to

Brocadia anammoxidans, used during nitrification

and denitrification processes.

NITROSOMONAS EUROPAEA (NITRIFIER)

a Gram-negative

chemolithoautotroph ammonia-

oxidizing bacterium

catalyzes the foremost phase in

the oxidation of toxic ammonia

to nitrite.

optimum temp 20-30 C and pH

6.0- 9.0

derives energy from burning

ammonia together with oxygen

NITROBACTER HAMBURGENSIS (NITRIFIER)

Nitrobacter hamburgensis is a

gram negative, obligate

chemolithotroph which exhibit

an aerobic lifestyle, dependent

on oxygen.

a nitrifying organism and is vital

during the process of sewage

water treatment due to the fact

that it is capable of catalyzing

the oxidation of nitrite to

nitrate, the second phase of

nitrification.

THIOBACILLUS DENITRIFICANS

Are implicated for the duration of the third phase of the nitrogen removal cycle.

This organism denitrifies nitrate to nitrogen gas, which is then released into the atmosphere.

T. denitrificans use inorganic sulfur compounds as an energy source.

Their optimal conditions vary between 30C and pH 7.5 -8.0.

SULFATE REDUCING BACTERIA

Lastly, sulfate reducing bacteria which such as Desulfotomaculum and Desulfovibrio, whom reduce sulfate to hydrogen sulfide (H2S).

These sulfate reducing microbes prefer environments with an approximate pH 7 and are inhibited below pH value of 5.5 and above 9.

Optimum temperature ranges between 28 - 32C.

PHOSPHORUS REMOVAL

Phosphorus is a nutrient which makes the growth of

algae possible.

Chemicals including: ferric chloride, alum, or lime

are added to the wastewater, which allow the

smaller particles including phosphorus to group into

larger masses.

Then are removed through the sedimentation

tanks.

PROTOZOA

Amoebae, ciliates, and flagellates are found present forsewage treatment.

Importance of protozoa in wastewater treatment is tomaintain a slime layer within trickling filter systems.

Play a predatory role in removing bacteria, otherprotozoa, and several small particles.

have multiple feeding mechanisms: filter and raptorialfeeding.

Filter feeders consume during the trickling filter phasewhen water is passed through the filter.

Raptorial feeders, such as flagellates and amoebae,feed on different types of bacteria. Larger forms ofamoebae eat ciliates and flagellates as well as smalleramoebae feed primarily on bacteria.

VIRUS

Enterovirus and rotavirus, amongst a handful of

viruses are excellent indicators of human fecal

contamination in wastewater .

These viruses must be maintained at temperatures

below 10 C and a pH 3.5- 4.

Two enteroviruses present in sewage water

treatment involve Hepatitis A and Polio myelitis.

Viruses are removed from water through ozonation,

a process of disinfection.

3. TERTIARY TREATMENT (CHEMICAL TREATMENT)

Removes disease-causing organisms from

wastewater .

3 different disinfection process are :

Chlorination

UV light radiation (a physical treatment)

Ozonation

CHLORINATION

Chlorine is used in 2 forms – Cl2 gas form or

hypochlorite tablets

Cl react with water to form HOCl, which rapidly

dissociate to form hypochlorite ion.

Cl is effective against enteric bacteria.

Most common

Advantages: low cost & effective

Disadvantages: chlorine residue could be harmful

to environment.

Dechlorination done.

OZONATION

Disinfection achieved by formation of free radicals

as oxidizing agents.

More effective against viruses & bacteria than

chlorination.

Advantages: safer than chlorination

fewer disinfection by-product

Disadvantage: high cost

low solubility of ozone in water

UV RADIATION

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

Advantages:

no chemicals are used

More rapid

water taste more natural

No by-products formed

Disadvantages: high maintenance of the UV-lamp

MEMBRANE FILTRATION

Membrane technologies disinfect treated

wastewater by physically filtering out m.os.

Does not require addition of reactive chemicals

No toxic by-products are produced.

Membrane technologies include: reverse osmosis,

ultrafiltration, microfiltration, nanofiltration.

THANK YOU……….