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A PROJECT REPORT ON

WATER TREATMENT SYSTEM

SUBMITTED TO


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COMPANY PROFILE The main objectives of the company are:

Water Treatment /Sewerage system / Water disposal Water Treatment /Supply/distribution Effluent Treatment Process. Equipment Air Pollution Control Devices. Environmental Impact Assessment Studies Environmental Management Plan. Environmental Audits / Statements. On Site Emergency Plan.

Packaged Effluent Treatment Plants.

Environmental EngineeringThe Rationale Mission

The Spirit to contribute towards the welfare of human being by optimum use of available natural resources and optimum use and discharge of water to maintain

equilibrium is realism at Akorn Industries Ltd. (AIL) . AIL is committed toDesign, Engineer, Deliver, review and continuously up grade innovativeEnvironmental Engineering Solutions in the fields of Effluent / Water Treatment / Disposal System, Air Pollution Control Systems, SolidManagement by exercising quality and adding values for maintainingtrustworthiness with all customers & clients. Being Honest, respectful & Co-Operative having the set of objectives as follows:

To educate people and organizations about optimum water utilization andminimum possible disposal.To provide Technology for minimizing generation.To design and deliver the most efficient treatment systems.To provide diagnostic services to assess the present technology and identifyimprovement areas.To conduct application research for improvement of existing Technologyand to create and develop better system.


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THE CORPORATE

M/s AKORN INDUSTRIES LIMITED (AIL) is an organization backed by

the vision of experienced Engineers Scientists and Management Professionalshaving expertise in the fields of Survey & Study of Water supply, Water Treatment, Environmental and Chemicals Engineering . The specialty of theorganization is turnkey projects in the field of Air, Water, Water and SolidManagement and support services being provided by a team of dedicated,efficient, highly qualified, experienced advisors with proven track records intheir respective disciplines of competence.

The company also has an added advantages of having requisite in house

facilities such as Laboratory for Water, water testing, R&D, technicalLibrary, drafting Printing, CAD & in House fabrication etc.

The above competence supplemented by prompt response and innovativeapplications makes Akorn Industries Limited a force to reckon with, whenit comes to Water supply , Treatment & Environmental EngineeringSolutions.


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GENERAL OUTLINES OF WATER TEATMENT

Water treatment , or domestic water treatment , is the process of removingcontaminants from water, both runoff (effluents ) and domestic. It includes

physical, chemical and biological processes to remove physical, chemical and biological contaminants. Its objective is to produce a stream (or treatedeffluent ) and a solid or sludge suitable for discharge or reuse back into theenvironment. This material is often inadvertently contaminated with many toxic organic and inorganic compounds.

Water is created by residences, institutions, hospitals and commercial andindustrial establishments. It can be treated close to where it is created (in septic tanks , biofilters or aerobic treatment systems ), or collected and transported via anetwork of pipes and pump stations to a municipal treatment plant (seesewerage and pipes and infrastructure ). Water collection and treatment istypically subject to local, state and federal regulations and standards. Industrialsources of water often require specialized treatment processes (see Industrial water treatment ).

The Water treatment involves three stages, called primary , secondary andtertiary treatment . First, the solids are separated from the water stream. Then

dissolved biological matter is progressively converted into a solid mass by usingindigenous, water-borne microorganisms . Finally, the biological solids areneutralized then disposed of or re-used, and the treated water may be disinfectedchemically or physically (for example by lagoons and micro-filtration). Thefinal effluent can be discharged into a stream , river , bay , lagoon or wetland , or itcan be used for the irrigation of a golf course, green way or park. If it issufficiently clean, it can also be used for groundwater recharge.

Raw influent (Water) includes household liquid from toilets , baths , showers ,kitchens , sinks , and so forth that is disposed of via sewers . In many areas, Water also includes liquid from industry and commerce. The draining of householdinto greywater and blackwater is becoming more common in the developedworld, with greywater being permitted to be used for watering plants or recycled for flushing toilets. A lot of Water also includes some surface water from roofs or hard-standing areas. Municipal water therefore includesresidential, commercial, and industrial liquid discharges, and may includestormwater runoff. Water systems capable of handling stormwater are known ascombined systems or combined sewers . Such systems are usually avoided sincethey complicate and thereby reduce the efficiency of Water treatment plantsowing to their seasonality. The variability in flow also leads to often larger thannecessary, and subsequently more expensive, treatment facilities. In addition,
http://en.wikipedia.org/wiki/Contaminantshttp://en.wikipedia.org/wiki/Runoffhttp://en.wikipedia.org/wiki/Effluentshttp://en.wikipedia.org/wiki/Effluenthttp://en.wikipedia.org/wiki/Sludgehttp://en.wikipedia.org/wiki/Toxichttp://en.wikipedia.org/wiki/Septic_tankhttp://en.wikipedia.org/wiki/Septic_tankhttp://en.wikipedia.org/wiki/Biofiltershttp://en.wikipedia.org/wiki/Aerobic_treatment_systemhttp://en.wikipedia.org/wiki/Seweragehttp://en.wikipedia.org/wiki/Sewage_collection_and_disposalhttp://en.wikipedia.org/wiki/Industrial_wastewater_treatmenthttp://en.wikipedia.org/wiki/Industrial_wastewater_treatmenthttp://en.wikipedia.org/wiki/Microorganismshttp://en.wikipedia.org/wiki/Streamhttp://en.wikipedia.org/wiki/Riverhttp://en.wikipedia.org/wiki/Bayhttp://en.wikipedia.org/wiki/Lagoonhttp://en.wikipedia.org/wiki/Wetlandhttp://en.wikipedia.org/wiki/Irrigationhttp://en.wikipedia.org/wiki/Groundwaterhttp://en.wikipedia.org/wiki/Household_wastehttp://en.wikipedia.org/wiki/Toilethttp://en.wikipedia.org/wiki/Bathinghttp://en.wikipedia.org/wiki/Showerhttp://en.wikipedia.org/wiki/Kitchenhttp://en.wikipedia.org/wiki/Sinkhttp://en.wikipedia.org/wiki/Sewerhttp://en.wikipedia.org/wiki/Greywaterhttp://en.wikipedia.org/wiki/Blackwater_(waste)http://en.wikipedia.org/wiki/Stormwaterhttp://en.wikipedia.org/wiki/Combined_sewerhttp://en.wikipedia.org/wiki/Runoffhttp://en.wikipedia.org/wiki/Effluentshttp://en.wikipedia.org/wiki/Effluenthttp://en.wikipedia.org/wiki/Sludgehttp://en.wikipedia.org/wiki/Toxichttp://en.wikipedia.org/wiki/Septic_tankhttp://en.wikipedia.org/wiki/Septic_tankhttp://en.wikipedia.org/wiki/Biofiltershttp://en.wikipedia.org/wiki/Aerobic_treatment_systemhttp://en.wikipedia.org/wiki/Seweragehttp://en.wikipedia.org/wiki/Sewage_collection_and_disposalhttp://en.wikipedia.org/wiki/Industrial_wastewater_treatmenthttp://en.wikipedia.org/wiki/Industrial_wastewater_treatmenthttp://en.wikipedia.org/wiki/Microorganismshttp://en.wikipedia.org/wiki/Streamhttp://en.wikipedia.org/wiki/Riverhttp://en.wikipedia.org/wiki/Bayhttp://en.wikipedia.org/wiki/Lagoonhttp://en.wikipedia.org/wiki/Wetlandhttp://en.wikipedia.org/wiki/Irrigationhttp://en.wikipedia.org/wiki/Groundwaterhttp://en.wikipedia.org/wiki/Household_wastehttp://en.wikipedia.org/wiki/Toilethttp://en.wikipedia.org/wiki/Bathinghttp://en.wikipedia.org/wiki/Showerhttp://en.wikipedia.org/wiki/Kitchenhttp://en.wikipedia.org/wiki/Sinkhttp://en.wikipedia.org/wiki/Sewerhttp://en.wikipedia.org/wiki/Greywaterhttp://en.wikipedia.org/wiki/Blackwater_(waste)http://en.wikipedia.org/wiki/Stormwaterhttp://en.wikipedia.org/wiki/Combined_sewerhttp://en.wikipedia.org/wiki/Contaminants


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heavy storms that contribute more flows than the treatment plant can handlemay overwhelm the Water treatment system, causing a spill or overflow (calleda combined sewer overflow, or CSO, in the United States ). It is preferable tohave a separate storm drain system for stormwater in areas that are developed

with sewer systems.

As rainfall runs over the surface of roofs and the ground, it may pick up variouscontaminants including soil particles and other sediment , heavy metals , organic compounds , animal , and oil and grease . Some jurisdictions require stormwater to receive some level of treatment before being discharged directly intowaterways. Examples of treatment processes used for stormwater includesedimentation basins, wetlands , buried concrete vaults with various kinds of filters, and vortex separators (to remove coarse solids).

The site where the raw water is processed before it is discharged back to theenvironment is called a water treatment plant (WWTP). The order and types of mechanical, chemical and biological systems that comprise the water treatment

plant are typically the same for most developed countries:

Mechanical treatment o Influx (Influent)

o

Removal of large objectso Removal of sand and grit

o Pre-precipitation

Biological treatment

o Oxidation bed (oxidizing bed) or aeration system

o Post precipitation

Chemical treatment (this step is usually combined with settling andother processes to remove solids, such as filtration. The combination isreferred to in the U.S. as physic

Primary treatment removes the materials that can be easily collected from theraw water and disposed of. The typical materials that are removed during

primary treatment include fats, oils, and greases (also referred to as FOG), sand ,gravels and rocks (also referred to as grit), larger settleable solids and floatingmaterials (such as rags and flushed feminine hygiene products). This step is

done entirely with machinery.
http://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/Storm_drainhttp://en.wikipedia.org/wiki/Soilhttp://en.wikipedia.org/wiki/Sedimenthttp://en.wikipedia.org/wiki/Heavy_metalshttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Oilhttp://en.wikipedia.org/wiki/Petroleumhttp://en.wikipedia.org/wiki/Jurisdictionhttp://en.wikipedia.org/wiki/Constructed_wetlandhttp://en.wikipedia.org/wiki/Aerationhttp://en.wikipedia.org/wiki/Sandhttp://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/Storm_drainhttp://en.wikipedia.org/wiki/Soilhttp://en.wikipedia.org/wiki/Sedimenthttp://en.wikipedia.org/wiki/Heavy_metalshttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Oilhttp://en.wikipedia.org/wiki/Petroleumhttp://en.wikipedia.org/wiki/Jurisdictionhttp://en.wikipedia.org/wiki/Constructed_wetlandhttp://en.wikipedia.org/wiki/Aerationhttp://en.wikipedia.org/wiki/Sand


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Many plants have a sedimentationstage where the Water is allowedto pass slowly through large tanks,commonly called "primary

clarifiers" or "primarysedimentation tanks". The tanksare large enough that sludge cansettle and floating material such asgrease and oils can rise to thesurface and be skimmed off. Themain purpose of the primaryclarification stage is to produce

both a generally homogeneous liquid capable of being treated biologically and a

sludge that can be separately treated or processed. Primary settling tanks areusually equipped with mechanically driven scrapers that continually drive thecollected sludge towards a hopper in the base of the tank from where it can be

pumped to further sludge treatment stages.

Secondary treatment

Secondary treatment is designed to substantially degrade the biologicalcontent of the Water such as are derived from human , food , soaps anddetergent. The majority of municipal and industrial plants treat the settled Water liquor using aerobic biological processes. For this to be effective, the biotarequires both oxygen and a substrate on which to live. There are number of ways in which this is done. In all these methods, the bacteria and protozoa consume biodegradable soluble organic contaminants (e.g. sugars , fats, organicshort-chain carbon molecules, etc.) and bind much of the less soluble fractionsinto floc . Secondary treatment systems are classified as fixed film or suspendedgrowth. Fixed-film treatment process including trickling filter and rotating

biological contactors where the biomass grows on media and the Water passesover its surface. In suspended growth systems such as activated sludgethe

biomass is well mixed with the Water and can be operated in a smaller spacethan fixed-film systems that treat the same amount of water. However, fixed-film systems are more able to cope with drastic changes in the amount of

biological material and can provide higher removal rates for organic materialand suspended solids than suspended growth systems.
http://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Protozoahttp://en.wikipedia.org/wiki/Sugarhttp://en.wikipedia.org/wiki/Flocculationhttp://en.wikipedia.org/wiki/Trickling_filterhttp://en.wikipedia.org/wiki/Rotating_biological_contactorshttp://en.wikipedia.org/wiki/Rotating_biological_contactorshttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Protozoahttp://en.wikipedia.org/wiki/Sugarhttp://en.wikipedia.org/wiki/Flocculationhttp://en.wikipedia.org/wiki/Trickling_filterhttp://en.wikipedia.org/wiki/Rotating_biological_contactorshttp://en.wikipedia.org/wiki/Rotating_biological_contactors


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Roughing filters are intended to treat particularly strong or variable organicloads, typically industrial, to allow them to then be treated by conventionalsecondary treatment processes. Characteristics include typically tall, circular filters filled with open synthetic filter media to which water is applied at a

relatively high rate. They are designed to allow high hydraulic loading and ahigh flow-through of air. On larger installations, air is forced through the mediausing blowers. The resultant water is usually within the normal range for conventional treatment processes.

Tertiary treatment

Tertiary treatment provides a final stage to raise the effluent quality before it isdischarged to the receiving environment (sea, river, lake, ground, etc.). Morethan one tertiary treatment process may be used at any treatment plant. If disinfection is practiced, it is always the final process. It is also called "effluent

polishing".

ROLE OF BACTERIA IN WATER TREATMENT:

Treatment plants should be designed to take advantage of the decompositionof organic materials by bacterial activity. This is something anyone can equateto lower costs, increased capacity, and an improved quality of effluent; evenfreedom from bad odours which may typically result when anaerobe bacteria

become dominant and in their decomposition process, produce hydrogensulphide gas and similar by-products.

Considering the fact that the total organic load of water or Water is composed of constantly changing constituent, it would be quite difficult to degrade all of these organics by the addition of one enzyme, or even several
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enzymes. Enzymes are specific catalysts and do not reproduce. What isneeded is the addition of an enzyme manufacturing system right in the Water that can be pre - determined as to its activity and performance and which has theinitial or continuing capacity to reduce .

At the present time, the addition of specifically cultured bacteria seems to be theleast expensive and most generally reliable way to accomplish desirable results.When you add the right bacteria in proper proportions to the environment, youhave established entirely new parameters of potential for the treatment situation.

WATER TREATMENT INDUSTRIES

The principal biological processes used for water treatment are divided into twomain categories:

1) Suspended growth processes2) Attached growth (or biofilm) processes.

SUSPENDED GROWTH PROCESSES

In suspended growth processes the microorganisms responsible for treatmentare maintained in liquid suspension by appropriate mixing methods. Manysuspended growth processes used in municipal and industrial water treatmentare operated with a positive dissolved oxygen concentration (aerobic), butapplications exist where suspended growth anaerobic processes are used, suchas for high organic concentration industrial water and organic sludges. The mostcommon suspended growth process used for municipal water treatment is theActivated Sludge Process.

ATTACHED GROWTH PROCESSES: In attached growth processes, themicroorganisms responsible for the conversion of organic material or nutrientsare attached on inert packing material. The organic material and nutrients areremoved from the water flowing past the attached growth also known as the

biofilm. Packing material in attached growth processes include rock, gravel,sand, slag, redwood and range of plastics and other synthetic materials.Attached growth processes are operated as aerobic or anaerobic processes. The

packing can be submerged completely in liquid or not submerged, with air or gas space above the biofilm liquid layer. The most common aerobic attachedgrowth process used is the Trickling filter.

The major methods for water treatment are listed below: Activated sludge systems
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Aerated lagoon

Aerobic granular reactor

Aerobic treatment system

Anaerobic clarigester

Anaerobic digestion

API oil-water separator

Anaerobic lagoon

Bead Filter

Belt press

Bioconversion of biomass to mixed alcohol fuels

Bioreactor

Bioretention

Biorotor

Bioroll [2]

Biolytix Carbon filtering

Cesspit

Chlorine disinfection

Combined sewer

Composting toilet

Constructed wetland

Dissolved air flotation

Distillation

Electrocoagulation

Electrodeionization

Electrolysis

Expanded granular sludge bed digestion
http://en.wikipedia.org/wiki/Aerated_lagoonhttp://en.wikipedia.org/wiki/Aerobic_granular_reactorhttp://en.wikipedia.org/wiki/Aerobic_treatment_systemhttp://en.wikipedia.org/wiki/Anaerobic_clarigesterhttp://en.wikipedia.org/wiki/Anaerobic_digestionhttp://en.wikipedia.org/wiki/API_oil-water_separatorhttp://en.wikipedia.org/wiki/Anaerobic_lagoonhttp://en.wikipedia.org/w/index.php?title=Bead_Filter&action=edit&redlink=1http://en.wikipedia.org/wiki/Belt_presshttp://en.wikipedia.org/wiki/Bioconversion_of_biomass_to_mixed_alcohol_fuelshttp://en.wikipedia.org/wiki/Bioreactorhttp://en.wikipedia.org/wiki/Bioretentionhttp://en.wikipedia.org/w/index.php?title=Biorotor&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Bioroll&action=edit&redlink=1http://en.wikipedia.org/wiki/List_of_waste_water_treatment_technologies#cite_note-1http://en.wikipedia.org/wiki/Biolytixhttp://en.wikipedia.org/wiki/Carbon_filteringhttp://en.wikipedia.org/wiki/Cesspithttp://en.wikipedia.org/w/index.php?title=Chlorine_disinfection&action=edit&redlink=1http://en.wikipedia.org/wiki/Combined_sewerhttp://en.wikipedia.org/wiki/Composting_toilethttp://en.wikipedia.org/wiki/Constructed_wetlandhttp://en.wikipedia.org/wiki/Dissolved_air_flotationhttp://en.wikipedia.org/wiki/Distillationhttp://en.wikipedia.org/wiki/Electrocoagulationhttp://en.wikipedia.org/wiki/Electrodeionizationhttp://en.wikipedia.org/wiki/Electrolysishttp://en.wikipedia.org/wiki/Expanded_granular_sludge_bed_digestionhttp://en.wikipedia.org/wiki/Aerated_lagoonhttp://en.wikipedia.org/wiki/Aerobic_granular_reactorhttp://en.wikipedia.org/wiki/Aerobic_treatment_systemhttp://en.wikipedia.org/wiki/Anaerobic_clarigesterhttp://en.wikipedia.org/wiki/Anaerobic_digestionhttp://en.wikipedia.org/wiki/API_oil-water_separatorhttp://en.wikipedia.org/wiki/Anaerobic_lagoonhttp://en.wikipedia.org/w/index.php?title=Bead_Filter&action=edit&redlink=1http://en.wikipedia.org/wiki/Belt_presshttp://en.wikipedia.org/wiki/Bioconversion_of_biomass_to_mixed_alcohol_fuelshttp://en.wikipedia.org/wiki/Bioreactorhttp://en.wikipedia.org/wiki/Bioretentionhttp://en.wikipedia.org/w/index.php?title=Biorotor&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Bioroll&action=edit&redlink=1http://en.wikipedia.org/wiki/List_of_waste_water_treatment_technologies#cite_note-1http://en.wikipedia.org/wiki/Biolytixhttp://en.wikipedia.org/wiki/Carbon_filteringhttp://en.wikipedia.org/wiki/Cesspithttp://en.wikipedia.org/w/index.php?title=Chlorine_disinfection&action=edit&redlink=1http://en.wikipedia.org/wiki/Combined_sewerhttp://en.wikipedia.org/wiki/Composting_toilethttp://en.wikipedia.org/wiki/Constructed_wetlandhttp://en.wikipedia.org/wiki/Dissolved_air_flotationhttp://en.wikipedia.org/wiki/Distillationhttp://en.wikipedia.org/wiki/Electrocoagulationhttp://en.wikipedia.org/wiki/Electrodeionizationhttp://en.wikipedia.org/wiki/Electrolysishttp://en.wikipedia.org/wiki/Expanded_granular_sludge_bed_digestion


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Facilitative lagoon

Flocculation & sedimentation

Fluidized Bed Biofilter

Flotation process

Froth flotation

Fuzzy Filter

Humanure (composting)

Imhoff tank

Iodine

Ion exchange

Living machines

Membrane Bioreactor

Nanotechnology

N-Viro

Ozone and Ultrasound Parallel plate oil-water separator

Recirculating Sand Filter

Reed bed

Retention basin

Reverse osmosis

Rotating biological contactor

Sand filter

Septic tank

Sequencing batch reactor

Water treatment

Submerged aerated filter

Treatment pond
http://en.wikipedia.org/w/index.php?title=Facilitative_lagoon&action=edit&redlink=1http://en.wikipedia.org/wiki/Flocculationhttp://en.wikipedia.org/wiki/Sedimentationhttp://en.wikipedia.org/w/index.php?title=Fluidized_Bed_Biofilter&action=edit&redlink=1http://en.wikipedia.org/wiki/Flotation_processhttp://en.wikipedia.org/wiki/Froth_flotationhttp://en.wikipedia.org/w/index.php?title=Fuzzy_Filter&action=edit&redlink=1http://en.wikipedia.org/wiki/Humanurehttp://en.wikipedia.org/wiki/Imhoff_tankhttp://en.wikipedia.org/wiki/Iodinehttp://en.wikipedia.org/wiki/Ion_exchangehttp://en.wikipedia.org/wiki/Living_machineshttp://en.wikipedia.org/w/index.php?title=Membrane_Bioreactor&action=edit&redlink=1http://en.wikipedia.org/wiki/Nanotechnologyhttp://en.wikipedia.org/w/index.php?title=N-Viro&action=edit&redlink=1http://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Ultrasoundhttp://en.wikipedia.org/wiki/API_oil-water_separatorhttp://en.wikipedia.org/w/index.php?title=Recirculating_Sand_Filter&action=edit&redlink=1http://en.wikipedia.org/wiki/Reed_bedhttp://en.wikipedia.org/wiki/Retention_basinhttp://en.wikipedia.org/wiki/Reverse_osmosishttp://en.wikipedia.org/wiki/Rotating_biological_contactorhttp://en.wikipedia.org/wiki/Sand_filterhttp://en.wikipedia.org/wiki/Septic_tankhttp://en.wikipedia.org/wiki/Sequencing_batch_reactorhttp://en.wikipedia.org/wiki/Sewage_treatmenthttp://en.wikipedia.org/w/index.php?title=Submerged_aerated_filter&action=edit&redlink=1http://en.wikipedia.org/wiki/Treatment_pondhttp://en.wikipedia.org/w/index.php?title=Facilitative_lagoon&action=edit&redlink=1http://en.wikipedia.org/wiki/Flocculationhttp://en.wikipedia.org/wiki/Sedimentationhttp://en.wikipedia.org/w/index.php?title=Fluidized_Bed_Biofilter&action=edit&redlink=1http://en.wikipedia.org/wiki/Flotation_processhttp://en.wikipedia.org/wiki/Froth_flotationhttp://en.wikipedia.org/w/index.php?title=Fuzzy_Filter&action=edit&redlink=1http://en.wikipedia.org/wiki/Humanurehttp://en.wikipedia.org/wiki/Imhoff_tankhttp://en.wikipedia.org/wiki/Iodinehttp://en.wikipedia.org/wiki/Ion_exchangehttp://en.wikipedia.org/wiki/Living_machineshttp://en.wikipedia.org/w/index.php?title=Membrane_Bioreactor&action=edit&redlink=1http://en.wikipedia.org/wiki/Nanotechnologyhttp://en.wikipedia.org/w/index.php?title=N-Viro&action=edit&redlink=1http://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Ultrasoundhttp://en.wikipedia.org/wiki/API_oil-water_separatorhttp://en.wikipedia.org/w/index.php?title=Recirculating_Sand_Filter&action=edit&redlink=1http://en.wikipedia.org/wiki/Reed_bedhttp://en.wikipedia.org/wiki/Retention_basinhttp://en.wikipedia.org/wiki/Reverse_osmosishttp://en.wikipedia.org/wiki/Rotating_biological_contactorhttp://en.wikipedia.org/wiki/Sand_filterhttp://en.wikipedia.org/wiki/Septic_tankhttp://en.wikipedia.org/wiki/Sequencing_batch_reactorhttp://en.wikipedia.org/wiki/Sewage_treatmenthttp://en.wikipedia.org/w/index.php?title=Submerged_aerated_filter&action=edit&redlink=1http://en.wikipedia.org/wiki/Treatment_pond


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Trickling filter

Ultrafiltration (industrial)

Ultraviolet disinfection

Upflow anaerobic sludge blanket digestion

Wet oxidation

CLASSIFICATION OF WER TREATMENT INDUSTRIES

The water treatment Industries can be broadly classified on the basis of mode of

operation as:1) Aerobic (in presence of oxygen)2) Anaerobic (in absence of oxygen)

THE RATIONALE FOR ANAEROBIC TREATMENT

The rationale for and interest in the use of anaerobic treatment process can beexplained by considering the advantages and disadvantages of this process. The

principal advantages and disadvantages of anaerobic treatment are listed as

follows:

Advantages:

Less energy requirement since aeration is not required.Less biological sludge production

Fewer nutrients required

Methane production, a potential energy source

Smaller reactor volume required

Elimination of off-gas air pollution

Rapid response to substrate addition after long periods without feeding.

Disadvantages:

Longer start-up time to develop necessary biomass inventory

May require alkalinity addition
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May require further treatment with an aerobic treatment process to meetdischarge requirements

Biological nitrogen and phosphorus removal is not possible

Much more sensitive to the adverse effects of lower temperatures onreaction rates.

May be more susceptible to upsets due to toxic substances

Potential for production of odors and corrosive gases.

AEROBIC TREATMENT PROCESSES

ACTIVATED SLUDGE PROCESS (ASP)

The activated sludge process is a water treatment method in which thecarbonaceous organic matter of water provides an energy source for the

production of new cells for a mixed population of microorganisms in an aquaticaerobic environment. The microbes convert carbon into cell tissue and oxidizedend products that include carbon dioxide and water. In addition, a limitednumber of microorganisms may exist in activated sludge that obtain energy byoxidizing ammonia nitrogen to nitrate nitrogen in the process known asnitrification.

Bacteria constitute the majority of microorganisms present in activated sludge.Bacteria that require organic compounds for their supply of carbon and energy(heterotrophic bacteria) predominate, whereas bacteria that use inorganiccompounds for cell growth (autotrophic bacteria) occur in proportion toconcentrations of carbon and nitrogen. Both aerobic and anaerobic bacteria mayexist in the activated sludge, but the preponderance of species are facultative,able to live in either the presence of or lack of dissolved oxygen.

Fungi, rotifers, and protozoan are also residents of activated sludge. The latter microorganisms are represented largely by ciliated species, but flagellated

protozoan and amoebae may also be present. Protozoan serve as indicators of the activated sludge condition, and ciliated species are instrumental in removingEscherichia coli from Water. Additionally, viruses of human origin may befound in raw Water influent, but a large percentage appears to be removed bythe activated-sludge process.

The success of the activated-sludge process is dependent upon establishing amixed community of microorganisms that will remove and consume organic

material, that will aggregate and adhere in a process known as bio flocculation,and that will settle in such a manner as to produce a concentrated sludge (return


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activated sludge, or RAS) for recycling. Any of several types of activated sludge solidsseparations problems indicate an

imbalance in the biologicalcomponent of this process. In theideal "healthy" system,filamentous organisms growwithin a floc (a large aggregate of

adherent, or floc-forming, microorganisms, such as bacteria) and give itstrength, with few filaments protruding out into the surrounding bulk solution.In such a system, there is no interference with the compaction and settling ratesof the activated sludge prior to its recycling.

In the figure above, following are the terms:

Q = flow rate of influent [m 3/d]

QW =

sludge flow rate [m 3/d]

Q r = Flow rate in return line from clarifier [m 3/d]

V = volume of aeration tank [m3

]

S 0 =influent soluble substrate concentration( bsCOD )

[BOD g/m 3] or [bsCODg/m 3]

S =effluent soluble substrate concentration( bsCOD )

[BOD g/m 3] or [bsCODg/m 3]

X 0 = concentration of biomass in influent [g VSS/m 3]

X R = concentration of biomass in return line fromclarifier

[g VSS/m 3]

X r = concentration of biomass in sludge drain [g VSS/m 3]

X e = concentration of biomass in effluent [g VSS/m 3]

The activated-sludge process is a biological method of water treatment that is performed by a variable and mixed community of microorganisms in an aerobicaquatic environment. These microorganisms derive energy from carbonaceousorganic matter in aerated water for the production of new cells in a process
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known as synthesis, while simultaneously releasing energy through theconversion of this organic matter into compounds that contain lower energy,such as carbon dioxide and water, in a process called respiration. As well, avariable number of microorganisms in the system obtain energy by converting

ammonia nitrogen to nitrate nitrogen in a process termed nitrification. Thisconsortium of microorganisms, the biological component of the process, isknown collectively as activated sludge.

The overall goal of the activated-sludge process is to remove substances thathave a demand for oxygen from the system. This is accomplished by themetabolic reactions (synthesis-respiration and nitrification) of themicroorganisms, the separation and settling of activated-sludge solids to createan acceptable quality of secondary water effluent, and the collection andrecycling of microorganisms back into the system or removal of excessmicroorganisms from the system.

THE PHYSICAL COMPONENTS OFTHE ACTIVATED-SLUDGE PROCESS

According to Activated Sludge, Manual of Practice #9 (Water EnvironmentAssociation, 1987), the activated-sludge process contains five essential

interrelated equipment components. The first is an aeration tank or tanks inwhich air or oxygen is introduced into the system to create an aerobicenvironment that meets the needs of the biological community and that keepsthe activated sludge properly mixed. At least seven modifications in the shapeand number of tanks exist to produce variations in the pattern of flow.

Second, an aeration source is required to ensure that adequate oxygen is fed intothe tank(s) and that the appropriate mixing takes place. This source may be

provided by pure oxygen, compressed air or mechanical aeration. Just as thereare modifications in the shape and number of aeration tanks that can be used inthe activated-sludge process, different equipment systems exist to deliver air or oxygen into aeration tanks.

Third, in the activated-sludge process, aeration tanks are followed by secondaryclarifiers. In secondary clarifiers, activated-sludge solids separate from thesurrounding waterwater by the process of flocculation (the formation of large

particle aggregates, or flocs, by the adherence of floc-forming organisms tofilamentous organisms) and gravity sedimentation, in which flocs settle towardthe bottom of the clarifier in a quiescent environment. This separation leadsideally to the formation of a secondary effluent (water having a low level of activated-sludge solids in suspension) in the upper portion of the clarifier and a


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thickened sludge comprised of flocs, termed return activated sludge, or RAS, inthe bottom portion of the clarifier.

Next, return activated sludge must be collected from the secondary clarifiers

and pumped back to the aeration tank(s) before dissolved oxygen is depleted. Inthis way, the biological community needed to metabolize influent organic or inorganic matter in the water stream is replenished.

Finally, activated sludge containing an overabundance of microorganisms must be removed, or d ( activated sludge, or WAS), from the system. This isaccomplished with the use of pumps and is done in part to control the food-to-microorganism ratio in the aeration tank(s).

THE BIOLOGICAL COMPONENTOF THE ACTIVATED-SLUDGE SYSTEM

The biological component of the activated sludge system is comprised of microorganisms. The composition of these microorganisms is 70 to 90 percentorganic matter and 10 to 30 percent organic matter. Cell makeup depends on

both the chemical composition of the water and the specific characteristics of the organisms in the biological community. Bacteria, fungi, protozoa, androtifers constitute the biological component, or biological mass, of activated

sludge. In addition, some metazoan, such as nematode worms, may be present.However, the constant agitation in the aeration tanks and sludge recirculationare deterrents to the growth of higher organisms.

The species of microorganism that dominates a system depends onenvironmental conditions, process design, the mode of plant operation, and thecharacteristics of the secondary influent water. The microorganisms that are of greatest numerical importance in activated sludge are bacteria, which occur asmicroscopic individuals from one micron in size to visible aggregations or colonies of individuals. Some bacteria are strict aerobes (they can only live inthe presence of oxygen), whereas others are anaerobes (they are active only inthe absence of oxygen). The preponderance of bacteria living in activatedsludge are facultativeable to live in either the presence or absence of oxygen,an important factor in the survival of activated sludge when dissolved oxygenconcentrations are low or perhaps approaching depletion.

While both heterotrophic and autotrophic bacteria reside in activated sludge, theformer predominate. Heterotrophic bacteria obtain energy from carbonaceousorganic matter in influent water for the synthesis of new cells. At the same time,they release energy via the conversion of organic matter into compounds suchas carbon dioxide and water. Important genera of heterotrophic bacteria include


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Achromobacter , Alcaligenes , Arthrobacter , Citromonas , Flavobacterium ,Pseudomonas , and Zoogloea .

NITRIFICATION

2 NH 4+ + 3O 2 =2NO 2- + 4H + + 2H 2O + energy

Nitrosomonas

2NO 2 + O 2 =2NO 3- + energy

Nitrobacter

Nitrification generally occurs when the time that the sludge stays in the system(called the mean cell residence time, or MCRT) is increased. A longer mean cellresidence time, therefore, allows an adequate population of nitrifying bacteria to

be built up. However, because the oxygen demand for complete nitrification ishigh, both the necessary oxygen supply and power requirements for the systemwill be increased. Moreover, optimum pH for the growth of nitrifying bacteria isin the 8 to 9 range, with pH levels below 7 causing a substantial reduction innitrification activity. In the process of converting ammonia to nitrate, mineralacidity is produced. In instances when insufficient alkalinity exists, the pH inthe system will drop, potentially inhibiting nitrification. Finally, thoughnitrification occurs over a wide range of temperatures, a reduction intemperature produces a slower rate of reaction.

CALCULATION OF THE COMMON CHARACTERISTICS OF ACOMPLETE-MIX ACTIVATED-SLUDGE SYSTEM WITH RECYCLE

Characteristics of PrimarySedimentation Effluent

water flow rate Q = 1000 m 3/dinfluent soluble substrate concentration( bsCOD ) S 0 = 192

BOD or bsCODg/m 3

nbVSS concentration in influent X 0,i = 30 g/m 3 or mg/linert inorganic Total Suspended Solids(iTSS ) iTSS = 10 g/m

3

total MLVSS concentration X T = 2500 g/m 3 or mg/lSedimentation Retention Time ( SRT ) SRT = 6 d
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Kinetic Coefficients maximum rate of soluble substrate utilization k = 12.5 g COD/gd

biomass yield Y = 0.4 g VSS/g CODusedendogenous decay coefficient k d = 0.1 g VSS/g VSSdhalf-velocity constant K s = 10 g COD/m 3

fraction of biomass that remains as cell debris f d = .15 g VSS/g VSS

biomass fraction 0.85

Characteristics of Complete-Mix SuspendedGrowth Process

effluent soluble substrate concentration ( bsCOD ) S = 0.56 g bsCOD/m

3

Hydraulic Retention Time (HRT ) = 0.197 d

daily sludge production P X,T,VSS = 82.2 kg VSS/d P X,T,TSS = 101.4 kg TSS/dfraction of biomass in the MLVSS X/X T = 0.58 kg/dobserved solids yield removed Y obs,VSS = 0.48 g VSS/g bsCOD Y obs,TSS = 0.53 g TSS/g bsCODoxygen requirement R0 = 117.4 kg/d
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Types

Two of the basic types of trickle filters are those applied to the treatment of Water and those applied to the treatment of industrial water.

Water treatment trickle filters

Onsite Water facilities (OSSF) are recognized as viable, low-cost, long-term,decentralized approaches to Water treatment if they are planned, designed,installed, operated and maintained properly (USEPA, 1997).

Water trickling filters are used in areas not serviced by municipal water treatment plants (WWTP). They are typically installed in areas where thetraditional septic tank system are failing, cannot be installed due to sitelimitations, or where improved levels of treatment are required for environmental benefits such as preventing contamination of ground water or surface water .

Sites with a high water table , high bedrock , heavy clay , small land area, or which require minimal site destruction (for example, tree removal) are ideallysuited for trickling filters.

All varieties of Water trickling filters have a low and sometimes intermittent

power consumption. They can be somewhat more expensive than traditionalseptic tank-leach field systems, however their use allows for better treatment, areduction in size of disposal area, less excavation, and higher density landdevelopment.

Configurations and components

All Water trickling filter systems share the same fundamental components :

a septic tank for fermentation and primary settling of solids a filter medium upon which beneficial microbes (biomass, biofilm ) are

promoted and developed

a container which houses the filter medium

a distribution system for applying water to be treated to the filter medium

a distribution system for disposal of the treated effluent.

By treating septic tank effluent before it is distributed into the ground, higher

treatment levels are obtained and smaller disposal means such as leach field ,shallow pressure trench or area beds are required.
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Systems can be configured for single-pass use where the treated water is appliedto the trickling filter once before being disposed of, or for multi-pass use wherea portion of the treated water is cycled back to the septic tank and re-treated viaa closed-loop . Multi-pass systems result in higher treatment quality and assist in

removing Total Nitrogen (TN) levels by promoting nitrification in the aerobicmedia bed and denitrification in the anaerobic septic tank.

Trickling filters differ primarily in the type of filter media used to house themicrobial colonies. Types of media most commonly used include plastic matrixmaterial, open-cell polyurethane foam , sphagnum peat moss , recycled tires ,clinker, gravel, sand and geotextiles. Ideal filter medium optimizes surface area for microbial attachment, water retention time, allows air flow, resists pluggingand does not degrade. Some residential systems require forced aeration unitswhich will increase maintenance and operational costs.

A typical complete trickling filter system

Industrial water treatment trickle filters

waters from a variety of industrial processes have been treated in tricklingfilters. Such industrial water trickling filters consist of two types:

Large tanks or concrete enclosures filled with plastic packing or other media.

Vertical towers filled with plastic packing or other media.
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A Typical Surface-Aerated Basing (using motor-driven floating aerators)

Ponds or basins using floating surface aerators achieve 80 to 90% removal of BOD with retention times of 1 to 10 days. The ponds or basins may range indepth from 1.5 to 5.0 metres.

In a surface-aerated system, the aerators provide two functions: they transfer air into the basins required by the biological oxidation reactions, and they providethe mixing required for dispersing the air and for contacting the reactants (thatis, oxygen, water and microbes). Typically, the floating surface aerators arerated to deliver the amount of air equivalent to 1.8 to 2.7 kg O2/kWh. However,they do not provide as good mixing as is normally achieved in activated sludgesystems and therefore aerated basins do not achieve the same performance levelas activated sludge units. Biological oxidation processes are sensitive totemperature and, between 0 C and 40 C, the rate of biological reactionsincrease with temperature. Most surface aerated vessels operate at between 4 Cand 32 C

ANAEROBIC METHODS

UPFLOW ANAEROBIC SLUDGE TREATMENT PROCESS ( UASB)

Upflow Anaerobic Sludge Blanket (UASB ) technology, normally referred toas UASB reactor, is a form of anaerobic digester that is used in the treatment of water .

The UASB reactor is a methanogenic (methane-producing) digester thatevolved from the anaerobic clarigester . A similar but variant technology toUASB is the expanded granular sludge bed (EGSB ) digester.
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UASB uses an anaerobic process whilst forming a blanket of granular sludgewhich suspends in the tank. water flows upwards through the blanket and is

processed (degraded) by the anaerobic microorganisms . The upward flowcombined with the settling action of gravity suspends the blanket with the aid of

flocculants . The blanket begins to reach maturity at around 3 months. Smallsludge granules begin to form whose surface area is covered in aggregations of bacteria. In the absence of any support matrix, the flow conditions create aselective environment in which only those microorganisms, capable of attachingto each other, survive and proliferate. Eventually the aggregates form into densecompact biofilms referred to as "granules". Biogas with a high concentration of methane is produced as a by-product, and this may be captured and used as anenergy source, to generate electricity for export and to cover its own running

power. The technology needs constant monitoring when put into use to ensure

that the sludge blanket is maintained, and not washed out (thereby losing theeffect). The heat produced as a by-product of electricity generation can bereused to heat the digestion tanks.

The blanketing of the sludge enables a dual solid and hydraulic (liquid)retention time in the digesters. Solids requiring a high degree of digestion canremain in the reactors for periods up to 90 days. Sugars dissolved in the liquidstream can be converted into gas quickly in the liquid phase which can exit thesystem in less than a day.

UASB reactors are typically suited to dilute water streams (3% TSS with particle size >0.75mm).

ANAEROBIC DIGESTION

Anaerobic digestion is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen. It is widely used to treatwater sludges and organic s because it provides volume and mass reduction of the input material. As part of an integrated management system, anaerobic

digestion reduces the emission of landfill gas into the atmosphere. Anaerobicdigestion is a renewable energy source because the process produces a methaneand carbon dioxide rich biogas suitable for energy production helping replacefossil fuels. Also, the nutrient-rich solids left after digestion can be used asfertiliser.

The digestion process begins with bacterial hydrolysis of the input materials inorder to break down insoluble organic polymers such as carbohydrates andmake them available for other bacteria. Acidogenic bacteria then convert thesugars and amino acids into carbon dioxide, hydrogen, ammonia, and organicacids. Acetogenic bacteria then convert these resulting organic acids into aceticacid, along with additional ammonia, hydrogen, and carbon dioxide.
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Methanogenic bacteria finally are able to convert these products to methane andcarbon dioxide.

The technical expertise required to maintain anaerobic digesters coupled with

high capital costs and lower process efficiencies have so far limited the level of its industrial application as a treatment technology.

Careful control of the digestion temperature, pH, and loading rates is crucial toobtaining efficient breakdown of the material, and disturbances to a digest canlead to process failure. Ensuring that the quality of input materials to thedigesters is maintained and that the process effectively monitored is essentialfor ensuring that a digester's performance is reliable.

Applications

Anaerobic digestion is particularly suited to wet organic material and iscommonly used for effluent and Water treatment. Anaerobic digestion is asimple process that can greatly reduce the amount of organic matter whichmight otherwise be destined to be landfilled or burnt in an incinerator.

Almost any organic material can be processed with anaerobic digestion. Thisincludes biodegradable materials such as paper, grass clippings, leftover food,Water and animal . The exception to this is woody s that are largely unaffected

by digestion as anaerobes are unable to degrade lignin. Anaerobic digesters canalso be fed with specially grown energy crops such as silage for dedicated biogas production. In Germany and continental Europe these facilities arereferred to as biogas plants. A co-digestion or co-fermentation plant is typicallyan agricultural anaerobic digester that accepts two or more input materials for simultaneous digestion.

In developing countries simple home and farm-based anaerobic digestionsystems offer the potential for cheap, low-cost energy for cooking and lighting.Anaerobic digestion facilities have been recognised by the United NationsDevelopment Programme as one of the most useful decentralised sources of energy supply.

Pressure from environmentally-related legislation on solid disposal methods indeveloped countries has increased the application of anaerobic digestion as a

process for reducing volumes and generating useful by-products. Anaerobicdigestion may either be used to process the source separated fraction of municipal , or alternatively combined with mechanical sorting systems, to

process residual mixed municipal . These facilities are called mechanical

biological treatment plants


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Utilising anaerobic digestion Industries can help to reduce the emission of greenhouse gases in a number of key ways:

Replacement of fossil fuels

Reducing methane emission from landfills Displacing industrially-produced chemical fertilisers

Reducing vehicle movements

Reducing electrical grid transportation losses

Methane and power produced in anaerobic digestion facilities can be utilised toreplace energy derived from fossil fuels, and hence reduce emissions of

greenhouse gases .This is due to the fact that the carbon in biodegradablematerial is part of a carbon cycle. The carbon released into the atmosphere fromthe combustion of biogas has been removed by plants in order for them to growin the recent past. This can have occurred within the last decade, but moretypically within the last growing season. If the plants are re-grown, taking thecarbon out of the atmosphere once more, the system will be carbon neutral.Thiscontrasts to carbon in fossil fuels that has been sequestered in the earth for manymillions of years, the combustion of which increases the overall levels of carbondioxide in the atmosphere.

Digestate liquor can be used as a fertiliser supplying vital nutrients to soils. Thesolid, fibrous component of digestate can be used as a soil conditioner. Theliquor can be used as a substitute for chemical fertilisers which require largeamounts of energy to produce. The use of manufactured fertilisers is thereforemore carbon intensive than the use of anaerobic digestate fertiliser. This soliddigestate can be used to boost the organic content of soils.

The process

There are a number of bacteria that are involved in the process of anaerobicdigestion including acetic acid-forming bacteria (acetogens) and methane-forming bacteria (methanogens). These bacteria feed upon the initial feedstock,which undergoes a number of different processes converting it to intermediatemolecules including sugars, hydrogen & acetic acid before finally beingconverted to biogas.

Different species of bacteria are able to survive at different temperature ranges.Ones living optimally at temperatures between 35-40C are called mesophiles

or mesophilic bacteria. Some of the bacteria can survive at the hotter and morehostile conditions of 55-60C, these are called thermophiles or thermophilic bacteria. Methanogens come from the primitive group of archaea. This family


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includes species that can grow in the hostile conditions of hydrothermal vents.These species are more resistant to heat and can therefore operate atthermophilic temperatures, a property that is unique to bacterial families.

As with aerobic systems the bacteria in anaerobic systems the growing andreproducing microorganisms within them require a source of elemental oxygento survive.

In an anaerobic system there is an absence of gaseous oxygen. In an anaerobicdigester, gaseous oxygen is prevented from entering the system through

physical containment in sealed tanks. Anaerobes access oxygen from sourcesother than the surrounding air. The oxygen source for these microorganisms can

be the organic material itself or alternatively may be supplied by inorganicoxides from within the input material. When the oxygen source in an anaerobicsystem is derived from the organic material itself, then the 'intermediate' end

products are primarily alcohols, aldehydes, and organic acids plus carbondioxide. In the presence of specialised methanogens, the intermediates areconverted to the 'final' end products of methane, carbon dioxide with tracelevels of hydrogen sulfide. In an anaerobic system the majority of the chemicalenergy contained within the starting material is released by methanogenic

bacteria as methane.

Populations of anaerobic bacteria typically take a significant period of time to

establish themselves to be fully effective. It is therefore common practice tointroduce anaerobic microorganisms from materials with existing populations.This process is called 'seeding' the digesters and typically takes place with theaddition of Water sludge or cattle slurry.

Stages

The key process stages of anaerobic digestion

There are four key biological and chemical stages of anaerobic digestion:

1. Hydrolysis2. Acidogenesis

3. Acetogenesis

4. Methanogenesis

In most cases biomass is made up of large organic polymers. In order for the bacteria in anaerobic digesters to access the energy potential of the material,these chains must first be broken down into their smaller constituent parts.These constituent parts or monomers such as sugars are readily available by


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other bacteria. The process of breaking these chains and dissolving the smaller molecules into solution is called hydrolysis. Therefore hydrolysis of these highmolecular weight polymeric components is the necessary first step in anaerobicdigestion. Through hydrolysis the complex organic molecules are broken down

into simple sugars, amino acids, and fatty acids.

Acetate and hydrogen produced in the first stages can be used directly bymethanogens. Other molecules such as volatile fatty acids (VFAs) with a chainlength that is greater than acetate must first be catabolised into compounds thatcan be directly utilized by methanogens. The biological process of acidogenesisis where there is further breakdown of the remaining components by acidogenic(fermentative) bacteria. Here VFAs are created along with ammonia, carbondioxide and hydrogen sulfide as well as other by-products. The process of acidogenesis is similar to the way that milk sours. The third stage anaerobicdigestion is acetogenesis. Here simple molecules created through theacidogenesis phase are further digested by acetogens to produce largely aceticacid as well as carbon dioxide and hydrogen. The terminal stage of anaerobicdigestion is the biological process of methanogenesis. Here methanogens utilisethe intermediate products of the preceding stages and convert them intomethane, carbon dioxide and water. It is these components that makes up themajority of the biogas emitted from the system. Methanogenesis is sensitive to

both high and low pH and occurs between pH 6.5 and pH 8. The remaining,non-digestable material which the microbes cannot feed upon, along with any

dead bacterial remains constitutes the digestate. Anaerobic digesters can bedesigned and engineered to operate using a number of different processconfigurations:

1. Batch or continuous

2. Temperature: Mesophilic or thermophilic

3. Solids content: High solids or low solids

4. Complexity: Single stage or multistage


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Batch or continuous

A batch system is the simplest form of digestion. Biomass is added to thereactor at the start of the process in a batch and is sealed for the duration of the

process. Batch reactors suffer from odour issues that can be a severe problemwhen they are emptied. Typically biogas production will be formed with anormal distribution pattern over time. The operator can use this fact todetermine when they believe the process of digestion of the organic matter hascompleted. As the batch digestion is simple and requires less equipment andlower levels of design work it is typically a cheaper form of digestion.

In continuous digestion processes organic matter is constantly or added instages to the reactor. Here the end products are constantly or periodicallyremoved, resulting in constant production of biogas. Examples of this form of

anaerobic digestion include, continuous stirred-tank reactors (CSTRs), Up flowanaerobic sludge blanket (UASB), Expanded granular sludge bed (EGSB) andInternal circulation reactors (ICR).

Temperature

There are two conventional operational temperature levels for anaerobic

digesters, which are determined by the species of methanogens in the digesters: Mesophilic which takes place optimally around 37-41C or at ambient

temperatures between 20-45C where mesophiles are the primarymicroorganism present

Thermophilic which takes place optimally around 50-52 at elevatedtemperatures up to 70C where thermophiles are the primarymicroorganisms present

There are a greater number of species of mesophiles than thermophiles. These bacteria are also more tolerant to changes environmental conditions thanthermophiles. Mesophilic systems are therefore considered to be more stablethan thermophilic digestion systems.

A drawback of operating at thermophilic temperatures is that more heat energyinput is required to achieve the correct operational temperatures. This increasein energy is not be outweighed by the increase in the outputs of biogas from the

systems. It is therefore important to consider an energy balance for thesesystems.


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Solids

Typically there are two different operational parameters associated with thesolids content of the feedstock to the digesters:

High-solids Low-solids

Digesters can either be designed to operate in high solid content, with a totalsuspended solids TSS) concentration greater than ~20%, or a low solidsconcentration less than ~15%.[55] High-solids digesters process thick slurrythat requires more energy input to move and process the feedstock. Thethickness of the material may also lead to associated problems with abrasion.High-solids digesters will typically have a lower land requirement due to thelower volumes associated with the moisture.

Low-solids digesters can transport material through the system using standard pumps that require significantly lower energy input. Low-solids digestersrequire a larger amount of land than high-solids due to the increase volumesassociated with the increased liquid: feedstock ratio of the digesters. There are

benefits associated with operation in a liquid environment as it enables morethorough circulation of materials and contact between the bacteria and their food. This enables the bacteria to more readily access the substances they are

feeding off and increases the speed of gas yields.Digestion systems can be configured with different levels of complexity:

One-stage or single-stage

Two-stage or multistage

A single-stage digestion system is one in which all of the biological reactionsoccur within a single sealed reactor or holding tank. Utilising a single stagereduces construction costs, however facilitates less control of the reactionsoccurring within the system. Acidogenic bacteria, through the production of acids, reduce the pH of the tank. Methanogenic bacteria, as outlined earlier,operate in a strictly defined pH range. Therefore the biological reactions of thedifferent species in a single stage reactor can be in direct competition with eachother. Another one-stage reaction system is an anaerobic lagoon. These lagoonsare pond-like earthen basins used for the treatment and long-term storage of manures. Here the anaerobic reactions are contained within the naturalanaerobic sludge contained in the pool.

In a two-stage or multi-stage digestion system different digestion vessels areoptimised to bring maximum control over the bacterial communities livingwithin the digesters. Acidogenic bacteria produce organic acids and more


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quickly grow and reproduce than methanogenic bacteria. Methanogenic bacteriarequire stable pH and temperature in order to optimise their performance.

Typically hydrolysis, acetogenesis and acidogenesis occur within the firstreaction vessel. The organic material is then heated to the required operationaltemperature (either mesophilic or thermophilic) prior to being pumped into amethanogenic reactor. The initial hydrolysis or acidogenesis tanks prior to themethanogenic reactor can provide a buffer to the rate at which feedstock isadded. Some European countries require a degree of elevated heat treatment inorder to kill harmful bacteria in the input . In this instance their may be a

pasteurisation or sterilisation stage prior to digestion or between the twodigestion tanks. It should be noted that it is not possible to completely isolatethe different reaction phases and often there is some biogas that is produced inthe hydrolysis or acidogenesis tanks.

Residence

The residence time in a digester varies with the amount and type of feedmaterial, the configuration of the digestion system and whether it be one-stageor two-stage.

In the case of single-stage thermophilic digestion residence times may be in theregion of 14 days, which comparatively to mesophilic digestion is relativelyfast. The plug-flow nature of some of these systems will mean that the fulldegradation of the material may not have been realised in this timescale. In thisevent digestive exiting the system will be darker in colour and will typicallyhave more odour.

In two-stage mesophilic digestion, residence time may vary between 15 and 40days. In the case of mesophilic UASB digestion hydraulic residence times can

be (1hour-1day) and solid retention times can be up to 90 days. In this manner the UASB system is able to separate solid in hydraulic retention times with theutilisation of a sludge blanket.

Continuous digesters have mechanical or hydraulic devices, depending on thelevel of solids in the material, to mix the contents enabling the bacteria and thefood to be in contact. They also allow excess material to be continuouslyextracted to maintain a reasonably constant volume within the digestion tanks.

Products


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There are three principal products of anaerobic digestion: biogas, digestate andwater. Biogas is the ultimate product of the bacteria feeding off the input

biodegradable feedstock, and is mostly methane and carbon dioxide, with asmall amount hydrogen and trace hydrogen sulphide. Most of the biogas is

produced during the middle of the digestion, after the bacterial population hasgrown, and tapers off as the putrescible material is exhausted. The gas isnormally stored on top of the digester in an inflatable gas bubble or extractedand stored next to the facility in a gas holder.

Biogas may require treatment or 'scrubbing' to refine it for use as a fuel.Hydrogen sulphide is a toxic product formed from sulphates in the feedstock and is released as a trace component of the biogas.

Volatile siloxanes can also contaminate the biogas; such compounds are

frequently found in household and water. In digestion facilities accepting thesematerials as a component of the feedstock, low molecular weight siloxanesvolatilise into biogas.

Digestive

Digestive is the solid remnants of the original input material to the digesters that

the microbes cannot use. It also consists of the mineralised remains of the dead bacteria from within the digesters. Digestive can come in three forms; fibrous,liquor or a sludge-based combination of the two fractions. In two-stage systemsthe different forms of digestive come from different digestion tanks. In singlestage digestion systems the two fractions will be combined and if desiredseparated by further processing.

water

The final output from anaerobic digestion systems is water. This water originates both from the moisture content of the original that was treated butalso includes water produced during the microbial reactions in the digestionsystems. This water may be released from the dewatering of the digestate or may be implicitly separate from the digestate.

The water exiting the anaerobic digestion facility will typically have elevatedlevels of biochemical oxygen demand (BOD) and chemical oxygen demand(COD), these are measures of the reactivity of the effluent and show an abilityto pollute. Some of this material is termed 'hard COD' meaning it cannot beaccessed by the anaerobic bacteria for conversion into biogas. If this effluentwas put directly into watercourses it would negatively affect them by causingeutrophication. As such further treatment of the water is often required. This


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treatment will typically be an oxidation stage where air is passed through thewater in a sequencing batch reactors or reverse osmosis unit.

ANAEROBIC LAGOONS

Anaerobic lagoons are used to dispose of animal , particularly that of cows and pigs. The is washed into the lagoon by flushing the animal pens with water.Solid , particularly the fibrous type of cows, is sometimes separated before thewater enters the lagoon to prevent the build up of solid material. Anaerobicorganisms naturally present in the manure and the environment decompose thein the anaerobic conditions of the lagoon.

Areas with cold winters are inappropriate for anaerobic lagoons because the

activity of the microorganisms is highly dependent on temperature. It is criticalto have the proper size for the lagoon, with volume being more important thansurface area. A minimum of two meters is necessary for anaerobic conditions,

but the depth should not exceed 6 meters. Sometimes a secondary lagoon isused to accept s while the primary lagoon is undergoing maintenance or for other purposes.

If the anaerobic lagoon system is being used for energy production, the primarylagoon has a cover floating on the surface of the water. The cover captures the

biogas produced by anaerobic bacteria. The biogas produced by anaerobiclagoons is 50 to 75% methane, with carbon dioxide making up most of the rest.The gas is usually used to produce electricity using a microturbine or reciprocating engine, but it can also be used for water or space heating. The gasusually undergoes pretreatment, particularly dehydration, prior to combustion.Sometimes the carbon dioxide, which is incombustible, is also removed.

PLANTS VISITED

0.35 MLD MBBR ( MOVING BED BIO REACTOR) , JANAKPURIWEST

The purpose of MBBR system is to increase the amount of biomass in a biological treatment reactor by providing a media upon which it can grow. Thusthe media of an MBBR system is central to its operation. It must perform therequired task of acting as a carrier or residence for the biomass while alsogiving a long service life.

The MBBR process employs a submerged ring media onto which microorganisms attach. The biomass retained on the ring media provides effective


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treatment for the effluent. The ring media are kept in motion by coarse bubbleaeration. The air introduced into the tank is sufficient to ensure thorough mixingand turnover of the media within the reactor. The media can be used in aerobic,anoxic, and anaerobic zones. The MBBR does not incorporate return sludge.

ADVANTAGES OF MBBR PROCESS: High effluent quality. Small footprint. Simplicity of design, installation and operation. Site specific designs for small to large populations. Retrofits activate sludge plants to improve capacity and effluent quality. Easily retained media. Low capital and operating costs. Robust package treatment plant for small communities.

40 MGD WATER TREATMENT PLANT, DELHI JAL BOARD,NILOTHI

SL. NO.

UNIT QUANTITY FUNCTION

1 Bar screen unit 4 It consists of conveyor belt. It isused for the removal of large


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floating solids.

2 Grit chamber unit. 4 There are four grit chambers inthe plant which consists of a

bridge. The bridge is dividedinto three parts: Gear Box,Shaft, and rubber equipment.Grit chamber mashes thick

particles. Rake classifier is also present here which takes up the particles which are not mashedup by grit chamber (like pieces

of stones).

3 Manual bar screen unit 4 It also removes floating solids.It is operated manually.

4 Primary sedimentationchamber unit

1 It removes primary settablesolids. From here water goes tothe aeration tank. In this step

settable are removed bygravitational settling under quiescent conditions. Thesludge formed at the bottom of the tank is removed asunderflow and the cleared liquid

produced is known as overflow.There are generally three types

of settling: Settling of dilutesuspensions of discrete

particles, settling of dilutesuspensions of flocculent

particles and zone settlingwhich includes hindered settlingand compressive settling.

Raw pump house is presentwhere raw sludge comes by


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gravity and water moves in theupward direction. There is alsoa pump which is called as returnsludge pump for return sludge.

5 Aeration chamber 14 aerators 14 aerators are installed for providing adequate amount of oxygen. Aeration depends uponthe amount of upcoming water.All the aerators are not operatedat the same time. It depends onthe amount of water supply. The

main function of this unit is tocontrol MLSS (Mixed Liquor Suspended Solids) by mixingoxygen through aeration. Therate at which dissolved oxygenis used , depends on:

a. Quantity of organics.

b. The ease with which they are bio- degraded.

c. Dilution capacity of thestream.

6 Secondary SedmentationTank

1 From the aeration tank theWater flows to the finalsedimentation tank since there

are no floating solids, provisions for the removal of the scum or floatage are notneeded. The suspended particlesin the aeration tank are light inweight and are thus markedlyinfluenced by currents.Therefore in these secondary

settling tanks a considerablelength of overflow weir is


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desirable to reduce the velocityof approach.

7 Sludge digestion tank 6 It consists of circular tank with

hoppered water and having afixed or floating type of roof over its top. The raw sludge is

pumped from raw sludge pumphouse into the tank and whenthe tank is put into the operationit is seeded with digested sludgefrom another tank. A screw

pump with an arrangement for circulating sludge from bottomto top of the tank or vice-versais commonly used, for stirringthe sludge.

The gases of decomposition(mainly CH4 and CO2) arecollected in Gas dome or in gasholders for subsequent use. Thedigested sludge which settlesdown to bottom of the Tank isremoved under hydrostatic

pressure periodically once or twice a week. The supernatantliquor being higher in BOD andsuspended solids content is sent

back for the treatment alongwith raw Water in the treatment

plant.

The digestion tanks arecylindrical shaped tanks withdia ranging between 3 to 12 m.the bottom hoppered floor of the

tank is given a slope of about1:1 or 1:3 (1H:3V) the depth of


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the digestion tank is usuallykept at about 6m. the capacityof the digestion tank is afunction of sludge production,digestion period, degree of digestion required, loss of moisture and conversion of organic matter. If the progressof the sludge digestion isassumed to be linear then thecapacity of digestion tank isgiven as:

V=[(V1+V2)/2]*T

Where V= volume of digestionin m3

V1= raw sludge added per day(m3 per day)

V2=equivalent digested sludge produced per day on completionof digestion(m3 per day)=V1/3

T= digestion period (days).

From the digester the sludge istaken as fertilizer and manure.Blowers are used for mixingand not for aeration in digester.

BULKING AND FOAMING SLUDGE IN AN ASP PLANT

Foam formation and poorly settling sludge are two most common problems of

ASP process. A sludge that exhibits poor settling characteristics is called as bulking sludge. Filamentous micro-organisms (fungi) are found to be


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responsible for bulked sludge. To control these organisms chlorination andreduction of sludge age to less than 6 days is done.

POWER SUPPLY IN NILOTHI PLANT

Dual fuel engine is used for power supply in which diesel and gas are used inthe ratio 20:80. There are three generators of 600 KVA which generates about1200KVa electricity. There are also many step-down and step-up transformersfor the electricity supply and control. To cool the air water coolers are present.

water treatment ok 1

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