Nitrification and Treatment Plants

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NITRIFICATION AND TREATMENT PLANTsWastewater Treatment PlantA WWTP is the place where wastewater is treated to remove pollutants before it enters a water body or reused.

It includes physical , chemical & biological processes to remove physical , chemical and biological contaminations.

Forms Of Nitrogen In WastewaterAmmonia NH3Nitrite NO2-Nitrate NO3-Organic nitrogen

Total Kjeldal Nitogen-TKN Sum of organic nitrogen + ammonia

Total Inorganic Nitrogen-TIN Sum of Ammmonia + Nitrite + NitrateWhy is it necessary to treat the forms of nitrogen?Improve receiving stream quality

Increase chlorination efficiency

Minimize pH changes in plant

Increase suitability for reuse

Prevent ammonia toxicity

Protect groundwater from nitrate contamination

To control the growth of algae

To prevent the DO depletion

Odor problemsTo prevent imbalance of natural ecological systems and increase of eutrophication

increase risks to human health, such as NO3-N concentration in the groundwater for potable use.

Nitrification is the biological oxidation of ammonia or ammonium to nitrite followed by the oxidation of the nitrite to nitrate

NitrificationNH3-NAmmonia NNO2-NNitrite N

NO2-NNitrite NNO3-NNitrate N

NitrosomonasNitrobacterNitrification of Ammonia Occurs inTwo StepsHeterotrophic Bacteria Break Down Organics Generate NH3, CO2, and H2OAutotrophic Bacteria Utilize Inorganic Compounds (and CO2 as a Carbon Source)Assimilation Some Nitrogen Will Be Removed By The BiomassNitrogen cycleNitrogen is present in the environment in a wide variety of chemical forms includingammonium(NH4+)nitrite(NO2-)nitrate(NO3-)nitric oxide(NO) or nitrous oxide(N2O)inorganic nitrogen gas (N2)organic nitrogen

Organic nitrogen may be in the form of a living organism,humusor in the intermediate products of organic matter decomposition.

The processes of the nitrogen cycle transform nitrogen from one form to another.

Many of those processes are carried out bymicrobes, either in their effort to harvest energy or to accumulate nitrogen in a form needed for their growth.The processes of Nitrogen cycle1. Nitrogen Fixation2. Assimilation3. Ammonification4. Nitrification5. DenitrificationN-CYCLENitrogen FixationSome fixation occurs inlightning strikes, but most fixation is done by free-living orsymbioticbacteriaknown asdiazotrophs

These bacteria have thenitrogenase enzyme that combines gaseous nitrogen withhydrogen to produceammonia , which is converted by the bacteria into otherorganic compounds

Example of N-fixing bacteria includes:free-living bacteria isAzotobacterSymbiotic nitrogen-fixing bacteria such asRhizobiumusually live in the root nodules oflegumesAssimilationPlants take nitrogen from the soil by absorption through their roots in the form of eithernitrateionsornitriteions

Plants cannot assimilate ammonium ions

nitrate is absorbed, & reduced to nitrite ions and then ammonium ions for incorporation into amino acids, nucleic acids, and chlorophyll

Animals, fungi, and otherheterotrophicorganisms obtain nitrogen by ingestion ofaminoacids, nucleotidesand other small organic moleculesNitrificationNitrification is a microbial process by which reduced nitrogen compounds (primarily ammonia) are sequentially oxidized to nitrite and nitrate

The conversion of ammonia to nitrate is performed primarily by soil-living bacteria and other nitrifying bacteria

The nitrification process is primarily accomplished by two groups of autotrophic nitrifying bacteria

In the first step of nitrification, ammonia-oxidizing bacteria oxidize ammonia to nitrite according to equation

NH3 + O2 NO2 - + 3H+ + 2e-

Nitrosomonas is the most frequently identified genus associated with this step, although other genera, including Nitrosococcus, and Nitrosospira

In the second step of the process, nitrite-oxidizing bacteria oxidize nitrite to nitrate

NO2 - + H2O NO3 - + 2H+ +2e-

Nitrobacter is the most frequently identified genus associated with this second step, although other genera, including Nitrospina, Nitrococcus, and Nitrospira can also autotrophically oxidize nitrite

Elevated nitrate in groundwater is a concern for drinking water use because nitrate can interfere with blood-oxygen levels in infants and causemethemoglobinemiaor blue-baby syndrome21DenitrificationDenitrification is the reduction of nitrates back into the largely inert nitrogen gas (N2), completing the nitrogen cycle. This process is performed in anaerobic conditions

Total Kjeldahl Nitrogen(TKN) NitrificationDenitrificationNITROGEN CYCLEPHYSICO-CHEMICAL NITROGEN REMOVAL

Physico-chemical methods of nitrogen removalhave not been widely applied in waste watertreatment because

They are generally more expensive to operatethan biological treatment;

they produce a poorer effluent quality thanbiological treatment

Air stripping of AmmoniaAs the pH increases, a greater proportion ofammonia converts fromNH4to NH3

NH3+H20 NH4 + OH

Therefore, ifthe pH ofa wastewateris increasedand the liquid brought into contact with air, agradient will exist across the gas/liquid interfaceandammoniawillbe strippedto the air.

25Ion exchangeZeolites have been found effective in waste water treatment asmolecular filters which can distinguish moleculesat the ionic level.For example, the natural zeoliteclinoptilolite is selective for the ammonium ion inpreference to other ions present in solution. Afiltered waste water can be passed through a bed of zeolite to effect a 90- 97% ammonium removal

Zeolitesaremicroporous,aluminosilicatemineralscommonly used as commercialadsorbents26Breakpoint chlorinationBy adding chlorine to a wastewater, a stepwisereaction takes place which results in theconversion of ammonium to nitrogen gasBIOLOGICAL NITRIFICATIONNSecondary Treatment(Biological)WASTEWATER TREATMENTOfNitrogen

APPROACHES TO SECONDARY TREATMENTFixed Film SystemsSuspended Film SystemsLagoon Systemsorganic matter + O2 CO2 + NH3 + H2O

NH3 NO3- aquatic nutrient

FIXED FILM SYSTEMSBiofilma biological slime layerbacteria in biofilm degrade organicsbiofilm will develop on almost anything

Stir & suspend microorganisms in waste water.

They absorb organic matter &nutrients from waste water.

After hours, they settle as sludge..

Ex..activated sludge system..etcSUSPENDED FILM SYSTEMS

Consist of in-ground earthen basins in which the waste is detained for a specified time and then discharged.

They take advantage of natural aeration and microorganisms in the wastewater to remove sewage.

LAGOON SYSTEMSNitrificationCan be achieved in any Aerobic-biological process at low organic loadings Suitable environmental conditionsNitrifying bacteria are slower growing than the heterotrophic bacteriaKey requirement for nitrification to occur, therefore, is that the process should be so controlled that the net rate of accumulation of biomass is less than the growth rate of the nitrifying bacteriaPROCESSESTRICKLING FILTERS Wastewater treatment system that Biodegrades organic matter Used to achieve nitrification Consists of a fixed bed of rocks, lava, coke, polyurethane foam, ceramic, or plastic mediaAerobic conditions are maintained by splashing, diffusion, and either by forced air flowing through the bed or natural convection of air if the filter medium is porous.

TRICKLING FILTERS Not a true filtering or sieving processMaterial only provides surface on which bacteria to growCan use plastic medialighter - can get deeper beds (up to 12 m)reduced space requirementlarger surface area for growthbetter air flowless prone to plugging by accumulating slime

TRICKLING FILTERS Tank is filled with solid media Rocks Plastic Bacteria grow on surface of media Wastewater is trickled over media, at top of tank As water trickles through media, bacteria degrade BOD Bacteria eventually die, fall off of media surface Filter is open to atmosphere, air flows naturally through media Treated water leaves bottom of tank, flows into secondary clarifier Bacterial cells settle, removed from clarifier as sludge Some water is recycled to the filter, to maintain moist conditions

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TRICKLING FILTER SYSTEM40

TRICKLING FILTER PROCESS 41

BACTERIA REMOVAL 42

TRICKLING FILTER SYSTEMEfficient nitrification (ammonium oxidation)

Small land area requiredADVANTAGESRequires expert design and constructionRequires operation and maintenance by skilled personnel Requires a constant source of electricity and constant wastewater flow Flies and odours are often problematic Risk of clogging, depending on pre- and primary treatment Not all parts and materials may be locally available

DISADVANTAGESTemperature Dissolved oxygen pHPresence of inhibitorsFilter depthMedia type Loading rateWastewater BODFACTORSRotating Biological Contractor Arotating biological contactororRBCis abiologicaltreatment process used in the treatment ofwastewater followingprimary treatment. The RBC process involves allowing the wastewater to come in contact with a biological medium in order to removepollutantsin the wastewater before discharge of the treated wastewater to theenvironment. A rotating biological contactor is a type of secondary treatment process. The first RBC was installed in West Germany in 1960, later it was introduced in the United States and Canada. In the United States, rotating biological contactors ar

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