water letter general chemistry
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CHAPTER –1
1, Water an universal Solvent available and easy to handle hence been used by various Industries for Process & Other Applications. 2, Source of Water shall be called as Surface Water & Under Ground Water. 3, Basic Chemical Character of the Water shall be Determined as follows, Minerals, Gases, Suspended Solids (Turbidity) Contributed to water an process through Decaying Vegetation’s, Gases producing Acid while passing through the Under ground sand bed and various types of Mineral Rocks thus diluting the particles been dissolved and remains in form of soluble in water known as TDS (Total Dissolved Solids).
HIGH TDS ‐‐‐‐‐‐‐‐‐‐ UNDER GROUND OR BORE WELL WATER LOW TDS BUT HIGH SUSPENDED SOLIDS IN SURFACE WATER The reason being for high tds in Bore well water purely depends upon the Landscape and Environment. Similarly Surface Water like River, Storm, Pond due to the flow Inconsistent while at High flow leaching and eroding the way it pass through thus contributing to Turbidity (or) Total Suspended Solids. However due to the lesser Acid Leaching occurs does not contributing Dissolved Solids. Generally Industry located near by River or Any Available Surface Water as a Source will adopt Raw Water Clarification ( Chemical Treatment ) consisting of Clarifiers And Filtration System prior to their Process Consumption. Like the same Industry, Which use Under Ground Water, as a Source will carry out Treatment like Softening, De Mineralisation, and Reverse Osmosis prior to their Process Consumption. TDS TDS means Mineral Available in the water in Soluble form and will include of the following Parameters
Conductivity PH Total Alkalinity Total Hardness ( Calcium & Magnesium ) Hydrogen Carbondioxide Oxides Chlorides Sulphates Sulphites Silica Iron as fe
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Nitrite Nitrate Sulphide Flouride Other Organic Matters
Definition Of The Treatment is As Follows 1, Raw Water Treatment Reduction of TSS. 2, Demineralisation Reduction of TDS. 3, Ion Exchange Softening Reduction of Total Hardness . 4, Reverse Osmosis Again reduction of TDS. PROBLEM OCCURS WHILE USING WATER 1, Mineral Deposition ( Scaling ). 2, Corrosion. 3, Microbial Growth. MINERAL DEPOSITION ( SCALING ) Mineral Deposits ( Scaling ) is an uniform layer and get baked off due to the system heat load and saturated minerals reacts and tend to deposit at the place where heat transfer take places. Normally scaling is an great issue at Steam Boiler & Cooling tower Applications.
Types Of Scaling 1, Calcium Carbonate 2, Magnesium Carbonate 3, Magnesium Silicate 4, Calcium Silicate 5, Calcium Sulphate 6, iron Oxide 7, Iron Phosphate 8, Calcium Phosphate 9, Magnesium Phosphate But major element for scaling occurs due to Calcium & Magnesium reacting with basic Carbonates and precipitates as Calcium & Magnesium Carbonates. SCALING PROCESS ♦ SATURATION ♦ NEUCLIATION ♦ CRYSTALISATION ♦ UNIFORM DEPOSITION
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Once the uniform deposition occurs and gets baked off and hard by nature means Scale. Any Scale Analysis will comprise of Chloride and Sulphate and other Minerals too the reason being is called Co Precipitation But Prime Scaling occurs is due to Calcium & Magnesium only. Iron Oxide deposits normally occurs due to Corroded Ferric Oxide Particles remaining in Water inSoluble Form as TSS . Phosphate Scales due to the Chemical Treatment where Excessive phosphate been Maintained as Product residual will Broke at high pH and reacts with Calcium & Magnesium, Iron which has already Saturated and deposits uniformly. As it been mentioned earlier Calcium & Magnesium is the major deposits since the Solubility of this is low at high pH and at high Temperature, Wherelse more soluble at Acidic pH and at low Temperature. Silica has Inverse Solubility against Total Hardness Means Low solubility at Low pH & Temperature and High Soluble at High pH And at High Temperature. Normally Calcium Silicate scale may not form since calcium Silicate is more Soluble than Magnesium Silicate hence more deposition will be Magnesium Silicate which is very hard by nature, Cement coloured and carry’s Ring mark within it is the Indication. Common Water‐related Problems in Process Plants : Reasons & Impact 1.) Scaling :‐
Reason:‐ i. Scaling / deposition is precipitation of various salts on water‐bearing
surfaces in Condensers, Tower fills etc. These deposits precipitate out due to reduced solubility of these salts in the water at higher concentrations and temperatures.
ii. Softening treatment of the make‐up water tends to reduce the severity of
the scaling / deposition to some extent. But even then the problem remains. Further, the severity of silica scaling is not at all reduced by softening, as Silica is not reduced during softening operations. Also, once formed, Silica scales cann’t be descaled easily.
Impact:‐ When Scaling / deposition takes place, the impact upon the process heat exchangers would vary from plant to plant and would depend upon the process requirements and constraints. However, in case the scaling/ deposition takes place in condensers, heat exchangers etc. the following impact is observed on overall plant operation :‐
I. Increase in the Energy Consumption II. Descaling requirements and associated costs III. Increase in Maintenance Costs for Condenser tubes etc. ( since every time
the descaling is carried out, the tube life reduces than what it was originally designed for)
IV. Downtime / bottlenecks in production V. Operational hastles
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2.) Lack of good treatment means higher Make‐up Water Requirements
Reason In a cooling tower, as the water evaporates, the concentration of dissolved salts in the recirculating water increases. The number of times, these salts get concentrated is called “Cycles of Concentration”. With increase in the concentration of salts, the potential of scaling increases. Without good treatment chemicals present in water, lower concentration of salts is permitted in recirculating waters in order to avoid scaling / deposits. This necessitates blowing down of a lot of extra water and replacing it with equivalent quantity of good quality make‐up water.
Impact
Good chemical treatment programs permit Cycles of Concentration of 4‐ ‐ 7 ( depending upon make‐up water quality) , without any scaling or deposition problems. Whereas , if no good chemical treatment program is being used, the cycles of concentration may be restricted to only 1.5‐3.0 . This would mean increase in make‐up water requirements and costs.
Afore said problems generally been avoided with the chemical treatment to prevent the system again technology may vary in accord to the development of Water treating methodology . Generally Polymer Technology been used widely world wide An Propriety Blend of Various Polymers. CORROSION Corrosion means Metal reverting back to its own form means Iron reacting with oxide available in the water and form as Iron Oxide and remain in insoluble form in the water. It again be said as Ferric converting as Ferric Oxide. Corrosion is an Electrochemical Process by which a Metal returns to its Natural State. For example Mild Steel is an Commonly used Metal and is very Susceptible to Corrosion and will return to its Iron Oxide Statge. For Corrosion to occur a Corrosion Cell Consisting of an Anode and a Cathode and Electrolyte ( Water ) is Must. Metal Ions dissolved in Water at the Anodes and Electrically Charged Particles ( Electrons ) are left Behind, These Electrons Flow Through the Metal to Other Part Cathodes Where Electrons consumed. Above reaction resulting in loss Anodes received by Cathodes over a Period deposits from Cathodes removed at Water Pressure and get Carried along with the Water Flow and tend to deposits at Heat Transfer Surfaces And wherever the Turbulence And Pressure Drop Occurs and this Uniform Deposits over a period baked off called Iron Oxide Scale. TYPES OF CORROSION ♦ General Localized Corrosion ♦ Under Deposit ( or) Pitting Corrosion
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♦ Mechanical Stress Corrosion ♦ Stress Cracking Corrosion ♦ Erosion Corrosion ♦ Galvanized Corrosion General Corrosion General corrosion is what mentioned in the above Corrosion Column. Uniform Reaction of the same is called General Corrosion. Under Deposit ( or) Pitting Corrosion Once the System having Deposits when the Water flow through Chips under the Deposit and get concentrated by observing the Heat from the Atmosphere Chloride & Sulphate present in the Water Exceeds the Concentration and Reacts With Gases Hydroxide and forms as HydroChloride and Hydro Sulphate Once the Oxide been removed from it converting it as Hydrochloric & Sulphuric Acids respectively. Being and Acid which dissolves the metal and over a time gets Punctured under the deposit is called Under Deposit ( Or ) Pitting Corrosion. Scaling & Fouling is the main cause for this type of corrosion. Mechanical Stress Corrosion Deposit Occurred due to the Mechanical Stress ( Change Or Throttling the Valves at the Inlet of the Heat Exchangers ( or ) the condensers) resulting of Reduced flow at Heat Exchanger where the design Heat load increases with reduced Water Load due to which system get scaled very fast and again under the scale deposit corrosion Occurs means Mechanical Stress Corrosion. Erosion Corrosion While Bulk Water Enters into the Condensors (or) Heat Exchanger due to the flow Pressure and while penetrating resulting with Eroding the Heat Exchanger & Condensor Tubes at the Inlet side. These days Manufacturers are providing the Heat Exchanger & Condensors with End Cap to prevent it from Erosion Corrosion. Galvanized Corrosion As its been understood Corrosion is an Ion loss or transmission of Anodes to Cathodes. Any form of Corrosion is due to the loss of Anodes means Potential of Anodes are less when compare to Cathodes which is higher the the Anodes. Hence heat Exchanger & Condensors will be fitted with Galvanized ( Loaded With Sacrificing Anodes ) End Caps thus increasing the Anodic Potential high than the Cathodes ( Zita Potential Theory ) resulting which reception of Anodes from the End cap thus corroding it called Galvanized Corrosion . Solution for all the above said problems been managed with the chemical Treatment thus forming as filming Chemical layer arresting the Anodic Sites and Cathodic Sites to prevent the system from any form of corrosion.
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MICROBIAL Water consisting Organic & Inorganic by its own. oxygen present naturally Atmosphere is main cause producing the Micro & Macro Organisms. Types Of Microbial Growth Micro & Macro Growth Physical Algae Growth Fouling & Acid Leaching For Instance hydrocarbons or other Carbon Sources can serve as food for Slime forming Organisms. Also Organisms Growth depends upon the Availability of Oxygen Or Carbondioxide. But Such factors as the Amounts of Light and Moisture Significantly Affects the growth rate of Micro Organisms. The Same it will also lead to corrosion and also creates Nucleation Sites the second Stage of Scaling Process. There were few type of Bacteria like sulphate reducing Bacteria, Nitrate Reducing Bacteria, Iron reducing Bacteria ( Anaerobic Bacteria’s) will also cause Corrosion ( lives in the water with help of Carbon di Oxide and releases the toxic gases thus by reducing the Water pH means Acid Leach ). Slime is an typical occurred due to the Microbial growth . Slime is an Colorless & Slippery, Sticky layer formed in the Heat Exchanger Tubes only . COOLING WATER TECHNICAL PROBLEMS ( MICROBIOLOGY )
Microbiology is a branch of Science that deals with the study of microorganisms and their activities.
Microorganisms are tiny living form of life that cannot be seen by unaided eye. Most
microorganisms are unicellular.
The microorganisms are most abundant in soil and air and through these sources microorganisms
enter into water.
Microorganisms are important form of life because : ⇒ Microorganisms make‐up the bulk of the mass of biosphere
⇒ Not a single thing in the world is not prone to microbial attack
⇒ They are faster growing than higher organism
⇒ Microorganisms grow in very wide environmental condition than plant and animal
⇒ Microorganisms carry out many unique reactions of geochemical significance
e.g. Curdling of milk
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Epidemicas
Antibiotics production etc.
On nutritional requirement cooling water microorganisms are classified as : 1. Autotrophs ‐ They are self nourishing microorganisms and require light as energy source
and very low inorganic nutrients for cellular carbon generation. Example ‐ Algae 2. Heterotrophs ‐ These microorganisms require organic nutrients for their energy and
cellular carbon generation Example ‐ Bacteria 3. Chemolithotrophs ‐ These microorganisms require inorganic compounds for energy and
carbon generations. Light is not required. Example ‐ Sulfate reducing bacteria Sulfur oxidising bacteria Nitrifying bacteria Iron bacteria A typical bacterial cell is as given below : Cell wall ‐ Cell wall is outer covering which gives protection and specific shape to bacteria Flagella ‐ Flagella is locomotory organ made up of protein. Pilli ‐ Pilli are used for genetic material transfer from one cell to another cell. Cell membrane ‐ Cell membrane present below cell wall to support cell wall and help in function
of transport mechanism. Nuclear material ‐ Nuclear material in bacterial cell is DNA and it is not enclosed in nuclear
membrane. Ribosomes ‐ Ribosomes are useful in synthesis of enzymes and all enzymes are proteins in
nature. Plasmids ‐ Plasmids are extra chromosomal circular DNA responsible for specific characteristics
like resistance to biocide and chemicals etc. Microorganisms in cooling water are classified as : Microorganisms Bacteria Algae Fungi
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Cyanobacteria Diatom Aerobic (required O2) Anaerobic (do not require O2) Sulfate Reducing Bacteria Slime Sulfur Iron Nitrifying producing Oxidising Bacteria Bacteria Bacteria A. Bacteria : 1. Slime producing bacteria Source : 1) Air 2) Dirt 3) Make‐up water Nature : Aerobic Slime producers show marked diversity in their natural habit, shapes, sizes, physiological and
biochemical characters and activities. In nature large number of genera and species are present. Example of this type bacteria found in cooling water are Pseudomonas, Flavobacterium, Enterobacter, Klebsiella etc. all of them are called as "slime producing bacteria". They require organic source for their growth. Slime is an extracellular gelatinous consistent secretion. The formation of slime is more often than not dependent on the environmental conditions like temperature, availability of nutrients etc. Slime is mainly made up of polysaccharide. Polysaccharide may contain cellulose and amino acids which support growth of other microorganisms. These bacteria normally grow in temperature range 30 to 40oC and between pH 7 to 8 which is common for almost all cooling towers.
Problems associated with their growth : ∗ Deposition : Slime produced by these microorganisms entraps various suspended matter
like dust and corrosion products which form deposits. ∗ Corrosion : Slime produced by microorganisms deposit and prevent the corrosion inhibitor
to reach the metal surface and leads to corrosion. This is also called as under slime corrosion.
∗ Under slime SRB growth : Slime deposit on metal surface and underdeposit corrosion
starts. These deposits are favourable site for replication of sulfate reducing bacteria which accelerates rate of corrosion.
∗ Reduced heat transfer corrosion.
Slime fouls heat exchanger and reduces heat transfer efficiency.
B. Sulfate reducing bacteria : [SRB]
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Nature : Anaerobic Source : SRB are soil born Make up water If system having deposits If sulfuric acid is used to control pH then it increases sulfates & helps SRB to grow. Process contaminantions in water may accelerate growth of SRB
Example ‐ Desulfovibrio desulfuricans Desulfatomaculum
These are anaerobic bacteria and use sulfate as terminal electron acceptor and converts sulfate to sulfides. Hydrogen generated at cathodic site used for this reaction. SRB attack on metal is characterised by formation of black sulfide under which there is usually a deep pit. When cleaned out the interior surface of the pit has a characteristic bright silvery appearance. Temperature around 30oC and pH around 7.2 is suitable for SRB growth. Although they are anaerobic, some species can survive for a long period in presence of oxygen. Fig. Problems associated with SRB growth
Corrosion (pitting) :
Corrosion is observed on both mild steel, stainless steel. SRB with the help of enzyme
"Dehydrogenase" uses elemental hydrogen generated at cathodic site and reduces sulfate to sulfide. H2S generated combines with iron to form ferrous sulfide.
Also metabolic reaction gives rise to formation of iron hydroxide as corrosion product.
8 H2O ‐‐‐‐‐‐‐‐ 8 H
+ + 8 OH‐ ] ∏ Anodic dissolution of iron 4 Fe + 8 H+ ‐‐‐‐‐‐‐‐‐‐ 4 Fe++ + 8 H ] SO4
‐‐ + 8 H ‐‐‐‐‐‐‐ H2S + 2 H2O + 2 OH‐ ∏ Cathodic depolarization with enzyme
dehydrogenase Fe++ + H2S ‐‐‐‐‐‐‐ FeS + 2 H
+ ] 3Fe++ + 6 OH‐‐‐‐‐‐‐‐ 3 Fe(OH)2 ] ∏ Formation of corrosion product Net reaction is : 4 Fe + SO4
‐‐ + 4 H2O ‐‐‐‐‐‐‐‐ FeS + 3 Fe(OH)2 + 2 OH‐∏ Formation of corrosion
product Ferrous sulfide formed is cathodic to metallic iron
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pH drop ‐ H2S generated by SRB get oxidised by chlorine and hydrochloric acid formed. This
leads to pH drop and leads to higher chlorine consumption. H2S + Cl2 ‐‐‐‐‐‐‐‐ 2HCl + S
C) Sulfur oxidising bacteria (SOB) : Nature : Aerobic Source 1) Soil born 2) Make up water Example : Thiobacillus Thiomicrospira Sulfolobus Activity of SOB in cooling tower remains low because they require acidic pH to grow. Problems associated with SOB growth : pH drop : These microorganisms oxidise sulfur compound like H2S to sulfuric acid. Sulfuric
acid drastically reduce the pH of circulating water. 2 H2S + 2 O2 ‐‐‐‐‐‐‐‐‐‐‐‐‐> H2S2O3 + H2O 5 H2S2O3 + 4 O2 + H2O ‐‐‐‐‐‐‐‐‐‐> H2SO4 + 5 SO4
‐‐ + 4 So + 1OH 2So + 3 O2 + 2H2O ‐‐‐‐‐‐‐‐‐‐‐‐ 2 H2SO4 Reduction of pH of cooling water leads to corrosion. D) Nitrifying Bacteria : Nature : Aerobic Source 1) Soil born bacteria 2) Continuous leakage of Ammonia in cooling tower may proliferate growth of these bacteria Example : Nitrosomonas Nitrobacter Nitrosococcus Nitrovibrio
Nitrifying bacteria utilizes all nitrogenous compounds for energy generation and are aerobic in
nature. Favourable condition for their growth is temperature in range of 28 to 30oC and pH in between 7.0 to 8.0. Nitrifiers need very specific substrates. Their growth rate is quite slow as compared to heterotrophs but once established they are difficult to control.
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Problems associated with their growth : 1. pH drop : Nitrogenous compounds are oxidized by process of nitrosification and nitrites are
generated. These nitrites are then oxidised by process of nitrification to nitrates to nitric acid.
Nitrogenous compounds like NH3 Nitrosification Nitrites e.g. Nitrosomonas Nitrification Nitrovibrio e.g. Nitrobacter Nitrosococcus Nitrococcus Nitrospine Nitrates + Nitric Acid i.e. 2 NH3 + 3 O2 ‐‐‐‐‐‐‐‐‐> 2 HNO2 + 2 H2O HNO2 + ½O2 ‐‐‐‐‐‐‐‐‐‐‐ HNO3
Due to acid production pH drops locally and passivation layer get dissolved in it which leads to
pitting corrosion. Corrosion due to low inhibitor concentration : Systems where nitrites are used as corrosion
inhibitor is prone to attack by nitrifying bacteria. Nitrifying bacteria oxidise nitrite and due to non‐availability of nitrite corrosion takes place.
Nodules and cracks : Nitrate formed during process of nitrification are responsible for formation of
nodules and inter granular cracking. These nodules and cracks are breeding site for nitrifying bacteria.
E) Iron bacteria : Nature : Aerobic Source : 1) Soil born 2) Make up water Example : Gallionella Sphaerotilus Crenothrix Iron bacteria are aerobic in nature and of two different types : 1) Stalked e.g. Gallionella 2) Filamentous e.g. Sphaerotilus
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Crenothrix Clanothrix Leptothrix Problems associated with their growth : Slime formation ‐ Iron bacteria secrete voluminous slime which is brownish in colour. This slime
reduces heat transfer across cooling tower and heat exchangers. Deposition/Under deposit corrosion : Iron bacteria causes oxidation of soluble ferrous iron to
insoluble ferric hydroxide which deposit in the system. This deposition prevents corrosion inhibitor to reach metal surface i.e. under deposit corrosion.
Net reaction of iron oxidising bacteria is : 4 Fe++ + O2 + 4 H
+‐‐‐‐‐‐‐‐‐> 4 Fe+++ + 2 H2O Algae Nature : Aerobic Source ‐ Soil born Make up water Example ‐ Two types of algae found in cooling tower : 1) Cyanobacteria : Nostoc Anabena Chorella Nariculla etc 2) Diatoms : Synedra Gomphonema
Algae are unicellular/multicellular having colour like green/ bluish green/brownish with the help of the pigment chlorophyll it fixes atmospheric CO2 and prepares food with the help of sunlight and inorganic salt. Some species like chorella grow in dark condition producing brownish nodule like growth. Algae have tremendous tolerance to pH and temperature fluctuations. Algae which have silica in their cell wall are called as diatoms.
Problems associated with algal growth :
♦ Reduced heat transfer : Algal growth on cooling tower decks, fills, frame interfere with water droplet formation and reduce heat transfer across cooling tower. Algae also choke nozzles of cooling tower and tubes of heat exchanger and fouls the system.
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♦ Slime and fouled odour : Mucilagenous sheath secreted by many algae give rise to algal slime. Many algae produce malodorous oils in their cells notably furfuryl alcohol which are released after its death give malodour.
♦ Electrochemical corrosion : During photosynthesis oxygen is liberated by algae which is
responsible for "electro‐chemical corrosion". Fungi : Nature : Aerobic Example ‐ Aspergillus, Nocardia Ascomycetes, Basidomycetes Problems associated ‐ wood rots Source ‐ soil
Fungi are simple plants without chlorophyll. They are dependent on dead organic matter for their food. Fungi grow well at temperature between 25‐30oC but many species found in cooling water also grow at higher temperature. They prefer acidic pH for their growth. Fungi secrete enzyme that degrade cellulose and lignin from wooden structures of cooling tower. The excessive fungal growth on wood is called as wood rots.
Problems associated : 1. Wood rots ‐ excessive fungal growth on wood Rots colour ‐ Fungus involved White rot ‐ Basiodiomycetes Brown rot ‐ Imperfecti Soft rot ‐ Ascomycetes 2. Delignification of wood ‐ fungi secrete enzyme that degrade cellulose and lignin of wooden structures of cooling tower. All the above said problems are tackled chemically ( Killing the Bacteria ) using Oxidizing & Non Oxidizing Treatment Methodology. RO MEMBRANE FOULING – CAUSES & EFFECTS
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Membrane fouling is one of the major and serious concerns of a Reverse Osmosis system and has a direct bearing on the performance efficiency of the system. The following are the general causes of membrane fouling in an RO system. � Improper or inadequate pretreatment of Feed water � Higher Mineral load over design, in Feed water � Presence of low soluble salts like those of Aluminium, Barium, Strontium etc., in Feed water � Presence of Dual phase (Soluble/Colloidal) species like Iron, Silica, Manganese etc., in Feed water � Presence of higher Iron over design in Feed water � Presence of Oil or Organics in Feed water � Presence of Micro organic species in Feed water � Absence of (or) inadequate online Antiscalant program Owing to the above, the RO system suffers the following performance deficiencies. � Drastically reduced Yield against target � Poor Product water quality � Poor Salt rejection or increased Silt Density Index � Pressure build up across the system; increased energy cost of pumping � Increased load on Post RO equipment like Demineraliser or Mixed bed Polisher � Frequent plant outage for cleaning and attendant product loss and maintenance costs � Premature failure of membranes and attendant high costs of replacement � Overall imbalance of economics in product water costs . A well designed RO system, operating with the most appropriate online Antiscalant program, generally requires a maintenance cleaning only twice or thrice a year. Any increased need of cleaning frequency would clearly establish the incidence of above said problems.
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WASTE WATER TREATMENT Waste water Means Effluent or the Process Let out water as waste should be treated prior to its discharge. Treatment means the norms fixed by the Pollution Control Board of the respective State. Waste Water Shall be Segregated into Two Ways 1, Domestic Waste Water 2, Industrial Waste Water In the above Domestic Waste will be called as Sewage, Industrial Waste as Effluent. EFFLEUNT TREATMENT PROCESS As be understood treating the Waste Water to Discharge consist of the following Parameters. 1, BOD ( Biological Oxygen Demand ) 2, COD ( Chemical Oxygen Demand ) 3, TSS ( Total Suspended Solids ) 4, pH 5, Oil & Grease 6, TDS 7, Chlorides 8, Sulphates In the above Except TDS other parameters been reduced by adopting two kind of treating methodology Called AEROBIC & ANEROBIC TREATMENT AEROBIC TREATMENT Kind Of Treatment Methodology adopted by various Industries. Using Bacteria As major Element which Lives with the Help Oxygen feeded Continuously by Aerators maintaining the Oxygen levels enables the growth of Bacterial Load on the System and degrades the Organics in the Effluent thus reducing it to the desired limits. ANEROBIC TREATMENT Similar Process of the Above the change here is Bacteria been developed and maintained without the help of Oxygen. Normally these kind of systems been used only in the Industries like Distilleries, Sugar, Paper ( Making Virgin Pulp Using Cotton & Wood & Pharma ) which all the above carry a very high BOD, COD and other parameters to be reduced where Aerobic Treatment will not be very Effective towards reducing BOD & COD levels.. PROCESS SCHEME OF WASTE WATER TREATMENT 1, Collection Sump 2, Primary Clarifier 3, Primary Treated Water Sump
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4, Aeration Tank 5, Secondary Clarifier 6, Final Treated Water Sump 7, Pressure Sand Filter 8, Activated Carbon Filter in the above Primary Clarifier will not be included in the scheme for sewage Treatment. PRIMARY TREATMENT Primary Treatment widely done by the Industries like Textile, Automobile, Paper, Oil Industries. Process of Coagulation & flocculation adopted. COAGULATION The process where by dosing the Inorganic Chemical to reduce the inorganic load on the effluent which contributes to COD will reduced prior to the Secondary Aeration Biological Process for the further process of reduction of BOD & COD and other Parameters. Inorganic coagulants Like Alum which charged negative ( Cations) allowed to react with Anions presence in the effluent in form of TSS which contributes to COD majorly and BOD in accord with COD contribution towards BOD will be reduced. Means reduced Load of the pollutants prior to the biological Treatment been obtained. Once Coagulated particles forms tiny sized Sludge again Flocculated with the help of Polyelectrolyte ( Polymers ) which produce a big Polymeric chemical chain bonds the tiny sludge’s into bigger in size and settles down at Primary clarifier which again been drained to Sludge Drain beds. BIOLOGICAL PROCESS Primary Treated (or) Clarified water been taken for the further process to Aeration Tank ( Biological Process) where Bacteria been Cultured (or) developed with the help of Cow dunk (or) Artificial Freezed Culture Bacteria in which Millions of Bacterial Count been loaded in a medium and ready for use. Culture bacteria is again an Replacement for the usage of Cowdunk where the Actual need of cowdunk is about in tons against the culture bacteria which required to use in Kgs. Aeration Tank Which consists of fixed Aerators (or) Surface Aerators ( Presently widely been used is Diffused Membrane Aeration Technology which provide Electrical Cost saving with Enhanced Performance and maintenance free to operate at very low cost) which will Aerate ( feeding of the Atmospheric oxygen into the Aeration Tank ) in order to maintain the required Bacterial load termed as MLSS ( Mixed Liquid Suspended Solids ) . The level of MLSS is depends upon the Effluent however it may vary according to the BOD load and other organic Pollutants. Then the Outlet from the Aeration Tank Mixed along with Biosludge been taken to the secondary Clarifier and the Biosludge settles down and Treated water been filtered and been Discharged to the surface. Again the settled Biosludge been taken by means of a Circulation pump back to the Aeration Tank to enable the system to maintain the required MLSS at Aeration Tank. If the system is maintaining required mlss then the excess Biosludge been drained to Sludge Drain beds. However Sewage Treatment process will avoid the Primary Coagulation & Flocculation Process since the Domestic Waste Water does not carry of much Inorganic Load ( COD) hence it will be simply treated Biologically and been recycled for gardening Purpose and for Toilet Flushing.
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NOTE : Sewage Treated water not been recycled for any other Applications like Cooling Tower Make up Water (or) as Feed Water to Steam Boilers since treatability does not remain consistent and any Increased BOD & COD and escaped Biosludges from the Filters will cause higher Fouling rate and Can cause severe Biological Corrosion and can Tamper with.