Design Of Wastewater Treatment Plant Environmental Sciences Essay

envision Of Waste piss intervention institute Environmental Sciences EssayIndustrial sewer weewee make outment covers the mechanisms and processes employ to treat piddles that have been conta hourated in much or less way by industrial or commercial activities foregoing to its release into the environment or its re-use. It involves mainly three stages, c every(prenominal)ed primary, utility(prenominal) and 3rd preaching. Activated sludge process tin be used to treat the sewer water produces from Oushadi Ayurvedic Pharmaceuticals. contaminants include oils, particulate consentients, materials having high assimilations of biochemical substance atomic number 8 read ( figure) and hang solids (SS). Primary intercession consists of temporarily holding the sewage ,where moody solids kitty place to the bottom tour oil, cover and lighter solids rove to the protrude. The settled and floating materials argon removed and the outrideing liquid may be put outd or s ubjected to secondary interference. One major paradox faced by Oushadi was the complete removal of oil from ragingwater and this make up a threat to the use of treated water for their boilers. alternative intercession removes dissolved and hang biologic weigh. Secondary discussion is typically performed by ind comfortablying, water-borne micro-organisms in a managed habitat. Secondary manipulation may require a separation process to remove the micro-organisms from the treated water prior to discharge or tertiary intervention. Tertiary sermon is some ms define as anything more than than primary and secondary preaching.Comprising over 70% of the earths surface, water is undoubtedly the closely precious rude(a) resource that exists on our planet. Recycling of effluent in industries is therefore a process, which is a necessity rather than a luxury. effluent treatment is the process of removing contaminants from sewer water. It includes physical, chemical, and biol ogical processes to remove physical, chemical and biological contaminants. Its objective is to produce a intemperance blow (or treated effluent) and a solid drift or sludge suitable for discharge or reuse back into the environment. This material is often inadvertently contaminated with numerous toxi raftt radical and in organic fertiliser compounds. sewer water can stir taint of ground water, lakes, streams and rivers. It wastes and decreases the nume tempo of potable water available on earth, causes an dissymmetry in aquatic ecosystems and wastes the nutrients abideed in sewer water by not recycle them. Many industries use braggart(a) volumes of water in their manufacturing functions. Because some of this water becomes contaminated, it requires treatment onward discharge.Improvements in determining the terminations of industrial waste discharges have led to the adoption of stringent environmental laws, which define the distri andor point of treatment necessary t o protect water quality. Discharge permits, issued nether the national Pollutant Discharge Elimination System (NPDES), regulate the amount of pollutants that an industry can return to the water source. The permitted quantities atomic number 18 knowing to ensure that other users of the water lead have a source that meets their require, whether these needs atomic number 18 for municipal water supply, industrial or agricultural uses, or tiping and recreation. rumination is given(p) to the feasibility of removing a pollutant, as well as the inwrought assimilative capacity of the receiving stream. This assimilative capacity varies with the image and amount of pollutant.effluent treatment plants atomic number 18 intentional to convert liquid wastes into an acceptable last(a) effluent and to dispose of solids removed or generated during the process. In most cases, treatment is ingrained for both suspended and dissolved contaminants. Special processes be required for the r emoval of certain pollutants, such(prenominal) as phosphorus or heavier-than- vent metals. wastewater can be recycled for reuse in plant processes to invalidate disposal requirements. Thispractice too humiliates water consumption.Sahradaya College Of engineer Technology, Kodakara 1 architectural plan Of Wastewater give-and-take Plant1.1 POLLUTANTS IN effluentOrganic CompoundsThe amount of organic material that can be discharged safely is be by the effect of the material on the dissolved atomic number 8 take aim in the water. Organisms in the water use the organic function as a food source. In a biochemical reaction, dissolved atomic number 8 is wasted as the end products of water and atomic number 6 dioxide be formed. Atmospheric oxygen can replenish the dissolved oxygen supply, precisely only at a slow rate. When the organic load causes oxygen consumption to occur this resupply, thus dissolved oxygen level drops, leading to the death of fish and other aquatic lo ok. Under extreme conditions, when the dissolved oxygen concentration reaches zero, the water may turn corrosive and produce foul spirits, such as the rotten egg smell of hydrogen sulphide. Organic compounds atomic number 18 normally metric as chemical oxygen demand (COD) or biochemical oxygen demand ( skeleton).NutrientsNitrogen and phosphorus are essential to the growth of plants and other organisms. However, nitrogen compounds can have the same effect on a water source as carbon- containing organic compounds. authentic organisms use nitrogen as a food source and consume oxygen.Phosphorus is a concern because of algae blooms that occur in surface waters due to its presence. During the day, algae produce oxygen finished photosynthesis, but at night theyconsume oxygen.SolidsSolids discharged with a waste stream may settle immediately at the discharge pointor may remain suspended in the water. Settled solids cover the bottom-dwelling organisms, do disruptions in population and building a reservoir of oxygen-consuming materials. Suspended solids outgrowth the turbidity of the water, thereby inhibiting light transmittance. Deprived of a light source, photosynthetic organisms die. Some solids can coat fish gills andcause suffocation.Sahradaya College Of applied science Technology, Kodakara 2 pattern Of Wastewater intervention PlantAcids and AlkaliesThe natural buffering system of a water source is exhausted by the discharge of acids and alkalies. Aquatic life is postulateed by the wide swings in pH as well as the destruction ofbicarbonate alkalinity levels.MetalsCertain metals are toxic and affect industrial, agricultural, and municipal users of thewater source. Metals can cause product quality problems for industrial users. Large quantities of discharged salts necessitate expensive removal by downriver industries utilize the receiving stream for boiler makeup water.The contaminants in effluent are removed by physical, chemical and biological methods . The particularized method are classified as physical social unit operations, chemical unit processes and biological unit processes.1.2 Unit Operations and Process in Wastewater TreatmentTABLE 1.1 Operations and Process in Wastewater TreatmentContaminant Unit Operations/ Processes ClassificationsSuspended solidsScreening Sedimentation FloatationFiltration somatogenicBiodegradable OrganicsActivated Sludge Trickling Filters Rotating BiologicalContactorsBiologicalPhosphorus lime hydrate Coagulation chemicHeavy Metal Chemical Precipitation ChemicalSahradaya College Of plan Technology, Kodakara 3Design Of Wastewater Treatment PlantCHAPTER 2WASTEWATER CHARACTERISTICS2.1 WASTEWATER CHARACTERISTICSTo design a treatment process properly, movie of wastewater is perhaps the most critical step. Wastewater characteristics of importance in the design of a treatment process can be class into the following categories Temperature pH Colour and Odour carbonaceous substrates Nitrogen phosphor ous Chlorides Total and volatile suspended solids (TSS and VSS) Toxic metals and compounds Density Oil grease Alkalinity2.1.1 TemperatureThe temperature of wastewater is commonly higher than that of the local water supply, because of the addition of warm up water from household activities. As the specific heat of water is more than greater than that of air, the observed wastewater temperatures are higher than the local air temperatures during most of the year and are hotter only during the hottest summer months. Depending on the fixture and time of the year the effluent temperatures can either higher or lower than the corresponding influent values.2.1.1.1 nucleus of temperatureThe temperature of water is a real important arguing because of its effect on chemical reactions and reaction rates, aquatic life, and the suitability of the water for beneficial purposes. In addition, oxygen is less oil-soluble in warm water than in cold water. The increases in rate of biochemical re actions that accompanies an increase in temperature, combine with the decrease in the amount of oxygen present in surface waters, can often cause serious depletions in dissolved oxygen concentrations in summer months. best temperatures forbacterial activity are in range from 25 to 35oC.Aerobic digestion and nitrification boodle whenthe temperature rises to 50oC. When the temperature drops to nigh 15oC, methane producing bacteria become quite inactive and at about 5oC, the autotrophic nitrifying bacteria practicallySahradaya College Of Engineering Technology, Kodakara 4Design Of Wastewater Treatment Plantcease functioning. At 2oC, even the chemo heterotrophic bacteria acting on carbonaceous material become essentially dormant.2.1.2 pHThe hydrogen ion concentration is an important quantity parameter of both natural waters and wastewaters. The usual means of expressing the hydrogen ion concentration is as pH, which is defined as the negative logarithm of hydrogen ion concentratio n. The concentration range for the conception of most biological life is quite narrow and critical typically 6 to 9. Wastewater with a extreme concentration of hydrogen ion is troublesome to treat by biological means, an if concentration is not altered before discharge, the wastewater effluent may alter the concentration in the natural waters. For treated effluents, discharged to the environment the allowed pH range commonly varies from 6.5 to 8.5.The pH of fresh domestic waste water is slightly more than that of the water supply to the community. However, the onset of septic conditions may lower the pH while the presence of industrial wastes may produce extreme fluctuations.2.1.3 ODOUR AND tingeFresh domestic waste water has slightly soapy and plebeian odour and cloudy appearance depending upon its concentration, With the passage of time, the waste water becomes stale, darkening in colour with a pronounced colour due to microbial activity.2.1.3.1 OdourOdours are usually caus ed by gases produced by the de organic laws of organic matter or by substances added to the waste water. Fresh wastewater has a distinctive, slenderly disagreeable odour which is less objectionable than the odour of wastewater which has undergone anaerophilous decomposition. The most characteristic odour of stale or septic wastewater is hydrogen sulfide. Odours have been rated as the foremost concern of public relation to wastewater treatment facilities. Within the past few years, the check over of odour has become major consideration in the design and operation of wastewater collection, treatment and disposal facilities, especially with respect to public acceptance of these facilities.Effect of OdoursThe importance of odours at low concentrations in human terms is relate primarily to psychological stress they produce rather than to the harm they do to the body. Offensive odours can cause poor appetite, lower water consumption, muck up respiration, nausea and vomiting and menta l perturbation. Some odorous compounds are toxic at elevatedconcentrations.Sahradaya College Of Engineering Technology, Kodakara 5Design Of Wastewater Treatment Plant2.1.3.2 ColourHistorically, the term condition was used along with composition and concentration was used to describe waste water. Conditions refer to the age of wastewater, which is find out qualitatively by its colour and odour. Fresh wastewater is usually a light brownish grey colour. However as the travel time in collection system increases, and more anaerobic conditions develop, the color of waste water change overs sequentially from grey to dark grey and ultimately black . When the color of wastewater is black, the wastewater is described as septic . In most cases the grey , dark grey and black color of wastewater is due to ecesis of metallic sulphites which form as the sulphide produced under anaerobic conditions react with metals in the wastewater.2.1.4 CARBONACEOUS CONSTITUENTSCarbonaceous constituents are measured by BOD, COD or TOC analyses. While the BOD has been the common parameter to characterize carbonaceous material in wastewater, COD is becoming more common in most current comprehensive computer trick design models.2.1.4.1 Biochemical Oxygen demandThe BOD test gives a measure of the oxygen utilized by bacteria during the oxidation of organic material contained in a waste water sample. The test is establish on the premise that all the biodegradable organic material contained in the wastewater sample will be oxidized to CO2 and H2O, using molecular of oxygen as the electron acceptor. Hence, it is a direct standard of oxygen requirements and an indirect measure of biodegradable organic matter.2.1.4.2 Chemical oxygen demandThe COD test is based on the principal that most organic compounds are oxidized to CO2 and H2O by knockout oxidizing agents under acid conditions. The measurement represents the oxygen that would be needed for aerobic microbial oxidation, assuming that all o rganics are biodegradable.2.1.4.3 Total Organic CarbonThe total carbon analyzer allows a total soluble carbon analysis to be made directly on an aqueous sample. In many cases TOC can be correlated with COD and occasionallywith BOD values.Sahradaya College Of Engineering Technology, Kodakara 6Design Of Wastewater Treatment Plant come across panel 2.1 Definition of Solids Found in WastewaterTest DescriptionThe residual remaining after a wastewaterTotal Solids (TS)Total vapourific Solids(TVS)sample has been evaporated and dried at a contract temperature (103-105oC).Those solids that can be volatilized and burned off when the TS are ignite (50050 oC).oTotal indomitable Solids (TFS) The residue that remains after TS are ignited(50050 C). pile of the TS retained on a tense with a specified think size, measured after being dried at a specified temperature (105oC). TheTotal Suspended Solids (TSS)Volatile Suspended Solids (VSS) Settle able Solidsfilter used most commonly for the d etermination of TSS is Whatman glass roughage filter which has a nominal pore size of about1.58m.Those solids that can be volatilized and burned off when the TSS are ignited (50050 oC).Suspended solids, expressed as mL/L, that will settle out of suspension with in a specified period of time.Sahradaya College Of Engineering Technology, Kodakara 7Design Of Wastewater Treatment PlantCHAPTER 3STAGES OF WASTEWATER TREATMENT3.1 STAGES OF WASTEWATER TREATMENT1) Preliminary Treatment Removal of wastewater constituents such as rags, sticks, floatable grit and grease that may cause nourishment or operational problems with treatment operations, process and ancillary systems.2) Primary treatment Removal of a portion of suspended solids and organic matter from the wastewater.3) go on Primary Enhanced removal of suspended solids and organic matter from the wastewater typically accomplished by chemical addition to wastewater.4) Secondary treatment Removal of biodegradable organic matter (in s olution or suspension)5) Secondary with nutrient removal Removal of biodegradable organics, suspended solids and nutrients. (N2, P or both N2 and P).6) Tertiary treatment Removal of residual suspended solids (after secondary treatment)usually by granular medium filtration or micro screens. Disinfection is too typically a part of tertiary treatment. Nutrient removal is often included in this definition.7) Advanced Tertiary Removal of dissolved and suspended materials remaining after normal biological treatment when required for conglomerate water reuse operations.3.2TREATMENT PROCESS FLOWSHEETDepending on the contaminants to be removed, an almost numberless number of process combinations can develop using the unit operations and process. The term lessen sheet is used to describe particular combinations of unit operations and process used to achieve a specific treatment objective. Apart from the analysis of the technical feasibility of the individual treatment methods, the invol ve accrue-sheets configuration will depend on factors such as (1) the needs of the of the clients needs, (2) the designers past experience, (3) regulatory agency policies on the application of specific treatment methods, (4) the availableness of equipment suppliers, (5) what use can be made of existing facilities, (6) the availability of qualified operating personnel, (7) initial construction costs and (8) future operation and living costs.Sahradaya College Of Engineering Technology, Kodakara 8Design Of Wastewater Treatment PlantThe Process menstruation Sheet proposed in this project for the wastewater treatment is as shown below Figure 3.1 Process feed Sheet board 3.1 LEVELS OF WASTEWATER TREATMENT TREATMENT LEVEL DESCRIPTIONRemoval of wastewater constituents Such asPreliminaryrags,sticks, floatables,grit and grease that may cause guardianship or operational problems with the treatment operations.Primary Removal of apportion of the suspended solids and organic matters from was tewater.Enhanced removal of suspended solids andAdvanced Primaryorganic matters from wastewater typically accomplished by chemical addition or filtration.Secondary Removal of biodegradable matters and suspended solidsSecondary with Nutrient removal Removal of biodegradable organics and nutrients.Tertiary Removal of residual suspended solids usually by granular medium filtration or micro screenSahradaya College Of Engineering Technology, Kodakara 9Design Of Wastewater Treatment PlantCHAPTER 4 books REVIEW4.1 SCREENINGThe first unit operation generally encountered in wastewater is screening. A screen is a device with opening, generally of equivalent size, that is used to retain solids found in the influent wastewater to the treatment plant. The principle role of screening is to remove coarse material from the work stream that could damage subsequent process equipment, reduce overall treatment process reliability and effectiveness and contaminate waterways.Fine screens are sometimes used in place of or following coarse screens where greater removal of solids are required to protect process equipment and eliminate materials that may inhibit the beneficial reuse of bio-solids.All aspects of screening, removal, disco biscuit and disposal must be considered in the application of screening devices including1. The degree of screening removal required, because of potential effects of downstream processes2. Health and safety of operators as screenings contain pathogenic organism that attract insects3. Odour potential4. Requirements for handling transport and disposal5. Disposal optionsTwo general pillowcases of screens, coarse screens and fine screens are used in overture treatment of wastewater. Coarse screens have piss opening ranging from 6 -150mm, Fine screens have openings ranging less than 6mm. Micro screens will generally have screen opening less than 50 m, are used principally in removing fine solids from treated effluents. Bar force out for the removal of coarse solids.4.2 GRIT REMOVALRemoval of grit from wastewater may be accomplished in grit houses or by the centrifugal separation of solids. mainstay house are knowing to remove grit, consisting of sand, gravels, cinders or other heavy solid materials that have subsidence velocities of specific gravities substantially greater than those of the organic putrescible solids in wastewater. gritstone chamber are most commonly located after the occlude screen and before the primary sedimentation army tanks.Sahradaya College Of Engineering Technology, Kodakara 10Design Of Wastewater Treatment PlantLocating grit chamber beforehand of wastewater pump when desirable, would involve placing them at massive depth at added expense. It is therefore deem more economical to pump the wastewater, including the grit to grotto chamber located at a convenient position frontward of the treatment plant units, recognising that pumps may require greater maintenance.4.2.1 Why Grit is removed? Prevent wear on pumps ingathering in clarifiers Accumulation in aeration tank Accumulation in digesters Clogging of sludge steaming4.2.2 TYPES OF GRIT CHAMBERSGrit chambers are provided to (1) Reduce formation of heavy deposits in pipelines, channels and conduits (2) reduce the frequency of digester cleaning caused by excessive accumulation of grit (3) Protect moving mechanical equipment from clams and accompanying abnormal wear.There are three general type of grit chamber swimming break away either rectangular or square configuration aerated or vortex type. The aeration type consists of a spiral give ear aeration tank where the spiral stop number is induced and controlled by the tank dimension in and quantity if air supplied to the unit. The vortex type consists of cylindrical tank, in which the flow enter tangentially vortex flow pattern centrifugal and gravitational forces causes the grit to separate. Design of grit chamber is commonly based on removal of grit particles ha ving aspecific gravity of 2.65 and wastewater temperature 15.5oC. However analysis of gritremoval info indicates the specific gravity ranges from 1.3-2.7. horizontal Flow Grit ChambersIn the horizontal flow type the flow passes through the chamber in a horizontal direction and the straight line velocity of flow is controlled by the dimension of the unit, an effluent distribution gate and a weir at the effluent end. Rectangular and square Horizontalflow grit chambers have been used for many years.Sahradaya College Of Engineering Technology, Kodakara 11Design Of Wastewater Treatment PlantTypical Design Information for Horizontal Flow Grit ChamberTable 4.1ItemDetention timeHorizontal velocitySettling velocity for removal of .21mm materialSettling velocity for removal of .15mm materialSIUnitRangeTypicals45-9060m/s.25-.4.3m/min1-1.31.15m/min.6-.9.75%30-4036%25-5030Head loss in a control section as % depth in channelAdded length registration for inlet and outlet turbulenceHorizontal- V elocity Grit ChambersThey are controlled by either a Parshall flume Proportional weirParshall fume is used more widely due to less head loss than the weir. The flume and weir are too used to measure flow rates. In the chamber, a unremitting horizontal velocities is maintained by proper cross-sectional geometry of the chamber. Horizontal velocity must be adequate to keep the organic matter in suspension. Horizontal velocities should be sufficient so as to foresee scouring of settled grit along the bottom of the channel. Values of .23-.38m/s are common.4.3 FLOW EQUALIZATIONProcess for water treatment work best with uniform conditions. Shock to the bioprocesses in the form of sudden change in the concentration of nutrients can upsets. If the concentrations or flow rates of the waste vary greatly, dosages for treatment must be constantly be read merelyed. Flow equalization is a method used to overcome the operational problems caused by flow rate variation, to improve the performanc e of downstream process, and to reduce the size and cost of t downstream treatment facilities.Flow equalisation is damping of flow rate variations to achieve a constant or nearly constant flow rate and can be applied in a number of different situations depending on characteristics of collection system. There may be aeration both to keep the unruffled frombecoming anaerobic and smelly and to biodegrade some of the organic compound present.Sahradaya College Of Engineering Technology, Kodakara 12Design Of Wastewater Treatment PlantThe principle applications are for the equalisation of1. Dry weather flow to reduce the peak flow and loads.2. Wet weather flow in sound collection systems experiencing inflow and infiltration.3. Combined storm water and sanitary system flows.In the line arrangement all of flow passes through equalisation basin. This arrangement can be used to achieve considerable amount of concentration and limits its divert into equalisation basin. Although the pumping r equirements are cut back in this arrangement, the amount of constituents concentration damping is intimately reduced.The principle benefits that are cited as derived from application of flow equalisation are1. Biological treatment is enhanced, because shock loadings are eliminated or minimised, inhibiting substances can be diluted and pH can be stabilised.2. The effluent quality and thickening performance of secondary sediment tankfollowing biological treatment is improved consistency in solid loading.3. Effluent filtration surface area requirements are reduced, filtered performance is improved and more uniform filter back wash cycles are possible by lower hydraulic loading.4. In chemical treatment, damping of mass loading improves chemical feed control and process reliability.5. Often the rest of the plant designed with a smaller equipment( less capital investment) because of this improvement in performance. mischief of flow equalisation include Relatively large land areas are re quired. Equalisation facilities may have to be covered for odour control near residential area. Additional operation and maintenance required with child(p) cost is increased.4.4 PRIMARY SEDIMENTATIONThe objective of treatment by sedimentation is to remove readily settle able solids and floating materials and thus reduce the suspended solids content. Primary sedimentation is used as a preliminary step in the further processing of the waste water. Efficiently designed and operated primary sedimentation tanks should remove from 50-70% of the suspended solids and from 25-40% of the BOD.Sedimentation tanks have also been used as storm water retention tanks which are designed to provide a moderate cargo deck period (10-30mins) for overflows from either combined sewers and storms sewers. The purpose of sedimentation is to remove a substantial portion of organic solids that otherwise would be discharged directly to the receiving waters. Sedimentation tanks have also beenused to provide de tention periods sufficient for effective disinfection of such overflows.Sahradaya College Of Engineering Technology, Kodakara 13Design Of Wastewater Treatment Plant4.4.1DESCRIPTIONAlmost all treatment plants are mechanically cleaned sedimentation tanks of standardized circular or rectangular design. The selection of the type of sedimentation unit for a given application is governed by the size of the installation, by rules and regulations of local control authorities, by local site conditions and by the experience and judgment of the engineer. Two or more tanks have to be provided so that the process may remain in operation when one tank is out of service for maintenance and repair work.RECTANGULAR TANKSRectangular sedimentation tanks may use either chain and flight solids collectors or travelling bridge type collectors. The solids remission in the tank are scraped solids hoppers in small tanks and transfers troughs in large tanks. In every long unit two collection mechanisms can be used to scrape solids to collection points near the middle of the tank length. Where possible, it is desirable to locate solids pumping facilities close to the collection hoppers.4.4.2 SEDIMENTATION TANK effectThe might of sedimentation basins with respect to removal of BOD and TSS is reduced by1. Eddy currents formed by inertia of incoming fluid2. Wind induced circulation cells formed in uncovered tanks3. Thermal convection currentsBOD AND TSS REMOVAL R=WhereR expected removal efficiency t- detention timea, b empirical constants4.4.3 DETENTION TIMEThe bulk of finely divided solids reaching primary sedimentation tanks is incompletely flocculated but is susceptible to flocculation. Flocculation is aided by eddying motion of the fluid within tanks and topic through the coalescence of fine particles at a rate that is a function of their concentration and of the natural ability of the particles to coalesce upon collision. Coalescence of a suspension of solids becomes more complet e as time elapses, thus detention time is a consideration in the design of sedimentation tank. usually primary sedimentation tanks are designed, to provide 1.5-2.5hrs of detention basedon the average rate of waste water.Sahradaya College Of Engineering Technology, Kodakara 14Design Of Wastewater Treatment Plant4.4.4 SCOUR VELOCITYTo avoid the resuspension or inhalation of resuspended particles horizontal velocity through the tank should be kept considerably low. The following equation gives criticalvelocity.( )VH= Where VH Horizontal velocity that will just produce scour, LT-1 (m/s)K Constant that depends on type of material being scoured s Specific Gravit