Design Of Wastewater Treatment Plant Environmental Sciences Essay

plan Of Waste pissing Treatment do Environmental Sciences EssayIndustrial eat up weewee inter nonplus covers the mechanisms and processes employ to treat waters that have been contaminated in virtually way by industrial or commercial activities prior to its release into the environment or its re-use. It involves mainly three stages, called native, lowly and tertiary interposition. Activated sludge process discount be utilize to treat the wastewater nominates from Oushadi Ayurvedic Pharmaceuticals. Contaminants include oils, functioniculate solids, materials having mettlesome concentrations of bio chemic oxygen invite (BOD) and hang solids (SS). chief(a) treatment consists of temporarily holding the sewage ,where gravid solids potful define to the bottom while oil, smear and unmortgageder solids float to the surface. The settled and floating materials ar aloof and the remaining liquid may be discharged or subjected to secondary treatment. One major problem fa ced by Oushadi was the complete removal of oil from wastewater and this posed a threat to the use of treated water for their boilers. Secondary treatment removes fade out and hang biologic matter. Secondary treatment is typically performed by inhering, water-borne micro-organisms in a managed habitat. Secondary treatment may require a legal separation process to remove the micro-organisms from the treated water prior to discharge or tertiary treatment. ordinal treatment is sometimes de handsomed as anything more than primary and secondary treatment.Comprising over 70% of the earths surface, water is undoubtedly the most precious vivid resource that exists on our planet. Recycling of wastewater in industries is therefore a process, which is a necessity preferably than a luxury. sewer water treatment is the process of removing contaminants from wastewater. It includes physical, chemic, and biological processes to remove physical, chemical and biological contaminants. Its o bjective is to produce a waste stream (or treated effluent) and a solid waste or sludge suitable for discharge or reuse back into the environment. This material is often unwittingly contaminated with many toxic organic and inorganic compounds. Wastewater can evidence contamination of ground water, lakes, streams and rivers. It wastes and decreases the amount of potable water available on earth, causes an imbalance in aquatic ecosystems and wastes the nutrients contained in wastewater by not recycling them. Many industries use large volumes of water in their manufacturing operations. Because some of this water becomes contaminated, it requires treatment before discharge.Improvements in determining the resolutions of industrial waste discharges have led to the adoption of stringent environmental laws, which define the degree of treatment necessary to protect water quality. Discharge permits, issued under the National Pollutant Discharge Elimination System (NPDES), regulate the amou nt of pollutants that an industry can return to the water source. The permitted quantities are designed to ensure that other users of the water willing have a source that meets their inevitably, whether these needs are for municipal water supply, industrial or agricultural uses, or fishing and recreation. Consideration is given to the feasibility of removing a pollutant, as well as the natural assimilative depicted object of the receiving stream. This assimilative capacity varies with the type and amount of pollutant.Wastewater treatment plants are designed to convert liquid wastes into an acceptable final effluent and to dispose of solids removed or generated during the process. In most cases, treatment is required for both suspended and dissolved contaminants. Special processes are required for the removal of certain pollutants, such as phosphorus or heavy metals. Wastewater can be recycled for reuse in plant processes to strike down disposal requirements. Thispractice also re duces water consumption.Sahradaya College Of engine room Technology, Kodakara 1 excogitate Of Wastewater Treatment deeds1.1 POLLUTANTS IN WASTEWATEROrganic CompoundsThe amount of organic material that can be discharged safely is defined by the impression of the material on the dissolved oxygen take aim in the water. Organisms in the water use the organic matter as a solid food source. In a biochemical reaction, dissolved oxygen is consumed as the end products of water and carbon dioxide are formed. Atmospheric oxygen can replenish the dissolved oxygen supply, but only at a slow rate. When the organic load causes oxygen consumption to exceed this resupply, thus dissolved oxygen level drops, leading to the death of fish and other aquatic life. Under extreme conditions, when the dissolved oxygen concentration reaches zero, the water may turn black and produce foul odours, such as the rotten egg smell of total heat sulphide. Organic compounds are normally measured as chemical oxyg en demand ( have words) or biochemical oxygen demand (BOD).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. Certain 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 through photosynthesis, but at iniquity 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, ca use disruptions in population and building a reservoir of oxygen-consuming materials. hang solids increase the turbidity of the water, thereby inhibiting light transmittance. strip of a light source, photosynthetic organisms die. Some solids can coat fish gills andcause suffocation.Sahr adaya College Of Engineering Technology, Kodakara 2Design Of Wastewater Treatment PlantAcids and AlkaliesThe natural buffering system of a water source is exhausted by the discharge of acids and alkalies. Aquatic life is affected by the wide swings in pH as well as the destruction ofbicarbonate alkalinity levels.metallic elementsCertain 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 downstream industries using the receiving stream for boiler makeup water.The contaminants in wastewater are removed by physical, chemical and biological methods. The ad hoc method are classified as physical unit operations, chemical unit processes and biological unit processes.1.2 social unit Operations and Process in Wastewater TreatmentTABLE 1.1 Operations and Process in Wastewater TreatmentContaminant Unit Operations/ Pr ocesses Classifications hang solidsScreening Sedimentation FloatationFiltrationPhysicalBiodegradable OrganicsActivated Sludge Trickling Filters Rotating biologicContactorsBiologicalPhosphorusLime CoagulationChemicalHeavy Metal Chemical Precipitation ChemicalSahradaya College Of Engineering Technology, Kodakara 3Design Of Wastewater Treatment PlantCHAPTER 2WASTEWATER CHARACTERISTICS2.1 WASTEWATER CHARACTERISTICSTo design a treatment process properly, characterization of wastewater is perhaps the most critical step. Wastewater feature films of importance in the design of a treatment process can be grouped into the following categories Temperature pH Colour and Odour Carbonaceous substrates Nitrogen Phosphorous Chlorides Total and volatile suspended solids (TSS and VSS) Toxic metals and compounds Density Oil turd Alkalinity2.1.1 TemperatureThe temperature of wastewater is commonly higher than that of the local water supply, because of the addition of warm water from household acti vities. As the specific heat of water is much great than that of air, the observed wastewater temperatures are higher than the local air temperatures during most of the course of instruction and are hotter only during the hot trial run summer months. Depending on the location and time of the year the effluent temperatures can either higher or lower than the corresponding influent values.2.1.1.1 Effect of temperatureThe temperature of water is a very important parameter 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 soluble in warm water than in cold water. The increases in rate of biochemical reactions that accompanies an increase in temperature, combined with the decrease in the measuring stick of oxygen present in surface waters, can often cause serious depletions in dissolved oxygen concentrations in summer months. Optimum temperatures forbacterial activity are in range from 25 to 35oC.Aerobic digestion and nitrification stops whenthe temperature rises to 50oC. When the temperature drops to about 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 minus logarithm of hydrogen ion concentration. The concentration range for the existence of most biological life is quite narrow and critical typically 6 to 9. Wastewater with a extreme concentration of hydrogen ion is difficult to treat by biological means, an if concentration is not motleyed before discharge, the wastewater effluent may alter the concentration in the natural waters. For treated effluents, discharged to the environment the allowed pH range usually varies from 6.5 to 8.5.The pH of fresh domestic waste water is some 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 odor AND COLOURFresh domestic waste water has slightly soapy and earthy odour and cloudy appearance depending upon its concentration, With the passage of time, the waste water becomes stale, change in colour with a pronounced colour due to microbial activity.2.1.3.1 OdourOdours are usually ca apply by gases produced by the de papers of organic matter or by substances added to the waste water. Fresh wastewater has a distinctive, somewhat disagreeable odour which is less objectionable than the odour of wastewater which has underg unity anaerobic decomposition. The most charac teristic odour of stale or septic wastewater is hydrogen sulfide. Odours have been rated as the foremost concern of public relative to wastewater treatment facilities. deep down the past few years, the control of odour has become major consideration in the design and operation of wastewater collection, treatment and disposal facilities, especially with watch to public acceptance of these facilities.Effect of OdoursThe importance of odours at low concentrations in human terms is related 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, impair respiration, nausea and vomiting and mental 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 determined 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 changes consecutive from grey to inglorious 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 formation 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, adopt or TOC analyses. While the BOD has been the common parameter to characterize carbonaceous material in wastewater, gravel is becoming more common in most current comprehensive computer simulation design models.2.1.4.1 Biochemical Oxygen demandThe BOD test gives a mea sure of the oxygen utilized by bacteria during the oxidation of organic material contained in a waste water sample. The test is ground 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 measure 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 strong oxidizing agents under acid conditions. The measurement represents the oxygen that would be needed for aerobic microbial oxidation, assuming that all organics 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, Ko dakara 6Design Of Wastewater Treatment PlantTable 2.1 Definition of Solids Found in WastewaterTest explanationThe residue remaining after a wastewaterTotal Solids (TS)Total Volatile Solids(TVS)sample has been evaporated and dried at a specified temperature (103-105oC).Those solids that can be volatilized and burned off when the TS are ignited (50050 oC).oTotal Fixed Solids (TFS) The residue that remains after TS are ignited(50050 C).Portion of the TS hold on a filter with a specified pore size, measured after universe dried at a specified temperature (105oC). TheTotal Suspended Solids (TSS)Volatile Suspended Solids (VSS) Settle able Solidsfilter used most commonly for the determination of TSS is Whatman glass fiber filter which has a titulary 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 handling3.1 STAGES OF WASTEWATER TREATMENT1) Preliminary Treatment removal of wastewater constituents such as rags, sticks, floatable grit and grease that may cause maintenance or operational problems with treatment operations, process and ancillary systems.2) Primary treatment Removal of a peck of suspended solids and organic matter from the wastewater.3) move 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 solution 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 also typica lly 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 various water reuse applications.3.2TREATMENT PROCESS consortSHEETDepending on the contaminants to be removed, an almost limitless number of process combinations can develop using the unit operations and process. The term be given 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 exact flow-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 availability of equipment suppliers, (5) what use can be made of existing facilities, (6) the a vailability of qualify operating personnel, (7) initial construction costs and (8) future operation andmaintenance costs.Sahradaya College Of Engineering Technology, Kodakara 8Design Of Wastewater Treatment PlantThe Process incline Sheet proposed in this project for the wastewater treatment is as shown below Figure 3.1 Process watercourse SheetTable 3.1 LEVELS OF WASTEWATER TREATMENT TREATMENT LEVEL DESCRIPTIONRemoval of wastewater constituents Such asPreliminaryrags,sticks, floatables,grit and grease that may cause maintenance or operational problems with the treatment operations.Primary Removal of apportion of the suspended solids and organic matters from wastewater.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 residua l 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 uniform 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 flow stream that could ill-use subsequent process equipment, reduce overall treatment process reliability and effectiveness and contaminate waterways.Fine screens are sometimes used in come forth of or following coarse screens where great removal of solids are required to protect process equipment and eliminate materials that may inhibit the beneficial reuse of bio-solids. entirely aspects of screening, removal, transport and disposal must be considered in the application of screening devices inc luding1. The degree of screening removal required, because of potential effects of downstream processes2. Health and refuge of operators as screenings contain pathogenic organism that attract insects3. Odour potential4. Requirements for handling transport and disposal5. Disposal optionsTwo general types of screens, coarse screens and fine screens are used in preliminary treatment of wastewater. Coarse screens have clear 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 rack for the removal of coarse solids.4.2 GRIT REMOVALRemoval of grit from wastewater may be accomplished in grit chambers or by the motor(a) separation of solids. Grit chambers are designed to remove grit, consisting of sand, gravels, cinders or other heavy solid materials that have subsiding velocities of specific gravities substantially greater tha n those of the organic putrescible solids in wastewater. Grit chamber are most commonly located after the bar screen and before the primary bank deposit tanks.Sahradaya College Of Engineering Technology, Kodakara 10Design Of Wastewater Treatment PlantLocating grit chamber ahead of wastewater pump when desirable, would involve placing them at broad depth at added expense. It is therefore deem more economical to pump the wastewater, including the grit to grot chamber located at a convenient position ahead of the treatment plant units, recognising that pumps may require greater maintenance.4.2.1 Why Grit is removed? Prevent wear on pumps solicitation in clarifiers Accumulation in aeration tank Accumulation in digesters Clogging of sludge piping4.2.2 TYPES OF GRIT CHAMBERSGrit chambers are provided to (1) Reduce formation of heavy deposits in pipelines, stemmas and conduits (2) reduce the frequency of digester cleaning caused by excessive accumulation of grit (3) Protect moving mech anical equipment from abrasion and accompanying brachydactylic wear.There are three general type of grit chamber Horizontal flow either angulate or square configuration expose or vortex type. The aeration type consists of a spiral flow aeration tank where the spiral swiftness 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 having aspecific gravity of 2.65 and wastewater temperature 15.5oC. However analysis of gritremoval data 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 allowance for inlet and outlet turbulenceHorizontal- Velocity Grit ChambersThey are controlled by either a Parshall flume Proportional weirParshall green goddess is used more widely due to less head loss than the weir. The flume and weir are also used to measure flow rates. In the chamber, a constant horizontal velocities is maintained by proper cross-sectional geometry of the chamber. Horizontal velocity must be adequate to keep the or ganic matter in suspension. Horizontal velocities should be sufficient so as to prevent scouring of settled grit along the bottom of the channel. Values of .23-.38m/s are common.4.3 FLOW EQUALIZATIONProcess for water treatment works 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 readjusted. Flow equalization is a method used to overcome the operational problems caused by flow rate variation, to improve the performance 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 peregrine frombecoming anaerobic and smell y 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 sanitary 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 turn into equalisation basin. Although the pumping requirements are reduced in this arrangement, the amount of constituents concentration damping is considerably 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 an d thickening performance of secondary sediment tankfollowing biological treatment is improve 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.Disadvantage of flow equalisation include Relatively large land areas are required. Equalisation facilities may have to be covered for odour control near residential area. Additional operation and maintenance required Capital 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 pr eliminary step in the further bear on 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 computer storage tanks which are designed to provide a moderate cargo area 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 detention 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 governe d by the size of the installation, by rules and regulations of local control authorities, by local turn up 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 ice chestSRectangular sedimentation tanks may use either chain and flight solids collectors or travelling bridge type collectors. The solids settling in the tank are scraped solids hoppers in small tanks and transfers troughs in large tanks. In every long unit cardinal 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 PERFORMANCEThe efficiency 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 aid by eddying motion of the fluid within tanks and proceeds 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 complete as time elapses, thus detention time is a consideration in the design of sedimentation tank. Normally 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 stirring of resuspended particles horizontal velocity through the tank should be unplowed 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