Envi engg water and wastewaterPresentation Transcript
A. Surface sources such as: 1. Ponds and Lakes 2. Streams and Rivers 3. Storage resources ( Dams )B. Subsurface or Underground sources such as: 1. Springs 2. Wells ( Open and Tube- wells )
LAKE A lake is a body of relatively still fresh orsalt water of considerable size, localized in abasin, that is surrounded by land apart from ariver, stream, or other form of moving water thatserves to feed or drain the lake. Lakes are inlandand not part of the ocean and therefore aredistinct from lagoons, and are larger and deeperthan ponds. Lakes can be contrasted with riversor streams, which are usually flowing. Howevermost lakes are fed and drained by rivers andstreams.
Natural lakes are generally found inmountainous areas, rift zones, and areas withongoing glaciations. Other lakes are found inendorheic basins or along the courses of maturerivers. In some parts of the world there are manylakes because of chaotic drainage patterns leftover from the last Ice Age. All lakes aretemporary over geologic time scales, as they willslowly fill in with sediments or spill out of thebasin containing them.
POND A pond is a body of standing water, eithernatural or man-made, that is usually smallerthan a lake. They may arise naturally infloodplains as part of a river system, or they maybe somewhat isolated depressions (examplesinclude vernal pools and prairie potholes).Usually they contain shallow water with marshand aquatic plants and animals. A few animalsalso make ponds, including both alligators andbeavers. The type of life in a pond is generallydetermined by a combination of factors includingwater level regime (particularly depth andduration of flooding) and nutrient levels, butother factors may also be important, includingpresence or absence of shading by trees, presenceor absence of streams, effects of grazinganimals, and salinity.
Humans also make ponds. A wide variety ofman-made bodies of water are classified asponds. Some ponds are created specifically forhabitat restoration, including water treatment.Others, like water gardens, water features andkoi ponds are designed for aestheticornamentation as landscape or architecturalfeatures. Fish ponds are designed for commercialfish breeding, and solar ponds designed to storethermal energy. Standing bodies of water such as puddles,ponds, and lakes are often categorized separatelyfrom flowing water courses, such as a brook,creek, or stream.
STREAM A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill (occasionally ghyll), kill, lick, rill, river, syke, bayou, rivulet, streamag e, wash, run or runnel. Streams are important as conduits in the watercycle, instruments in groundwater recharge, and corridorsfor fish and wildlife migration. The biological habitat in theimmediate vicinity of a stream is called a riparian zone.Given the status of the ongoing Holoceneextinction, streams play an important corridor role inconnecting fragmented habitats and thus in conservingbiodiversity. The study of streams and waterways ingeneral is known as surface hydrology and is a core elementof environmental geography.
These are bodies of flowing water moving in onedirection. Streams and rivers can be found everywhere—they get their starts at headwaters, which may be springs,snowmelt or even lakes, and then travel all the way to theirmouths, usually another water channel or the ocean. Thecharacteristics of a river or stream change during thejourney from the source to the mouth. The temperature iscooler at the source than it is at the mouth. The water isalso clearer, has higher oxygen levels, and freshwater fishsuch as trout and heterotrophs can be found there.Towards the middle part of the stream/river, the widthincreases, as does species diversity—numerous aquaticgreen plants and algae can be found. Toward the mouth ofthe river/stream, the water becomes murky from all thesediments that it has picked up upstream, decreasing theamount of light that can penetrate through the water.Since there is less light, there is less diversity of flora, andbecause of the lower oxygen levels, fish that require lessoxygen, such as catfish and carp, can be found.
RIVER A river is a natural watercourse, usuallyfreshwater, flowing towards an ocean, a lake, a sea, oranother river. In a few cases, a river simply flows intothe ground or dries up completely before reachinganother body of water. Small rivers may also be calledby several other names, includingstream, creek, brook, rivulet, run, tributary and rill.There are no official definitions for genericterms, such as river, as applied to geographicfeatures, although in some countries or communitiesa stream may be defined by its size. Many names forsmall rivers are specific to geographic location; oneexample is "burn" in Scotland and northeast England.Sometimes a river is said to be larger than acreek, but this is not always the case, because ofvagueness in the language.
Rivers are part of the hydrological cycle.Water within a river is generally collected fromprecipitation through a drainage basin fromsurface runoff and other sources such asgroundwater recharge, springs, and the release ofstored water in natural ice and snowpacks (e.g.,from glaciers). Potamology is the scientific studyof rivers.
DAM A dam is a barrier that impounds water orunderground streams. Dams generally serve theprimary purpose of retaining water, while otherstructures such as floodgates or levees (alsoknown as dikes) are used to manage or preventwater flow into specific land regions. Hydropowerand pumped-storage hydroelectricity are oftenused in conjunction with dams to generateelectricity. A dam can also be used to collect wateror for storage of water which can be evenlydistributed between locations.
SPRING (HYDROLOGY) A spring—also known as a rising orresurgence—is a component of the hydrosphere.Specifically, it is any natural situation wherewater flows to the surface of the earth fromunderground. Thus, a spring is a site where theaquifer surface meets the ground surface.
WATER WELL A water well is an excavation or structurecreated in the ground by digging, driving, boring ordrilling to access groundwater in undergroundaquifers. The well water is drawn by an electricsubmersible pump, a trash pump, a vertical turbinepump, a handpump or a mechanical pump (e.g.from a water-pumping windmill). It can also bedrawn up using containers, such as buckets, thatare raised mechanically or by hand. Wells can vary greatly in depth, water volumeand water quality. Well water typically containsmore minerals in solution than surface water andmay require treatment to soften the water byremoving minerals such as arsenic, iron andmanganese.
SURFACE SOURCES refers to water occurring in lakes, rivers, ponds, streams, or other fresh water sources used for drinking water supplies. It is naturally replenished by precipitation and naturally lost through discharge to the oceans, evaporation, evapotranspiration and sub-surface seepage.
These also pertains to the sources in which the water flows over the surface of the earth and is directly available as raw water like what is mentioned in the previous slide.
The surface water that goes deeper into the earth enhances the groundwater safe deposits , though on the other hand it contains more salt and energy is required to take it out.
Image of the entire surface water flow of the Alapaha River nearJennings, Florida going into a sinkhole leading to the FloridanAquifer groundwater
Potrerillos DamTrinity Dam
Grand Coulee Dam Arch DamTrinity Dam
Thomson Dam Evretou DamTrinity Dam
Water resources are sources of water that are usefulor potentially useful. Uses of water includeagricultural, industrial, household, recreational andenvironmental activities. Virtually all of these human usesrequire fresh water.
WATER RESOURCES 97% of the water on the Earth is salt water. However, only three percent is fresh water; slightly over two thirds of this is frozen in glaciers and polar ice caps. The remaining unfrozen freshwater is found mainly as groundwater, with only a small fraction present above ground or in the air.
WATER RESOURCESThe sources of Surface Sources water which Ponds and Lakes can be Streams and Rivers harnessed Storage Resources ( Dams) economicallycan be divided Subsurface or Underground into the Sourcesfollowing two Springs categories: Wells
Surface Water Surface water is water in a river, lake or fresh water wetland. Surface water is naturally replenished by precipitation and naturally lost through discharge to the oceans, evaporation, evapotranspiration and sub- surface seepage.
Ponds A pond is a body of water shallow enough to support rooted plants. Many times plants grow all the way across a shallow pond. Water temperature is fairly even from top to bottom and changes with air temperature. There is little wave action and the bottom is usually covered with mud. Plants can, and often do, grow along the pond edge. The amount of dissolved oxygen may vary greatly during a day. In really cold places, the entire pond can freeze solid.
Lakes A lake is bigger than a pond, and is too deep to support rooted plants except near the shore. Some lakes are big enough for waves to be produced. Water temperatures in lakes during summer months is not uniform from top to bottom. Three distinct layers develop: The top layer stays warm at around 65–75 degrees F (18.8–24.5 degrees C). The middle layer drops dramatically, usually to 45–65 degrees F (7.4–18.8 degrees C). The bottom layer is the coldest, staying at around 39–45 degrees F (4.0–7.4 degrees C). Since light does not penetrate to the bottom, photosynthesis is limited to the top layer. Because of the warmer waters and more plentiful food supply, almost all creatures spend the summer months in the upper layer.
Lakes During spring and fall the lake temperature is more uniform. Fish and other animals are found throughout the layers of the lake. Even in cold climates, most lakes are large enough so that they dont freeze solid, unlike ponds. During the winter months some creatures hibernate in the bottom mud. Some fish continue to feed, but less actively. A layer of ice can develop on the top of lakes during winter. The ice blocks out sunlight and can prevent photosynthesis. Without photosynthesis, oxygen levels drop and some plants and animals may die. This is called "winterkill."
Streams and Rivers Rivers come in lots of different shapes and sizes, but they all have some things in common. All rivers and streams start at some high point. The high point can be a mountain, hill or other elevated area. Water from some source like a spring, snow melt or a lake starts at this high point and begins to flow down to lower points. As the water flows down, it may pick up more water from other small streams, springs or or from rain or snow melt. These streams may slowly join together to form a larger stream or river. Small rivers and streams may join together to become larger rivers. Eventually all this water from rivers and streams will run into the ocean or an inland body of water like a lake.
Streams and Rivers Although river water makes up only about 0.2 percent of all the fresh water on Earth, it plays a very important role. Rivers are like roads. They carry water, organisms and important gases and nutrients to many areas. They also help drain rainwater and provide habitats for many species of plants and animals. As they make their way to the sea, rivers help shape the features of the Earth. Rivers are travel routes for people and provide the power for hydroelectric plants.
Streams and Rivers
Storage Resources ( Dams) A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or prevent water flow into specific land regions. Hydropower and pumped- storage hydroelectricity are often used in conjunction with dams to generate electricity. A dam can also be used to collect water or for storage of water which can be evenly distributed between locations.
Storage Resources ( Dams)
Subsurface or Underground Sources Sub-surface water, or groundwater, is fresh water located in the pore space of soil and rocks. It is also water that is flowing within aquifers below the water table. Sometimes it is useful to make a distinction between sub- surface water that is closely associated with surface water and deep sub-surface water in an aquifer (sometimes called "fossil water").
Springs A spring is also known as a rising or resurgence. It is a component of the hydrosphere. Specifically, it is any natural situation where water flows to the surface of the earth from underground. Thus, a spring is a site where the aquifer surface meets the ground surface.
Wells A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater in underground aquifers. The well water is drawn by an electric submersible pump, a trash pump, a vertical turbine pump, a handpump or a mechanical pump (e.g. from a water-pumping windmill). It can also be drawn up using containers, such as buckets, that are raised mechanically or by hand. Wells can vary greatly in depth, water volume and water quality. Well water typically contains more minerals in solution than surface water and may require treatment to soften the water by removing minerals such as arsenic, iron and manganese.
Water Supply Schemes
scheme• means a system to draw water from suitable source, treat it and then supply it to the consumers
The underground water is generally pure (from suspended impurities point of view because of natural filtration) but contains more dissolved salts.The lifting of water (pumping out from wells) also requires energy (electricity) whereas the filtration of surface water is a costly affair.So the environmental engineers in the public health engineering departments (water works) make schemes(plans) to supply potable (fit for drinking from all points of view, i.e. clarity, dissolved salts, and free from bacteria etc.) water to the consumers
Types of Water Supply Schemes• rural water • Urban water supply supply schemes schemes
Aspects to be Considered• surety of availability of water• quality of water• cost of treatment• cost of supply
Traditional Source scheme• traditional source of the water supply already existing in the village like an open well or the pond is electrified and pumping machinery is installed• The pumped water is distributed to the villager’s byte existing small tanks near the wells. After commissioning the scheme it was handed over to the villagers to run at their own cost• But the schemes were not run by them successfully due to lack of interest and money.
Pump and Tank Schemes• In these schemes the government public health departments develop a source in the village itself. It may be an open well or a tube-well generally. One ground level reservoir (G.L.R.) is constructed and the pump installed on the source fills water in this tank. Public stand posts (P.S.Ps) are constructed by the sides of this GLR and public is allowed to fetch water from here free of cost-free but no hose connections are given.
Pump and Tank Schemes
Regional Water Supply Schemes• this is a combined scheme of many villages• Pipe lines have to be laid to carry water from the source to the benefited villages. So it is a costlier option.• Some times connections to individual houses are also given depending upon the population and the paying capacity and willingness of the consumers. There are some regional water supply schemes which cater the needs of hundreds of villages along with the urban towns
Regional Water Supply Schemes
Piped Water Supply Schemes• These are generally for towns or big villages (urban areas).• In these schemes house connections are given and the consumption is charged. The source may be in the locality or a distance source.• Overhead tanks known as elevated service reservoirs (E.S.R) are constructed for the distribution of water through the distribution mains.
Piped Water Supply Schemes
• First of all the raw water is treated by all means including disinfection (most important).Then pumped to ESRs and then distributed either for the whole day or at certain fixed time.• The consumption is generally metered and charged on monthly basis. After some years the existing water supply schemes are reframed and executed.• Such schemes are known as Reorganized Water Supply Schemes.
Urban Water Supply Schemes• These are the schemes implemented for the urban areas.• The main difference in design of rural and urban water supply scheme is the rate of water supply.• . The other main difference is the house connections.
• In most of the rural water supply schemes water is supplied at a common point and people have to fetch it from this common place also known as public stand post.• In urban water supply schemes every house is given a metered or flat rate service connection through which water is generally supplied intermittently.
• The water obtained from a surface or ground source is treated and lifted in an elevated service reservoir. Then it is distributed through properly designed and maintained distribution system. Though some of it is wasted in leakages but the loss should not be more than 10%. The water is also supplied for industrial and commercial purposes. Some of the water is always stored for fire fighting.
Urban Water Supply Schemes
PHYSICAL AND CHEMICALSTANDARDS OF WATER
Safe drinking water• Free from pathogenic organisms• Clear• Not saline• Free from offensive taste or smell• Free from compounds that may have adverse effect on human health• Free from chemicals that cause corrosion of water supply systems
Coliform (bacteria, as the indicatororganism) count in any sample of 100mLshould be zeroSample of water that does not conform tothis standard calls for an immediateinvestigation into both the efficacy of thepurification process and the method ofsampling.
Criteria of water in the distribution system• E. Coli(Escherichia Coli, bacteria found in the colon of human beings as natural habitant) count in 100ml of any sample should be zero• Coliform organisms, not more than 10 per 100ml shall be present in any amount• Coliform organisms should not be detectable in 100ml of any two consecutive sample or more than 55 of the samples collected per year
Individual or small community supplies• E. Coli count should be zero in any sample of 100mL and coliform organisms should not be more than 3 per 100ml.• If it exceeds the said amount, the supply shoul be disinfected
Virological Standards0.5 mg/L of free chlorine residual for an hour• Sufficient to inactivate virus even in water that was originally polluted• Insisted in all disinfected supplies in areas suspected of infectious hepatitis Jaundice• Other areas insists of 0.2mg/L of this free residual for half an hour
9. What are the toxicological materials found in water?
•Total coliform bacteria Total coliform bacteria are commonly found in the environment (e.g., soil or vegetation) and are generally harmless. If only total coliform bacteria are detected in drinking water, the source is probably environmental. Fecal contamination is not likely. However, if environmental contamination can enter the system, there may also be a way for pathogens to enter the system. Therefore, it is important to find the source and resolve the problem.
• E. Coli E. coli is a type of fecal coliform bacteria commonly found in the intestines of animals and humans. E. coli is short for Escherichia coli. The presence of E. coli in water is a strong indication of recent sewage or animal waste contamination. Sewage may contain many types of disease-causing organisms.
• Fecal coliform bacteria Fecal coliform bacteria are a sub-group of total coliform bacteria. They appear in great quantities in the intestines and feces of people and animals. The presence of fecal coliform in a drinking water sample often indicates recent fecal contamination, meaning that there is a greater risk that pathogens are present than if only total coliform bacteria is detected.
PHYSICAL CHARACTERISTICS OF WATERTemperature It can be measured by athermometer. The temperatureshould be suitable for human beingsdepending on climatic and weatherconditions. An average temperature is15 degree Celsius.
Turbidity The muddy or cloudy appearance of such particles that presents hindrances on path of light. The turbidity is measured by a turbidity rod or a turbidity meter with physical observations and is expressed as the suspended matter in mg/I or ppm (part per million). The standard unit of turbidity is that which is produced by 1 mg of finely divided silica in one litre of distilled water.
Colour It is imparted by dissolved organic matters from decaying vegetation or some inorganic materials. The presence of algae or other aquatic plants in water may impart colour changes. The standard unit of colour is that which produced by one milligram of platinum cobalt dissolved in one litre of distilled water. It is measured by lab`s by Nessler`s tubes by comparing the sample with the known intensities. The instrument used is TINTOMETER.
Taste and odour The dissolved inorganic salts or organic matter or the dissolved gases may impart taste and odour to the water. The water must not contain any undesirable or objectionable taste or odour. The extent of taste or odour is measured by the term called odour intensity which is related with the threshold odour, which represents the dilution ratio at which the odour is hardly detectible. The water to be tasted is gradually diluted with odour free water and the mixture at which the detection of taste and odour is just lost is determined. The number of times the sample is diluted is known as the threshold number. Thus if 20 ml of water is made 100ml (until it just losses its odour and tastes) then the threshold number is 5. For domestic water supplies the water should be free from any taste and odour so the threshold number should be 1 and not to exceed to 3.
Specific conductivity of water It is determined by means of a portable diionic water tester and is expressed as micro ohms per cm at 25 degree Celsius. Mho is the unit of conductivity and is equal to 1 ampere / 1 volt . The specific conductivity is multiplied by a co-efficient (generally 0.65) so a to directly obtain the dissolved salt content in ppm.
Chemical Characteristics of water
• Since water is such a good solvent, it is not surprising to find many different chemical substances present in it. Water, on reaching a river, will contain inorganic and organic compounds which were dissolved as rainwater percolated through the soil and rocks. In addition, some gases will dissolve in rainwater during its passage through the air.• Analysis of water is done to determine this chemical characteristics.
Total solids and Suspended solids• The total amount of solids can be determined by evaporating a measured sample of water and weighing the dry residue left.• The suspended solids can be determined by filtering the water sample and weighing the residue left on the filter paper.• The difference between the total solids and the suspended solids will be the dissolved solids.
pH of Water• pH is equal to the negative logarithm of hydrogen ion. The higher value of pH means lower value hydrogen ion concentrations and thus represent alkaline water and vice versa.• The neutral water has the same number of H+ and OH- ions.• If an acid is added to neutral water the number of hydrogen ion and thus reduces pH. Similarly, if an alkali is added the number of hydroxyl ion increases thus reducing hydrogen ion and the pH increases.
• Hence, if the pH of water is more than 7 it is alkaline and if it’s less than 7 it is acidic.• Generally, the alkalinity of water is caused by the presence of bicarbonates of calcium & magnesium, or by the carbonates, or the hydroxides of Na, K, Ca, and Mg.• Acidity is caused by the presence of mineral acids, free CO2 sulfates of Fe and Al etc.
• For municipal water supplies the pH should be close to 7 as possible. The lower pH may damage the pipelines etc. by reacting with them. The alkaline water may produce sedimentation in pipes, difficulties in chlorination and adverse effect on human physiological system.
Hardness of Water• Hardness in water prevents the formation of sufficient foam when used with soap.• Hardness in water is mainly due to the presence of ions of the metals calcium (Ca2+), magnesium (Mg2+), and iron (Fe2+). Rivers and lakes fed by water that has run from chalky areas and limestone (CaCO3) contain an abundance of calcium. Calcium and magnesium account for at least 70% of the total cations in water.
• Hardness is measured by titration method and is expressed in ppm or mg/l. Generally the underground water is harder as it dissolves the salts in its journey form surface to the ground water table. For boiler feed waters and for efficient washing of clothes the water must be soft, i.e. hardness should be less than 75ppm.
Chlorides• Chlorides are generally present in water in the form of sodium chloride and their concentration above 250mg/l produces a salty taste in drinking water. The chlorides can be measured in water by titrating the water with standard silver nitrate solution using potassium chormate as indicator.
Nitrogen Content• Nitrogen in water may occur in one or more of the following: – Free Ammonia • Indicates a very fast stage of decomposition of organic matter. – Albuminoid Nitrogen • Represents the quantity of nitrogen present in water before the decomposition of organic matter has started.
Metals• Various metals in minerals may be present in water like Fe, Mn, Cu, Pb, Cd, As, Se, etc. The allowable limits
Dissolved Gasses• Various gases like CO2, O2, N2, H2S and CH4 etc. may be present in dissolved form in water. • H2S even in small concentration gives bad taste and odor. • CO2 indicates biological activity. • O2 is generally absorbed by water from the atmosphere• Organic matter may be present in water due to the disposal of waste water in it. • Organic matter has the tendency to become inorganic matter known as decomposition of organic matter and the process is bio-chemical
Bio Chemical Oxygen Demand(BOD) – Demand of oxygen imposed by the aerobic bacteria – This reduces the dissolved oxygen content of water. So if the dissolved oxygen of water is found to be less than the concentration it indicates water pollution.• The BOD of water should be zero.
Treatment of Water
The available raw water has to be treated to makeit fit, i.e. potable, means safe for human consumption. Itshould satisfy the physical, chemical, and bacteriologicalstandards. The various methods of water purification are:Screening Plain sedimentationSedimentation aided with coagulationFiltrationDisinfectionAerationSofteningMiscellaneous treatments likedefluoridation, recarbonation, desalination, etc.
S creening Screens are provided before the intake works so asto prevent the entry of big objects like debris, branches oftrees, parts of animals etc. Screens may be of twotypes, coarse screen and fine screens. Coarse screen areparallel iron rods placed vertically or at a slope at about 2.5cm to 10 cm apart. The fine screens are made up of finewire or perforated metal with small openings less than 1 cmin size. Finer is the screen more are the chances of cloggingso generally only coarse screens are used. The screens maybe manually cleaned or mechanically cleaned dependingupon the requirement i.e. the size of the treatment plant.
P S lain edimentation Sedimentation is done to remove the impurities whichhave specific gravity more than that of the water and aresettleable. When water is moving these impurities remain insuspension due to the turbulence and as the velocity is reducedthey settle down. It is not necessary to stop the motion of watercompletely as it will require more volume of the sedimentationtanks. As per the theory of sedimentation the settlement of aparticle depend upon the velocity of flow, the velocity of water,the size shape and specific gravity of particle. The settlingvelocity of a spherical particle is expressed by Stroke’s law.
S edimentation aided with C oagulation The fine suspended particles like mud particles and thecolloidal matter present in the water cannot settle down by plainsedimentation with ordinary (lesser) detention periods. Some ofthe colloidal impurities will not settle even if the water is detainedfor long periods in the sedimentation tanks as the same charge onthe clay particles repel each other and do not allow them to settledown. So the sedimentation is aided with coagulation. Coagulationis a process in which some chemical like alum or ferrous sulfate ismixed in water resulting in particle destabilization. Operationallythis is achieved by the addition of appropriate chemical like alumand intense mixing for achieving uniform dispersion of thechemical. These chemicals are more effective when the water isslightly alkaline .
Sometimes sodium carbonate or lime is to be added toachieve the suitable pH of water. Flocculation is the stage ofthe formation of settleable particles (or flocs) fromdestabilized (neutral) colloidal particles and is achieved bygentle (slow) mixing. So in flocculation the alum is firstmixed rapidly for dispersion and then slow mixing producesflocs. Both these stages of flocculation are greatly influencedby physical and chemical forces such as electrical charge onparticles, exchange capacity, particle size andconcentration, pH, water temperature, and electrolyteconcentration.
F iltration Filtration is the physical and chemical process forseparating suspended and colloidal impurities from waterby passage through a porous bed made up of gravel andsand etc. Actually the sedimentation even aided withcoagulation and flocculation cannot remove all thesuspended and colloidal impurities and to make water(specifically surface water) fit for drinking, thus filtration isa must. The theory of filtration includes the followingactions:
1.) M echanical S training The suspended particles present in water that are biggerin size than the voids in the sand layers are retained their and thewater becomes free of them. The sand layer may get chokedafter some time and then it is to be cleaned for further action bywashing it back.2.) S edimentation The small voids in the sand act as tiny sedimentationtanks and the colloidal matter arrested in these voids is agelatinous mass and thus attracts other finer particles. Thesefiner particles are thus removed by sedimentation.
3.) Biological Metabolism Certain microorganisms are present in the sand voids.They decompose the organic matter like the algae etc. and thusremove some of the impurity.4.) E lectrolyte C hange According to the theory of ionization, a filter helps inpurifying the water by changing the chemical characteristics ofwater. The sand grains of the filter media and the impurities inwater carry electrical charge of opposite nature whichneutralizes each other and forces the particles to settle now bygravity.
D isinfection The filtration of water removes the suspendedimpurities and removes a large percentage of bacteriabut still some remain there in the filtered water. Thesebacteria may be harmful (pathogenic bacteria). Theprocess of killing these bacteria is known asdisinfection. There are many diseases like cholera,gastro entities, infectious hepatitis, typhoid etc., thebacteria or virus of which transmits through water. It isnecessary to make water free from any micro-organismbefore human consumption.
Contamination (mixing of pathogenic micro-organism) maytake place in the water supply at any time (because of leakage etc.)so proper measures must be taken to stop it at all levels. Generallythe disinfection is done by adding chlorine to water. There should bea residual amount of chlorine after the disinfection to fight with anyprobable contamination in the route of water to the consumer.S M ome ethods of D isinfection:•Boiling of water•Treatment with excess lime•Use of ozone•Treatment with ultraviolet rays•Use of potassium permanganate•Treatment with silver•Use of bromine, iodine and chlorine
Criteria for a Good Disinfectant•It should be capable of destroying the pathogenic organisms present, within the contact time•Available and not unduly influenced by the range of physical and chemical properties of water encountered particularly temperature, pH and mineral constituents.•It should not leave products of reaction which render the water toxic or impart colour or otherwise make it unpotable.•It should have ready and dependable availability at reasonable cost permitting convenient, safe and accurate application to water.•It should possess the property of leaving residual concentrations to deal with small possible recontamination.•It should be amenable to detection by practical, rapid and simple analytical techniques in the small concentration ranges to permit the control of efficiency of the disinfection process.
F actors A ffecting E fficiency of D isinfection•Type, condition and concentration of organisms to be destroyed•Type and concentration of disinfectant•Contact time and concentration of disinfectants in water and•Chemical and physical characteristics of water to be treated particularly the temperature, ph and mineral constituents. Potable water should always have some amount ofresidual chlorine, as there are all chances of contamination at alllevels. This may be 0.2 ppm. to 0.3 ppm. Depending upon therequirement (rainy season or enhance chances, more CL2required). To make sure the presence of chlorine some tests aredone out of which Orthotolodine test is the most common one.
O rthotoIodine T est: In this test 10 ml of chlorinated sample of water is takenafter the required contact period (say half an hour) in a glasstube. 0.1 ml of orthotoIodine solution is added to it. The colorformed is noted after 5 minutes and compare with the standardcolored glasses. Darker is the yellow color formed more is theresidual chlorine. The test is very simple and even a semi-skilledemployee can perform it satisfactorily and it can be done at thesite itself and accordingly corrective measures can be taken. Forexample if there is a complaint from a hostel mess. Test isperformed for the tank water and if no residual chlorine is found,bleaching powder (a good source of chlorine) is mixed withsome water and added to the tank water is paste form and stirred.The test is again performed after half an hour till it shows therequired residual chlorine.
A eration Taste and odor, both are undesirable in water. Aeration isdone to remove taste and odor. Aeration is done to promote theexchange of gases between the water and the atmosphere.P urpose:•To add oxygen to water for imparting freshness, for example water from underground sources may have lesser oxygen.•For expulsion of carbon dioxide, hydrogen sulfide and other volatile substances causing taste and odor.•To precipitate impurities like iron and manganese especially from underground water.
In aeration gases are dissolved in or liberated fromwater until the concentration of the gas in the water hasreached its saturation value. The concentration of gases inthe liquid generally obeys Henery’s law which states thatthe concentration of each gas in water is directlyproportional to the partial pressure (product of the volumepercentage of the gas and the total pressure of theatmosphere.) or concentration of gas in the atmosphere incontact with water. The saturation concentration of a gasdecreases with temperature and dissolved salt in water.Aeration accelerates the exchange of gas.
To ensure proper aeration, it is necessary to:•Increase the area of water in contact with the air. The smaller are the droplets produced, the larger will be the area available.•Keep the surface of the liquid constantly agitated so as to reduce the thickness of the liquid film which would govern the resistance offered to the rate of exchange of the gas.•Increase the time of contact of water droplets with the air or increase the time of flow which can be achieved by increasing the height of jet in spray aerators and increasing the height of the tower in case of packed media. Where oxygen is to be dissolved in water, the concentrationor partial pressure of the oxygen may be increased by increasing thetotal pressure of the gas in contact with water. For this purpose airinjected into a main under pressure is a reasonably efficient methodof increasing the amount of dissolved oxygen.
W S ater oftening The reduction or removal of hardness from water is calledwater softening. For domestic water supplies, the softening isdone to reduce the soap consumption, to ensure longer life towashed fabric, to lower the cost of maintaining plumbing fixturesand to improve the taste of food preparations and improvepalatability. For industrial supplies, softening is one for reducingscale problems in boilers and the interference in the working ofdyeing systems. Usually a total hardness of 75 to 100 mg/Lwould meet these requirements. The magnesium hardness shouldnot exceed 40 mg/L to minimize the possibility of magnesiumhydroxide scale in domestic water heaters.
Calcium and magnesium associated withbicarbonates are responsible for carbonates hardness andthat with the sulfates, chlorides and nitrates contribute tonon carbonate hardness. Normally the alkalinity measuresthe carbonate hardness unless it contains sodium alkalinity.The non carbonate hardness is measured by the differencebetween the total hardness and the carbonate hardness.Carbonate and bicarbonates of sodium are described asnegative non carbonate hardness.
Water Softening Processes
• The reduction or removal of hardness from water is called as water softening. For the domestic water supplies the softening is done to reduce the soap consumption, to ensure longer life, to wash fabric, to lower the cost of maintaining plumbing fixtures and to improve the taste of food preparation and improve the palatability (good taste). For industrial supplies, softening is done for reducing scaling problems in boilers and the interference in the working of dyeing systems.
Origin of water "hardness"1. Carbon dioxide reacts with water to form carbonic acid which at ordinary environmental pH exists mostly as bicarbonate ion2. Microscopic marine organisms take this up as carbonate to form calcite skeletons which, over millions of years, have built up extensive limestone deposits. Groundwaters, made slightly acidic by CO2 (both that absorbed from the air and from the respiration of soil bacteria) dissolve the limestone .3. Thereby acquiring calcium and bicarbonate ions and becoming "hard". If the HCO3– concentration is sufficiently great, the combination of processes and4. causes calcium carbonate ("lime scale") to precipitate out on surfaces such as the insides of pipes. (Calcium bicarbonate itself does not form a solid, but always precipitates as CaCO3.)
ProcessesConventional water softeningMost conventional water-softening devicesdepend on a process known as ion-exchange in which "hardness" ions trade places with sodium and chloride ions that are loosely bound to an ion- exchange resin or a zeolite (many zeolite minerals occur in nature, but specialized ones are often made artificially.)Magnetic water softening and scale controlThere is a long history of the promotion of magnets to alleviate the "hardness" of mineral-containing waters, and particularly to control the deposition of scale in teapots, plumbing systems, evaporators, and boilers. There are now a large variety of devices on the market that claim to reduce scale deposition, and some claim to "soften" the water as well. The earlier devices mostly employed permanent magnets, but many now use alternating magnetic or electrostatic fields. The magnetic field surrounds the pipe at some point and penetrates it from all sides. This obviously limits its use to non-ferrous pipes such as copper or plastic.
Catalysts cannot soften waterMany groundwaters are supersaturated in hardness ions, and it is conceivable that a suitable catalyst could cause this escess material to precipitate out. But even if the solid carbonates were filtered out, the remaining water would be saturated and capable of forming scale on heat exchanger surfaces and leaving evaporative deposits in teakettles and on surfaces. It would also react with soaps to produce scums in laundry and bathtubs.
Question # 16 What is the requirement ofpressure of water to be supplied to the residences?
Landscape requirements• A requirement of the design process is to produce a landscape survey of the proposed area of construction to assess the effect of the project on shrubs and trees. Trees to be retained should be identified, marked and methods of protection determined. Vegetation such as mature trees and other natural habitat for fauna shall not be removed unnecessarily.• Backfilling of trenches shall be arranged to provide topsoil at the surface of the trench, and shall be such that no depressions are left along pipe alignments after settlement of the soil. Special care is required in restoration of highly visible sites and existing pavements.
Pipe deflection• Deviation of a pipeline around an obstruction can be achieved by deflection at pipe joints or in combination with bends or connectors. The deflection angle permitted at a flexible joint shall be in accordance with the manufacturers recommendation. For laying PVC or PE pipes on curves, minimum radii are to be as per manufacturers recommendations. If deflection of joints does not provide the necessary deviation, bends and other fittings shall be employed.
Pipelines in easements• Water mains that are located anywhere other than in the road reserve of a dedicated public road shall be located within an appropriately sized water supply easement subject to ACTEWs approval.
Locating buried mains• Tracer wire shall be used for all non-metallic water mains for the purpose of locating buried mains (by passing a signal through the wire, which can then be picked up by the detector). PVC coated copper wire (1mm) shall be taped to the non-metallic main in a continuous length. At every hydrant, sufficient slack shall be left to enable the wire to be brought up to the surface within each hydrant surround, wound three times around, and taped to the hydrant immediately below the hydrant head.• Marking tape to AS 2648 shall be laid in a continuous length on top of the pipe embedment material, 150mm above all water mains.
Water supply master plan• The design of the water reticulation network including pipe layout and sizes, fire risk categories, zone boundaries, and valving to meet breakdown requirements shall be shown on a Water Supply Master Plan
System reliability• All elements of ACTEWs water supply system should be planned and detailed to ensure as high a level of reliability as is reasonable. Features incorporated into a system layout to enhance reliability include the following:• for critical mechanical equipment, a standby capacity sufficient enough to maintain full capacity with any one element out of service;• for distribution systems downstream of reservoirs, a looped rather than branched layout is generally used to provide more than one supply route on distribution systems. Valving is arranged as described in Clause 5.4. These valving arrangements help to limit the area needing to be shut down when isolating and repairing any section of main;
• for all reservoirs, either duplicate tanks or pressure regulated bypass arrangements to maintain a rate of supply to the distribution system equivalent to at least the design bulk supply rate (if the reservoir is out of service);• emergency storage in reservoirs, which in addition to providing a reserve for fire fighting, can be used to maintain a distribution supply for limited periods during bulk supply interruptions. Inter-zone connections or other arrangements can usually be made to maintain some supply. In some extreme cases, it may be necessary to contact consumers and request sparing the use of water until repairs can be completed. The limited periods referred to above, for maintaining supply, range from a few hours during prolonged high demand (in summer) to a few days during low demands in winter.
Pressure requirements• Maximum pressures• Pressure zoning is arranged wherever possible to limit the maximum static pressure at any point to 75 metres head. In special cases this is relaxed to 90 metres head.• There are two areas within the ACT where maximum static heads over 100 metres currently exist:• the Woden town centre area below contour 587 metres AHD could experience a maximum static head in excess of 100 metres up to 107 metres;• the North Canberra area, which comprises the City, Acton, Braddon, Turner, Reid, Lyneham, Dickson and Downer below contour 575 metres AHD, could experience a maximum static head in excess of 100 metres and up to 115 metres.• All pipework shall be designed for the field test pressure as defined in Clause 3.5.4, for the following reasons:• to allow for the use of inter-zone connections during emergencies;• to allow for waterhammer;• to allow for standardisation of equipment and flexibility of use.
• for domestic development exceeding two stories and for shopping, commercial and industrial: the equivalent of 30 metres head over the highest point on the block.• For very large blocks such as institutional campuses, an extra allowance of 5 metres head for every 1000 metres distance, between the main and the most critical point on the block (with regard to either elevation or distance from the main), is permitted.• Stated residuals are to be achieved with service reservoirs at half capacity and an allowance for reservoir outlet losses of 1.5 metres. The system should be checked to ensure that the same residuals can be achieved at 50% peak hour demands with any one element out of service.
Pipe roughness• Reticulation mains are to be sized to provide the minimum heads (specified above) using the Colebrook-White equation. A pipe roughness value (k) of 0.3mm averaged over the life of the main is to be used when no allowance is made for valves and fittings. A pipe roughness value (k) of 0.15mm should be used if specific allowances have been made for valves and fittings.
Design velocity• Ideally, the velocity in water mains should range between 0.5m/s and 2.0m/s. However, under extreme conditions (e.g. fire flows in high fire risk areas) velocities up to 5m/s are acceptable. Very low velocities in pipes cause water quality problems due to long detention times and should be avoided if possible. Minimum diameters and lengths of main should be constructed consistent with meeting the required demands on the network. Generally, dead end mains with tapered diameters below DN100 should be used in cul-de- sacs.
General detailing requirements for pipelines• As mentioned in the introduction, there is a demonstrated need to construct systems in a standard configuration using tried and proven methods and materials. Within the ACT, any deviation from normal practice has the propensity to increase stock holdings for spare parts, and create additional maintenance costs by way of labour charges. Any deviation from standard practice will require the specific approval of ACTEW. A submission detailing the proposals, in full, must be made to include an economic and long term benefit analysis, and the covering life cycle costs. The costs of burst mains can quickly erode cost differentials of the initial costs in pipe networks. Unless otherwise noted, the current version ofAustralian Standards shall apply.
Valve size• The nominal size of a valve may be reduced below the nominal size of a pipe line providing the reduction in size does not significantly reduce the hydraulic capacity of the main. Such intentions must be identified at the Design Submission stage of the works.
Scour outlets• On water mains without hydrants (e.g. generally bulk supply mains), scour (or drain) outlets, with isolating valve control, shall be provided at all low points. Wherever possible, on water mains with hydrants (e.g. reticulation), a hydrant should be located at or near all low points.• Scour outlets should also be provided on bulk supply mains to assist in the draining of each section of main between sectioning valves.• For larger mains, the size of the scour should be determined after considering (1) the length of time available for draining the pipe section, and (2) the facilities available to dispose of the flow.
Water supply services• For new leases and in the redevelopment of existing leases water supply services shall be installed by developers of municipal works. The service shall terminate just inside the front property boundary.
Aeration is used to treat tastes and odors, to help removeminerals such as iron and manganese from water, and toremove carbon dioxide from the water.In general, aeration is more commonly used when treatingroundwater than when treating surface water. Surfacewater has typically run through creeks and rivers, aeratinthe water before it reaches the treatment plant.
How Does Aeration Work? Aeration is the intimate exposure of water and air. It is away of thoroughly mixing the air and water so thatvarious reactions can occur between the components ofthe air and the components of the water.
Fig. 1 –The Process of Aeration
Two methods of aeration 1. Scrubbing action2. Oxidation
Why aeration is done?The goal of an aerator is to increase thesurface area of water coming in contact withairso that more air can react with the water. Asair or water is broken up into smallerdrops/bubbles or into thin sheets, the samevolume of either substance has a largersurface area.
Water softening is the reduction of the concentration of calcium, magnesium, and certain other metal cations in hard water. These "hardness ions" can cause a variety of undesired effects including interfering with the action of soaps, the build up of limescale, which can foul plumbing, and galvanic corrosion. Conventional water-softening appliances intended for household use depend on an ion- exchange resin in which hardness ions are exchanged for sodium ions. Water softening may be desirable where the source of water is hard. However, hard water also conveys some benefits to health by reducing the solubility of potentially toxic metal ions such as lead and copper.
Water softening methods mainly rely on the removal of Ca2+ and Mg2+ from a solution or the sequestration of these ions, i.e. binding them to a molecule that removes their ability to form scale or interfere with soaps. Removal is achieved by ion exchange and by precipitation methods. Sequestration entails the addition of chemical compounds called sequestration (or chelating) agents. Since Ca2+ and Mg2+ exist as nonvolatile salts, theycan be removed by distilling the water, but distillationis too expensive in most cases (rainwater is softbecause it is, in effect, distilled.)
Effects of sodiumFor people on a low-sodium diet, the increase insodium levels (for systems releasinwater. Forexample:A person who drinks two litres (2L) ofsoftened, extremely hard water (assume 30 gpg)will consume about 480 mg more sodium (2L x30 gpg x 8 mg/L/gpg = 480 mg), than ifunsoftened water is consumed.This amount is significant.g sodium) in the water can besignificant, especially when treating very hard
This amount is significant. The American HeartAssociation (AHA) suggests that the 3 percent of thepopulation who must follow a severe, salt-restricted dietshould not consume more than 400 mg of sodium a day.AHA suggests that no more than 10 percent of this sodiumintake should come from water. The EPA’s draft guideline of20 mg/L for water protects people who are mostsusceptible. Most people who are concerned with the addedsodium in water generally have one tap in the house thatbypasses the softener, or have a reverse osmosis unitinstalled for the drinking water and cooking water, whichwas designed for desalinisation of sea water. Potassiumchloride can also be used instead of sodiumchloride, which would have the added benefit of helping tolower blood pressure, although costly. However, elevatedpotassium levels are dangerous for people with impairedkidney function: it can lead to complications such ascardiac arrhythmia.
Various Methods of Water Softening Ion exchange water softener Softening water through magnetsWater softening is a process in which a plant reducesmagnesium, calcium and ion concentration from the hardwater. On an average, hard water contains about 90 pounds ofdissolved rocks. It can pose hazards to human health.Hardness of water can damage hair in a man and makeswater less safe for drinking.The rocks which get dissolved in water mixes magnesiumand calcium ions in pipes and heats the surface ofdishwashers and washing machines. Water hardness alsomakes soap less effective.
Ion Exchange Water Softener Ion exchange water softener depends on two tanks- the brine and resin tanks. This process removes magnesium and calcium ions. Potentially hard water will pass through the resin beads in resin tank. When the beads become saturated with magnesium and calcium ions, the ion exchange softener goes offline. Brine tank is again filled with new sodium ions which are ready for exchange, it flushes the resin tank and then it becomes online again. This method is suitable for all appliances which uses a lot of water. This method can also increase the life span of dishes and clothes. This method is not ideal for drinking purposes because of the sodium intake.
Softening Water through Magnets It is a new method for water softening and this is the safest method for drinking purposes. This is non-chemical based water softening method. The process involves magnets placed outside or inside the water pipe and water flows through a magnetic field. Water is stripped of its hardness and impurities because of the magnetic field’s strength. It is also advised to put the magnet bars close to the water source.
What do you understand bywastewater management?
The wastewater management systemshould aim at the following achievement: Proper collection of wastewater discharged by the community. Adequate treatment of wastewater to achieve the desired effluent standards. Safe and efficient operations and as far as possible self supporting. Sound financial management.
The wastewater management hasthe main components as collection,conveyance, treatment and disposal of wastewater.
Describe the Method of Design of SewerLine along with the Hydraulics of Sewer
What is sewer? Sewer is an artificial conduit or system of conduitsused to remove sewage and to provide drainage. Sewage is the mainly liquid waste containingsome solids produced by humans which typicallyconsists of -washing water -faeces -urine -laundry waste -other material from household and industry
The objective of sewage treatment is to make the sewageharmless before it is disposed.The disposal means final laying of sewage on the land orleaving it on land to flow and mix in some body of water likethe river or a pond.The sewage has many characteristics like temperature,hydrogen ion concentration (pH), color and odor,solids, nitrogen, phosphorous, chlorides, bio-chemical oxygendemand (BOD), chemical oxygen demand (COD), and toxicmetals etc. Though all of them are important fordetermination of disposal criteria, BOD is the most importantone.The Bio-chemical oxygen demand (BOD) of sewage orpolluted water is the amount of oxygen required for thebiological decomposition of biodegradable organic matterunder aerobic conditions.
The general temperature of sewage is 20 degree celsius so it istermed as BOD5 at 20 degree C as the standard BOD. The BODsatisfaction equation is as follows, Yt = L (1-10Kd t)Where Yt = BOD at any time t L = initial BOD at time t = 0 Kd = deoxygenation co-efficient (function of temperature) KdT = Kd20 × 1.047 T–20 T = temperature of the reaction Kd20 = 0.1 per day (for normal sewage).So the BOD5 determines the strength of the sewage. Higher is theBOD5 stronger is the sewage. The average value of domesticsewage is 300 parts per million (ppm) or mg/liter.
In the 20th century developed world, Sewersare usually pipelines that begin withconnecting pipes from buildings to one ormore levels of larger underground horizontalmains, which terminate at sewage treatmentfacilities. Vertical pipes, calledmanhole, connect the mains to the surface.Sewers are generally gravity powered, thoughpump may be used if necessary
Most drains have a single large exit at theirpoint of discharge (often covered by agrating to prevent access by humans andexit by debris) into either acanal, river, lake, reservoir, ocean andspread out intosmaller branches as they move up intotheir catchment area.
Sanitary sewer is a type of underground carriage system for transporting sewage from houses or industry to treatment or disposal. Sanitary lines generally consist of laterals, mains, and manholes (or other various forms of traps).
‰SEPARATESEWER SYSTEM‰COMBINED SEWER SYSTEM
A combined sewer is a type of sewersystem which provides partiallyseparated channels for sanitary sewageand Storm water runoff. This allows thesanitary sewer system to providebackup capacity for the runoff sewerwhen runoff volumes are unusuallyhigh, but it is an antiquated system thatis vulnerable to sanitary sewer overflowduring peak rainfall events.
A separate sewer system is a typeof sewer system which one pipe systemcarries wastewater and anotherseparate pipe system carries stormwater.
BIO-CHEMICAL OXYGENDEMANDBio-Chemical Oxygen demand (BOD) ofsewage or polluted water is the amount ofoxygen required for the biologicaldecomposition of biodegradable organicmatter under aerobic conditions.
• Readily decomposable organic matterlike food items, human excreta, urine,etc. is known as the putresciblematter. • The decomposition of organic matteris done by the bacteria. There aremainly two types of bacteria: 1. aerobic bacteria which work inpresence of oxygen. 2. anaerobic bacteria which workin absence of oxygen.
CHEMICAL OXYGENDEMANDThe chemical oxygen demand ofthe biodegradable and non-biodegradable organic matter.
• The COD can be readily(3-4hrs)measured in the laboratory where asthe BOD5 determination takes 5 daysin the laboratory. • The COD/BOD ratio variesgenerally from 2.0 – 2.5. • The BOD of the waste decides itsfoulness or offensiveness.
• When wastewater is disposed in theriver, it consumes the dissolved oxygenof the river water for the satisfactionof its BOD. This reduces the DissolvedOxygen(D.O) of the river water.• If the D.O goes below 4 p.p.m., almostall the fish and aquatic life shall bedestroyed.• The died fish will become organicmatter that will further decompose andthe whole of the D.O of the fresh body ofwater shall be exhausted and it willconvert into a polluted and useless bodyof water.
The Water Treatments are the process to remove the different impurities present in the raw water, to render the water safe and clean and to ensure the water treatment process and treated water quality meets the drinking water standards. The type of water treatment required depends on the characteristics of the raw water. The characteristics of the raw water is assessed by taking sample of water from the source during different seasons of the year and analyzing for physical, chemical and bacteriological quality parameters.
Water treatment involves removal of undesirable constituents from water and then disposal of them in easiest and safest manner. To achieve these goals, a variety of water treatment operation and processes are utilized, which exploit various physical and chemical phenomena to remove or reduce the undesirable constituents from the water. Those operations used in the treatment of water in which change is brought about by means of or through application of physical forces are known as Water Treatment Process unit operations . Those Process used for the Water Treatment in which is brought about by means of chemical reaction are known Unit Process.
Chemical precipitation :Enhancement of removal ofsuspended solids by chemical addition.• Coagulation in Water Treatment Process - Coagulation is the addition and rapid mixing of coagulant resulting in destabilization of the colloidal particles and formation of micro flocs.• Ion exchange in Water Treatment Process - The cations and anions in water are selectively removed when water is percolated through beds containing cation and anion exchange resins.• Aeration or Gas transfer in Water Treatment Process - Addition or removal of gases from liquid phase.• Disinfection in Water Treatment Process - Selective destruction of disease-causing organisms present in water.
Screening – it is a unit operation that removes floating and suspended larger material from water. Aeration- Aeration is the unit water treatment process for the exchange of gases between water and atmosphere. Aeration or gas transfer involves either bringing air or other gases in contact with water or to transfer volatile substances from the liquid to the gaseous phase. Coagulation and Flocculation- the unit processes to convert the stable colloidal particles into settle able flocs by destabilizing the charge on the colloids so as to remove turbidity from the water. Water with little or no turbidity will be clear. In addition to removing turbidity from the
Sedimentation – it is a unit operation to settle out the suspended particles in water by gravitational force. This is achieved by lowering the flow velocity of the water below the suspension velocity in a basin to settle out suspended particles by gravity. The process is also known as settling or clarification. Filtration - is the unit operation in Water Treatment. Filtration using a filter media to separate the suspended particles mechanically from water to render water free from turbidity. Disinfection - is the unit process employed to inactivate the disease producing bacteria present in water by addition of certain chemicals in order to render the water safe for consumption. Common disinfectant is chlorine and the process of addition of chlorine is known as chlorination. Demineralization -is the process of removing dissolved minerals and mineral salts, present in the form of mineral ions in water. This process strips out all chemical impurities present in water.
• The treatment of wastewater is a general term that applies to any operation/process that can reduce the objectionable properties of wastewater and make it less objectionable. Wastewater treatment is a combination of physical, chemical and biological processes.• Unit Operations are the methods of treatment in which the application of physical forces predominate while unit processes are those in which the chemical and biological activities are involved. The aim of wastewater treatment works is to produce an acceptable effluent through the available unit operations. Generally the wastewater treatment processes bring about changes in concentration of a specific substance by moving it either into or out of the wastewater itself. This is known as the phase transfer. The main phase transfers are as follows,
• Gas transfer : aeration • Centrifuging • Chemical conditioning• Ion transfer • Biological floatation • Chemical coagulation • Vacuum filtration • Chemical precipitation • Sludge digestion • Ion exchange • Incineration • Adsorption • Wet combustion• Solute stabilization • Chlorination • Liming • Recarbonation • Break point and super chlorination• Solid transfer • Straining • Sedimentation • Floatation • Filtration• Nutrient transfer• Solid concentration and stabilization • Thickening
Operation Application1. Screening Removal of floating water2. Comminution Grinding and shredding of big objects3. Equalization Equalization of flow and BOD loading4. Mixing Mixing of chemical and gases in wastewater and keeping solids in suspension5. Flocculation Enlarging small particle6. Sedimentation Removal of settleable solids7. Floatation Thickening of biological sludge8. Filtration Removal of fine material after biological or chemical treatment9. Micro screening Removal of algae from stabilization ponds, oxidation ponds effluent
Process Application1. Chemical precipitation Removal of phosphorus and enhancement of suspended solids removal in sedimentation2. Gas Transfer Addition and removal of gases3. Adsorption Removal of organics4. Disinfection Killing of disease causing organisms5. Dechlorination Removal of chlorine residuals6. Miscellaneous Specific wastewater treatments
Biological unit processes are those processes in which the removal ofobjectionable matter is done by biological activity. In this process the objectivesare to coagulate and remove the dissolved or nonsettleable colloidal solids. Biological processes are differentiated by the oxygen dependence ofthe microorganisms responsible for the wastewater treatment as follows,1. Aerobic processes: The processes occur in presence of oxygen by the aerobic bacteria. The aerobic process include the following, 1. Trickling filter (attached growth process) 2. Activated sludge process with its modifications (suspended growth process) 3. Aerobic Stabilization ponds (oxidation ponds) 4. Aerated lagoons2. Anaerobic processes: The anaerobic processes occur in absence of oxygen by the anaerobic bacteria. The anaerobic bacteria processes include the following, 1. Anaerobic sludge digestion 2. Anaerobic contact process 3. Anaerobic filters 4. Anaerobic lagoons or ponds 5. Septic tanks and imhoff tanks 3. Facultative process: the facultative bacteria can act in presence as well as in absence of oxygen.
WASTE WATER TREATMENT Physical unit operation Chemical unit operation Biological unit operation
FOUR LEVELS OF WASTE WATERTREATMENT PRELIMINARY TREATMENT PRIMARY TREATMENT SECONDARY TREATMENT TERTIARY/ ADVANCED TREATMENT
The treatment of wastewater is a general term that includes anyunit operation or process that can reduce the objectionableproperties sewage to make it less offensive (bad, foul). Thetreatment includes: 1. Removal of floating and suspended solid matter 2. Treatment of biodegradable organic matter 3. Disinfection (elimination of pathogenic organisms)
The various operations and processes for the treatment of sewage give effluent (treated wastewater) and the sludge (solids separated in semi solid form). The effluent may be directly disposed either in the receiving waters (rivers, ponds) or on land. The sludge is generally first of all treated and then disposed. The aim of processing sludge is to extract water (reduce high volumes) and dispose the dewatered residue through a combination of physical, chemical and biological operations. The after dewatering chemical conditioning and thickening the sludge is treated biologically, generally by anaerobic treatment.
SUSPENDED SOLID MATTER Small particles of solid pollutants that float on the surface of, orare suspended in sewage or other liquids. They resist removal by conventional means. BIODEGRADABLE The ability to break down or decompose rapidly under natural conditions and processes. DISINFECTANT A chemical or physical process that kills pathogenic organisms in water. Chlorine is often used to disinfect sewage treatment effluent, water supplies, wells, and swimming pools.
ORGANIC MATTER Carbonaceous waste contained in plant or animal matter and originating from industrial sources. DISINFECTION treatment to destroy harmful microorganisms PATHOGENS Microorganism that can cause disease in other organisms or in humans, animals and plants. They may be bacteria, viruses, orparasites and are found in sewage. Fish and shellfish contaminated by pathogens, or the contaminated water itself, can cause serious illnesses.
ANAEROBICDIGESTION AND BIOGAS
ANAEROBIC DIGESTION ANAEROBIC DIGESTION IS A SERIES OF PROCESSES IN WHICH MICROORGANISMS BREAK D OW N B I O D E G R A DA B L E M AT E R I A L I NT H E A B S E N C E O F OX YG E N. I T I S U S E D FOR INDUSTRIAL OR DOMESTICP U R P O S E S T O M A N A G E WA S T E A N D / O R T O R E L E A S E E N E R G Y.
ANAEROBIC DIGESTER ANAEROBIC DIGESTER I S A N A I R T I G H T, O X Y G E N - F R E ECONTAINER THAT IS FED AN ORGANIC MATERIAL, SUCH AS ANIMAL MANURE OR F OOD S C RA P S. A B I OL OG I C A LPROCESS OCCURS TO THIS MIXTURE TO P ROD U C E M E T H A N E G A S, C OM M ON LY K N OW N A S B I O G A S, A L O N G W I T H A NO D O R - R E D U C E D E F F L U E N T. M I C R O B E S B R E A K D OW N M A N U R E I N T O B I O G A S A N D A N U T R I E N T - R I C H E F F L U E N T.
THERE ARE FOUR KEY BIOLOGICALA N D C H E M I C A L S TAG E S O F A N A E RO B I C DIGESTION: HYDROLYSIS ACIDOGENESIS ACETOGENESIS METHANOGENESIS
T H E K E Y P RO C E S S S TAG E S O F ANAEROBIC DIGESTION
BIOGAS BIOGAS TYPICALLY REFERS TO A GAS PRODUCED BY THE BIOLOGICAL B R E A K D OW N O F O RG A N I C M AT T E R I N T H E A B S E N C E O F OX YG E N. O RG A N I C WA S T E S U C H A S D E A D P L A N T A N DANIMAL MATERIAL, ANIMAL FECES, AND K I T C H E N WA S T E C A N B E C O N V E R T E DI N T O A G A S E OU S F U E L C A L L E D B I OG A S.
Wet Land Treatment The process in which wastewater is distributed evenly distributed over the ground surface which acts as a low rate filter. Suspended particles are strained out colloids and organic matter are absorbed by the soil particles. Nutrients are utilized by vegetation and more complex organic materials are decomposed to simpler inorganic compounds by soil bacteria.
1. Natural Wetland Wetlands are areas that are permanently or periodically inundated or saturated by surface or groundwater and support the growth of aquatic vegetation. Wetlands are defined as land where the water surface is near the ground surface long enough each year to maintain saturated soil conditions, along with the related vegetation. Natural wetlands include saturated wetlands and freshwater wetlands.
Wetland plants can be classified into two (2) functional types: a. Rooted Plants * emergent macrophytes- roots in the sediment and emergent stems and leaves * submerged macrophytes- stems and leaves submerged * floating leafed macrophytes- stem submerged and leaves floating b. Floating Plants- they have surface leaves and roots which hang down into the water
2. Constructed Wetlands Constructed wetland is defined as a wetland specifically constructed for the purpose of pollution control and waste management, at a location other than naturally existing wetland. Constructed wetlands are used to improved the quality of point and non-point sources of water pollutants and are also used to treat petroleum refinery waste, compost and landfill leachates, fishpond discharges and pre- treated industrial wastewater.
Two (2) basic types of constructed wetland:a. Free Water Surface Wetland- consist of a basin or channels w/ some type of barriers to prevent seepage, soil to support the root of the emergent vegetation and water at a relatively shallow depth flowing through the system.b. Subsurface Flow Wetland- consists of a basin or channels with barriers.
Principal mechanism in wastewater treatment: a. sedimentation b. bacterial action c. filtration d. absorption e. precipitation f. nutrient uptake g. vegetation system
Advantages of Constructed Wetlands:• Wetlands can be less expensive to build than other treatment options.• Operation and maintenance expenses (energy and supplies) are low.• Operation and maintenance require only periodic, rather than continuous, on site labor.• Wetlands are able to tolerate fluctuations in flow.
• They facilitate water reuse and recycling.• They provide habitat for many wetland organisms.• They can be built to fit harmoniously into the landscape.• They provide numerous benefits in addition to water quality improvement.• They are an environmentally sensitive approach that is viewed with favour by the general publice
Disadvantages of Constructed Wetlands:• There are no standardized designs that can be routinely applied to universal applications. Each system of constructed wetlands must be custom- designed and site- specific. This limitation is not necessarily detrimental because it allows each system to be designed on wastewater flow, soil characteristics, and geochemical processes particular to each system’s needs.
• Constructed wetlands traditionally have poorer performance in colder weather. The biological processes slow down in lower temperatures. This severely limits winter use of the system.• Depending on the design, they may require a relatively large land area compared to a conventional facility.• The design and operating criteria for this new science are yet precise.
• The biological and hydrological processes within a constructed wetland are not yet well understood.• There may be possible problems with pests.
Effluent Disposal on Land1. Spraying Method- a process leads to removal waste load through filtration during percolation and removes most of the suspended solids. A combination of processes such as evaporation, transpiration, percolation and runoff work for the disposal of wastewater by spraying.
2. Drip Method- drip systems utilize pressure compensated drip tubing to slowly and evenly dispense the wastewater just below the soil surface, but still within the root zone of the vegetation.3. Ponding Method- used where evaporation losses are much greater. This method is preferred in there areas where land availability is not an issue and rainfall is not widespread and heavy.
Domestic Waste Disposal: Septic tank The septic tank is the most widely used method of disposal of domestic waste disposal. Septic tank was one of the most earliest treatment devices developed. It works simply by acting as a settling tank for the household sewage.Components of septic tank:a. Influent tank c. Dosing tankb. Settling tank d. Adsorption field
Some common methods:1. Spreading on land or soil- wet digested sludge may be disposed of by spreading over farmlands and plowing under after it has died. The humus in the sludge conditions the soil, improving its moisture relativeness.2. Lagooning- another popular method because it is simple and economical if the treatment plant is in remote location. A lagoon is an earth basin into which raw or digested sludge is deposited.
3. Dumping- a suitable disposal method only for sludge that are stabilized so that no decomposition or nuisance conditions will result. Digested sludge clean grit and incinerator can be disposed off safely by this method.4. Landfill- a sanitary landfill can be used for disposal of sludge, grease and grit whether it is stabilized or not if a suitable site is convenient. The sanitary landfill method is most suitable if it is also used for disposal of the refuse and other solid waste in the community.
In a true sanitary landfill, the wastes aredeposited in a designed area, compacted inplace with a tractor or roller, and coveredwith 30cm layer of clean soil.
Digested Sludge in Different Application on Land:1. Cropland- sludges are applied to cropland either by surface spreading, or by subsurface injection sludge is usually applied once a year to a given area.2. Marginal Land- sludges has been applied to marginal land for reclamation in Pennsylvania and in other states successfully. This is usually a one- time process and a continual supply of land must be provided for future applications.
3. Forest Land- it is determined by sludge characteristics, tree maturity, species, soil, etc. application to a specific site is often done only at multi- year intervals.
Septic Tank& Soak Pits
SEPTIC TANK• It is a combination of sedimentation and digestion tanks where the sewage is held for 24 hours. During this period the sattleable suspended solids settle down to the bottom.
SEPTIC TANK • The direct outflow of the sewage is restricted by the provision of two baffle walls. The baffle walls divide it in three components and the sewage entering at any time gets exit after 24 hours.
SEPTIC TANK• The tank is organic matter and thus reduces BOD. This results in the reduction of in the volume of sludge and release of gases like carbon dioxide , methane and hydrogen sulfide. The hydrogen sulfide is an obnoxious gas and smells like rotten eggs so the problem of foul gases is always there and so it is called as a septic tank.
SOAK PITS• Preferable when water table is low and the soil is porous.• It is easy to construct and cheap.• Circular fit with a dry masonry lining.• It has a size of 3.0m diameter and 3.0m depth which is sufficient for a moderate family of 5 persons for a cleaning period of 7 years in porous soil.
SOAK PITS• It can accommodate the whole sewage of the house and nothing comes out of it so there is no problem of treatment and disposal.• It is planned and constructed in such a way that the water of sewage is soaked in the soil and penetrates deep under ground.•
SOAK PITS• The only consideration is the: GROUND WATER TABLE It should be deep so that either the percolating sewage does not mixes with it or it gets purified in its journey through the soil layers before it mixes with the ground water. After all if it mixes with the ground water the pathogenic bacteria present in it shall contaminate the ground water and one has to treat the tube-well before direct consumption.