Drinking water

Drinking water

Drinking water


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EARTH WATER RESOURCESOCEAN519 063 400 km 3GLACIERSUNDERGROUNDWATERS9 654 000 km 33 218 000 km 3ATMOSPHERE4 827 km 3¾ of the Earth is covered by <strong>water</strong>, but drinking <strong>water</strong> resources arelimited in many places of the World.2

EARTH WATER RESOURCESOnly 3 % of the Earth resources is fresh<strong>water</strong>.Fresh<strong>water</strong>OceanGlaciersUnderground<strong>water</strong>sRivers, lakes, streams,dams, etc.3

DRINKING WATERPotable <strong>water</strong> source in the Sahara Desertmarked in Italian, German, Polish andEnglish.<strong>Drinking</strong> <strong>water</strong> or potable <strong>water</strong> is <strong>water</strong> pureenough to be used with low risk ofimmediate or long term harm.In most developed countries, the <strong>water</strong>supplied to households, commerce andindustry is all of drinking <strong>water</strong> standard,even though only a very small proportionis actually consumed or used in foodpreparation.Over large parts of the world, humans haveinadequate access to potable <strong>water</strong> anduse sources contaminated with diseasevectors, pathogens or unacceptable levelsof toxins or suspended solids.Such <strong>water</strong> is not wholesome, and drinking orusing such <strong>water</strong> in food preparation leadsto widespread acute and chronic illnessesand is a major cause of death and miseryin many countries.Reduction of <strong>water</strong>borne diseases is a majorpublic health goal in developing countries.4

Percentage of population with access to safedrinking <strong>water</strong>Country% Country % Country % Country % Country %Albania 97 Algeria 89 Azerbaijan 78 Brazil 87 Chile 93China 75 Cuba 91 Egypt 97 India 84 Indonesia 78Iran 92 Iraq 85 Kenya 57 North Korea 100SoughtKorea92Mexico 88 Moldova 92 Morocco 80 Mozambique 57 Pakistan 90Peru 80 Philippines 86 Singapore 100 Sought Africa 86 Sudan 67Syria 80 Turkey 82 Uganda 52 Venezuela 83 Zimbabwe 83

Water quality - percent of population usingimproved <strong>water</strong> sources by country

ACCESS TO DRINKING WATEROnly 46 % of people in Africa havesafe drinking <strong>water</strong>.<strong>Drinking</strong> <strong>water</strong> vending machines in Thailand.One litre of purified <strong>water</strong> is sold(into the customer's own bottle) for 1 bath (1 EUR≈ 43 thai bath).Water from taps, but supplied by a truck.7

EPA drinking <strong>water</strong>security poster.

WATER TREATMENTWater is one of the most essential substances in human life,production and technological processes.In production, just as in nature, <strong>water</strong> circulation can bedescribed as a cycle consisting of several stages.The <strong>water</strong> cycle comprises the source of <strong>water</strong>, its purificationto make it potable or usable in production processes andconsumption, which, in turn, results in contamination andsubsequent need for waste<strong>water</strong> treatment.There are two types of technological processes for maintaining<strong>water</strong> for human consumption – preparation of drinking<strong>water</strong> and waste<strong>water</strong> treatment.

WATER TURNOVER IN SOCIETYWaterconsumptionSupply forconsumersWaste<strong>water</strong>collectionWater treatmentWaste<strong>water</strong>treatmentWater sourceDrainageIndirect use10

Water purificationWater is purified for two reasons: to ensure the <strong>water</strong>quality the consumers require or to prevent theformation of <strong>water</strong> pollution.Consumers need <strong>water</strong> with quite different qualityparameters;therefore, <strong>water</strong> treatment generally falls into threebroad categories:▪ preparation of drinking <strong>water</strong>,▪ preparation of technological <strong>water</strong> for productionprocesses,▪ waste<strong>water</strong> treatment for reuse or to the quality ofenvironment-friendly <strong>water</strong> before dischargeinto open bodies of <strong>water</strong>.

Continuity of <strong>water</strong> supply is taken for granted in most developed countries, but is a severeproblem in many developing countries, where sometimes <strong>water</strong> is only provided for a fewhours every day or a few days a week. It is estimated that about half of the population ofdeveloping countries receives <strong>water</strong> on an intermittent basis.Phases of the <strong>water</strong> supply:Water extractionWATER SUPPLYWater purificationWater storageWater transportationWater distribution12

SERVICE PROVISIONWater supply service providers, differ from each other in terms of their geographicalcoverage relative to administrative boundaries; their sectoral coverage; theirownership structure; and their governance arrangements.Many <strong>water</strong> utilities provide services in a single city, town or municipality. However, inmany countries municipalities have associated in regional or inter-municipal ormulti-jurisdictional utilities to benefit from economies of scale. In the US these cantake the form of special-purpose districts which may have independent taxingauthority.Multi-jurisdictional utilities are also common in Germany (are known as "Zweckverbaende“),in France and in Italy.In some federal countries there are <strong>water</strong> service providers covering most or all citiesand towns in an entire state, such as in all states of Brazil and some states inMexico.In UK <strong>water</strong> supply and sewerage is supplied almost entirely through regionalcompanies.Some smaller countries, especially developed countries, have established serviceproviders that cover the entire country or at least most of its cities and majortowns.Such national service providers are especially prevalent in West Africa and CentralAmerica, but also exist, for example, in Tunisia, Jordan and Uruguay.In rural areas, where about half the world population lives, <strong>water</strong> services are oftennot provided by utilities, but by community-based organizations which usuallycover one or sometimes several villages.

OWNERSHIP AND GOVERNANCE ARRANGEMENTSWater supply providers can be either public, private, mixed or cooperative. Most urban<strong>water</strong> supply services around the world are provided by public entities.The introduction of cost-reflective tariffs together with cross-subsidisation between richerand poorer consumers is an essential governance reform in order to reduce the highlevels of unaccounted <strong>water</strong> and to provide the finance needed to extend the networkto those poorest households who remain unconnected.Partnership arrangements between the public and private sector can play an important rolein order to achieve this objective.An estimated 10 percent of urban <strong>water</strong> supply is provided by private or mixed publicprivatecompanies, usually under concessions, leases or management contracts. Underthese arrangements the public entity that is legally responsible for service provisiondelegates certain or all aspects of service provision to the private service provider for aperiod typically ranging from 4 to 30 years.The public entity continues to own the assets. These arrangements are common in Franceand in Spain.Only in few parts of the world <strong>water</strong> supply systems have been completely sold to theprivate sector (privatization), such as in England and Wales as well as in Chile.The largest private <strong>water</strong> companies in the world are Suez (Suez was result of a 1997merger between the Compagnie de Suez and Lyonnaise des Eaux) from France; Aguas deBarcelona from Spain; and Thames Water from the UK, all of which are engagedinternationally.90% of urban <strong>water</strong> supply services are currently in the public sector. They are owned by thestate or local authorities, or also by collectives or cooperatives. They run without an aimfor profit.14

OWNERSHIP AND GOVERNANCE ARRANGEMENTSIn most middle and low-income countries, these publicly-owned and managed <strong>water</strong>providers can be inefficient as a result of political interference, leading to over-staffingand low labour productivity. Ironically, the main losers from this institutionalarrangement are the urban poor in these countries.Because they are not connected to the network, they end up paying far more per litre of<strong>water</strong> than do more well-off households connected to the network who benefit from theimplicit subsidies that they receive from loss-making utilities.Governance arrangements for both public and private utilities can take many forms.Governance arrangements define the relationship between the service provider, itsowners, its customers and regulatory entities.They determine the financial autonomy of the service provider and thus its ability tomaintain its assets, expand services, attract and retain qualified staff, and ultimately toprovide high-quality services.Key aspects of governance arrangements are the extent to which the entity in charge ofproviding services is insulated from arbitrary political intervention; and whether there isan explicit mandate and political will to allow the service provider to recover all or atleast most of its costs through tariffs and retain these revenues.If <strong>water</strong> supply is the responsibility of a department that is integrated in the administrationof a city, town or municipality, there is a risk that tariff revenues are diverted for otherpurposes. In some cases, there is also a risk that staff are appointed mainly on politicalgrounds rather than based on their professional credentials.15

METERINGMetering of <strong>water</strong> supply is usually motivated by one or several of four objectives:- it provides an incentive to conserve <strong>water</strong> which protects <strong>water</strong> resources(environmental objective),- it can postpone costly system expansion and saves energy and chemical costs(economic objective),- it allows a utility to better locate distribution losses (technical objective),- it allows to charge for <strong>water</strong> based on use, which is perceived by many as thefairest way to allocate the costs of <strong>water</strong> supply to users.Metering is considered good practice in <strong>water</strong> supply and is widespread indeveloped countries, except for the UK. In developing countries it is estimatedthat half of all urban <strong>water</strong> supply systems are metered and the tendency isincreasing.

WATER METERS READINGWater meters are read by one of several methods:- the <strong>water</strong> customer writes down the meter reading and mails in a postcardwith this info to the <strong>water</strong> department;- the <strong>water</strong> customer writes down the meter reading and uses a phone dial-insystem to transfer this info to the <strong>water</strong> department;- the <strong>water</strong> customer logs in to the website of the <strong>water</strong> supply company, entersthe address, meter ID and meter readings;- a meter reader comes to the premise and enters the meter reading into ahandheld computer;- the meter reading is echoed on a display unit mounted to the outside of thepremise, where a meter reader records them;- a small radio is hooked up to the meter to automatically transmit readings tocorresponding receivers in handheld computers, utility vehicles or distributedcollectors;- a small computer is hooked up to the meter that can either dial out or receiveautomated phone calls that give the reading to a central computer system;- Installation of the Automatic Meter Reading Systems to prevent fraud, to lowerever-increasing labour and liability costs and to improve customer service andsatisfaction.

WATER SUPPLYWater supply is dependent of <strong>water</strong> demand, needs of consumers, <strong>water</strong>sources in the local environment, technical potentialities.Forms of <strong>water</strong>supplyCentralisedsystemsDecentralisedsystemsPublic <strong>water</strong> supplyLocal <strong>water</strong>supplyIndividual <strong>water</strong>supplyChelsea Waterworks, 1752. Two beam enginespumped Thames <strong>water</strong> from a canal to reservoirs atGreen Park and Hyde Park.18

WATER QUALITYWater supply system is available to provide <strong>water</strong> of different quality.<strong>Drinking</strong> <strong>water</strong> – everyday for residentsTechnological <strong>water</strong> – forindustrial and agriculturalneedsWater are used for different needs, thereforeconsumers ask for different quality of <strong>water</strong>.Food processing are using mainly drinking <strong>water</strong>, but somesectors seeks for more higher quality of <strong>water</strong> – distilled ortwice distilled <strong>water</strong>.Water supply providers is responsible for <strong>water</strong> flow as far as a tap, inflow inbuilding or border of the landed estate.19

WATER SUPPLY PROBLEMSWater quality can be lowered by:→ cracks in the pipes→ insufficient pressure in thepipe’s net→ unexpected pollution→ through unforeseencircumstancesLoss of <strong>water</strong> by:ACTUAL→ breaks in pipes→ joining defect→ imperfect packingSEEMING→ inaccuracy of the <strong>water</strong> meter→ mistakes at determination of <strong>water</strong>volume→ lack of inventory for <strong>water</strong> quantity20

DRINKING WATER<strong>Drinking</strong> <strong>water</strong> are surface or ground <strong>water</strong>, pure enough to be consumed or used withlow risk of immediate or long term harm. <strong>Drinking</strong> <strong>water</strong> with special treatment or withouttreatment and apart from form of supply (pipeline, cistern or packaging), is provided for:→ cooking→ use in household→ trade→ food processing21

WATER RESOURCES IN LATVIAWater resources use are approximately 20 % of total.Surface <strong>water</strong> –use ~ 33-35 km 3 /yearGround <strong>water</strong> –use ~ 1,4 milj. m 3 /dayProblem in Latvia – irregularity of the spatialdistribution in <strong>water</strong> use.22

GROUNDWATERGround<strong>water</strong> is located beneath the ground surfacein soil pore spaces and in the fractures of rockformations. A unit of rock or an unconsolidateddeposit is called an aquifer when it can yield a usablequantity of <strong>water</strong>. The depth at which soil porespaces or fractures and voids in rock becomecompletely saturated with <strong>water</strong> is called the table.Ground<strong>water</strong> is recharged from, and eventually flows to, thesurface naturally; natural discharge often occurs at springsand seeps (caursūkšanās), and can form wetlands.Ground<strong>water</strong> is also often withdrawn for agricultural, municipaland industrial use by constructing and operating extractionwells.The study of the distribution and movement of ground<strong>water</strong> ishydrogeology, also called ground<strong>water</strong> hydrology.23

GROUNDWATERBy intensity of <strong>water</strong> exchange and chemical content in vertical section there are3 hydrodynamic zones:→ active circulation (fresh-<strong>water</strong>) zone – developing fromprecipitation (full <strong>water</strong> turnover takes 100-1000 years);→ slow down circulation (brackish-<strong>water</strong>) zone –full <strong>water</strong>turnover takes many hundred thousands – one millionyears;→ stagnant <strong>water</strong> zone.24


An aquifer is a layer of porous substrate that contains and transmits ground<strong>water</strong>. When<strong>water</strong> can flow directly between the surface and the saturated zone of an aquifer, theaquifer is unconfined.The deeper parts of unconfined aquifers are usually more saturated since gravity causes<strong>water</strong> to flow downward.A confined aquifer is an aquifer that is overlain by a relatively impermeable layer of rockor substrate. If a confined aquifer follows a downward grade from its recharge zone,ground<strong>water</strong> can become pressurized as it flows. This can create artesian wells that flowfreely without the need of a pump and rise to a higher elevation than the static <strong>water</strong>table at the above, unconfined, aquifer.GROUNDWATERThickness of the aquifer, used for <strong>water</strong> extraction is from some meters up to 50 m.In Latvia artesian wells are 100-300 m deep.26

GROUNDWATER CHEMICAL CONTENTGround<strong>water</strong> chemical content is dependent by:→ Topography – affect surface and underground flow,distribution of precipitation, processes of salt’s migrationin soil, tendencies of the bogging-up;→ climate – quantity and mode of precipitation, temperatureand evaporation;→ minerals – chemical content, processes of weathering,their intensity;→ covering of soil.27

GROUNDWATER CHEMICAL CONTENTChemical content of ground<strong>water</strong> in Latvia:→ calcium hydrogen carbonate Ca(HCO 3 ) 2→ high content of ironMaximal permissible concentration for iron(Fe)→ in some places high content of the organiccarbon C org. (up to 80 mg/l), ammonia NH 4(up to 30 mg/l) and iron (up to 90 mg/l)→ here and there (Liepaja, Jurmala) highconcentration of the calcium sulphateCaSO 4 :Standard by World Health Organisation forSO 42-is:0,3-0,4 g/l0,3-3,0 mg/l0,4 mg/llīdz 400 mg/l SO 42-līdz 250 mg/l SO 42-28

PROBLEMS WITH GROUNDWATERS IN LATVIA→ HIGH IRON CONCENTRATION→ HIGH RATE OF OXIDATION→ HIGH AMMONIA, PHENOL,MANGANESE CONCENTRATIONGround<strong>water</strong> risks in Latvia:→ drying up – as ground<strong>water</strong> system’sconditions are changing;→ pollution – can change hydro chemical contentof ground<strong>water</strong>.29

PROBLEMS WITH GROUNDWATERS IN LATVIAProtected (minimal risk)Relatively protected (low risk)On average protected (medium)Poorly protected (high risk)Not protected (highest risk)Devon sedimentsMain threat for ground<strong>water</strong> quality and quantity is inadequate economic activities !30

IRON CONTENT IN GROUNDWATER IN LATVIAESTONIARUSSIABalticSeaRiga gulf>4,2 mg/l2,8-4,1 mg/l1,4-2,7 mg/l0-1,3 mg/lLITHUANIABELARUS31

GROUNDWATER SOURCES IN LATVIAGround<strong>water</strong> resources are renewed by:→ precipitation (rain, snow);→ run-off from surface <strong>water</strong>s (rivers,lakes).Annual supplement for the ground <strong>water</strong>s in Latvia comes by infiltration - approximately 4,7km 3 or 1/3 of run-off from surface <strong>water</strong>s in whole Latvia (~15,7 km 3 /year).32

GROUNDWATER FLOWSRelieve(atslodzes)zoneFeeding zoneRailway or highwayaccident placesLandfillAgricultural landsOil reservoirsInfiltration fromsoil fertilizingRelieve zoneRun-off from oilreservoirsRun-off from manurestorageRun-off from wastedumping groundsWater aquiferFlow’s systemGround <strong>water</strong>s run-off flows and pollution sources33

<strong>Drinking</strong> <strong>water</strong> pollution detector Rainbow trout (Oncorhynchus mykiss) are being usedin <strong>water</strong> purification plants to detect acute <strong>water</strong> pollution.

USE OF THE GROUNDWATERSIn the World:In the Europe:→ approximately 6 000 km 3 /year - 14% oftotal <strong>water</strong> resources;→ 80 % of ground <strong>water</strong> are used for toirrigation of the agricultural fields, whataccelerate evaporation process and<strong>water</strong> turn-over cycle, as well as cause<strong>water</strong> losses;→ as result annually ~ 2 900 km 3 of <strong>water</strong>(48 % of the total consumption) are lost.→ in the Western Europe <strong>water</strong>consumption (surface and ground<strong>water</strong>) in 100 years were growth 18times and now are ~ 380 km 3 per year(18 % from total surface run-off);→ more as a half of <strong>water</strong> are used forindustry, but 1/3 for agriculture.35

MINERAL AND SPRING WATERNatural mineral <strong>water</strong> areextracted from undergroundsources is different from drinking<strong>water</strong> by chemical content andtemperature.However, main quality parametersare constant for fixed source place.A spring is a component of the hydrosphere,specifically, any natural situation where <strong>water</strong> flowsto the surface of the earth from underground. Thus, aspring is a site where the aquifer surface meets theground surface.Minerals become dissolved in the <strong>water</strong> as it movesthrough the underground rocks. This may give the<strong>water</strong> flavour and even carbon dioxide bubbles,depending on the nature of the volume throughwhich it passes. This is why spring <strong>water</strong> is oftenbottled and sold as mineral <strong>water</strong>.36

Springs are often classified by the volume of the <strong>water</strong> they discharge. The largestsprings are called "first-magnitude," defined as springs that discharge <strong>water</strong> at a rateof at least 2800 liters or 100 cubic feet (2.8 m 3 ) of <strong>water</strong> per second.Magnitude Flow (ft³/s, gal/min, pint/min) Flow (l/s)1st magnitude > 100 ft³/s 2800 l/s2nd magnitude 10 to 100 ft³/s 280 to 2800 l/s3rd magnitude 1 to 10 ft³/s 28 to 280 l/s4th magnitude 100 US gal/min to 1 ft³/s (448 US gal/min) 6.3 to 28 l/s5th magnitude 10 to 100 gal/min 0.63 to 6.3 l/s6th magnitude 1 to 10 gal/min 63 to 630 ml/s7th magnitude 1 pint to 1 gal/min 8 to 63 ml/s8th magnitude Less than 1 pint/min 8 ml/s0 magnitude no flow (sites of past/historic flow)

Spring of Vaucluse in France discharges about 1,800,000 m 3 of <strong>water</strong> per day at arate of 21 m 3 per second.

MINERAL WATERS IN LATVIAWater from springs are usually clear. However some springs may be coloured by the mineralsthat are dissolved in the <strong>water</strong>. Iron and tannins often give spring <strong>water</strong> an orange colour.The cool <strong>water</strong> of a spring and its branch may harbour species such as certain trout that areotherwise ill-suited to a warmer local climate.Mineral <strong>water</strong>s in Latvia are at the depth 100-400 m (100 m at North part of Kurzeme, 400 m atVidzeme heights).NaCl mineral <strong>water</strong>s are in whole territory ofLatvia (Valmieras, Mangaļu, Siguldas m.w.) –has salt’s concentration of 1-3 g/l.H 2 S mineral <strong>water</strong>s (Baldone,Ķemeri) – has salt’s concentrationaround 3 g/l.Mineral <strong>water</strong> “Stelpes” and it’s filling line. Sulphur mineral <strong>water</strong> spring in Ķemeri. 39

When ground<strong>water</strong> arepulled upward that causesa few changes for the <strong>water</strong>table. Because wells drawfrom one point, <strong>water</strong> flowsupward but also outward inall directions. This outwardsurge, though gradual,causes the <strong>water</strong>-table levelaround the well to morphinto a cone-like shapetermed a "cone ofdepression“.CONE OF DEPRESSIONWateraquiferCone ofdepressionWellFlow ofground<strong>water</strong>Water levelIn Latvia are two large cones of depression:“Liepaja” (1000 km 2 ) – 1930;“Great Riga” (7000 km 2 ) – 1960-1980.As use of ground <strong>water</strong> are reducing in latest decades, cones of depressionprogressively, but unequal results in <strong>water</strong> level rising and accordingly cones ofdepression diminish.40

WATER TREATMENTKOAGULATIONAERATIONFILTRATIONFILTRATIONSEDIMENTATIONWater treatment describes thoseprocesses used to make <strong>water</strong> moreacceptable for a desired end-use.The goal of all <strong>water</strong> treatmentprocess is to remove existingcontaminants in the <strong>water</strong>, or reducethe concentration of suchcontaminants so the <strong>water</strong> becomesfit for its desired end-use.DESINFECTIONSTORAGE ANDDISTRIBUTION41

PRELIMENARY OPERATIONS - SETTLINGSettling is the process by which particulates settle to the bottom of a liquid and form asediment. Particles that experience a force, either due to gravity or due to centrifugalmotion will tend to move in a uniform manner in the direction exerted by that force. Forgravity settling, this means that the particles will tend to fall to the bottom of the vessel,forming a slurry at the vessel base.by:Settling process is slow. Possible to sediment only rough participles (no colloid sizeparticiples) – Stokes’ law.42

Settling pond for solid particles at <strong>water</strong> works, Kalová laguna, Sojovice,Czech Republic.

Filtration is commonly the mechanicalor physical operation which is used forthe separation of solids from fluids byinterposing a medium through whichonly the fluid can pass.Aeration is the process by which air is circulated through, mixed with ordissolved in a liquid or substance. In this manner possible to oxidise acompound dissolved or suspended in <strong>water</strong> (H 2 S, CH 4 , NH 3 , volatile organicsubstances) – unpleasant odour and taste are reduced.Air oxygen helps to reduce iron content in <strong>water</strong> byoxydation soluble Fe(II) for non soluble Fe(III).44

Slow "artificial" filtration to the ground, Water purification plant Káraný, CzechRepublic.

COAGULATION AND FLOCCULATIONCoagulation is precipitation of suspended particles as they increase in size (by any ofseveral physical or chemical processes). Flocculation is a process wherein colloidscome out of suspension in the form of flakes by the addition of a clarifying agent.Flakes can adsorb organic polymers (large molecules made up of a linked series ofrepeated simple monomers) , bacteria, viruses. Process substantially reduceconcentration of dissolved substances and colloid participles.CoagulantAs coagulants are used iron or aluminium salts (chlorides or sulphates).46

COAGULATION AND FLOCCULATIONAluminium sulphate is frequently used coagulantAl 2 (SO 4 ) 3 ∙18H 2 OAluminium sulphate in <strong>water</strong> are hydrolyzed – formpoorly soluble aluminium hydroxide, which moleculesstart to polymerize shaping polymer structure.Aluminium sulphateFlowPositively chargedaluminium hydroxidecomplexesNegatively charged are colloid participles, bacteriaand acidic organic substances, solved in <strong>water</strong> (humicacids, fulvio-acids)StartdevelopingcoagulationcentresDepositionSediments of metal hydroxides accumulated in secondary sedimentationreservoirs.47

Mechanical system to pushfloc out of the <strong>water</strong> basin.Floc floating at the surface of a basin.

USE OF THE ADSORBENTS FOR WATER TREATMENTAdsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, ordissolved solids to a surface. This process creates a film of the adsorbate (themolecules or atoms being accumulated) on the surface of the adsorbent. It differs fromabsorption, in which a fluid permeates or is dissolved by a liquid or solid. The termsorbtion encompasses both processes, while desorbtion is the reverse of adsorption.For <strong>water</strong> purification from dissolved organic substances use sorbents activated carbon,purified anthracite or hydrophobic synthetic sorbents.AdsorbedmoleculesActivatedcarbonPoreActivated carbon areproduced from wood, peat,other organic materials -apricot pit (kernel) by gettingcharred at anaerobesconditions in temperaturehigher as 600°C followed byactivation – partly oxidationat 800-900°C.Participle of activated carbonin microscope.49

USE OF THE ADSORBENTS FOR WATER TREATMENTActivated carbon or anthracite for <strong>water</strong> treatment use in aform of pellet in columns or as layer in filtration volume.Pellets of theactivated carbon.Adsorption columns.This method is very efficient, although quite expensive, therefore isn’t use forindustrial <strong>water</strong> treatment.50

Cutaway view of a typical rapid sand filter.

SECONDARY SETTLING AND FILTRATIONAfter coagulation, <strong>water</strong> is settled in secondary basins and filtered. The purified <strong>water</strong>from the settling or flocculation reservoirs is drawn into the filter tank, where it moves bygravitational force through the sand filter layer down to the drainage system installed atthe bottom part of the filter, from where it is then drained to the <strong>water</strong> storage tank.A sand bed filter is a kind of depth filter.Broadly, there are two types of filter forseparating particulate solids from fluids:→ surface filters, where particulates arecaptured on a permeable surface;→ depth filters, where particulates arecaptured within a porous body of material.Overall, there are several categories of sand bedfilter:• rapid (gravity) sand filters• rapid (pressure) sand bed filters• up flow sand filters• slow sand filters.Membrane filters system.52

DISINFECTIONDisinfection is accomplished both by filtering out harmful microbesand also by adding disinfectant chemicals in the last step in purifyingdrinking <strong>water</strong>.Water is disinfected to kill any patogens which pass through thefilters.In most developed countries, public <strong>water</strong> supplies are required tomaintain a residual disinfecting agent throughout the distributionsystem, in which <strong>water</strong> may remain for days before reaching theconsumer.Following the introduction of any chemical disinfecting agent, the<strong>water</strong> is usually held in temporary storage – often called a contact tankor clear well to allow the disinfecting action to complete.Disinfection methods include chlorination, ozonization,UV-light.53

Chlorination is the process of adding the element chlorine to <strong>water</strong> as a method of <strong>water</strong> purificationto make it fit for human consumption as drinking <strong>water</strong>. Water which has been treated with chlorineis effective in preventing the spread of <strong>water</strong>borne disease.The use of chlorine has greatly reduced the prevalence of <strong>water</strong>borne disease as it is effectiveagainst almost all bacteria and vireses, as well as amoeba.Cl 2 (gaseous) ↔ Cl 2 (solution) + H 2 O→→ H + + Cl - + HClOCHLORINATIONHClO ↔ H + + ClO - Total amount of the Cl 2 , ClO -un HClO is activated chlorine.Quantity characterize actualability for disinfection of<strong>water</strong>.54

Solar <strong>water</strong> disinfection application in Indonesia.

→ Softening→ Fluorination→ Iron removal→ Decontamination ofnitrates→ Decontamination ofnatural organicsubstancesIron removal facility in KarsavaWater softening facility in Liepaja56

Iron and manganese removalMain methods for iron and manganese removal in drinking <strong>water</strong>:→ Aeration: in presence of oxygenFe(II) are oxidized on low-solubleFe(III)→ Chemical oxidation: are usedchlorine gas Cl 2 or sodiumhypochlorite NaClO, ozone O 3 ,potassium permanganate KMnO 4 ,hydrogen peroxide H 2 O 2→ Catalytic oxidation of manganesedioxide: as catalyst are used specialfiltration materials and overpressure→ Iron removal-softening: iron andmanganese ions are precipitatedwith sodium hydroxide NaOH→ Surface oxidation: beforefiltration air are injected – ironare oxidized and accumulatedon surface of filter→ Ions exchange: <strong>water</strong> arefiltrated through sodiumcationite - Na + ions areexchanged by iron, manganeseor other ions→ Biological iron removal :specific bacteria are used – theyoxidize Fe(II) on Fe(III), whichare accumulated in cells cover57


Riga’s <strong>water</strong> supply historyIn Riga centralised <strong>water</strong> supply system development starts at themiddle of 17 century, when residents has been supplied with <strong>water</strong> fromriver Daugava, using pumping with horses force and wooden pipelines.In 1863 wooden pipes has been replaced by castiron pipes, but pumping station start to use steamenergy.First <strong>water</strong> pumping station in Riga(1863).At 19 century non <strong>water</strong> quality fromriver Daugava non existing system of<strong>water</strong> supply satisfied demand.59

Riga’s <strong>water</strong> supply historyIn Riga till now are some <strong>water</strong> towers, built in 19-20century.CiekurkalnsMatisa streetAgenskalnsIn 1903-1904 at Bukultu estate has been built ground <strong>water</strong> extractionstation and pipelines from lake Baltezers to Riga.60

DRINKING WATER SUPPLY FOR RIGA NOWADAYS<strong>Drinking</strong> <strong>water</strong> for residents of Riga are transported from:→ river Daugava→ ground <strong>water</strong> sources “Baltezers”, “Zakumuiza” and“Rembergi” (~ 85 000 m³ day) – mainly for right bankterritories of river DaugavaAt “Baltezers” pumping station <strong>water</strong> isextracted from ~150 m deep wells.In the old pumping station “Baltezers”now is Museum of Water supplyhistory.Ground <strong>water</strong> reserves are replenishingfrom lake Baltezers, usinginfiltration method.61

DRINKING WATER TREATMENT PLANT “DAUGAVA”Water are taken from river Daugava (Rigahydropower plant reservoir) and pumped to<strong>Drinking</strong> <strong>water</strong> treatment plant “Daugava” withcapacity 210 000 m 3 per day.62

RIGA WATER PIPELINE SYSTEMRiga pipeline’s system length is 1 380 km ,Built from different material and size (diameter 20 - 1200 mm) pipes.Some pipes are hundred or more years old, therefore trouble crew quitefrequently are on duties.30 cm diameter <strong>water</strong> pipe crack in Riga, Nicgales Str. on July, 2010.63

RIGA WATERSUPLY SYSTEMAPZĪMĒJUMISūkņu stacijas ūdens ņemšanasvietāsSpiediena paaugstināšanasstacijas vai ūdenstorņiGalvenās ūdensvada maģistrāles64

WATER EXTRACTION IN LATVIAWater extraction in different river basins in Latvia:Daugava river basinAnnual <strong>water</strong> volume extracted118 279 000 m 3Daugava, Aiviekste, Dubna, Rēzekne,Malta, Ogre, Pededze, L.Jugla, M.JuglaGauja river basin10 717 530 m 3Gauja, Salaca, Amata, Rūja, BraslaVenta river basin12 260 800 m 3Venta, Abava, Irbe, Saka, RojaLielupe river basin4 144 600 m 3Lielupe, Mēmele, Mūsa, Iecava,Svēte, Dienvidsusēja65


Investments needed for Latvia to fulfill requirements of the EU directives98/83/EC and 91/271/EC on drinking <strong>water</strong> supply and waste<strong>water</strong>treatment; milj. LVL.

Parameter World Health Organization European UnionAcrylamide “ 0.10 μg/Arsenic 10μg/l 0.1 μg/lBarium 700μg/l nsBenzene 10μg/l 1.0 μg/lBenzo(a)pyrene “ 0.010 μg/lBoron 2.4mg/l 1,0 mg/lBromate “ 10 μg/lCadmium 3μg/l 5,0 μg/lChromium 50μg/l 50 μg/lCopper “ 2.0 mg/lCyanide “ 50 μg/lFluoride 1.5 mg/l 1.5 mg/lLead “ 10 μg/lMercury 6μg/l 1.0 μg/lNickel “ 20 μg/lNitrate “ 50 mg/lNitrite “ 0.50 mg/lPesticides (individual/total) “ 0.10 μg/ l/0.50 μg/lPolycyclic aromatic hydrocarbons “ 0.10 μg/Selenium 40μg/l 10 μg/lWHO AND EU WATER QUALITY STANDARDS68

ALTERNATIVE WATER TREATMENTWater treatment, when safe drinking <strong>water</strong>isn’t available :→ Boiling: after 3 minutes of boiling practically all bacteriaand viruses are extinguish→ Filtration: at high pollution level with inorganic substances filters gals orceramic fibber) are recommend→ Chemical treatment: iodine or chlorinedioxide solutions or pellets are recommend→ Inovative methods: treatment with special devices (UV light)69

The authentic ALEGI <strong>water</strong> disinfectionThe system kills e.coli bacteria and legionella bacteriafrom the <strong>water</strong>. Your drinking <strong>water</strong> stays clean andhealthy. Up to 1.200 litres per hour/70.000 litresinternal <strong>water</strong> circulation (tank).• In the home, between the <strong>water</strong> pump and theappliances (taps).• On your yacht, on transport ships, on cruisers.• In your firm and industries.• On your farm.• For all drinking <strong>water</strong> situations.


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