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Dr.Atikah,MSi,AptJurusan Kimia FMIPAUniversitas Brawijaya (UB)2012Lingkungan air

04/12/2012Kimia Lingkungan Air-11ReferensiFrom Green Chemistry and the Ten Commandments of Sustainability, Stanley E. Manahan, ChemChar Research, Inc., 2006 manahans@missouri.eduManahan, Stanley E. "ENVIRONMENTAL SCIENCE, TECHNOLOGY, AND CHEMISTRY"Environmental Chemistry, Boca Raton: CRC Press LLC, 2000

04/12/2012Kimia Lingkungan Air-12Air, dengan rumus kimia tampak sederhana H2O, merupakan substansi sangat penting dalam semua bagian dari lingkungan. Air mencakup sekitar 70% keberadaanya di semua bidang lingkungan dari permukaan bumi, dengan lautan sebagai reservoir terbesar Keberadaan air mulai dari :air asin, air atas tanah sebagai air permukaan di danau dan sungai, air bawah tanah sebagai air tanah, di atmosfer sebagai uap air, dalam ice caps kutub seperti es padat, dan.

pendahuluan04/12/2012Kimia Lingkungan Air-13Keberadaan air juga terdapat dalam banyak segmen anthrosphere seperti dalam boiler atau sistem distribusi air kota

Air merupakan bagian penting dari semua sistem kehidupan dan Merupakan media dari mana kehidupan berevolusi dan di mana ada kehidupanPENDAHULUAN04/12/2012Kimia Lingkungan Air-14Air yang digunakan manusia harus cukup keberadaannya dan bersihOleh karena itu kita perlu mengukur kuantitas dan kualitas air dalam rangka untuk memahami di mana masalah air terjadi Air dapat menjadi "terbarukan" jika penggunaan air < dibandingkan air yang dapat di Recharge (pengisisn kembali air)Air dapat menjadi "terbarukan" jika Polusi air < dari Pembersihan air

AIR04/12/2012Kimia Lingkungan Air-15H2O: RUMUS MOLEKUL SEDERHANA, MOLEKUL KOMPLEKSSiku struktur molekul air (lihat slide berikutnya)Molekul air polar Muatan Positif berakhir pada anionMuatan Negatif berakhir pada kation Molekul air membentuk ikatan hidrogen04/12/2012Kimia Lingkungan Air-16Water MoleculeWaters properties can best be understood by considering the structure and bonding of the water molecule:

The water molecule is made up of two hydrogen atoms bonded to an oxygen atom.The three atoms are not in a straight line; instead, as shown above, they form an angle of 105. Because of waters bent structure and the fact that the oxygen atom attracts the negative electrons more strongly than do the hydrogen atoms, the water molecule behaves like a dipole having opposite electrical charges at either end.

The properties of water are due to the polar nature of the water molecule and its ability to form hydrogen bonds.The Water Molecule

04/12/2012Kimia Lingkungan Air-188SIFAT PENTING AIRAir memiliki sifat yang sangat penting karena perannya sebagai:Pelarut, media kehidupan, perilaku lingkungan, dan penggunaan di industri, mengikuti dasar karakteristik molekul air:04/12/2012Kimia Lingkungan Air-19Sifat Air sebagai Senyawa yang UnikSebagai media reaksi kimia, air sangat penting dalam kehidupan makhluk hidupSifat khusus air adalah: bersifat polar, cenderung membentuk ikatan hidrogen serta mampu menghidrasi ion-ion logamSifat air disajikan dalam Tabel 3.1

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Apabila garam NaCl dilarutkan ke dalam air, maka akan dihasilkan ion positif Na+ dan ion negatif Cl-, ion ion positif Na+ dikelilingi oleh molekul air , dimana gugus negatifnya berujung pada ion-ion positif dan anion klorida dikelilingi molekul air dengan gugus positifnya berujung pada ion-ion negatif seperti yang terlihap pada Gambar 3.4. This kind of attraction for ions is the reason why water dissolves many ionic compounds and salts that do not dissolve in other liquids.MOLEKUL AIRPolar water molecules

Ikatan Hidrogen AirSifat kedua dari air adalah kemampuannya membentuk ikatan hidrogen

Ikatan Hidrogen dalam Molekul AirIkatan Hidrogen air membantu agar molekul-molekul solut dan ion-ion berada dalam larutan Hal ini terjadi jika terjadi ikatan Hidrogen yang terbentuk antara molekul air dengan atom hidrogen, nitrogen, oksigen dalam molekul solut (see Figure 3.5). Ikatan Hidrogen juga membantu mengikat partikel-partikel kecil (partikel koloid) tetap dalam bentuk suspensi dalam airSifat Air Sebagai Pelarut yang Baik Sebagai pelarut, molekul air merupakan media transpor dasar untuk nutrisi dan limbah yang dihasilkan dalam proses-proses kehidupanKarena memiliki tetapan dielektrik yang tinggi maka air merupakan pelarut yang baik dan kebanyakan senyawa-senyawa ionik berdissosiasi dalam air menghasilkan ion-ionAir juga memiliki kapasitas panas tertinggi diantara cairan atau padatan (l cal x g-1 x deg-1)

04/12/2012Kimia Lingkungan Air-116Sifat Air Sebagai Pelarut yang Baik Karena tingginya kapasitas panas yang dimiliki air maka untuk mengubah temperatur massa air diperlukan panas cukup besarOleh karena itu badan air bersifat dapat menstabilkan efek temperatur pada daerah geografis berdekatanSifat kapasitas panas dari air mencegah perubahan besar temperatur secara tiba-tiba dalam badan air sehingga melindungi organisme akuatik akibat terjadinya schock tiba-tiba akibat perubahan temperatur air04/12/2012Kimia Lingkungan Air-117Sifat Air Sebagai Pelarut yang Baik Kenyataan sifat air ini menyababkan es mengapung, Yang beruntung konsekuensi dari fakta ini adalah bahwa es mengapung, bahkan tubuh besar beberapa molekul air dapat membeku.Gambaran sirkulasi secara vertikal air danau merupakan faktor penentu senyawa kimia dan biologi yang berada di dalamnya yang sebagian besar dibentuk oleh keunikan hubungan densitas-temperatur molekul air

04/12/2012Kimia Lingkungan Air-118SIFAT PENTING AIRSebagai pelarut yang baik untuk garam, asam, basa, dan Dengan zat yang memiliki atom H, O, dan N mampu membentuk ikatan hidrogenSebagai pelarut dalam cairan biologis, seperti darah atau urinSebagai media mineral dan transportasi mineral terlarut dalam geosfer yang mengangkut nutrisi ke akar tanaman dalam tanahBanyak digunakan dalam industri Air memiliki tegangan permukaan sangat tinggi Cairan air seperti tetes hujan menunjukkan sifat fisk seperti penutup lapisan tipis membran bebek mengapresiasi sifat air karena memungkinkan mereka mengambang diatas permukaan air04/12/2012Kimia Lingkungan Air-119SIFAT PENTING AIRSeekor bebek akan tenggelam dalam air yang ditambahkan deterjen telah untuk menurunkan tegangan permukaan, menyebabkan burung bernasib sangat menyedihkanAir bersifat transparan terhadap cahaya sinar tampak dan UV yang memungkinkan terjadinya fotosintesis pada ganggang di bawah permukaan airAir membeku pada 0oC dan memiliki kerapatan maksimum pada temperatur 4oC, sehingga menyebabkan badan air bertingkat dengan bagian lebih dingin, lapisan padat berada di bagian lebih bawah air

04/12/2012Kimia Lingkungan Air-120Sifat Panas Air yang PentingHigh heat capacity of 4.184 joules per gram per C (J/g-C)Very high heat of fusion of 334 joules per gram (J/g)Very high heat of vaporization of water is 2,259 J/g, water vapor carries latent heat

04/12/2012Kimia Lingkungan Air-121Karakteristik Panas Air yang PentingSifat fisik yang paling penting dari air yang sering diperdebatkan adalah perilaku dengan panas.Air cair memiliki kapasitas panas dari 4,184 joules per gram per C (J / g C), yang berarti bahwa 4,184 joule energi panas yang dibutuhkan untuk menaikkan suhu 1 gramair cair sebesar 1 C. Ini menunjukkan kapasitas panas yang sangat tinggi untuk menstabilkan suhu daerah di dekat badan air. Kapasitas panas tinggi air adalah karena adanya fakta bahwa molekul air sangat terikat bersama oleh ikatan hidrogen04/12/2012Kimia Lingkungan Air-122Karakteristik Panas Air yang PentingBesarnya energi panas diperlukan untuk memecahkan ikatan hidrogen air sehingga molekul air dapat bergerak lebih cepat pada suhu tinggiAir juga memiliki panas fusi sangat tinggi yakni 334 joule per gram (J / g). Ini berarti diperlukan panas yang sangat tinggi untuk memecahkan bagian molekul air yang terikat secara ikatan hidrogen dalam molekul es dalam rangka mengubah es menjadi cairan air

04/12/2012Kimia Lingkungan Air-123Karakteristik Panas Air yang PentingEs yang meleleh, asalkan baik es padat dan air cair berada bersama-sama, maka suhu tetap pada suhu leleh, yaitu suhu konstan pada 0 C. Panas ditambahkan ke sistem digunakan untuk memecah molekul terpisah dalam es padat, bukan untuk meningkatkan suhu.Panas penguapan air adalah 2,259 J/g. Artinya 2.259 joule energi panas yang dibutuhkan untuk menguapkan 1 gram air cairPanas ini merupakan suhu penguapan tertinggi bagi kebanyakan cairan

04/12/2012Kimia Lingkungan Air-124Karakteristik Panas Air yang PentingPanas penguapan ini memiliki pengaruh besar pada badan air dan pada cuaca. Dengan menyerap panas begitu banyak, air berubah dari cair ke uap, Air menstabilkan suhu atmosfer. Namun, panas laten yang terkandung dalam uap airdilepaskan ketika uap mengembun, seperti apa yang terjadi saat hujan. panas yang dilepas ini menghangatkan massa udara menyebabkan massa udara meningkat, yang merupakan kekuatan pendorong di belakang badai dan angin topan.04/12/2012Kimia Lingkungan Air-125Karakteristik Panas Air yang PentingPanas laten dalam bentuk uap air diuapkan darilautan di dekat khatulistiwa yang terbawa menjauh dari khatulistiwa dalam bentuk massa udara dan dilepaskan ketika uap air terkondensasi membentuk hujan.04/12/2012Kimia Lingkungan Air-126Air yang digunakan oleh manusia terutama adalah air permukaan dan air tanahMeskupun sumber air berbeda beda satu sama lainnya secara nyataSecara teoritis air yang dapat digunakan sekitar 4.6 x 1012 liter per hari, atau hanya 23 sentimeter per tahun.Pada saat ini air yang dapat digunakan di USA sekitar 1.6 x 1012 liter per hari, atau 8 sentimeterdari rata-rata curah hujan tahunan .Jumlah ini merupakan kenaikan 10 kali penggunaan dari 1.66 x 1011 liter per hari pada pergantian abad.

04/12/2012Kimia Lingkungan Air-127PENGGUNAAN AIRTrend dalam penggunaan air di U.SAPendorong tren dalam penggunaan air di AS, merupakan hasil dari:upaya konservasi air, terutama di industri dan pertanianDaur ulang air, termasuk penggunaan melalui beberapa tingkatan membutuhkan kualitas air semakin rendahPenggantian irigasi semprot dengan aplikasi langsung dari air untuk tanah termasuk irigasi kontrol penggunaan air04/12/2012Kimia Lingkungan Air-1287.3. WATER DISTRIBUTION AND SUPPLY

04/12/2012Kimia Lingkungan Air-12929conserve waterSince about 1980, however, water use in the U.S. has shown an encouraging trend with total consumption down by about 9% during a time in which populationgrew 16%, according to figures compiled by the U.S. Geological Survey. This trend, which is illustrated in Figure 3.2,4.4. Water Utilization (in U.S.)

04/12/2012Kimia Lingkungan Air-13131conserve waterIt has been attributed to the success of efforts to conserve water, especially in the industrial (including power generation) and agricultural sectors. Conservation and recycling have accounted for much of the decreased use in the industrial sector. Irrigation water has been used much more efficiently by replacing spray irrigators, which lose large quantities of water to the action of wind and to evaporation, with irrigation systems that apply water directly to soil. Trickle irrigation systems that apply just the amount of water needed directly to plant roots are especially efficientDistribution Problem of WaterA major problem with water supply is its nonuniform distribution with location and time. As shown in Figure 3.3, precipitation falls unevenly in the continental U.S.This causes difficulties because people in areas with low precipitation often consume more water than people in regions with more rainfall. Rapid population growth in the more arid southwestern states of the U.S. during the last four decades has further aggravated the problemDistribution Problem of Water

.THE CHARACTERISTICS OF BODIES OF WATERThe physical condition of a body of water strongly influences the chemical and biological processes that occur in water. Surface water occurs primarily in streams, lakes, and reservoirs.Wetlands are flooded areas in which the water is shallow enough to enable growth of bottom-rooted plants. Estuaries are arms of the ocean into which streams flow. The mixing of fresh and salt water gives estuaries unique chemical and biological properties. Estuaries are the breeding grounds of much marine life, which makes their preservation very importantTHE CHARACTERISTICS OF BODIES OF WATER

THE CHARACTERISTICS OF BODIES OF WATERWaters unique temperature-density relationship results in the formation of distinct layers within nonflowing bodies of water, as shown in Figure 3.6. During the summer a surface layer (epilimnion) is heated by solar radiation and, because of its lower density, floats upon the bottom layer, or hypolimnion. This phenomenon is called thermal stratification.THE CHARACTERISTICS OF BODIES OF WATERWhen an appreciable temperature difference exists between the two layers, they do not mix but behave independently and have very different chemical and biological properties. The epilimnion, which is exposed to light, may have a heavy growth of algae. As a result of exposure to the atmosphere and (during daylight hours) because of the photosynthetic activity of algae, the epilimnion contains relatively higher levels of dissolved oxygen and generally is aerobic. In the hypolimnion, bacterial action on biodegradable organic material may cause the water to become anaerobic (lacking dissolved oxygen). As a consequence, chemical species in a relatively reduced form tend to predominate in the hypolimnion.THE CHARACTERISTICS OF BODIES OF WATERThe shear-plane, or layer between epilimnion and hypolimnion, is called the thermoclineDuring the autumn, when the epilimnion cools, a point is reached at which the temperatures of the epilimnion and hypolimnion are equal. This disappearance of thermal stratification causes the entire body of water to behave as a hydrological unit, and the resultant mixing is known as overturn. An overturn also generally occurs in the spring. During the overturn, the chemical and physical characteristics of the body of water become much more uniform, and a number of chemical, physical, and biological changes may result. Biological activity may increase from the mixing of nutrients. Changes in water composition during overturn may cause disruption in water-treatment processes.BADAN AIR DAN KEHIDUPAN DI AIRStratifikasi thermal badan air menunjukkan sifat sebagai berikut:Pada lapisan bagian atas badan air (lapisan epilimnion) lebih hangat, kurang padat, kaya oksigendan lapisan lebih bawah (hypolimnion) , dingin lebih padat, dan miskin oksigen (Gambar 7.4) sangat mempengaruhi kimia dan biologi airLapisan Epiliminion sering mendukung tinggipertumbuhan alga secara fotosintetikLapisan epilimnion yang kaya oksigen umumnya mengandung konsentrasi tinggi spesies kimia teroksidasi, yang biasanya memiliki kandungan oksigen yang tinggi, misal: CO2 dan HCO3-untuk karbon, NO3 untuk nitrogen, dan SO42- untuk sulfur

04/12/2012Kimia Lingkungan Air-140BADAN AIR DAN KEHIDUPAN DI AIRLapisan hypolimnion sering kekurangan O dan cenderung mengandung senyawa kimia cenderung tereduksi mengurangi isi species dengan kandungan oksigen rendah dan H tinggi, termasuk CH4, NH3 (atau NH4 +), dan H2S masing-masing untuk karbon, nitrogen, dan beleran Di bawah kondisi reduksi lapisan hypolimnion, besi dapat hadir sebagai Fe larut, sedangkan di hypolimnion itu ada apadatan Fe(OH)3 atau Fe2O304/12/2012Kimia Lingkungan Air-141BADAN AIR DAN KEHIDUPAN DI AIR

04/12/2012Kimia Lingkungan Air-142Sources and Uses of Water: The Hydrologic CycleThe worlds water supply is found in the five parts of the hydrologic cycle(Figure 3.1). About 97% of Earths water is found in the oceans. Another fraction is present as water vapor in the atmosphere (clouds). Some water is contained in the solid state as ice and snow in snowpacks, glaciers, and the polar ice caps. Surface water is found in lakes, streams, and reservoirs. Groundwater is located in aquifers underground.

04/12/2012Kimia Lingkungan Air-14444The Hydrologic Cycle:There is a strong connection between the hydrosphere, where water is found, and the lithosphere, which is that part of the geosphere accessible to water. Human activities affect both.For example, disturbance of land by conversion of grasslands or forests to agricultural land or intensification of agricultural production may reducevegetation cover, decreasing transpiration (loss of water vapor by plants) and affecting the microclimate. The result is increased rain runoff, erosion, and accumulation of silt in bodies of water. The nutrient cycles may be accelerated, leading to nutrient enrichment of surface waters. This, in turn, can profoundly affect the chemical and biological characteristics of bodies of water.Where Earths Water is FoundAbout 97% of Earths water is in oceansMost of the remaining water is in the form of solid snow and iceLess than 1% of Earths water as water vapor and clouds in the atmosphere, as surface water in lakes, streams, and reservoirs, and as groundwater in underground aquifers46

7.4. Bodies of Water and Life in WaterStratification of a Body of Water Strongly Affects Chemical and Biological Processes47Living Organisms inWaterSebuah badan air normal akan menyediakan habitat bagi sejumlah besar organisme mulaidari bersel tunggal ganggang sampai ikan. Sehingga badan air dapat dianggap sebagai sebuah ekosistem,biasanya didasarkan pada pasokan makanan yang terdiri dari biomassa yang dihasilkan secara photosynthetic oleh ganggang dan tanaman yang hidup di dalamnya:

04/12/2012Kimia Lingkungan Air-148Biologically Mediated Processes in WaterSpecialized bacteria in water can utilize oxidized chemical species with high oxygen contents other than molecular O2 for oxygen sources.Example: Nitrate ion, NO3-, acts as an oxidizing agent in the bacterially-mediated biodegradation of biomass: C6H12O6 + 3NO3- + 6H+ 6CO2 + 3H2O + 3NH4+ (7.4.3)By mediating chemical reactions, such as the one above, microorganisms, particularly bacteria, largely determine the chemistry that occurs in water.Dissolved oxygen in water is very important.Biodegradable organic pollutants cause biochemical oxygen demand, BOD.497.5. CHEMICAL PROCESSES IN WATERBiochemical processes including photosynthesis 2HCO3- (sunlight energy) {CH2O} + O2 + CO32- (7.5.1) {CH2O} represents biomassAcid-base reactions CO32- + H2O HCO3- + OH- (7.5.2)Precipitation reactions Ca2+ + CO32- CaCO3(s) (7.5.3)Oxidation-reduction reactions, usually carried out by bacteria are generally ones in which chemical species gain or lose oxygenExample: Oxidation of S in H2S H2S + 2O2 SO42- + 2H+ (7.5.4)50CHEMICAL PROCESSES IN WATERMany chemical and biochemical reactions occur in water in the environment. Theseare discussed here on the basis of their chemical classification. Several of these were shown by example reactions in Figure 7.41. The photosynthesis reaction, which utilizes sunlight energy to produce biomass,

04/12/2012Kimia Lingkungan Air-151CHEMICAL PROCESSES IN WATERis shown here for the conversion of inorganic carbon from dissolved HCO3- ion to organic carbon (biomass) abbreviated as {CHO}. This reaction produces biomass that can be acted upon biochemically by other organisms to form the basis of a number of important biochemical processes in water04/12/2012Kimia Lingkungan Air-152CHEMICAL PROCESSES IN WATER2. The carbonate ion, CO32-generated by photo-synthesis reacts with water

removing a hydrogen ion, H, from the water molecule and producing OH- ion. Reactions involving the exchange of H+ or the generation or consumption of OH- are acid-base reactions. This reaction generates OH- ion, so it makes the water more basic.The carbonate ion generated by photosynthesis may become involved in another kind of reaction as exemplified by its reaction with dissolved calcium ion, Ca 2+, in water, to produce solid CaCO3

04/12/2012Kimia Lingkungan Air-153CHEMICAL PROCESSES IN WATERThis is a precipitation reaction. CaCO3 is limestone, and it is this kind of reaction, beginning with the CO32- generated by photosynthesis, that is responsible for large formations of limestone rock throughout the world.3. Oxidation-reduction reactions (see Section 4.7), usually carried out by bacteria,are common in natural waters. The bacterially-mediated reaction of sulfate ion, SO42- acting as an oxidizing agent in the O2 -deficient bottom regions of a body of water to oxidize biodegradable organic matter, {CH2O}04/12/2012Kimia Lingkungan Air-154CHEMICAL PROCESSES IN WATERReaksi :

is one in which the sulfate ion loses oxygen (is reduced). As the H2S gas bubbles up through the water, it may contact molecular oxygen and other kinds of bacteria that cause it to undergo the following reaction in which the sulfur is oxidized with the addition of oxygen atoms to produce SO42-ion:

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7.6. FIZZY WATER FROM UNDERGROUNDNatural waters contain dissolved gases. Dissolved oxygen required by fish Dissolved carbon dioxide in some mineral watersCarbon dioxide in Lake Nyos in the African country of Cameroon which asphyxiated 1,700 people in 1986Henrys Law for gas solubilities states that the solubility of a gas in a liquid is proportional to the partial pressure of that gas in contact with the liquid. Gas solubility decreases with increasing temperature56Oxygen in WaterAt 25 C the concentration of oxygen dissolved in water is only about 8 milligrams per liter of water (mg/L)Readily consumed by biodegradation of biomass (abbreviated {CH2O}) by oxygen-utilizing bacteria:{CH2O} + O2 CO2 + H2O (7.6.1)Only about 8 mg of {CH2O} consumes 8 mg of O2577.7. (WEAK) ACID FROM THE SKYAn acid is a substance that contains or produces H+ ion in water, whereas a base is a substance that accepts H+ ion in water or contains or produces hydroxide ion, OH-Whether water is acidic or basic is expressed by pH: pH = -log [H+] (7.7.1)[H+] is the molar concentration of H+ in water, that is, the number of moles of this ion per liter of water.[H+], mol/Llog[H+]pH 0.100-1.001.001.00 10-3-3.003.001.00 10-5-5.005.001.00 10-9-9.009.0058Acid in Water (Continued)The value of [H+] in pure water at 25 C is 1.00 10-7 mol/L and the pH is 7.00.The concentration of dissolved carbon dioxide, [CO2(aq)], in water in equilibrium with 370 ppm atmospheric air at 25 C is 1.21 10-5 mol/L.Makes water slightly acidic because CO2 + H2O H+ + HCO3- (7.7.2)[H+] = 2.3 10-6 mol/L corresponding to a slightly acidic pH of 5.6Such water is neutral, neither acidic nor basic.Water with a pH less than 7.00 is acidic, whereas water with a pH greater than 7.00 is basic.The average global concentration of CO2 gas in air in the year 2001 was about 370 parts per million by volume, and going up by about 1 ppm per year.597.8. WHY NATURAL WATERS CONTAIN ALKALINITY AND CALCIUMWater alkalinity is the ability of water to react with and neutralize acid (H+).Due to presence of bicarbonate ion, HCO3-, which can react as follows with H+ ion: HCO3- + H+ CO2(aq) + H2O (7.7.3)Water hardness in the form of dissolved Ca2+ ionBoth water hardness and alkalinity are acquired when water containing dissolved CO2 reacts with limestone, CaCO3: CO2(aq) + CaCO3(s) + H2O Ca2+(aq) + 2HCO3- (7.7.4)60Atmospheric CO2 dissolved in water, and from biodegradationHCO3- dissolved in waterSolid carbonates (CaCO3) in mineral formations in contact with waterCarbon Dioxide and Carbonate Species in Water

617.9. METALS IN WATERMetal ions in water are present as hydrated ions, such as Ca(H2O)62+.Bound water molecules can be displaced reversibly by other species.Such species include chelating agents, which can bond to metal ions in 2 or more places to form a metal chelate.One such chelating agent is the nitrilotriacetate anion used in some cleaning formulations and capable of bonding to a metal ion on 4 separate sitesChelates tend to be particularly stable, and they are very important in natural water systems.Chelates are involved in life systems; for example, blood hemoglobin is a chelate that contains Fe2+ ion bonded simultaneously to 4 N atoms on the hemoglobin protein molecule62Humic Substances in WaterWater in nature may contain naturally-occurring chelating agents called humic substances that are complex molecules of variable composition left over from the biodegradation of plant material.Humic substances bind with Fe2+ ion to produce gelbstoffe (German for yellow stuff) which is very difficult to remove by water treatment processes.Humic substances produce trihalomethanes, such as chloroform, HCCl3 during disinfection of water by chlorine63Most important chemical and biochemical processes in water occur at interfaces between water and another phase (usually solid)7.10. Water Interactions With Other Phases

64Sediments are variable mixtures of minerals, clay, silt, sand, and organic matter Formed by Erosion Sloughing of banks into water Washed in from watershedsChemical reactions, for example, as the result of photosynthesis: Ca2+ + 2HCO3 - + h {CH2O}(s) + CaCO3(s) + O2(g) Deposits solid CaCO3 (limestone) Deposits biomass, {CH2O}Sediments65Very small particles suspended in waterSize ranging from very large molecules up to about 1mScatter light (Tyndall effect)Unique characteristics High surface/volume High interfacial energy High surface/chargeColloids in Water

66Behavior and stability of colloids are important in aquatic chemical phenomena Formation of sediments Dispersion and agglomeration of bacterial cells Dispersion and removal of pollutants Waste treatment processes67AQUATIC LIFEThe living organisms (biota) in an aquatic ecosystem may be classified as either autotrophic or heterotrophic. Autotrophic organisms utilize solar or chemical energyto fix elements from simple, nonliving inorganic material into complex life molecules that compose living organisms. Algae are the most important autotrophic aquatic organisms because they are producers that utilize solar energy to generate biomass from CO2 and other simple inorganic species.AQUATIC LIFEHeterotrophic organisms utilize the organic substances produced by autotrophic organisms as energy sources and as the raw materials for the synthesis of their own biomass. Decomposers (or reducers) are a subclass of the heterotrophic organisms and consist of chiefly bacteria and fungi, which ultimately break down material of biological origin to the simple compounds originally fixed by the autotrophic organisms.AQUATIC LIFEThe ability of a body of water to produce living material is known as its productivity.Productivity results from a combination of physical and chemical factors.High productivity requires an adequate supply of carbon (CO2), nitrogen (nitrate), phosphorus (orthophosphate), and trace elements such as ironWater of low productivity generally is desirable for water supply or for swimming.AQUATIC LIFERelatively high productivity is required for the support of fish and to serve as the basis of the food chain in an aquatic ecosystem. Excessive productivity results in decay of the biomass produced, consumption of dissolved oxygen, and odor production, a condition called eutrophicationAQUATIC LIFELife forms higher than algae and bacteriafish, for examplecomprise a comparatively small fraction of the biomass in most aquatic systems. The influence of these higher life forms upon aquatic chemistry is minimal. However, aquatic life is strongly influenced by the physical and chemical properties of the body of water in which it lives. Temperature, transparency, and turbulence are the three main physical properties affecting aquatic life. Very low water temperatures result in very slow biological processes, whereas very high temperatures are fatal to most organisms. The transparency of water is particularly important in determining the growth of algae.Turbulence is an important factor in mixing processes and transport of nutrients and waste products in water. Some small organisms (plankton) depend upon water currents for their own mobility.Dissolved oxygen (DODissolved oxygen (DO) frequently is the key substance in determining the extent and kinds of life in a body of water. Oxygen deficiency is fatal to many aquatic animals such as fish. The presence of oxygen can be equally fatal to many kinds of anaerobic bacteria. Biochemical oxygen demand, BOD, discussed as a water pollutant, refers to the amount of oxygen utilized when the organic matter in a given volume of water is degraded biologically.Carbon dioxideCarbon dioxide is produced by respiratory processes in water and sediments and can also enter water from the atmosphere. Carbon dioxide is required for the photosynthetic production of biomass by algae and in some cases is a limiting factor.High levels of carbon dioxide produced by the degradation of organic matter in water can cause excessive algal growth and productivity.The salinity of water also determines the kinds of life forms present. Irrigation waters may pick up harmful levels of salt. Marine life obviously requires or tolerates salt water, whereas many freshwater organisms are intolerant of salt.04/12/2012Kimia Lingkungan Air-175Thank you for your attention