Water Technology

Water Technology

• Water technology encompasses the study and application of scientific and engineering principles to manage, treat, and utilize water resources. It involves understanding water quality parameters, adhering to established standards, conducting thorough analysis, and implementing effective management strategies to ensure water is safe and suitable for various purposes.

Water Sources & Consumption

• Surface Water:

  • Rain Water: Naturally pure as it originates from atmospheric condensation but becomes contaminated upon contact with atmospheric gases and pollutants. Collection methods and storage significantly affect its quality.

  • River Water: Contains a high load of dissolved salts and minerals due to runoff from soil and rocks. Organic matter and pollutants from urban and agricultural areas also contribute to its composition.

  • Lake Water: Typically has a more constant composition compared to rivers, but often contains higher concentrations of organic matter from decaying plant and animal life, leading to potential eutrophication.

  • Sea Water: Characterized by high salinity and the presence of pathogens and organic compounds, making it unsuitable for direct consumption or many industrial applications without extensive treatment.

• Underground Water:

  • Spring/Well Water: Generally has high dissolved salts from prolonged contact with subsurface minerals. Naturally filtered through soil layers, it is usually free from organic contaminants but may require treatment for hardness or specific dissolved minerals.

• Consumption:

  • Drinking: Water must meet stringent purity standards to ensure it is safe for human consumption, free from harmful pathogens and toxic chemicals.

  • Household: Includes water used for cleaning, cooking, sanitation, and personal hygiene. Quality requirements vary but generally need to be free from contaminants that could affect health or aesthetics.

  • Industrial: Water is used for cooling, cleaning, processing, and as a raw material. Quality requirements vary widely depending on the specific industry and application.

Water Quality Parameters

• Water quality determines the 'goodness' of water for particular purposes, reflecting its suitability for specific uses such as drinking, agriculture, or industrial processes. These parameters provide a comprehensive assessment of water's characteristics.

• It includes physical, chemical, and biological characteristics that define its condition. These characteristics interact and influence each other, affecting the overall quality and usability of the water.

• Key parameters include:

  • Temperature: Influences biological activity and chemical reactions in water.

  • pH: Measures the acidity or alkalinity, affecting the solubility and bioavailability of chemical constituents.

  • Salinity: Indicates the concentration of dissolved salts, influencing aquatic life and the suitability for irrigation.

  • Total Dissolved Solids (TDS): Represents the total amount of dissolved substances in water, affecting taste and usability.

  • Hardness: Measures the concentration of calcium and magnesium ions, which can cause scaling and affect soap's effectiveness.

  • Turbidity: Indicates the cloudiness or haziness caused by suspended particles, affecting light penetration and aesthetics.

  • Dissolved Oxygen: Essential for aquatic life, indicating the water's ability to support aerobic organisms.

  • Nutrients: Nitrogen and phosphorus compounds that can promote excessive plant growth.

  • Dissolved Organic Matter: Organic compounds from natural and synthetic sources that can affect water color, taste, and disinfection effectiveness.

  • Dissolved Inorganic Matter: Inorganic compounds such as metals and minerals that can affect water quality and toxicity.

  • Microorganisms: Bacteria, viruses, and protozoa that can pose health risks if present in high numbers.

1. Temperature

• Affects dissolved oxygen levels; lower temperatures hold more oxygen, critical for sustaining aquatic life.

• Example:

  • 0°C water holds up to 14.6 mg/L of oxygen

  • 30°C water holds only up to 7.6 mg/L.

• Influences the rate of photosynthesis, metabolic rates, reproduction cycles, and the sensitivity of aquatic life to toxins. Temperature changes can disrupt aquatic ecosystems.

2. pH

• Measures acidity or alkalinity, reflecting the concentration of hydrogen ions (H+) in water.

• Scale: 0-6.9 (Acidic), 7 (Neutral), 7.1-14 (Alkaline). The pH scale is logarithmic, meaning each unit change represents a tenfold difference in acidity or alkalinity.

• Optimal ranges:

  • 6.5-8 for freshwater, supporting a diverse range of aquatic organisms.

  • 8-9 for estuarine and sea water, reflecting the natural buffering capacity of marine environments.

• Extreme pH values can harm aquatic fauna, causing skin irritations, ulcers, and impaired gill function. Death may occur in extremely acidic or alkaline conditions by disrupting cellular functions and physiological processes.

3. Salinity

• Measures dissolved salts, often expressed as Total Dissolved Solids (TDS). Salinity affects water density, osmotic pressure, and the solubility of gases.

• Appropriate salt concentrations are vital for aquatic life; excess salinity causes stress or death by disrupting osmotic balance and physiological functions.

• Affects nutrient availability to plant roots by altering soil structure and water uptake mechanisms.

• Water with TDS above 500 mg/L is unsuitable for irrigation and tastes unpleasant, affecting crop yields and consumer satisfaction.

4. TDS Values

• Ideal Drinking Water:

  • 0-50 ppm: Water from reverse osmosis, deionization, carbon filtration, microfiltration, mountain springs, or distillation. This level indicates high purity and minimal dissolved substances.

• Average Tap Water

  • Ranges from mountain springs or aquifers being ideal to hard water (170 ppm) to marginally acceptable average tap water, up to high TDS water from tap or mineral springs. Wide variability due to source water quality and treatment processes.

• EPA Maximum Contamination Level

  • 500+ ppm: Indicates potential contamination and aesthetic concerns.

• Tolerance levels for plants and animals:

  • 0 - 500 mg/L: Suitable for Humans, Lettuce, Potatoes, Peas, Celery etc., supporting healthy growth and physiological functions.

  • 500 - 1500 mg/L: Tolerated by Mulberry, Apple, Cauliflower, Cabbage, Tomato, Poultry, Oats etc., with some potential for reduced yields or growth rates.

  • 1500 - 3500 mg/L: Accommodates Wheat, Rye, Lucerne, Sweet corn., though may require adaptive management strategies.

  • 3500 - 6,000 mg/L: Used for Millet, Pigs, Horses, Dairy cows, Ewes with lambs., but careful monitoring is needed to prevent adverse effects on animal health.

  • 6,000 - 10,000 mg/L: Tolerated by Beef cattle. Requires specific adaptation and management.

  • 3500 - 6,000 mg/L: Supports Seashore paspalum, Saltwater couch, Date palm, Salt sheoaks., adapted to high-salinity environments.

5. Turbidity

• Measures water murkiness, indicating suspended solids. High turbidity reduces water clarity and affects light penetration.

• Sources of suspended solids: soil erosion, sewage effluent, industrial discharge. These sources introduce particulate matter into water bodies.

• Naturally occurring sources: bank and channel erosion accelerated by human activity. Human activities exacerbate natural erosion processes.

• Causes:

  • Silt, sand, and mud

  • Bacteria and germs

  • Chemical precipitates

• Suspended sediments can:

  • Smother aquatic plants by reducing light penetration

  • Clog mouthparts and gills of aquatic organisms, impairing respiration and feeding

  • Prevent sufficient light for photosynthesis, disrupting aquatic ecosystems

Measurement of Turbidity

• Turbidimeter: Measures light intensity transmitted through a water sample, compared to a formazin standard, expressed as Formazin Turbidity Units (FTU). Measures the reduction in light transmitted through the sample.

• Nephelometer: Measures light scattered by the water sample at right angles, expressed as Nephelometric Turbidity Units (NTU). More sensitive to low levels of turbidity.

Importance of Measuring Turbidity

• Essential for domestic water supplies due to treatment process effects. High turbidity complicates disinfection and filtration processes.

• High turbidity can block filters during rainy seasons, increasing maintenance and reducing water supply efficiency.

• Can fill tanks and pipes with mud and silt, damaging valves and taps, leading to infrastructure problems.

• Interferes with chlorination efficiency by shielding pathogens from the disinfectant.

• Some treatment systems (sedimentors, coagulators, gravel pre-filters) are designed to remove turbidity to improve water quality.

6. Dissolved Oxygen (DO)

• Indicates water's overall health; high levels suggest low pollution, supporting a thriving aquatic ecosystem.

• Required by aquatic fauna for survival; low oxygen causes death through suffocation and disruption of metabolic processes.

7. Nutrients

• Main plant nutrients: nitrogen and phosphorus. These nutrients stimulate plant and algal growth.

• Phosphates Sources:

  • Sediments from rocks and soil: Natural weathering releases phosphates

  • Wastewater treatment effluent: Contains phosphates from human waste and detergents

  • Sewage disposal units: Septic systems and sewage leaks can introduce phosphates

  • Detergents and fertilizers: Major sources of phosphate pollution

• Nitrates Sources:

  • Fertilizers: Agricultural runoff is a primary source

  • Stock manure: Animal waste contains high levels of nitrates

  • Soil bacteria decomposing organic matter: Natural process that releases nitrates

Effects of High Nutrient Levels

• Water bodies choked with vegetation/algae due to eutrophication, leading to algal blooms and excessive plant growth

• Changes in aquatic flora and fauna composition, potentially leading to monoculture and reduced biodiversity

• Increased dissolved oxygen fluctuations, stressing aquatic fauna as oxygen levels swing between supersaturation and hypoxia

• Increased organic load, causing odors and reduced aesthetic quality, making water less appealing and usable

8. Dissolved Organic Impurities

• From decay of vegetable matter, paper, domestic and industrial wastes. Sources include both natural and anthropogenic activities.

• Include detergents, oils, fats, pesticide and herbicide residues. These contaminants can have toxic effects on aquatic life and human health.

9. Dissolved Inorganic Impurities

• From water percolating through soil. Natural geochemical processes contribute to the presence of these impurities.

• Include carbon dioxide, sodium salts, silicates, ferrous and ferric compounds, aluminum (from dosing chemicals and minerals), phosphates (from detergents), and nitrates (from fertilizers). These substances can affect water's taste, color, and safety.

10. Micro-organisms

• Include amoeba, bacteria, paramecia, rotifers, and algae present on surface waters. These organisms can indicate fecal contamination and potential health risks.

Drinking Water Standards

• Quality parameters set to protect public health. These standards define acceptable levels of contaminants and ensure water is safe for consumption.

• Organizations setting standards:

  • World Health Organization (WHO): Provides international guidelines

  • Central Pollution Control Board (CPCB): Sets standards in India

  • Indian Council of Medical Research (ICMR): Contributes to health-related standards in India

  • United States Environmental Protection Agency (USEPA): Enforces drinking water standards in the USA

Drinking Water Specification Agencies

• Bureau of Indian Standards (2012)

• United States Environmental Protection Agency (US-EPA): Safe Drinking Water Act (1974).

• European Union Drinking Water Regulation (2014)

• Guidelines of Drinking Water Quality, Health Protection Agency, United Kingdom (2009).

• National Standards for Republic of China (GB 5749-2006).

• American Public Health Association (APHA) (1872).

Permissible Limits of Drinking Water Quality

*A table of parameters including pH, Turbitity, Conductivity, Alkalinity, Total hardness, Iron, Chlorides, Nitrate, Sulfate, Residual free Chlorine, Calcium, Magnesium, Copper, Fluoride, Mercury, Cadmium, Selenium, Arsenic, Lead, Zinc, Chromium, E. Coli with permissible limits defined by USEPA, WHO, ISI, ICMR and CPCB

International Standard for Drinking Water

• Water intended for human consumption must be free from chemical substances and micro-organisms in amounts which would provide a hazard to health. This ensures the water is safe and does not pose any risks to human health.

• Supplies of drinking-water should not only be safe and free from dangers to health, but should also be as aesthetically attractive as possible. Aesthetic qualities such as taste, odor, and appearance are important for consumer acceptance.

• Absence of turbidity, color and disagreeable or detectable tastes and odors is important in water-supplies intended for domestic use. These characteristics contribute to the overall acceptability of drinking water.

• The location, construction, operation and supervision of a water-supply-its sources, reservoirs, treatment and distribution-must exclude all potential sources of pollution and contamination. Proper management and protection of water sources are essential to prevent contamination.

Indian Standard Drinking Water Specification

• IS 10500:2012 This standard was originally published in 1983.

• Based on report prepared by WHO that in 1975, some 1230 million people were without safe water supplies. Highlighting the global need for safe water.

• United Nations decision to declare an International Drinking Water Supply and Sanitation decade, beginning in 1981. To raise awareness and promote improvements in water and sanitation.

• Sixth Five-Year Plan of India had made a special provision for availability of safe drinking water for the masses. Addressing water scarcity and quality issues in India.

• Formulated with the objective of assessing the quality of water resources, and to check the effectiveness of water treatment and supply by the concerned authorities. Ensuring water quality through monitoring and treatment.

• As per the eleventh five year plan 2. 17 lakh quality affected habitations with more than half affected with excess iron, followed by fluoride, salinity, nitrate and arsenic in that order. Identifying prevalent water quality issues in India.

• Approximately 10 million cases of diarrhoea, more than 7.2 lakh typhoid cases and 1.5 lakh viral hepatitis cases contribute to the uncleanliness of the waters. Disease related to unclean water are a severe public health issue.

Definition of Drinking Water & Requirements

• Drinking water shall comply with the requirements given in Tables 1 to 4. These tables specify the acceptable levels of various parameters.

• Drinking water shall also comply with bacteriological requirements, virological requirements and biological requirements. Ensuring water safety from harmful microorganisms.

Drinking Water Specifications

• Total dissolved solids: 500 mg/L (acceptable), 2000 mg/L (permissible). High TDS can affect taste and usability.

• Total hardness (as $CaCO_3$): 200 mg/L (acceptable), 600 mg/L (permissible). Hardness affects soap's effectiveness and can cause scaling.

• Chloride (as Cl): 250 mg/L (acceptable), 1000 mg/L (permissible). High chloride levels can indicate pollution.

• Fluoride (as F): 1 mg/L (acceptable), 1.5 mg/L (permissible). Fluoride is added to prevent dental cavities but excessive levels can be harmful.

• Iron (as Fe): Max. No relaxation permitted. Iron can cause discoloration and affect taste.

• Free from toxic substances (cadmium, mercury, lead, cyanide, molybdenum, chromium, nickel, arsenic). These substances are harmful even in small amounts.

• Free from pesticide residue. Pesticides can have adverse health effects.

• Free from radioactive materials. Radioactive materials pose a long-term health risk.

• Free from E. coli and coliform bacteria. These indicate fecal contamination and the potential presence of pathogens.

Water Quality Parameters & Measurement

• pH: Measured using pH meters

• Turbidity: Measured using turbidimeters or nephelometers

• Dissolved Oxygen (DO): Measured using DO meters

• Biological Oxygen Demand (BOD): Measured through laboratory incubation

• Chemical Oxygen Demand (COD): Measured through chemical oxidation

• Chloride, fluoride, oil and fats: Measured using specific ion electrodes and extraction methods

• Hardness (EDTA method): Determined through complexometric titration

• Nutrients (N, P), nitrate, dissolved metals: Measured using spectrophotometry and atomic absorption spectroscopy

Hardness Of Water

• Hardness in water is that characteristic, which “ prevents the lathering of soap”. When soap is mixed with, it does not form lather or foam, it forms white scum or precipitate

• $2 C{17}H{35}COONa + Ca^{2+} (C{17}H{35}COO)_2Ca + 2 Na^+$

• sodium soap (water soluble) hardness causing ion calcium soap (water insoluble)

Types Of Hardness

• Temporary / Carbonate / Alkaline Hardness:

  • Attributed to the presence of bicarbonates of Ca and Mg.

  • Can be removed by boiling the water.

  • $Ca (HCO3)2 CaCO3 CO2 H_2O$

  • $Mg (HCO3)2 Mg (OH)2 2CO2$

• Permanent / Non carbonate / Non Alkaline Hardness

  • Attributed to the presence of chlorides and sulphates of primarily Ca and Mg and to a minor extent of Fe and other heavy metals.

  • Cannot be removed by boiling the water.

  • Removal: addition of chemicals, large-scale softening with zeolite, ion exchange resins, reverse osmosis

Units of Hardness

• Hardness of water is the net amount of hardness causing impurities present in a finite volume.

• The concentration of dissolved impurities is usually expressed in terms of $CaCO_3$ equivalent.

• The choice of $CaCO_3$ is accepted universally because its molecular weight is 100 and is the most insoluble salt in water.

CaCO3 Equivalence Conversion

Units Of Hardness

• Parts Per million

• Degree Clark (°CI)

• Degree french (°Fr)

• meq/L

Conversion Factors For Hardness

• 1 ppm = 1 mg/L

• 1 ppm = 0.07°Cl

• 1 ppm = 0.02 meq/L

• 1 ppm = 0.1°Fr

EDTA

• What is EDTA? Ethylene Diamine Tetra Acetic Acid (EDTA). Disodium salt of EDTA.

• Determination of Hardness of water by EDTA method.

Determination of Hardness of water by EDTA method

• It is a Complexometric Titration.

• Complexometric titrations are based on the formation of a complex between the analyte and the titrant. The chelating agent EDTA is commonly used to titrate metal ions in solution.

• EDTA is one of the most common chelating agents used for complexometric titrations in analytical chemistry.

• Disodium salt of EDTA complexes with $Ca^{2+}$ and $Mg^{2+}$ ions are present in hard water to form a stable complex.

• Disodium salt of EDTA solution in water can be used as a standard solution for estimating the hardness of water.

• Hard water is titrated against standard EDTA solution using Erichrome Black –T (EBT) indicator

• EBT (Blue color solution) EBT complex with $Mg^{2+}$ (wine red solution).

• When EBT is Sodium 1-[1-Hydroxynaphthylazo]-6-nitro-2-naphthol-4-sulfonate added to hard water EBT forms an unstable wine-red color complex with Ca and Mg ions at pH 10. (Buffer)

• $Ca^{2+} + [HIn]^{2-} [CaIn]^- + H^+$ (wine red unstable complex)

• $Mg^{2+} + [HIn]^{2-} [MgIn]^- + H^+$ (wine red unstable complex)

• When EDTA is added into the hard water, the metal ions form a stable metal complex with EDTA by leaving the EBT indicator. When all the metal ions are taken by EDTA from the indicator metal ion complex, the wine red color changes into blue, which indicates the end point.

• $[CaIn]^-(aq) + H_2EDTA^{2-}(aq) [CaEDTA]^{2-}(aq) + H^+(aq) + [HIn]^{2-}(aq)$

• (Colorless) (blue)

• $[MgIn]^-(aq) + H_2EDTA^{2-}(aq) [MgEDTA]^{2-}(aq) + H^+(aq) + [HIn]^{2-}(aq)$

• (Colorless) (blue)

• Both, the $[MIn]^−$ and $[MEDTA]^{2−}$ complexes are formed only in alkaline medium. However, in highly alkaline medium $Mg^{2+}$ gets precipitated as $Mg(OH)_2$ and therefore complexation reaction is studied around pH 10 only.

Disadvantages of Hard Water

• It is harmful for drinking . It results in the deposition of calcium in bone joints.

• It cause scale formation in boilers and pipes

• The blockage of passage occurs when water is used for cooling, due to scale deposition

• It does not form lather with soap or detergent

Advantages of Hard Water

• It tastes better due to the presence of calcium and magnesium ions.

• It provides useful calcium ions for the healthy growth of bones and teeth.

• The formation of lime scale in pipes due to hard water causes the inside of the pipe to be covered with insoluble carbonates. It prevents the contact of water with metal so prevents the pipe corrosion and poisonous metal salts becoming dissolved in water.