Engineering Chemistry: Water Chemistry and Impurities

• Engineering chemistry applies chemical principles to engineering problem-solving.
• Engineers gain a fundamental understanding of chemical processes in projects through engineering chemistry.
• Engineering chemistry includes materials science, corrosion, fuels, polymers, water/environmental chemistry.
• Engineers design safe, efficient, and sustainable materials, processes, and products thanks to it.
• Industries like manufacturing, construction, energy, and transportation rely on it.

Water Chemistry

• Water chemistry studies composition/properties, compounds, ions, and gases in water.
• Water's source, environment, and human activities influence its chemistry
• Water treatment, environmental monitoring, and industrial processes rely on understanding water chemistry.
• Monitoring and controlling chemical parameters is key to water quality and safety.
• Key parameters: pH, alkalinity, hardness, dissolved oxygen, ions, and contaminants.

Water Impurities

• Water impurities are classified as suspended, colloidal, dissolved, or biological.
• Suspended impurities include visible particles like sand, clay, and organic matter.
• Colloidal impurities are tiny particles dispersed in water like silica and some organic compounds.
• Dissolved impurities are fully dissolved substances like salts, minerals, and gases.
• Biological impurities include bacteria, viruses, algae, and microorganisms.
• Impurities impact water quality/safety, necessitating treatment for various uses.

Water Quality Parameters

• pH measures water's acidity/alkalinity, ranging 0-14 (7 is neutral).
  • pH below 7 is acidic, above 7 is alkaline and impacts substance solubility
  • Also influences disinfection effectiveness.
• Alkalinity measures the ability to neutralize acids.
  • Primarily from bicarbonate, carbonate, and hydroxide ions.
  • It buffers pH changes and is important for aquatic life.
• Hardness measures calcium/magnesium ions, expressed as mg/L of CaCO3.
  • Hardness causes pipe scaling and reduces soap/detergent effectiveness.
  • Water is classified by hardness level: soft, moderately hard, hard, or very hard.
• Dissolved Oxygen (DO) is the oxygen gas amount in water and vital for aquatic life.
  • Temperature, salinity, and organic matter affect DO levels.
  • Pollution or eutrophication is indicated y low DO.
• Chemical Oxygen Demand (COD) measures oxygen needed to oxidize organic compounds.
  • It assesses water's organic pollution.
  • Higher COD signifies more organic matter.
• Biochemical Oxygen Demand (BOD) measures oxygen microorganisms consume when decomposing organic matter.
  • It indicates organic pollution.
  • BOD is often measured over 5 days (BOD5).
• Conductivity measures water's ability to conduct electricity.
  • Related to ion concentration, to estimate total dissolved solids (TDS).
• Turbidity measures cloudiness/haziness from suspended particles.
  • High turbidity reduces light penetration, affecting aquatic life.
  • It can also make water unappealing.

Water Treatment Processes

• Water treatment removes impurities for safe use.
• Sedimentation removes suspended solids by settling.
• Coagulation/flocculation destabilize colloidal particles, forming removable clumps.
• Filtration removes impurities via filter media like sand, gravel, or activated carbon.
• Disinfection kills/inactivates pathogens using chlorination, ozonation, or UV radiation.
• Water softening removes hardness ions via chemical precipitation, ion exchange, or membrane filtration.
• Adsorption removes dissolved organics by binding them to materials like activated carbon.
• Membrane filtration separates water from impurities using semi-permeable membranes.
  • Common processes: reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), microfiltration (MF).
• Aeration increases dissolved oxygen and removes volatile organic compounds (VOCs).

Water for Industrial Use

• Industrial water requires specific quality standards.
• Boiler feed water must lack hardness, silica, and dissolved gases to prevent scaling/corrosion.
  • Pre-treatment includes softening, demineralization, and deaeration.
• Cooling water needs treatment to prevent scaling, corrosion, and biological fouling.
  • Chemical inhibitors and biocides are used.
• Manufacturing process water needs consistent quality.
  • Treatment depends on specific manufacturing needs.

Water Pollution

• Water pollution contaminates water bodies with harmful substances.
• Point source pollution has identifiable sources like factories/sewage plants.
• Non-point source pollution comes from diffuse sources like agricultural/urban runoff and atmospheric deposition.
• Pollutants include pathogens, nutrients, toxic chemicals, heavy metals, and sediments.
• Water pollution has negative impacts on health, ecosystems, and the environment.
• Eutrophication excessively enriches water, causing algal blooms and oxygen depletion.
• Acid rain happens when sulfur dioxide/nitrogen oxides react with water in the atmosphere to form acids.