Environmental Science: Water Pollution and Filtration

Water Pollution - Lecture 1

• Over 97.2% of the world's water is in the oceans, making it unusable for humans.
• Only 0.6% of the water is usable by humans (~8.4 km³).
• The hydrological cycle involves evaporation and precipitation (approximately 5.2 *10⁵ km³/year).
• Only 20% of precipitated water falls on continents.
• Evaporation is higher over oceans than precipitations.
• Precipitations are higher than evaporation over continents.
• Human activities affect the water cycle, leading to contamination and diseases in various areas.

Characteristics of Natural Water

• Water's chemical composition has a significant influence on water cycle and climate.
• Water has covalent bonds between hydrogen and oxygen atoms (~100 kcal/mol).
• Water has hydrogen bonds between hydrogen and oxygen atoms of different molecules (between 1 and 40 kcal/mol).
• Water cycle: evaporation, precipitation, runoff, etc.

Contaminated Water Characteristics - Lecture 1

• Water pollution occurs when the composition or physical condition of water is altered due to human activity.
• It implies water cannot be used with the same purpose as natural water.
• Contamination is measured in relation to the intended use of the water.
• Types of water pollution include concentrated sources (industrial effluents) and diffuse sources (agricultural runoff).

Physical Contaminants - Lecture 1.2.1

• Total matter: composed of suspended matter and substances removable by filtration.
• Suspended matter affects water color, sunlight penetration, and sediment deposition.
• Salinity, O2 solubility, and toxicity are quantifiable indicators of water quality.
• Other quantifiable data includes Matter in Suspension (MS), Solids in Suspension (SS), Dry Residue (DR) at 105 °C or Total Dissolved Solids (TDS), and Fixed Residue.
• Odor results from organic matter decomposition.
• Colour is caused by organic and inorganic pollutants (natural or anthropogenic).
• Urban wastewater (grey = recent, black = decomposed) and industrial wastewater colors vary based on contaminants.
• Temperature affects gas solubility and microbial activity.

Chemical Contaminants - Lecture 1.2.2

• Organic matter (OM): has natural (biodegradable) and urban/industrial (bio/non-biodegradable) sources.
• Detergents include surfactants and complementary chemicals (active ingredients, co-adjuvants and additives).
• Pesticides: formulations combining the active agent with other substances (inorganic/organic).
• Polychlorinated biphenyls (PCBs): stable at high temperatures, non-flammable, and persistent.
• Hydrocarbons (HC) include alkanes, alkenes, cycloalkanes, and aromatic compounds, with lower water-solubility and densities than water.
• They prevent light and oxygen from passing through the water's surface.

Parameters for Organic Contamination - Lecture 1.2.2

• Biochemical oxygen demand (BOD) is the amount of oxygen consumed by microorganisms during organic matter degradation under aerobic conditions.
• Chemical oxygen demand (COD) measures the amount of oxygen consumed by chemical reactions in organic matter degradation.
• Total Organic Carbon (TOC) and Total Oxygen Demand (TOD) are other relevant indicators.
• Understanding BOD5 (5-day BOD) and BOD20 (20-day BOD) is necessary for assessing the total organic contamination.
• Reference values for water quality: Highly pure waters = BOD5 < 3mgO2/L ; Contaminated waters = BOD5 >8 mgO2/L.

General Water Quality Indicators - Lecture 1.2.2

• Turbidity is an interference to light passing through water, caused by suspended matter, suspended/dissolved matter.
• It's measured in Nephelometric Turbidity Units (NTU's).
• Conductivity is the ability of water to conduct electricity, which depends on ion concentration.
• Water hardness is due to Ca², Mg² and other cations like Fe² and Mn².

Biological Contaminants - Lecture 1.2.3

• Biological contaminants include microorganisms (bacteria, algae, and viruses).
• These contaminants are present in wastewater, particularly in urban areas and can be a cause of eutrophication.
• Coliform bacteria indicate fecal contamination, while biotic indexes and toxicity assays measure the response of aquatic organisms to contaminants.

Contaminated Water Treatment - Lecture 2

• Wastewater sources: urban (conventional/separated sewers) and industrial sources.
• Home wastewaters are relatively consistent in flow & composition.
• Industrial wastewaters have varying compositions, including non-biodegradable chemical compounds or heavy metals.
• The type of wastewater impacts treatment choices.

Wastewater Treatment Plant (WWTP) - Lecture 2.3

• Wastewater treatment plants are crucial in treating wastewater to achieve specific levels of purity.
• The treatment stages include pretreatment, primary, secondary, and tertiary treatments.
• Pretreatment involves removing coarse particles like sediment, sand, grease, etc.
• Primary wastewater treatment focuses on removing sediment, which reduces BOD5 (Biochemical Oxygen Demand) by 30-40%.
• Secondary treatment employs biological or chemical processes to remove organic matter, thus reducing the BOD5 further.
• Tertiary treatment achieves the final purification of wastewater for reuse or discharge.

Sewage Sludge - Lecture 3

• Sewage sludge is produced during wastewater treatment processes.
• Sludge includes different types of organic and inorganic matters, in both solid and liquid form.
• Sludge is typically treated by stabilization (chemical, thermal, or biological), conditioning, dehydration (filtration, pressing, centrifuging, or drying beds), and disposal through landfill or incineration.
• Different treatment options exist for managing sewage sludge, and the best option depends on the specific characteristics of the sludge and the desired final application.

Air Pollution - Lecture 4

• The atmosphere layers are: Exosphere, Thermosphere, Mesosphere, Stratosphere and Troposphere.
• The homosphere is the lower layer and characterized by its homogenous composition.
• The heterosphere is found above, with a varying composition.
• Air pollutants include sulfur oxides (SOx), nitrogen oxides (NOx), carbon oxides (CO, CO₂), and hazardous air pollutants (HAPs).
• Atmospheric contamination impacts climate and ecosystems.

Management of Solid Contaminants in Gases - Lecture 5

• Solids and particles in gases present a varied composition and characteristics.
• Different physical and chemical processes are used to remove the particles in these solid contaminants.
• Mechanical separators (gravity chambers, cyclones, etc.) and electrostatic precipitators for solid removal are used.
• Scrubbers and filters are used for gases' cleaning and removal or trapping.

Management of Gaseous Pollutants - Lecture 6

• Absorption removes gaseous contaminants by dissolving them in a liquid (absorbent).
• Adsorption uses a solid adsorbent to retain contaminants.
• Incineration involves the combustion of the gaseous pollutants to achieve higher temperatures destroying the pollutants.
• Catalytic reduction chemically converts gaseous pollutants, using a catalyst, into less harmful products.

Industrial Waste - Lecture 9

• Industrial wastes are generated from different manufacturing and industrial processes.
• EU legislation and List of Wastes categorize various industrial wastes.
• Hazardous waste characteristics are defined by the EU for safe processing and treatment.

This quiz covers key concepts in environmental science related to water pollution and filtration methods. Topics include the properties of activated carbon, the operation of electro-filters, and the impact of agricultural practices on water quality. Test your knowledge on the interaction between groundwater composition, contamination, and purification techniques.