Algae, Viruses, and Water Quality

Algae and Water Quality

• Algae contribute significantly to water quality, influencing taste, odor, and toxicity.
• Affect the oxygen balance in aquatic environments, potentially causing supersaturation or anaerobic conditions.
• Play a role in organic matter content and turbidity, impacting water filtration.

Viruses

• A virus consists of nucleic acid (DNA or RNA) and a protein coat (capsid), forming a nucleocapsid.
• Viruses can be naked or enveloped; examples include influenza and herpes viruses.
• Highly host-specific and may target specific tissues or cells within the host.
• Viruses do not reproduce outside living cells and typically lead to host cell death after replication.
• Bacteriophages utilize bacteria as hosts and are about 100 nm in size.

Pathogens in Water

• Waterborne pathogens can compromise human health, posing direct risks or being associated with aquatic insects.
• Microorganisms can survive in water for extended periods, impacting overall water quality.

Water Hardness

• Two types of hardness in water: carbonate (temporary) and non-carbonate (permanent).
• Primary contributors to hardness are calcium (Ca) and magnesium (Mg), with minor contributions from iron (Fe), manganese (Mn), strontium (Sr), and aluminum (Al).
• Carbonate hardness (easily removed by heating) relates to carbonates and bicarbonates, while non-carbonate hardness comes from other anions like sulfates and chlorides.
• Hardness affects soap efficiency and creates precipitates that can stain surfaces.

pH and Hardness Impact

• pH changes can lead to precipitate formation using bicarbonates, especially above pH 9.
• Hardness is measured in mg/L as CaCO3, categorized as soft (<50 mg/L), moderately hard (50-150 mg/L), hard (150-300 mg/L), and very hard (>300 mg/L).

Alkalinity

• Alkalinity measures water's capacity to neutralize acids, critical for maintaining pH stability.

Organic Matter in Wastewater

• Wastewater contains substantial organic matter, categorized into carbohydrates (30-50%), fats (10%), and proteins (40-60%).
• Various oxygen demand parameters measure organic matter, including ThOD, COD, BOD, and TOC.

Oxygen Demand Types

• ThOD: Theoretical oxygen demand based on known chemical equations; phosphorus and sulfur often overlooked in calculations.
• COD: Amount of oxygen needed to chemically oxidize organic matter in wastewater using potassium dichromate.

Nitrogen Compounds

• Common forms: organic nitrogen, ammonia (NH4+/NH3), nitrite (NO2-), nitrate (NO3-), and gaseous nitrogen.
• Ammoniacal nitrogen distribution varies with pH; NH4+ is favored at lower pH, while NH3 is favored at higher pH.

Nitrogen Measurements

• Total forms include total ammonia nitrogen (TAN), total inorganic nitrogen (TIN), total Kjeldahl nitrogen (TKN), and total nitrogen (TN).
• High nitrate levels in drinking water can lead to serious health issues like blue baby syndrome (methemoglobinemia).

Algal Effects on Water Supply

• Algae increase the demand for coagulants, clog filters, and promote bacteria aftergrowth.
• Aquatic weeds obstruct water supply screens, increase evapo-transpiration, and affect fish populations.

Sulfate in Water

• Present naturally in water and wastewater, essential for protein synthesis.
• Under anaerobic conditions, sulfate reduces to sulfide and can react with hydrogen to form hydrogen sulfide (H2S).

Oil and Grease in Water

• Interfere with natural re-aeration, are toxic to aquatic species, and pose fire hazards.
• Deteriorate water reuse potential, impart undesirable tastes and odors, and diminish recreational water quality.

Fluoride

• An inorganic anion associated with dental health benefits, though recent studies question its efficacy.
• WHO reports conflicting outcomes regarding cavity rates in children with and without fluoride exposure, raising skepticism over its supposed benefits.

This quiz explores the critical roles of algae, viruses, and pathogens in influencing water quality. It covers the effects of these microorganisms on oxygen balance, turbidity, and human health. Test your understanding of their characteristics and impacts in aquatic environments.