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Microbiology - Aquatic Microbiology

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    Study Guide Microbiology – Aquatic Microbiology 1. Sewage and Wastewater Treatment Every day, human activities produce large amounts of sewage and wastewater . Before this water can be released into rivers, lakes, or oceans — or reused — it must be treated carefully. Wastewater often contains: • Excess nitrogen and phosphorus • Heavy metals and chemical pollutants • Organic waste that can harm ecosystems • Pathogenic microorganisms that cause disease If released untreated, this mixture would overload natural waterways and threaten human health. 1.1 Why Treatment Is Necessary Sewage contains both chemical and biological waste . These wastes must be broken down before water is returned to the environment or reused. Treatment works by: • Managing microbial populations • Encouraging helpful microorganisms to digest organic matter • Removing harmful chemicals and disease - causing microbes Even water taken from ground sources must be treated before it is safe to drink. 1.2 Water Purification (Drinking Water Treatment) Water purification focuses on reducing microorganisms to safe levels and keeping them low. Step 1: Sedimentation Water is placed in a sedimentation tank , where heavy particles settle to the bottom.

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    Study Guide Chemicals such as alum are added to form clumps (flocs) that pull microorganisms down with them. Step 2: Filtration Water is filtered through sand to remove remaining microbes. • Slow sand filters use fine sand and take longer • Rapid sand filters use coarser sand and work faster Both remove about 99% of microorganisms . Step 3: Chlorination Most communities add chlorine to kill remaining microbes and prevent regrowth. • Chlorine gas or sodium hypochlorite (NaOCl) is used • A small chlorine residue is left to ensure safety 1.3 Sewage Treatment (Wastewater Treatment) Sewage treatment is more complex than drinking water treatment because sewage contains more organic matter and a wider variety of microorganisms. Primary Treatment • Large particles settle out in settling tanks • Solid material forms sludge • Sludge is burned, buried in landfills, or sent to digesters Secondary Treatment Secondary treatment reduces the microbial population and breaks down organic matter.

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    Study Guide Anaerobic Sludge Digestion • Occurs without oxygen • Microorganisms break down proteins, fats, and cellulose • Products include organic acids, alcohols, and methane gas • Methane can be burned as fuel • Remaining sludge is buried or incinerated Aerobic Secondary Treatment • Wastewater is aerated • Liquid passes through a trickling filter • Microbes grow on rocks or other materials and digest organic waste • The water leaving this stage is about 99% free of microorganisms Activated Sludge Process • Wastewater is vigorously aerated • Slime - forming bacteria trap other microbes • Clear liquid is removed for purification • Sludge is disposed of at sea or in landfills 1.4 Tertiary Treatment Tertiary treatment removes nutrients and chemical pollutants that can damage ecosystems. This stage includes: • Removal of phosphates and nitrates • Precipitation of ions using calcium or iron • Conversion of ammonia to nitrate ( nitrification ) • Activated charcoal adsorption to remove organic pollutants like PCBs

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    Study Guide 1.5 Home Septic Systems A septic system is a small - scale sewage treatment system used in homes. • Waste enters a septic tank • Anaerobic bacteria digest solids • Liquids flow into a septic field • Soil bacteria complete the breakdown Cesspools work similarly, but waste enters directly into surrounding soil.

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